Speed anomaly

Rohan · Oct 14, 2015

In a similar vein, Alan Shepherd on a rather fast 350cc Ajay Boy Racer in the 1960 Ulster TT had given the MV boys a real scare, harrying them until his cam chain broke, a real rarity for Ajays. MV protested his engine (implying that it was bigger then 350cc) but it was stripped and found to be legal. They simply couldn't believe that it/he could go that fast, as good as the latest multi cylinder MV Augusta racer.

Mike Hailwood in the 1961 IoM Junior TT had a similarly wickedly fast Ajay single, but the gudgeon pin let go 15 miles from the end.
Going (much) faster than the design had been designed/tested to ??

http://cybermotorcycle.com/archives/puc ... js7r98.jpg

It would have had a fairing for these era of races, but I couldn't readily find a pic ....
?
http://niclassicscramblesclub.com/galle ... 1318962902

johnm · Oct 15, 2015

" wickedly fast Ajay single, but the gudgeon pin let go 15 miles from the end. "

Actually Peter Williams swears it wasn't the gudgeon pin but a cam problem. His Dad built the engine. The gudgeon pin was a convienient story.

Peter Williams told me this himself.

(That Enfield is quick !!!!!!!! )

Bernhard · Oct 15, 2015

Thanks for posting this infro Snotzo-this is the first time I have seen the top speed of the Seeley –Enfield.
Re “Steve Linsdell's Enfield Bullet will not develop anything like the same rwhp as any of the Norton’s on the screen, so how does it manage to run so fast in a straight line?” quote.
The speed of 138 mph suggests that it is making at least 50 BHP, on par with a good Manx Norton -Ollies dad was beating them years ago, I watched Steve Linsdell racing the 500 single Royal Enfield in the 1970s around places like Brand’s Hatch, usually winning his class, his speed was really fast., as he regularly beat the DOHC 500s. He tuned his own engines raising the compression ratio, a G.P. carb, fitting a 750 drum front brake, (Classic racing rules at the time) I am surprised that Steve doesn’t tak the bike to the Elvington speed weekend –I am sure that they would come away with a record, or two.
This must be one of the fastest petrol fuelled 500 single pushrod bikes out there-unless someone knows different
Steve Linsdell started racing in 1977 on a hand built Royal Enfield with a 1959 Bullet 500cc engine and a Colin Seeley frame. The public was quite sceptic when he took the field at the Isle of Man TT in 1981 and astonished to see him finish second in the newcomers race at 94.87 mph. This is the last Royal Enfield to go on the IOM TT podium!

Bernhard · Oct 15, 2015

Fast Eddie said:
Maybe the 4 valves need higher revs to achieve that peak power, and maybe riders weren't able to keep the motor 'in the zone' for some reason ergo actually produced less power at that point?
Alternatively, as all the 4 valves DNF, maybe they just weren't running right?
It surely seems very mysterious, but at the end of the day, there has to be a sound reason for this anomaly.

Not really very mysterious, most engines, when put on a Dyno have a peak power, then it will tail off on a graph, the 4 valves will do exactly the same.
As I answered previously, the heavy extra 2 valve springs poundage that the engine has to overcome WILL kill off the power quicker when the engine reaches its red line power limit. The acceleration of a 4 valve engine at lower revs will be quicker than a 2 valve, as it is able to fill the cylinder quicker and is still climbing up the liner power curve.
If you really want to compare like with like, ride a couple of 250 Ducati’s back to back, like I did, at the Kirby – Vic Camp racing school, they were both more or less the same bike, except one was a Desmo and the other had normal valve springs, the Desmo would not only out accelerate the standard bike but go at a higher top speed because it didn’t have the valve springs to overcome which the standard engine had to overcome-this alone would put a standard engine at an enormous disadvantage .

Fast Eddie · Oct 15, 2015

Bernhard said:
Fast Eddie said:

Maybe the 4 valves need higher revs to achieve that peak power, and maybe riders weren't able to keep the motor 'in the zone' for some reason ergo actually produced less power at that point?
Alternatively, as all the 4 valves DNF, maybe they just weren't running right?
It surely seems very mysterious, but at the end of the day, there has to be a sound reason for this anomaly.

Click to expand...

Not really very mysterious, most engines, when put on a Dyno have a peak power, then it will tail off on a graph, the 4 valves will do exactly the same.
As I answered previously, the heavy extra 2 valve springs poundage that the engine has to overcome WILL kill off the power quicker when the engine reaches its red line power limit. The acceleration of a 4 valve engine at lower revs will be quicker than a 2 valve, as it is able to fill the cylinder quicker and is still climbing up the liner power curve.
If you really want to compare like with like, ride a couple of 250 Ducati’s back to back, like I did, at the Kirby – Vic Camp racing school, they were both more or less the same bike, except one was a Desmo and the other had normal valve springs, the Desmo would not only out accelerate the standard bike but go at a higher top speed because it didn’t have the valve springs to overcome which the standard engine had to overcome-this alone would put a standard engine at an enormous disadvantage .

Not sure I follow you Bernhard, increased valve spring pressure will consume BHP I fully agree. But this will be shown in lower BHP readings at the wheel. And even I can relate to a lower BHP machine not being able to match the top speed of a similar but higher BHP machine. However, the question, and thus mystery, is regarding how and why more powerful engines, on otherwise similar machines, show a lower top speed than less powerful ones ...

Rohan · Oct 15, 2015

johnm said:
" wickedly fast Ajay single, but the gudgeon pin let go 15 miles from the end. "

Actually Peter Williams swears it wasn't the gudgeon pin but a cam problem. His Dad built the engine. The gudgeon pin was a convienient story.

Peter Williams told me this himself.

Interesting to hear that, John.
If his dad built that engine, the chief engineer for AMC, was he retired by then ?
The real inside story....

Bit like the old line of the DNF was due to 'magneto failure".
(A conrod came out of the cases, and smashed the megneto off...!!),

johnm · Oct 16, 2015

Trying to remember the exact detail. It was about 10 years ago when Peter Williams and Norman White came down to NZ to visit the Pukekohe festival and the Norton Owners club. A friend of mine organised the trip so we were able to talk with Peter and Norman for a long time and spent the whole evening talking about racing and bike development. He was surprised to learn that he had very keen fans down in NZ who had been watching his racing and development time at Norton very carefully.

We were talking about cam design. Specifically the PW3 cam. I was using one in my Dommie - installed delayed - which surprised him. Peter pointed out that part of his purpose in designing this cam was to minimize the acceleration and jerk at initial openning. He said he had used a computer at Norwich university to help which enabled the required calculations to be done in a short time. He then talked about what he had done versus what his dad had done with the 7R and G50 cams. He said his dad had used a design method that went back to some developments done by Austin ???. (dont quote me on that - but Im sure it was one of the famous English car factories) But it produced high levels of what he called stab torque in the cam train. And he then said this caused problems with the cams in the 7R and G50. Thinking back he may not have said that his dad built the Hailwood engine but the cam was definitely his fathers (Jack Williams) design. And he said that's what caused the Hailwood bike to stop.

Again of course this is second hand information. But second hand from the man whose Dad did so much development on the 7R.

One thing I should have asked Peter is if he has his Dad's development records for the 7 R. Now I would love to see those notes !!!!!!

Bernhard · Oct 16, 2015

Snotzo said:
A bit of background that some may find interesting.
For the 1961 TT, Stan Hailwood asked Bill Lacey to build an engine for Mike, as he was without suitable machinery.
Bill had long held ideas about a special engine, so he set about the job, which entailed making a one piece crank, used with a D type Jaguar conrod, special oil pump, and a forged piston he obtained from Mahle. Bill also had cams made to his own design. All this with the bore and stroke left standard.
Bill had intended it to be best at 7500 rpm, but was pleasantly surprised to find it made 66 bhp at 7900 rpm, and was safe to 8300. This was crankshaft power, measured on Bill's Heenan and Froude DPX1 dynamometer.

Through Mike, this was the last Senior TT won by a Norton motorcycle.!

As a footnote to this story, some years later Mike was a Red Book victim on that TV program “This is your life” where he met Bill Lacy again, and Lacy was heard to say to mike, “ I will do it again if you will do it again”

O'Really? · Mar 30, 2025

Snotzo said:
A bit of background that some may find interesting.
For the 1961 TT, Stan Hailwood asked Bill Lacey to build an engine for Mike, as he was without suitable machinery.
Bill had long held ideas about a special engine, so he set about the job, which entailed making a one piece crank, used with a D type Jaguar conrod, special oil pump, and a forged piston he obtained from Mahle. Bill also had cams made to his own design. All this with the bore and stroke left standard.
Bill had intended it to be best at 7500 rpm, but was pleasantly surprised to find it made 66 bhp at 7900 rpm, and was safe to 8300. This was crankshaft power, measured on Bill's Heenan and Froude DPX1 dynamometer.

Through Mike, this was the last Senior TT won by a Norton motorcycle.

Mike was timed through the Sulby speed trap at 138.45 mph, the same speed as John Hartle on an MV. The next fastest single was Dickie Dale, also on a Norton, nearly 10 mph slower.

When this feat is considered, with respect to the list of speed trap times given previously, it is hard to see where the progress has been made with current Norton machines.
From my study of dyno tests reported in another post 'The Last Norton Dyno Book?' I find most 500cc Manx engines tested at approx 50 bhp at 7000 rpm, only one exception being better, an engine owned by George Leigh, a dealer of Southport, which made 52.5 bhp at 7500 rpm, this with a lot of special parts and George's Titanium conrod.
Engines typical of these kind of power outputs would undoubtedly account for most of the lesser speed machines in 1961, but the Lacey engine was undoubtedly something quite unusual.
After the TT, Bill stripped his special parts out of the motor and rebuilt it with standard items. The special parts were never used again.

Very much better tyres are available now than riders had in 1961, and the TT course is undoubtedly smoother and faster for today's racers.

Does any of this make the speed anomaly issue any clearer? To me it serves to confuse even further!

Snotzo · Apr 22, 2025

A lot of water has passed under the bridge since my first post that started this topic. In last years MGP Senior Classic, the Linsdell Enfield Bullet recorded a top speed of 144 mph through the Sulby speed trap, and finished the drastically shortened one lap race on a podium 3rd place, beaten by a pair of Patons. I have said many times, "If you have enough power, you'll know it when you are on the race track, and if you have enough, the numbers are immaterial".

Fast Eddie · Apr 23, 2025

Snotzo said:
A lot of water has passed under the bridge since my first post that started this topic. In last years MGP Senior Classic, the Linsdell Enfield Bullet recorded a top speed of 144 mph through the Sulby speed trap, and finished the drastically shortened one lap race on a podium 3rd place, beaten by a pair of Patons. I have said many times, "If you have enough power, you'll know it when you are on the race track, and if you have enough, the numbers are immaterial".

144mph… wow…!

mdt-son · Apr 23, 2025

Rohan said:
If his dad built that engine, the chief engineer for AMC, was he retired by then ?

A dutch magazine's visit to the race shop by October 1962 documents that Jack Williams was still fully employed at the time. The visit also hints at development work on a 4 valve 7R.

- Knut

Fast Eddie · Apr 23, 2025

Been ponderin’ this thread again…

If a bike has more power, and better acceleration, yet a lower top speed, surely it can only be due to either aero dynamics or gearing ?

And given the comments about the fairings etc already made, it can only therefore be gearing ??

ando · Apr 27, 2025

There used to be David Vizard Porting School 1-10 lessons on the net. In one of those lessons there was a flow graph and an explanation showing 2 valve verses 4 valve. While the combined 4 valve flow was highest for 90% or so of the graph, from memory at a certain high flow point the 2 valve flow would exceed the 4 valve flow. Unfortunately those Porting Lessons have for some reason been removed. If anyone has copies of those lessons, or just the one with the 2v v 4v, and can post them then maybe that will answer the question.

ando

Fast Eddie · Apr 27, 2025

ando said:
There used to be David Vizard Porting School 1-10 lessons on the net. In one of those lessons there was a flow graph and an explanation showing 2 valve verses 4 valve. While the combined 4 valve flow was highest for 90% or so of the graph, from memory at a certain high flow point the 2 valve flow would exceed the 4 valve flow. Unfortunately those Porting Lessons have for some reason been removed. If anyone has copies of those lessons, or just the one with the 2v v 4v, and can post them then maybe that will answer the question.

ando

I can easily believe that to be the case in certain circumstances. Absolute peak power places more emphasis on flow, and a big pipe flows more!

But a big heavy valve is more difficult to control, so I’d imagine this only applies up to a certain rpm?

Anyway, in the scenario being discussed here it’s not really relevant as we are accepting that the 4 valve does produce more BHP. As I understand it at least.

Snotzo · May 8, 2025

Nigel, it appears that the advantage lies in mid range power, acceleration, but they do not have a peak power advantage, despite the exaggerated claims. There have been some top 4 valve performers in the past, but not currently. Three 2 valve singles currently racing in the Classic Senior class at the MGP have all bettered 140 mph through the Sulby speed trap, but the best speed I have seen for a 4 valve single cylinder machine is 135 mph, very creditable certainly, but hardly in line with the 61 bhp plus claims.

Speed anomaly

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