You've currently linked the two differentials together for steering. This is effective, but there is potential for more here: If you control each one seperately with one motor each, you can make this system work as a 4-speed gearbox too. It lets you add or substract the speed of each steering motor to the central one, giving you multiple drive speeds. You can also steer on only one side that way, rather than only spin on the spot. These two features combined also give you multiple steering arcs. The multiple speeds can be achieved by carefully selecting the gears connecting the steering motors to the differentials, so that if the main motor is 1:1, the steering motors are 3:1, giving you a selection of 3:1 (turn both steering motors in the same direction for linear motion), 3:2 (1:1 minus 3:1), 1:1 and 4:3 (1:1 plus 3:1). I would also suggest using wormgears, if you can. It's possible that the tank would be so heavy that the idle motors would end up getting turned by the active ones rather than the tracks, which could be damaging to the electronics. I've built this myself once, and it works beautifully. All this from simply disconnecting your steering!
Didn't notice this earlier, but the point of it is to have actual proper steering and not rely on on each motor being equal in power. This is an invalid solution for a heavy model. You can drive each track directly with proportional steering input if you've got a light model, but once you put 2 KG of bricks on top of that, it won't drive straight because motors won't be exactly equal and power output from the battery may not be exactly equal and so on. Also what you are proposing uses another motor input for it, so you're left with just one input on 4-input hubs while for tanks you'll need those two separate inputs for turret. That's why those steering mechanisms matter. Also it's now possible to do a fairly clean double gearbox steering like in T-34 with 16T/20T/24T clutch gear gearboxes for each side.
Actually I need to figure out an optimal layout that allows driving on a curve properly, so it' either needs some kind of reduction on the steering drive or a different layout than this. Right now steering drive rotates the differential frames so it has 2x the effect on the output and it should really have just fraction of what the main drive does.
@@SaperPl1 you might not really need to worry about gear reduction as the kinds of builds you'd put this in are big enough to have the gear reduction happen outside of the differential. You could also change the currently used differentials to the rc differentials (found in 42109, 42114 and 42124) because they connect with the 12 tooth gear. Another fix could be switching to powered up and using software to fix your problem.
@@K3b1bisLtu I tried doing that: i.imgur.com/jJeUvUcm.jpg i.imgur.com/1NgPgkXh.png I don't really want to put the reduction outside - I want to make it as small as possible as I want to make a kind of reference minimal tank chassis.
So THAT'S how Firestorm's drive system works! Firestorm was one of the most successful robots during the classic era of the TV show Robot Wars. It used the same drive system as this.
This is something used by tanks in general. Post WWII tanks, I think. In WWII a lot of tanks had just differential steering where they were breaking one side of the differential to turn and locking differential to go straight.
@@osmacar5331 I think you are confusing something here - this double differential setup is one of possible mechanisms for neutral steering. What was used during WW2 was single differential steering where you would break one sone of the tracks so whole power goes to the opposite side. I think such double differential mechanism is exactly the setup what most of the tanks had for neutral steering.
@@osmacar5331 You are still confusing it - I never said the ww2 tanks had this double diff. I said they had normal SINGLE differential steering == steering with breaks, Double differential == neutral steering.
beautiful. I just figured out a way to do this with the new differential. Just use the 36t between the two 8t gears that drives the new difff it works. Thank you so much for the inspiration!
The best what I could do was this: i.imgur.com/jJeUvUc.jpg I'm not sure about using 8t gears in all this, but I've tried doing something like this as well: i.imgur.com/1NgPgkX.png The general issue with all those setups is that by turning/subtraction through differential frames you are doubling the input and the effect in a lot of cases is that you are really close to stopping one track and the whole point is to have something like 2:1 ratio for driving on the curve instead of stopping one side. If that was the case, it'd be better to just figure out a way to break one side of the tracks and let the differential handle it, but this kind of mechanism also needs a differential lock when you're not breaking sides and making it flat gets complicated.
@@SaperPl1 So I built a couple one with your design the past week and they seem to work fine with reinforcements; my current version has two 5x7 frames supporting the two differential(which was the biggest issues, the tracks got too much friction on the suspension and drive it will start to skip. The second one is very interesting, also looks very simplistic
Thank you, this helped me design one of my best double differentials yet. Version 8 is only 9 studs wide, 7 ~ish (Some gears poke out) tall, and 8-7 deep depending which vertical level you measure.
I've had a lot of those stickers laying around and I had to mark the centre of the table. I need something that I can centre the camera with and I don't want to simply mark the table with a marker pen.
this was very helpful! I always wanted to build a lego tank like a real tank would have been built but I never figured the transmission out. So I just put one motor on each track and called it a day XD
@@mahj I really like the way you process videos, for me this part usually gets to a point of a chore. I just mostly like building MOCs, but I assume you like making videos as well and it really shows. I really liked your big desert landship and the forklift warehouse videos. Also the crane in micro container yard is really clever :)
Thank‘s for the Inspiration. But decided to use for my project, a 4 wheel drive. So I took your Idea, and I have expanded it so that I have all-wheel drive, which means that I have added 2 different speeds or 4 (with cornering) via gearstick. The gearstick is also motorised, so I can operate it by remote control.
I did and I plan to make a full tank chassis, but the suspension seems to be the hardest part to make it actually useful at this scale. I'll probably have to wait with it till I can make video for two models that are already there and waiting, because I'm running low on the parts and will have to scrap one of them.
@@aniolo5 Nie wiem jakim cudem nie zauważyłem tego wpisu wcześniej. Usuń swój adres email stąd. Zarejestruj się na forum lugpol i ewentualnie podrzuć na PW link do galerii jak jeszcze nie chcesz wszystkim pokazywać co robić.
Fantastic, I've been racking my brains out for something similar. You've solved it , well done. Hay I ordered some track and the kit came with little white rubber gripps that go in the track links . Amz.
I love the design, however I fail to see its usefulness. If you have two motors isn't it easier to power the two tracks via each one, and make the turns that way? Edit: okay, I red your comment on motor difference and "lottery" if it goes straight. That's a reasonable explanation, I'll take it.
Had the same thought here. I wonder if the “steering” motor could be made smaller/weaker than the main motor? Maybe with gears to compensate for the lack of torque.
@@Mike-oz4cv I tried multiple approaches to fit within this frame, but it always ended up in a way either the whole construction gets weak, or the ratio of steering input to drive input is big. This solution is still valid if you use analog input and slow down the speed on steering input, but for a big tank, lowering the motor output may make it not have the required torque. Ideally the default full speed of the steering motor would make it so that you have something like 50% of speed on one side and 150% on the other side or 66% vs 133%.
great thing for if you have two different motors. or don't have contorl+ or any other means of speed control! Done some things myself for my gremlin (not compact), but its fun to figure this type of differential on your own %) Tho now i prefer direct drive, control+ and 3rd part app is a blessing!
direct drive with two drives is cool and simple, but with bigger/heavier models when you reduce the power to the motors to slow down, its when it starts showing what such mechanisms are for. With Lego motors reducing speed also means reducing power, so it's not like exchanging speed for torque. systems for steering like this are made to handle driving straight and on a curve properly. I know the obvious solution is to have two perfectly matching motors with direct drive :)
@@SaperPl1 cant argue with that, better option is better motors altogether, but we have what we have %) ( i still think, OR WISH for some solution for power to control+ conversion or adapter)
Awesome, thanks for sharing. A few days ago, I was thinking about creating a tracked loader and thoughted I'd better start looking for those old subtractor designs I'd seen a few years ago. Then I opened CZcams and there was your video sitting there! I didn't even have to do a search for subtractors. Great compact design. It looks like I may need to do a little gear reduction as the one motor seems to be a bit too fast, but overall, I like it.
Totally awesome! The design is so compact. I think the steering motor is too fast. It supposed to be slower, but not too slow so it can pivot fast too. Maybe for steering motor need an electronic with more speed envelopes.
yeah, the steering motor is indeed too fast. This is just presentation of the principle. You can gear down this steering motor or try to figure out a better gearing setup altogether.
A little Info after i used this build for a tracked vehicle by myself. The idea is great but it is to weak if you use it under load. I later used a much stronger build of this mechanism but its allways the same result. To much torque on the gears resulting in the construction braking apart. Especially if you use it on a carped and if you try to turn the vehicle. If you build a stronger case around it the motor itself crushes the first axle. I found another use for it. You can use it in a Lego RC boat driven and steered by 2 propellers. in this case the load is much smaller and you can use the machanism as intended.
Well, I built this to explain the principle, but gearing here is the problem - the point is to have just slight difference in the speeds while this here is barely different than just breaking one side of the tracks. There should be some additional reduction for subtractor drive input.
@@SaperPl1 i build the mechanism you showed in this video a year ago. I liked it so much that i never disassembled it :) When i came to the idea to build a RC ship i instantly remembered it! Now it will find its way into my ship. For a ship with 2 propellers it is just perfect. Because the steering is extreme simple this way. And there should be no problem with to much torque etc. So still thank you and ofc showing the principle. It got me deeper in thinking about funktions in general. Building with lego technic and searching for solutions is my most loved part of the hobby.
basically, driveshaft car will rotate clockwise if the driver want car moving forward, but this steering mechanic working in other way, maybe it should be placed on front or change the shaft rotate. well, this video tell everything about dual differential steering in other way. (the other one used planetary gear for steering gear but this look like use a differential gear)
@@SaperPl1 ah, sorry about that, what I want to say is when the main axle rotate forward, the wheels will rotate in reverse, so if this configuration will be placed in vehicle (like tracked vehicle maybe) it must be placed in front or maybe make the main axle rotate backward or something like that, its just my opinion, maybe in practice will be different well, thanks about this video, it show if the dual differential steering can be improved. cause what I know is dual differential steering are using the planetary gear, not differential gear like this
@@naufalhaniffakhruddin3498 Well, yeah, but we don't have planetary gears in lego that have housing with separate input, just enclosed planetary gears for final drives/speed reduction-torque increase.
Hello, when in reverse/backward, the drive is also reverse (backward turn left in controller would make it turn right) or not? Because I cant really see it in video. I dont have the system yet right now so I can't check it but I do have my DIY tank RC with dual drive motor and it is programmed to behave like this regenerative dual differential steering and it is reversed when backward so I have yo make additionl switch input to reverse it again, and if I think of it it is true in this system that without reversing the input when we go reverse the steering would be the reverse.
Good question, I don't have this assembled right now, but since it's a subtractor, when you change the main drive input direction, the steering direction would also change meaning now the input that was subtracting before, would be adding to the direction. I think in the tanks that used this kind of mechanism before the electronic control era this was handled by this input drive being driven from the main shaft, so it was a sub-gearbox for steering feeding off from the drive shaft after the main speed gearbox, which effectively meant it kept the ratio of steering regardless of the main drive shaft speed, but also as you noticed, it maintained the proper steering direction, which I don't remember thinking about here. Good catch.
@@SaperPl1 I see. Its okay, as far as I know, at least on Leopard 2 engine they use hydrostatic motor to change the direction, same kind of motor used for forklift. It is turned by oil pump by changing the direction of pistons (?) of the hydrostatic motor it moved forward or bacward or you can say left and right. But you are correct on Tiger Tank it is being driven by main shaft and yes you are correct it would also be reversed. Thank you!
I tried to make something similar to this decades ago for another purpose but mine didn't work. Not sure how the torques work in this setup but it doesn't seem to have to problems I had. I wanted to make a bicycle with a fixed high gear ratio and use a low power motor to 'subtract' and produce a Constantly Variable Transmission. My goal was to have optimum pedal speed and let the torque applied decide the effective gear ratio. It didn't work.
Very nice, but I dont get why arent all the 20 tooth gears held the same way (using the grey brick with 4 pins) because that would make the whole thing sturdier, also not all of the four 20 tooth gears are needed, the one that is blue in the drive showcase is not needed. But other than that its really good design.
It is a leftovers build and I was missing some parts. Also not all gears/axles are located in spots where you can use this piece. But fair point - feel free to modify this design to make it sturdier.
IRL - you've got one gearbox/transmission + petrol engine for the forward movement and an electric motor for steering or some kind of separate connection. You can turn in place without moving back and forth. In Lego - for heavier models the differences between individual motors makes it so that it's harder to maintain straight line. This here isn't perfect as gear ratio aren't perfect for curve driving, but you can turn in place and drive straight without issues.
Do you gain anything with using this setup. Cool idea but since you already have to use 2 motors to power it why not just run one motor on one side and another on the other with just 2 gears to on each motor so the motors can run parallel like you have them. Very cool idea just seems inefficient to do something that can be done a lot simpler.
I've replied to those questions multiple times, go check out other comments. For one, this is how historically some of the tanks implemented neutral steering (the layout is flattened out, but the principle is the same), secondly Lego RC motors are not ideal and when you drop the speed, you drop the amount of power given to the motor and thus the torque drops. Also their characteristics on lowered speed are varying and some youtubers did tests of those. Because of that, if you have slightly bigger and heavier model, it makes sense to have something like that versus direct control. I'm not the first one to make a video on such steering mechanisms, check out Sariel's videos as well.
In real life conditions it's better to have one engine and one transmission/gearbox and be able to drive on a curve on the road because of the simplicity (both for steering ergonomics and reliability). In lego PF conditions you are losing torque when lowering the speed because the speed control on lego power functions is voltage based. For bigger/heavier models it means you don't really have that fine grain control over the steering with power output control of two motors. Also read other comments because there are other people asking same or similar questions :)
That is sbrick. But I already sold this one. CADA controller + battery works really well for me so far, having simple physical controller is nice while connecting phone to both gamepad and lego pf controller is cumbersome.
Depends on the size of the build and quality of the motors vs what the controller does when you are putting load on more than one motor. The issue is that when you've got a heavy build, and your motors work slightly differently at various power ranges, you won't drive straight. And also you may have differences when moving from a stand still. For small builds like CADA tiger/t34/panther, direct motor drive is okay, but I want to build a big technic model with technic shell on top at some point, but I need to figure out all the mechanics first.
@@SaperPl1 The advantages were also explained in the video you linked. Driving in a curve is a great plus, and being able to have a large primary and a seperate "turning" motor is also great. Being able to add a 2-speed transmission that can down-shift on load is also a great argument. I'd like to see this technique used on the rear wheels on a car where the "steering" motor both adds a difference (torque vectoring?) and turns the front wheels. This would be a challenge, ofcourse, because you don't want to engage the torque vectoring when standing still or driving backwards.
@@SaperPl1 but I need a proper explanation because the things I know about that system is they use gyro but how do they install that and how actually that works that's what I want u to demonstrate in ur video.
The service life of Lego differential is very poor because of the cross-like hole of the pinion. This is Ok if it does not work when moving straight. But this is not about this design.
I don't think using a limited slip differential is a good idea for a subtractor system. And Lego doesn't have a Torsen differential - the fully enclosed one is not a Torsen, nor limited slip - it just have a bit more resistance due to more gears is the mechanism.
Hey there, I'm a college engineering student and want to make this gearbox for my final project. Would you be able to find the part id numbers for all the parts in the gear box? If not that makes sense lol, this was a year ago! Thanks again in advance!
I think if you check out bricklink studio (stud.io) you will be able to find all those parts in studio easily with their corresponding numbers. Look for technic pins, gears, connectors, frames, axles, bushes, liftarms and differential frames. Studio is cool to look for parts, and maybe you'll make something cool yourself. Do some work for your project :P As for engineering student final (sic!) project, you should go for this one here: czcams.com/video/IhhNMtKU12E/video.html and show how it worked originally in Sherman because there's awesome documentation for it here: www.theshermantank.com/about/the-sherman-tank-powertrain-page/the-sherman-differential-normally-just-lumped-in-with-the-final-drives-but-not-here/
Please read other comments where I explain over and over the same thing. The Lego motors don't have precisely equal output, especially when you drop the power output to drive slower, so for bigger heavier models it starts to matter to have reliable mechanism for steering. Also apart from petrol-electric drive that Porsche pushed for with his prototype (which were breaking a lot because of that), most WWII tanks didn't had a direct drive like this and had some kind of steering mechanism.
Ik, i have a few techinc sets i've taken apart but i don't have the differential housing pieces, nor do i have those fram pieces. Edit: i don't have a lot of gears as well
@@blenheimmayhem That's because Lego is segmenting the market making it so that lower end/cheaper sets don't have a lot of mechanical parts in them. It's similar to how you won't usually find the best APU (CPU with integrated GPU) in a low end laptop that doesn't have dedicated GPU and you need to get a higher tiered model to have it where it stops making sense.
Super Awesome this project. Where I can find 3D models for all the tech Lego parts used for this project? Can you help me in this regard? I would like to reproduce this for my son. Thanks in advance and best regards !
Thanks, but for some simpler projects like this, I don't make instructions on rebrickable, but I tend to make the video in a way that you can initially see all parts required for such small builds like this. For 3D models like you said, everything required for this construction should be already there in bricklink studio, you just need to pick correct parts from the library.
Because of the complexity - steering a tank with two gearboxes and two engines means doubling the chances of failure and making it harder for a single driver to handle, at least early in WWII. Now when we have all different automatic transmissions, the modern tanks could do that, but you've got to remember that on the inside tanks of WWII had actually transmissions coming straight from the trucks, at least they were designed the same way, and with an increased weight and off-road drive, this already got complicated to drive. There were actually tanks that had to stop to change gear on the transmission, which is obviously weird, but there were such failures. If you were to have two separate transmissions, you have two clutches etc. I think T34 actually had this kind of steering system as Sariel recently shown though. Also, I'm not sure if I'm right here, but I think that additionally this type of dual differential steering may have better torque characteristics than having two gearboxes in which you obviously exchange torque for higher speed, so when turning the torque is uneven, but I think it may work a bit differently with that subtractor configuration.
I don't think so, unless you want to make this thing bigger. You could use the red 28 tooth gear from new differential, but that's not really good option as its costly.
The whole point of this kind mechanism is so you can decide of how tight turn you want to make with the subtracted input speed. Or I don't get why you mean. This is still not perfect though as I should have significant reduction on that subtracting/steering drive.
@@SaperPl1 Also, ich denke, dass es vielleicht 3 Arten von der Änderung der Richtung, die das Fahrzeug irgendwohin geht oder fährt, gibt. Beziehungsweise: 1)Links↓ Rechts↑; 2)Links(bewegungslos) Rechts↑; 3)Links↑ Rechts↑ (Die Geschwindigkeit von Rechts ist größer als Links) Also, ich möchte fragen, ob deine Tank die 3) Situation vollenden kann
@@Mora_is_not_enough Like I said, that's the point of this mechanism. one of the motor defines the base speed of the tracks going forward and the other defines the speed difference between them. The issue here is that the subtractor in this configuration is rotating the differential frames which makes the subtraction speed too high.
Sorry, I don't have the list, but check out the first few seconds of the video to see what's there. the grey piece is a 28 tooth gear that's kind of new.
This is only one type of tracked steering. What you are talking about is still something that is valid, but with Lego it gets complicated to do because making breaks for each side of track gets complicated and also you should have differential lock when you're driving straight with that kind of steering. I've got a video on the steering with breaking, so check that out :)
you don't have perfect control over lego RC motors - when you lower the speed, you also have lower torque and those values vary from motor to motor. For bigger models it starts making sense. Also check out other comments as I keep repeating myself here.
Or can you give me the link to where you can buy these two? Compact flat subtractor / Double Differential - tank steering build czcams.com/video/3_Xxrw2BSf0/video.html Small steering hub revisited and a 6x6 prototype chassis czcams.com/video/DNqy_S8GR7M/video.html
The parts in the compact flat subtractor are all original Lego Technic. The small steering hub is a 3D printed part and there is a thingiverse link in the video description.
Not really. The quality of the motors matters, how controller outputs the power matters. Those are not precise linear motors that guarantee that you will have same amount of steps/RPMs on each motor, so it's a lottery on whether your motors will let you drive in a straight line or not.
@@SaperPl1Firstly… they’re definitely precise enough for a LEGO TOY😂. Secondly. HUNDREDS OF MILLIONS of machines around the world use non precise motor drives for tanks, skid steers, compact track loaders, zero turn lawn mowers, sod rollers, tractors, snow blowers, snow cats and even R/C versions of ALL the aforementioned machines. It’s very easy to compensate for slight differences with the controls or even a speed sensing system that has the ability to monitor ground speed on both sides. Both are far less complex and exponentially more efficient and reliable than this.
@@brandoncrimmins6296 direct input gives direct control, this is true. This system will turn smoother though. Much less jerky. You should look up why differentials are important, and why they could but utilized to improve tracked vehicles.
@@brandoncrimmins6296why you mad about a guy building a lego tank. Also most of us clicked on this because we like the complexity. wouldn’t be cool if it were just 2 motors and 2 gears
Well, I keep explaining the same thing in those comments - the issue is that you can't be sure that both motors connected directly to the tracks will have same output either because of the motors themselves or how the power is coming from the controller. That's for one. For two, this is one of steering types used in tanks, this one is in more modern tanks, and it allows driving on a curve. If you wanted to make something like separate drives for each track in real tank, you'd have to have separate gearboxes for each track or a petrol-electric kind of drive that Porsche pushed for with his tank designs.
@@SaperPl1 look we have cars that have 4 separate motors for each wheel we have cars with double petrol engines running front and rear axles separately how do you want to drive on curve when your motors works 01 on or off there is something called correction every rc model does that there are even automatic ones using gyroscope this design has no future its complicated mechanical design that have flaws of loosing power on friction and having higher chances of getting damaged german tanks in ww2 were able to rotate in place and drive on curve having only one motor and doing it all on mechanical system what what it lead to? all of them were breaking there is no reason to chase after gears and transmissions when for past decade everyone was trying to get rid of them because they are weak points
@@OGNISTYSZKQAJDII Go look for videos comparing output/RPMs between motors from various vendors. BrickHouse had quite a few of those recently. Also check out videos from Sariel showing off those types of tank steering. The motors in lego are not RC-grade quality motors people use in RC models, but just stupid DC motors and this doesn't compare. It's not something that I've made up just to be cool, those steering mechanisms are existing ones being used. Of course now when we have quality electric motors like those in tesla cars, this is different, but it wasn't always like that. As for german steering mechanisms breaking - actually, at least for the panthers, it's not the steering that was breaking, but the final drives which is a bit different piece - it's the reduction gearing that's coming out of the transmission/steering to reduce the speed and increase torque. Also the petrol-electric drive where you have electric motors for each track and engine(s) generating power was breaking a lot in those Porsche tanks (tiger prototype, Elefant and Maus) Finally I don't think it's the most used steering mechanism in WWII, the most popular one is probably simple differential/break steering where you break one of the side of differential so all output goes to the other side and the differential gets locked when driving straight. This is good enough for off-road and going straight, but when driving on curved roads this consumes the break pads a lot or is a general pain to drive this way. This is something that's both for making it work more like the tanks do it and because lego motors are not perfect. Reference for this kind of steering: i.ytimg.com/vi/_z3n6VOk-Ls/maxresdefault.jpg Sariel's videos: czcams.com/video/f5_OQooBxdY/video.html czcams.com/video/h7GAZl6Il6k/video.html
@@SaperPl1 seriously, this is impressive. Please try to ignore the commenters trying to tear down your idea "because a real life tank doesn't do that / $50k cars have motors that can do this better!" Do you people even hear yourselves?
That's one of the was to control steering on the tank. It's not useless. It starts to make sense for bigger and heavier models if you want to have some precision in steering. Lego motors as well as their clones are pretty dumb motors that do not guarantee the same RPMs and torque, so you'll have different speed on each track. It becomes more visible when you run them at lower power output as well, so driving in a straight line slowly will be impossible. Of course that's a toy and you can't just ignore those problems, but there are also models that people do to make them work more realistic.
You've currently linked the two differentials together for steering. This is effective, but there is potential for more here: If you control each one seperately with one motor each, you can make this system work as a 4-speed gearbox too. It lets you add or substract the speed of each steering motor to the central one, giving you multiple drive speeds. You can also steer on only one side that way, rather than only spin on the spot. These two features combined also give you multiple steering arcs.
The multiple speeds can be achieved by carefully selecting the gears connecting the steering motors to the differentials, so that if the main motor is 1:1, the steering motors are 3:1, giving you a selection of 3:1 (turn both steering motors in the same direction for linear motion), 3:2 (1:1 minus 3:1), 1:1 and 4:3 (1:1 plus 3:1).
I would also suggest using wormgears, if you can. It's possible that the tank would be so heavy that the idle motors would end up getting turned by the active ones rather than the tracks, which could be damaging to the electronics.
I've built this myself once, and it works beautifully. All this from simply disconnecting your steering!
Didn't notice this earlier, but the point of it is to have actual proper steering and not rely on on each motor being equal in power. This is an invalid solution for a heavy model. You can drive each track directly with proportional steering input if you've got a light model, but once you put 2 KG of bricks on top of that, it won't drive straight because motors won't be exactly equal and power output from the battery may not be exactly equal and so on. Also what you are proposing uses another motor input for it, so you're left with just one input on 4-input hubs while for tanks you'll need those two separate inputs for turret.
That's why those steering mechanisms matter. Also it's now possible to do a fairly clean double gearbox steering like in T-34 with 16T/20T/24T clutch gear gearboxes for each side.
I think this is also known as a double differential, you might what to add that in the title so people can find it more easily. This is really great.
Actually I need to figure out an optimal layout that allows driving on a curve properly, so it' either needs some kind of reduction on the steering drive or a different layout than this. Right now steering drive rotates the differential frames so it has 2x the effect on the output and it should really have just fraction of what the main drive does.
@@SaperPl1 you might not really need to worry about gear reduction as the kinds of builds you'd put this in are big enough to have the gear reduction happen outside of the differential.
You could also change the currently used differentials to the rc differentials (found in 42109, 42114 and 42124) because they connect with the 12 tooth gear.
Another fix could be switching to powered up and using software to fix your problem.
@@K3b1bisLtu I tried doing that: i.imgur.com/jJeUvUcm.jpg i.imgur.com/1NgPgkXh.png
I don't really want to put the reduction outside - I want to make it as small as possible as I want to make a kind of reference minimal tank chassis.
@@SaperPl1 well then, good luck
@@SaperPl1 Are there any substitutes for the 28 tooth gear?
So THAT'S how Firestorm's drive system works!
Firestorm was one of the most successful robots during the classic era of the TV show Robot Wars. It used the same drive system as this.
This is something used by tanks in general. Post WWII tanks, I think. In WWII a lot of tanks had just differential steering where they were breaking one side of the differential to turn and locking differential to go straight.
@@SaperPl1 it was during WW2 that double diff was used post war p much al ltanks used it as neutral steering was very advantageous
@@osmacar5331 I think you are confusing something here - this double differential setup is one of possible mechanisms for neutral steering. What was used during WW2 was single differential steering where you would break one sone of the tracks so whole power goes to the opposite side. I think such double differential mechanism is exactly the setup what most of the tanks had for neutral steering.
@@osmacar5331 You are still confusing it - I never said the ww2 tanks had this double diff. I said they had normal SINGLE differential steering == steering with breaks, Double differential == neutral steering.
beautiful. I just figured out a way to do this with the new differential. Just use the 36t between the two 8t gears that drives the new difff it works. Thank you so much for the inspiration!
The best what I could do was this: i.imgur.com/jJeUvUc.jpg
I'm not sure about using 8t gears in all this, but I've tried doing something like this as well:
i.imgur.com/1NgPgkX.png
The general issue with all those setups is that by turning/subtraction through differential frames you are doubling the input and the effect in a lot of cases is that you are really close to stopping one track and the whole point is to have something like 2:1 ratio for driving on the curve instead of stopping one side. If that was the case, it'd be better to just figure out a way to break one side of the tracks and let the differential handle it, but this kind of mechanism also needs a differential lock when you're not breaking sides and making it flat gets complicated.
@@SaperPl1 So I built a couple one with your design the past week and they seem to work fine with reinforcements; my current version has two 5x7 frames supporting the two differential(which was the biggest issues, the tracks got too much friction on the suspension and drive it will start to skip. The second one is very interesting, also looks very simplistic
Thank you, this helped me design one of my best double differentials yet. Version 8 is only 9 studs wide, 7 ~ish (Some gears poke out) tall, and 8-7 deep depending which vertical level you measure.
War thunder profile I like it
I enjoyed the mechanical/electrical symbol for ground on the table. Had a chuckle.
I've had a lot of those stickers laying around and I had to mark the centre of the table. I need something that I can centre the camera with and I don't want to simply mark the table with a marker pen.
this was very helpful! I always wanted to build a lego tank like a real tank would have been built but I never figured the transmission out. So I just put one motor on each track and called it a day XD
Yep. Me too. Two motors made sense to me. Seems like this model also used a two motors
Engineering is so flippin' awesome! Great showcase of what I was trying to wrap my brain around.
Very elegant solution.
Thanks. Btw I was blown away by your MOCs, couldn't believe someone with so many subs subscribed to my channel. So thanks again :D
@@SaperPl1 The numbers are skewed- I just got an early start, that helps. Really glad to hear you like what I do!
@@mahj I really like the way you process videos, for me this part usually gets to a point of a chore. I just mostly like building MOCs, but I assume you like making videos as well and it really shows. I really liked your big desert landship and the forklift warehouse videos. Also the crane in micro container yard is really clever :)
How have i never found this channel before, fantastic content!
Thank‘s for the Inspiration. But decided to use for my project, a 4 wheel drive.
So I took your Idea, and I have expanded it so that I have all-wheel drive, which means that I have added 2 different speeds or 4 (with cornering) via gearstick. The gearstick is also motorised, so I can operate it by remote control.
Thanks for putting the ground marker there. Otherwise it would seem it drives in the air ;P
Oh how long we've been waiting for the 28 tooth gear
Wait is that legal?
someone needs to hire this man.
Looks really nice. Would be interesting to try this in a small tank MOC. Have you experimented with suspension for a tank of this scale?
I did and I plan to make a full tank chassis, but the suspension seems to be the hardest part to make it actually useful at this scale. I'll probably have to wait with it till I can make video for two models that are already there and waiting, because I'm running low on the parts and will have to scrap one of them.
@@SaperPl1 maybe fuck up some axels as torsion bars? Should work at that scale…
@@aniolo5 Nie wiem jakim cudem nie zauważyłem tego wpisu wcześniej. Usuń swój adres email stąd. Zarejestruj się na forum lugpol i ewentualnie podrzuć na PW link do galerii jak jeszcze nie chcesz wszystkim pokazywać co robić.
@@tobiastho9639 will have to see when I get back to that project. I don't really like designing the features that damage parts.
@@SaperPl1 also my problem. i dont like that idea. also i am not a fan of rubber bands.
Fantastic, I've been racking my brains out for something similar. You've solved it , well done. Hay I ordered some track and the kit came with little white rubber gripps that go in the track links . Amz.
So beautiful.
I love the design, however I fail to see its usefulness. If you have two motors isn't it easier to power the two tracks via each one, and make the turns that way?
Edit: okay, I red your comment on motor difference and "lottery" if it goes straight. That's a reasonable explanation, I'll take it.
meme :D
Had the same thought here. I wonder if the “steering” motor could be made smaller/weaker than the main motor? Maybe with gears to compensate for the lack of torque.
@@Mike-oz4cv I tried multiple approaches to fit within this frame, but it always ended up in a way either the whole construction gets weak, or the ratio of steering input to drive input is big. This solution is still valid if you use analog input and slow down the speed on steering input, but for a big tank, lowering the motor output may make it not have the required torque. Ideally the default full speed of the steering motor would make it so that you have something like 50% of speed on one side and 150% on the other side or 66% vs 133%.
great thing for if you have two different motors. or don't have contorl+ or any other means of speed control!
Done some things myself for my gremlin (not compact), but its fun to figure this type of differential on your own %)
Tho now i prefer direct drive, control+ and 3rd part app is a blessing!
direct drive with two drives is cool and simple, but with bigger/heavier models when you reduce the power to the motors to slow down, its when it starts showing what such mechanisms are for. With Lego motors reducing speed also means reducing power, so it's not like exchanging speed for torque. systems for steering like this are made to handle driving straight and on a curve properly.
I know the obvious solution is to have two perfectly matching motors with direct drive :)
@@SaperPl1 cant argue with that, better option is better motors altogether, but we have what we have %) ( i still think, OR WISH for some solution for power to control+ conversion or adapter)
Классное решение :)
Awesome, thanks for sharing. A few days ago, I was thinking about creating a tracked loader and thoughted I'd better start looking for those old subtractor designs I'd seen a few years ago. Then I opened CZcams and there was your video sitting there! I didn't even have to do a search for subtractors. Great compact design. It looks like I may need to do a little gear reduction as the one motor seems to be a bit too fast, but overall, I like it.
Totally awesome! The design is so compact. I think the steering motor is too fast. It supposed to be slower, but not too slow so it can pivot fast too. Maybe for steering motor need an electronic with more speed envelopes.
yeah, the steering motor is indeed too fast. This is just presentation of the principle. You can gear down this steering motor or try to figure out a better gearing setup altogether.
A little Info after i used this build for a tracked vehicle by myself. The idea is great but it is to weak if you use it under load. I later used a much stronger build of this mechanism but its allways the same result. To much torque on the gears resulting in the construction braking apart. Especially if you use it on a carped and if you try to turn the vehicle. If you build a stronger case around it the motor itself crushes the first axle.
I found another use for it. You can use it in a Lego RC boat driven and steered by 2 propellers. in this case the load is much smaller and you can use the machanism as intended.
Well, I built this to explain the principle, but gearing here is the problem - the point is to have just slight difference in the speeds while this here is barely different than just breaking one side of the tracks. There should be some additional reduction for subtractor drive input.
@@SaperPl1 i build the mechanism you showed in this video a year ago. I liked it so much that i never disassembled it :)
When i came to the idea to build a RC ship i instantly remembered it! Now it will find its way into my ship. For a ship with 2 propellers it is just perfect. Because the steering is extreme simple this way. And there should be no problem with to much torque etc.
So still thank you and ofc showing the principle. It got me deeper in thinking about funktions in general. Building with lego technic and searching for solutions is my most loved part of the hobby.
This looks amazing, never would have thought of that. I have almost every part, except the grey 28 tooth gear, should probably get a few of those!
Great work, I really need to make one of these but I don’t have that weird gray gear
Brilliant design!
basically, driveshaft car will rotate clockwise if the driver want car moving forward, but this steering mechanic working in other way, maybe it should be placed on front or change the shaft rotate. well, this video tell everything about dual differential steering in other way. (the other one used planetary gear for steering gear but this look like use a differential gear)
I'm a bit lost in what you want to say. Iirc you are refering to the semi truck with drive forwarded through the trailer turntable connection?
@@SaperPl1 ah, sorry about that, what I want to say is when the main axle rotate forward, the wheels will rotate in reverse, so if this configuration will be placed in vehicle (like tracked vehicle maybe) it must be placed in front or maybe make the main axle rotate backward or something like that, its just my opinion, maybe in practice will be different
well, thanks about this video, it show if the dual differential steering can be improved. cause what I know is dual differential steering are using the planetary gear, not differential gear like this
@@naufalhaniffakhruddin3498 Well, yeah, but we don't have planetary gears in lego that have housing with separate input, just enclosed planetary gears for final drives/speed reduction-torque increase.
I wonder how much backlash the output furthest from the steering driveshaft faces
Це Більш механічний спосіб рішення , а простіший встановити на кожну сторону свій мотор і запрограмувати відповідно .
Щей дуже шумит
Cool design
Very cool design!
Hello, when in reverse/backward, the drive is also reverse (backward turn left in controller would make it turn right) or not? Because I cant really see it in video.
I dont have the system yet right now so I can't check it but I do have my DIY tank RC with dual drive motor and it is programmed to behave like this regenerative dual differential steering and it is reversed when backward so I have yo make additionl switch input to reverse it again, and if I think of it it is true in this system that without reversing the input when we go reverse the steering would be the reverse.
Good question, I don't have this assembled right now, but since it's a subtractor, when you change the main drive input direction, the steering direction would also change meaning now the input that was subtracting before, would be adding to the direction. I think in the tanks that used this kind of mechanism before the electronic control era this was handled by this input drive being driven from the main shaft, so it was a sub-gearbox for steering feeding off from the drive shaft after the main speed gearbox, which effectively meant it kept the ratio of steering regardless of the main drive shaft speed, but also as you noticed, it maintained the proper steering direction, which I don't remember thinking about here. Good catch.
@@SaperPl1 I see. Its okay, as far as I know, at least on Leopard 2 engine they use hydrostatic motor to change the direction, same kind of motor used for forklift. It is turned by oil pump by changing the direction of pistons (?) of the hydrostatic motor it moved forward or bacward or you can say left and right.
But you are correct on Tiger Tank it is being driven by main shaft and yes you are correct it would also be reversed. Thank you!
I tried to make something similar to this decades ago for another purpose but mine didn't work. Not sure how the torques work in this setup but it doesn't seem to have to problems I had.
I wanted to make a bicycle with a fixed high gear ratio and use a low power motor to 'subtract' and produce a Constantly Variable Transmission. My goal was to have optimum pedal speed and let the torque applied decide the effective gear ratio.
It didn't work.
It does have some problems, I'm still tinkering with this idea
hell yeah yehaw brother.
😻
What type of remote sensor is that? Is it better than the one lego produced pre-2019
that's sbrick
Very nice, but I dont get why arent all the 20 tooth gears held the same way (using the grey brick with 4 pins) because that would make the whole thing sturdier, also not all of the four 20 tooth gears are needed, the one that is blue in the drive showcase is not needed. But other than that its really good design.
It is a leftovers build and I was missing some parts. Also not all gears/axles are located in spots where you can use this piece. But fair point - feel free to modify this design to make it sturdier.
perhaps this can be done through one motor. but there will be a lot of moving parts ... A LOT
There is a guy doing such shenanigans, but it doesn't make much sense. Like spend 10x more on gears so you can save on single motor :P
I have a question I am trying to motorize a Lego tank that I currently have do you think you could send a link for all of the parts
It's probably the smallest Lego subtractor ever
i build it and it works very well. thank you!
That's way cool
I love it
Lets say you wanted to pull it with a handle left or right. How would you do that?
I don't know what you mean. What's handle left or right?
Can you drive the other side of the differential? Because to me it looks to be possible if the motors spin the same way.
Can you explain in more detail what you mean by the other side of the differential?
@@SaperPl1 Like is it worth it to have three motors or is it just wasting battery?
So what's the advantage of this, versus just making each motor control a different side of the track?
IRL - you've got one gearbox/transmission + petrol engine for the forward movement and an electric motor for steering or some kind of separate connection. You can turn in place without moving back and forth.
In Lego - for heavier models the differences between individual motors makes it so that it's harder to maintain straight line. This here isn't perfect as gear ratio aren't perfect for curve driving, but you can turn in place and drive straight without issues.
охуенный механизм. теперь только так будем делать)
Yay music,
Try to drive on some carpet😃 anyway, really good video, i understand that principle
Do you gain anything with using this setup. Cool idea but since you already have to use 2 motors to power it why not just run one motor on one side and another on the other with just 2 gears to on each motor so the motors can run parallel like you have them. Very cool idea just seems inefficient to do something that can be done a lot simpler.
I've replied to those questions multiple times, go check out other comments. For one, this is how historically some of the tanks implemented neutral steering (the layout is flattened out, but the principle is the same), secondly Lego RC motors are not ideal and when you drop the speed, you drop the amount of power given to the motor and thus the torque drops. Also their characteristics on lowered speed are varying and some youtubers did tests of those. Because of that, if you have slightly bigger and heavier model, it makes sense to have something like that versus direct control. I'm not the first one to make a video on such steering mechanisms, check out Sariel's videos as well.
Is this better than just having the two motors direct drive each track? I understand the demo of the mechanism but is there an advantage to it?
In real life conditions it's better to have one engine and one transmission/gearbox and be able to drive on a curve on the road because of the simplicity (both for steering ergonomics and reliability). In lego PF conditions you are losing torque when lowering the speed because the speed control on lego power functions is voltage based. For bigger/heavier models it means you don't really have that fine grain control over the steering with power output control of two motors. Also read other comments because there are other people asking same or similar questions :)
It's brilliant! 🤩
What is the manufacturer / model of these white RF receiver?
That is sbrick. But I already sold this one. CADA controller + battery works really well for me so far, having simple physical controller is nice while connecting phone to both gamepad and lego pf controller is cumbersome.
This is pretty neat, but i wonder if just using one motor per side is more efficient
Depends on the size of the build and quality of the motors vs what the controller does when you are putting load on more than one motor. The issue is that when you've got a heavy build, and your motors work slightly differently at various power ranges, you won't drive straight. And also you may have differences when moving from a stand still. For small builds like CADA tiger/t34/panther, direct motor drive is okay, but I want to build a big technic model with technic shell on top at some point, but I need to figure out all the mechanics first.
@@SaperPl1 The advantages were also explained in the video you linked. Driving in a curve is a great plus, and being able to have a large primary and a seperate "turning" motor is also great. Being able to add a 2-speed transmission that can down-shift on load is also a great argument.
I'd like to see this technique used on the rear wheels on a car where the "steering" motor both adds a difference (torque vectoring?) and turns the front wheels. This would be a challenge, ofcourse, because you don't want to engage the torque vectoring when standing still or driving backwards.
Please make a video on stability of barrel 🙏
stability of barrel? you mean gun stabiliser? I don't think it's an easy thing to do with just mechanics at the scale I'm making models.
@@SaperPl1 but I need a proper explanation because the things I know about that system is they use gyro but how do they install that and how actually that works that's what I want u to demonstrate in ur video.
I wish there were legos like this when I was a kid.
Lol, that's exactly why I'm back into legos xD
If you were born after 1973 there were
The service life of Lego differential is very poor because of the cross-like hole of the pinion. This is Ok if it does not work when moving straight. But this is not about this design.
Subbed, hope your channel grows!
Same
Thanks!
@@Phoenix-Saika Thanks :D
Ahoy! Would it be suitable to substitute the open style differential for torsen style?
I don't think using a limited slip differential is a good idea for a subtractor system. And Lego doesn't have a Torsen differential - the fully enclosed one is not a Torsen, nor limited slip - it just have a bit more resistance due to more gears is the mechanism.
Just a thought. Messing with custom diff builds, train of thought got abit wild
In any case, 2 engines are used, instead of one as in real life
Hey there, I'm a college engineering student and want to make this gearbox for my final project. Would you be able to find the part id numbers for all the parts in the gear box? If not that makes sense lol, this was a year ago! Thanks again in advance!
I think if you check out bricklink studio (stud.io) you will be able to find all those parts in studio easily with their corresponding numbers. Look for technic pins, gears, connectors, frames, axles, bushes, liftarms and differential frames. Studio is cool to look for parts, and maybe you'll make something cool yourself. Do some work for your project :P
As for engineering student final (sic!) project, you should go for this one here: czcams.com/video/IhhNMtKU12E/video.html and show how it worked originally in Sherman because there's awesome documentation for it here: www.theshermantank.com/about/the-sherman-tank-powertrain-page/the-sherman-differential-normally-just-lumped-in-with-the-final-drives-but-not-here/
@@SaperPl1 thank you so much! I’m so excited to make this and you’re a big help!
Oops I'm missing a gear ! Please how many teath has that centre Gray gear?
That's the 28 tooth gear - it's the one that you have on the differential but full instead of half. It's kind of new piece
You have a list or a website where I can find the parts numbers?
Very effective design, cool, tho i don't have the 28 tooth gear lol
Edit: Yea i could replace It with a small turntable, Imma try that...
Wow, I didn't think about that. That's an interesting idea
VERY GOOD
👍
sick
ok very cool but why didnt you just put 1 motor for each track instead of making a complicated transmission
Please read other comments where I explain over and over the same thing. The Lego motors don't have precisely equal output, especially when you drop the power output to drive slower, so for bigger heavier models it starts to matter to have reliable mechanism for steering. Also apart from petrol-electric drive that Porsche pushed for with his prototype (which were breaking a lot because of that), most WWII tanks didn't had a direct drive like this and had some kind of steering mechanism.
I wish i had the parts to do this
Yeah, making custom things in lego is either having a lot of sets or buying separate pieces. Either way its not a cheap hobby.
Ik, i have a few techinc sets i've taken apart but i don't have the differential housing pieces, nor do i have those fram pieces. Edit: i don't have a lot of gears as well
@@blenheimmayhem That's because Lego is segmenting the market making it so that lower end/cheaper sets don't have a lot of mechanical parts in them. It's similar to how you won't usually find the best APU (CPU with integrated GPU) in a low end laptop that doesn't have dedicated GPU and you need to get a higher tiered model to have it where it stops making sense.
Super Awesome this project. Where I can find 3D models for all the tech Lego parts used for this project? Can you help me in this regard? I would like to reproduce this for my son. Thanks in advance and best regards !
Thanks, but for some simpler projects like this, I don't make instructions on rebrickable, but I tend to make the video in a way that you can initially see all parts required for such small builds like this. For 3D models like you said, everything required for this construction should be already there in bricklink studio, you just need to pick correct parts from the library.
So why is such a scheme better than the usual one, when each side has its own engine with a gearbox?
Because of the complexity - steering a tank with two gearboxes and two engines means doubling the chances of failure and making it harder for a single driver to handle, at least early in WWII. Now when we have all different automatic transmissions, the modern tanks could do that, but you've got to remember that on the inside tanks of WWII had actually transmissions coming straight from the trucks, at least they were designed the same way, and with an increased weight and off-road drive, this already got complicated to drive. There were actually tanks that had to stop to change gear on the transmission, which is obviously weird, but there were such failures. If you were to have two separate transmissions, you have two clutches etc. I think T34 actually had this kind of steering system as Sariel recently shown though.
Also, I'm not sure if I'm right here, but I think that additionally this type of dual differential steering may have better torque characteristics than having two gearboxes in which you obviously exchange torque for higher speed, so when turning the torque is uneven, but I think it may work a bit differently with that subtractor configuration.
@@SaperPl1 Got it. Thank you.
pls try variable speed motors ;-)
you mean to have two motors directly connected to the tracks and controling steering with the motor power value?
Are there any substitutes for the 28 tooth gear?
I don't think so, unless you want to make this thing bigger. You could use the red 28 tooth gear from new differential, but that's not really good option as its costly.
Well, I think this Tank cannot turn a corner when this Tank is going forward(except stop).
The whole point of this kind mechanism is so you can decide of how tight turn you want to make with the subtracted input speed. Or I don't get why you mean. This is still not perfect though as I should have significant reduction on that subtracting/steering drive.
@@SaperPl1 I mean the kind of turn where the speed of the tracks on both sides are different.
@@SaperPl1 Also, ich denke, dass es vielleicht 3 Arten von der Änderung der Richtung, die das Fahrzeug irgendwohin geht oder fährt, gibt.
Beziehungsweise:
1)Links↓ Rechts↑;
2)Links(bewegungslos) Rechts↑;
3)Links↑ Rechts↑
(Die Geschwindigkeit von Rechts ist größer als Links)
Also, ich möchte fragen, ob deine Tank die 3) Situation vollenden kann
@@Mora_is_not_enough Like I said, that's the point of this mechanism. one of the motor defines the base speed of the tracks going forward and the other defines the speed difference between them. The issue here is that the subtractor in this configuration is rotating the differential frames which makes the subtraction speed too high.
@@SaperPl1 Thanks for the explanation
Where can I find a list of the necessary items? :D
Sorry, I don't have the list, but check out the first few seconds of the video to see what's there.
the grey piece is a 28 tooth gear that's kind of new.
Is it possible to connect a gearbox to this design?
Yes, you connect it to the drive input in the middle.
@@SaperPl1 Okay, thank you.
This is realy smal but my tank needs a stronger system my tank weights more than 5kg! And i need 6XL motors too have good power!
Well, at your scale you can figure something out that doesn't need to be this small.
@@SaperPl1 yea thats the other point
is it 1:1?
1:1 of what? gear ratio? No - because it's 20:24 on the differential frame input.
Interesting... most of the dozers I’ve driven have clutches and brakes on each side, but they’re older. This must be how the new dozers function.
This is only one type of tracked steering. What you are talking about is still something that is valid, but with Lego it gets complicated to do because making breaks for each side of track gets complicated and also you should have differential lock when you're driving straight with that kind of steering. I've got a video on the steering with breaking, so check that out :)
I made a smaller but flawed one
if you are using 2 engines anyway- isnt the differential is unnecessary? ypu could instead just drive every track with its own engine...
you don't have perfect control over lego RC motors - when you lower the speed, you also have lower torque and those values vary from motor to motor. For bigger models it starts making sense. Also check out other comments as I keep repeating myself here.
Check
You could also just use one motor on each chain. Way easier. Nice mechanism tho :)
Intelligence!
Мега хорош
前進後退は真ん中、超信地旋回は隣のモーターってことか
両方動かすと信地旋回になるのか
両方の場合のギアの動きがわがんねw
I wish I could fully understand what you mean here. Can you try explaining it in English? google-translate doesn't do a good job with it.
As cool as it is, its a-symmetry hurts my ocd.
Or can you give me the link to where you can buy these two?
Compact flat subtractor / Double Differential - tank steering build
czcams.com/video/3_Xxrw2BSf0/video.html
Small steering hub revisited and a 6x6 prototype chassis
czcams.com/video/DNqy_S8GR7M/video.html
The parts in the compact flat subtractor are all original Lego Technic. The small steering hub is a 3D printed part and there is a thingiverse link in the video description.
Connecting the two motors to each of the tracks directly would have resulted in the same but without the complexity 😂
Not really. The quality of the motors matters, how controller outputs the power matters. Those are not precise linear motors that guarantee that you will have same amount of steps/RPMs on each motor, so it's a lottery on whether your motors will let you drive in a straight line or not.
@@SaperPl1Firstly… they’re definitely precise enough for a LEGO TOY😂. Secondly. HUNDREDS OF MILLIONS of machines around the world use non precise motor drives for tanks, skid steers, compact track loaders, zero turn lawn mowers, sod rollers, tractors, snow blowers, snow cats and even R/C versions of ALL the aforementioned machines.
It’s very easy to compensate for slight differences with the controls or even a speed sensing system that has the ability to monitor ground speed on both sides. Both are far less complex and exponentially more efficient and reliable than this.
@@brandoncrimmins6296 direct input gives direct control, this is true. This system will turn smoother though. Much less jerky. You should look up why differentials are important, and why they could but utilized to improve tracked vehicles.
@@brandoncrimmins6296why you mad about a guy building a lego tank. Also most of us clicked on this because we like the complexity. wouldn’t be cool if it were just 2 motors and 2 gears
I’m pretty sure dual differential tank drive allows you to steer a tank like a car. Again mentioned by others, it’s more smooth and realistic.
i see no reason to use this mechanism ,you are forced to run 2 motors anyway
Well, I keep explaining the same thing in those comments - the issue is that you can't be sure that both motors connected directly to the tracks will have same output either because of the motors themselves or how the power is coming from the controller. That's for one. For two, this is one of steering types used in tanks, this one is in more modern tanks, and it allows driving on a curve. If you wanted to make something like separate drives for each track in real tank, you'd have to have separate gearboxes for each track or a petrol-electric kind of drive that Porsche pushed for with his tank designs.
@@SaperPl1 look we have cars that have 4 separate motors for each wheel
we have cars with double petrol engines running front and rear axles separately
how do you want to drive on curve when your motors works 01 on or off
there is something called correction
every rc model does that there are even automatic ones using gyroscope
this design has no future its complicated mechanical design that have flaws of loosing power on friction and having higher chances of getting damaged
german tanks in ww2 were able to rotate in place and drive on curve having only one motor and doing it all on mechanical system
what what it lead to? all of them were breaking
there is no reason to chase after gears and transmissions when for past decade everyone was trying to get rid of them because they are weak points
@@OGNISTYSZKQAJDII Go look for videos comparing output/RPMs between motors from various vendors. BrickHouse had quite a few of those recently. Also check out videos from Sariel showing off those types of tank steering.
The motors in lego are not RC-grade quality motors people use in RC models, but just stupid DC motors and this doesn't compare.
It's not something that I've made up just to be cool, those steering mechanisms are existing ones being used. Of course now when we have quality electric motors like those in tesla cars, this is different, but it wasn't always like that.
As for german steering mechanisms breaking - actually, at least for the panthers, it's not the steering that was breaking, but the final drives which is a bit different piece - it's the reduction gearing that's coming out of the transmission/steering to reduce the speed and increase torque.
Also the petrol-electric drive where you have electric motors for each track and engine(s) generating power was breaking a lot in those Porsche tanks (tiger prototype, Elefant and Maus)
Finally I don't think it's the most used steering mechanism in WWII, the most popular one is probably simple differential/break steering where you break one of the side of differential so all output goes to the other side and the differential gets locked when driving straight. This is good enough for off-road and going straight, but when driving on curved roads this consumes the break pads a lot or is a general pain to drive this way.
This is something that's both for making it work more like the tanks do it and because lego motors are not perfect.
Reference for this kind of steering: i.ytimg.com/vi/_z3n6VOk-Ls/maxresdefault.jpg
Sariel's videos: czcams.com/video/f5_OQooBxdY/video.html czcams.com/video/h7GAZl6Il6k/video.html
@@SaperPl1 seriously, this is impressive. Please try to ignore the commenters trying to tear down your idea "because a real life tank doesn't do that / $50k cars have motors that can do this better!"
Do you people even hear yourselves?
looks useless if i right understand u cant use 2 motors to drive at the same time
That's one of the was to control steering on the tank. It's not useless. It starts to make sense for bigger and heavier models if you want to have some precision in steering. Lego motors as well as their clones are pretty dumb motors that do not guarantee the same RPMs and torque, so you'll have different speed on each track. It becomes more visible when you run them at lower power output as well, so driving in a straight line slowly will be impossible. Of course that's a toy and you can't just ignore those problems, but there are also models that people do to make them work more realistic.