Let's Make Robots!

Large Tracked Robot

Runs over stuff, should be very snow capable, as well as most other land terrains.

Another new video 3/4/12.  I got it all together and it WORKS.  I think it did pretty good, many changes to come.

Added another video of me trying to pull myself on a snow sled, even though there isn't any snow :)  it drained the battery at an alarming rate, I'm changing to 10:1 gear ratio and gonna have to increase voltage to maintain some speed.  5:1 gear ratio is fine if I don't want to pull anything, but I want it to have a little more grunt.

This is a work in progress ATM, my major obstacle is coming up with my own tracked driving system, including every aspect of the track drive system (except making the tracks, they are youth snowmobile tracks). I've been through several prototypes to get to the point now, and actually am changing the drive system again. It buckled under the track tensioning system, so i'm changing it again, actually going back to an older model with some new ideas.

Everything is geared to go 16mph, however I have no idea if i'ts really going to do this or not. I did have a unit assembled, and tested powering it downstairs, i think one track output about 40lbs of pushing force at stall. However I used my hand as a gauge, so 40lbs is just a guess. There will be 2 tracks, so double that power. Granted I don't know how this will translate to real world performance, but at least it has what seems to be a decent amount of power.

The gearbox I used can be switched out for many different ratios, 10:1, 20:1, 40:1, 50:1, and 60:1 are available, so if the rest of the design works, changing gear ratios won't be that big of a deal, and overall won't be that costly either. I have a feeling i may have to goto 10:1 (cutting my speed in half) to get the power I really want.

Here is a shot of the internal track drive system:

Internal shot of track driver system

Top mockup view:

Top mockup view

 

 

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They are youth snowmobile tracks, here is the ebay auction i got em from:

http://www.ebay.com/itm/110790649945

I looked at all the other track system available, from other robot shop websites, and really they weren't much more then a double sided timing belt most of the time.  Some have a small amount of treads, but snowmobile tracks have real treads, also the rubber is like a quarter inch thick, granted they all have steel bands under the rubber.  Plus the widest tracks I saw from other places was 4" wide, these youth tracks are 10 inch wide.

Here's a pic of just the motor and gearbox:

I got it from surpluscenter, https://www.surpluscenter.com/Item.asp?item=13-175-5-DE-56C

I've used many of the other similiar type gearboxes from there, this is the lowest ratio i've ever used, i have some 50:1's and others for slower applications.  Overall they are great gearboxes, and their specs are severely underrated.  The rpm's are really low as well, since they are all designed for an input speed of 1725rpm, which is a common industrial AC motor rpm.  I've done testing over double that, and they are fine.  Really, all these gearboxes are, is a worm gear, and the entire thing is filled with oil, with nice load rated bearings.  They are heavy however, but that's a good thing for this specific application.  I think it could take a small caliber gunshot and be alright.

The NPC black motor is a good match, it's 5/8" shaft and high power are not that common in it's power range.  I couldn't find a cheaper motor with enough power and the shaft size.  You can always get shaft input ones, but you have to make a much more involved mount, at least I think so, plus coupler cost more money.

Ross

 

Can you post some specs on the motor/gearbox combos?