48 replies to this topic

[joeninety]

Hi, I had an e-mail wanting to know more about Joe, with a particular interest in the Desmo valve conversion of the Manx engine.
Over to Ben
Chris

Edited by joeninety, 30 March 2011 - 19:22.

[Rennmax]

Thanks for opening the thread Chris, may I add your pic



Wonder whether the engine with it's massive cylinder head fitted into the Manx frame ?

Edited by Rennmax, 30 March 2011 - 20:28.

[GD66]

Not without some pretty major surgery to the tank base I'd have thought, Renn !

[joepotts7]

Here is something I have put together on the Joe Potts Desmo. There is plenty left to add, but I'll save that for later.

Joe Potts Desmo

Ben

[Rennmax]

Thanks a lot for your diligent synopsis of the technical side, can't hardly wait till you spill the beans regarding the engine's performance on the dyno and eventually on the track. Refering to the frame (and without hopping to another topic), I wonder whether Alec Crummie also designed and built the frame for the 'McIntyre AJS', which had obviously a quite different layout.

Edited by Rennmax, 31 March 2011 - 15:02.

[joepotts7]

Thanks a lot for your diligent synopsis of the technical side, can't hardly wait till you spill the beans regarding the engine's performance on the dyno and eventually on the track. Refering to the frame (and without hopping to another topic), I wonder whether Alec Crummie also designed and built the frame for the 'McIntyre AJS', which had obviously a quite different layout.

Yes Alec Crummie did make the frame for the McIntyre AJS. The frame was built in 1961. It was used for the first time in 1962 with a Matchless G50 engine. The reason for this is because McIntyre had works Hondas for the 250cc and 350cc class (new 285cc Honda) - leaving only the 500cc class for Potts machines. The G50 was a straight swap for the 7R engine, although it was only meant to be a temporary measure. Bob's JP7 Manx engine was more powerful than the Matchless, so it was planned to 'proove' the frame with the G50, before making a new frame of similar design for the JP7 engine. Sadly with Bob's death in 1962 this never happened.

Sadly I do not know where Bob's "McIntyre Matcless" frame is now. It was the most advanced frame in the world at that point.

Ben

[joepotts7]

Here is something I have put together on the Joe Potts Desmo. There is plenty left to add, but I'll save that for later.

Joe Potts Desmo

Ben

Here is part 2:
Preparations for the start of the 1958 racing season

Ben

[GD66]

Didin't the G50 chassis go to Jack Findlay and end up with Mick Hemmings, Ben ?

[Rennmax]

Ben, you know that Bob Mac finished 3rd behind MV mounted Hartle and Surtees on a AJS in the Junior TT in '60. I'm a bit puzzled now since this site (obviously copied from John Griffith's 'Famous racing motorcyles' book) claims that he already used his special framed bike then, hardly possible when the frame was built in '61

http://www.google.de...wM4nItAag1qjCCA

Refering to the McIntyre Matchless, I think Jack Findlay sold it in '69 to Austrian Werner Bergold. Sadly Werner lost his life on a enduro bike in '75. Have no idea what happend to the McIntyre bike afterwards, in fact I'm not even sure if he still possessed it

Edited by Rennmax, 31 March 2011 - 17:32.

[GD66]

I think we're talking about two differing chassis here, Renn. The G50 frame had its' bottom tubes running outside the crankcases to lower the engine, which laid forward a few degrees. The 7R-engined chassis depicted has an upright cylinder, and the bottom tubes run below the crankcases.

[Russell Burrows]

Ben, you know that Bob Mac finished 3rd behind MV mounted Hartle and Surtees on a AJS in the Junior TT in '60. I'm a bit puzzled now since this site (obviously copied from John Griffith's 'Famous racing motorcyles' book) claims that he already used his special framed bike then, hardly possible when the frame was built in '61

http://www.google.de...wM4nItAag1qjCCA

Refering to the McIntyre Matchless, I think Jack Findlay sold it in '69 to Austrian Werner Bergold. Sadly Werner lost his life on a enduro bike in '75. Have no idea what happend to the McIntyre bike afterwards, in fact I'm not even sure if he still possessed it

There was some discussion a few years ago in one of the mags as to who has an authentic bike. Mick Hemmings and none other than Ginger Molloy were in dispute on this, with the latter claiming the bike remained on the continent somewhere; I seem to recall Mick presenting the more persuasive story.

Edited by Russell Burrows, 31 March 2011 - 23:06.

[joepotts7]

Ben, you know that Bob Mac finished 3rd behind MV mounted Hartle and Surtees on a AJS in the Junior TT in '60. I'm a bit puzzled now since this site (obviously copied from John Griffith's 'Famous racing motorcyles' book) claims that he already used his special framed bike then, hardly possible when the frame was built in '61

http://www.google.de...wM4nItAag1qjCCA

Refering to the McIntyre Matchless, I think Jack Findlay sold it in '69 to Austrian Werner Bergold. Sadly Werner lost his life on a enduro bike in '75. Have no idea what happend to the McIntyre bike afterwards, in fact I'm not even sure if he still possessed it

Yes, they are very different bikes. The one in the link is one of the specials built for the 1960 season (a 500cc Manx and 350cc 7R). The McIntyre Matchless was the next special frame the Potts team made after those two.

Ben

[joepotts7]

There was some discussion a few years ago in one of the mags as to who has an authentic bike. Mick Hemmings and none other than Ginger Molloy were in dispute on this, with the latter claiming the bike remained on the continent somewhere; I seem to recall Mick presenting the more persuasive story.

The Mick Hemmings machine is certainly not the ex-Bob McIntyre machine that was built at Bellshill. It could be the replica machine that Findlay's made, but it has nothing to do with McIntyre, Crummie or the Potts team. The frame on the Hemmings machine is not like the one produced by Alec Crummie.

Ben

[joepotts7]

Below is the third part of the story behind the Potts desmo.

The 1958 racing season begins.

[joepotts7]

Part 4 about the Potts Desmo:

Part 4 Potts Desmo

Ben

[Rennmax]

Part 4 about the Potts Desmo:

Part 4 Potts Desmo

Ben

Thanks a lot for your documentation and all the details I have'nt heard of before. Do you have any figures how the desmo engine did perform on the test bench ?

[joepotts7]

Thanks a lot for your documentation and all the details I have'nt heard of before. Do you have any figures how the desmo engine did perform on the test bench ?

Sadly it never ran. It sat in an uncompleted state, as can be seen here - What happened to the Potts Desmo.
You can see the bearings were fitted and that the bearing caps were all machined (as were the rockers). The team had no frame to fit the desmo and had to concentrate on getting McIntyre's season back on track with more conventional bikes.

Ben

[joepotts7]

And some photos of the Potts Desmo as it is now

Ben

[terryshep]

And some photos of the Potts Desmo as it is now

Ben

Thanks for all those details, Ben. I wasn't aware that Bob had the 90 bore motor that year. The Silverstone race was a 50-miler and the size of the circuit meant I had lots of time to study the behaviour of Bob's bike. I spent most of the race in his slipstream because his motor was really quick and the 55lbs he had on me made his acceleration really good. It was only due to a combination of Norton handling and Avon tyres which kept me in touch.

Bob was a Dunlop runner and while they may have had greater ultimate grip, the Avons had a more user-friendly sliding window. I could push the front to slow me towards the apex of a bend and drift the rear on the exit, better than Bob could do it with his shorter frame and Dunlops. This was a technique especially beneficial at Silverstone with its really high speed bends (they are hardly corners), as well as Gerard's at Mallory. Coming into Woodcote on the last lap, I felt I could pass him round the outside, so pulled out of the slipstream and attacked. Bob tried to defend but his bike couldn't stick and he very nearly collected me. However, we both avoided each other and he very nearly out-accelerated me to the line, no more than half a wheel in it as we finished. Another 100 yards and he would have had me.

I might add, he was the first to congratulate me.

As you have said, he was using Norton chassis after that and although his motor was very good, I found it was possible to win at the Southern 100. I think it was because the 90-bore motor perhaps wasn't optimised for the extra weight of the Norton and maybe the torque of the standard 'square' motor in my bike was able to keep pace on the straights at Castletown. Whatever the reason, we lapped everybody else and the decision went to me by the usual half-wheel.

I got on terrifically well with those lads from Bellshill, Bob, Alistair, Charlie Bruce, Pim (Bob's mechanic) and Joe. I know 'if-only's' are pointless, but when I was driving a Lotus 20 at the German GP at Solitude in 1962, Bob loved my car & we agreed we would race a couple of F3 cars on the Continent as a team in the following year. Then he went to that Oulton Park meeting.......

[Classicpics]

And some photos of the Potts Desmo as it is now

Ben

It's a great piece of history, but I'm afraid I find it all a bit sad, Bob was a wonderful man.

I watched a TV program about Jackie Stewart last night, the best years of car racing for me, but sadly as with the bike racing they last a lot of good men, that always sits uneasy with me. The entertainment was superb but the circuits were unsafe, yes crashing was part of the entertainment for some, but to have unprotected solid objects so close to the track on many circuits was horrific.

It will always be a dangerous sport, but it is relatively safe today, than goodness!

[joepotts7]

It's a great piece of history, but I'm afraid I find it all a bit sad, Bob was a wonderful man.

I watched a TV program about Jackie Stewart last night, the best years of car racing for me, but sadly as with the bike racing they last a lot of good men, that always sits uneasy with me. The entertainment was superb but the circuits were unsafe, yes crashing was part of the entertainment for some, but to have unprotected solid objects so close to the track on many circuits was horrific.

It will always be a dangerous sport, but it is relatively safe today, than goodness!

In some aspects it is tinged with sadness. However the team at Bellshill had so many happy times - really were like a family. You don't have to talk with someone about the Potts team for long until a smile or a hillarious anaecdote comes up. What the Potts team did and how they all got on really makes me smile. To do what they did - and from the back of a funeral parlour outside Glasgow is amazing.
The trophy won by Alastair King on a Potts Manx for finishing 2nd at the 1961 500cc Italian GP held at Monza:

[joepotts7]

Thanks for all those details, Ben. I wasn't aware that Bob had the 90 bore motor that year. The Silverstone race was a 50-miler and the size of the circuit meant I had lots of time to study the behaviour of Bob's bike. I spent most of the race in his slipstream because his motor was really quick and the 55lbs he had on me made his acceleration really good. It was only due to a combination of Norton handling and Avon tyres which kept me in touch.

Bob was a Dunlop runner and while they may have had greater ultimate grip, the Avons had a more user-friendly sliding window. I could push the front to slow me towards the apex of a bend and drift the rear on the exit, better than Bob could do it with his shorter frame and Dunlops. This was a technique especially beneficial at Silverstone with its really high speed bends (they are hardly corners), as well as Gerard's at Mallory. Coming into Woodcote on the last lap, I felt I could pass him round the outside, so pulled out of the slipstream and attacked. Bob tried to defend but his bike couldn't stick and he very nearly collected me. However, we both avoided each other and he very nearly out-accelerated me to the line, no more than half a wheel in it as we finished. Another 100 yards and he would have had me.

I might add, he was the first to congratulate me.

As you have said, he was using Norton chassis after that and although his motor was very good, I found it was possible to win at the Southern 100. I think it was because the 90-bore motor perhaps wasn't optimised for the extra weight of the Norton and maybe the torque of the standard 'square' motor in my bike was able to keep pace on the straights at Castletown. Whatever the reason, we lapped everybody else and the decision went to me by the usual half-wheel.

I got on terrifically well with those lads from Bellshill, Bob, Alistair, Charlie Bruce, Pim (Bob's mechanic) and Joe. I know 'if-only's' are pointless, but when I was driving a Lotus 20 at the German GP at Solitude in 1962, Bob loved my car & we agreed we would race a couple of F3 cars on the Continent as a team in the following year. Then he went to that Oulton Park meeting.......

Thanks for the reply Terry. You are very right on Bob's Dunlop rubber. At this point in the season Bob was using narrower tyres on the Razorblade bikes tyres (2.75 front and 3.00 rear, as opposed to the more conventional 3.00 and 3.50). Bob attributed the high speed sliding of the 275lb 500cc partly due to these narrow section tyres. After Silverstone Bob fitted tyres with a conventional section.

Ben

[terryshep]

"the Avons had a more user-friendly sliding window"
Would this be the Avon GP type, a fantastic tyre if I'm correct
A different profile to the triangular type, more like a modern profile if I recall ?

Yes, Joe, it was whatever Avon called their racing boots back then; the rear was the one with the zig-zag tread. They first came up with the separate triangular tread blocks but I found that this was far too user-slideable for comfort, so they joined them up with a continuous rib right round the tyre. The front had circumferential ribbing on the sides and an interrupted tread block pattern in the centre, for braking. They were, as you say, of a rounded profile, no suggestion of triangular shape, so they were very predictable as you laid them over and wonderfully controllable in a corner.

The high hysteresis compound didn't come along until late 1960.

[Russell Burrows]

The Mick Hemmings machine is certainly not the ex-Bob McIntyre machine that was built at Bellshill. It could be the replica machine that Findlay's made, but it has nothing to do with McIntyre, Crummie or the Potts team. The frame on the Hemmings machine is not like the one produced by Alec Crummie.

Ben

Joe, I recently came across accounts by both Jack Findlay and Mick Hemmings on the provenance of Mick's bike. Jack claimed he sold the original Belshill bike, by then fitted with a 7R motor, to Brian Ball in 65/66, 'and this is now the bike owned by Mick Hemmings'. Findlay said that at the time of selling the original, he had a G50 motor fitted to a Bill Jakeman built replica. He said the Jakeman bike was a wider framed version, built to accomodate a six speed Schaftleitner gearbox, and it was this bike, one built in the winter of 63/4, that is the famous McIntyre Matchless of GP fame.

According to Mick, after Brian Ball had used the original framed bike for about a year, he sold it to Stan Hudson who in turn passed it on to Bill Gidman, and it was from Bill's dusty loft that he rescued the bike in 1978. Unfortunately, Mick also claimed the bike came with a Quiafe six speed box. Now I must admit to having no idea if a Quaife box would fit the original 'slim' frame, so perhaps this apparent contradiction isn't relevant?

I sense there's a bit of a running controversy on the authenticity issue around this bike and that unlike me you know the history?

Edited by Russell Burrows, 07 April 2011 - 21:30.

[joepotts7]

Joe, I recently came across accounts by both Jack Findlay and Mick Hemmings on the provenance of Mick's bike. Jack claimed he sold the original Belshill bike, by then fitted with a 7R motor, to Brian Ball in 65/66, 'and this is now the bike owned by Mick Hemmings'. Findlay said that at the time of selling the original, he had a G50 motor fitted to a Bill Jakeman built replica. He said the Jakeman bike was a wider framed version, built to accomodate a six speed Schaftleitner gearbox, and it was this bike, one built in the winter of 63/4, that is the famous McIntyre Matchless of GP fame.

According to Mick, after Brian Ball had used the original framed bike for about a year, he sold it to Stan Hudson who in turn passed it on to Bill Gidman, and it was from Bill's dusty loft that he rescued the bike in 1978. Unfortunately, Mick also claimed the bike came with a Quiafe six speed box. Now I must admit to having no idea if a Quaife box would fit the original 'slim' frame, so perhaps this apparent contradiction isn't relevant?

I sense there's a bit of a running controversy on the authenticity issue around this bike and that unlike me you know the history?

Thanks for the info Russell. I do not know much of the history regarding the bike after it left Bellshill, but I know Alec Crummie's work. The frame Hemmings has, is without doubt not the one made by Crummie.

Race history on bikes/cars is sometimes a very contentious issue.

Ben

[joepotts7]

A nice story from racing in the early 60s at the TT:
Works Bianchi team and the Bellshill brigade at the 1961 TT

[terryshep]

A nice story from racing in the early 60s at the TT:
Works Bianchi team and the Bellshill brigade at the 1961 TT

That's a nice little story, Ben and sounds very much like the Bob I knew. Here's another pic from the period, note the 1956-style transporter in the background! I wonder if anybody will recognise the two people to the left? Or say where it is?

[fil2.8]

Is it at Aberdare , Terry ??

[Russell Burrows]

That's a nice little story, Ben and sounds very much like the Bob I knew. Here's another pic from the period, note the 1956-style transporter in the background! I wonder if anybody will recognise the two people to the left? Or say where it is?

Geoffrey Duke talking to the bloke in the fyling jacket? And yourself talking to Bob. Wild and crazy guess as to where: Scarborough?

Edited by Russell Burrows, 12 April 2011 - 17:25.

[davyboy]

Geoffrey Duke talking to the bloke in the fyling jacket? And yourself talking to Bob. Wild and crazy guess as to where: Scarborough?

is the rider facing bob mac not alistair king

[terryshep]

Geoffrey Duke talking to the bloke in the fyling jacket? And yourself talking to Bob. Wild and crazy guess as to where: Scarborough?

Russ, I'm not sure that that is Geoff though it is very like him. I don't have a memory of him being there that day. You missed Alistair King, too! Mr fil2.8 is right about Aberdare, though.

Two people to the left of Alistair are of interest...... Have a try.

[Russell Burrows]

Russ, I'm not sure that that is Geoff though it is very like him. I don't have a memory of him being there that day. You missed Alistair King, too! Mr fil2.8 is right about Aberdare, though.

Two people to the left of Alistair are of interest...... Have a try.

Can't, Terry, you've stumped me good and proper.

[larryd]

Can't, Terry, you've stumped me good and proper.

Second left from Alastair K - Jack Williams ?

First left - Chas Mortimer's dad Charles ??

Why do I keep taking flyers ???

[terryshep]

Second left from Alastair K - Jack Williams ?

First left - Chas Mortimer's dad Charles ??

Why do I keep taking flyers ???

No, larry, no cigar! First left is a rider, second left an industry person.

[joeninety]

[quote name='Rennmax' date='Mar 30 2011, 21:23' post='4931776']
Thanks for opening the thread Chris, may I add your pic



I always thought Ducati had the sole rights to the Desmo concept. Interesting aricle regarding the razorblade frame, the tapered front down tube is a great concept. I always thought the featherbead frame was over - engineered. Wonder why Norton, and others, were so set in their ways and so negative to great ideas to improve their machines. Suppose it's a kick in the teeth in truth. Enter the Japanese, the footage of Honda's R&D department as featured in the Jim Redman video says it all. They were light years ahead, the draughtsmen the intricate designs as proven in the recent Honda six replica, even todays engineers were outstanded at the detail ie different size main bearings for each crank etc.

[Russell Burrows]

I always thought Ducati had the sole rights to the Desmo concept. Interesting aricle regarding the razorblade frame, the tapered front down tube is a great concept. I always thought the featherbead frame was over - engineered. Wonder why Norton, and others, were so set in their ways and so negative to great ideas to improve their machines. Suppose it's a kick in the teeth in truth. Enter the Japanese, the footage of Honda's R&D department as featured in the Jim Redman video says it all. They were light years ahead, the draughtsmen the intricate designs as proven in the recent Honda six replica, even todays engineers were outstanded at the detail ie different size main bearings for each crank etc.

According to the ultra reliable source that is Wikipedia, the desmo idea was patented as early as the 1890's. Mercedes racing engines of the 50's also employed it.

[Robin127]

According to the ultra reliable source that is Wikipedia, the desmo idea was patented as early as the 1890's. Mercedes racing engines of the 50's also employed it.

I recollect being told that Triumph Dolomite Sprints of the 1970's used desmo valve gear but I could just be imagining it.

[Herr Wankel]

I recollect being told that Triumph Dolomite Sprints of the 1970's used desmo valve gear but I could just be imagining it.

I think they may have been 16 valve,but not desmo.Legend has it that you could hang the car by the cylinder head with no head nuts on.It was so hard to remove them,if they'd been on a while !

HW

[exclubracer]

I think they may have been 16 valve,but not desmo.Legend has it that you could hang the car by the cylinder head with no head nuts on.It was so hard to remove them,if they'd been on a while !

HW

Spot on there Andy, the studs were a tight fit and would corrode the ally by galvanic action and the only solution was to drill out the cut-off stud/corroded ally and press inserts in the head. Even the good old gas-axe wouldn't shift 'em

[Rennmax]

..... Wonder why Norton, and others, were so set in their ways and so negative to great ideas to improve their machines. Suppose it's a kick in the teeth in truth.

I think Joe Craig was very well aware of the limits a single has way back in 1946. As far as I know, the engineering team who also designed the 16 cylinder BRM engine was commissioned to develop a watercooled 4 cylinder in 1948. In fact, a single cylinder 125 cc engine was made for testing in 51/52. Although the power output of 10,5 bhp was disappointing, they nevertheless carried on to build a complete 4 cylinder engine, though this motor seemingly never ran
And there was the French Nougier machine, which Craig wanted to purchase for about 3500 GBP in the mid fifties as a base for own development, but was vetoed by AMC

Edited by Rennmax, 22 April 2011 - 09:23.

[GD66]

As far as I know, the engineering team who also designed the 16 cylinder BRM engine was commissioned to develop a watercooled 4 cylinder in 1948. In fact, a single cylinder 125 cc engine was made for testing in 51/52.

Are you referring to the Leo Kusmicki-designed prototype engine for the Vanwall here, Renn ?
Based on four x Manx cylinders on a common crankcase, but never used.

Edited by GD66, 22 April 2011 - 10:31.

[Rennmax]

Are you referring to the Leo Kusmicki-designed prototype engine for the Vanwall here, Renn ?
Based on four x Manx cylinders on a common crankcase, but never used.

No Glenn, the project you mention is alluded to here

http://thevintagent....ton-squish.html

but the 4 cylinder 'Manx' inspired car engine with a capacity of 2.3 litres in '54 is a completely different venture. I was refering to a 500/4 watercooled motorcycle engine which is described in the general trustable Norton book written by Christian Spahn which shows the 125 test bed engine and parts of it as it was still existing in '59, sadly the trace ends there.

Edited by Rennmax, 22 April 2011 - 12:07.

[GD66]

Oh, gotcha now. Yes, I recall a detailed drawing of the bike-to-be with the 500/4 engine, in one of Vic's books, looked promising but naturally the glacier-like development aspirations of Norton's management ensured nothing that exotic would ever roll out the race shop doors...

Happy Easter eggs to all, by the way.

Edited by GD66, 22 April 2011 - 12:26.

[Rennmax]

Oh, gotcha now. Yes, I recall a detailed drawing of the bike-to-be with the 500/4 engine, in one of Vic's books, looked promising but naturally the glacier-like development aspirations of Norton's management ensured nothing that exotic would ever roll out the race shop doors...

Happy Easter eggs to all, by the way.

Well, men like MD Gilbert Smith were first and foremost business men, hence more interested in their return of investment than the pure joy of having a brilliant GP winner and Gilera was not a competitor for Norton in their aim to secure their market share...Vic is Mr Willoughby ?
And happy Easter from an extraordinary hot Germany as well

Edited by Rennmax, 22 April 2011 - 15:24.

[joepotts7]

Charlie Bruce and his 250cc DOHC Velocette:
Charlie Bruce DOHC Velo

[Mistron]

Hi folks,

I don't normally look at the bike threads, but by chance I read this thread just the other day, as a Scottish enthusiast I am of course interested in Joe Potts and the JPs.

By complete co-incidence I have just found an article from 'the Scotsman' back in 2004 all about Joe! I'd kept it all that time and this must be the first time I've seen it since then. a bit wierd!

Anyway, If I can work out my scanner I'll, try to post a copy.

I'd forgotten that Potts did the development work on the Buick V8 heads for the Ecurie Ecosse Tojeiro coupes.

Al

[joepotts7]

Hi folks,

I don't normally look at the bike threads, but by chance I read this thread just the other day, as a Scottish enthusiast I am of course interested in Joe Potts and the JPs.

By complete co-incidence I have just found an article from 'the Scotsman' back in 2004 all about Joe! I'd kept it all that time and this must be the first time I've seen it since then. a bit wierd!

Anyway, If I can work out my scanner I'll, try to post a copy.

I'd forgotten that Potts did the development work on the Buick V8 heads for the Ecurie Ecosse Tojeiro coupes.

Al

Plus the cylinder head work on the Le Mans Aston Martins. The first hardtop MGB was done by Joe. MG came up to take pictures/drawings of his car - became the GT.

[joepotts7]

Second part on the Cahrlie Bruce DOHC Velo:


Charlie Bruce Velo part 2

Edited by joepotts7, 10 May 2011 - 10:07.

[joepotts7]

The things dreams are made of...
1961 Italian GP at Monza