Over centre mechanisms will make your designs more effective - Guide with examples
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- čas přidán 20. 05. 2024
- If you only learn to design with one mechanism, make it an over centre mechanism. In my opinion, this is one of the most versatile and effective mechanical systems you can utilise. In this video, we look at real world examples, and then break down the characteristics across a series of different designed examples. The final example is a CO2 dragster launcher, and stores enough energy to puncture a canister despite only needing the smallest nudge to activate.
All of the printed examples plus the F1 launcher on Printables: www.printables.com/model/4519...
Goat graphic: openclipart.org/detail/313163...
0:00 Introduction
0:43 Where do we find over centre mechanisms?
1:00 Example 1: Basic
3:07 Example 2: Closing latch
5:38 Example 3: Cam latch
8:22 Example 4: C02 canister firing system
F1 in Schools Australian champions: • Winning the F1 in Scho...
F1 in Schools equipment video: • F1 in Schools - Equipm...
F1 race control system: store.rea.org.au/f1-race-cont...
My launcher assembly video: • F1 in Schools / CO2 dr...
11:25 Key characteristics summary
12:12 Conclusion
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Please make more videos like this in the future. Learning about simple mechanisms that could be incorporated into my own designs is super useful. You did a very good job of explaining this one and it’s potential use cases.
I'm a MechE student in my 3rd year and while I already knew about this mechanism and learned how to design them, it can't be understated how valuable it is to see real examples like these. Thank you for making this video, I now have more ideas on where I would apply this mechanism that I may not have thought of before!
Quick tip on rigid over-center mechanisms. By Hooke's law, sigma (tension) equals E (Young's modulus) x epsilon (strain). And strain is given by deltaL (in the case of the video Arm lenght delta) divided by L (lenght of the part that is the replacement of the spring or rubber band). Combining both we can see that for the same elongation (deltaL) the bigger the part, the smaller the tension.
When switching from PLA to PETG, one plays with the Youngs Modulus, which is lower on PETG, hence creating less tension for the same lenght and elongation of the part. This is what makes it more elastic.
As always, great video.
yeap, instead of switching, he could just make a planar spring (like a sinusoidal slender segment) and you should be fine. PLA makes quiet good spring (because of their comparative high young modulus, you need less mass to store the same energy compared to other plastics) if you design them well (limit max deformation to low values (no more than 6%)) and in applications where the spring forces only matter at transient states (so you avoid creeping)
@@giuseppebonatici7169 yes but that kind of deviates from my initial consideration. The shape you are mentioning, and pretty correctly, would be a spring itself. I'm talking about rigid parts. If you can call them rigid. He he he
@@giuseppebonatici7169 Very important last bit, was gonna comment on that, PLA having as much creep potential as it does, any PLA spring would be necessarily unloaded most of the time to be reliable in the long therm (heck maybe like, days).
I always go with ABS whenever possible for any part that stays loaded in a way or another, when not possible PETG is my go to material.
something something everything's a spring
@@satibel indeed it is. However the trick in this is the balance and harmony of plasticity and elasticity. Given that you can't change the parameters at will, you have to go through the design route. And that requires some knowledge on materials and/or "touch".
I am a fan of this content. Been subscribed for years, afaik, but this "jumped the shark" in a good way for me. Maybe I haven't been paying enough attention to your channel, but I love this. Thank you.
The concept of breaking down design concepts of specific mechanisms is marvelous, and your presentations are always nice and concise.
While PLA is objectively a bad material for any "spring" mechanism, it's worth noting that layering single perimeters next to each other offers more "springyness" vs the same thickness as a fused perimeter. Same principle as thin stranded wires in cables vs the stiff single strand ones. Many individual thin strands can flex much easier than one solid one that exceeds compression on one side and tension on the other.
While many people say a bigger nozzle can produce stronger prints i've found the opposite to be true bc of the reason you stated, i speak from experience working with figurines, tended to prefer bigger nozzle sizes until i realized it.
Do you mean have air gaps between perimeters? It makes sense that it would bend easier, but will it really help with elongation?
@@polycrystallinecandy Yes, that's what I meant. And the answer is "kinda".
As stated, PLA is awful when it comes to being a spring.
But material structure is quite intruiging and the finer you go with a given material, the more "springy" it becomes.
The best example are modern phones, or to be more precise, their accelerometers. These are nothing but nano scale silicon parts that flex with amounts that would shatter the same material if it were a millimeter thick.
Same way how the fine stranded copper wires can be bend and twisted fine (within reason), while the single strand versions, meant for permanent placement, would work harden and break rather quickly from the same bending and twisting.
Obviously, when printing springs with this approach, it comes with the cost of less stiffness. So experimentation is needed regardless.
But the lifetime of the flexing parts would be drastically higher.
Another benefit, more related to PLA in particular, would be that it's likely that only one spring "strand" would fail at first, and not the entire section.
Since PLA often tends to reach critical failure with little warning, it would help to have several points that all are stressed differently in the same section, that way some can fail first as a warning before all have failed.
But this depends highly on the design and applied forces.
One design might even be better off, once one or a few strands have broken, another might overload all of them at once.
Nice! That one latch is still over-centered, it’s just also a compliant mechanism, so a compliant over-center latch.
Also, in the cutout that affords the springiness, the narrow ends of the hole being round will extend the life of the mechanism. Those sharp points are more likely to spawn cracks as well as taking longer to print than rounded profiles.
I love using over center mechanisms in my designs. (and I'm a mechanical engineer who's been doing it for years)
Do you have some links who explain all of those mecanism ?
What other systems do you use?
This type of mechanism can also be used in reverse. Think of a gas strut on a concession window. The strut holds the window open, but when closed, it will reach a minimum compressed strut length and begin to extend a bit when nearly closed. This keeps the window from opening. 😊
It's amazing how something so simple can be so useful! Thanks for helping me understand these mechanisms!
Wow, this has to be a series for other mechanisms as well! - That would be exactly what I have been searching for a long time!
Love the deep dive!
Michael, thank you so much for your continuous contributions. There are certainly more reasons not to have a youtube channel than to continue working as hard as you do to put out such fantastic content. Thank you. I learn valuable information every time I watch your videos.
Weirdly enough, I've been doing a lot of research of late because I have a need for such a thing, but have been having a hell of a time finding such specific info. Your timing is impeccable!
Please make more of videos like this!!!!! You explained it so well, and I loved how you showed real life examples
Agreed.
bro I cannot put into words how thankful I am you've made this video, I've been trying to design a waterproof lid on a new product I hope may save lives down the line and I've needed exactly this information but not come across it until now. thank you so so so very much!!!
I made a drawer lock and release mechanism out of a broken biro and a broken barrel slide lock which had lost its lock pin five minutes with a grinder and way more blood than would seem appropriate for a tiny puncture wound winding the spring setup I'd made. Gotta love brass cuts they just keep leaking. Now you can open and close the drawer without it going past the end point and pull a tag to release it to access the dishwasher.
👏👏👏Well done! I would love to see more videos like this one. Your excellent explanation and visuals via the CAD graphics as well as showing your multiple iterations up to the final product help make this concept much easier to understand! Thank you my friend!
Hello from Greece from a fellow designer. I would like to thank you for all the effort you put in your videos and we are all grateful for the knowledge that you spread. The way you do it is really informative and fun, and your videos have saved me countless times, I can't be thankful enough.
These kind of tutorials are what i truly do need.
Always been fascinated by this mechanism. Thank you for the great video!
Michael. Since getting into 3D printing, about a year ago, I have gone through the progression that I think most of us have, which is download stl's then changing the original design to fit our needs then start to design our own stuff. On the final step, what do we do, hit youtube and figure it out. After much browsing I decided on blender. It works very well, but it's very confusing. While hitting youtube regularly I found a few people that I liked to go to all the time. CHEP, BV3D, and a couple of others. But I am SOOO glad that I found you! Because of you I switched to Onshape, and LOVE IT! You also explain things very well and make it easy to understand. Please keep up the GREAT content.
Dude, please keep making these videos - these theories has/will outlive us
Such a great presentation - thanks for putting together because it’s so helpful.
Needed this for a project I'm working on right now. Great timing! Thanks!
With teachers like you i might have actually enjoyed mechanical design in college! This is such a good video and explanation! Thank you!!!!!! I'm the least mechanically inclined person you'll meet and this made sense.
I'm very grateful for your videos for this reason: You don't need to exaggerate your voice or use lots of gimmicks to keep attention. You're just a likeable guy with a voice that doesn't grate on my ears. It's refreshing. Oh and you have good content. Equally important lol.
Awesome vid. One thing - the "center" that makes it "over center" isn't (from your first example) the center of overall travel, but the center of alignment 90 degrees away from that point. In that example the center line of the rubber band is in line with the center line of the swinging bar...and then goes "over center" to latch. Same in the vise grip if you watch its bars move.
I really wish you'd taught me in school. You are a great teacher. You explain things so well
Very educational and a well made video, would love to see more like this!
Thanks for the video Michael, fantastic tutorial!
Pretty fascinating stuff! Thanks a bunch, Michael! 😃
Stay safe there with your family! 🖖😊
Your videos are fully of knowledge. Thanks for sharing!
This is a fantastic video. Great explanations and examples
I was looking for such a mechanism. Thank you so much!
Excellent Video, you have always been the absolute top of the CZcams achievment.
Nice. Been using these kinds of designs for years but never knew the name of them which of course makes it that much more difficult to research them. Good stuff. If you need video ideas, by all means do other mechanisms.
Very well done. I did not know you were a teacher however, it clearly shows in your presentations.
You truly are an educator, sir!
He really is haha. He’s a teacher.
More of this. That was amazing!
Loved this vid, felt really understandable and intuitive. I think it'll be very helpful in my designs.
Having a curve in the latching part makes it a spring. Here you can carefully tune it so that the range of motion when it’s flatting on the top position is not too much. Also print it so that the layers are length wise.
outstanding video man. ive been searching for this type of mechanism for a while now but i diddnt know what to call it, let alone decode the hows and wheres. over center makes all the sense in the world. im working on a sliding table saw and needed a way to lock in place on 20mm linear shaft, with the help of this video all my questions about this specific mechanism were answered. and anything that i wasnt totally sure of became very clear as i constructed the mechanism in cad. thanks a million bro!
Great video! Thank you for making it and sharing the launcher design. To answer your question, with a bit of question, I think it depends how you you define mechanism. I think as in most things, simpler is usually better, and you have a fairly simple multipart mechanism. But if a mechanism is just another name for machine, then I would go even simpler and say that an inclined plane is just about as good as it gets. A little more complex and an axle is a pretty great one as well. Interestingly enough, you used both of those as parts of your various mechanisms. And if the whole point of the title, and question was just to get pedantic folks like me to comment, well that also succeeded. Thanks again for doing all you do.
great vid, like others have said: I would love to see more with this format
Awesome video, really enjoyed learning about such simple and yet ubiquitous mechanism!
Very informative! Havent heard of this one before, very much appreciated this video
No way! This is one of my absolute favorite mechanisms too!
One of your best videos ever!
Fantastic tutorial, thank you!
I love love this! Definitely you should make more videos like this in the future!!
Thank you for a simple explanation of a handy method.
I am guessing from the school footage, your classes were far from what I remember school being like, almost pre-recorded monotone "Open your books to page..."
Thanks for the video! Been needing to design a mechanism like this and this is a big help.
Great video as always
Thanks for sharing 🙂
A handy and clear video! Thank you.
Great idea and presentation!
I didnt go to school for engineering but i ended up designing a mechanism like this for a weight set i have. Its fantastic.
You can tell you were a teacher previously as this video is an excellent explanation of "over centre mechanisms". Been using them for decades but never thought about the how do they work? Now I know. A thumbs up seems inadequate thanks but of course, I have.
11:19 is an impressive bit of timing, an ever growing car or cheeky editing. Good tut.
love this kind of video. great job
Thanks for the incredible video!
Just one part of engineering, and they are very helpful toggle clamps on jigs and fixtures being an example.
Vice grips also use an over centre mechanism.
Heavy doors sometimes need them on the hinges to help stop bounce.
For any such mechanism that stays loaded during operation, PLA is definitely not a material to rely on, PETG has a big advantage here and ABS much more so, not because of stiffness, but creep. You wouldn't want your latch to suddenly loosen with time, but with PLA it will happen, and it won't even take that long. PETG handles creep much better and ABS is the king as far as I know without going into extremely expensive engineering polymers. Would love to know good materials on this property as well in case anyone knows.
Interesting video. I'm currently working on and extruder design that will use an over the center mechanism to hold back the spring pressure on the idler carrier for easy filament removal/insertion. I didn't know the mechanism had a 'name' so to speak, I just knew how it worked and thought I could apply it in the extruder design. When the 'release' lever is lifted, it will lock at just over center for filament insertion/removal, when the lever is pushed down, it will go over center and allow the spring pressure of the idler carrier to take over again. This should allow for adjustable pressure on the filament via the usual thumb screw/spring assembly and easy filament insertion/removal via lever/over center mechanism. I hope so anyway. I've been tinkering with the idea on and off but the design is still in very early stages at the moment.
It was an awesome video, I would love to see more mechanism videos!
Excellent work! Please create more content on different mechanisms.
Another very simple very useful very cool mechanism is the humble flexture.
Love learning about mechanics in 3d printing life
Nice info, thanks for sharing it :)
In my experience PETG is great at first, but as it absorbs moisture or ages by some other mechanism I am unaware of, it gets weaker and notably more brittle. Just a potential warning.
I do find that you can design around stiffness with a more framelike /skeletonized structure.
Great explanation. Thanks
Nice content, great teacher!
Wow crazy you made this today, I was just looking into the mechanics of vise grips.
Great video! I think I'll use this info for a latching clamp for an extendable pole. The clamp uses 4 M3 screws right now and is a pain to remove.
Yoooo. Great video. Thanks!
love cam locks!
Thanks for the video 👍
This brings back memories of high school
Never knew what this was called, thanks!
Very cool video, thanks.
Love this video!
Really good video!
Its so cool, thank you very interesting.
Excellent!!!
Excellent!
Great video. I've always found the push-push switch mechanism to be the 'GOAT' for me. Any device where the same 1 action can toggle between 2 or more different conditions is so satisfying to use when done correctly. Would love to see your thoughts on it.
Great video
This is a good example of quasi stability
Thanks mate, always wondered what the mechanism was called as I tried to search but never had the correct name.
Informative ✌ Good content 👌 thus I has to subscribe 😊, thanks!
This is very cool.
If I may suggest one more thing to add to the CO2 dragster launcher. Some sort of safety interlock. Because it just take a sharp slap to get it to fire, that creates a hazard for use. My first thought (it might not be the best, take this as a brainstorming idea) is to add a servo. I'd probably use a 2 horn servo attachment. One of the horns would hold the firing pin in it's cocked position, the other horn with some sort of spring to pull it into safe position should there be a power outage to the launcher. I was at first thinking of another bi-stable mechanism on the safety, but if the firing mechanism is sensitive enough to fire with a sharp slap, then the vibration from "snapping" the safety open might cause the firing mechanism to fire. Though, I suppose a simple pin through holes in the side panels would work just as well and be simpler...
this is actually great for PLA which has a very bad tendency to creep even at room temperature meaning it is a terrible choice for parts under constant tension or compression as in most fastening mechanisms--except for over center mechanisms which do not store any compression or tension in the fully open or closed positions, only temporararily!. excellent!
I've never seen anyone animate OnShape sketches before. I've never thought of doing that, but I will in the future.
What great timing ....... Im in the middle of designing a switching duel extruder system. And have been pondering how to do this with a servo, but then thinking can the servo hold enough pressure for long enough to keep everything accurate without burning out. Along comes teaching tech with over centered locks ..... mmmm Im thinking whilst watching "how can I use this to help me ...... Then the car launcher ..... yes that will work for me ..................... now get back to designing it lol
I love these videos. So informative and practical. Knowing that PETG is better for a plastic that stretches makes me wonder whether Nylon would be even better? I assume TPU is too flexible, and assume ASA and PC are too stiff?
I think Nylon would be ideal. It's just harder to print.
This type of content makes me set notifications to "All" 🍻🤓
Where can I find more videos like this?
Learning Design Patterns are the key to mastering anything.
Great lesson, thanks for that. I use onshape also, but how do you move the sketch on a point? I tried, but it failed. Do you have also a lesson for that?
Thanks!
Now I know how to open a bottle of beer! That's what the iron bracket is there for! ✌
Please make a detailed analysis of the operation of buttons on trousers in the next video. Thank you in advance! ❤
An over-center mechanism without a sear would make up for an incredibly smooth and dangerous gun trigger 😀 I wonder if set triggers actually work this way, pushing the hammer close to a over-center state but not past it and locking it with a second less loaded sear? Don't know too much about guns but just came into my mind..
I would have loved having you as my teacher...