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Pretty good start! How do you plan to attach tread (and what kind of tread)?

The fillets should be okay, especially with a ball-end mill. However, you could simplify it a bit by removing the fillets that are not going in the direction of the axis of rotation of the wheel. In other words, only keep the fillets that can be cut by a normal mill when the wheel is laying flat.

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For tread, I figured I'd just rivet on a strip of blue nitrile roughtop. With 6 or 12 rivets it should hold I think...

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I was thinking this as well.

Any reason for hex as opposed to keyed, or was this not for any particular purpose?

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Hex is way better than keyed, less parts and a stronger connection.

As for the fillets, using a ball end mill to make those fillets is no more difficult than the wheel without. I'm a big fan of them, and every set of wheels I've had machined since 07 has had that feature.

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Chris, RC, and I have just been working on a few things lately that are mostly direct driven such as cost effective West Coast drives. Hex is just much easier to work with when doing this. (Or in most situations actually).

Keep the fillets Chris, they're just another method to disperse stress.

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Have you considered a tread groove?

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Chris, what about making the spokes with a channel cross section? might save some weight and add some strength, if you do it right. And I'm sure it would provide a good SW challenge for at least a few minutes

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You mean all, right? I hate keys and everything about them and never want to work with them if I can avoid it. Hex broaches are not cheap at all, but I think Shaker can earn enough this summer to get one, or we can pool with local teams and collaborators for broaching. After a few scary wheel and chain failures this year, I want to look into live axle drivetrains including West-Coast cantilevered drives.

Yeah, and I may add one to the model just to gain experience. I'm tempted to say with 6 evenly spaced rivets, the tread won't budge, but at least it'll help with the initial setup.

I'm really satisfied with the wheel weight as is, but I'll likely do this just to have fun with Solidworks and to push myself a little further. Thanks for the inspiration.

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This looks awesome!!!

Have you considered drilling a center hole instead of the hex hole and putting this on one side of each wheel?
I am almost sure that it will save you a lot of money when making those wheels... it might weigh a bit more but it will still be cheaper...

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I highly reccommended that you do this or use a contact adhesive on your tread in addition to rivets.

BTW: If you want to free up machine time and get almost the same thing at a reasonable price:
http://www.andymark.biz/am-0393.html

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If you have a hex broach and an arbor press, it will be much cheaper than $15/wheel to get the hexagonal hole.

A 1/2" hex broach is only like $200 on McMaster, so if you plan on making more than 13 hex broached parts, its probably worth it. (A 6wd live axle would require 16: 6 wheels, 10 sprockets.)

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You don't even need an arbor press to do the broaching. Our team has done all of our broaching by just putting the broach in the tailstock of our lathe and pushing it throught the part pressed up against the chuck (not held in the jaws).

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Nice first design. It definitely looks a lot like the AM performance wheel and depending on how much time/money you have, buying those would be more cost effective although making your own is certainly cool!

I definitely echo the sentiment of sticking with the hex at all costs, and keeping the fillets. Its really incredible how much extra strength the fillets give in bending.

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I will agree with Nick on both counts.
A recess for the tread is the only way to go, then you only need two rivets at each end if the tread, the groove takes all the side load on the tread.
And the hex broach is far superior to bolting the A/M flanges on your wheels.
mike d

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If you're tight on money and like working with your hands, you can make your own hex broach for 'soft' materials like plastic or aluminum. All you need is an old HSS end mill, a lathe, and a precision grinder. It'll work good enough for FRC-style applications.

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If you've got SW2010 with all the options, try running an FEA on it and what sort of loading it might see and what benefits/sacrifices are required to make it out of different materials. Solidworks Sim is butt-simple to use, very robust, and gives reasonably accurate answers.

For example, if you make it out of 7075 it could weigh significantly less than if it's made out of 6061T6 because of the strength advantage of 7075. What about 2024?

Could you make it out of steel and weld it to an output shaft? Drilling a round hole is easier than broaching, and a welded shaft can be incredibly strong. You could use an alloy steel like 4340 or 4130 that has a strength/weight ratio that's better than most aluminums. I know it's harder to machine, but you might need fewer spokes for the same strength, so there would be less machining required.

I'd do these just as a exercise in SW (think about setting up different configurations for the same model too) but if you like where it's going don't be afraid to break out of the typical FIRST rut of "pretty machined aluminum everything".

Edit: also, the rendering looks really nice :-)

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I have to comment about those "silly tutorials and guides", all good 3d modelers cannot go a day without having to look something up and watch a tutorial. It is not a sign of weakness, but a sign of "knowing when to ask for help". :)

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Hey Art,

Could you elaborate on the proper way to do this? Sounds very interesting. Thanks.

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My roommate did this to broach some aluminum parts for a combat robot he was working on.

What you do is take an old HSS end mill, and cut off the cutter portion of it, leaving just the shank. Then mount this in a collet in a lathe with cut off end of the end mill sticking into the lathe, with the original end sticking out. Crank turn on the lathe, and then hold a Dremel with a cutoff tool perpendicular to the end of the end mill, and slowly turn the entire end of the end mill into a concave dimple.

Then get a large piece of steel hex stock, mount it in the lathe, and bore a through hole the same diameter as the end mill. Mount this piece of hex stock in a milling machine and drill/tap holes for set screws to hold against the flats of the HSS end mill shank.

Then mount the HSS end mill shank into the hex stock, and make sure the set screws are against the flats of the end mill, with the dimpled end sticking out. Then go over to the precision grinder and stick and steel hex stock on it, and activate the magnets to keep it in place. Now use the precision grinder, which should have a XZ table. Slowly start grinding down a flat into the HSS end mill. Once you've started this, deactivate the magnets, turn the steel hex stock by 60 degrees onto the adjacent face, and again grind down a small amount.

Don't adjust the Z-distance until you've done all six faces; it helps to mark one with a Sharpie/some mark, to make sure the hex stays true. Keep going, grinding down all six faces, then readjusting the Z, and then again grind down all six faces until you reach the correct size hex you desire. Now you have a homemade HSS hex broach. To use, simply first bore a round hole to the diameter you want in a lathe, then mount the HSS hex broach in a lathe and use then force the homemade hex broach through the round hole (while the lathe is stationary of course).

It might take an hour to make your own hex broach, but for broke college students, it sure beat spenting $$$ to buy one.

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I know, I'm just lazy. :)

I'll probably fire up those tutorials and guides today, before I work on stuff a little more ambitious.

I ran an FEA on the wheel and it tells me it's more than strong enough for the peak side load this wheel would have as is (safety factor of 10 or something). I probably did something wrong with the FEA.

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My suggestions, most of which have been said, are to make a tread groove and i would suggest two rivits at the start and end of the tread and two in the middle.

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That's the same design we used last year for our gyro for stearing only difference was we had a hole for key and round shaft instead of hex

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I could only dream of getting PhotoView 360 to cooperate...

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What do you mean? I never have a problem with it...

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Same here. I have a mid range workstation provided by RPI and it works without a hitch. Solidworks is more likely to crash my graphics drivers...