Alp Sungurtekin 666 Vincent at the World Finals, SCTA September 29, 2020

[Monkeypants]

I find that the standard gearboxes on my more or less standard Rapides do not shift well at about 50 bhp, let alone 150bhp or whatever Alp's bike is making on nitromethane.
They really don't shift easily when the trans RPM is high.
Back off the rpm and don't rush the shift, the problem goes away. Ok for a 50 bhp setup on the road.
The Quaife/Surtees setup seems to shift instantly even at redline and beyond. In the 1970s, when he first proposed building of the Quaife Vincent 5 speed, Rod Quaife stated that the gears in his design are suitable for up to 200 bhp.
Would a Quaife gearset be acceptable in Alp's class?



Glen

 

[davidd]

Glen,

Your answer says much about the unusual problems of running very high HP engines. Backing off for a considerable time during shifting has been problematic with the Triumphs and Vincent. I think it was the first run where the radio announcer said that Alp had turned out and the recorded speeds were all over the place. It turned out that he was shifting. The bike would lose about 20 mph during the shift.

Alp will check the fundamentals again. I wondered if the Quaife would be helpful, but with a new build, it is important to check the baseline with many of the components being stock. The bike uses more stock components that most would believe. Compared to the Triumphs, this has been a very expensive project for Alp, and the more stock components that could be used, the better. Alp will need to exhaust all the possibilities with the stock set-up before moving on.

Changing to a 5-speed is not a rule problem. In general, the internals can be changed asl long as the cases are vintage.

David

 

[bmetcalf]

Alp runs in A-VF 1000. I see that the A-F 1000 (non-vintage) record is ~195 mph on a Yamaha. Is that within reach?

 

[timetraveller]

I suspect that something near that is possible. My reasoning is follows. Several years ago Roy Robertson got up to just under 170 mph on his track racing Egli. This is bored and stroked to about 1,200 cc but runs on petrol. His height above sea level was small and he was on tarmac so not the same type of problems as on some of the salt flats. He had a 'George Brown' type fairing fitted but got confused with some of the course markers and shut off well before the end of the timed section. Had it not been for that he would certainly have achieved 170 or more. Clearly the fairing gives a big advantage but the bike is set up for track use and has a larger, although more streamlined, frontal area. If the resistance goes as the square of the speed then to go from 180 to 200 needs and extra 23% more power. Whether the final change to nitro can do that I am not sure but it must be near.

 

[davidd]

Additional reporting by Bill Hoddinott in the March BRN:

David