Doug Hele and the Balance pipe

Suddenly it all makes sense- the balance pipe on its own doesn't add power, it makes the bike quieter with a given set of silencers.
This allows for more free flowing silencers and that is where the power gain is.
My Commando has the stock balance pipe with open reverse cones. It is remarkably quiet until you really open it up.
If you don't care about noise levels, the balance pipe is of no advantage.
If you like a fairly quiet but freeflowing exhaust, the balance pipe gets you that.
Doug was a smart guy.
He added it to the T120 Bonneville and someone at Norton later copied that.

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Doug Hele


Douglas Lionel "Doug" Hele (13 July 1919 – 2 November 2001) was a pioneering British motorcycle engineer with Triumph and other firms: BSA, Douglas and Norton.

Norton closed the Birmingham factory in 1962 and moved production to Plumstead, South London, but Hele was ready for a change and took a job with the Ford Motor Company in their Dagenham factory. Things didn't really work out so it was with great relief when he accepted the position of Head of Development with Triumph in Meriden.

His first project was to improve the Triumph Bonneville T120. Drawing from his success with Norton Dominator twins, Hele raised the power ouptput from 47 bhp to 52 bhp on open megaphone exhausts by careful modifications to the design of the camshafts and cam followers. Keen to keep the power gains for road and production racing use, he added a balance pipe between the two exhaust pipes where they exited the cylinder head adjacent to the ports, quieting the engine and allowing use of a less-restrictive silencer. A decrease in exhaust-gas velocity caused by linking each cylinder into effectively two silencers was addressed by reducing the exhaust pipe diameter from 11 /" to 11 /".[4]

That article claims that Doug Hele paid special attention to the design of the cams in the T120 Bonneville. The Bonneville usually had an E3134 inlet cam with the Tiger 110 E3275 cam on the exhaust. The E3134 cam was part of the Tiger 100 race kit which came out in 1953. The Tiger 110 cam was around in 1954. There was an E3134 profile exhaust cam for the unit construction Bonneville, but it was not in common usage. I don't think the article has much credibility.

The article is part of his obituary written by his best friend.
What part lacks credibility?
That Doug Hele would alter Triumph cams and improve them?
This is the guy who managed to make the ( formerly)gutless little Norton 500 Domi crack 100 mph at the IOM.
He is also the main design engineer behind the Meridian Triples that beat up nearly everything in race circles ( and still do in their class, unfortunately)
And the 650ss , and the short stroke Manx, and made the T100 into a very competetive racebike
and so on....

worntorn said:

The article is part of his obituary written by his best friend.
What part lacks credibility?
That Doug Hele would alter Triumph cams and improve them?
This is the guy who managed to make the ( formerly)gutless little Norton 500 Domi crack 100 mph at the IOM.
He is also the main design engineer behind the Meridian Triples that beat up nearly everything in race circles ( and still do in their class, unfortunately)
And the 650ss , and the short stroke Manx, and made the T100 into a very competetive racebike
and so on....

Click to expand...

All of the above is true ,but I have a feeling that Dunstall actually offered an exhaust system with balance pipes before the 4into 1 into 2.. I think it was 68 when the Bonnie won the ProductionTT , Dunstall may have copied it , or arrived at it independently. I think it was clocked at 130mph and MCN gave this list of detailed developments that had incrementally added around 15mph .. However it should be noted that in 1962 a 650 SS production racer was clocked at 133 mph down the Norwich straight.. 7, 590 rpm and went on to win... Presumably this was with the Domiracer cam that Hele had developed earlier.

A great engineer stymied by the bean counters

worntorn said:

Suddenly it all makes sense- the balance pipe on its own doesn't add power, it makes the bike quieter with a given set of silencers.
This allows for more free flowing silencers and that is where the power gain is.
My Commando has the stock balance pipe with open reverse cones. It is remarkably quiet until you really open it up.
If you don't care about noise levels, the balance pipe is of no advantage.
If you like a fairly quiet but freeflowing exhaust, the balance pipe gets you that.
Doug was a smart guy.
He added it to the T120 Bonneville and someone at Norton later copied that.

• 

Doug Hele
Article

Topics

Videos

Discuss

Connect

Folders

Notes

Doug Hele

Douglas Lionel "Doug" Hele (13 July 1919 – 2 November 2001) was a pioneering British motorcycle engineer with Triumph and other firms: BSA, Douglas and Norton.

Norton closed the Birmingham factory in 1962 and moved production to Plumstead, South London, but Hele was ready for a change and took a job with the Ford Motor Company in their Dagenham factory. Things didn't really work out so it was with great relief when he accepted the position of Head of Development with Triumph in Meriden.

His first project was to improve the Triumph Bonneville T120. Drawing from his success with Norton Dominator twins, Hele raised the power ouptput from 47 bhp to 52 bhp on open megaphone exhausts by careful modifications to the design of the camshafts and cam followers. Keen to keep the power gains for road and production racing use, he added a balance pipe between the two exhaust pipes where they exited the cylinder head adjacent to the ports, quieting the engine and allowing use of a less-restrictive silencer. A decrease in exhaust-gas velocity caused by linking each cylinder into effectively two silencers was addressed by reducing the exhaust pipe diameter from 11 /" to 11 /".[4]

Click to expand...

Another old mag pic. Someone smarter than me may have to rotate this one, too.




A friend commented positively the other day on the exhaust note of the Titanic with it's balance pipe and Campbell's peashooters.

Amazing !I wonder what year the mag is... the first appearence on the T 120 was at the 1968 prod TT. Actually in real life the Dunstall balancer looked horrible -just a bit of flexible pipe.

Balance or cross over pipes are not same thing as 2>1 Y header and something all deep south bootleggers have long understood, to point out possible error in Dunstall design reasoning, as cross over only needs 1/3 size of main tubes or loose some extra low end grunt but bigger tube does tend to soften/lower low throttle sounds more. If designing DIY or wanting to comprehend of cross-over/balance pipes why/how/where, search up those terms to see the scope and optimizing. Up close to head is not best place to tie together but still distinctly functional, as all cross overs are, just some ways a bit more better. Note: Dunstall tested how sharp a bend might hurt performance and never did find any sharp enough to tell.

Works similar in reverse to dual crab balance tubes, another path for pressure/reflection spikes to exit rather than back up as much on themselves. Us simple southerners think of it going easier out two exhaust pipes/mufflers instead just one. Flex tube was good idea for less leaks or fractures and less severe fitting hassle. Does not need nor should be sized to carry full exhaust flow volume so turbulence inside is a non issue, even don't look proper or factory.

Hello All

Just for info it was 1969 that the Thruxton Bonneville, ridden by Malcolm Uphill, became the first production motorcycle to lap the Isle of Man at over 100mph.
At the time this was only the second push-rod twin to achieve this. The first had been the Doug Hele 500cc Norton Domiracer in 1961 ridden by Tom Phillis.

Details of many of the mods made to the Bonneville are given in this book https://www.amazon.co.uk/Triumph-Th...5&sr=8-1&keywords=Thruxton+Bonneville+Sintich
The Triumph Experimental book by Mick Duckworth is also a good read for those interested in the era.

Andy

oldmikew said:

Amazing !I wonder what year the mag is... the first appearence on the T 120 was at the 1968 prod TT. Actually in real life the Dunstall balancer looked horrible -just a bit of flexible pipe.

Click to expand...

I think it was around '68 or '69 issue of Cycle. I was taking pics of notable stuff as I reviewed and arranged mags for display.

The crossover was made of Inconel, a type of stainless used in flexible exhausts. Some old Harleys had both header pipes made of inconel, I suppose because it was easier than making a snaky solid tube header.

Danno said:

I think it was around '68 or '69 issue of Cycle. I was taking pics of notable stuff as I reviewed and arranged mags for display.

The crossover was made of Inconel, a type of stainless used in flexible exhausts. Some old Harleys had both header pipes made of inconel, I suppose because it was easier than making a snaky solid tube header.

Click to expand...

Thanks for posting ,must admit the crossover looks much better than those I saw here in the UK. leaves open the question who imitated who.
Andy thanks for reminding me it was 69 when Malcom Uphill won . Have been trying to find the production racing regs for the era.. It could be that Worntorn called it right -that the benefit from the crossover was in noise reduction-enabling them to run silencers that were actually megaphones in disguise

worntorn said:

The article is part of his obituary written by his best friend.
What part lacks credibility?
That Doug Hele would alter Triumph cams and improve them?
This is the guy who ...
And the 650ss , and the short stroke Manx, and made the T100 into a very competetive racebike
and so on....

Click to expand...

In terms of the short stroke Manx (Works) I think you are vastly understating the work of Leo Kusmicki here - I believe Doug was the "learner" under Leo here,
And the T100 - how many senior TT's or places?
Not to say he wasn't a very skilled/gifted engineer but I think you may be overstating his contribution.

His job was to make the T100 competitive
at Daytona, which he did. Won it in fact, back to back in 66 and 67. That is why resurrected Triumph uses the "Daytona" name on their most competitive model built today.
The IOM isn't the only important motorcycle race.
Its all in the book " Triumph Experimental"
As far as the Manx goes, that may be. I only know that Norton paid him to make it go faster and it did.
That was the pattern everywhere he went, every bike he worked on.
But mainly my post was about the balance pipe .
There has been lots of discussion about it here over the years. Most wanted to see dyno info that would show an improvement with the balance pipe vs without.
The revelation for me was that it was never intended to work that way. It just quiets the exhaust to allow for a freeflowing, higher performance exhaust that still meets roadbike Db requirements.
And I'm not sure who was first with the idea, only that Hele added it to the Bonneville.
Unfortunately when Norton borrowed the idea, they got it backwards. Instead of using freeflowing silencers with the balance pipe, they chose those stuffed up black caps and the poor engine was strangled.
The fix is easy, but it makes you wonder who thought that one out!

Glen

And re the question of the T100 as a racebike after Hele's development work, this historical snippet is interesting

" At the 1969 Belgian motorcycle Grand Prix on the Circuit de Spa-Francorchamps in the Ardennes, Triumph's factory tester Percy Taitled the world champion Giacomo Agostini (MV Augusta) for three laps and finished second at an average speed of 116 mph (187 km/h) on the Daytona.[5]

The balance pipe may "work" in theory, but what a POS in practice. On the Norton, with the exhaust hanging off the vibrating engine, the pipes crack in the vicinity of the balance pipe. Plus when you need to remove the exhaust to do any work, the balance pipe makes it a much harder job. I would never ever purchase a replacement balance pipe exhaust for a Commando.

Stephen Hill

Re: the T100 - fair enough Glen
Consider half my hat eaten!

On the point of the balance pipe - I think I understand the reasoning you're putting forward.
If true, I wonder why all race "360" twins, with their low-backpressure exhausts don't have balance pipes?

I wondered about that too. Perhaps the balance pipe is really only useful to quiet the bike. So back in the day before noise restrictions at racetracks, the balance pipe had no benefit.

With noise restrictions in place at most racetracks today, the balance pipe could be helpful.
Its the perfect penny pinching British solution, a chunk of pipe , the cost of which is more than offset by the deleted silencer baffles.

Stephen Hill said:

The balance pipe may "work" in theory, but what a POS in practice. On the Norton, with the exhaust hanging off the vibrating engine, the pipes crack in the vicinity of the balance pipe. Plus when you need to remove the exhaust to do any work, the balance pipe makes it a much harder job. I would never ever purchase a replacement balance pipe exhaust for a Commando.

Stephen Hill

Click to expand...

I've had no issues with mine. 26,000 miles.

Exhaust balance/crossover, same as dual carb balance tube, can only help noise and some extra response at idle>low rpms, so adds nothing from beginning of mid range to top end but at least does not subtract/hurt mid to top end. Don't confuse this with a 2>1 Y header set. Its related to X connection between dual exhaust systems in a 4 or more cylinder engine. Note: connecting tube does not have to be straight or particularly short either, which is another way it differs from a Y 2>1 type header merging. A crossover/balance tube may not improve anything but it can not hurt low down response no matter how they are expediently done or placed or routed. Anyone that thinks/feels they harm any rpm performance, has some other unrelated un recognized issue.

oldmikew said:

All of the above is true ,but I have a feeling that Dunstall actually offered an exhaust system with balance pipes before the 4into 1 into 2.. I think it was 68 when the Bonnie won the ProductionTT , Dunstall may have copied it , or arrived at it independently. I think it was clocked at 130mph and MCN gave this list of detailed developments that had incrementally added around 15mph .. However it should be noted that in 1962 a 650 SS production racer was clocked at 133 mph down the Norwich straight.. 7, 590 rpm and went on to win... Presumably this was with the Domiracer cam that Hele had developed earlier.

A great engineer stymied by the bean counters

Click to expand...

If the balance pipe makes the exhaust quieter, it might mean that more radical cam timing can be used without increasing the noise to a level which is not tolerable. I believe Exup works on that basis.