Silk Scott racer project – the return of the frame tubes

I’m not sure that would make a successful Hollywood title but it sure as hell excites me!
I don’t know whether everyone does it but I carry moments of regret through life somewhere buried in a dusty box in the corner of my brain. They spill out sometimes and I go through an internal process of closing my eyes and shaking my head side to side as I remember the feeling. It is largely pointless of course as the moments are long gone.
The bike(s) I shouldn’t have sold, the engines I shouldn’t have blown up, the Rolls Royce I shouldn’t have crashed (it wasn’t mine.. I was working as a mechanic in New Zealand and being towed to a garage) and definitely in the mix.. the Silk Scott frame I shouldn’t have cut the front tubes out of. Putting the fact that it wasn’t going to be easy to swap engines without doing something ‘detachable’ aside… the Silk Scott sat rather forlorn for at least 10 years until I started looking at possibilities last year. It’s not finished by any means but Alan (Noakes), who’s been working on the detachable cradle has got a loose assembly together now. he just sent me the pictures: This is how Christmas should feel.

My initial sketches
My initial sketches
Frame connectors
Frame connectors
loose frame assembly 001
loose frame assembly 001
Frame loose assembly 002
Frame loose assembly 002
loose frame assembly 003
loose frame assembly 003

The next step is to braze the lugs up.

So that’s what Alan has been doing!

What have I been doing?
I’ve stripped the weighted cranks out of the crankcase my dad machined for the Silk Scott as I need to do some final work on the gas flowing on the transfer and inlet passages (I love doing this.. stick a MotoGP DVD on and needle file for hours). I’ve also written to Rex Caunt, an ignition expert, to get advice about the process of setting up a charging system using the ring of magnets on the side of the flywheel.

It’s all too much. I’m off to bed.

January 2015 – Progress report

Well, we are moving in the right direction (I think) but I’ve a lot of ambitions this year so we’ll see how it works out…

Last weekend I decided to drive up to Leicestershire to see Roger and to help him improve security at his place, following the break in the previous weekend that resulted in the theft of a Yamaha RD 350 LC YPVS F2 (the one I had when I was 18 years old.. 25 years ago). He’d bought lights and I bought an alarm system and over the weekend we fitted it all and made the best of a bad lot.
I love being in the workshop and he’s still pushing forward with improvements to machinery and tooling, the latest being a DRO on the beautifully made Smart and Brown 1024 VSL lathe. You don’t need them, but they do make life easier and quicker.
It’s also good to be surrounded by his Scott engine work and I think we help motivate each other to do the best we can to make sure that our racing Scotts are in good competitive order for riding this year.
Sometime on Sunday morning we had a visit from Eddie Shermer, the editor of ‘Yowl’ (journal of the Scott Owners Club) and a skilled engineer in his own right. He and his wife also put great energy into organising the annual ‘gathering’ of the Scott Owners Club held at Abbotsholme School in Staffordshire.

Eddie Shermer, Roger and Thiel 158 universal jig mill. They were smiling until the photo!
Eddie Shermer, Roger and Thiel 158 universal jig mill. They were smiling until the photo!
Eddie does a lot of Scott transmission work but also takes on complete engine rebuilds too, and came to discuss possible solutions to a particular problem he’d encountered with a crankcase. It was good to see him and always interesting to discuss the engine issues.
In fact, I kept a Scott line going through the weekend because I’d arranged with Alan Noakes in Lincolnshire that I’d take the Silk Scott frame up to him so that he could make a start on the frame connectors. Lincolnshire is hardly on the way back to Devon, in fact around 2 1/2 hours in the opposite direction, but it meant that I could see Alan and chat through some of the details and also see some of the things that he is working on. He had some hardened and ground clutch hub centres as well as pressure plates that he’d made on the bench, and also a very compact roller starter that he’d even cast the rollers for. Very impressive.
Anyway, I couldn’t stay long as I had a 6 1/2 hour drive back home! Just back by midnight.

This last week, I’ve removed the carburettors from the Super Squirrel as I need to make some modifications for the return to petrol. I never had the twin carb set-up developed for methanol anyway (switching back to petrol this year) so it’s not something that I wouldn’t have to do anyway. The two carbs are Amal 276, but are of different bore sizes at the moment. I need to get them bored out to 1 1/16″ and also have some short inlet ‘trumpets’ made. They won’t be very trumpet like, but will just have a better radius for the air flow.
I’ve also got some ‘K-type’ thermocouples which I want to fit to the exhaust, fairly close to the exhaust manifold, to give extra information when I take it to so a dyno setup when the inital carburettor modifications have been done. Petrol will make everything run hotter, and I’ll need to be careful to try to make sure that I do what I can to make sure that I’m not overheating the piston. I may also fit a temperature sensor to a spark plug to read that, as well as coolant temperature to see whether the small radiator is able to shed heat. It’s possible that I could pressurise the radiator to help the situation, but it might not be necessary. I also have a slightly rough, larger radiator that I bought many years ago from the late John Hartshorne, a prominent Scott enthusiast who had some wonderful stories, not least from his work with Wilf Green in bringing East German MZ’s into the UK in the years before the ‘Iron curtain’ came down.
Also on the agenda is crank counter-balancing. A Scott engine, being a 180° twin has reasonable primary balance, and normally they are known as being fairly smooth engines. They have almost no actual balancing on each crank assembly however, as the cranks are too small. The engine relies mainly on the large central flywheel to help dampen out the residual vibrations, which it does reasonably well. Some people have drilled the side on the flywheel on opposite sides to try to counteract the implied rocking couple effect but roger has never been convinced of the efficacy of this process. His own idea was to view each crank assembly in isolation and to work to try to balance at least as much of the big end weight as possible. In his ‘four bearing cranks’ he has two crank ‘discs’ each side, rather than the usual one. His enables him, using tungsten heavy metal (and Titanium rods) to balance the big end if nothing else. Rogers engine is very smooth, much more so than my own, and seems to want to rev more easily. We have ‘slugged’ single sided ‘Moss’ cranks in the past for a couple of people, and one of them cannot praise its smoothness enough. My cranks are not weighted, but I have some heavy metal slugs and I want to fit them. Normally, the holes are put into the cranks prior to heat treatment, as the final specification of the material conforms to around 50 to 53 HRC which is pretty tough stuff to machine. I’ve been looking into using surface coated solid carbide cutters rated up to 60 HRC to machine out for the slugs. I’ll post further information on the calculated % balance. I think it should be interesting!

Anyway, enough for now. things are happening! Even the Triumph head is back although a little more work needed here too.
I’ll try to not leave it so long as we go through the winter.

Not a great start to a New Year

Christmas is not without it’s delights when you’ve got a 2 year old daughter and a 5 month old daughter, but in my house we were all battling a bit with various virus cold/sinusy ailments and looking forward to all getting better and starting a brand new year. Unfortunately just as the New Year began, my dad has suffered an upsetting incident.
Somewhere between the evening of Sunday 4th January 2015 and the morning of the 5th, my father Roger had a shed broken into. They were obviously looking to steal garden equipment but realised that once they had carefully removed a glazing pane to enter, they could release the shot bolts holding the fixed side of the twin doors and swing the mortice locked doors open. They stole his 1990 Yamaha RD 350 LC YPVS F2, which was my first real performance road bike when I was 18. He really enjoys it as it’s lightweight and quick and comfortable.
We’re looking at security now of course, too late. At least we might prevent a repeat performance.
I’ve posted a message on a motorcycling forum, but it’s highly unlikely it will produce anything.

Picture here of identical machine:YPVS