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Jeandr said:
I'm sure the offset crank helps kicking it. Do you start your Norton the same way?
80° crankshaft
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I'm sure the offset crank helps kicking it. Do you start your Norton the same way?
I have a problem with the theoretical plane that people talk about. If the contact points of the iso's were right on the centerline and the stress put on them was right in the middle of them then it would make sense. The iso contacts aren't on line with the center and the source of the load is at the contact patch of the rear tire. When the rear wheel is forced in one direction the rear iso is loaded on one side, the front iso is getting pressed on the other, and the headsteady is too, only more so. If the wheel is pushed to the right then the right side of the rear iso is loaded and the left side of the other two are. The opposing sides of the same iso's may as well not exist because there is no contact. The plane then is from the right rear to the front left crossing the centerline at an angle. The engine vibrates in line so it's going to be hammering the iso's and binding them. It's probably why you cant set them to nil. Add the fact that the contact patch of the rear tire is a good distance away from all of them and everything becomes magnified by leverage.ludwig said:
Rod-end linkages put as close to the centerline as possible would be good because the distance would just be half the diameter of the ball, but you can't get away from the leverage deal. Four seems better to me just because it spreads out the load a little on that flexible frame
bpatton said:
Not really because the isos are guiding surfaces so they definitely are NOT punctiform in their load path. I agree however that because of the flexibility of the frame the idea of the isos is a bit spoiled....
The idea of the third iso and the theoretical plane is slightly different IMHO: If you only run the two standard isos and the two rubber thingies instead of a head steady the torsional distortion fed into the whole structure will cause the top rubbers to compress and therefore load the edges of the two STD isos far higher than with a third iso. Edge loading means increased friction means more vibration and more wear.
Rod ends are fare more effective with respect to frame flexing but you'd need for anyway - not because of spreading the load but for correct degree of freedom. Three rods would force the cradle to perform a twisting motion against the frame and this would load the suspension.
Tim
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Jeandr said:
I close my eyes and dream of the bike starting one day.
Back in the day with my Interstate I'd push it past TDC and kick it over. Kind of slow, maybe two kicks.
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I don't know what he's getting at either Bob.
My experience of the tri-links is it allows smashing down
rear suspension loading for un- expected extra hook up grip.
I can sure feel the forks and frame twist up but it just
seems to relieve all tire conflict and then un- wnds in one sling
shot like action w/o rebound or springing. The wildest effect is how
much pilot can cause chassis to twist up and stay twisted
till pressure let off. When I load moderns half that much
they suddenly start juddering the front tire out of traction
with the chassis whip amplifying to tank slap.
A Watt's linear motion can be obtained by linking above
one iso mount and below the other with long enough radius
rods there is no bind or tipping in the range of engine and
road load oscillation.
http://www.brockeng.com/mechanism/Watt.htm
http://www.brockeng.com/mechanism/Watt.htm
Throw in the long even 360' power pulses on rubber dampened
drive train and the twist up into rear suspension loading tire patch
just begs for extra torque piled on at apex climaxes.
What works on very rigid bikes does not always apply to Commandos,
thank goodness.
hobot
My experience of the tri-links is it allows smashing down
rear suspension loading for un- expected extra hook up grip.
I can sure feel the forks and frame twist up but it just
seems to relieve all tire conflict and then un- wnds in one sling
shot like action w/o rebound or springing. The wildest effect is how
much pilot can cause chassis to twist up and stay twisted
till pressure let off. When I load moderns half that much
they suddenly start juddering the front tire out of traction
with the chassis whip amplifying to tank slap.
A Watt's linear motion can be obtained by linking above
one iso mount and below the other with long enough radius
rods there is no bind or tipping in the range of engine and
road load oscillation.
http://www.brockeng.com/mechanism/Watt.htm
http://www.brockeng.com/mechanism/Watt.htm
Throw in the long even 360' power pulses on rubber dampened
drive train and the twist up into rear suspension loading tire patch
just begs for extra torque piled on at apex climaxes.
What works on very rigid bikes does not always apply to Commandos,
thank goodness.
hobot
bpatton said:
The situation is that of a kinematic chain http://en.wikipedia.org/wiki/Kinematic_chain : If we regard the frame as the support structure the engine cradle has six degrees of freedom relative to the frame: It can move along and rotate around three axes. Each rod-end link takes away one DoF - so three links leave three DoF and as you want to create a planer motion this is one degree of freedom too much. The twisting motion would occur if the three links are (close to) parallel to each other and (almost) perpendicular to the X-Z-plane of the bike. The cradle could then rotate relative to the frame but the links would force it to move sideways with the rotation - a twisting motion. The suspension would counteract this but in a very random way because it mixed the behavior of a rod link with that of a spring/damper. To decouple this you'd need to take one further degree of freedom away and that would be with a fourth link (almost) parallel to the other three and (almost) perpendicular to the X-Z-plane. The fourth link would force the cradle to move on a sphere (presuming the links are of equal length and parallel otherwise it would be a more complex surface than a sphere).
It's the same idea as that of a multi-link suspension ( http://en.wikipedia.org/wiki/Multi-link_suspension ) except for the fact that the purpose of the suspension is to provide one degree of freedom and therefore it needs five links.
A three bar linkage on a Commando would probably lead to a motorcycle that is already pretty stiff in torsion but this would rely on the iso rubbers and the suspension to take some of the loads in the linkage. The fourth bar would let them do what they are supposed to do (and feeding the rear suspension forces into the engine cradle like some of the mono shock arrangements do would finish the job....)
Tim
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Yes sir Tim and I have tried to see why this expected geometric linkage
binding has such an exception to the rule,
revealing a new level of operation to model and reveal in.
In Commando practice it Only takes the one rear, low, far, back mounted
Helm's link to transform isolastic Commando load handling way beyond
what is known to limit all other motorcycles.
But w/o the front link one can feel the oscillations of the front
following road texture, though don't bother holding any line
ya can stand in cornering.
But w/o the top link one can feel the wind buffet jostling the
chassis though it don't bother holding any line ya can stand cornering.
Then with all 3 set to neutral slack, one can feel the power
pulses frequency on tire patch hysteria to appreciate how far ahead
of the pack a rear link tamed isolastic Commando is >
like a loaded Goldwing in free fall with ballistic jet aiming.
360' crank then becomes an a traction asset,
flexy thin steel tube frame then becomes as advantage,
riding to limits of leaned over traction becomes so soothing
and effortless, invites one into to faster funner ways around.
I know what yo'all are missing out on - but do you?
hobot
binding has such an exception to the rule,
revealing a new level of operation to model and reveal in.
In Commando practice it Only takes the one rear, low, far, back mounted
Helm's link to transform isolastic Commando load handling way beyond
what is known to limit all other motorcycles.
But w/o the front link one can feel the oscillations of the front
following road texture, though don't bother holding any line
ya can stand in cornering.
But w/o the top link one can feel the wind buffet jostling the
chassis though it don't bother holding any line ya can stand cornering.
Then with all 3 set to neutral slack, one can feel the power
pulses frequency on tire patch hysteria to appreciate how far ahead
of the pack a rear link tamed isolastic Commando is >
like a loaded Goldwing in free fall with ballistic jet aiming.
360' crank then becomes an a traction asset,
flexy thin steel tube frame then becomes as advantage,
riding to limits of leaned over traction becomes so soothing
and effortless, invites one into to faster funner ways around.
I know what yo'all are missing out on - but do you?
hobot
hobot said:
I read your post three times and have - once again - absolutely no idea what you are talking about. I don't know why you keep on mentioning a Watt's linkage for years now - it's pretty much irrelevant for the given task of controlling the XZ-plane movement as intended. Watt is 2D and is used on live axles to control lateral movement of one single point (around which the axle can rotate - you don't want the cradle to rotate, do you?). Apart from that I'd really like to see how on earth you place two rods of sufficient length inside a motorcycle frame....and so on. Sorry to say that but from the minimal facts I'm able to distill from your posts all I can say is that your concepts appear half-cooked at best.
I have the feeling that I'm missing out on a parallel universe with a completely different set of rules of a) physics and b) grammar.
Tim
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I know better than to respond to hobot's comments... but I will anyways. I sadly understand some of what he's trying to articulate.
The Watt's linkage for controlling the movement of components is one of the few examples that illustrates how to control the cradle of a Commando using rod end links. It may not be perfect but there aren't a lot of examples out there. Other examples I've heard of but not studied are the ones used on some Harleys and Buells.
Using words to describe the movement and function of components is difficult. The only way I know of doing it is will illustrations but I'm a visual person.
The Watt's linkage for controlling the movement of components is one of the few examples that illustrates how to control the cradle of a Commando using rod end links. It may not be perfect but there aren't a lot of examples out there. Other examples I've heard of but not studied are the ones used on some Harleys and Buells.
Using words to describe the movement and function of components is difficult. The only way I know of doing it is will illustrations but I'm a visual person.
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Thanks Jean.
This thread has gotten off topic.
Great Vids but I don't think the sound comes through very well. It's hard to get an accurate representation of the sound with most video cameras.
Have you heard from Eagan? Any updates on how the bike is doing?
He couldn't kick it over when I was there either. I hope he's sorted this out or found the secret handshake so to speak.
Will
This thread has gotten off topic.
Great Vids but I don't think the sound comes through very well. It's hard to get an accurate representation of the sound with most video cameras.
Have you heard from Eagan? Any updates on how the bike is doing?
He couldn't kick it over when I was there either. I hope he's sorted this out or found the secret handshake so to speak.
Will
willh said:
I spoke to him about a month or two ago and he was busy with other things so he didn't have his bike running. I think he is waiting for a decent electric starter so he can start it without having a gorilla to kick it to life :wink: He said he would come and visit us sometime this summer, but alas, in his car. I really think he got more enjoyment out of building it than he would get riding it and I'm not criticizing him, I'm in the same boat :mrgreen:
Jean
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Jeandr said:
As has been mentioned many times it's a properly set up bike and technique. I would think that the 80° crank would be easier to kick.
Had the Norton Commando been equipped with a proper electric starter, a decent front disc brake and didn't leak oil like a BP oil well, it may have been in business yet today, the new Norton notwithstanding. I bought a 69 Commando and my buddy bought a Honda CB 750. I felt I really got screwed.
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swooshdave said:
I personally have no problem kicking over my 850. 215 lbs and 25 years of practice bringing bikes to life this way. For me an electric starter is just extra weight I don't need, but not all who enjoy these bikes have the girth or technique, some have failing health, bad knees, or ankles etc.
I don't think the offset crank would make any real difference.
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