pic: Coaxial Crab
 

Re: pic: Coaxial Crab
 

That's pretty amazing.

How hard would it be to change the gearbox? Is there a reason it's not a shifter?

What needs to be CNCd?

Re: pic: Coaxial Crab
 

i was wondering, why don't you support the bottom of the module at all? a. you wouldn't need the two .5"thick plates and b. it'd probably be even lighter. but its only 40 lbs right now which is more than i can say for our 60lb one (it'll be lighter next year)
one last question how many swerve drives do you currently have designed?

Re: pic: Coaxial Crab
 

A shifter is easily possible, I just haven't added one in. In order to change a gearbox, you only need to undo 4 bolts. In order to save weight and structure, the gearbox bolts also mount the modules.

The only CNC necessary parts are the side plates of the actual modules.

It's actually a single block, not two plates. I just chopped the middle out to save weight. We've built a crab with a mounting system just like this, and never had any issues.

I think I'm up to like 8 different ones designed... this is by far the lightest and best.

Re: pic: Coaxial Crab
 

...

Re: pic: Coaxial Crab
 

What can I say? I'm obsessed... and my team still won't let me build one of these...

Re: pic: Coaxial Crab
 

Sorry, that was just a placeholder for CD-Media apparently not allowing you to delete your own posts. Not a question of why :)

Re: pic: Coaxial Crab
 

Your CAD work still amazes me. Eight different designs?? What's next?!? Keep up the good work, and maybe you can bring one of those digital files to life one day!

Re: pic: Coaxial Crab
 

jesus christ we are twins I swear to god. I have pretty much the EXACT same design. wow.. yours is much better drawn of course ( I am still learning AutoDesk) But man we think a like for sure.

Re: pic: Coaxial Crab
 

Our team is interested in doing a Crab drive similar to yours this year. We were wondering if by any chance you could send us those files for us to look at them.
Thanks,
Miriah Team 1710

email (miriah27@sbcglobal.net)

Re: pic: Coaxial Crab
 

Wow! That's epic. I like your mounting system. How do you plan to tension your chains, though? Are you going to try the Robonauts free-floating sprockets, or will you try some sort of spring-loaded idler?

Re: pic: Coaxial Crab
 

this is like my FTC bot this year except only 2 'swerves' so really its only half that
and unfortunatly it cant go 8fps, maybe about 2fps

Re: pic: Coaxial Crab
 

There looks to be a plastic rod near the globe motor, that would probably tension the steering chain. I can't see anything in the picture to tension the drive chain though. It's entirely possible he designed the distance to be exact so that no tensioner is needed.

Re: pic: Coaxial Crab
 

Hah. I did the math for one of those once, and I'm never doing it again. Besides, chain stresses. Especially under high stress apps like this.

The tensioning method is the Delrin rods, like AdamHeard said. They're off center, kinda CAM ish. One will be a through bolt, to act as a pivot point. The CAM would be rotated to hold the chain tense, then a second hole would be drilled to lock it in place. If the chain stretches to an unhappy amount over time, a new piece of delrin (which is surprisingly cheap...) would be drilled and attached.

I'm sorry, but I don't really hand out CAD to something this complex. It's a much better process if teams learn how to design themselves. However, I'd love to answer any questions you folks might have. Feel free to shoot me PMs whenever you'd like, and I'll work to get back to you as soon as possible.

I'm glad people still like my designs!

Re: pic: Coaxial Crab
 

Sorry, We don't need CAD help that is not one of our weakness's. We are just having trouble with the drive assembly for our swerve prototype. Some shop drawings would be nice at least, someone with inventor knowledge like yourself should be able to whip a few of those up in minutes with auto-dimension. Let me know what you can do to help!

-Spenser
FRC1710