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Valve timing

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AJW19/11/2018 19:11:06
289 forum posts
117 photos
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'?

Jon Lawes19/11/2018 19:53:06
371 forum posts

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.

JasonB19/11/2018 19:56:40
18122 forum posts
1996 photos
1 articles

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

MichaelR19/11/2018 20:00:45
374 forum posts
79 photos

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.


geoff walker 119/11/2018 20:18:49
412 forum posts
159 photos

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.


AJW19/11/2018 23:05:08
289 forum posts
117 photos
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?

JasonB20/11/2018 06:57:45
18122 forum posts
1996 photos
1 articles

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

AJW20/11/2018 10:16:19
289 forum posts
117 photos
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.


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