Instructables

when making a gear system with a push mechanism, which allows it to move easier? more gears or less?

I am trying to design and build a recreational vehicle with a push system instead of a motor. (similar to one of the old toys were u pushed in a button to rev up a part of the toy and the faster u pushed the faster the speed .) im trying to make it as easy as possible to get the "vehicle" moving.

More gear less pressure on push slower speed.

Less gear more pressure on push faster speed.

Now if you add a spring storage system between the push pump and the drive like a clock main spring you can get the best of both for short bursts.

Joe
rickharris11 months ago
Try doing some calculations around the amount of energy you might store in a spring or flywheel. I think you will find the power to weight ratio disappointing.

http://justinsomnia.org/2007/10/my-dad-and-his-life-size-rubber-band-powered-car/

you could try this idea - It was done in the 30's I think but I can't find the reference now.

The rubber bands were cycle inner tubes. The transmission a simple rope round the axel. Bands stretched by winding the wheels backwards.





rubber band car.jpg
mpilchfamily11 months ago
You have a huge problem of scale here. Yes you could build a similar mechanism large enough to drive the car. Problem is the amount of pressure that it would require to get the car moving. No amount of additional gears will change that. Sure with enough gears you can make it easier to push the button but the returns from that press will be almost none existent. Thus requiring thousands of pushes to even move the vehicle an inch. Keep in mind the more you gear things down to make it easier to operate the more times the initial set of gears has to rotate to get the end set moving at all. In the end you'll have to expend more energy into the gearing to get the car moving than you would just my putting your back into the vehicle and pushing it.
curvy77 (author)  mpilchfamily11 months ago
I think i may not have been very clear. The vehicle will be about gokart sized and (prototype at least) will be made of wood. At that size and weight (car without driver....estimating 100lbs. At least.) Should be easier to propel it forward. O and most important, its not build up of pushing. More push as u go. Kinda like a bike but with one pedal.
Is this intended to make it easier on those with only one leg? Whether it is or not you'll want to go with a basic transmission like that of a muti speed bike. If it has to be a single pedal that can only be pushed then you replace the bike peddles with a spring loaded shaft with gear teeth on it. So when the pedal is pushed it engages the first gear and rotates it then springs back when released ready to engage again.

That toy car gets the wheels spinning very fast on a single push. In a large scale item like a 100+ lb gokart it would take a large amount of pressure to get that going and all you would achieve is the tires spinning out. You better off with changeable gears so the first pushes of the pedal only rotate the tires a bit. As the pedaling becomes easier you shift gears so that each push of the pedal is getting a little more out of the tires till you reach a point where a single push is giving you multiple rotations of the tires.