Re: pic: VEX High Reduction Gearbox
 

Also inertia :(

Someone please correct me if I am wrong but wouldn't you be fighting a force of 1/12(mass)(3*radius^2 + height^2) * 244140625 Newtons to get it started? Now, maybe if you put a crazy long lever arm on the small wheel's shaft you could over come that.

Of course, even that number is almost nothing compared to the real number because you would have to account for starting the gears rotating too. This could be an interesting problem for more advanced students, What is the max length of a lever arm you could attach a 100 kg weight to and still not have the large wheel move? Have them run it both ways.

But very cool John.

Re: pic: VEX High Reduction Gearbox
 

What I want to know is what the backlash is at the input gear. It has to be several thousand full revolutions of the input shaft. Which amuses me to no end, given I'm usually working with gearheads that measure backlash in minutes of arc....

Re: pic: VEX High Reduction Gearbox
 

Now try replacing all those medium gears with the large gears. :D

Re: pic: VEX High Reduction Gearbox
 

Cool gearbox, JVN!

We had a guy call us this past summer, wanting to use a Toughbox and a low power motor to slowly move a parabolic solar panel so that it follows the sun.

So... we found a small gearmotor package from Dayton, and used that as an input to the Toughbox. We bench tested this assembly and found out that the output shaft of the Toughbox was doing 1 revolution in about 18 minutes. Of course, this is much faster than the Earth is spinning, but it was a good way to use a very low power motor to move a 12 foot long solar panel.

AB

Re: pic: VEX High Reduction Gearbox
 

Now lest see you "back-drive" that!

Re: pic: VEX High Reduction Gearbox
 

Have you seen the mini jet engines that are in the fancy rc planes? Some of those spin up to around 150,000 rpm. At that rate it would take a little over a day to turn the wheel.

Re: pic: VEX High Reduction Gearbox
 

It's going to move the large wheel if you apply any torque to the small wheel at all, the amount of torque just determines the acceleration, which will be tiny for any reasonable amount of mass. The only thing that might actually stop the entire thing from rotating is the friction in the bearings, which I don't think is very large.

Re: pic: VEX High Reduction Gearbox
 

Thanks, you can tell it has been a while since physics.

Re: pic: VEX High Reduction Gearbox
 

That is, before the thing starts melting or grinds itself into pieces...

Re: pic: VEX High Reduction Gearbox
 

Wow. This is just plain cool. =]

Re: pic: VEX High Reduction Gearbox
 

Heh - very cool. If you could "drive" the big wheel from the Earth to the Moon (at apogee, the approximate distance is 251,968 miles), the little wheel would turn only 4.1629 times.

-dave



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Re: pic: VEX High Reduction Gearbox
 

Say we're driving on the big wheel to Mars ... how many little wheel turns?

Re: pic: VEX High Reduction Gearbox
 

At closest approach (such as during the perihelic opposition in August 2003) the Earth-Mars distance can be as small at 34,646,418 miles. In that case, the little wheel turns 572.418 times. During conjunction, such as the one just ending this week, the distance can be approximately 247,821,000 miles. In that case, the little wheel turns 4094.437 times. I would find that number to be excessive, so for a Mars transportation application I would want to add on at least one more 12:60 reduction stage. :)


-dave



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Re: pic: VEX High Reduction Gearbox
 

I would like to thank both John and Dave for finally making me understand how far away mars is :D

Re: pic: VEX High Reduction Gearbox
 

All I can say is - we are such geeks!