Commando motor in solid frame

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Fast Eddie said:
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 ?
Click to expand...

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.
Click to expand...

I appreciate that sort of glass-half-full thinking. This is precisely how current GP race machines are constructed, although with no thought as to using leftover space, since there isn't any! The engines are moved as far forward as possible and any increase in wheelbase is mitigated by ever-steeper front rakes, and the subsequent reduction in trail is mitigated by manipulating fork offset. Rider position has also moved forward from the days when your butt was nearly vertical to the rear axle. With the prototypes at the top of the food chain, all these factors are fluid, ever-changing and constantly fettled to suit circuit, rider and conditions. Overall frame stiffness reached a peak and was backed away from to add the flexibility necessary to make the frame act as suspension at max lean.
 
Interestingly, Dave Degans preferred unit motors in the Tritons he built as they are so much stronger, both regarding the engine and gearbox.

He used his endurance racing experience to arrive at what he thought was the best position of the motor.

Having ridden both unit and pre unit Tritons, I couldn't tell any difference quite frankly. Handling of a Triton is far more about condition and choice of forks, shocks, tyres, than it is about unit or pre unit power IMHO.
 
i haven't or don't recall running across info for a 67 bsa commando engine combo?
 
Fast Eddie said:
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 ?
Click to expand...

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.
Click to expand...

Would anyone really fit larger pivot mounting plates to a good Featherbed frame - why not simply use a frame of the right configuration in the first place ? I any case, there is a problem with the swing arm fouling the frame tubes when you fit a different one to a Featherbed to get bigger rubber onto the bike. As you move the pivot forward the radius of it's movement gets larger at the critical point where it would foul. What really amazes me is how Chromie McCandless got the Manx featherbed frame so right - there is very little room for modification to improve it. My feeling is that the Slimline frame is disgusting. A replica Manx frame is a much better option.
 
acotrel said:
Fast Eddie said:
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 ?
Click to expand...

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.
Click to expand...

Would anyone really fit larger pivot mounting plates to a good Featherbed frame - why not simply use a frame of the right configuration in the first place ? I any case, there is a problem with the swing arm fouling the frame tubes when you fit a different one to a Featherbed to get bigger rubber onto the bike. As you move the pivot forward the radius of it's movement gets larger at the critical point where it would foul. What really amazes me is how Chromie McCandless got the Manx featherbed frame so right - there is very little room for modification to improve it. My feeling is that the Slimline frame is disgusting. A replica Manx frame is a much better option.
Click to expand...

I also much prefer the wideline from an aesthetic perspective and that's what I'd use if I were embarking on a special build. Especially for a road bike.

However, I raced both and when using a 'modern' riding style (i.e. hanging off a bit) I used to get large bruises on my inner thigh from the wide tank on a wideline. The slimline gives better ergonomics.

And, I know its been debated many times and probably will be for ever, but I firmly believe there is zero handing difference between wideline and slimine.
 
The Featherbed was definitely a great leap forward at the time. All the tributes paid in rehashes of all sorts for years and years prove the viability of the twin-loop cradle. But it wasn't the end-all, be-all, even of tubular frames. Witness the Seely Mk II, the Rob North triple chassis and others (I'm sure) that show there was room for improvement on the original concept. To say it was "right" or "perfect as-is" is to ignore reality. Time and technology march on and new factors (horsepower!) must be coped with.

So why couldn't someone build a twin-loop cradle frame with steeper rake, longer, wider swingarm and modern ergos (forward weight placement)? And while they're at it, make it narrow at the top, wider at the bottom and stiff enough to accommodate any amount of power desired. It's already been done by someone who isn't stuck on the past


Commando motor in solid frame



Commando motor in solid frame
 
Danno said:
So why couldn't someone build a twin-loop cradle frame with steeper rake, longer, wider swingarm and modern ergos (forward weight placement)? And while they're at it, make it narrow at the top, wider at the bottom and stiff enough to accommodate any amount of power desired. It's already been done by someone who isn't stuck on the past

They do Danno. One such is the Hyde Harrier, chassis made by Harris. This is one I nailed together:

Commando motor in solid frame


Commando motor in solid frame


And while I'm on photobucket, this is the bike I built and raced and then put on the road. I designed the frame myself as a featherbed inspired design but around a unit motor. I screwed up the swing arm pivot point. Took me a while to realise and remedy it!

Commando motor in solid frame
Click to expand...
 
You sir "nail together" some of the most beautiful bikes I've seen. I especially like the Harrier, but your current Commando also is pretty in blue. Are you really going the JPN route? I'm sure it too will impress.
Lance
 
Very nice work there Sir; especially that triple.

I have contemplated building and campaigning a Triple but 1.) getting too spread out with stuff and 2.) I don't have the historic knowledge base on the tricks to get a Triple to really perform - I would have to rely a lot on others (ex. how do you keep that pesky middle cylinder happy, rod & main lubrication issues, etc...). As a side note, is Phil Pick still doing? A long while back I heard he had a bad get off and ????


So what does that Hyde Harrier Triple weigh in at?
 
Thanks for the nice words gents.

John, I'm not sure if Phil is still 'doing it' he kinda dips in and out somewhat depending on the rest of his 'work life balance'.

P&M are big triple players here. A gent by the name of Neil Beadling (trading as Nova Classics) is, IMHO, THE go to triple guy it he UK. He built my Harrier motor and mightily impressive it was too.

With either P&M or Nova Classics though, if you want a top drawer fast triple, you need deep pockets and long patience !!

John, sorry matey but I can't remember the weight of the Harrier and I sold it a while back. It was light though, most of the body work that looks black in the pics is actually carbon fibre. The motor was much lighter than stock due to lightened crank and P&M belt primary and Newby clutch. FYI, I worked on the chassis arrangement with a good racing / engineering friend. It handled like a 1990s GSXR and went like one too! It wanted to be ridden 10/10th all of the time. It was a very fast machine, and fun... when you were in the mood. But therein lied the problem, one can buy a 1990s-2000s GSXR for next to nowt and have the same fun! Plus the Harrier had kinda lost some of that elusive 'character' that we like about old bikes. It was a fabulously successful engineering exercise, but a less successful 'enjoyable road bike' exercise.
 
Beautiful machines you cobbled up there Eddie.

I am curious, not that I want to build one, but can you elaborate on "I screwed up the swing arm pivot point. Took me a while to realise and remedy it!"

Slick
 
texasSlick said:
Beautiful machines you cobbled up there Eddie.

I am curious, not that I want to build one, but can you elaborate on "I screwed up the swing arm pivot point. Took me a while to realise and remedy it!"

Slick
Click to expand...

One has to keep on cobbling...

Ref the swinging arm pivot, basically, I put it too low. So when under compression (i.e. when going quick in a long bend) the rear wheel spindle, and gearbox spindle centre lines would be above the swinging arm spindle centre line. A school boy error for anyone who knows their stuff, which I didn't (or don't)!
Then, during certain throttle openings, the motor would 'fight against' the rear shock springs. Meaning the motor would be trying to pull the wheel up whilst the shock springs were trying to push it down, at a certain point, this reached a natural resonance, which showed up as a 'patter'. Mostly I'd just press on through it, although their were times it felt a tad too close to the edge!
 
Nigel,
What a smashing pair as they say in the best Carry On films. I believe the gearbox, swingarm, & rear spindle should all be in line at one third rear suspension travel. Martin Russell did tell me he moves this up a little (I think) on certain frames. Something to do with preventing squat under acceleration.
 
Whenever I've made engine plates, I've always tried to keep the centre of the gearbox sprocket about 1/4 of an inch above the line between the centres of the rear sprocket and the engine sprocket
 
Here's what I did on my Monoshock space frame racer to mamimize the length of the swing arm. There is a 1/2 round tube (tube cut in 1/2 the long way) to give structural support and still make room for the swingarm.

Commando motor in solid frame


The bike below as Ken Canaga set it up when it got on the BOTT podium with Rob T riding.
Commando motor in solid frame


My Avatar shows me on an earlier version of this bike powering out of a turn with a multi jap bike not far behind. All this was in the late 80s.
 
Fast Eddie said:
Danno said:
So why couldn't someone build a twin-loop cradle frame with steeper rake, longer, wider swingarm and modern ergos (forward weight placement)? And while they're at it, make it narrow at the top, wider at the bottom and stiff enough to accommodate any amount of power desired. It's already been done by someone who isn't stuck on the past

They do Danno. One such is the Hyde Harrier, chassis made by Harris. This is one I nailed together:

Commando motor in solid frame


Commando motor in solid frame


And while I'm on photobucket, this is the bike I built and raced and then put on the road. I designed the frame myself as a featherbed inspired design but around a unit motor. I screwed up the swing arm pivot point. Took me a while to realise and remedy it!

Commando motor in solid frame
Click to expand...
Click to expand...

I agree with everyone's assessments. Fabulous machines. The Hyde Harrier looks much like a Rob North-framed Beezumph factory racer. Pity neither one is Commando-powered.
 
And then there's this one.

Commando motor in solid frame


Commando motor in solid frame


This was the price list from Mick back in '86 or so when I bought the frame kit from him. I never used it, and now I'm trying to decide whether I'll ever get around to building a bike with it, and whether maybe I should just sell it to someone who will.

Commando motor in solid frame


I think he had 10 of them made by Miles Engineering. I'm still looking through Classic Bike and Classic Racer for pictures of the one Mick built and raced, with full JPN style fairing, but haven't found it yet.

I've seen a couple of them for sale in the past few years as complete bikes. The last one was listed for 16,500 pounds, but I don't know what it actually sold for. These are a couple of the pictures from the ad for it. He didn't include any good full view pictures.

Commando motor in solid frame


Commando motor in solid frame


Ken
 
Hi all

This is an intresting thread. Love the JPN framed bike. What is the frame? I remember a few with the swinging arm pivot in the engine plates.
Eddies Harrier build was a great read at the time but in hindsight high lights updating a classic bike too much. ( I still would have kept it :D )
Kens unused Rob North Commando frame is facinating. I read that article at the time & wondered, as I was struggling to get eligibility on my race bike, how this frame would be allowed to race with the CRMCC. I am a lover of anything special, shed built one offs etc & "Eddie" has built a number of corkers. He moves them when the time is right. I would still have the Dresda 8 valve Bonnie, so the Harrier would never have got built.

Chris
 
lcrken said:
And then there's this one.

Commando motor in solid frame


Commando motor in solid frame


This was the price list from Mick back in '86 or so when I bought the frame kit from him. I never used it, and now I'm trying to decide whether I'll ever get around to building a bike with it, and whether maybe I should just sell it to someone who will.

Commando motor in solid frame


I think he had 10 of them made by Miles Engineering. I'm still looking through Classic Bike and Classic Racer for pictures of the one Mick built and raced, with full JPN style fairing, but haven't found it yet.

I've seen a couple of them for sale in the past few years as complete bikes. The last one was listed for 16,500 pounds, but I don't know what it actually sold for. These are a couple of the pictures from the ad for it. He didn't include any good full view pictures.

Commando motor in solid frame


Commando motor in solid frame


Ken
Click to expand...

That looks quite stout. Do you have the entire kit and what would it need to make a complete machine?
 
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