Let's Make Robots!

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.

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robologist's picture

Small Mattracks from Radio Shack used on a robot :

http://www.youtube.com/watch?v=R5K0gVGb-LI

Chainer's picture
Very close to what I was envisioning, very close indeed.
voodoobot's picture
I'd seen some on ebay before, but they are becoming hard to find.....
robologist's picture

Order direct from Radio Shack, an old quote :

"The Mattracks are available with the wheel. Your local RadioShack store can order them for you. Catalog numbers are Left/ RSU 12458907 $11.69 & Right/RSU 12458923 $11.69."
 

voodoobot's picture

here are a couple that I had been thinking of...most are 3 angle, but tere are some others....they are just rough sketches...

 

tracks_sketch_small.jpg

Chainer's picture
Hmm...still not quite what I was thinking...I will attempt to build a mockup over the next few days to show you guys.
voodoobot's picture

I thought I replied to this one, but apparently I didn' submit it this morning

http://letsmakerobots.com/node/2154

This is a good design as it uses the three sprockets, with the upper one being the drive gear giving quite a bit of clearance depending on how the motor is actually mounted. This also has the drive gear slightly forward which helps with keeping the center of gravity pretty close to the center and low.   Hootyhoo's suggestion would also help giving additional clearance with mounting the sprocket/wheels on pegs/standoffs.

 

Chainer's picture

It appears my reply got gobbled up in the changeover, alas woe is me, etc etc.

 

But thanks for the helpful tips guys, I am starting to redo my idea in my head, and hopefully it flows out into at least a drawing soon.

Also, the "Witeboard" is really just printer paper with sharpies, though now I want to get a white board and expo markers to cut down on buying paper.

Excuse the dots on the ASCII pic but it kept left justifying the bottom part of the treads :)

Instead of using axles for the wheels try mounting the wheels on a standoff with an OD less than the ID of your wheel (you could also find a metal bar of the right diameter cut it to length and drill/thread it but that's a bit beyond most of us). Then you won't have any bars going from one side to the other. With the use of a sprocket and chain setup to drive the wheels you can create as much ground clearance as you want and still keep the classic \O^^^^^^O/ look to your treads.

..........................................................................\O___O/

The_keyword recently did something similar to this. Check out the video on this page and this picture. If he had opted for a chain drive setup instead of a direct drive (mount motors to wheel) setup he could have increased the ground clearance as much as he wanted (until that plastic sheet began to bend due to the laws of physics and leverage). You can do the same thing with the Tamiya trackset and get that classic tread look, just throw away the axles that come with it and use the standoffs.

 

NOTE: Using a bearing would be much better than placing the wheel straight on the axle but alas finding them can be hard and expensive. Just make sure you grease the standoffs (or whatever you use) and the wheel to cut down on friction. It shouldn't be a problem on small scale projects like most of us are building.