pic: 4 Wheel Strafing Chassis
 

Re: pic: 4 Wheel Strafing Chassis
 

As promised, here are the zip files with additional jpegs. They needed to be shrunk to make the file size limitations.
PM me if you want any closeups.

Re: pic: 4 Wheel Strafing Chassis
 

Looks good. I'm just curious, why did you go with sprockets as opposed to gears?

Re: pic: 4 Wheel Strafing Chassis
 

Looks great! One quick question though. Do all four wheels turn or only the wheels on the side of the steering assembly?

Re: pic: 4 Wheel Strafing Chassis
 

And to amend to that question, why was that decided upon?

Re: pic: 4 Wheel Strafing Chassis
 

I choose sprockets were used for a couple reasons. There was quite a debate among team members regarding this. I am not the head designer for my team. This was something I worked on my own. It was my opinion that sprockets were the way to go for these reasons:
1. cheaper
2. allows for more flexibility for choosing distances while maintaining gear ratio's
3. requires less precision in holding tolerances when machining side plates.
4. Allows for a change of gear ratio's easily.

5. just as efficient as gears if chain is correctly tensioned.
(I calculated the center distances with Matt Adams sprocket center distance calculator. Thanks Matt)

All 4 wheels turn together, and steering is tank style. Its simpler than having paired wheels for steering, or 4 wheel independent, especially since we don't get 2 globes in the kit anymore, or 2 of any appropriate motor for that matter.

OT: center distance calculator
 

off topic, but...
link to M.A. center distance calc.
i felt obligated to post a link to the calculator for those who missed it the first time (or weren't around). its really an invaluable tool, and has saved me some work and frustration.

<edit> FYI, it runs in excel </edit>

Re: pic: 4 Wheel Strafing Chassis
 

It looks like you have all the bases covered. I would look at the upper bearing being a little larger in diameter with a central hole for wiring big enough so as to allow power and control wiring. The lower bearing/followers are a good idea too. Remember though that using the chain and sprocket design raises the steering power demand and allows for objects to block the turning if they get caught between the outside of the wheel module and the robot frame. Tank steering is OK for changing orientation but is not need for normal driving. As always (after it is built) practice, practice, practice.
Good luck!

Re: pic: 4 Wheel Strafing Chassis
 

I am looking to purchase a 4 wheel 'crab' or strafing chassis for use on a powered chair project. Can I purchase your design or can you build one for me?

Re: pic: 4 Wheel Strafing Chassis
 

Holy Thread Revival!

You may be interested in http://www.chiefdelphi.com/forums/sh...ad.php?t=77623 You might not get many results when asking in this thread because it is quite old, but who knows.