Valve timing

[AJWParticipant @ajw]

Pressing on with my Centaur build I am about to produce camshaft with timing gears and cams.
I was considering securing the skew timing gears to their shafts with a grubscrew into a tapped hole in the bore/shaft joint – does that sound ok?
When it comes to the cams on their shaft I would like to be able to have some sort of adjustment, the drawings show these as pinned and hence fixed.
Shaft will be 3/8 in diameter and the Boss’s of the cams is drawn up as 3/4 in.
Any ideas with regard to an ‘adjustable fixing’?

Alan

[AJWParticipant @ajw]

[Jon LawesParticipant @jonlawes51698]

What about a vernier gear? different number of holes in two halves of the same gear, one indexed to the shaft and the other with the lobes on? or something of that ilk.

[JasonBModerator @jasonb]

I'd stick a grub screw in the boss so you have some adjustment and then when you have it running right change for a pin of put a flat on the shaft and keep the grub screw

[MichaelRParticipant @michaelr]

On my Centaur I used grub screws for the skew gears (not tapped into shaft) and the same for the cams, they have not moved at all during running.

Mike.

[geoff walker 1Participant @geoffwalker1]

http://www.plans-for-everything.com/hen_steam_engine_plans.html

Hi Alan,

Have a look at the above website.

Scroll down until you see the JEPSON engine.

Download the drawings and have a look at the adjustable cam design.

It is a simple "pinch" clamp, very effective, Takes a little time to make but much better than a grub screw.

Geoff

[AJWParticipant @ajw]

Thanks guys, I like the idea of the Nelson eccentric clamp but don’t want it to get too bulky and obtrusive.
Depending on how much space is available I could consider a tapered collet type setup although as Jason says, once it’s setup it will stay setup so the simple grubscrew changed for a pin later sounds the simplist.
What do you think about the ‘end on’ grubscrew in the gears/shafts as any adjustments would be made at the cam end?

Alan

[JasonBModerator @jasonb]

If you do it at the gear end then you will only be able to adjust the cams as a pair not individually. Key the gears or at least have them solidly fixed.

 

Edited By JasonB on 20/11/2018 07:20:42

[AJWParticipant @ajw]

What I meant was! Fixing the gears to their shafts (not adjustable) then, as the cams are independent of each other, making any timing adjustments at that end.

Alan

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