Bevel gear markings

[Paddy]

I have to say i am new to singles being a twins bloke...sorry but i sort of assumed that the bevel gears were interchangeable. Obviously matched pairs is ideal but 50 years down the line there are going to be a lot of rebuilt engines and replaced bevel gears.
Is there really any way to tell what gear and what markings go with each other or what engine and what crank ?
For example:



I have up shafts and cam bevel gears up to 90 degree difference ? Is there some sort of rule of thumb ?

Thanks
Paddy

[DewCatTea-Bob]

____ There have been past threads covering this stuff before, so perhaps you'd have luck searching for one.

[quote= Paddy ...
" i sort of assumed that the bevel gears were interchangeable. Obviously matched pairs is ideal
Is there really any way to tell what gear and what markings go with each other "

____ Mismatched bevel-gears, (if they will mesh at all), rob power whilst also wearing-out each other ! _ So they're not so very interchangeable.
__ When the factory matched-up a pair of bevel-gears, they would then marry them as a 'matched-pair' by placing a grind-mark on them both while they were held meshed-together.
So to identify WHICH b.gear was meant to go to another,, (sort-of like comparing 'finger-prints'), ya try matching-up the grind-marks to see that EVERY tiny scratch within the grind-mark (on both gears), as well as the grind-mark's outer-boarder, all perfectly align-together, so as to then be sure that the pair of b.gears in-question were actually an original 'FACTORY-match'.
If the grind-marks' outer-boarders don't obviously tip-off that they are not a 'match', then further-scrutiny with a good magnifying-glass will likely be needed.


Hopeful-Cheers,
-Bob

[Paddy]

Yea i take your point about the grind marks but it would still be easy to get a matched bottom set and a matched top set that didnt work together so if you are buying a replacement top set you will not know if its any good until you line up the D drive and check.
Oh well i have a set that works on my little Elite engine but i had planned to sell the other spare sets i have but i can see they are pretty worthless until the buyer checks them on his set up. Looks like i will keep them.
Cheers
Paddy

[Eldert]

i put some pictures up of diff. bevelgears in the : making changes in a 24 horas thread on page 3

Eldert

[DewCatTea-Bob]

[quote= Paddy ... but it would still be easy to get a matched bottom set and a matched top set that didnt work together "

____ How could that even be possible ? _ As they ALL have just the very-same ONE-single 'D-tooth' !


" so if you are buying a replacement top set you will not know if its any good until you line up the D drive and check. "

____ I'm afraid I don't get what you must mean,, cuz as far as I know, they're all the same. ... When set for at TDC, they-ALL then have their D/slot-faces aligned to&fro (parallel along-with the motor-casing gasket-seams), unless the employed crankshaft-gear doesn't happen to have it's timing-dot aligned with it's key-slot, (as can be noted in Eldert's pic).


" i had planned to sell the other spare sets i have but i can see they are pretty worthless until the buyer checks them on his set up. "

____ But they should actually indeed fit any-other as well, (just as well as any store-bought roll of toilet-paper fits it's intended holder in ANYone's bathroom) !
__ It seems that your seemingly NON-issue needs to have YOUR-viewpoint better-explained.


Hopeful-Cheers,
-Bob

[Paddy]

Maybe i am being thick here but if it was just down to TDC and the D drive you wouldn't need to mark the gears.

Lets say you have the piston at TDC the crank bevel dot lines up with the bottom bevel dots, The D drive is front/back parallel.
You then have a choice of these two shafts. Both are sitting with the d drive horizontal but one has marks at 6 o'clock and the other at 11 o'clock. That is going to throw you cam timing way out is it not ?



Put simply the top pair will not work with the bottom pair, how can they if there are variations between all markings and key and d positions.

I dont see why they didnt keep the dots in the same place to the key ways and d drive faces.

As i say..maybe its just me .

[DewCatTea-Bob]

[quote= Paddy ...
" You then have a choice of these two shafts. Both are sitting with the d drive horizontal but one has marks at 6 o'clock and the other at 11 o'clock. That is going to throw you cam timing way out is it not ? "

____ NOW your particular point has been clearly brought to light. _ I've never before seen any tower-shaft with a timing-dot not placed in the normal-position !
Of-course one of those bevel-shafts would lead the camshaft to be out of time with the crankshaft.



" the top pair will not work with the bottom pair, how can they if there are variations between all markings and key and d positions. "

____ They COULD still be made to work together of-course, if you simply ignore the incorrectly placed timing-dot, and place your-own timing-mark on the correct-tooth.



" I dont see why they didnt keep the dots in the same place to the key ways and d drive faces. "

____ I certainly agree, and don't have THE answer for why such inconsistency has occurred.
Do you know for sure which Duke-model the odd tower-shaft came from ?


Disconcerted-Cheers,
-Bob

[Paddy]

OK thanks Bob
You can see why i was confused because this is my first ever single build after years of twins and i had 2 different bottom bevels and 2 different bevels on shafts. I guess i am just unlucky . An way i sourced a complete 250 set of bevels and all is now fine
this is a better picture of the problem i had with dots at 8 o'clock



And this is my engine so far










Tank has been re chromed and is at the sprayers now allong with all the other paintwork


I assumed when i said bevel markings at the start of this thread, being new, that it was known there was a problem with more than just the crank bevel.my apologies for not making things a bit more clear
Thanks
Paddy

[DewCatTea-Bob]

[quote= Paddy ...
" You can see why i was confused because
i had 2 different bottom bevels and 2 different bevels on shafts.
this is a better picture of the problem i had with dots at 8 o'clock "


____ Thanks for adding the comparison-pic, so I can now see for myself !
The upper-left bevel-shaft appears to be a normal-example, while the one underneath appears to have it's incorrectly placed timing-dot filled-in with putty (perhaps in some-kind of attempt to correct it's mistakenly-placed location).
With a std.normal bevel-shaft placed as-if held in it's normal/working-position (and 'timed' at power-stroke TDC), and looked-at directly from underneath (with X-ray vision),, a correctly-placed timing-dot should be located centered-over (& just outside-of) the D-tooth, in-towards the inner-side of the engine/top-end.
In other-words,, if the tower-shaft is rather-instead laid-over horizontal with it's D-tooth's round-side faced-upward between 9 to 3 o'clock, then the timing-dot should be located at 12-o'clock ! _ OR likewise, if the shaft is laid with the D-tooth's flat-side faced-upward (with the round of the tooth occupying the space between 3 to 9 o'clock), THEN the t.dot should be located at 6-o'clock (as the shaft is laying-over flatly) !
(Let me know if all-this doesn't help.)



" I assumed when i said bevel markings at the start of this thread, being new, that it was known there was a problem with more than just the crank bevel. "

____ No, I don't think-so,, I much doubt that anyone of us registered here, has ever before chanced-upon a bevel-shaft with it's t.dot miss-located any at all.
But even if armed with such knowledge, your post still certainly seemed to be clearly concerning the fairly-common concern about the relative importance of factory-MATCHED bevel-gears.


Enlightened-Cheers,
-Bob

[ecurbruce]

Bob, (or anyone else),
How is that gear attached to that shaft, and could they have been disassembled and reassembled in the wrong place?

Bruce