how to attach a carrier plate for a turret arm to the robot.

[vivek16]

well i have been designing a new robot for fun after season. and here is what i have so far:
-mecanum drive train- completely done- places to get the parts listed.

-bionic arm controller- working on it...

-arm- carriet plate+mast+joint+extended peice+joint+another peice that can extend using a pneumatic piston+joint+ claw.

i have been working on the arm recently and having trouble with how the turret is going to work.

i would like to figure out how to mount the carrier plate onto the top of the robot with it still being able to move around freely. i know that i want to use a 72 tooth IFI mechanism sprocket. and i can attach the bearing retainer to the sprocket and put the bearing in like that.

but how would i mount the bearing so it would still spin freely but be securely mounted?



this might be something to look at...

[MrForbes]

You haven't given us a lot to go on here, could you maybe draw a sketch of what the robot is going to look like? ie how high the turret mount is, what the arm is that will extend from it (length, approx weight, materials), etc.

I assume you are planning on using the small 1/2" diameter bearing that fits into the IFI sprocket....if so, you probably need to use two of them to get the support you will need.

This is a tough design problem!

[vivek16]

ok i attached a sketch to my original post. the mast part is going to be two 3' long peices of aluminum tubing (1.5x1.5x1/16). the next part is going to be two peices of 1x1x1/16 peices of aluminum tubing. the next part is going to be a pneumatic piston and four peices of aluminum tubing that can slide within each other. and the claw is going to have four fingers and be a pincher like thing.

i approximate the overall weight of the arm to be around 15-20 pounds.

thanks.

and i was planning on having some sort of supports underneath the sprocket like plastic blocks or something low friction. (i like the ball transfer but i dont want to steal anyones ideas and i thing i could much better support it with some sort of roller system)

and only the 3/8 bearing retainers work for this size sprocket.

[MrForbes]

I doubt a 3/8" bearing, or even two of them, could do what you want...the load at the turret is going to be very high, because of the length of the arm and the weight. You might see if you can use a "lazy susan" type bearing under the sprocket, and maybe a 3/8" bolt going thru the bearing in the center to hold it down to the robot frame.

Even this is probably going to be kind of weak for what you want to do.

[vivek16]

hmm, ok thanks.

maybe home depot will have some lazy susan type bearings. that seems like the easiest option.

thanks, vivek

[vivek16]

what if i used ball transfers on the top of the sprocket to distribute some of the stress there?

thanks

[Joe Ross]

FIRST Robots: Behind the Design features several teams with turrets with a lot of pictures and descriptions of how they designed and built them.

http://www.amazon.com/FIRST-Robots-H...6089718&sr=8-1

[EllieJ]

i have seen a lot of turrets types that don't really function that well. You have to make sure you get the right balance of stability and manueverability.
If it does fit into that small goal, then they usually work fairly well.
Good Luck!

[Cptn Patches537]

We used a turret for our arm this year, and it is fairly similar to what you want to do except that you have one more joint thrown in there. Our turreted design has the carrier plate flush with the top of the chassis. A steel shaft runs through 2 bearings down to a pulley which is connected via timing belt to the nippo denso motor. The 2 bearings are about 8 inches apart, and the steel shaft gives us excellent stability. Our turreted arm has worked amazingly, giving us a clear advantage when people try to play defense against us. See us in action here:
http://www.youtube.com/watch?v=ydGq45HHCuM
All our primary driver has to do is move back and forth.
If you would like more detailed drawings post and i will try to find them for you.
-Eric

[fimmel]

McMaster sells them
http://www.mcmaster.com/nav/enter.asp?pagenum=1068

page 1068
not to price either imo

/forest

[mikeleslie]

We have used a 360 deg rotation turret for the last 2 years. We have used a very large "ring" and 4 bearing blocks. the blocks clamp the ring in place. THis years ring was 24 inches in diamater. The larger it gets, the lower the forces, less clamping force is required and the bearing blocks can mount to the frame, which reduces the structural requirements. It was turned with a fp motor/trans combo with a 4 in skyway wheel. The benefit of this setup is that if there are very high rotational forces, it will slip instead of break, so if you get caught in the rack, it will tend to rotate out instead of stress the chain. I'll try and find a better pic later

[Gene Williams]

Vivek,

The Martians, Team 494, lead engineer Jay Tenbrink has designed our robots with turrets for several years. We use a Kaydon bearing. It's mounted by it's outer and the inner race. We secure the bearings race with machined blocks that clamp it to the robot via a mounting plate and use the same block method to attach the arm or whatever the device may be to the other bearing race. It's hard for me to describe. A picture is worth a thousand words! See the publication that's out on robot design. You will find our robot featured in it with drawings of the turret. You can also contact us and we can advise you over the phone. PM me and I'll help out the best I can. Good luck.

Gene