Stair Climbing, Tracks and how well they work on carpet!

I am designing a robot that will be able to climb stairs in a similar method to a packBot.

However it is designed exclisvly for indoor use, which means carpets!

From my reasearch the basic impression i get is that i need smooth tracks with not much friction to be able to turn effectivly while on the flat. However when it comes to being able to climb stairs i will need tracks with large treads. Obviously two ends of the spectrum so somehow i need to find a balance!

I can't find any documented information about the use of tracks on carpet so i wondered if anyone here has any insights about the trade off, design tips stories from experience etc. I would also apreciate the same about stair climbing in general.

As it is likey to be suggested, due to other design contraints no i can't use a different method of climbing stairs. ;)

Also if anyone knows of a good supplier of tracks or a way to make tracks that are thin, about 25mm wide and not very bulky let me know!


** Having tread on your**


Having tread on your tracks doesn’t necessarily mean there will be high friction when you turn. It depends on the design of the treads. If the treads run from side to side of the robot



(like the packbot does) there won’t be much friction at all. But if the treads run from front to back there will be a lot of friction. This is due to the fact that when the robot is turning, every point on the track is sliding to one side or another. 


Also, you want the profile of the treads to be trapezoidal, not rectangular. This will prevent the edges of your treads from snaging the carpet when it is sliding. 

Here's a bad pic of what I'm talking about (top right corner): 

As for how to make them, a lot of people use those roller chain some way or another:

I've built tracks using these before and they work great (a little expensive though): 

(McMaster-Carr part number 7321K7)

Hope that helps some (I did my Thesis on kinematics of tracked robots). 

Thats really helpful,

Thats really helpful, thanks!

I didnt notice these replies when i was doing the project (a summer placement at university) but now im continuing it for my dissertation project. So is there any way i can read your thesis, has it been published? It would be perfect for the literature review i need to do.

If anyone knows where to source these kind of tracks that would be really helpful! I need to use continuous rubber ones rather than ones in sections due to the fact it will have very small drive wheels (its designed to be super thin!)