Large Tracked Robot

Let's Make Robots Robots
1

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

 

 

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

  • Actuators / output devices: NPC Black Motors with a 5:1 gearbox to a 10 inch wheel.
  • Control method: android phone/tablet via wifi
  • CPU: Beagleboard XM
  • Operating system: Linux
  • Power source: 2x12v lead acid, possible conversion to lipo in future
  • Programming language: C++
  • Sensors / input devices: Current sensors, voltage sensors
  • Target environment: outdoor ground
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/large-tracked-robot
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Here’s a pic of just the

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

IMG_20120128_135934.jpg

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

 

3

Where did you get a hold of

Where did you get a hold of those nice tracks?

4

That looks like it is going

That looks like it is going to be one heck of a platform. Thanks so much for sharing; I’ll be watching with interest.

5

looks great cant wait to see

looks great cant wait to see it run from phone

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They are youth snowmobile

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.

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Cost to build: $0Can you

 

Cost to build: 
$0
Can you send couples of those where you have them for 0USD? :smiley:
Seriosly though very nice tracks! What Amp draw do you have at 16V and what amp draw when stalled?

 

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Unfortunately I haven’t been

Unfortunately I haven’t been recording the amp draw during any of my tests, although I have a certain idea based upon battery draining characteristics and also I know under what loads the Roboteq controllers start to scale back.  That said, at 16 volt probably around 50-75 amp (per side) to get going, then really if it’s going straight probaly around 30-40 amps per side at higher speeds.  Turning is the real killer on this, I knew it wouldn’t skidsteer like turn, but if you attempt to, it pulls hundreds of amps trying.  On some surfaces it can.  I planned to make the software not even attempt skidsteering, I was gonna make a mode on the android app called “skid-less-steering”, which is a horrible name, but it just means that it would drive more like a car, where you only turn while moving forward or backwards.  It’s more efficient.

I am working on the software to send the amp currents to my phone so I can see as i’m running.  Once I know i’ll post some current data.  

Thanks

9

check this

check this out

http://www.youtube.com/watch?v=F6sowsDK5ac&feature=related

i came accross it looking up Sabertooth dual 25A motor driver

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Yes I have seen that, it’s

Yes I have seen that, it’s very cool I must say.  I actually have always wanted to make a motorized dolley for my boat, i came across it while searching for that.  I looked into buying it, but it costs $1450, so i quickly decided against that. 

I wish I could just get their tracks and drive wheels to make my own smaller robot.  That would be a great size for a tracked robot in the house.

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Track drive wheels

Did yo make the drive wheels or buy them somewhere online?

 

Sick robot BTW!

12

The tracked bot is burly,

The tracked bot is burly, nice work!

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Hey man that’s impressive!

Hey man that’s impressive!

14

cogs

where did you get the cogs or wheells for the tracks to run on?