Gearbox incorporated into frame.

[Ken Patton]

Sanddrag-

We have done this since 2001. We started out with 1/4" plate on the outside, 1/8" plate on the inside, and a 3rd small 1/8" plate for a bearing support.

Over time this has evolved to two plates, 3/16" and 1/8".

I uploaded a picture of our 2003 robot (actually its the "mutt" made from spare pieces) to the CD picture gallery, year 2003, section "robots."

Advantages:
1. The two sides can be identical, so machining multiple pieces is easy.
2. You can put extra motor mount holes in the inner plates to be ready for a motor swap with different gear sizes (say FIRST decides to replace the F-P motor halfway through the season... never know it might happen).
2.5 If you pay attention, you can make access holes to do very quick motor swaps when those F-P's start to fry.
3. Stiff as all get-out. Don't get carried away though or it will be heavy as all get-out. With stiffness comes well-supported shafts, which leads to low friction.
4. Frame x-members can be very lightweight aluminum or steel thinwall tubing with welded flanges on the end. We use 1" OD 0.065" wall chrome-moly.
5. Can machine cool designs into the sides - 7075 aluminum works best for both machining an polishing, but get out your wallet. We typically use 2024 or 6061.
6. Good mounting surfaces for components - eliminates the added mass of a lot of brackets. We often "trampoline" control boards off the tubular x-members.
7. Very little welding required (we weld simple flanges on end of x-members).
8. East to assemble - disassemble.

Caveats:
1. Think ahead of time where you want to put x-members - pay attention to torsional stiffness when you place them.
2. It is easy to make the plates bigger than they need to be, which means you might carry around too much weight.
3. If you want to mount a horizontal platform (say for a turret) you have to think ahead about how it will get securely mounted to the frame. If possible use the mountings for your appendage(s) as x-member(s).
4. We always seem to have trouble with bumpers - think about what you put in the front and rear center of the bot (where there are no plates) cuz it will get banged up.
5. Mounting things to the tubular x-members can sometimes be a pain.

hth,
Ken