Reducing Colson Wheel Diameter

[first_newbie]

How would one go about reducing colson wheel diameter? This would be done so that a center drop would not be need to be made.

[Richard.Varone]

It's funny you ask, all you need is a Lathe, File, and caliper!

http://i.imgur.com/i1vMoVE.jpg

http://i.imgur.com/UbcVnva.jpg

All you do it stick a piece of hex shaft into the lathe, slip a locking collar on, put the wheel in, turn the lathe on and hold a file to it.

We did this for ~100 wheels, they where turned from 3" to 2.9" and 2.7"

[R.C.]

Originally Posted by first_newbie

How would one go about reducing colson wheel diameter? This would be done so that a center drop would not be need to be made.

Does the colson have a hex built into it? If so just take a 1/2 shaft with some sort of bolt/snap ring on the end. And just use a lathe to reduce the diameter.

[Richard.Varone]

Originally Posted by R.C.

Does the colson have a hex built into it? If so just take a 1/2 shaft with some sort of bolt/snap ring on the end. And just use a lathe to reduce the diameter.

I'm not sure if you've had different results, but for us normal lathe tooling didn't work very well and found that a file worked the best.

[R.C.]

Originally Posted by Richard.Varone

I'm not sure if you've had different results, but for us normal lathe tooling didn't work very well and found that a file worked the best.

We used super small radius/sharp carbide insert that we normally use for aluminum. Works pretty well but I can see a file working pretty good as well or some misc HSS tool.

[Cothron Theiss]

Originally Posted by first_newbie

How would one go about reducing colson wheel diameter? This would be done so that a center drop would not be need to be made.

If your wheels are spinning at the same RPM, wouldn't this cause issues with the actual contact speeds of the wheels being different? It seems to me that the larger center wheels would lose traction often and cause your drivetrain to "skip" or at least decrease the smoothness of the drive.

[FarmerJohn]

I wonder if a file would add a tread pattern onto the colson, or if a better effect can be achieved with a knurling tool.

[DonRotolo]

Originally Posted by FarmerJohn

I wonder if a file would add a tread pattern onto the colson, or if a better effect can be achieved with a knurling tool.

I don't think a knurling tool will work in a soft material such as colson tread

[Alan Anderson]

Originally Posted by Cothron Theiss

If your wheels are spinning at the same RPM, wouldn't this cause issues with the actual contact speeds of the wheels being different? It seems to me that the larger center wheels would lose traction often and cause your drivetrain to "skip" or at least decrease the smoothness of the drive.

We worried about that in 2007, with an extra layer of tread affixed on the center wheels of our six-wheel-drive (it didn't have a drop on the axle). If anything, it made the robot drive more smoothly. We never decided exactly why that was.

[Chris is me]

Originally Posted by Richard.Varone

I'm not sure if you've had different results, but for us normal lathe tooling didn't work very well and found that a file worked the best.

You need to use a very sharp tool to avoid just ripping up the wheel, but it can be done. For this case, I'd just use a file since you are taking off so little and you want to take off *just* enough for smooth turning but no more than you need to.

If your wheels are spinning at the same RPM, wouldn't this cause issues with the actual contact speeds of the wheels being different? It seems to me that the larger center wheels would lose traction often and cause your drivetrain to "skip" or at least decrease the smoothness of the drive.

The very, very small diameter changes required to make this work would have a negligible effect on speed - seriously, this is taking about around 1/16th of an inch off the diameter of a wheel, maybe 1/8 if you're pushing it.

[Richard Wallace]

Originally Posted by Alan Anderson

We worried about that in 2007, with an extra layer of tread affixed on the center wheels of our six-wheel-drive (it didn't have a drop on the axle). If anything, it made the robot drive more smoothly. We never decided exactly why that was.

I'll hazard a guess:

The larger wheels spin faster, and exert more traction force because they support more of the robot's weight. That means a slight drag at the smaller wheels, which will be toward the rear in a 6WD because the front smaller wheels are lifted by torque. Rear drag opposes turning, making the robot feel smoother to driver.

[ollien]

Originally Posted by Richard.Varone

http://i.imgur.com/i1vMoVE.jpg

Get that man some safety glasses! Not that I've never been guilty of doing the same thing in a hurry.

[Cothron Theiss]

Originally Posted by Richard Wallace

I'll hazard a guess:

The larger wheels spin faster, and exert more traction force because they support more of the robot's weight. That means a slight drag at the smaller wheels, which will be toward the rear in a 6WD because the front smaller wheels are lifted by torque. Rear drag opposes turning, making the robot feel smoother to driver.

Ok, thank you for the explanation.