pic: VEX High Reduction Gearbox [Archive]

JVN

15-12-2008, 23:38

This is something goofy I made which is inspired by the concept of a millennium clock. I've made plenty of things which spin really fast, but I've never made something which spins VERY slow; I think this qualifies.

I use it as a lesson for Robowrangler students. I ask them to calculate some things as a way of proving they learned their gear theory.

I thought maybe someone here would think it is cool.

-John

s_forbes

15-12-2008, 23:44

Hmm... I'm suddenly tempted to add a year hand to my LEGO clock (http://www.youtube.com/watch?v=ItMgCJB90f4).

AdamHeard

15-12-2008, 23:46

Is it even possible to turn the little wheel by hand?

This is one of the most ridiculous/amazing things I've seen recently.

JVN

15-12-2008, 23:51

Is it even possible to turn the little wheel by hand?

This is one of the most ridiculous/amazing things I've seen recently.

Thanks!

No, it takes a lot of effort to turn even the 4th 60t gear from the input. I've had this gearbox sitting on my desk for a few months and every so often someone gives it a spin. Even after all this time we've been unable to advance the small wheel a noticeable amount (you can see the sharpie line we added when I first built the gearbox on the top of that wheel.)

-John

Qbranch

15-12-2008, 23:54

Wow... with that kind of gear reduction... I bet you could move the Earth!

...well... provided the gears don't explode first... :o

Great nonsensical gizmo. I think I'll dub it the Neunian Reduction Box for my memory.

-q

IKE

15-12-2008, 23:54

If my 24 hours of lemons team took this with us driving from Detroit to San Francicso, strapped on the back of the back of the race-car for the full length of the race, and then drug it back to Detroit, the little wheel would have only turned about 40 degrees.

Another way of looking at this is 1 JVN small wheel degree is equal to about 168 miles. In order words, our trip to Atlanta this spring is only 4.5 JVN small wheel degrees. That doesn't sound so bad.
:yikes:

JVN

15-12-2008, 23:57

MrForbes

16-12-2008, 00:12

Hmm... I'm suddenly tempted to add a year hand to my LEGO clock (http://www.youtube.com/watch?v=ItMgCJB90f4).

How's that Fluids studying going? ready for the final?

Neat gearbox...in the old days cars used to have mechanical odometers. The cable driving it turns 1000 revolutions per mile. The odometer has 6 digits, the first one turns one revolution per mile. I guess it's a similar concept.

sanddrag

16-12-2008, 00:34

Reminds me of something the artist Tim Hawkinson made once. A ridiculous gear reduction, where the input spun at several thousand RPM, and the output would take hundreds of years to make one revolution.

Barak Shelef

16-12-2008, 01:22

haha... I was just yesterday teaching our new team members about planing a good reduction gear assembly. I'll show them this picture ;)

colin340

16-12-2008, 11:45

How's that Fluids studying going? ready for the final?

Neat gearbox...in the old days cars used to have mechanical odometers. The cable driving it turns 1000 revolutions per mile. The odometer has 6 digits, the first one turns one revolution per mile. I guess it's a similar concept.

dang you got busted !!!!!!

thats really cool john

Greg Needel

16-12-2008, 11:55

This is the kind of goofy stuff I make my students calculate.
It is an awesome learning aid. It makes a pretty cool piece of desk art too.

I think this is awesome. I think I am going to borrow the idea for my team, but we are going to make a "Shipdate countdown clock" So Whatever day they build it they will have to calculate the right ratio for a ~60 day output cycle.

Now the real question, has anyone ever run a vex controller for 60+ straight days using a power supply?

Madison

16-12-2008, 12:02

I think the makes it reasonably possibly to accelerate the larger wheel to the speed of light.

MrForbes

16-12-2008, 12:23

I think the makes it reasonably possibly to accelerate the larger wheel to the speed of light.

If not for that pesky friction....

Andrew Schreiber

16-12-2008, 12:41

If not for that pesky friction....

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.

Kevin Sevcik

16-12-2008, 17:55

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....

daltore

16-12-2008, 18:04

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

Andy Baker

16-12-2008, 18:10

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

Rupnick

16-12-2008, 22:41

Now lest see you "back-drive" that!

Bannanakin

17-12-2008, 02:14

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.

Mr. Freeman

17-12-2008, 06:38

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.

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.

Andrew Schreiber

17-12-2008, 08:43

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.

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

Eugene Fang

17-12-2008, 16:36

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.

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

Libby K

18-12-2008, 08:38

Wow. This is just plain cool. =]

dlavery

18-12-2008, 10:01

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

.

Rich Kressly

18-12-2008, 10:15

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

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

dlavery

18-12-2008, 11:05

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

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

.

AdamHeard

18-12-2008, 16:47

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

.

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

Raul

19-12-2008, 20:13

All I can say is - we are such geeks!

JVN

19-12-2008, 23:15

All I can say is - we are such geeks!

Totally... and proud of it.

Are there people out there who don't geek out over stuff like this? Weirdos...

Abrakadabra

20-12-2008, 22:59

Arthur Ganson has a sculpture at the MIT museum called "Machine In Concrete" that consists of a 12-stage geartrain, where each stage reduces the speed of rotation by a factor of 50. The left end is spinning furiously at around 200 rpm; the right end is embedded in a concrete block. The end in the concrete makes one revolution every 2 trillion years or so.

Here is a partial picture of the machine from Ganson's own website:
http://www.arthurganson.com/pages/sculpture%20image%20pages/Concrete%20page.html

But to really appreciate it, you can see a video of the sculpture (and Ganson's comments about it) at the 8:30 mark in this video from the 2004 TED conference:
http://www.ted.com/index.php/talks/arthur_ganson_makes_moving_sculpture.html

T3_1565

21-12-2008, 19:24

I have always wondered how fast you would need to spin something for it to spontaniously combust.... care to give it a try??:p :p :p

Greg Needel

21-12-2008, 20:36

Along these same lines anyone care to predict what the lifespan of a vex motor constantly running would be?

Rich Kressly

22-12-2008, 13:45

Along these same lines anyone care to predict what the lifespan of a vex motor constantly running would be? I don't know the answer, but we're certainly thinking about doing the same thing :)

Rich Kressly

21-04-2009, 14:35

Thanks to senior Petra Hartman LMHS now has its own version of the JVN High Reduction Gearbox to teach gear theory to 1712 members and students in the Engineering Design classes. Woot!

http://www.chiefdelphi.com/media/photos/33863?
http://www.chiefdelphi.com/media/photos/33864?

JVN

21-04-2009, 14:42

This gearbox was on display in the 148 pit in Atlanta this year. I noticed quite a few people playing with it.

Andy L

21-04-2009, 14:53

This gearbox was on display in the 148 pit in Atlanta this year. I noticed quite a few people playing with it.

I spent a few minutes playing with it, and trying to explain it's coolness to some parents, they didn't share my enthusiasm for it.

Crump

22-04-2009, 13:52

i think it would be fun to make one of these gear reduction towers and make it turn once every 42 days... the 42 days is completely an arbitrary number :)

Jared Russell

22-04-2009, 13:57

This gearbox was on display in the 148 pit in Atlanta this year. I noticed quite a few people playing with it.

John -

In the spirit of absurdly high gear reductions, maybe next year you should put something like this on your drivetrain as soon as it is constructed. Paired with a ratcheting rectifier, you can make yourself a pretty nifty odometer. I've always been curious to know precisely how many miles a 148 robot travels in the course of build, practice, and competition...

IKE

06-07-2009, 16:58

Totally... and proud of it.

Are there people out there who don't geek out over stuff like this? Weirdos...

Apparently there are others outside the realm of FIRST that geek out about this too.

http://jalopnik.com/5302043/on-the-power-of-transmissions

"Artist Arthur Ganson's creation called "Machine with Concrete" provides a beautiful illustration of the power of a transmission. Should you input only 1 lb-ft of torque, the other end could deliver 244 quintillion lb-ft.

Ganson's piece demonstrates the unbelievable power which can be generated through simple gear reduction. It uses an electric motor turning at a modest 200 RPM and mates it to 12 identical sets of 1/50th gear reducers for a total reduction of 1/244,140,625,000,000,000,000. Of course no material in the universe could actually deliver that kind of power without shattering into pieces and even if such materials existed, turning only one rotation at that speed would take over two trillion years. It turns so slowly that embedding the final drive in concrete will have no appreciable effect — ever. The universe itself is only about 10 billion years old, and in another 10 billion years the sun will expand into a red giant and consume the Earth anyway, the final drive having complete only 0.5% of one rotation."

My emphasis added to my favorite part.