pic: GUS Team 228's Prototype Sheet Metal 6WD Chassis

[artdutra04]

Originally Posted by Rob Stehlik

How much ground clearance is there?

About an inch; I don't have the exact number, as the files are on another computer at the moment.

But depending on the game, this number can easily be increased. One design we drew up (only drew a 2D side sketch of a chassis rail) had angled bottoms and could clear a 30-degree ramp.

Originally Posted by Rob Stehlik

If the game calls for an open front, do you have a plan for joining the frame members mid way?

The same way we did on our 2009 robot: use short end rails and an inner chassis rail further into the chassis.

Originally Posted by Rob Stehlik

For the mounting hole pattern on the frame, I'm wondering if you could make them all 1/4" holes. This would allow you to choose either 1/4-20 fasteners, or #10-24, since 1/4" is the drill size required for #10-24 PEM nuts. So if you have a spot where you want to use # 10 screws, just put in a PEM nut.

We hardly ever use 1/4-20 bolts on our FRC robots anymore as #8 or #10 screws work just as well in FRC, but at a fraction of the weight. A #10-32 screw weighs 58% of the same length 1/4-20. By modifying our hole pattern to accept either #10 bolts or 5/32 rivets, we can choose whatever fastener will work better for a particular application.

We also chose #10-32 over #10-24 for two reasons: 1) #10-32 are the screws needed to mount the CIM motor, so we might as well stick to one or the other (nothing is more annoying than picking up a #10 nylock nut and realizing it's the wrong pitch), and 2) the ratio of shank size to pitch of #10-24 screws often causes them to be the second most broken tap at machine shops (#6-32 is the worst).

Originally Posted by Rob Stehlik

I like the way you have designed in a series of holes to allow repositioning of the standoffs to serve double duty as chain tensioners. This is much more reliable than using slots to reposition a tensioner. Do you know how much excess chain length would be taken up for each position of the standoff?

It would vary for each standoff, so we didn't calculate it. We did calculate the chain length and design for an exact number of 146 25p links, so any tensioners would depend on how much it stretches.

Plus, we also have a habit of adding in a lot more mounting holes than most parts need. Often times we've found that these extra holes help us out in a pinch when we need to mount a Lexan panel or zip tie wiring to.