pic: GUS Team 228's Prototype Sheet Metal 6WD Chassis

[Bruceb]

I was wondering if you could post a picture of the hub you are talking about?
Bruce

[Brandon Holley]

Originally Posted by Rob Stehlik

Brandon,
Thanks for the info on Colson wheels. I got a sample from Mcmaster a while ago, and they do seem to be nice wheels. Obviously they were never intended to be powered, which is why they are difficult to mount hubs to. The one I got has a 1/2" bore, but this is with plastic bushings. The hub itself is 7/8", which could be broached, but now that you mention it, the plastic is a bit soft, and may not hold up well under stress. I was looking for an alternative to knurling because while we do have the tools, it seems like it would be a bit time consuming to get it right on a manual lathe.
I guess with Colsons the initial effort to mount them is offset by the benefit of never having to change treads.
Rob

Rob you are right on in regard to the effort to mount them. They really are NICE wheels though, and can be worth the effort. If you have the resources to make hubs, you could make something similar to this...

This is just a very quick CAD I made from memory of what I did to mount Colsons on the 05 and 06 robots I helped with. The inner hub is converted into that round boss sticking off the hub where you could press bearings into it. Then, the notches around the outside grab a hold of the ribs you see on the Colson wheel. The hole pattern can then be drilled through the wheel so you can compress sprocket, hub, and wheel with the same bolt pattern to make entire wheel assemblies. Just an idea to get those other ideas flowing...

-Brando

[Madison]

Can someone provide a part no. from McMaster for these wheels? I know they're available elsewhere, but McMaster seems like it might be a more reliable source.

I haven't been able to find any good information regarding bore diameter and overall hub diameter, but if the hub is large enough to accept the pseudo-standard 1.875" six hole circle, these should be pretty easy to mount.

[Aren_Hill]

Searching "rubber wheels" in mcmaster brings up the page

Colson Performa (the wheels in this thread) are on the lower half of the page titled "Performance rubber wheels"

We used the 3"x7/8ths wide ones in the 4 corners of our 6wd swerve this last year, live axle 3/8ths hex hub, and 3 bolts going through the wheel and hub.

The hub was a simple 1.25" diameter .1" ish wide flange, 3 bolt pattern with a smaller diameter that went through the wheel hub.

Not having to worry about retreading is nice.

[s_forbes]

Arthur, It's great to see more awesome sheet metal musings from your team. You guys really nail the simplicity and efficiency aspect of your designs every year and have become one of my favorite teams to watch during the build season.

This looks like the most robust, clean, well thought out 6wd chassis I've seen posted up here. It's one of those designs that makes me think "I wish I had one!"

[artdutra04]

Originally Posted by Rob Stehlik

How much ground clearance is there?

About an inch; I don't have the exact number, as the files are on another computer at the moment.

But depending on the game, this number can easily be increased. One design we drew up (only drew a 2D side sketch of a chassis rail) had angled bottoms and could clear a 30-degree ramp.

Originally Posted by Rob Stehlik

If the game calls for an open front, do you have a plan for joining the frame members mid way?

The same way we did on our 2009 robot: use short end rails and an inner chassis rail further into the chassis.

Originally Posted by Rob Stehlik

For the mounting hole pattern on the frame, I'm wondering if you could make them all 1/4" holes. This would allow you to choose either 1/4-20 fasteners, or #10-24, since 1/4" is the drill size required for #10-24 PEM nuts. So if you have a spot where you want to use # 10 screws, just put in a PEM nut.

We hardly ever use 1/4-20 bolts on our FRC robots anymore as #8 or #10 screws work just as well in FRC, but at a fraction of the weight. A #10-32 screw weighs 58% of the same length 1/4-20. By modifying our hole pattern to accept either #10 bolts or 5/32 rivets, we can choose whatever fastener will work better for a particular application.

We also chose #10-32 over #10-24 for two reasons: 1) #10-32 are the screws needed to mount the CIM motor, so we might as well stick to one or the other (nothing is more annoying than picking up a #10 nylock nut and realizing it's the wrong pitch), and 2) the ratio of shank size to pitch of #10-24 screws often causes them to be the second most broken tap at machine shops (#6-32 is the worst).

Originally Posted by Rob Stehlik

I like the way you have designed in a series of holes to allow repositioning of the standoffs to serve double duty as chain tensioners. This is much more reliable than using slots to reposition a tensioner. Do you know how much excess chain length would be taken up for each position of the standoff?

It would vary for each standoff, so we didn't calculate it. We did calculate the chain length and design for an exact number of 146 25p links, so any tensioners would depend on how much it stretches.

Plus, we also have a habit of adding in a lot more mounting holes than most parts need. Often times we've found that these extra holes help us out in a pinch when we need to mount a Lexan panel or zip tie wiring to.

[AdamHeard]

Originally Posted by artdutra04

Plus, we also have a habit of adding in a lot more mounting holes than most parts need. Often times we've found that these extra holes help us out in a pinch when we need to mount a Lexan panel or zip tie wiring to.

We do the same, it's nice to have!

[skimoose]

Originally Posted by Madison

Can someone provide a part no. from McMaster for these wheels? I know they're available elsewhere, but McMaster seems like it might be a more reliable source.

I haven't been able to find any good information regarding bore diameter and overall hub diameter, but if the hub is large enough to accept the pseudo-standard 1.875" six hole circle, these should be pretty easy to mount.

We've had good luck through robot marketplace in the past. They have a good selection of sizes, and specs, including bore, are listed on each product page.

[AdamHeard]

Originally Posted by skimoose

We've had good luck through robot marketplace in the past. They have a good selection of sizes, and specs, including bore, are listed on each product page.

Compared to mcmaster, they ship painfully slow (in our experience).

[skimoose]

Originally Posted by AdamHeard

Compared to mcmaster, they ship painfully slow (in our experience).

True. Nothing beat McMaster for speed, but we've normally received our colson order from Robot Marketplace in about a week. I don't remember, but we probably could have paid extra for expedited shipping.

Originally Posted by Rob Stehlik

Brandon,
Thanks for the info on Colson wheels. I got a sample from Mcmaster a while ago, and they do seem to be nice wheels. Obviously they were never intended to be powered, which is why they are difficult to mount hubs to. The one I got has a 1/2" bore, but this is with plastic bushings. The hub itself is 7/8", which could be broached, but now that you mention it, the plastic is a bit soft, and may not hold up well under stress. I was looking for an alternative to knurling because while we do have the tools, it seems like it would be a bit time consuming to get it right on a manual lathe.
I guess with Colsons the initial effort to mount them is offset by the benefit of never having to change treads.
Rob

Actually, making the insert plugs is very simple, and we've always made them on a manual lathe. Round aluminum stock, 6061 has worked fine, turned down to +0.005-0.007" larger than the Colson wheel's bore ID. Knurl the plug stock with a standard diamond pattern tool. This will raise the plug's OD by another 0.005" or so. Bore for your preferred axle diameter. Cut to length and slightly chamfer the edge of the plug to help with the alignment during the initial insertion into the wheel. Broach the plug for your key stock or hex broach if you prefer hex shaft. The plug is done.

If you're using 2" wide Colson wheels, the plug can be a little long to broach. One year we made the plugs in two pieces. One half was bored and broached, the other half had just the bore. That made it easy to broach and we didn't have to worry about lining up the key ways.

The knurled plug works to the advantage of the soft plastic of the Colson hubs. As the plug is inserted into the wheel the knurling cuts into the plastic forming a sort of spline mating. We have never spun a wheel off of one of our plug inserts.

To Install the plugs simply place the wheel on an arbor press, place the plug onto the wheel's bore, and press until flush. I would recommend a 3-5 ton arbor press. We've used a two ton press in the past, but that's pushing the limits of the press. The plugs are self centering and self aligning. Twelve plugs were machined in about 2-3 hours, insertion takes about 10 minutes.



As for the tread pattern cut into the wheel's surface, now that was time consuming. We built a jig and used a radial arm saw to cut a 0.125" deep tread. This modification withstood an entire year's worth of wear, and greatly improved the wheel's normally impressive traction.

[topgun]

Any difference between the black tread and the gray tread offered at RobotMarketPlace? Doesn't seem to be from the specs. Is the gray non-marking whereas black is marking?

[Rich Kressly]

The NPC Wheel at robotmarketplace comes with a hub already if anyone is interested:
http://www.robotmarketplace.com/prod...lrin_hubs.html

something 1712 has used in the past

[skimoose]

Originally Posted by topgun

Any difference between the black tread and the gray tread offered at RobotMarketPlace? Doesn't seem to be from the specs. Is the gray non-marking whereas black is marking?

Yes, you are correct. Our static friction tests showed very little difference between the two compounds.

[robostangs548]

Wow, looks great guys, and it looks like it will work out very well this year! Good luck at the competitions!

[artdutra04]

Originally Posted by AdamHeard

Compared to mcmaster, they ship painfully slow (in our experience).

2011 Update: We ordered 14 Colson wheels on Sunday (16 Jan) from Robot Marketplace and their estimated delivery date with standard shipping is Thursday (20 Jan). While they may have been somewhat slow in the past, they're fine this year, and well worth the ~$5 per wheel savings over McMaster's prices.