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Tread Chassis Design Question

Alright, so I am new to robotics as well as this site, but here is a question I feel I have to ask.  I need to ask because it will effect a future project I want to do when I am more experienced in Robotics.


Alright, so the theory behind this question has entirely to do with ground clearance with a treaded chassis.  I notice that every bot with treads has very little ground clearance, and was wondering if there wasn't another way to do the chassis so you could increase the clearance and what kind of effect it would have on terrain options.


So, for reference I have a few pics of sketches.  Please ignore my horrible drawing ability, as well as the pictures, as I took them with a digital camera at my desk, instead of using my scanner.


Image #1: Traditional Style (insofar as I have seen)

Image #2: My Design


Basically, the black lines are obviously the wheels and tread, and red is the chassis/frame for the bot.  You can see in the second how it has raised the clearance by quite a bit.  In the picture I used solid frames extending down to the lower wheels, but as I sit here, I am already thinking of how you could implement a shock absorption system to further enable rough terrain durability.


Basically, I just wanted to get some feedback to see if my idea is crazy, or if I am.



Edit: Thinking along another thought path (which I am prone to do) I came up with the idea of 4 treads on a bot (which I am sure isn't a new one) and was curious as to if there is a reason for not doing it, or does it just present to many problems?  Image #3 is what I came up with.

Image #1150.79 KB
Image #2160.4 KB
Image #3154.92 KB

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This site is probably informative: http://www.rctankcombat.com/articles/

What I gather from the pictures is that ground clearance is defined by the diameter of the wheels that carry the weight of the vehicle. The big ones in the middle of the track. Most LMR robots are too small to even have those wheels. So they only have the drive wheel and a free wheel (idler pulley). Just like this little wooden design: http://woodgears.ca/tracked_vehicle/index.html.

In your second image, you solve the problem by mounting the wheels on legs. But the wheels are very small (in comparison to the body). That vehicle will not be able to climb an obstacle like a threshold in the doorway. Place the lower two wheel closer together, like a tank has them. The front and back of the track now is diagonal and it will climb up and over any obstacle.

in ascii art:




BTW: I love the whyteboard/digicam design sharing technique!