#16
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More ways to skin a cat.
Heres some photos to show the vw disc spindle built up to porsche diameters (welded and turned between centres).I took 3.5mm from the back of the hub and rear counterbores .Made spacer to move front bearing forward 2mm to correct the pitch as much as i could.Made a spacer for the seal diameter to use 62x8x45 seal.This increased the track by 3mm each side.If i did another i would probably try it the way you did .It was basically easier for me to do it this way ,as i could do it myself.Did you use a back plate ?
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#17
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I can answer that now .It was a 3mm each side.
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#18
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Yeah, good work. A very neat solution, I like your caliper mounting bracket, I think mine is going to be harder work!
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#19
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I have added pictures showing the tools that where made up in order to machine accurately.
http://www.fastbug.net/node/219
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#20
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Thats some jig your using ,but i guess your mass producing them .I didnt realise you were a buisness .I used soft jaws machined to the front boss dia and faced them so the hub sits squaure .I didnt have to machine the front just make a bearing spacer.I guess from the pictures you press the insert in with the bearing c/b under size and finish machine that in the fixture.
Many thanks Chris .
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#21
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No its not a business.. The machining was done by a friend of mine, these are his jigs that he made in order to do it for me.
The bearing inserts where made on the lathe, then pressed in complete. The bearing spacer is separate as it had to be made from aluminium so it doesn't rust..
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#22
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Quote:
How do you get repeatable centering with that fixture held in a 3-jaw chuck? (or is accuracy beyond the 3-jaw not an issue for the machining required on the hubs?) Bill |
#23
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Hi Bill, not sure why you'd need repeatable centering, please elaborate?
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fastbug.net | FastTrack Dub Club "Straights are the boring bits that link corners together" |
#24
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Quote:
(of course some are better and some do have adjustable centering) Say you check a bar and turn it round. Remove it and put it back into the chuck. Chances are good if you put a dial indicator on it, it's not centered anymore. It looks like the same situation exists with the hub holding fixture in your pictures. Once that fixture is removed from the chuck, it'll be hard to get it back in again centered precisely the same way. Thus, not repeatable. Bill |
#25
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Ah I see, for machining both ends of the hub. I don't think it was ever a major issue, he just had to centre it as best he could every time he fixed it to the mounting tool and chuck. Resulting run-out of it all assembled was 0.01mm, so I guess he did a good job of that..
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#26
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If I understand the mods to the hub, the overall runout of the entire system will be a function only of the accuracy of the new bearing spacers (and of course the original parts' accuracy).
Very nice job, BTW. Bill |
#27
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I think the run-out we measured was on the face of the brake disk as bolted to hub (so 'wobble' if you like), not run-out at the circumference (from centering errors), but both could be effected by centering errors, and bearing spacer inacuracy as you say. Thanks, but he takes all the credit for the machining, I was just mad enough to envisage it all working...
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#28
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I'm a hobbyist machinist and 0.01mm is accuracy I can only read about, not something I achieve. ;-)
FWIW, I just looked up the Porsche specs for runout in the 996 Workshop Manual. Lateral runout of the brake disc, max. - 0.03 mm Lateral runout of the wheel hub, max. - 0.03 mm Lateral runout of the brake disc when installed, max. - 0.06 mm Maximum permissible radial runout and lateral runout of the light alloy wheels = 0.7 mm. Bill |
#29
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Yeah, I think I remember us reading up on the Porsche specs and feeling chuffed with ourselves that we came in within them..
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fastbug.net | FastTrack Dub Club "Straights are the boring bits that link corners together" |
#30
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Also, the Porsche specs (996) are set for the car going 175 MPH.
I just checked a recent Chrysler book and they spec 0.08mm lateral at the hub. That's almost 3 times what Porsche wants. And 0.13mm at the rotor. Bill |
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