The best way to mount wheels?

[corrado33]

I'm in a conundrum...

I can't figure out a good way to mount wheels to a smallish geared DC motor I have.  It's hard finding parts for small robots!

Basically I have a motor with an 3/16in shaft.  That's smaller than most wheels accept.  Most of what I've seen are 1/4 inch at the smallest.  So I could do a bunch of different things...

*Get some sort of friction fit sleeve... Would that stand up to the repeated back and forth motion of an onmiwheeled robot?  

*Get some sort of hub with set screws.  Maybe it could be keyed on the OD?  It'd probably have an OD of 1/2 in though, which isn't a problem.

*Get a hub like you see on the ends of servos.    The red thing...  EDIT:  AH-HA they're called servo HORNS.  Found em online.  I was right, they're a buck.

*Or I could make some sort of elaborate axle out of a piece of 1/2 inch (keyed) stock with a 3/16 inch hole drilled perfectly straight down the center... While I would LOVE to do it this way, I don't have the resources (I really need to buy a drill press, I suck at drilling straight holes). Then I could weld the 3/16 inch shaft inside the 1/2 inch stock.  Or rather have my brother do it since he rocks at tig welding...

*Or I could tap my wheel and screw it on to an axle.  But how would that hold up to back and forth motion?  Locktight?  

The bolded is what I think is my best bet.  I think it'd be the cheapest (I can't imagine those hub things would be more than a couple of bucks), and the easiest to implement.  I just have to make sure it's centered.  But I have NO idea where to find those things.  Can anyone help me out?  

I'm gunna go look at mcmaster now... see if I can come up with any ideas.  I guess I could make the things, can't be that hard.

[corrado33]

I know, double post.

But I think I am going to go with a servo horn.  The only problem now is how to connect the horn to the shaft.  I'm thinking drilling and tapping a hole in the end, with an itsy bitsy bolt.  It doesn't seem like the holes in the middle of servo horns are kept to any tolerance since usually a screw just goes through it.  Well, at least on the measurement drawings, the hole size is not defined.  

Yes I know this takes me back to drilling straight holes, but drilling a hole for a (small) screw to go into is a lot less deep than drilling a hole for a shaft to go into.  

Or, instead of a shaft I could use a threaded rod and wedge the thing in between two nuts...  They'd probably come loose though. 

[waltr]

Another option is use a brass wheel collar with a set screw sold for retaining model airplane wheels. Then solder a brass disk to the collar. Drill three or more holes around the disk for screws to the wheel like you would do with a servo horn.

The brass collars are chrome plated so you need to file off the chrome to expose the brass. Then use a strong solder (not electronic solder) with an acid flux. Stay Bright brand works very well.
http://www.google.com/products/catalog?q=stay+bright+solder&hl=en&client=firefox-a&hs=6x3&rls=org.mozilla:en-US:official&prmd=ivns&bav=on.2,or.r_gc.r_pw.&biw=1280&bih=839&um=1&ie=UTF-8&tbm=shop&cid=293056921266805762&sa=X&ei=YTcJTrjeJoT10gGHi52IAQ&ved=0CFAQ8wIwAA

[corrado33]

Another option is use a brass wheel collar with a set screw sold for retaining model airplane wheels. Then solder a brass disk to the collar. Drill three or more holes around the disk for screws to the wheel like you would do with a servo horn.

The brass collars are chrome plated so you need to file off the chrome to expose the brass. Then use a strong solder (not electronic solder) with an acid flux. Stay Bright brand works very well.
http://www.google.com/products/catalog?q=stay+bright+solder&hl=en&client=firefox-a&hs=6x3&rls=org.mozilla:en-US:official&prmd=ivns&bav=on.2,or.r_gc.r_pw.&biw=1280&bih=839&um=1&ie=UTF-8&tbm=shop&cid=293056921266805762&sa=X&ei=YTcJTrjeJoT10gGHi52IAQ&ved=0CFAQ8wIwAA

I like that idea...  Should be solid (since it has a set screw) and hold together well.  Well, depending on how well I solder it.  Or would it be considered brazing? 

[waltr]

Stay Bright solder is very strong so you don't need to braze. Stay Bright is a low temperature silver solder that melt with a soldering iron. It comes with a bottle of HCl (Hydrochloric acid) flux. If you can solder wires well then you can get a good solder joint with Stay Bright. (Disclaimer: I have no financial interest in this produce. I just have used it for many years).

[corrado33]

I actually found a better way to do it. 

I have to admit, I don't have geared motors, I'm just putting gears on the end of them cause I got ungeared DC motors and gears REALLY cheap. 

Anyway, I just drilled out the final gear that connects to the wheel to 1/4 inches.  That way it's the same I/D as the wheels I'm using.  Easy hu?

[waltr]

Yep. the simplest method is usually best.

[Admin]

You want to make a wheel coupler:
http://www.robotroom.com/MountsAndCouplers4.html

And some wheels even come with one built in:

[kornylak]

Hi Corrado33,

Can you tell me where you got your red servo horn pictured bolted to a Transwheel (either 2" or 4" OD), the part # ordered and the gear size it mounts to on a servo?

Thanks,  I'm trying to promote Society of Robots while also promoting solutions for our wheels, Kornylak Transwheels and Omniwheels for robotic applications, and need this info. so I can link back to a source of the servo horns.

Thanks, Pete Ward Sr. Project Engineer, Kornylak Corporation

[corrado33]

Hi Corrado33,

Can you tell me where you got your red servo horn pictured bolted to a Transwheel (either 2" or 4" OD), the part # ordered and the gear size it mounts to on a servo?

Thanks,  I'm trying to promote Society of Robots while also promoting solutions for our wheels, Kornylak Transwheels and Omniwheels for robotic applications, and need this info. so I can link back to a source of the servo horns.

Thanks, Pete Ward Sr. Project Engineer, Kornylak Corporation

The bot is above is actually admin's (I think).  It's not mine.  But you can find servo horns like the one pictured above on this site.

http://www.servocity.com/html/servo_arms___horns.html

as well as many others.