Twin Gravity Powered Cars comparison
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- čas přidán 11. 01. 2014
- I hadn't really intended to do another gravity power car at the moment, but I was throwing out some packaging from some Christmas mince pies and suddenly thought "Gravity Powered Cars" and decided to make a pair and compare their performance.
The big factor in the performance of your car is friction. Either at the axle bearings or the pulley bearing so ensure they are free running. Experimenting with different sized pulleys may help.
Components
-
Cardboard box + plastic packaging
8 CDs
16 plastic bottle tops
12 barbecue skewers
2 plastic bobbins
4 cheap plastic beads
length of wire - a thick paperclip would do
Heavy duty fishing line (18 lb breaking strain)
Hot Glue
2 x 4 oz fishing weights
Tools
-
Hot Glue Gun
Hobby Knife
Pliers
Several people have asked how to connect the string to the back axle. To connect the string to the axle I have used many different methods in my cars over the years. You could just glue a short length of bbq skewer or toothpick to the axle so it makes a T shape then put a loop on the end of your string and loop it over the stick. Then you wind it up. The idea is the string should pull off the hook cleanly so the axle can then freewheel after the power (weight has dropped). If the string is too long it won't drop off the hook and will start winding up again eventually acting like a brake. If you start with the weight sitting on the car and push the car backwards it will wind the string round the axle and raise the weight. You might like to check out the two videos directly linked to this one.
Twin Gravity Cars Pulley Improvement • Twin Gravity Cars Pull...
Twin Gravity Cars reducing axle friction • Twin Gravity Cars redu...
Some helpfiles
Making the CD wheels • Helpfile - How to use ...
CD Wheels with Cardboard Hubs • CD Wheels with Cardboa...
Putting rubber tyres on CDs • Helpfile - how to put ...
Connecting rubber bands • Helpfile - Joining rub...
Connecting the band to the axle • Connecting a Rubber Ba...
Gravity Powered Car • Gravity Powered vehicles
Toy cars • Model cars
Twin Gravity Powered Cars comparison playlist • Twin Gravity Powered C...
Twin Gravity Powered Cars comparison • Twin Gravity Powered C...
Twin Gravity Cars Pulley Improvement • Twin Gravity Cars Pull...
Twin Gravity Cars reducing axle friction • Twin Gravity Cars redu...
Gravity Car Bicycle Spokes Chassis and Axles • Gravity Car Bicycle Sp...
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Good job😊
Thank you, there is more information in the video description 👍
Why do you cut of the small piece in the back axle where hole is to attach string. How can you attach string to axle if you cut in out.
I guess you need to watch the video again. I don't cut the axle. I cut a gap in the drinking straw that the axle goes through. That allows you to attach the string to the axle. If you don't cut a gap in the straw how can you attach the string to the axle? I tie a loop in the end of the string and I glue a very short length of BBQ skewer to the axle in the middle making a T shape so you can hook the string loop over it. That allows the string to drop off when the weight has dropped so the car can freewheel without the string getting tangled back up on the axle.
What do I have to fix if my car goes fast but stops halfway? I need it to go 20 feet but it ends up going 10 feet fast and stops because the weight falls down too quickly.
First thing to do is make sure your car can freewheel properly when the weight has finished falling. Much of the distance traveled is by the momentum of the vehicle after the the weight has got the car up to speed. Have you tied the string to the back axle? It needs to come of the axle so the axle can spin free so tying it is a bad idea.
Im sorry to say this, but after 5+ hours of following this tutorial, my gravity car still does not work, i wish you had spent more time explaining the winding up process because my car winds up but doesn't move. Now I have finished car that doesn't move unless you push it. Please explain how to attach the string better so others can understand.. Thank you.
First it says nothing about being a tutorial. It is an attempt to compare different sized wheels. There are currently 36 videos in the associated playlist with various different designs if you look in the video description for the link. The most likely reason for the lack of movement for your car is friction. Either at the axle bearings or the pulley bearing so ensure they are free running. Experimenting with different sized pulleys may help. To connect the string to the axle I have used many different methods in my cars over the years. You could just glue a short length of bbq skewer or toothpick to the axle so it makes a T shape then put a loop on the end of your string and loop it over the stick. Then you wind it up. If you start with the weight sitting on the car and push the car backwards it will wind the string round the axle and raise the weight. You might like to check out the two videos directly linked to this one.
Twin Gravity Cars Pulley Improvement czcams.com/video/k-kZzlY5cTE/video.html
Twin Gravity Cars reducing axle friction czcams.com/video/0FpP3qRDAS0/video.html
Did you use type around the border of the CDs?
Hi Lexi, I re-used the wheels that I had been using on my rubber band powered cars and they had strips of rubber cut from washing-up gloves stretched around the rims, but didn't really need the extra grip so I took the strips off in later videos.
I was reading the description and was wondering what is the wire, or thick paper clip for?
02:32
GrandadIsAnOldMan Can you also help me by telling me how to tie the fishing line?
Here is a site that gives you guidance on tying knots www.animatedknots.com/indexfishing.php#ScrollPoint
GrandadIsAnOldMan I was actually asking on where do I tie the fishing line to
carlos liu you tie one end to the weight and you have a loop on the other end that hooks onto the peg on the back axle. The peg on the back axle is just a short bit of bbq skewer glued in place.
Hello! can you please tell me the principle behind the working of gravity driven car ? does it use any laws ?
Energy is stored by lifting the weight. So that is potential energy. The energy is converted to kinetic energy as the weight falls and the string turns the axle driving the car forward.
Wow! Thank you soo much GrandadIsAnOldMan. Only this much I thought there would be some laws behind the working. I am doing the gravity driven car for my mechanics project and my teacher would question me on its working. Thank u once again.
Junia Shelomi yes you can include Newtons laws of motion but may be a bit more difficult to explain or prove. The energy in - the weight dropping - will equate to the energy used by the car moving. So you would have to know the mass of the car and measure the distance traveled, the velocity and then make allowances for friction etc.
yes i think I will give it a try to include the laws of motions and if i have any doubts I'll ask you. thank you soo much
Junia Shelomi good luck :-)
Do you think a mass of 1kg falling from 10 cm would cause the car made out of the box go faster? (ASAP)
+Kevin Jimenez the problem would be that a 1kg weight will probably bend the axles so you would need to make it stronger. Here is an alternative idea czcams.com/video/laTDJk79H00/video.html I did another one recently using Vinyl LPs - old records - using a 1Kg weight and it ran 10 metres easily. The video is already uploaded but scheduled for publication on 27th January. To give you an idea it looks very similar to this mousetrap car czcams.com/video/v1n4PtRaM9Y/video.html
+GrandadIsAnOldMan
Do you think there is anyway we can see the video?
***** it is the same in principle as the cars in the links I gave you in my previous reply. Try watching them. The only difference is the wheels are Vinyl LPs. There are not many different ways you can build a car with just 2 wheels and an axle. As this is obviously your school project I am not sure I should do your work for you, I have given you some guidance and advice and I am giving the same advice to everybody else who is asking me about a 1kg drop project.
+GrandadIsAnOldMan Where could we possibly get the "Vinyl LPs"?
***** how should I know? I don't even know where in the world you live. All you need is two disks for the wheels, the bigger the better. The video link showed you one I made from cardboard and that worked fine rolling for 5 metres with only a 4 ounce weight.
I v tried with seven box like you use but it didn't went far
The distance it goes is related to the friction of all the moving parts. In the video description there are links to several videos that give you hints and tips on improving the performance. The type of box is pretty well irrelevant, it is the axle bearings and the pulley that makes the difference.
Hello! I just wanted to know if your mass was 1kg?
+Cherei Tree if you mean the lead weights, they are 4 oz lead fishing weights. The details are in the video description.
+GrandadIsAnOldMan
Thank you! Do you think this can carry 1 kg? I'm planning to make a joule mobile, but it can only fall 10 cm with one kg. Do you have any tips? Thank you so much!!
Cherei Tree I am assuming you have to cover a certain distance. If you can only use a 10 cm drop you will have to ensure the car runs freely with minimum friction so you get the benefit of it freewheeling after the power has finished. There will be an optimal wheel size and axle size to get the best out of the drop. Larger wheels will cover a greater distance for a give number of revolutions but require more power to start them rolling. Smaller wheels will accelerate faster put the power will run out over a shorter distance because they travel less distance for the same number of revolutions. The diameter of the axle will set the number of turns of string you get round it from a 10 cm drop. The bigger the diameter, the less number of turns and therefor the less number of revolutions for the wheels under power. The smaller the axle diameter the less power it has to turn the wheel so a small diameter axle may mean you cannot turn a large diameter wheel.
+Cherei Tree the problem would be that a 1kg weight will probably bend the axles so you would need to make it stronger. Here is an alternative idea czcams.com/video/laTDJk79H00/video.html I did another one recently using Vinyl LPs - old records - using a 1Kg weight and it ran 10 metres easily. The video is already uploaded but scheduled for publication on 27th January. To give you an idea it looks very similar to this mousetrap car czcams.com/video/v1n4PtRaM9Y/video.html
+GrandadIsAnOldMan Thank you very much for your detailed answer. Your advice is very helpful!! I'm on the process of finishing it up :D Thanks and wish me luck!
Btw, were you a physics major /teacher or did you just like the subject? You seem very knowledgeable & happy with what you do-- so kudos to you :D
can they travel at least 7.5m?
Probably. In tell you in my video they travel the length of my kitchen which is 5 metres and hit the wall at the end. The important thing is minimising friction so if you pay particular attention to the pulley at the top you can improve your performance. Also need to make sure your axles run freely. Much of the distance travelled can be the freewheeling after the weight has dropped. I did not build these to go a long distance, I just wanted to compare a few options like the size of the wheels.
do you know how i can make one that goes 10 meters
The distance it travels is very much down to the friction and inertia. If your bearing surfaces have minimal friction it will travel further, so the pulley and the axles need to run freely. Lubricate the bearing surfaces, consider using ball races. A heavy weight will give you more inertia to get the car moving faster. A taller tower will give you a longer distance for the weight to drop. The distance the car travels forwards with each revolution of the wheel is the circumference of the wheel, so a small wheeled car will travel less distance than a large wheeled car. I have no doubt you will be given some specific criteria for your project, so I cannot guess what your car design would be without knowing those details. If you read the video description I have already given advice and useful links.
@@GrandadIsAnOldMan ok thank you
Hola me gusta
Thank you. There is useful information in the video description.
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