How do i make this part??

[dfukuba]

Hey there guys,

I'm working on making a scooter that uses two bicycle wheels. I need to created a pair of hubs for the bucycle wheels, that attach to the gearbox output shaft i'm using.

http://tlb.org/scooter2_fab_drawings.pdf (Page 3 &4)

I'm not to familiar with using the compound angle part of the lathe. If anyone know a good place for learning these machining techniques, could they let me know? thanks.

The equipment at our school is also not the best, so i would be willing to pay someone out here that is confident that they could make it. Just let me know what you'd charge.

of course i would prefer to learn how to do it my self of course :")

thanks for any help.
--Dan

[Foster]

I can't help you on the fabrication of the hubs.

On the other hand they look pretty close to standard bike hubs, so I would visit a few bike shops / repair places and see what they have for replacement hubs. I'd look to see what I could do some minor changes to and get them. The local bike repair guy is pretty clever, I'd explain what I was trying to do and see what he suggests.

It looks like you want to direct drive the hubs, can you get by with driving a small sprocket that's attached by chain to the drive hub of the wheel?

Good luck!

[IKE]

If you really want to do a custom Hub you can get a quote from emachineshop.com

http://www.emachineshop.com/

They have software that you download and then you make the part. It will take a little time to get used to their software and does require some machining knowledge (but not much). The best part is that you pick the processes, material, and quantity, then press quote and TaH DaH! You have a price and you can order it. Typically it takes 3-4 weeks to get custom parts (that is why it isn't the greatest FIRST Resource).

If you have a lathe and some generic tooling and some metal and skill, you can make this yourself. You will then need a mill and a rotary table to get the holes in the hubs concentric. making this part by hand will be difficult and time consuming.

Overally i personally would not re-invent the wheel (pun intended). I would shop around an find a design that fits your needs that you can get to work. If you are making a scooter do you want it to coast? Direct drive may not be good for coasting.

[RaMoore]

That part will be pretty difficult to make with any accuracy if your school's equipment is as poorly maintained as mine! You should try to make a little one, not to scale, just to learn the process and see how it goes.

We make most of our hole patterns using a small rotary table on just a table top mill and you can get pretty good, but it takes practice!

I have used MFG Quote before with reasonable success.

You can select qty, material quality, etc and then upload your design drawings and company's will place bids and then you can award the part. Most companies will even take "make to model" also if you have Inventor/ProE or any models typically that you can convert to .iges or .step. You can get a huge range of prices, but you have to look at the manufacturer very closely!

[artdutra04]

Oooh, that part makes me cringe when I think about actually milling/turning that part.

Does it have to be one solid piece? It would be a lot easier to make that part if it were two halves that bolt/weld together.

[dfukuba]

The part does need to be once piece, this is because the spokes of the bike wheel would be mounted pulling on those smaller holes to keep the wheel tensioned and true.

I wen to my local bike shop the other day to ask him about lacing the wheel, and what he thought about doing this overall (i will agree that bike shop guys really know their stuff). He hadn't seen someone do this before, and wasn't really sure what another reliable way would be to do it.

I will have to check out the MFGquote place. What do you mean by "but you have to look at the manufacturer very closely!"?

emachine shop is nice, i could say it was the first time i used CAD hehe. I've heard that they're pretty expensive, and i would like to have my part before the amount of time it would take for them to make it :"/

this hub will be mounting to two of these guys i don't want to have this wheel cantilevered over the shaft tooo much (this is the reason for the deep holes on each side of the hub.

--Dan

[SuperJake]

Any shop with a good CNC Lathe can turn that out in no-time. The holes around the perimeter are also trivial on even an NC Mill. The trick is the tools you use to build it. You should be able to use Google to find a machine shop in your area that can quote the part (A really good shop will ask for the 3D files to make the part). Who knows - you might even find a new sponsor for your team this way!

Good luck!

[RaMoore]

I would agree that local is typically a better connection.

If that's not an option, what I meant by my word of caution is that not all shops have same quality or service. I didn't have any real problems with the 4 companies I worked with.

MFGquote will get you a good number of quotes (from around the world) in a day or two and they will have a huge range (just a guess $50 - $800) and you'll just need to look up the suppliers rating on the site. It's just like buying anything else online, sometimes the cheapest will only get you a bad product (and sometimes the most expensive will). Look at local or regional bids and to keep the cost reasonable correctly dimension your drawing with reasonable tolerances.

[EricH]

If a local community college has a machine shop course, take it. This'll deal with learning the compound angle. (I'm short on time right now; when/if I get more, I'll take a look and see what I'd do in that situation.)

[sanddrag]

You might try http://www.rfqwork.com/ or the RFQ forum on www.cnczone.com

This can be done on manual machinery, but you'd need digital readout or preferably a dividing head to get those holes

[Cory]

Why not just use a bike hub?

[DonRotolo]

In looking closely at the drawings for the hub, quite frankly it is not all that hard to make. Time consuming, perhaps, but not a technical challenge. It is important that you find someone with machining epxerience, since selection of tools and turning speeds are important.

You do need to get the material first, and you will need material that is at least 2 inches longer than the workpiece - maybe 5 inches for each hub. You first cut the outside profile and then the deep bore on the one side. Mark the rim every 20 degrees for the small holes now, too.

Flip the piece and grip it inside the deep bore, and make the shallow bore. Drill the 4 holes, and then the 18 holes (make a jig to do that, as they suggest, using the 4 holes to locate the jig. That way, you only have to be careful with one piece (the jig) and all four edges (2 hubs) will turn out identical with little extra effort.

I would allow for 3 hours for each one, but I'm experienced, so allow twice that for the first one. Also remember that tolerances are not that critical, so long as both are the same. +/- 0.010 is more than enough.

Don

[Doug G]

I have to agree with Cory and others here. Perhaps we are missing the point - is it that you want to learn how to machine stuff like this?

Otherwise go get a bike hub and fab something similar to match your drive shaft. I remember we used to get those skyway wheelchair wheels and either used the spoke couplers that FIRST supplied or one year we made our own so we could use a keyed shaft. Much simpler than the route you're taking.

[Richard Wallace]

I like your hub design. It transfers the wheel load to the gearhead with minimum cantilever, and that will be important in your application.

Quite a few years back, I was part of a rookie college-level solar racing team. We built custom wheels for our car using 20" rims, and our hubs had a similar aspect ratio to yours -- about 3.5" spoke-hole circle and 3" axial width. Local bike shop guys assembled them for us using a three-cross pattern to help with the side loads. Our car weighed about 700 pounds (plus driver) and had about 5 ft. track width. Those wheels held up nicely during the transcontinental race, with no problems apart from the expected few flats. We never damaged a rim.

Our hubs were machined from billets using a process similar to the one Don Rotolo described above.

What diameter rims will you use?

[dfukuba]

Cory,

the reason why were making out own is because as richard pointed out, it will take a lot more load off of the wheel, and i don't want to cantilever the motor shaft too much by having a 3" long hub, mounted on the end of the shaft.

Rhichard,

I am going to be using a 20" x 1.5" wheel with 36 spokes. The design did go very well (I can't take any credit, it was first made by Trevor Blackwell). He had made three pairs on current projects that i checked out, those things are as solid as a rock, they take lateral load fairly well.

doug,

I actually used 20 skyway wheels on my first prototype of the scooter, but they started cracking due to (what i believe) was the lateral load on it.

Don & eveyone else

what i was told when trevor made his, is that he made a mandrel that bolted on to the four holes. So when he flipped it over he could chuck the mandrel on the lathe. Would this work better then doing it the other way??

I had some 3" diameter Aluminum stock that we got for this years robot (something like 6' of it, tooo bad it wasn't just a little bigger) I tried makeing a smaller version of something that looked just like it. It started turning out pretty nice, the part i was having trouble with was boring out the insides. It was probably because of the tooling that we have at the school...I'm thinking about buying a set of my own cutters. anyone have any good places online to order lathe cutters??

Also, facing off that angle in the cavity seems to be the one thing i'm not sure how to do, any advice?

thanks!!
--daniel