extra ISO under gearbox head steady delete

Little did I know when I bought it, but my bike has an extra ISO about 75mm forward of the centre stand pivots. I have no idea if it has rubbers in it, or just used for lateral control. I think I only discovered it’s existance when I came to install an Alton starter.
As I’d imported the bike from the UK, I had to take it to a Brit bike shop for them to give it the once over prior to official inspection.The owner was very familiar with Commando’s, and grabbed the rear wheel top and bottom and pushed / pulled. I was alarmed to see how much the engine moved, and he was surprised too I think. Anyway he looked at the top of the cylinder head and noticed there was no head steady at all. He still gave the bike the OK, but erring on the side of caution, I made my own Taylor style head steady prior to taking it for the extended inspection. (thank god they didn’t notice the extra ISO).

There are some good pictures of it in this thread. In retrospect I should have checked that ISO while it was easy to access - oh well.

cliffa

Post in thread 'Journey into the unknown..'

The weather was amazing here today, so I decided to do the work outside. The back of my neck is now glowing like an LED stoplight.

Anyway, I digress, As you good folks told me the 1/2" WW for the crank, and a 3/4" a/f (19mm) were the correct for the clutch nut ( which was already fitted with a pushrod seal nut) Hey - Ho. I have a battery impact driver (rattle gun) and that made short work of getting those off. If you don't have one already I can highly recommend them. I have now identified the belt drive as a Norvil variant. This of course is the most difficult to fit, as the front...
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It may be filthy just behind and under the box but so is under the oil tank messy too. The rubber gaiters are fitted to the 3rd lower mount and do their job. Where you showed the 3rd mount marked NEW is not correct and it is actually down further around the lower bend . I reasoned when setting out to do this in 1988 the first time, that the side loading from the rear wheel at the swingarm pivot when pitched over would be held firmer. And it does. It does make a centre stand a problem though. What real vertical work do a couple of old 06-0622 rubbers do at the head steady? Do they really assist the front mount much in vertical or the whole plot in twisting motion? It may put extra load on the cradle to case bolts but I don't see that as the top mount does very little anyway. I hit them all up with air and rarely find them slackened. The rod end top mounts I see, seem to me might be good stopping twisting but don't help out the front mount in the vertical and must surely pass along some vibes when isolation is the design? Dunno never seen one up close. I like to play what can I say. A more pressing problem for me is my yellow Commando which just did a 2,500 mile trip has a shot cam lobe. It was new 12,500 ago. This is depressing. Lot of needless work ahead. I had just fired it up with a new CV carb and Wassel ignition and it settled into a good idle, fresh oil and 80psi and decided to check the tappets. Wheel that off into the corner and finish the '75 ES I guess. Boy that ES was a piece of crap when found, left beside the shed with no plugs and lots missing, match# so trying to do the right thing.
 
mdt-son said:
Not a traditional one, but I think the rubber mounting (and the additional spring on the Mk3) does limit back/forth movements (pitch rotations). It certainly limits roll rotations. Granted, it's an imperfect system, and the reason why my crankcases and cradles have ovalized mounting holes!
The Norvil racing-type head steady is far more effective of course.

The problem with a 3rd large ISO support under the gearbox is that distance to the CoG of the powerplant is small, so torque forces becomes quite large, and there is no effective counteracting force couple in that design, so a different design is called for. Not easy to realize without obstructing the function of the other two supports.


Huh? I don't doubt the existence of your set-up in any way! I guess you altered the support under the gearbox into a nonworking support because the idea didn't work out?
By my comment "What happens to the 3 ISOs I can't imagine", I was addressing the displacement behavior in general of such a support system.

- Knut
Click to expand...
No I had no intention of fitting any rubbers into my extra ISO
And the idea did work out
I copied the Idea that Peter Cook did with his commandos back in the 90s
 
baz said:
No I had no intention of fitting any rubbers into my extra ISO
And the idea did work out
I copied the Idea that Peter Cook did with his commandos back in the 90s
Click to expand...
Herb Beckers 3rd iso used nylon strips between steel plates to allow vertical but not lateral movement. My 3rd iso is low enough to clear lower chain run which it would not if placed where the frame drawing showed. One way to take care of vertical movement is to go with a bent crank. I have a unit Triumph with 70 deg twisted Norton crank in a Commando frame and the front wheel doesn't move at all at idle unlike a 360 crank. It has modified front and a 3rd isolastic mount, modified cradle. My main Norton ride has stock mounts and I'm happy with that, 19" wheels, tis a joy to ride. Other builds ie. built from bits are likely to be modified.
 
My favorite SECOND iso-resultant stabilizer (Heim joint top one being only the FIRST) is Windy Ead's FRONT steady.

extra ISO under gearbox head steady delete


Now, in order to have a FULLY stabilized isolastic system, you must have a THIRD stabilizer. Several people have created various under-tranny units, but only one that I can recall ALSO included muffler mount brackets, the PERFECT solution. If anyone recalls that unit, and can post a photo, I'd love to see it again. No more need for rubber buffers, NO MORE LOOSE EXHAUST HARDWARE!
 
quick search gets, any other key words u can think of? name? etc
grandpaul

Post in thread 'Exhaust Isolators'

"Onder" has a good point.

Some of the members here have fabricated alternative mounting brackets that bolt up to the transmission cradle, then make thier way down and around to the muffler mounting area.

This provides a secure mounting point that moves/rocks/vibrates in sync with the engine, where the other end of the pipes are mounted. The result is that you COULD mount the mufflers solidly without the same concerns for rapid damage, but I would still use high quality McMaster-Carr isolators to fully damp out the vibration at the heavy end.
 
phippsy said:
Is this what you are after , not mine photo shoot it to remind myself when got time to do .View attachment 118027
Click to expand...
74ok said:
quick search gets, any other key words u can think of? name? etc
grandpaul

Post in thread 'Exhaust Isolators'

"Onder" has a good point.

Some of the members here have fabricated alternative mounting brackets that bolt up to the transmission cradle, then make thier way down and around to the muffler mounting area.

This provides a secure mounting point that moves/rocks/vibrates in sync with the engine, where the other end of the pipes are mounted. The result is that you COULD mount the mufflers solidly without the same concerns for rapid damage, but I would still use high quality McMaster-Carr isolators to fully damp out the vibration at the heavy end.
Click to expand...
I do something similar but more ugly. I make and fit bend flat bar from a clamp on the header to the front mount aka Triumph. Seems to help.
 
grandpaul said:
My favorite SECOND iso-resultant stabilizer (Heim joint top one being only the FIRST) is Windy Ead's FRONT steady.

View attachment 118026

Now, in order to have a FULLY stabilized isolastic system, you must have a THIRD stabilizer. Several people have created various under-tranny units, but only one that I can recall ALSO included muffler mount brackets, the PERFECT solution. If anyone recalls that unit, and can post a photo, I'd love to see it again. No more need for rubber buffers, NO MORE LOOSE EXHAUST HARDWARE!
Click to expand...
Bracketing for mufflers off a 3rd lower mount would be a good thing I imagine. As I often brace between muffler clamps anyway picking up points on a 3rd would be little trouble. This would help at the muff/ pipe joint but rear muffler mounts too, they would have to be very sturdy. This front mount arrangement looks to go a long way to solving the main problem, that being the front mount is too narrow for lateral support. Frame design and time constraints for sure. What about vibes with this design? Good thing it is easy to drop out and shim. Aligning pipes and mufflers to the rear mounts is vital and no pressure should be on the rubbers when tightening. Put a bar in the pipe and adjust if necessary or make a new mount plate, no load on these rubbers should make for a longer life. Make 2 plates and use 3.
 
mdt-son said:
.. think the rubber mounting (and the additional spring on the Mk3) does limit back/forth movements..
Click to expand...
The spring is there to relieve the front iso.
It will not restrict engine movements.

About the 4th iso:
3 points are always in one plane.
4 points in a flexible frame rarely are.
If your main goal is a vibration -free ride, then stick to 3 isos.
 
Gotta say looks to be the best way. Will have to try it. After both cotton reels failed on the left side halfway thru my recent 2500m trip, would be a nice clean way to get away from those things. Stick a Norvil head steady or other and goodbye to 06-0622.
 
ludwig said:
Maybe you are referring to my bike?

extra ISO under gearbox head steady delete
Click to expand...
Ludwig
Do you have a functional centre-stand with those brackets?
I do like your idea but wouldn't be prepared to do without a centre-stand.
Also - it looks like you need custom mufflers with forward mounts - correct?
Cheers
 
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