UKDRN

Anything Nostalgia Related.

Moderators: timetravel, ukdrn

 #39706  by ColinF
 
Can anyone tell me when the mult-engined bikes were outlawed? Tried searching online and couldn't find anything!
 #39707  by ukdrn
 
Phil Baimbridge says they never were outlawed Colin.
 #39711  by ColinF
 
Thanks for the replies so far. I was reading an article by John Stein (2014) "The birth of the modern Top Fuel Motorcycle" which said that the changing of the guard was in 1978 when Marion Owen's twin engine Harley didn't win at Bowling Green. It goes on to chart the rise of Ron Teson on Honda and later the Teson Bernard Yamahas. Bo O'Brochta dominated 1980 and of course Elmer Trett was ahead of the game having switched to a single engine blown nitro Harley about the same time before going down the Kawasaki route when the Harley backing dried up. So......my question now is what was the last competitive twin-engine bike? Did the likes of John Hobbs/Jonny Munn and Rod Pallant etc keep double engined bikes winning over here longer than people did stateside?
 #39714  by shasta
 
In the current ACU drag race rule book, under the Top Fuel bike regs section 13.1.2 it states A maximum of two engines with unlimited modifications. Therefore they have never been banned and could still be used in competitions. I recall that the last competitive double engined bikes were still around in the late 1980s. Ton Pels on the double twin cylinder Puma and Paul Rose on the twin Yamaha TZ750 were still doing well on the European and domestic scene respectively as late as 1990.
 #39715  by ahensman
 
Of the many successfully run multi-engine bikes of the past (and there were a few triple engine ones including a couple of 9 cylinder behemoths , triple-engined two-strokers), the most interesting was John Hobbs' Hobbit.

If you have the opportunity, I implore you to go see it run and talk to John as it is unique in how it is set up.
Most multis used the concept of two identically tuned engines linked together in some way including both chains and gears.
The Hobbit, however, is two twin cylinder engines (one behind the other) set up to run as one four cylinder unit. One main advantage to this was to keep the bike's width to a minimum. Not to mention that Weslake didn't produce a four cylinder engine.

I'm not up to speed with all the technical details of running such a set up (sparking order etc.), but it sure worked well during the time I raced my bikes. The Hobbit was always the one to beat. If you can, take the time to visit with John the next time he runs the beauty then take that opportunity.
 #39716  by shasta
 
I have always been interested in how the power produced by the two engines and the engine speeds in particular can be made the same to avoid unnecessary loading on the coupling belt or chain between the 2 engines. I'm slowly rebuilding the bike AAC250 (AAC116) which used to run the two engines each with their own ignition system. These were missing when I got the bike, so I have come up with a solution which should work, is a lot cheaper than two systems and more importantly will ensure both engines run at exactly the same revs. I am using a Mallory 8 cylinder distributor run from the rear engine and will time the engines 90 degrees apart so effectively it becomes a single 8 cylinder engine. The attached photo shows the build at present. The gears were needed to reverse the drive to get the correct rotation for the distributor... the left hand side of the bike does not lend itself to take off a drive and when I bought the distributor I wasn't aware of it's rotation!!. It's still very much an ongoing project but should be finished this year...hopefully!
 #39717  by shasta
 
Oops! Here's the picture that didn't go through previously...


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IMG_3617 (2).JPG (2.15 MiB) Viewed 10832 times
 #39720  by ColinF
 
Again , thanks for the informative replies . I did meet John Hobbs at Dragstalgia and he very kindly let me sit on The Hobbit which feels smaller than i thought it would.I was also lucky enough to be "stuck" in the exhibition tent when it got rained off a couple of years ago and had quite a long conversation with Derek Chinn who was with Pegasus which was on static display from the National Motorcycle Museum along with The Hogslayer. These are all bikes that i saw in the magazines and books when i was at school and i'm basically reduced to that schoolboy when i go to Dragstalgia! i now have pictures of me sitting on all three ( i never grew up! ).
The picture of your double engine set up looks incredibly neat.Can you post a pic of the whole bike sometime ? and will we see it at Dragstalgia ? Love to have a closer look at it ( and promise not to sit on it ! ).
 #39721  by ColinF
 
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pegasus.jpg
pegasus.jpg (30.25 KiB) Viewed 10736 times
hogslayer.jpg
hogslayer.jpg (26.16 KiB) Viewed 10736 times
hobbit.jpg
hobbit.jpg (48.57 KiB) Viewed 10736 times