pic: 1683 Concept 8 Wheel Drive

[sdcantrell56]

8 wheel drive can be very maneuverable if the middle 4 wheels are dropped. For instance I have them dropped 1/8" which is the same drop that we have on our 6 wheel drive robots creating a rocking effect and eliminating scrub steer. Polish I do agree we could always have more wheels. Actually my brother is pushing for 10 wheels so that one can be lowered in the center. I did see your robot at the championship and that takes it to the max. I wish we could do something like that however I don't know how much more it would help us and we do not know how to properly tolerance for a gear drive like that. I also forgot my whole reasoning for having the braces offset into the frame. If you notice the front and back of the side plates are angled to provide clearance for climbing any ramp. In order to put channel on the front I would have to get rid of the slope unless there is some other way that I am missing

[MrForbes]

You might want to consider making the drivetrain side plates taller, so they extend past the top of the wheels, then it would be a bit easier to mount the front and rear end pieces up high enough that they are in the bumper zone (over 2.5" off the floor). Although with the small diameter wheels, this might not work too well.

Using 6" wheels, axle near the bottom of the side plates, and 4" tall side plates, seems to work out well for using bumpers, also it keeps the wheels from being in the way of whatever gets mounted to the top of the chassis.

[sdcantrell56]

I actually have made a new version that incorporates the transmission into the side plate to help with mounting. As for using bigger wheels, I am trying to use as small as possible wheels because of the weight savings of the actual wheels as well as smaller sprockets to achieve the same rpm. Additionally if we are going to be custom making the wheels the smaller size costs less in raw material, as well as the smaller side plates cost less

[MrForbes]

Something you might want to consider is that if there is to be weight on the robot, you want it as low as possible....so having a heavy chassis and heavy wheels may be a good thing, not a bad thing. It forces you to keep weight off the top of the robot--the result is that your robot will spend it's life upright, on it's wheels, rather than falling over and laying immobile on it's side.

[sdcantrell56]

I know that low weight is good however, as is this frame is not going to be overly light considering that there are 8 wheels and all of the chain and such associated with that. This year our drivetrain weighed 75 lbs and we are trying to cut that down considerably without losing too much strength. With our current drivetrain we were never out-pushed so I am using that as a basis to work off of. Also I think it is better to be underweight and be able to strap on ballast than be too heavy and forced to cut weight. I have posted a new version of this drivetrain http://www.chiefdelphi.com/media/photos/28328

[sdcantrell56]

Here is an even more updated one I made the plates one inch taller and moved the braces flush with the front and back. I still have not decided what other braces to have on the inner frame. http://www.chiefdelphi.com/media/photos/28331?

[POLISH703]

Originally Posted by sdcantrell56

8 wheel drive can be very maneuverable if the middle 4 wheels are dropped. For instance I have them dropped 1/8" which is the same drop that we have on our 6 wheel drive robots creating a rocking effect and eliminating scrub steer. Polish I do agree we could always have more wheels. Actually my brother is pushing for 10 wheels so that one can be lowered in the center. I did see your robot at the championship and that takes it to the max. I wish we could do something like that however I don't know how much more it would help us and we do not know how to properly tolerance for a gear drive like that. I also forgot my whole reasoning for having the braces offset into the frame. If you notice the front and back of the side plates are angled to provide clearance for climbing any ramp. In order to put channel on the front I would have to get rid of the slope unless there is some other way that I am missing

The 14 wheeler is an extreme but it works for us. Something that we did that may work for you is rather then offsetting the middle wheel 1/8" (or wheels) is off setting all the wheels on an arc. On my robot, we set the axis of the wheels on a radius of a 38 foot arc.

On another thing. Orginally our gearbox was also intregrated to be a part of side panels, later we found out it was pain when we had to make a fix to the gear box. This year, we made the entire gearbox modulur. All we do is pull off 4 bolts and unwire the motors and the whole gearbox comes out.

[sdcantrell56]

That arc idea sounds interesting however with only 8 wheels I think setting them on an arc would be the same as lowering the 4 middle wheels. Also about integrating the transmission into the side plates, I posted some pictures of what im talking about and they would also come off with 4 bolts. I greatly appreciate your ideas though as I really love your robot.