To Link or Not?

My my my

All this talk about under the bike linkage.

However did Peter WIlliams win the Isle of Man and dominate the British short circuit tracks way back in 1973 WITHOUT all the marvelous benefits of today's underbelly "links"? Or maybe Peter DID link up down there way back then?


Are the top people today racing Commandos all knowledgeable about and have installed these links?

And are all of us owning unlinked Commandos just fools who are missing out on such great handling improvement?

The concept and pictures seem and look pretty cool. But is there any empirical tested evidence of superiority?

That's a good question.

Mine (linked) feel rock-solid, but that's as compared to floppy old beaters that had work isolastics and loose swingarm spindles. Every time I've "gone in", I've gone ALL in.

So let me get this straight, you guy's have done away with the Iso's completely and are using (3) sets of linked rose joint connections simalar to the D.Taylor and J.Comstock (CNW) headsteadies? How is that working vibration wise? Sounds solid as a rock & adjustable. But what about them good vibes?

No, the rod links COMPLIMENT the isolastics, they don't REPLACE them.

They limit the range of motion of the rubber to strictly fore/aft and up/down, no side-to-side.

The result is a much truer swingarm path, and of course much truer rear wheel path, relative to the chassis.

gtsun said:

So let me get this straight, you guy's have done away with the Iso's completely and are using (3) sets of linked rose joint connections simalar to the D.Taylor and J.Comstock (CNW) headsteadies? How is that working vibration wise? Sounds solid as a rock & adjustable. But what about them good vibes?

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The links don't do away with the ISOs, the links are providing a better control of the side to side motion than the one given by the teflon washers and shims. The rubber bushings are still used to let the engine vibrate while the frame doesn't. While building mine, I found that the top link was the one needing to be replaced the first. If you look at all the racers, they run with the Norvil type head steady. I haven't run with mine yet, and I make no claims, but I think it should work better if not as well as a well adjusted Norton with stock ISOs AND a better head steady than the little rubber isolators.

Jean

Do the better Commando racers today have this linked set up? I presume so if it makes the rear wheel track truer?

Would there not be more felt vibration because all side to side iso movement is eliminated?

If the purpose to eliminate side to side movement, then why not just snug up the ISO clearance to near zero for the same effect?

Are these links all that noticeably "necessary" assuming a rod link head steady and well set up front and rear ISOs set tighter than the 10 thou spec?

Can, as Hobot emphatically states, a fully linked Commando really stay with, spank, "modern" sport bikes in the handling department?

A 40 year old, but well sorted, Commando with all this extra linkage is transformed handling wise because of a truer rear wheel corner, handle with today's Ducatis
and Hondas, etc?

If so, wow, all that more great performance just by adding these lower links?

There are kits and testimonials all over the web stating similar results on linked Harleys. The theory makes sense.

Do the better Commando racers today have this linked set up? I presume so if it makes the rear wheel track truer?

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Not that I've read about.

If the purpose to eliminate side to side movement, then why not just snug up the ISO clearance to near zero for the same effect?

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Then you couple more vibration to the frame. The rod links still allow the isos to work, but only in a vertical direction. Lateral motion is eliminated.

A 40 year old, but well sorted, Commando with all this extra linkage is transformed handling wise because of a truer rear wheel corner, handle with today's Ducatis
and Hondas, etc?

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No. You can't turn a sow's ear into a silk purse. You can, however make some of the "hinged in the middle" feeling go away.

The isos are rubber biscuits. The engine trans and swing arm all hang on these. When lateral force is applied to the rear tire and transmitted to the front and rear iso. What happens is the engine cradle flexes, opposite the force applied to the rear tire. This in turn causes the rear tire to change its allignment so that it shifts opposite the dicection of the turn, effectively causing the rear to track wider than the front tire.

With the links, the cradle will locked side to side so that this is eliminated. A link in the rear from the cradle to the frame below the swing arm should ha e the most effect. One at the front iso the second and the head steady third.

Another benifit of a link below the swing arm would be to keep the cradle and swing arm from twisting off vertical. Next time you have your bike up on the center stand, grab the top and.bottom of the tire and pull/push them in opposit directions and you'll see what I mean. Now some of this is the swing arm itself, but the rest is flex in the isolastics.

I'll be installing a setup on mine in a few weeks and will post some results. As far as kicking modern bike ass? Not a chance. Keeping the rear tire from feeling like it has a mind of its own? Definitely.

Chris, I think replacing the head steady first is the way to go, only because Norton did it so bad. Sure there will be flex in the cradle, but nowhere as bad as the rubber isolators on each side of the head "steady" Rubber is a lot easier to bend than steel.

Post some pictures when you start to make your links.

Jean

highdesert said:

A 40 year old, but well sorted, Commando with all this extra linkage is transformed handling wise because of a truer rear wheel corner, handle with today's Ducatis
and Hondas, etc?

If so, wow, all that more great performance just by adding these lower links?

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Surely it would be more realistic to aim for the standard of handling that a Featherbed or Seeley-framed Norton has. Could you approach this standard with a front and rear link? Or is the Commando frame not as rigid, even without the rubber mounts?

Kenny Cummings is one of the top Commando racers.

Does Kenny's Commando have this front and rear linkage installed?

Surely if this is such a great idea, his race bike would have it?

Kenny Cummings is one of the top Commando racers.

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Kenny runs a non-iso mounted Seeley frame, not a Commando.

And before that, he ran a Featherbed. I saw what Herb Becker did to get his Commandos to handle as he wanted them to. He had some steel pieces welded to the frame and they came very close to the cradle on the bottom, limiting side to side movement. Of course he had a Norvil type head steady, but for racing, he needed more sideways control than what was provided by the two stock ISOs and the Norvil head steady. Kenny Dreer had a third ISO on the bottom of the frame, but he did that to remove the head steady.

More than one way to skin a cat no :?:

Jean

caddy chris said:

Another benifit of a link below the swing arm would be to keep the cradle and swing arm from twisting off vertical. Next time you have your bike up on the center stand, grab the top and.bottom of the tire and pull/push them in opposit directions and you'll see what I mean. Now some of this is the swing arm itself, but the rest is flex in the isolastics.

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You are right to point out that if you support the cradle below the swingarm you are able to minimize the twisting forces put on the cradle and the stock iso's. In theory, the loads from that point forward are just side to side or yaw. In reality, it's limited to the extent the frame and cradle back there can carry it off. But it does make life easier for all the iso's by supplementing them. IMHO, that's where the benefit of adding links at the headsteady and below the swingarm really is. It spreads out the load four ways.

Jeandr said:

Chris, I think replacing the head steady first is the way to go, only because Norton did it so bad. Sure there will be flex in the cradle, but nowhere as bad as the rubber isolators on each side of the head "steady" Rubber is a lot easier to bend than steel.

Post some pictures when you start to make your links.

Jean

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I completely agree. I have the old britts head steady installed. Thinking I may go one step further and do two small links down low and triangulate to counteract three directions of movement and still allow up and down vibration. Instead of only two. Plus, it will leave the oil filter accessable. You'll just have to wait...

I can't post pix from my phone, but I just got a new toughbook so i'll try to learn on that.

Do pay attention when Bob Patton speaks on this as he is the real source to the fire in me to change elite bike-doom concepts of handling on is head someday. Already flipped mine inside out and I ain't coming down!

Norton had to keep removing rubber surface area to get isolation down to human comfort, add any more and the isolastic rpm threshold goes up. I'm am Commando spoiled to the N'th degree, if it don't flat disappear from pilot sensation, then it ain't comfortable-desirable to ride to me no more.

Commandos are made with two mostly rigid structures over lapping through isolastic rubber biscuits. Rear patch side loads mostly side slaps the front iso silly via the rear iso pivot. This front mount side slapping is what most onset the hinged handling right into tank slappers. Magnified by iso rubbers compressing and springing back, like a screw driver stuck through rubber washer and flicked. Plus the frame itself coils and uncoils. These all interreact in positive feedback till uncontrollable. 2ndarilly the rear patch below the rear iso is also a lever arm to twist-tip the power unit to show up as side loads on the head steady.

Total rod package to me allows frame to twist up storing energy as long and hard as you care to press it. While twisted it seems to take the tire conflict out that Chris alluded to, like rear wheel steering on hi end cars. But on load let off, by power cut, lifting out of lean or fork letting go, the frame unwraps but only in one half cycle, that is snaps back to N w/o rebound. When going in rather faster than anything you've ever seen on race video and pilot stayed on, Ms Peel uses the frame unwrap right at the instead of apex traction let go to litterally sling shot her the hardest right where everyone else and their little sister are about to lose it.

On one but me can relate to this about phase 3 handling the links allow in a ruber baby buggy, so how could you even concieve there are TWO more even faster harder on power planted ways around. Alas only racer video on that sytle show them all crashing, the poor dangerous corner cripple things.

Rump link to me is worth about 80% stability, breast 15% and head 5%. All combined for me have totally solved any and all handling conditions and upsets and sense of motorcycle under me but for the G's forces I can nearly get on no dam fat assed corner cripple modern no matter their power or traction control power cutting miss direction for really going fast into through and out of turns.

Bicker and banter all ya like, I'm done with testing linked wonders, moving on the power to kick some world class robotized elite straight line wonders.
Ms Peel don't need no stinking infaces to do it either and that includes braking
but for sure not in any turning condition pashaw.

"End of Discussion"!

grandpaul said:

"End of Discussion"!

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I wish.