30-07-2013 16:40

magnets

Re: pic: offseason Wheel cage and pivot desgin

Nice design!

Just a few questions/comments:

What sort of belts are you using for drive?
What sort of bearings/bushings are being used for the wheel cage rotation, and how far apart are they on the tube?
In the wheel cage, the upper shaft has no bearing. How does this work?
What diameter shaft are you using in the wheel cage?
The top of the module looks really really thin/too weak, you may want to consider making it stronger. If you don't know how thick/wide to make your plates, you can look at 1640's swerve here, which has a similar wheel cage design.
Also you need to fillet all the right angles, as it makes it considerably stronger/easier to machine.
How are you planning to machine this, out of a solid block of aluminum? (If so, I would recommend a design like this.)

My biggest concern is the sides of the module getting bent, so I would recommend making that connection stronger, as well as putting some sort of brace on the front/back like 1640 has.

31-07-2013 10:33

Jay Burnett

Re: pic: offseason Wheel cage and pivot desgin

The drive belts are 3/8 wide, and the steering belt is 1" wide

There is a lazy susan bearing on top of the pivot cage and a flanged 1/2 diam bearing directly above that.

There is a bearing there, the photo just isn't hi-res enough to see it

It is a 1/4 in shaft that thickens to 1/2 half in the middle to help retain the gears.

Thanks for the feedback, Magnets. I have looked at 1640's website and i think the sides of my pivot cage are a bit thicker than theirs, but I will thicken the top. I would like to try makinging the cage out of one piece on a bending machine, but I don't know if aluminum will be strong enough to take the sideways force.

31-07-2013 12:10

magnets

Re: pic: offseason Wheel cage and pivot desgin

I'm not sure that the 3/8" belt is strong enough to power the drive, and I would also stay away from the lazy susan bearing. The lazy susan is able to withstand the thrust loading, but it will have trouble when there is any amount of side load. I would recommend putting another bearing for the module rotation above the steering pulley. Also, I can't tell what sort of bearing you're using for the shaft with the miter gears, but it should probably be a thrust bearing because the miter gears will try to move away from each other.

While it probably is possible to make this module out of a bent sheet of aluminum, I would recommend against it, as it will make the corner too thin.
It would be easier to make the top plate a separate part, then put some holes in the side, and bolt the side plates on. I know that 1640 did this, as well as 118 in in 08.

Another question, how does the tube that sticks out of the top plate get held on? Is it welded, or is it something else?

31-07-2013 15:45

DampRobot

Re: pic: offseason Wheel cage and pivot desgin

I'd look into GT2 or HTD profile belts instead of the ones you have now. If you do use the trapezoidal profile belt, I think you'll be unpleasantly surprised by ratcheting.

01-08-2013 23:45

cadandcookies

Re: pic: offseason Wheel cage and pivot desgin

We used 9mm belt (~.35") on our robot this year. Provided you're getting a decent belt, it would probably be fine. I would think ratcheting would be a bigger concern with that tooth profile (as Damprobot mentioned). It does strike me as a little bit odd that the rotation belt is larger than the drive belt (not sure about actual performance, but it looks weird to me).