Centaur engine timing gears

Mention of using stock gears from HPC here

What do the plans call for? (I dont think it makes a difference, but you never know! )

Edited By John Rudd on 02/09/2018 20:29:01

I think they are right hand, could not see it mentioned in the ME articles

Left or right would alter the direction of the camshaft so you would need to bear that in mind when timing the engine

Looking at a picture of the engine they appear to be RH. Ideally they would be arranged such that the axial forces on the gear are resisted by the larger bearing surface, whichever one it may be.

Andrew

I built the Centaur and when I came to fitting the skew gears I found that the gears supplied by Reeves were to big to fit on the cam shaft.I had to mill a cavity in the side to allow the gear to mesh properly,this cavity was nearly through.When selling castings and parts for the engine the supplier should ensure that they are correct,this was not a mistake, they told me if I wanted gears to fit I would have to look for another supplier.It,s a nice engine to build .

Frank

Edited By AJW on 03/09/2018 17:15:40

I'm not sure that the criticism of Reeves is justified. ETW specified skew (helical) gears that had differing helix angles ( approx 60 and 30 degrees) such that they were the same diameter. This allowed the gears to fit nicely in the space he designed (probably ! ) The only readily available helical gears are 45 degrees so a compromise has to be reached. If you have found 45 degree gears that fit then it is possible that the gears will be too small for the load they have to carry (but I doubt it). Basically, Reeves have offered one solution (perhaps the same DP as the original gears but both 45 degree helix angle rather than a 30/60 pair). You have chosen a different solution - neither is correct according to the original design.

Cheers,

Rod

Alan,

As you know, ETW was, in fact, very vague about the size of the gears and we can't be sure that he got it right. I made the "correct" skew gears for my Wyvern and still had to relieve the bracket to give clearance for the driven gear to rotate. I still revere the man though and I'm sure you will end up with a splendid engine.

Enjoy the journey,

Rod

What you need is a pair of gears like the ones in front of these castings.

My dad made those many years ago on his CVA hobbing machine.

Phil

I suppose for those without the equipment to cut them you could draw them up in cad and send off the files to be printed in one of the sintered metals or LWC. They ar enot taking a massive load or going really fast.

Or make up the jig that Chuck Fellows came up with to allow you to cut them on your home mill.

If you did make them yourself you could probably get the drive gear bigger than the driven with the right helix angles and this may actually be what is shown on the cover illustration. I just had a look back at the photos of teh 1/2 scale Domestic that I made and the 6T crankshaft gear is a larger than the 12T driven camshaft gear 

Edited By JasonB on 04/09/2018 07:51:32

.

I followed that hint, Jason, and also found this : **LINK**

https://m.youtube.com/watch?v=oSeMX9SZXXY

Very impressive ... Thanks

MichaelG.

There is also this video of the same set up by George Britnell

https://youtu.be/blaZ5tz0_6E

Drawings and a couple of threads about it can be found on MEM forum, may need to be a member to get at the drawings. 

Edited By JasonB on 04/09/2018 07:55:44

.

Thanks for the extra video link, Jason

may need to be a member to get at the drawings.

... do you think they would let me in ?

For suitable gears for your gas engine, you might look out for unwanted sewing machines. Not too old. My daughter discarded one. Naturally I had it to bits to see if there was anything useful inside. Not really, except for a pair of 2:1 helical gears! One is brass and one steel. They are both a fraction over 3/4” diameter, and 3/4” working centres. The steel one is 13/16”. long with a half inch bore that fits my crankshaft perfectly. The brass one is 3/8” long, and 15/32” bore. I have not yet compared them to the drawings, as this is a “back burner” project that I inherited from an old friend; but they look a better bet than the ones that came with the castings.