designing a better kit frame.

[jspatz1]

Very cool idea.

No, you can't fabricate before build season begins. Making the design open source allows you to utilize a design that was worked on before build, but not fabricate it.

[Tristan Lall]

Given you mentioned fabricating it in the preseason, can I assume that this is something you'd like to see mass-produced and made available to teams through retail or KOP channels (e.g. as a future kit frame)? (If you're only planning to build them for your own team's consumption, then this advice may not apply.)

It's a neat idea, and it's got great potential for modularity. I think that you're looking at a lot of cost in fabricating it, relative to a kitbot.

The huge advantage of the last two kit frames was the ability to punch and bend them using sheet metal equipment. The raw material is relatively cheap, and provided you're sourcing them from a shop with significant investments in turret punches and brake presses, they're reasonably cheap to fabricate in mass production quantities too.

The problem with this design is the need for a lot of CNC setups to drill all four faces individually. (Well, you could do it manually, but that's obviously a ton of work; not a production solution unless you can get the cost of labour way down.) So for mass production on the scale of a kitbot, I would encourage you to think of other ways that a roughly equivalent part could be made. Maybe you could get away with C-channel made from punched and bent sheet metal (like the old kit frames, but a larger section). It wouldn't be difficult to rivet in a few smaller stiffening braces on the open side to carry the inner bearings, for example.

The universal mounting for the bearings is nice. But as you're CNCing them anyway, maybe you'd want to consider some more hole locations for intermediate settings. That way you could be a bit more flexible in using them as tensioners. Or if you want to get a little crazy, make them in two pieces: one sets the ground clearance for raised or lowered wheels, and the other one has some sort of pattern that allows you to rivet the wheels in place in a couple positions, e.g. on centre, or plus or minus 0.125 in to compensate for chain centre distance.

[Hawiian Cadder]

while this may not be massed produced, after our 2012 season, i will probably write a full paper, cad a sheet metal version, and submit it to Andy-Mark. you are correct that this frame has a TON of CnC work. however, the frame and gussets themselves only weigh 8.3 lbs, which of the amount of strength this frame would have, extremely light. the other advantage, is that even if we are unable to pre-fabricate the pieces, they can be fabricated durring the finalization of the design, and the CAD. which will still cut a 4-6 days off our build season.

while the 3*1.5 tube in this version dissalows more than 4, 6 at maximum different axle positions, the previous version used 4*2 tubing, and each wheel had 12 different positions. the 3*1.5 tube saves 4-5 lbs over the robot, but does make it a tiny bit less flexible. a sheet metal version could probably accommodate a larger number of axle positions.

[Chris is me]

What are the flaws of the current kit frame?

Have you ever had aluminum tubing bend because you directly mounted a bearing in it? I've never seen that problem before. Why not just punch bearing holes in the tube?

[Hawiian Cadder]

Originally Posted by Chris is me

What are the flaws of the current kit frame?

Have you ever had aluminum tubing bend because you directly mounted a bearing in it? I've never seen that problem before. Why not just punch bearing holes in the tube?

the primary advantage that this has over the kit frame is how adaptable it is, it can support more wheels, more gearboxes, and more manipulators Nativity. the kit frame also weighs more, i don't know exactly how much it weighs, but our cart, which is a kit frame, weights i would guess upwards of 20 lbs, this weighs less than half as much. the kit frame also suffers from rigidity issues, because this uses much larger members, it should hold its shape better, this should prevent the drive train from throwing chains. my last complaint about all of the rapid build options available (kit frame, 80-20) is that they don't tend to stay exactly square. the aggressively sized gussets on this frame should keep it perfectly square, no matter what abuse it takes. i don't dislike the current kit, it just is not quite adequate in my oppinion in terms of flexibility and strength/weight (for the weight of the kit-frame, something much much stronger can be built). That is part of the reason that the holes on this match the ones on the kit, they can be used in tandem.


the reason to use the pockets and bearing blocks is 2 fold

1, the pockets make it much, much, much lighter

2, we like to use dead axles for the outer most wheels, and live axles for the middle two. a bearing hole would not deform the frame, but a .5 inch axle hole would be pretty sketchy.

[Jared Russell]

Cool idea. Very similar to some ideas that I had been meditating on. For bonus points, you could make sure the axles are spaced properly for an integer number of #25 or #35 chain links. Also be sure to offer a bearing block with a dropped center for anyone who wants to do 6/8WD.

Given the number of teams that used AndyMark Nanotubes this year, I would bet that a solid implementation of this would see plenty of interest from teams.

[Hawiian Cadder]

Originally Posted by Jared341

Cool idea. Very similar to some ideas that I had been meditating on. For bonus points, you could make sure the axles are spaced properly for an integer number of #25 or #35 chain links. Also be sure to offer a bearing block with a dropped center for anyone who wants to do 6/8WD.

Given the number of teams that used AndyMark Nanotubes this year, I would bet that a solid implementation of this would see plenty of interest from teams.

the bearing blocks have the bearing / axle hole off center by 1/16 of an inch in bot the x and y direction, so dropping wheels is just a matter of the orientation that you put the bearing block in. the axles are set up for an integral number of #25 chain, no matter what wheel placement you use. you can use #35 chain, however you are restricted in which holes you can use. i believe #35 chain requires a wheel every 3rd hole, while #25 chain can be run to every hole. i will probably work on making a plate that will adapt any andymark gearbox to this frame.