80° crankshaft

Re:

panic said:

1. 90° produces the best balance of motion between the 2 cylinders - this will always be 90° regardless of engine design, etc.....

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This is only true regarding mass forces, not mass moments. And the isos demand that the engine produces no mass moments, otherwise the whole idea doesn't work anymore. Putting anything else than a 360deg crankshaft in a Commando is simply bullshit - doing something for the sake of doing it and actually against the maths. On a rigid mount chassis it's okay but it doesn't really "cure" vibrations, it just changes the pattern which can be a good thing but also a bad thing. The only real reason for going to 90deg is that it can be balanced with a single balance shaft which is what Yamaha did on the TRX and what Triumph does on their current twin. Does anybody of the no-360deg-fraternity put a balance shaft into their engine?


Tim

I want one of those windscreens! What kind is it?

Re: Re:

Tintin said:

panic said:

1. 90° produces the best balance of motion between the 2 cylinders - this will always be 90° regardless of engine design, etc.....

Click to expand...

On a rigid mount chassis it's okay but it doesn't really "cure" vibrations, it just changes the pattern which can be a good thing but also a bad thing.


Tim

Click to expand...

I believe that for a rigid mounted bike like a P11, some light weight internals, offset crank, and balancing can turn it from f'n miserable to being a pleasure to ride.
Yeah it should still vibrate, but in a good way
My Duc vibrated too but not in a way that bothers you, just letting you know what's going on.

I have never felt good riding a rubber mounted engine-trans-swing arm bike, be it Norton, Harley or Buell.

Re: Re:

Tintin said:

This is only true regarding mass forces, not mass moments. And the isos demand that the engine produces no mass moments, otherwise the whole idea doesn't work anymore. Putting anything else than a 360deg crankshaft in a Commando is simply bullshit - doing something for the sake of doing it and actually against the maths. On a rigid mount chassis it's okay but it doesn't really "cure" vibrations, it just changes the pattern which can be a good thing but also a bad thing. The only real reason for going to 90deg is that it can be balanced with a single balance shaft which is what Yamaha did on the TRX and what Triumph does on their current twin. Does anybody of the no-360deg-fraternity put a balance shaft into their engine?


Tim

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The only other potential benefit I've seen discussed for the offset cranks in vertical twins like the Norton is better hookup in dirt track racing. I have no idea if this actually works. I've only ever ridden my Nortons in the dirt unintentionally, so have no experience to rely on. As I recall, the theory is that you get two torque impulses to the tire/dirt interface, and then a longer period for it to recover traction. It looks like an effort to get closer to the HD firing order, which seems to work extraordinarily well on dirt.

Ken

Re: Re:

lcrken said:

Tintin said:

This is only true regarding mass forces, not mass moments. And the isos demand that the engine produces no mass moments, otherwise the whole idea doesn't work anymore. Putting anything else than a 360deg crankshaft in a Commando is simply bullshit - doing something for the sake of doing it and actually against the maths. On a rigid mount chassis it's okay but it doesn't really "cure" vibrations, it just changes the pattern which can be a good thing but also a bad thing. The only real reason for going to 90deg is that it can be balanced with a single balance shaft which is what Yamaha did on the TRX and what Triumph does on their current twin. Does anybody of the no-360deg-fraternity put a balance shaft into their engine?


Tim

Click to expand...

The only other potential benefit I've seen discussed for the offset cranks in vertical twins like the Norton is better hookup in dirt track racing. I have no idea if this actually works. I've only ever ridden my Nortons in the dirt unintentionally, so have no experience to rely on. As I recall, the theory is that you get two torque impulses to the tire/dirt interface, and then a longer period for it to recover traction. It looks like an effort to get closer to the HD firing order, which seems to work extraordinarily well on dirt.

Ken

Click to expand...

That and favorable rules committees... :roll:

I've had enough experience with slight power pulse imbalances
in Commandos to know they are very sensitive to side/side
mass inertia shifts that isolastics are not designed to absorb.

I'm sensitive to the power pulse spread and dampening, in
loose stuff to best pavement leaned far with hi power on.
So far can find anything that hooks up better than 360'
rubber dampened Commando.

What may apply and help solid mounted chassis/engines
may not apply to the Commandos with the whole power train
rubber mounted to take up slack both up/dn as well
as the fro/aft traction hits.

Rear iso linkage seems to solve any need for a rigid chassis and
fixed engine mount. Any vibes or throbs to me off
idle is an annoyance like other utilitarian appliances.

BTW the shifter is reversed to allow a minimalist rear set
peg and retain the gear pointer. But it also reverses
the shift pattern unless a reverse selector cam fitted too.

Delicious creation, thanks for sharing.

hobot

hobot

ludwig said:

what's the story with the gear indicator ?
and what's the thing below the box ? :

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I think the thing below the box is the frame cross bar for the fourth isolastic mount. Same as Dreer was doing on his early bikes. The top Iso is Vernier as well. He was running them at .005" if memory serves.

Gday Jean,
many thanks for posting those nice pics of a gorgeous build. Some blokes are clever being able to give birth to such a dream bike. Alot of worthy hours have gone into it. It was the path I was going to take in rebuilding a Norton but have gone the featherbed direction, with 920 cc, 90 deg Offset from Geoff Collins. My crank is the lighter version, weighing some 8 lbs lighter than standard.
Good to read Willh,s & PJL,s positive reports on the sound and smooth running. Theres alot of theory floating around, but sometimes practical or in practice, comes out on top.
Panic, thats a good read on the math too.
Jean, youre a clever man, can you post a link with the sound please?
rgds Foxy

Amen Ludwig, any rubber cushion area added to the two factory isolastic
will inherently move isolation rpm range upward before iso's can dampen.
Factory head steady is not involved with restraining engine vertical
orbital, just some side motion on corner loads and from
wind and road texture slaps at the stem into front iso.

As far as I'm concerned all vibration and handling issues solution
has been found and tested to find its
Flabergastingly Fabulous and so simple a hay seed can do.

hobot

hobot said:

Amen Ludwig, any rubber cushion area added to the two factory isolastic
will inherently move isolation rpm range upward before iso's can dampen.
Factory head steady is not involved with restraining engine vertical
orbital, just some side motion on corner loads and from
wind and road texture slaps at the stem into front iso.

As far as I'm concerned all vibration and handling issues solution
has been found and tested to find its
Flabergastingly Fabulous and so simple a hay seed can do.

hobot

Click to expand...

You are absolutely right sir.
This is not my Motorcycle. But it sure is nice. These are toys, toys with heritage, soul, and character, but toys non the less. I could not nor would want to put this much time and money into a flawed chassis. Might as well buy a H-D and put chrome on it. Any bike with a rubber mounted swingarm will not give good rear end feel. This isn't just a Norton thing. Take one of the air cooled Buells out for a spin. They are numb. Everyone wants a smooth twin. The Isos deliver. Do the deliver a crisp ride? No
I love my old lump but I will never pretend that it is fast. I have a real sporting twin for that.
In the 15 years I've had my Commando I tried everything to get it to where I thought it should be. The problem wasn't the bike, it was me. My expectations were too high.

The crank offset does what it is supposed to. The Commando frame is a waste of the benefits. The frame/isos were designed for a 360 degree crank. Put that same engine in a P11, Trackmaster, or featherbed with the proper balance factor and the thing should be relatively smooth. The remaining vibrations easily dealt with.

Here's a mock up of my dirt road Norton project. This is a good candidate for the 80 degree crank.


Now that I've said what I have to say let the flaming begin. :twisted:

ludwig said:

willh said:

..I think the thing below the box is the frame cross bar for the fourth isolastic mount. Same as Dreer was doing on his early bikes. The top Iso is Vernier as well. He was running them at .005" if memory serves.

Click to expand...

If that is so , than it would be a mistake .
Dreer added an iso below the box , bet removed the head steady .
3 point are allways in a plane , 4 are not .
If you have 4 isos set at .005" , then as soon as the frame flexes more than .005" ( = allways ) , 2 of the 4 isos will bind .

Click to expand...

I don't remember if the bottom was there last time. Every time I saw it, details had changed. I wouldn't be surprised if it was still there. I saw a Becker racing Commando with frame bracing behind the cradle with a block of rubber attached to it that was wedged into the back of the cradle. Wonder what he was trying to do.

Is that your blue commando in your avatar? If it is I like your exhaust solutions, particularly the mounting the pipes to the cradle.

willh - your mock up is similar to my P!! that got me so imprinted
on Norton twins and berserk performance.

I too once thought exactly as you and everyone else does that
rubber mounted drive train in flimsy chassis was a hindrance
to handling extreme or sustained oscillating loads, and for
sure it is - but also aflicks the most rigid elite motorcycles
just the onset is moved up a bit faster and hits at way
higher frequency. Not fun no more.

There is an exception to this rule, that is a deeper rule
or principle operating, if ya can uncover it.
My experience is Watt's like linkage makes other
two wheeled craft dangerous corner cripples. unworthy
opponents not in same league as 4wd turbo drift cars
and Race Karts.

I know too well how to upset any bikes handling
and traction in various ways, yet feeling young enough
I must induce in order it to avoid it in future flings.
So far have not been able to upset my tri-linked Combat.
I know limits of ever other bike but don't yet know
what all I can get away with on Ms Peel, so smooth
and sedate feels steadier than a loaded down Gold Wing.

Try an experiment to get concept of the load tolerance
rear link provides, get going about 20-or more mph
and suddenly throw in a tad of straight steering, chassis
will twist and wipe back at you aiming to hi side.
Peel can take that and hold it, but requires constantly
increasing power to resist the hi side, though too much,
or rather just enough extra, trips out into a low side, which turns
out to be life saving action when next turn at 90' is
passing your shoulder and no way can a human turn
bars or lift bike fast enough before off the edge across the road.

Ahhhhhhhh... don't need to be an athlete on a tamed
Totally Neutral Handling Commando.

hobot




hobot




t

Foxy said:

Gday Jean,
many thanks for posting those nice pics of a gorgeous build. Some blokes are clever being able to give birth to such a dream bike. Alot of worthy hours have gone into it. It was the path I was going to take in rebuilding a Norton but have gone the featherbed direction, with 920 cc, 90 deg Offset from Geoff Collins. My crank is the lighter version, weighing some 8 lbs lighter than standard.
Good to read Willh,s & PJL,s positive reports on the sound and smooth running. Theres alot of theory floating around, but sometimes practical or in practice, comes out on top.
Panic, thats a good read on the math too.
Jean, youre a clever man, can you post a link with the sound please?
rgds Foxy

Click to expand...

I will, give me a bit of time. Please be aware that bike does NOT belong to me, I just did the electrics on it. The circled thing below the engine I think is only an extra cross brace added to the frame just like the one seen on the two downtubes.

Jean

Looks awesome. Great restoration job. I have been curious about the 80 and 90 degree cranks for some time now.
Would like to here it run. ravidano@comcast.net

3 videos with sound at:







Jean

that is a ducati windscreen?

Looks like a real beast to start, mmm.. also sounds like one when running!! yep I like it very much, many thanks for your efforts Jean in making the veiwing and sound possible. I appologise for smiling(LOL) when watching the kick starting...
O.K. Jean could you tell us in your words what you think of the offsetcranks running? I noticed it wasnt rocking down the drive.
Regards FOXY

Foxy said:

Looks like a real beast to start, mmm.. also sounds like one when running!! yep I like it very much, many thanks for your efforts Jean in making the veiwing and sound possible. I appologise for smiling(LOL) when watching the kick starting...
O.K. Jean could you tell us in your words what you think of the offsetcranks running? I noticed it wasnt rocking down the drive.
Regards FOXY

Click to expand...

IMOHO, overkill on a Commando, it would have been something to do on a Featherbed Norton like mine except I didn't have the money to burn. If I had to do an engine for the long haul, I would get a crank from Dominator Engineering ( http://www.britishclassicbikes.de/ ) with 850 barrels but with a shorter stroke to make it a 750 and set of pistons and rods from Jim Schmidt ( http://users.gotsky.com/jimschmidt/nortonrods.html ) By doing so, the engine would be a lot smoother than even an ofset crank I would think. If I wanted an engine with more power, I would get a Kawasuzuhonmaha.

Jean

The bike didn't even move when revved. Don't like the sound tho.

That one guy fanned that kickstarter like a two stroke.

swooshdave said:

The bike didn't even move when revved. Don't like the sound tho.

That one guy fanned that kickstarter like a two stroke.

Click to expand...

Now who are you calling a two stroker :?: I'm the one who got it started, and I can tell you cycling legs helped a lot (along with 190lb of body weight :wink: ).

Jean

I could probably still start my RD400 with my hand :lol: