Bevel question

[Jordan]

I understand about the ground marks ex-factory. I owned some nearly new singles in the early '70s, and discovered the grinding marks, which at the time were puzzling.
I guess the final disassembly to clean out the grinding dust could be avoided. Just don't grind them, until it's time to dismantle again!

[DewCatTea-Bob]

[quote= Jordan ...
" I understand about the ground marks ex-factory. "

____ When I first responded to your previous-post's question - "Is all that correct?",, I then shouldn't have assumed that you had any specific doubts concerning your understanding (of the included wording you copied from a previous thread-post's claims) as seemingly being in some possible conflict with that which Nigel & I were meaning to state,, and-then without me replying with such biased-thinking, I rather simply should've replied with: 'yes'.
But then, the additional related matter I included, wouldn't have gotten brought-up & further covered, and the exact difference between "machine-ground"* and 'ground-surface' & 'grind-patch' wouldn't have gotten covered so specifically. _ Which is why I left my direct-response post as it was posted and rather went onward with another-post (inspired by Kev's post), to bring-up how post-writers & post-readers have-to more extensively consider matters of post-wording when considering the chosen-wording's intended interpretation. _ (Which is an ongoing problem because people don't always care to keep their written-English properly-termed consistently.)
So anyhow, the statement "The best mesh might result in the machine-ground outer surfaces of the mated gears NOT to be level with each other." certainly makes fine sense, since it's (well chosen !) statement-wording is-not at all in any reference to the factory-added 'grind-patch' markings !
(* Meaning the machine-grinded regular outer-diameter/level(s) of the bevel-gears's teeth, [rather than the factory-hand added grind-patchwork's mated-level].)



" Just don't grind them, until it's time to dismantle again! "

____ After being positively-SURE that one's-own bevel-mating work is at least as good as the factories, a leveling grind-mark could THEN be added (with a strong vacuum near-by to suck-up the grinding-dust).


Dukaddy-DUKEs,
-Bob

[Jordan]

Yes, I think I should have started with definitions for the terms I used.
But you got correct what I meant, Bob.
I wanted to be sure that there's nothing inherently right about the (what I called) machined surfaces being level with each other. The machined surfaces being of course, the conical outer edges of the bevel gears. They were probably a feature of blanks spat out of a machine with fairly wide tolerances, before going to the Gleason.
It was a while before I appreciated the advantage of hand-grinding across the edges. It leaves a unique "fingerprint", confirming a matched pair as well as aiding correct re-shimming.

The Creasey article on shimming is OK, but the illustrations about bluing don't make much sense to me.
For example, the black marks as printed - do they signify where the blue is, or isn't? Not enough info given on this crucial point.

Jordan

[LaceyDucati]

Jordan

I looked at the Creasey article pics and thought them a bit misleading. The drawings I guess are lifted from somewhere else and show a straight tooth anyway. There is a better picture found in a guzzi manual for the drive box shimming as seen on page 75 on this link. It's a copy of what is found in all the Guzzi manuals,
this is from one of Mick Walkers books.

http://books.google.co.uk/books?id=wsox ... ar&f=false

Probably a bit idealistic, but clearly shows what you are aiming for.

But as has been said before, if they are a matched set then there is little if anything to be gained from getting the engineerers blue out. Leveled across the hand ground marks they are usually right.

Regards Nigel

[Rick]

Jordan,
The dark patches in the Creasy article show the contact patch- where the teeth touch. Some guys paint one gear and look for a patch of paint to be transferred onto the other gear, but I think most people paint both gears and look for the area where the paint gets rubbed off. You can use machinists' blue layout die, but most guys prefer GM yellow 'gear paint'.
Helical bevel gears sort of 'seek' the correct mesh- if you hold them in your hand and try to rotate them when they're grossly misaligned they'll push each other into position.
The pros at this are the people who do automotive differential ring and pinion gears. They worry about the 'drive vs coast' side of the gear, and tell me the coast side is the more important when setting up used gears, but I've never heard an explanation for why that's true.
To me, they look like a big gear in relation to the load they're driving- I've examined a few sets from singles and twins and never seen anything that looked like wear.
Rick

[Jordan]

Thanks Bob, Nigel & Rick.

Can you please give a pointer to the GM gear paint? I can't find it.
Is it easier to use than engineers' blue?

Jordan

[LaceyDucati]

Jordan

I just put "GM yellow gear marking compound" in google and lots of suppliers dropped out. Put it in google images and lots of interesting pics there.

Mind you looks hellishly messy to me, wondering how one would clean it off in situ? Unless you are going to strip the engine to clean it and then rebuild it I'ld rather stick to engineers blue. I don't know what the consistancey of it is like and weather it sets, but I'm having images of a big yellow bit of snot stuck in an oil way In a sealed drive box this is probably not an problem. Maybe it disolves in engine oil, maybe someone else here knows.

Just my thoughts.

Regards Nigel

[Rick]

Jordan,
In the US it's usually called 'Gear Marking Compound', and Nigel founk it in the UK, so it shouldn't be hard to find- here is the Amazon listing for yellow, and another compound in white.
http://www.amazon.com/General-Motors-Ge ... ar+marking
http://www.summitracing.com/parts/rmg-5500011
Before you buy yellow or white marking compound try ordinary machinists' blue dye, like Dykem, and see if the pattern shows up OK. I often use broad tip felt tipped pens instead of Dykem- the Dykem brushes are messy and the bottle is amazingly easy to spill all over your bench.
I've done this on large industial gearboxes, but never on a Ducati engine- I'll give it a try sometime- probably a waste of time, but if I found the contact was way out I'd be glad I checked.
And finally, here is a document that goes into gruesome detail on the process- the contact pattern stuff starts on page 22.
http://www.pirate4x4.com/tech/billavist ... _Setup.pdf
Rick

[Jordan]

I see it now.
I'm interested in the GM yellow, as being a little colour-blind, the greater the contrast the better.

That 4x4 article is a comprehensive description of the car rear axle gear shimming, that I quickly browsed through and saved for future reference - thanks.
The author points out the importance of keeping original sets of crown gear and pinion together - they are marked with numbers. A mis-matched pair will never be able to be shimmed correctly. Why would that be, I wonder?
No doubt a hypoid rear axle that transmits hundreds of horsepower would be more critical than a cam drive bevel set.

Jordan