ET: Engine (Twin) ET48 Mag/ATD Pinion

[royrobertson]

Hi Vic, As you can see mine are split in two and no larger than a steel Comet one. Are you saying Comet ones are no good for a road bike and should be Alloy? Did you think of Stainless? After all our pushrods are stainless. Even my racer has hollow stainless with hardened steel ends and they never require adjustment.
Cheers Roy

 

[Nigel Spaxman]

My ATD pinion was supplied by Coventry Spares. It is a fixed one that drives an electronic ignition. Maybe the load is a bit less than if it drove a Magneto. It is a black plastic material and it has lasted for about 20,000 miles with no noticeable wear. Whatever material it is made of it seems to be really good for this job.

 

[Bill Thomas]

The one The Spares Company now sells is called Acetal ?,
Cheers Bill.

 

[oexing]

Roy, its not a thing of length of pushrods or spindles that is my concern. Just that the engine case is alu with all positions of spindles and camshafts. When you mount a steady plate over them that is not alu , positions will not remain same as alu got twice the expansion than steel, stainless is a bit better but still way less. So in effect there will be side loads on spindles and shafts, so no longer perpendicular like in cold condition - unless you can work out all positions in engine case in hot condition and machine holes in steel plate for hot state . Not soo easy to do, on a mill with DRO allright to find positions, with hot case then. So for a workaround I just got alu 7075 and no more worries about heat growth. I could not see much of advantage in steel, so no headache. You got two part steady plates , a bit better maybe. I prefer one piece plate and not much of windows in it, looks more solid to me as less flexible from loads. But don´t ask me for calculations about this matter, I am quite useless in maths of that kind.
Stainless for pushrods is better than plain steel but still not quite to the point. We got all alu engine components in Vincents. Allright, the pushrods are very short, that helps. But you really want alu for keeping valve clearance in hot engine as good as possible for enjoying the quieting ramps on cams - if there were any with original . That is the reason why you set nil in cold engine as this is all you can do, no negative "clearance" possible. Sure, there is more than one place in the engine that can be noisy but once you know about this aspect you may want to improve things if you can.

Vic

 

[oexing]

Actually, when calculating heat growth for spindles distances it is not quite so bad as I was expecting. With engine temperature at 80 degrees C in operation you´d see a plus of 0.20 -0.30 mm for crank case in alu. That means the steel steady will do half of this , 0.10 - 0.15mm . My guess then, the fit of holes in the steady plate for spindle ends might be not quite so perfect in the real world. So that side load from heat growth will be concealed somewhere on the way somehow. In effect this can be seen as a more academic discussion when associated with vintage bikes - and I am not one of them , I mean academics .
Sure, the job of the steady plate was initially to support the free ends of all spindles. But how can you achieve this with an old engine and replaced spindles ? I had the timing side on the mill to measure up positions as they actually were for fabricating new alu plates. But how do you deal with this at home - no simple thing when shifting the large idler around for good mesh with camgears ? Another place for improvisations to put it nicely .

Vic

 

[litnman]

Vic, I hope you show a video of this engine running. It looks very impressive.

 

[royrobertson]

Hi Vic, as you say It's all academic when you work it out and using gauge plate (a ground tool steel) means even with the extra holes in it, it is very unlikely to flex. I would have used stainless plate now as the coefficient of expansion is closer to alloy but I had access to gauge plate at work. I have seen over my 55 years of Vincent engine ownership many clapped out and destroyed Ally steady plates mostly from overtightening of the nuts or loose spindles. I have even seen wavy ones or ones that have grabbed the spindle ends or indented where the washers go. Perhaps the ally you are using is tougher and in theory it is the right material for the plates and pushrods. However my setup has given no trouble even going back to my Norvin days. Titanium is not the material for things like pushrods, as I found out. I did make and use successfully crankcase and cylinder studs plus as many nuts as possible using Titanium. All for weight saving on my racer.
Cheers Roy

 

[oexing]

Roy, great photo, you are enjoying yourself I guess ? I am getting slower in the brain all the time so no racing activities ever done. My target with Vincent B types is to have them less noisy and reliable working. Next matter is having good brakes for modern road traffic - working on that these days. Finally I try to keep weight under 200 kg for old age . So when I found titanium at lower prices I did a few parts in titanium for the joy of it. But weightwise this is minimal effect , anyway, it is some satisfaction once you can hold shiny new parts in your hand. Well, once toolmaker it is hard to keep yourself from messing around on machines .

Vic
titanium Brampton spindles

 

[Marcus Bowden]

Vic my handsome, I must say that those spindles look to be the dogs bollocks with hexagon end ? what size hex? where can I buy bright stock like that ? 7/17", 1/2", 9/16" as I've always made my own spindles. What grade is suitable as I've never used it before ?

 

[timetraveller]

For those who are not familiar with Roy Robertson's efforts it should be realised that Roy is not a wealthy man. Someone gave him a sheet of titanium and Roy cut it up and eventually machined it into nuts, small bolts etc The amount of work was enormous. The man is a hero.