Commando with a single sided swingarm idea.

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The F 750 spaceframe , had a monoshock ? ' cantilever ' rear end at one stage , or was tested.dunno if raced with it .

A pair of Hiem joint Longitudeinal link rods may be required ? Shock under the cradle would contain all the forces in
the powertrain assembly ? ?

Rubber IS self dampening ( almost ) hence Mini ' rubber ' suspension , & and Mosquio rubber ring in tube Oleo's .

SEEING youve got the welder out , A Commando I spotted at the Classic Races in N.Z. , not an entrant , had a third
ISOLASTIC MOUNT placed I believe under and behind the lower gearbox mounting bolt .
Proper ' tube / spacers / shims ' arangement .
A study of the force vectors / mounting points is food for thought . He'd said it was fine for playing Cowboys on gravel roads
850 Mk II . , as he lived several miles up one . :mrgreen:
 
motoalchemist said:
"Any shock that strays from horizontal starts loading the iso's" <<<< Hmmmm, need to go look at this closer....was never a issue in my mind
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That would be for shocks attached to the swingarm near the rear axle. For a horizontal single shock attached to the swingarm about 1/4 of the way from the spindle the load on the spring pushing it up would be x4 of what the rear wheel is carrying, and the force on the spindle the same amount, pushing that down.
 
rpatton said:
motoalchemist said:
"Any shock that strays from horizontal starts loading the iso's" <<<< Hmmmm, need to go look at this closer....was never a issue in my mind
Click to expand...

That would be for shocks attached to the swingarm near the rear axle. For a horizontal single shock attached to the swingarm about 1/4 of the way from the spindle the load on the spring pushing it up would be x4 of what the rear wheel is carrying, and the force on the spindle the same amount, pushing that down.
Click to expand...

I experimented with a single shock on my commando racebike. It was connected to the swingarm at 1/4 of the way back from the spindle. With the stock rear iso I had 1 1/2 to 2 inches of rear wheel travel undampened because of iso squish. I tried hard iso bushings and got it down to less but it didn't work on the track. The rear wheel chattered badly anytime you pushed it hard. I ended up shelving the idea.

The best my Commando ever handled on the track was with the top mount moved back until the shocks were vertical. Jim
 
comnoz said:
The best my Commando ever handled on the track was with the top mount moved back until the shocks were vertical. Jim
Click to expand...

Now isn't that an interesting comment. ...
 
Rohan said:
comnoz said:
The best my Commando ever handled on the track was with the top mount moved back until the shocks were vertical. Jim
Click to expand...

Now isn't that an interesting comment. ...
Click to expand...

Yes, Very interesting.....on my VFR rear swing arm Commando, we just tried to keep the shock in a position that reflected the stock VFR, so the shock is in its intended position.
 
Altering the rear shock geometry to suit a particular purpose better is something that works very well on twin-shock frames, but the same effect can be achieved by using shocks which have been properly designed and made to suit the application perfectly.
 
The shock angle alters the progression of the suspension, as the spring rate effectively changes as the suspension is compressed. Mounting the shocks in a more laid down position means more progressive suspension action and increased movement, while more upright means less progressive and less movement.
 
Certainly the performance of a damper is directly affected by the suspension geometry, but only a very small number of shock manufacturers take this into account, so very few people have rear suspension which works anywhere near as well as could be expected if purpose made dampers were used.
 
If the distance from the spindle to the top shock pickup point is further than the distance from the spindle to the bottom pickup point then the shock is going to actually be regressive. So just to get to neutral shock geometry it's going to be laid down to a certain degree, and progressive rates by geometry alone are even more so. But with progressive springs you can have a neutral or even a progressive net rate with any geometry you want, including vertical. And in the case of a Commando, you happen to have specific reasons for wanting a vertical shock. This isn't motocross style wheel travel here. I think most people are riding around with too little or no rebound damping at all, so the effect of geometry on the rate might be getting a little too nuanced.
 
Take a look at Tony Foales excellent book on motorcycle chassis design for a basic outline of matters related to suspension. Most people dont understand that rear suspension that works well isnt simply a matter of bolting on a pair of one size fits all shocks, often with the wrong springs fitted, and then hoping for the best.
 
The shocks I was using were custom built Works performance shocks. They had to be shorter when the shock was not angled forward and also the damping and spring rates were different.
Standing the shocks up helped my cornering speed and made the bike feel less springy. [almost like a featherbed with a smooth motor]. The bike was built with 4 isolastic mounts. I suspect it was because standing the shocks up took the isolastics out of the rear suspension damping. Jim
 
I've got it and you you can tell from the shape it's in that I've read it. You've probably seen the mc-chassis list mentioned before, I think you might like it, if you haven't seen it already. I think he was one of the original members and he's still on it. The level is over my head but I like to read the digest.

http://micapeak.com/mailman/listinfo/mc-chassis-design


Commando with a single sided swingarm idea.
 
Before yo'all go all esoteric on this, its old racer news that lifting the rear with longer shock alone helped C'do handling, I think it allowed faster sharper turning. So maybe vertical mounted shocks are doing that as much as changing the dampening rate and geometry. This would decrease the fork trail as well as the downward rear tire thrust vector on front isolastic.

It a swing arm can move side to side it translates as side to side slapping of the forks which only take a silly mm or so to feel it significantly instantly.
 
I maintained the same ride height. I did increase the effective spring rate a little because I lost some suspension travel. Jim
 
I would think altering the rear suspension geometry by making the shocks more upright, would be likely to mean it was easier to feel exactly what the rear wheel was doing, as well as reducing squat, which would mean more clearance in the turns. Same type of effects can be achieved through using modern fully adjustable shocks, but will never be quite the same as altering the mounting points.
 
Clearance was never an issue. Better feel was a big plus.

I never tried it until I was racing against modern bikes with the MRA. I had found that I couldn't stay with them when accelerating from the corner apex. They would be able to use full throttle immediately after the apex and I had to feed the throttle in slowly or I would run out of track on the outside of the turn. It was worse if the track was a little rough. I had tried different shock valving, springs and tires. Standing the shocks up was suggested by an experienced racer who happens to be married to my sister. I was impressed by the difference it made, especially on short tight tracks.

I even tried it on my streetbike. The rear upper mounts are still there. There was no real advantage on the street and it didn't look right. Jim
 
Sorry for posting and not responding sooner. I guess I stirred up the bee's nest a bit. I chatted with the mech at the shop here and he doesn't think the iso's are going to be a problem. Probably have to mount the mono shock clost to a 45 deg angle. he thinks it could work. I was also looking at the JS motorsports monoshock frame plans for $10. they might be worth looking at. I'm checking an old buddy I went to school with that builds Russel Mitchel bikes here in Canada to see what he may be able to do for me. I may just break down and buy the SS swingarm on ebay to check things out for now. I'm waiting for my motor to get finished for my 850 Roadster, so I have another week or 2 until I get to do some more work on it, so dreaming it is!!
 
Powereng03 said:
Sorry for posting and not responding sooner. I guess I stirred up the bee's nest a bit. I chatted with the mech at the shop here and he doesn't think the iso's are going to be a problem. Probably have to mount the mono shock clost to a 45 deg angle. he thinks it could work. I was also looking at the JS motorsports monoshock frame plans for $10. they might be worth looking at. I'm checking an old buddy I went to school with that builds Russel Mitchel bikes here in Canada to see what he may be able to do for me. I may just break down and buy the SS swingarm on ebay to check things out for now. I'm waiting for my motor to get finished for my 850 Roadster, so I have another week or 2 until I get to do some more work on it, so dreaming it is!!
Click to expand...

If you have to ask a chopper guy for chassis advice, you're in BIG trouble.
 
Well he may be able to make the frame if I get the plans so that may be a way to get the job done a little cheaper/easier.
 
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