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Camshaft availability.

Brampton Bryan

New Website User
Non-VOC Member
Can anybody tell me what options are open to us.
I have tried our trusted friends at VOCSpares at Lymm only to be told that there have been none available for the last two years and no signs for the future.I asked if there was a drawing available to check timing mark orientation(answer was no),it seems that cams have moved relative to the pinnion on many occasions is this a design weakness ?
Have the club just built a complete new machine from new parts but with reclaimed cams in then?? Garry Robinson reclaims cams using Stellite 12 and stellite 6 for the followers with great results and welds them to avoid movement if the interferrence is insufficient.He also makes new camshafts. How many other options are available to us. Can anyone help.
Thanks, Bryan.
 

derek

Well Known and Active Website User
VOC Member
cam availability

I have also just tried to obtain cams, and eventually sent some to Gary Robinson for reclaiming, as I also want a new cam wheel, he stated that they were best obtained from Maughans (which he would do on my behalf) with the correct ground fit too suit the shaft, he would inform Maughans of the size. Seems good to me.
The spares Co., have had the cam blanks at a firm for grinding for, as you state , a couple of years. I do not see why they can not use Maughan or Gary Robinson.
 

Vic Youel

Well Known and Active Website User
Non-VOC Member
Cam Drawings

I also wonder whether the drawings project has made drawings available for the various cams.....does anyone know? Have cams been manufactured in accordance with these drawings to test them?

Further......what drawings/designs do Gary Robinson and Maughan's use.

What is the origin/design of the cams which the club shadow utilises?

Lot's of questions here. Would make interesting reading if an MPH article to update previously published information was composed by someone "in the know."

Cheers

Vic
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Cam designs

PEI explains where his cam designs came from in FYO (and in his autobiography). There wasn't a lot of science involved, largely because he found he had to produce cam masters at his leisure, so long as they were ready in about 30 minutes. Gary Robinson 105 cams have some connection with Ian Hamilton that I can't remember. Ian designed them? Modified another design? Commissioned them? Doubtless there are details in Ian's MPH articles. What I remember Gary saying is that they are basically Mark II's with less overlap, and that many users think there's less spitting back as a result. I can't say I'd noticed, which isn't to say it isn't true.
From observation, Vin cams are look mild, similar to Rudge Special cams ("Special" means "Very Ordinary" in this context). Rudge Replica cams, which I use (in a Rudge Ulster), are two near-parallel flanks with a base circle at each end - like the classic description of a Manx Norton cam: a housebrick rotated off-centre. They (Replica cams) work very well. I half-expected a buzzy engine, but in fact it pulls like a train from zero revs to god knows what. CR is about 7:1. I suppose that having two small valves to shift rather than one big one gives more opportunity for aggressive valve acceleration rates.

Stepping back a bit, a Rapide produces 45 bhp, 22 1/2 bhp per pot. That isn't exactly radical. As noted elsewhere, the legendary Guzzi 500 cc plonker, the Gambalunga, named for its long stroke, originally had dimensions of 84 x 90. I'm not complaining: a big, softly tuned motor makes for a very pleasant bicycle at, say, 60 to 90 mph. I'd hate to lose that in pursuit of performance I'd never use.
 

bmetcalf

Well Known and Active Website User
VOC Member
Cam Design

Supposedly, the Emmerich/Andrews/Megacycle cams are "constant acceleration" design. Of course the acceleration has to change from positive to negative when the follower is between the base circle and the nose. This makes me think the term was more of a marketing term than an engineering concept.

I was a poor student, so I find it difficult to think of a way to describe the varying contact point of the cam and the follower that makes the valve motion more complex than a roller lifter in a US V-8. You could do it graphically every few degrees to try to optimize things, but the ideal motion might be impossible with the mass of the valve and the available springs.
 

Len Matthews

Well Known and Active Website User
VOC Member
Brampton Bryan raises an interesting point; if the Club/VOCSCo Black Shadow was supposedly built from all new parts, how come they have had no cams in stock for two years? What's more, I loaned an RFM to assist the Drawings Project-it has not been returned. How many others have contributed parts and /or drawings are still waiting?
 

BlackLightning998

Well Known and Active Website User
VOC Member
Isn't there a Club Officer in charge of the Drawings Project who could comment?

Vic and Len seem to be asking a similar question - isn't there someone in charge of the Drawings Project for the VOC who could provide a response?

Stuart



Brampton Bryan raises an interesting point; if the Club/VOCSCo Black Shadow was supposedly built from all new parts, how come they have had no cams in stock for two years? What's more, I loaned an RFM to assist the Drawings Project-it has not been returned. How many others have contributed parts and /or drawings are still waiting?
 

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