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which bevels? please note correction I have coniflex

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which bevels? please note correction I have coniflex

Postby steve c » Thu Apr 13, 2017 12:03 pm

building a Mk 3 engine 150 from junk of several engines , I think I have a set of coniflex bevels ( crowned straight cut gears very hard to see) but can not be sure they all the same set as the friend I got them from may have used the clutch pinion on something else. The engine came with helical ( slight curve to form) gears but the clutch had jammed chipping the clutch bevel, crank bevel and damaging a tooth on the rear pinion and rear crown wheel no damage to the kickstart bevel
I have a set of straight cut mark 2 bevels. Does any one know what you can mix and match and any foolproof of way identifying coniflex gears.
Lots of engines are totally worn out when you strip them so makes buying engines for the bevels a bit of a lottery.

One thought from Steve J later comment; can worn coniflex gears resemble helical profile slightly? helical gears in other applications are very pronounced I am only going on the vague statement in the parts book which is not linked to engine numbers as far as I can see. I may well be looking at worn coniflex gears.
Contact pattern test seems a good idea in my case.
Last edited by steve c on Thu Apr 13, 2017 6:16 pm, edited 2 times in total.
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Re: which bevels?

Postby jbcollier » Thu Apr 13, 2017 2:36 pm

You can't mix straight cut and helical cut gears. The 4-cam Porsche chaps do mix mismatched gears of the same type. They set up a special jig and run the gears together using polishing compound. Otherwise, Prussian Blue is your friend. Just set up the suspect gears as per manual and do a contact pattern check. If it is good, you should be fine. Check both drive and coast patterns.
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Re: which bevels?

Postby Steve J » Thu Apr 13, 2017 3:59 pm

The only straight cut crankshaft/clutch bevel gears I've seen have been the Mk3 17/25 teeth sidecar gears, but some of the earlier LDs apparently had the straight cut 19/26 teeth gear sets. The normal 19/26 teeth gear sets for the Mk3 LD are either helical or coniflex - I've only ever seen helical gears on the crankshaft & clutch bevels of an engine from a NSU Prima D (derived from the LC Lambretta), and there's no way that particular gear form will mesh with any other type of bevel gear form. I guess the majority of bevel gears on the Mk3 LD would be coniflex, and trying to get those to mesh with straight bevels is not something I would attempt. In the past, I have mixed & matched individual gears of the same form (probably coniflex) without issues, but it can take a long time to set the gears up by changing the shim washers. These days, I try to keep the gears together as a pair whenever I strip old engines, but I do still have a few odd ones...

If you've got a set of Mk2 straight cut bevel gears, you won't be able to use them with the Mk3 kickstarter - the Mk3 kickstart bevel gears have a larger bearing diameter than the Mk2 kickstart, and none of the Mk3 kickstart gears had straight teeth (apart from the 17 tooth sidecar bevels, which won't mesh with 26 tooth clutch bevel!)

Steve - PM sent.
Last edited by Steve J on Thu Apr 13, 2017 9:13 pm, edited 1 time in total.
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Re: which bevels? please note correction I have coniflex

Postby steve c » Thu Apr 13, 2017 5:53 pm

can wear to coniflex gears resemble helical profile slightly? helical gears in other applications are very pronounced I am only going on the vague statement in the parts book which is not linked to engine numbers as far as I can see. I may well be looking at worn coniflex gears.
Contact pattern test seems a good idea in my case.
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Re: which bevels? please note correction I have coniflex

Postby jbcollier » Fri Apr 14, 2017 1:41 pm

For a detailed description of bevel gear teeth:

http://www.sdp-si.com/resources/element ... /page4.php

(scroll down to "8.4 Forms Of Bevel Teeth")

An experienced machinist might be able to pick out a coniflex machined gear but I doubt mere mortals such as ourselves can.

You are either going to have to find matched gear pairs, or set up and test random gear pairs until you find a reasonable match.
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