85 to 95 Cam Gears 928 105 530 01 NLA - Update
#346
Three Wheelin'
Dumb question- has anyone taken both a new style & old style gear and had them Rockwell hardness tested? It would be interesting to see if they really are worth the increased cost,
not that these is any option at present.
not that these is any option at present.
Last edited by Jim Devine; 09-21-2011 at 03:20 AM. Reason: add
#347
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Roger,
my shop here in Germany says the same as you .He searched for a replacement for the gears and says Porsche use a special tooth divider so you need to much fabrication time.
Conclusion:Selling OEM cam gears.
my shop here in Germany says the same as you .He searched for a replacement for the gears and says Porsche use a special tooth divider so you need to much fabrication time.
Conclusion:Selling OEM cam gears.
#348
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Since I'm out of the country I've postponed my search, but am considering the cost to cut crank gears (being a very basic design compared to oil pump/cam gears) directly when I come home.
I'm sure you managed a more thorough search Roger, but its slightly comforting to hear that my problem is at least similar.
#350
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Heinrich - all about volume - they probably made more VW's in one month than the circa 50,000 928's made between 77 and 95. If I ordered 5000 instead of 100 the price would tumble dramatically.
Jim - we did the full comparison of old v new - cad drawings and all. Material was defined as well as the hardness. As already said the new gears are significantly harder than the old.
Jim - we did the full comparison of old v new - cad drawings and all. Material was defined as well as the hardness. As already said the new gears are significantly harder than the old.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
#351
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One of my sideline business efforts for 25+ years has been cutting gears....not for cars but for other 1 off sorts of deals. (antique clock replacement gears) I have looked at making the 928 cam drive gears, my equipment would certainly cut the space between the teeth without issue....however, speaking of the whole job it would require equipment I don't currently own...time could be rented on other machines but the volume of parts needed just does not justify the costs IMO.
To build a complete replacement there are several problems to solve 1) fixturing to correctly position the keyway in relation to the teeth, 2) cutting the keyway itself requires tooling I don't currently own 3) hard anodization would have to be contracted via 3rd parties 4)specifications needed of the aluminum used in the current Porsche supplied part, 5)testing and inspection of replacement parts would require specifications I don't currently have, i.e. hard anodization, how hard is hard?
I can see these being a $50 gear in say quantites of 10,000. But quantites of 10, or 100, or even 500, my numbers do not work. I agree with others however that Porsche is attempting to hit it out of the park with their current prices on these....they are I would think buying them in 500 or 1000 lots...or maybe they are committing to 10 at a time, hence the ugly prices...
opps, it looks like Roger has already covered several of my points while I was writing this....it is all about volume IMO and we can't drive enough volume to really reduce the price unless we can find a near identical gear from say VW that can be easily modified, and Roger is already all over that and not finding anything...
To build a complete replacement there are several problems to solve 1) fixturing to correctly position the keyway in relation to the teeth, 2) cutting the keyway itself requires tooling I don't currently own 3) hard anodization would have to be contracted via 3rd parties 4)specifications needed of the aluminum used in the current Porsche supplied part, 5)testing and inspection of replacement parts would require specifications I don't currently have, i.e. hard anodization, how hard is hard?
I can see these being a $50 gear in say quantites of 10,000. But quantites of 10, or 100, or even 500, my numbers do not work. I agree with others however that Porsche is attempting to hit it out of the park with their current prices on these....they are I would think buying them in 500 or 1000 lots...or maybe they are committing to 10 at a time, hence the ugly prices...
opps, it looks like Roger has already covered several of my points while I was writing this....it is all about volume IMO and we can't drive enough volume to really reduce the price unless we can find a near identical gear from say VW that can be easily modified, and Roger is already all over that and not finding anything...
Last edited by tmpusfugit; 09-21-2011 at 10:50 AM. Reason: add notes based on Rogers last entry...
#352
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Why not change perspective a little bit and use existing gears and make a belt to fit? Of course this means all gears need to be changed.
#353
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Dan
'91 928GT S/C 475hp/460lb.ft
#354
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Can't these things be milled on a CNC machine of some type based on a high res scan of an existing gear? I mean, they can rapid prototype stuff nowadays, isn't there some way to just put a blank of billet on a CNC machine, take a new existing gear, scan the thing and out comes a new gear just like it?
#355
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Can't these things be milled on a CNC machine of some type based on a high res scan of an existing gear? I mean, they can rapid prototype stuff nowadays, isn't there some way to just put a blank of billet on a CNC machine, take a new existing gear, scan the thing and out comes a new gear just like it?
And that still wont be a finished product.
#356
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Jim, would a "retread" be an option? Basically putting a new toothed ring on a core that has had its teeth machined down. That would take out all the machining work related to the hub of the gear. Is there a reason the retread gear ring couldn't be done in steel as opposed to hard anodized aluminum?
I have looked at making the 928 cam drive gears, my equipment would certainly cut the space between the teeth without issue....however, speaking of the whole job it would require equipment I don't currently own...time could be rented on other machines but the volume of parts needed just does not justify the costs IMO.
To build a complete replacement there are several problems to solve 1) fixturing to correctly position the keyway in relation to the teeth, 2) cutting the keyway itself requires tooling I don't currently own 3) hard anodization would have to be contracted via 3rd parties 4)specifications needed of the aluminum used in the current Porsche supplied part, 5)testing and inspection of replacement parts would require specifications I don't currently have, i.e. hard anodization, how hard is hard?
To build a complete replacement there are several problems to solve 1) fixturing to correctly position the keyway in relation to the teeth, 2) cutting the keyway itself requires tooling I don't currently own 3) hard anodization would have to be contracted via 3rd parties 4)specifications needed of the aluminum used in the current Porsche supplied part, 5)testing and inspection of replacement parts would require specifications I don't currently have, i.e. hard anodization, how hard is hard?
#357
Can't these things be milled on a CNC machine of some type based on a high res scan of an existing gear? I mean, they can rapid prototype stuff nowadays, isn't there some way to just put a blank of billet on a CNC machine, take a new existing gear, scan the thing and out comes a new gear just like it?
Even still the data has to be verified by a human, and that takes time and skill, both of which cost money.
So they make half a dozen paperweights to get it close. Then someone has to test fit the latest version on an engine, and compare to original fit.... then take it back and forth a few times with a few more versions...... at some point you get a set you can actually use... then you get them hard anodized..
Then you can start cranking out production. Good material isn't cheap either.
#358
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Jim, would a "retread" be an option? Basically putting a new toothed ring on a core that has had its teeth machined down. That would take out all the machining work related to the hub of the gear. Is there a reason the retread gear ring couldn't be done in steel as opposed to hard anodized aluminum?
As far as bonding a steel sleeve on the aluminum hub, hight temp loctite might do the job. No easy way to mechanically bond the two metals. A shrink fit in thin metal is usually not a good idea, and both the sleeve and the hub will both end up very thin. How thin I need to investigate. My first opinion is there is insufficent metal whickness to "do the job" but further inquiry is needed. I have an old set of16v pulleys to mess with, perhaps I should set forth and do so?
#359
928 Collector
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If we get a good process, we will never again need this work. In other words, sourcing aluminium gears is not a problem. every 928 has a set right? Just use existing cores (as is done for rebuilt water pumps). They already fit all our engines - oil pump; crank etc. I must say that the worst wear I've seen is on crank gears. The other gears tend to become sharp and cut timing belts, but the steel ones will be a different story.
Even if a set of cam timing gears is bowed, it should be possible to machine them again, and then hard anodize. At that point I'm not sure if there should or should not be a surfacing of teflon .
Even if a set of cam timing gears is bowed, it should be possible to machine them again, and then hard anodize. At that point I'm not sure if there should or should not be a surfacing of teflon .
#360
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And it may be that it wouldnt be an option for the 32v engine because the exposure to big dollar damages if it fails, but on the 16v, no big deal. At least in the testing phases.