DIY Headsteady

I've just about got it all ready to go.... the bike has been converted to 'vernier' at some point, I have tried the feeler guage method at 10 thou but it seemed a bit variable... a search

suggested that one turn was 50 thou and 1/2 a turn at 25 thou was recommended........

I did this and you can grab the rear wheel and it appears to move a few mm/" ....you can see the primary case move slightly.....is this normal? how should I set it all up?

I've got a rally on in a fortnight ...the pressure is on... :roll:

Thanks for you all your input guys, much appreciated.

What shape are the iso rubbers in?

Have you checked the integrity of your swingarm spindle mounting tube in teh tranny cradle? They can get wallowed out and need at least a bolt-on clamp fix...

Perhaps there might be a better way to rubber mount the motor in a standard commando frame ? If we threw away the isolastics and simply rigidly fixed the swing arm pivot to the frame, and simply used silent bloc bushes to mount the motor/gearbox assembly. It would still transmit vibration, but nowhere near as much as a rigidly mounted motor. What we found with two strokes is that you lose power when the motor is rubber mounted, but with the torquey commando engine that shouldn't be a problem. The Isolastics were obviously intended to make the commando suitable for comfortable riding in UK traffic - a compromise bike. If we are prepared to specify it's end use differently, we can change the design t o suit. I would have thought that 80 mph freeway riding would require a different approach to balance factor and means of mounting the motor, to what is required in 30mph UK traffic ?

grandpaul said:

What shape are the iso rubbers in?

Have you checked the integrity of your swingarm spindle mounting tube in teh tranny cradle? They can get wallowed out and need at least a bolt-on clamp fix...

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They look alright and I don't think the bike has had much use in the last few years, a PO had modified the swingarm spindle to have three fixings on the cradle. I lubed it up and it nice.

Taking the isolastics out looks like a mission..... cheers.

acotrel said:

It depends on whether you are using isolastics or rigidly mounted motor. I cannot come t o grips with using the head steady as part of the way to stop the swinging arm from moving irrationally. Personally, I think that if I had a standard commando, I would replace the isolastics with solid mounts for racing. The design is pretty crappy. On the Seeley, I have a curved chrome-moly front tube which is intended to spring, so the frame doesn't crack. You will note that ends the two head steadies can vibrate upwards with the motor. The head steadies are not intended to cope with any sideways rocking couple on my bike.

For OZziE :

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I bet your headsteadys are more there to take up any vertical engine expansion that vibration.

Commandos were designed to be comfortable and fast. The fact that they make ok racebikes leads us to believe they aren't as horrible as you make out.

When you give the bike a lot of stick, the motor tends to move back as you accelerate, and forwards as you use engine braking by changing down approaching corners the head steady stops the engine plates frpm fatiguing and cracking. If you don't have the head steady, everything gets a dose of the vibes and unnecessary loads, and lots of things shake loose and fatigue. Peter Williams was obviously a good engineer, but in some things he lost the plot. The attempt to make a frame with the swing arm supported at the engine plates instead of at its extremities, was just bloody silly when you think of the loads involved. It just has to flex the engine plates regardless of any sideways shimming. Featherbed frame tubes crack at the tops of the plates which support the swing arm spindle - what does that tell you ? I think that if I was using a standard commando frame, I'd weld or bolt two small plates to the frame each side of the swing arm and through bolt it with small silentboc bushes at each end to stop the twist. You could even do the same thing by remanufacturing the footrest plates, to pick up the ends of the pivot spindle with two rubber filled bushes. Somebody should fit a load cell to the end of the spindle in a standard commando and measure the flex when it is ridden hard.

72Combat said:

I've just about got it all ready to go.... the bike has been converted to 'vernier' at some point, I have tried the feeler guage method at 10 thou but it seemed a bit variable... a search

suggested that one turn was 50 thou and 1/2 a turn at 25 thou was recommended........

I did this and you can grab the rear wheel and it appears to move a few mm/" ....you can see the primary case move slightly.....is this normal? how should I set it all up?

I've got a rally on in a fortnight ...the pressure is on... :roll:

Thanks for you all your input guys, much appreciated.

Click to expand...

If you can see the primary case moving, the front iso may have too much clearance. This forum taught me that you have to use a lever to push the engine away from the adjuster to get an accurate clearance with your feeler gauge, otherwise you can get a false reading and end up with the iso too loose. When you tighten the engine mounting bolt after turning the adjuster, check the clearance again. You may find that it has tightened up because of the slack in the threads of the mounting bolt. If this happens, you will have to back off the adjuster, nip it up again, then re-check, and repeat till you achieve 8-10 thou between the plastic shim and the adjuster when the engine mounting bolt is tight and with the bike off the stand. You may not get an even 'feel' from the feeler gauge - this is quite normal.

Hope you make the rally. When the pressure is off, it would be a good idea to inspect your isos!

acotrel said:

It depends on whether you are using isolastics or rigidly mounted motor. I cannot come t o grips with using the head steady as part of the way to stop the swinging arm from moving irrationally. Personally, I think that if I had a standard commando, I would replace the isolastics with solid mounts for racing. The design is pretty crappy. On the Seeley, I have a curved chrome-moly front tube which is intended to spring, so the frame doesn't crack. You will note that ends the two head steadies can vibrate upwards with the motor. The head steadies are not intended to cope with any sideways rocking couple on my bike.

For OZziE :

Click to expand...

That is nice Thanks! The money shot for me would have to be the timing side though.

Trace marks at front iso is mostly vertical slightly leaned rearwards, motion at top is mostly horizontal slight tipped up at rear, rear iso is mostly front/back d/t thrust & road load motion but hardly nothing from engine other than slight rotational motion that don't leave marks.

Seems the 750 Commando's were as good or better in handling than other makes of the era so a great success but are dangerous to play with sports bikes with or w/o a head steady. My quandary and guest is to find out Peels pecking order in all conditions as I feel something really different with her hi load handling compared to sports bikes or un-tamed Commando. Could the isolating mounting system be improved on, shoot I don't know. Could the isolastic power unit and over lapping frame be re-created in modern translation, I sure hope so, but how? In 2003 head link was found not to transmit vibration so numerous designs popped up since.

What's different in 'tamed' isolatics vs Seeleys or other rigid chassis? I think it has something to do with allowing the front and rear tire to tip or aim slightly differently following road texture or pilot inputs w/o one end bothering the other, until it gets to building up rebound bouncing, but Peel's links completely nullify-resist to point I've not been able to induce any thing upsetting. That can make ya crazy, finding every other cycle's dangerous behavior to avoid, but not able to on Peel going way harsher. Crazy because you lose rational fear of any turn but to run into a hidden object so fast brakes only affect the impact angle.

I think i've sensed the two down tubes iso tabs twisting like torsion bars so tying them together seems to help that source of rebound. Rear of frame bend and back of cradle plates benefit by tying together too, as do fork tubes. That leaves the Commando's soft center I so love in you know who-what.

Summary ?: elites are seeking some compliance for tire conflicts and side loads, so does this too rigidness apply to the vintage Seeleys too and is Becker swash plates so effective it mimics rigid Seeley's? Not a bad thing mind you but is there even better to seek like the elites are scratching at straws on?

Finally got it finished.


I was contemplating a new wiring loom but its nearly summer here so a quick tart up....
The Boyer was suspended with a clip so I made up a bracket lined with rubber and stuck it between the coils.
One thing just leads into another....
Just about ready for the annual Vintage Bike Rally in a week......this weekend off racing the Beemer....

acotrel said:

Peter Williams was obviously a good engineer, but in some things he lost the plot. The attempt to make a frame with the swing arm supported at the engine plates instead of at its extremities, was just bloody silly when you think of the loads involved. .

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Wrong. The geometry of the frame was by Dr. Stefan Bauer and the Isolastic design was by Bernard Hooper and John Favill in 1967 before Peter Williams joined. By the way, Peter's first design job at Norton was the twin muffler hanger on the 750 S.

Hooper's reasoning for attaching the swingarm to the gearbox cradle was correct - it was proven that it was feasible for the drive chain to jump the teeth of the output sprocket if the motor / transmission was in a seperate planes of movement to the rear sprocket. Whilst this condition was seen as low risk in low to medium speeds, it was considered too risky at higher speeds.

Whilst the Iso system is a compromise, it does respond to careful attention to set up and maintenance. If you need to be convinced just have a look at the 1968 Isle of Man Production TT. There are several very fast 750's taking a multitude of bends for many many miles. A competenant rider today can enjoy sprited fast handling with confidence and without the vibes. That does not diminish in any way that the Seeley is the best race chassis - just don't disregard the Commando chassis.

Mick

72Combat said:

Finally got it finished.

I was contemplating a new wiring loom but its nearly summer here so a quick tart up....
The Boyer was suspended with a clip so I made up a bracket lined with rubber and stuck it between the coils.
One thing just leads into another....
Just about ready for the annual Vintage Bike Rally in a week......this weekend off racing the Beemer....

Click to expand...

Looks good, well done. Let us know how it handles.

ML said:

Whilst the Iso system is a compromise, it does respond to careful attention to set up and maintenance. If you need to be convinced just have a look at the 1968 Isle of Man Production TT. There are several very fast 750's taking a multitude of bends for many many miles. A competenant rider today can enjoy sprited fast handling with confidence and without the vibes. That does not diminish in any way that the Seeley is the best race chassis - just don't disregard the Commando chassis.

Mick

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Well said.

I never believed in the commando, but having read what is on this forum, and in a magazine that I found while I was away this weekend, I'm thinking of looking for a basket case 850. I can live with a certain level of vibes if they are only low down in the rev range, and I believe that I can re-engineer a commando to be really spectacular.

In case ya ain't noticed my remarks I have found the tri-linked half compliant linked isolastic Commando to run circles around elite riders while not even feeling the bike under me but for the hand of God G forces of acceleration forward and though turns so easy and secure breaking traction in tight dangerous public places ain't exciting enough to get Adrenalin Trembles, so have to fling 'er off road to get the zings of loss of control and recovery challenges. Alan I tell ya you would appreciate a Ms Peel setup like few others and don't yet know what I'm talking about or what rest of the world is missing out on. My suggestion is a robust rear swash plate or 1/2" rump rod plus slightly compliant breast and head links. Once you've had road orgasms with likes of Peel, you'll never be happy with too rigid or flexy dangerous corner cripples - so sight of balloon tires and steering damper on 'computer controlled contestants will be a depressing sight as no contest to challenge ya on a air cooled flying carpet with ballistic steering jets >>> up to the ton on non blown engines and rather above that with boost. Ya can't imagine how harsh corner attacking it takes to make the elite's seem so backwards in construction philosophy and riding style needed to control them. pashaw. It ain't me its the genius of isolastic Commando I'm pointing too, once tamed but not stifled.

acotrel said:

I never believed in the commando, but having read what is on this forum, and in a magazine that I found while I was away this weekend, I'm thinking of looking for a basket case 850. I can live with a certain level of vibes if they are only low down in the rev range, and I believe that I can re-engineer a commando to be really spectacular.

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Go for it, Aco. Dip into the archives here and you'll find most of what you need to know and where to get it, and the people to consult. Hobot's tri-link is worth looking at; if I got another Commando I would try it. He will fill you in on the details. Add re-worked Roadholder forks, some decent shocks, a good front disc brake and a pair of new Avons, and you're nearly there. Leave the engine standard but blueprinted for good road manners and reliability and you will have a bike that will make you smile every time you ride it.

if all I'd ever tasted was a fully fettered un-tamed isolastic Commando I would of never been heard from again as even cheap girls beginner bikes can leave the best ridden isolastic Cdo in the dust or more likely the weeds in a ditch. If you follow what others have done all you'll end up with is over rigid ho hum corner handler that can kill ya just seeking a bit more fun over their hidden thresholds that take out the best racers as ever was, no fault of their own skill. Study Watt's linkages for deeper insights and don't put the links close to the isolastics nor same horizontal plane at the isolastics. Head steady then becomes merely a wind gust isolator as nothing else for it to do. Also hobot Roadholders have never let me down nor get any notice going cross wise over lumpy road surface leaned way over on power. Uncannty Flabergastingly Fabulous~!

The reactions one gets from the super duper hot rods is absolutely priceless! The might be able to put down like 25-30 hp in the chicances but Peel could put down like 50 so not even a contest till over 100 mph in opens where they'd better be able to float front or just no time to catch up before more distance accelerated in next leaning turn. I don't feel a thing but the fun flinging.
watt-like-triple-helm-linkage-peel-t6637.html

Well been a couple of weeks with the new headsteady. Took the Combat on a 300 km Vintage rally and have used it every day for the last week commuting in prep for next weekend away.
I can't say I really notice any real improvement as I don't really push the bike very hard. The ride is smooth in fact as smooth as my BMW once over 3000 rpm.
I need to get around to fitting my Landowne kit and sleeving down the pathetic front disc m/c before I explore the other side of 70 MPH.