Slant gears?

[vintagengineerParticipant @vintagengineer]

[vintagengineerParticipant @vintagengineer]

I am rebuilding a 1914 petrol engine that has twin cams. One of the timing gears is missing. I need to make a replacement, I have measured them and they appear to be cut at an angle of 14 1/2 degrees but are straight not helical.

I assume I can cut the gear the same as straight spur gear but at the correct angle.

Anyone has come across this type of gear before?

[HopperParticipant @hopper]

Yes, but I made it myself. Works well as a wormwheel on a dividing head, meshed with an Acme thread of suitable pitch. I made it just as you say, same as a straight spur gear but mount the blank at the suitable angle. No idea how it would go meshing with another gear rather than a worm.

[John Stevenson 1Participant @johnstevenson1]

If they are cut AT AN ANGLE of 14 1/2 degrees then regardless they are helical

[Phil PParticipant @philp]

Can you put us a close up photo of the gear in question please.

I doubt very much it will be an angled gear as you describe and think it probably is a helical gear, but I would be very interested to see it all the same.

If teeth were cut at an angle across a gear blank, they would be shallower at the sides and deeper in the middle, I don't think that would make for a very good gear if it has to mesh with another one the same.

The only time I have seen this type of gear in use, is as an alternative to a true worm gear on a cheap dividing head, but in that application it is only the centre of the teeth that have contact with a worm and you can sort of get away with it.

Phil

 

PS. Hopper and JS both type a lot faster than me !!

Edited By Phil P on 16/02/2017 22:21:18

[vintagengineerParticipant @vintagengineer]

I will post some pictures tomorrow. They are cut in a straight angle ( I have clocked them to confirm this) rather than a helix and they alternate lefthand – righthand so that they mesh. But because of the angle they have thrust washers on all the gears.

[John Stevenson 1Participant @johnstevenson1]

It's a bit like 20 questions isn't it ?

[vintagengineerParticipant @vintagengineer]

[John Stevenson 1Participant @johnstevenson1]

That is a helical gear.

I'd suggest that you get hold of a copy of Ivan Laws fine book Gears and Gearcutting, No 17 in the Workshop practice series and all will become clear.

[vintagengineerParticipant @vintagengineer]

Will do, thank you.

[HacksawParticipant @hacksaw]

Now tell us what the engine is ! Alfa?  , Peugeot

Edited By Hacksaw on 17/02/2017 22:50:19

[vintagengineerParticipant @vintagengineer]

White and Poppe / Dennis Brothers Motors. Customer cannot get an exact date but we think its a 1914 engine as it has some W+P parts and some Dennis parts. 5 litres, 4 cylinder T head.

[HacksawParticipant @hacksaw]

I've got a Dennis ..a 36" Blackburn 500cc beast !

[John ReeseParticipant @johnreese12848]

There was a post within the last year or two dealing with cutting helical gears. I searched but could not find it.

I responded to it stating that the traditional method was to use a universal mill (table swivels) and a universal dividing head geared to the lead screw. Several members responded with work-arounds devised by model engineers to cut helical gears without the specialized equipment. I searched for that post but was unable to find it. Perhaps another member can post a link. I think you would find it useful.

You might need to search for a commercial gear shop that could do it on a hobber.

[Anonymous]

Posted by John Reese on 19/02/2017 16:17:36:

There was a post within the last year or two dealing with cutting helical gears. I searched but could not find it.

Here:

**LINK**

And for reference the 'traditional' way:

And less conventionally on a vertical mill:

Neither of these methods produce the correct tooth form, although for many practical purposes the gears work well.

Andrew

[Author]

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