pic: 296's Tri-Star Wheel

[pras870]

You're misunderstanding my statement. I didn't say it was machined badly, I'm saying a team like that could of machined it BETTER. I'm talking mainly about the edges, personally if it was me, I would of made it more of a straight edge as opposed to being bumpy such as theres. I'm not sure if it's meant to be like that, but seeing as how big the tires are, and what they're trying to do, I'm just offering my opinion.

[tkwetzel]

I noticed that all the tri-wheels have the same "bumpy edges" and I believe they were designed like that. The sides are all the same too...also implying the general design.

[Cory]

Who the heck cares how well they machined it? jeez... dont you have something on your robot to work on rather than nitpicking someone else's machining? I think it looks pretty darn good myself, and I cant wait to see it in action. Good job 296!

P.S. If the parts I made looked as good as those, I would be very happy

Cory

[Alavinus]

Originally Posted by pras870

You're misunderstanding my statement. I didn't say it was machined badly, I'm saying a team like that could of machined it BETTER. I'm talking mainly about the edges, personally if it was me, I would of made it more of a straight edge as opposed to being bumpy such as theres. I'm not sure if it's meant to be like that, but seeing as how big the tires are, and what they're trying to do, I'm just offering my opinion.

I'm not affiliated with their team in anyw ay, but I'd guess the reason for the edges is to give that gear a little extra support all around. The edges bow out slightly around the axle and then go back in probably to save weight.

So now for some questions: CNC milled or waterjet? To me it looks like it was cut with a waterjet. Also- did you get the idea for the curve from a stress analyzation program? We had an engineer on our team once who had the software and allowed us to save all kinds of weight.

Anyway, great looking part and keep up the great machining.

[Pat Fairbank]

Sorry for not replying sooner - I've been at robotics all weekend until now.

Those wheels weigh ten pounds each, and we are using two in the front, with two six-inch wheels in the back.

We actually designed the sides of the plates that way (not straight) , only because we found that the metal would touch the corner of the step while we were climbing it. It's not a curve, just either two or three seperate straight sides that meet to form corners. We got the plates, shafts and wheel hubs machined professionally (I'm not sure what method they used, but the plates look pretty sweet up close).

The turning is very good, considering all eight of our wheels are made of neoprene rubber.

Hope that answers all your questions.

[Adam Y.]

That is machined very well. Im not sure what that guy is thinking. Anway have you tested the wheels yet? Also, why did you guys go for the gears instead of chains? The weight probably would have been cut down and it would have simplified the whole process.

[Pat Fairbank]

I don't see where we could have used chains... seems like it would be a pain to tension them.

We did test the wheels, and they are performing beautifully, except that we haven't yet put delrin sliders or something else on the bottom of the 'bot, and so we can't get more than halfway up the step for now.

[Adam Y.]

I don't see where we could have used chains... seems like it would be a pain to tension them.

The chains would serve the same purpose as the gears. The only reason what I could think of using them is the weight.

[ChrisH]

Originally Posted by pras870

You're misunderstanding my statement. I didn't say it was machined badly, I'm saying a team like that could of machined it BETTER. I'm talking mainly about the edges, personally if it was me, I would of made it more of a straight edge as opposed to being bumpy such as theres. I'm not sure if it's meant to be like that, but seeing as how big the tires are, and what they're trying to do, I'm just offering my opinion.

It lookes to me like the "bumps" are to provide what we here in the aircraft biz call ED or edge distance. That is the distance from the center of a hole to the nearest edge of the part. If a hole is too near an edge it lowers the strength of the part tremendously. In general, we use a minimum ED of 1.5 times the hole diameter, though I've been noticing lately that EDs of 1 are common in commercial products. If the bumps weren't there, the shafts supporting the small gears would be hanging out in space, either that or the wheel would be even heavier.

I think the design has been nicely optimized and well executed. If there were big ugly burrs hanging off the edge or chatter marks or the edges wandered like they had been cut with a hack saw then pras870 might have a point, but as it is I don't think so. It seems pretty obvious to me that those bumps were planned and needed to be just where they are. It is a professional looking job, good work 296!