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Musclecargod
| | Posted on Friday, January 20, 2012 - 08:17 am: | 
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That last picture is interesting. The dead spline is already present (or not present depending on how you look at it).
My guess is they are using an EDM because the piece could be heat treated, and drilling at oblique angles really sucks. I don't see anything that would require extreme precision, or complex machining. Looks like an easy mod to me, that is once you fixture it up. Low volume makes EDM attractive and simple, although this could be milled/drilled for higher volume. I wouldn't tackle this on a drill press though... |
Avc8130
| | Posted on Friday, January 20, 2012 - 08:48 am: |
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If it is EDM...it MUST be plunge. That is not cheap. |
Musclecargod
| | Posted on Friday, January 20, 2012 - 10:42 am: |
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Yeah it's definitely a sinker job. But I can't imagine the tolerances are anything extreme. As long as the surface finish requirements aren't too high, this could be run rather quickly (and based on the above pictures which show plenty of chatter and tool marks I'm guessing it's not critical). Most of the money is in the setup, thus volume dictates price. |
Timebandit
| | Posted on Friday, January 20, 2012 - 01:12 pm: |
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There are definitely tooling marks on the inside of the rotor. I was using a rag to wipe down some of the oil and a razor sharp toolmark around the circumference of the rotor put a nice slice through my fingertip.
Some of that green stuff that you see is residual Loctite 648 retaining compound. I'm not quite sure why they used a 350*F retaining compound on the sprag clutch bolts and the rotor nut instead of using a threadlocking compound when the bike was made. Possible differences are that the commonly available Loctite threadlockers are rated for 300*F, while the retaining compounds are rated for 350*F. They may have chosen 648 due to concerns about heat.
Notice that in 2010 they changed the spec for the rotor nut to Loctite 272, which is rated for 450*F on large diameter fasteners > 1 inch.
It amazes me that Buell could use a retaining compound rated for 350*F on the rotor nut and still have thermal failure of the fastener related to tension relaxation. That suggests that the stator/rotor are getting pretty darned HOT.
Could it be that the reason that peoples' rotor nuts are coming off is because the stators are getting so darned hot that they're causing the 350*F Loctite 648 to fail? That would explain why there was the change to 450*F 272. |
Timebandit
| | Posted on Friday, January 20, 2012 - 01:27 pm: |
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Most of the money is in the setup, thus volume dictates price.
It would be interesting to know how much it would cost to add this feature to a run of say, 10,000 units. |
Avc8130
| | Posted on Friday, January 20, 2012 - 01:33 pm: |
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For machining:
Probably $5-10k to get a proper fixture setup and machine programming done.
Then figure ~3-5 mins/part.
For 10k, it might be about $.50-1 in setup and maybe $5-10 each to run. This part is SS, but I don't know what kind. Free machining and we are golden.
It is amazing how cheap things get at quantity and amazing how expensive 1 is. |
Timebandit
| | Posted on Friday, January 20, 2012 - 01:42 pm: |
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In other words, if you did the job in quantity, the unit cost could be $5.50 to $11.00, and that includes the $5k-$10k setup/programming cost, amortized across the production run?
So 10,000 units could cost somewhere in the range of $5.50 x 10,000 to $11.00 x 10,000? Or $55,000 to $110,000?
Wow -- Just like with GM, shave a nickel off of production cost per unit and the numbers really add up. |
Musclecargod
| | Posted on Friday, January 20, 2012 - 01:47 pm: |
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It is amazing how cheap things get at quantity and amazing how expensive 1 is.
Hit the nail on the head there.
At volume of 10,000, I think this could be done for a couple bucks a piece, depending on the hardness. A custom tool could do the hole and the counterbore in one operation. |
Timebandit
| | Posted on Friday, January 20, 2012 - 01:54 pm: |
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If you knew even half of the things that never made it into production for one reason or another, you too would want to decapitate some HD execs : )
I don't want to decapitate anyone.  But I can't help but think about those stories I've heard where some bean counter at GM decides that it's in the company's economic interest to implement a change in production, and the best ideas from the design engineers get thrown out the window in the name of profitability. |
Avc8130
| | Posted on Friday, January 20, 2012 - 01:56 pm: |
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Yeah, those are VERY rough figures.
I have bought similar components at work, in MUCH smaller quantities (~500 units) and the final price was usually ~$2-300. That would be for something similar to the whole item you have pictured there.
Adding these holes would not have been a very big deal in the long run if it was done from the very start.
If the change was to be implemented after, logistics apply and all bets are off.
Really, I don't see how a competent machine shop couldn't perform this mod for a very reasonable price "free-hand". |
Timebandit
| | Posted on Friday, January 20, 2012 - 02:09 pm: |
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Any problems working with magentized metals? Not in terms of getting the work done, but in terms of damaging the magnet's strength.
Heating magnetized metal is *BAD* for it. We also know that over torquing it is bad for it. The problem is that to pull off the rotor, you have to heat the rotor nut.
The H-D service manual instructs the tech to use a Robinair heat gun to heat the nut. That's going to heat the nut and the rotor. Not good. Instead of using a blunt force heating device like a heat gun, EBR recommended propane. I had MAPP, so I used a fine point torch to directly heat the corners of the rotor nut.
Amazing how well the 648 was holding that bolt on. After briefly heating the nut, I almost tipped the bike off of the Pitbull stands with the 25" breaker bar. I applied more heat at each corner of the nut and it came off with a lot less effort. Unfortunately, the nut required enough heat (maybe 30 seconds) that I noticed water vapor was starting to condense on the face of the rotor. The rotor had to be getting hot too.
My main concern about using torque/impact/heat in removing the stator nut revolved around damaging the B-field magnetization of the rotor. I also worry about what effects different forms of machining might have on a perfectly good rotor. It would really suck to go through all of this effort, and then magnetically (invisibly) damage the rotor so that instead of having a 530W charging system, you end up with something that's weaker than it was before you got started.
What kind of risks are there to the magnetic strength when you go machining magnetized parts? |
Avc8130
| | Posted on Friday, January 20, 2012 - 02:17 pm: |
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Is the component being machined Stainless Steel? Is any machining done directly to the permanent magnets?
http://www.magnetsales.com/Design/FAQs_frames/FAQs_3.htm
(Message edited by avc8130 on January 20, 2012) |
Musclecargod
| | Posted on Friday, January 20, 2012 - 03:26 pm: |
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I agree a competent machine shop could "free hand" these pretty easily.
I don't think machining magnetized parts would present much issue to the magnetic strength as long as heat and vibrations were kept in check. But chip evacuation is a pia with magnetized stuff, both in mills/lathes and sinker. |
Timebandit
| | Posted on Friday, January 20, 2012 - 03:43 pm: |
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I don't know the composition of the steel.
The only machining that has to be done (AFAIK) is to cut the pilot hole and jet near the center of the rotor. The good news is that at that central location, the magnetic pole is going to be close to neutral.
The magnetic north and south poles would be located on the large "lip" surface of the bowl, at the farthest possible distances from the rotor's central axis. I don't think any machining is going to go on there... unless the rotor has to be rebalanced. In that case, there could be a smidgen of metal taken off at the base of the opposite side.
I'm not sure if I took a photo that shows the balancing cuts or not. Will have to look. |
Timebandit
| | Posted on Friday, January 20, 2012 - 04:12 pm: |
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They use air for installing it too? Do they set final torque by hand?
I followed up on this question.
The torque spec for fastening the rotor nut is 400 N-m, or 300 ft-lb with Loctite 272.
I asked whether someone in the field could use an air impact on the rotor nut. I asked specifically, is the 300 ft-lb rating a minimum, and can it be safely exceeded and by how much?
I was told that the torque-to-failure rating on the rotor nut is 400 ft-lb.
There's your answer.
Although it would be safe to use an air gun that's limited to the proper torque, you definitely wouldn't want to use a heavy duty 1/2" impact gun that's jacked up to it's max 600 ft-lb output -- that could exceed the failure rating of the nut.
EBR uses those expensive torque wrenches that cost about $650 at Snap-On.
My torquing tool was a lot cheaper. 6-foot breaker bar/extension, with a 50-lb bucket of sand hung on the end. 300 ft-lb. |
Avc8130
| | Posted on Friday, January 20, 2012 - 04:19 pm: |
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Time,
Good job, Newton. 
ac |
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