Supercharged Atlas

I was going through some old bike magazines, putting them up on ebay, and ran accross these two articles on supercharging a 750 Atlas back in the '60s. I thought they might be of interest to some of the listers.

This one used a Judson supercharger meant for a VW.











And this one has a SCOT blower.









Ken

I love the Triumph pre-unit primary cover in the vertical.

Just what I wanted for Christmas …………25 years ago!

That was a whole lot of work to produce only 103mph in the quarter mile. I am sure the N15 scrambler would have been even slower if it had ever got to the strip.

Too bad these guys did not know John Gregory at Sunset Motors back then. In 1963 John Gregory was getting 110 mph in quarter mile drags with a Norton 650 twin used for daily transportation. The bike used all stock factory parts in the engine along with Amal monobloc carbs, but of course it was massaged and assembled with a lot of care.

The thing about positive displacement *compressors* vs centrifugal *blowers* is that the 1st kind have a fixed ratio of air volume pumped per rpm so they greatly increase low-mid range power but then tapper down the boost effect as rpm increases to top end. To get top end increase to matter requires a rather larger compressor and all kinds of mechanical and fuel tricks to tolerate and make use of it.
Snail type blowers like turbo chargers increase their mixture packing boost the higher they turn up but are kind of tame just off idle, so allows a big block to grunt off line by its pure piston displacement torque then fills in the flow restrictions as rpm goes up till something breaks.

Rather clever to use one row of chain teeth to drive the compressor. Wonder if they had to keep it in an oil bath.

beng said:

That was a whole lot of work to produce only 103mph in the quarter mile. I am sure the N15 scrambler would have been even slower if it had ever got to the strip.

Too bad these guys did not know John Gregory at Sunset Motors back then. In 1963 John Gregory was getting 110 mph in quarter mile drags with a Norton 650 twin used for daily transportation. The bike used all stock factory parts in the engine along with Amal monobloc carbs, but of course it was massaged and assembled with a lot of care.

Click to expand...

Be rather interesting to know what Sunset Motors did to those "stock" Norton parts on assembly then - the book of Dommie RoadTests Reprinted shows a stock Manxman 650 in the early 1960s recorded an 80 mph exit from the 1/4 mile. And stock Atlas and 650SS were around the 90 to 95 mph mark. So thats a pretty large increase over a stock motorcycle. Is there a pic of this motorcycle anywhere ? Cheers.

beng said:

That was a whole lot of work to produce only 103mph in the quarter mile. I am sure the N15 scrambler would have been even slower if it had ever got to the strip.

Too bad these guys did not know John Gregory at Sunset Motors back then. In 1963 John Gregory was getting 110 mph in quarter mile drags with a Norton 650 twin used for daily transportation. The bike used all stock factory parts in the engine along with Amal monobloc carbs, but of course it was massaged and assembled with a lot of care.

Click to expand...

Care to back that up with FACTS mr mouth :!: