Wheel alignment

Saturday 5 December 2009

Growing up a bit - drag racing

Road bike ownership was replaced by an old Wolesley 6/110 car as the main form of transport. Bikes certainly weren't forgotten though because mechanical engineering studies awakened an interest in engine development. The decision was taken to build a drag bike, partly because of the outrageous horsepower achievable with a supercharger and nitromethane but also because riding in a straight line would not expose my inability to go round corners at a fair lick without falling off.

My first ever drag meet - Santa Pod Dragway, UK

 The Mk1 supercharged 3TA 350cc drag bike, circa 1967

The first attempt at building a hot motor consisted of sticking a supercharger on a nearly stock Triumph 350cc twin motor and running it on methanol. Optimisim was soon replaced with pessimism when piston crowns regularly separated at the oil control ring as a result of high revs. A few calculations were done and a short-stroke crankshaft was built in the engineering labs and mated to a modified 500cc barrel and head to make a very over-square 350 to reduce mean piston speed. A whole load of other mods were carried out at the same time and a prolonged cycle of "blow it up, fix it, improve it and blow it up again" was entered into. The engineering work during this period would fill a book by itself.

The short stroke Mk 2 bike, Santa Pod UK, circa 1970 (courtesy Pete Miller)

Oh dear, oh dear, oh dear.... the hairy 1970's (courtesy Pete Miller)

The photo of me above shows a buckled alloy pushrod, one of the many engineering problems to be overcome and was fixed by replacing them with titanium. A friend recently commented that I looked like an extra from the TV series "The Avengers", which I thought was a bit uncalled for! The photo below is of me hanging on grimly at Santa Pod raceway.

 Nice hole shot! (courtesy Pete Miller)
Mk2 short stroke Icarus ready to go on the starting rollers

Eventually, Icarus became extremely competitive at a national level over the quarter mile and at world level over the standing start mile but the time and money to go further was beyond my means, interest waned and racing was abandoned.

As a footnote, the engine languished for many years in the shed of a friend,  John Hancock, who went on to become R&D Director at Cosworth Engineering, the race car engine builders.  It may still be there!!

Conclusions from this period: A happy marriage of engineering theory and practice by actually using my education to have fun! Worrying signs of maturity appearing.


  1. hi Geoff
    I am very interested in your bike development. With the renewed interest in Vintage Land Speed record setting at Pendine sands this year I am looking at turning a 350 Triumph heap of parts into a competitive bike on the sand.
    No doubt you have many more fond memories of running Icarus on the tarmac strip, but from one silly old fool to another 'it has to be done'

    leave a note here with an email if you are interested in sharing any information. best wishes Rob

    1. Hi there it may be too late but did you get anything done with the 350 motor? I have just picked one up in a sorry state and I'm looking to build a drag inspired engine out of it please contact me if you have any tips or info! Crusemonty4@gmail.com

  2. Hi Rob,Currently out of NZ so keeping it short, had no idea Pendine was back in use. The only true Triumph 350 part on my bike was the crankcase. The rest was heavily modified T100 or home-made like the crank to make it an over square 350. I don't think my experiences back in the mists of time would be a lot of use for a standard stroke motor, apart from piston crowns coming off at 9000 rpm!!

    Best wishes in your enterprise. Such thinks are there to keep us young - that's why I still do organised long distance events such as round NZ in 5 days!

    1. Hi Geoff as I said before it may be too late you lot may not be on this site anymore but please contact me as I am wanting to build a 3t motor into a competition style bike
      You are the only person I have seen to do it!

    2. Hi Monty,
      Nice to hear that there is at least one sucker for punishment in the world! As you may have seen on the Facebook post, I had knee surgery today and will be in hospital for a few days. It will give me time to put some basic notes together, outlining the engineering principles I followed. If you want more specific detail after that, just email me and I'll do my best to help.

  3. "blow it up, fix it, improve it and blow it up again"
    Some things never change Geoff, 4th time lucky for me next year (I hope)

  4. Hi Tiny,
    Piston crowns coming off at the oil control ring, Fixed with a short stroke crank. Valve bounce, fixed with stiffer springs but caused the pushrods to bend. Fixed with making titanium ones. And those were just the easy ones to fix!
    Best of luck on the salt next year!

  5. Just saw the nose cone of one called Rebel on The Repair Shop on TV. Used to know a couple of guys from a team called Frogs Island who raced dragsters back then

    1. Hello Bill - thanks for checking in! We get the UK Repair Shop on NZ TV so look forward to seeing it at some stage.


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