Commando motor in solid frame

Dances with Shrapnel said:

Uh huh. I know a BS'er when I see one.

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Yes, like you suggesting we could simulate a Fullauto head's dyno figures, without actually needing to dyno it.
And then defending this to the hilt, without having actually tried it and produced meaningful numbers.

And if you didn't know that 10 hp for 60 mph and 32 hp for a 100mph motorcycle, then your practical knowledge of this aero is about zip.

We were all set to have an interesting discussion about aero and hp numbers, and instead we got this.
Well done.

Dances with Shrapnel said:

For the benefit of the readers, I am not suggesting, I am stating they are wrong..

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How can they be wrong ?? They have been quoted for so long and so solidly that the whole motorcycling world used them as a yardstick, for a fair part of a century or more.

What did Mr Irving say about the Vincents hp and top speed.
45 hp and 110 mph, 55 hp and 125 mph. ?? Fairly comparable to a Commando even.
More if you did a Rollie Free.
Indian Chief had about 25hp, and 75-85 mph (big bike, the riders size makes a fair difference).

Heck, my old 1910 Triumph is said to produce about 10 hp, and do 60 mph.
If it ever gets mobile, I'll report back. Might be a few more decades, everything was well knackered,
it was obviously loved and ridden to death.
Brakes must have been an interesting prospect at that speed.....

So, has anyone any contributions as to how Jim can readily measure the engines output at
that 100 mph and half throttle. ?

Its often quoted that Tritons would likely be better if the builder spreads the frame rails to get the motor lower.
You do sometimes see this said to have been done, but the bikes are not raced to be able to report if this is significantly better or not. And unless its tried 100%, the final say is likely to be somewhat vague, at road speeds its going to good anyway.

wakeup said:

Whilst talking about getting the motor weight as far forward as possible, have a look at a good photograph on the side of a Manx Norton. Figure out where the crank centre line is, relative to any fixed points, wheel spindles, swinging arm spindle etc. Then have a look at a Triton with a unit motor and see where the crank centre line is, relative to the same fixed points.
The Manx crank is about as far forward and as low as possible, the triton maybe not...
cheers
wakeup

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Thats hardly surprising Alan - with a full fairing, when you sit up it barely makes any difference because of the fairing. Unless its minimal, and sitting up exposes your head/chest etc fully to the airflow.

Harley some years back did some record breaking with various fairings fitted.
They were amused when they discovered that a fuller touring fairing was faster than one of the skimpy speed fairing they had tried, obviously everything tucked in inside the fairing helps, considerably.

acotrel said:

The effect on the way your bike slows down from high speed when you back-off is interesting after you have fitted a fairing to it. Even your hands being outside the fairing must have an effect on your top speed.

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Not surprisingly, this subject of bhp vs mph vs machine weight has been extensively discussed over the years,
inc on other forums.
"Phil Irving in his book Tuning for Speed has a graph that gives a correlation between horse power,
approximate weight of bike and top speed."

Where do we think yer average 300 lb road race bike sits with respect to bhp @ 100 mph.
Yep, bang on 30 bhp.
"Very light stripped bikes" a bit less.
Heavyweight machines a bit more.

Rohan said:

P.S. And before anyone says anything silly, and for those mathematically inclined, it is generally quoted it takes the average moddersickle plus rider just over 30 hp to do 100 mph.

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might be best to start another ~ have at it thread, to continue a lengthy sub debate not related to topic, that if continued here, will likely lock a "Commando motor in solid frame" thread, if not worse

it's always best to take unrelated stuff that may unfold in a thread to a new/fresh one, well prior to differences becoming well developed

good bet also that a fresh thread would bring a new focus on the relevant issue(s), where participation by anyone on any level including going on at length or depth if interested or inclined wouldn't be a big deal

norsa1 said:

So here is my version of a Commando motor solidly mounted in a frame. The chassis is a BSA A 10 frame. The adapter plates run the full length of the engine bay and fix the motor and trans into the frame. It was a shoehorn fit but this is lovely combination with terrific handling and that wonderful Norton torque. This engine is a 270 degree and yes the vibration is an issue at low RPM, the engine is happier as the revs increase. The level of vibration is not objectionable.

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Another unique special! Very nice. I've oft wondered how the BSA and Triumph twins handled so well with their bolt-together skeletons. I suppose they, like Featherbed Nortons, were engineered for stiffness using the engine as a stressed member.

Danno said:

Another unique special! Very nice. I've oft wondered how the BSA and Triumph twins handled so well with their bolt-together skeletons. I suppose they, like Featherbed Nortons, were engineered for stiffness using the engine as a stressed member.

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+1

https://www.google.ca/search?sitesearch ... fWeJvVgMAO

Dances with Shrapnel said:

Uh huh. I know a BS'er when I see one.

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Rohan said:

Yes, like you suggesting we could simulate a Fullauto head's dyno figures, without actually needing to dyno it.
And then defending this to the hilt, without having actually tried it and produced meaningful numbers.

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Ah, showing your old wounds. The record stands as I not only tried it but did it, you, on the other hand, blathered on with your ignorance of the matter and virtually no relevant experience; - the record stands for perpetuity for all to see.

Rohan said:

And if you didn't know that 10 hp for 60 mph and 32 hp for a 100mph motorcycle, then your practical knowledge of this aero is about zip.

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It is so easy to parrot those numbers without any knowledge. Your numbers don't work for power required to overcome wind resistance; and this from someone who incorrectly states something and suggests it is good to quote accurately (below) ...too funny.

Rohan said:

Lets not beat around the bush, air resistance rises with the cube of the speed.
THE huge factor in top speed.

A minor point, but good to quote accurately...

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I still stand by my statement and am not about to dig you out of your hole. You must do the work to attain enlightenment ....if at all achievable.

Rohan said:

Dances with Shrapnel said:

For the benefit of the readers, I am not suggesting, I am stating they are wrong..

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How can they be wrong ?? They have been quoted for so long and so solidly that the whole motorcycling world used them as a yardstick, for a fair part of a century or more.

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The world is flat, how can they be wrong? Have you ever thought you might be using the numbers out of context? Read and understand Phil Irving on the matter. Do the math.
And now for the fun part:

Rohan said:

What did Mr Irving say about the Vincents hp and top speed.
45 hp and 110 mph, 55 hp and 125 mph. ?? Fairly comparable to a Commando even.

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You really soiled yourself in front of everybody here. Read the legend of that chart; I am beginning to spoon feed you here. Mind you, this discussion has been about air resistance and power to overcome that air resistance - this is your first clue. According to the legend of the Phil Irving chart, the curves depict b.h.p., commonly known as brake horsepower. B.H.P. in the subject chart includes power required to overcome wind resistance (at speed), as well as other resistances (ex. including rolling resistance losses, and probably rear chain losses, gearbox losses, primary chain losses and bearing losses.)

Plug your commonly "quoted for so long" numbers into the Phil Irving or wiki equations (basically the same) and see what you get! What do the results tell you??? Can you reconcile the two "common" numbers??? Maybe you will learn something but I doubt it. The whole point is power requirements to overcome wind resistance is proportional to the cube of the speed, something that maybe you still do not get and is likely the whole point of your handbag war here. Take the time to do the math. Air resistance does not "rise with the cube of the speed" as you so incorrectly stated.

Here is one I had Randy and Karsten Illg at Framecrafters.net put together several years ago.
This gearbox is a Nourish Shell and Shaft for a Triumph five-speed conversion. The rear hub is a light weight quick change (QC). The engine has a lightened crank with steel flywheel and undercut mains. The head is a Steve Maney Stage 2 with Steve Maney exhaust and racing pistons. Carbs are Amal Mk2 (34mm if I recall correctly). Fiberglass tank and seat pan. I recall the front brake is an alloy Lockheed race caliper and the steering damper is by Storz.
http://framecrafters.net/show-project.php?id=75
The second picture gives some perspective of the relationships between the crank, counter shaft, swing arm spindle and rear axle centerlines. Randy modeled the engine plates after the Convertas that were commonly available during the period.
The third picture is a view of the adjustable triple clamps.

The numbers I quoted weren't wrong, were they.

Old wounds ?
You were full of it from start to finish, with no hope of giving any meaningful answers.
Complete waste of wordage.

Good to see you have some serious motorcycling experience there.
Are you past it, or still have a Commando ?

Rohan said:

Not surprisingly, this subject of bhp vs mph vs machine weight has been extensively discussed over the years,
inc on other forums.
"Phil Irving in his book Tuning for Speed has a graph that gives a correlation between horse power,
approximate weight of bike and top speed."

Where do we think yer average 300 lb road race bike sits with respect to bhp @ 100 mph.
Yep, bang on 30 bhp.
"Very light stripped bikes" a bit less.
Heavyweight machines a bit more.

Rohan said:

P.S. And before anyone says anything silly, and for those mathematically inclined, it is generally quoted it takes the average moddersickle plus rider just over 30 hp to do 100 mph.

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deleted

Triton Thrasher said:

So, who said this:

Rohan said:

air resistance rises with the cube of the speed.

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and is it correct?

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I thought it was 'the square of the speed'? :?

http://www.explainthatstuff.com/aerodynamics.html

Air resistance—drag, as it's usually known—follows on from the distinction between laminar and turbulent flow. When a sports car speeds through the air, the flow remains relatively laminar; when a truck plows through it, there's much more turbulence. Drag is the force that a moving body feels when the flow of air around it starts to become turbulent. If you ride a bike or you've ever run a sprint race, it'll be very obvious to you that drag increases with speed. But a very important point is that it doesn't increase linearly as your speed increases but according to the square of your speed. In other words, if you double your speed, roughly speaking you quadruple the drag.

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Reference https://www.physicsforums.com/threads/a ... ce.391582/

The air resistance increases with the square of speed, so at 200km/h you need 4x as much power as at 100km/h

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Dances with Shrapnel said:

Here is one I had Randy and Karsten Illg at Framecrafters.net put together several years ago.
This gearbox is a Nourish Shell and Shaft for a Triumph five-speed conversion. The rear hub is a light weight quick change (QC). The engine has a lightened crank with steel flywheel and undercut mains. The head is a Steve Maney Stage 2 with Steve Maney exhaust and racing pistons. Carbs are Amal Mk2 (34mm if I recall correctly). Fiberglass tank and seat pan. I recall the front brake is an alloy Lockheed race caliper and the steering damper is by Storz.
http://framecrafters.net/show-project.php?id=75
The second picture gives some perspective of the relationships between the crank, counter shaft, swing arm spindle and rear axle centerlines. Randy modeled the engine plates after the Convertas that were commonly available during the period.
The third picture is a view of the adjustable triple clamps.

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The Triumph gearbox sits lower in that featherbed than in most Tritons. And the spindle relationship is therefore different and very healthy looking to my eye at least. I reckon there are subtle differences to what converta would have done.

I'd venture that Randy new his stuff!

What was it like to ride?

Honestly Rohan, you have quoted so many numbers we have all lost track - sort of like a random number generator, the numbers and issues and evasive side steps just keep coming like a shower of sparks. Clearly, you missed the point(s) again and again - on both threads. If you want an explanation of where you went wrong, please pm me and I will take the time to explain as I have suggested numerous times. I have given most reasonable enough guidance and explanation on this matter (ex. citing Phil Irvings graph out of context without understanding the components of the information) - just falling on deaf ears. Have you tried to run your "commonly quoted numbers" and reconcile the results - NO. You don't want to understand, you just want to be heard.

I still have a Commando road bike (bone stock) as well as components for my old Commando road racer. I also own a fleet of Seeley Mk2 road racers with various unique motors - more of a pleasant blight. Thanks for asking.

Fast Eddie said:

I'd venture that Randy new his stuff!

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Yes he does. I would categorize Randy as an expert and all around good guy. He and his son Karsten operate their shop maybe 20 minutes from me and they are a pleasure to deal with. They also campaign and sponsor race bikes. Karsten goes faster than the wind. The Nourish shell is designed to fit the AMC envelope in the cradle so I don't know what, if any, liberties Randy took with the gearbox location. I vaguely recall having to use a longer belt but other Featherbed Norton Twin racer I recall also used a longer belt (longer than a Commando) so I just don't know.

Fast Eddie said:

What was it like to ride?

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Ha! You asked! It has not even been started. Way too many irons in the fire with other rebuilds in the queue, work, and races so perhaps next season or it may be reworked for the street.

About that longer belt on the Featherbed Nortons - What some people seem to have failed to recognise is the length in the featherbed frame. Fitting a longer swing arm would be a bit absurd. The variation in rake which determines how the bike handles under power and braking, is affected by the bike's wheel-base and suspension setting .
On my Seeley and my old Tribsa the motor and gearbox are/were much closer together than they were on my Triton , however the swing arm on the Seeley is longer. The Tribsa was very good when the A10 frame was fitted with 60s Triumph fork yokes, however it was not raced.
A unit construction Triumph motor in a Featherbed frame is a waste of space - it cannot possibly work well. How would you ever get the weight distribution right without a big gap behind the gearbox ?

apologies, i had not read the whole thread when i posted the below, turns out someone else had already suggested starting another thread, further reading seemed to indicate invitations to a new thread that are not pursued

eitherway, here it is
started-with-pulls-100mph-only-throttle-t25242.html

i also see now how this was related or started from this topic/thread

84ok said:

might be best to start another ~ have at it thread, to continue a lengthy sub debate not related to topic, that if continued here, will likely lock a "Commando motor in solid frame" thread, if not worse

it's always best to take unrelated stuff that may unfold in a thread to a new/fresh one, well prior to differences becoming well developed

good bet also that a fresh thread would bring a new focus on the relevant issue(s), where participation by anyone on any level including going on at length or depth if interested or inclined wouldn't be a big deal

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acotrel said:

About that longer belt on the Featherbed Nortons - What some people seem to have failed to recognise is the length in the featherbed frame. Fitting a longer swing arm would be a bit absurd. The variation in rake which determines how the bike handles under power and braking, is affected by the bike's wheel-base and suspension setting .
On my Seeley and my old Tribsa the motor and gearbox are/were much closer together than they were on my Triton , however the swing arm on the Seeley is longer. The Tribsa was very good when the A10 frame was fitted with 60s Triumph fork yokes, however it was not raced.
A unit construction Triumph motor in a Featherbed frame is a waste of space - it cannot possibly work well. How would you ever get the weight distribution right without a big gap behind the gearbox ?

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The conversation about using a longer swinging arm was precisely regarding the issue you mention. I respectfully suggest that you didn’t read the threads properly.

No-one mentioned changing the wheel base. The idea was to move the swinging arm spindle further forward, and ideally, up or down, to give an ideal chain run.

That way, the engine can be mounted in the forward most position, then even with a unit construction engine, the set up would work perfectly well. The gap behind the gearbox would be there, and might be unsightly, but would be irrelevant to handling purposes.

In fact it might be useful to have such a gap to mount a battery, extended oil tank, or small compartment for the safe storage of ones reading glasses.

Dances with Shrapnel said:

Fast Eddie said:

I'd venture that Randy new his stuff!

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Yes he does. I would categorize Randy as an expert and all around good guy. He and his son Karsten operate their shop maybe 20 minutes from me and they are a pleasure to deal with. They also campaign and sponsor race bikes. Karsten goes faster than the wind. The Nourish shell is designed to fit the AMC envelope in the cradle so I don't know what, if any, liberties Randy took with the gearbox location. I vaguely recall having to use a longer belt but other Featherbed Norton Twin racer I recall also used a longer belt (longer than a Commando) so I just don't know.

Fast Eddie said:

What was it like to ride?

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Ha! You asked! It has not even been started. Way too many irons in the fire with other rebuilds in the queue, work, and races so perhaps next season or it may be reworked for the street.

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That is sacrilege John!

Can't you find some young, keen, hot shot kid to campaign some of this fine machinery for you?

I'd gladly volunteer, if I was young... or keen... or a hot shot...