09-02-2012 10:03

DampRobot

Re: pic: Wheel

Wow, that's an amazing machining job! Did you machine it yourself just to get the diameter to 3.5 inches? I really like how you integrated the sprocket with the wheel.

09-02-2012 12:35

Jacob Paikoff

Re: pic: Wheel

Nice wheel Jeff.

Bryan showed me some earlier pictures of it and I'm glad to see you got it all done.

09-02-2012 13:12

Jeff 801

Re: pic: Wheel

I started with a 3.75" OD stock and Machined the sprockets as well as removed a lot of material from the other side.

09-02-2012 13:24

Madison

Re: pic: Wheel

Why?

What advantages does this offer over a more common, more flexible approach?

09-02-2012 13:27

sdcantrell56

Re: pic: Wheel

I will have to echo this question.

That said it is definitely "cool"

09-02-2012 13:30

Sean Raia

Re: pic: Wheel

I find it cool that the sprocket is part of the wheel... this allows for a rigid "mount" that cannot be beat.

09-02-2012 13:33

sdcantrell56

Re: pic: Wheel

It's definitely rigid at the expense of a huge amount of machining time and material waste. The sprocket also doesnt have the typical chamfer which could lead to interesting performance as well.

09-02-2012 13:34

Tristan Lall

Re: pic: Wheel

Someone has an extreme aversion to fasteners?

In a way, it's built like an aircraft part: lots of material wasted to get a complex solid shape—but few fasteners and joints to worry about, and minimal weight. But it seems like if you're going to go to those lengths to save weight, you ought to do something about the rim thickness. (Or is it going to be sliced much narrower later, and/or turned down significantly?)

09-02-2012 14:11

Jeff 801

Re: pic: Wheel

It removes 6 bolts, nuts, washers and spacers per wheel from your drive system.

Machine time is really not that bad because all that really is added is a roughing operation to remove the material from the OD of the wheel to the OD of the sprocket then an 1/8" cutter does the teeth of the sprockets and for extra lightning I went in with a 3/16 cutter to put the spokes on the sprockets then finished it a woodruff/ keyseat cutter to get the space between the sprockets.
As far as material waste it uses an extra 3/4" of stock on the wheel.
The lack of the chamfer is not that big of a deal I have ran sprockets like this over the past 3 seasons with no issues.

09-02-2012 14:13

45Auto

Re: pic: Wheel

Just think how much fun it'll be when you find out you need a slightly larger or smaller sprocket!

09-02-2012 14:17

Jeff 801

Re: pic: Wheel

On the drive system between wheels the ratio should always be 1:1 (assuming same wheel size) and with one of the wheels being direct drive if there is a ratio issue it would be accounted for in the gearbox

09-02-2012 14:43

DampRobot

Re: pic: Wheel

Yeah, I'd be interested in how the sprocket without the chamfer would work out. I predict finikeyness if not executed properly...

09-02-2012 15:47

JamesBrown

Re: pic: Wheel

What is the weight benefit for that? Is there another benefit besides weight? This just seems like a really impractical way to make a wheel.

10-02-2012 10:39

Kevin_Morris

Re: pic: Wheel

Not to give the textbook mentor answer, but if students learned in the process, I see that it has more benefit than just weight saving. If they didn't... well it's still pretty nifty.




I too was wondering why the rim thickness was kept so thick, until I realized the center spokes of the wheel are only about 3/4" or so wide (relative to wheel width). I also realized that's what you meant by "a lot of material was removed from the back side".

10-02-2012 11:11

electron

Re: pic: Wheel

Despite the obvious comments of "why?" and "where is the chamfer?", I must say that this looks like a very fun CAD and machine job! I give you many props for pulling it off!

10-02-2012 13:47

JamesBrown

Re: pic: Wheel

I agree to an extent that projects for the sake of learning are great but one of the biggest lessons to teach students is how to compare solutions (time, complexity, cost, weight, etc) to choose the appropriate one.

11-02-2012 04:39

Jeff 801

Re: pic: Wheel

The outside of the wheel is really not that thick if you look at this picture you will get a better idea of why you thought it was. The spokes are only 1/4" wide. When I said remove material on the back side it was to take the OD of the part from 3.75 to the OD of the sprockets at ~2.15"



I understand cost benefit analysis. The addition of the double sprocket added only 30 min to the total cycle time of the wheel. In that added 30 min a total of 26 individual components were removed from each wheel (assuming the use of individual spacers). In the end its a simple and elegant solution to making a wheel and sprocket assembly simpler.