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Pre war supercharged Comet..........Zoller supercharger.

greg brillus

Well Known and Active Website User
VOC Member
Hi there folks........Does anyone have the foggiest idea where to look for the whereabouts or info, pictures anything at all about the small Licence built Zoller supercharger's used on the 2 factory built Singles.......I know they were unsuccessful only due to time limitations (mostly from over heating from what I understand)........Anyone with possible factory drawings, sketches anything that might help in the quest to put one back together (actually possibly both bikes........you never know).........Much appreciated.........Cheers......... Greg.
 

davidd

Well Known and Active Website User
VOC Member
Greg,

I have some photos and Phil Irving's notes on the supercharged bikes. Of course, one of them, ST29, was reported to be in Victoria. I wrote about Frank Pratt in an earlier Lightning/Grey Flash review and his partner was the well-known racer, Norm Osborn. Norm is shown here racing STT29 in Australia:

Osborn, Norman (2).jpg

I believe the supercharger was removed when Norm was racing the bike. Many years ago it was said that the bike was in Victoria in pieces.

Close up photos of the supercharged engine are in the PDFs.

Zollers seemed to be the favorite of MG, so there is some general information available on MG sites:


Series A TTBlown 02-1.jpg

Series A TTBlown 01-1.jpg

David
 

Attachments

  • Series A TTBlown 01.pdf
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  • Series A TTBlown 02.pdf
    211.2 KB · Views: 26
Last edited:

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
I know the other supercharged bike was dismantled by the factory and the frame reused in another race bike which was eventually sold as a std TT replica. This bike is still in UK with a non supercharged TT engine.

The PDF photos David just posted are the best ones of the supercharger that I have seen.
Simon
 

A Nut

Website User
VOC Member
Hi there folks........Does anyone have the foggiest idea where to look for the whereabouts or info, pictures anything at all about the small Licence built Zoller supercharger's used on the 2 factory built Singles.......I know they were unsuccessful only due to time limitations (mostly from over heating from what I understand)........Anyone with possible factory drawings, sketches anything that might help in the quest to put one back together (actually possibly both bikes........you never know).........Much appreciated.........Cheers......... Greg.
Hi Greg, I have the other TT machine, frame number D 963TTS but as Simon said it is fitted with what is described in the engine specification sheet as "TT engine". This is the same machine that is featured in David Wright's book "Vincents HRDs and the IOM ridden by Nigel Seymour Smith in the 1946,1947 &1948 Senior Manx GP. I bought the bike from Nigel many years ago and have restored it to the same specification as when Nigel rode it in the Island. I have taken it to the Island a couple of times and ridden it in the VOC closed roads sessions also a couple of goes up the test hill at Brooklands (and a bit of unofficial riding up the banking as well as a couple of runs at Prescott Hill Climb) I do have some factory photos of the bike in it's supercharged form but can't lay my hands on them at the moment. The Zoller blower was made under licence by McEvoys of Derby. Years ago I tried unsuccessfully to find a blower but they were probably specially made for the 2 machines as one photo clearly shows a HRD logo cast into the rear. It is delightful to ride but not that fast (a bit faster than my A Comet, however!) They stretched the frame a bit for the 2 supercharged bikes as they were fitted with some pretty large petrol tanks and the seat had to be moved back several inches to accommodate them but it suits me as I am 6ft tall!
Send me your email address and when I can find the photos I will send them to you.
Brtian Werrett
 

greg brillus

Well Known and Active Website User
VOC Member
It will be an ambitious project, but I will be rebuilding Franc's bike hopefully back to it's original supercharged specification........ My understanding was that Zoller seemed to cast the factory logo of sorts into the main blower casing. This seems to be the case with the ones fitted to MG's from pictures of ones I've seen. It would be very handy to have some factory spec pictures of the blower and drive housings.......We will probably make all the parts ourselves.......Rodney Brown, has kindly offered to assist here with all the castings needed........probably 3 for the blower and 2 for the drive housing. From the pictures i have studied, one item that looks a bit scary is the tiny oil pump mounted on the left side of the blower to inject a small metered amount of oil into the air intake to lube the rotor veins.......These were probably made of carbon, and would readily Gaul up the inner case wall if no lubrication was provided........Not unlike a rotary engine,ran without any lubricating oil in the fuel mix. Thanks to all for the pics, perhaps someone may have some info hiding somewhere.......It should be a fun if not challenging project, something different anyway. Making up that rather special oil tank in stainless............Hmmmm. Cheers for now.......... Greg.
 

greg brillus

Well Known and Active Website User
VOC Member
Hi there Brian, Yes Franc told me you had the other bike........It would be great to see the pictures you mentioned........I was looking at the detailed pictures David kindly posted above, and i can't tell if the drive housing/cover is in fact a casting or if it was fabricated from sheet alloy or stainless........It seems to have too many screws around it to be a simple sheet alloy cover. Mind you that seemed to be very common back in those days........lots of bolts/nuts holding everything together. My email address is feelinggreat01@bigpond.com I haven't started on this project yet, still busy with several others.......probably a job for next year give or take.......just wanted to do some homework to see what info can be found. We would probably be making 2 of everything rather than just one. I will not be buying and installing some other make or type of supercharger........I feel with the people i know that we should be able to duplicate the original as close as we can........Especially as Rodney is a series "A" fanatic and very keen to help out.
 

Gene Nehring

Well Known and Active Website User
VOC Member
Greg this is a book that you might like to find. It has allot of information about setting up and types of superchargers. Maurice Brierley owner of the super charged Vincent Methamon wrote it. Lots of good pictures etc.20210124_150235.jpg
 

greg brillus

Well Known and Active Website User
VOC Member
Thanks for that Gene, I've always had a thing for supercharging........when I was studying for all my aircraft engineering exams years ago, my highest mark was for supercharging. I have built a few......not many engines with them on.......If this one runs any kind of "Boost" it will be on the low side, probably 6 to 8 Lb's at most........and it will need to run on methanol I think, given the original ones suffered over heating quite badly.......enough to turn the piston rings "Blue"......... The cylinder head design is too flimsy.......the alloy ones look like exact copies of the cast iron ones, very weak........I am currently rebuilding one of the 2 factory 'Big fin" head TTR's .........same bike as in J B's "Original Vincent" These oversized fins were simply welded on to the original fins to add extra surface area, however, the welding has made the head like plastercine.
 

Robert Watson

Well Known and Active Website User
VOC Member
When Smith spent a bit of time looking for the blower for his Velocette Roarer project and found nothing, he just scaled some dimensions from pictures etc and as one does, went over to the lathe and built one. He might chime in but boost was not excessive and was in the range Greg is talking of (I think) Also it was a roots type one..... again I think

No doubt he will get on here in a day or so and tell me I am full of it!
 

greg brillus

Well Known and Active Website User
VOC Member
Thanks Robert, I think that might be the bike that is in Virgil Ellings bike museum in Solvang CA.......Cathy and I visited and met both he and Gill at the museum back in May 2019........He took me out the back and showed me the workshop with many more bikes and parts/engines......just amazing.......Actually, he might be worth a call........a lot of his bikes are exotic race bikes, so he might know or have information on this early supercharger.
 

delboy

Well Known and Active Website User
VOC Member
Greg,

I have some photos and Phil Irving's notes on the supercharged bikes. Of course, one of them, ST29, was reported to be in Victoria. I wrote about Frank Pratt in an earlier Lightning/Grey Flash review and his partner was the well-known racer, Norm Osborn. Norm is shown here racing STT29 in Australia:

View attachment 39778

I believe the supercharger was removed when Norm was racing the bike. Many years ago it was said that the bike was in Victoria in pieces.

Close up photos of the supercharged engine are in the PDFs.

Zollers seemed to be the favorite of MG, so there is some general information available on MG sites:


View attachment 39781

View attachment 39782

David
David,
excellent definition Series "A" close ups.
This is the sort of thing us [sad] "A" nuts long for. [Especially close up details of road-goers.]
Thanks, Delboy.
 

Glenliman

Well Known and Active Website User
VOC Member
This is reminding me of a recent Supercharged Norton purchased on another site.
The bike came complete with 2 large boxes of spares, including 4 sets of broken crankcases! :)
 

greg brillus

Well Known and Active Website User
VOC Member
Yes I guess due to the over heating issues, luckily these engines returned to a naturally aspirated state before any further abuse and/or poor tuning resulted in mechanical failure. Interestingly, this TTR that I am rebuilding (engine, gearbox and primary only) it was evident that it had indeed suffered a broken con rod at some point.
 

vibrac

Well Known and Active Website User
VOC Member
My friend built supercharged a Norton twin (it is allowed in the BHR regs!) he only raced it once he said it was great till you closed the throttle then it was like a vast brake was pulled on, and he couldn't obtain that fine control of retardation that is so necessary in Road Racing it it significant no others have raced a blown bike in the BHR road races since.
I seem to recall that the blown Vincent bike was never raced and only had one trial run in an IOM TT practice and was then abandoned as a supercharged racer, can someone confirm.this?
 

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