isolastic replacement suggestions for a 72 interstate

[Fast Eddie]

I have a hard time believing that the stock head steady rubbers (same part number as the exhaust mount rubbers) can effectively take any real weight of the engine unit. And if they did, it wouldn’t be for very long!

 

[grandpaul]

I give up.

 

[EstuaryBoy]

'but the spring (and top isolastic coushions) are indeed suspending the engine.'

'Did NOBODY read my previous reply regarding the fact that the spring is NOT holding the weight of the engine?'

Again, here to learn, but maybe I've taken one of the above quotes out of context??? Do not the rear shock absorbers also play a big part in this equation, assuming the mass is rotating around the rear iso?

 

[10drum]

I give up.

Everyone is falling into the trap I always fall into. I over think everything. With that being said GP. Are you the "grandpaulZ", on the triumphrat forum?

I think I'm going with the racingnorton kit on eBay. I may end up replacing that with the cNw kit next year, but price does have some influence on me.

thanks again for all the replies.

Phil

 

[EstuaryBoy]

Everyone is falling into the trap I always fall into. I over think everything. With that being said GP. Are you the "grandpaulZ", on the triumphrat forum?

I think I'm going with the racingnorton kit on eBay. I may end up replacing that with the cNw kit next year, but price does have some influence on me.

thanks again for all the replies.

Phil

Yes, we mustn't overlook it was just a: 'bodge up'... a temporary measure by the engineers until a better engine could be developed.
It is/was very a successful bodge up though, given it's relatively primitive solution, but never intended as the nirvana that: 'Someday all motorcycles will be built this way'
Keeps the grey stuff ticking over, though

 

[SteveC]

The good news is that it still works regardless of our individual opinions.
I would still love to have more insight into how and why some of these things were developed!

 

[Craig]

I can attest to improvement with a DT type headsteady with the spring tensioned in place ... as I mentioned earlier I really don’t understand exactly how it works , but it does ! I don’t understand how some prescription drugs work exactly but they do the job when needed ....

 

[Fast Eddie]

I give up.

My comment on the ‘exhaust’ rubbers in the head steady was in response to your comment that ‘the spring (and top isolastic coushions) are indeed suspending the engine’.

Personally, I am still having a ‘hard time believing’ that those rubbers can take any real engine weight for any real length of time. And I don’t see how they can suspend something without taking any weight....

 

[grandpaul]

...With that being said GP. Are you the "grandpaulZ", on the triumphrat forum?

Guilty as charged.

Somebody stole my username on TRat.Net and started posting cr@p. The moderators banned him, then made me a moderator, but I had to add the "Z".

 

[grandpaul]

I can attest to improvement with a DT type headsteady with the spring tensioned in place ...

I happily joined that crowd just after joining this forum in 2008. I saw one for sale at close to half price and snapped it up.

 

[Fast Eddie]

The cNw head steady seems to come with the drilling/tapping for this (see photos below) - that is, to mount item #2.
Item #8 appears to pick up on the front tank bolts?
Anyone done this? Views?
View attachment 21211View attachment 21212

Rob, you’ve got a well built, well balanced engine with top drawer isolastics and the best rose joint head steady.

It would be wonderful if you did decide to try the spring and give us all the benefit of your before / after comparisons.

 

[grandpaul]

The chances that a particular setup of rear suspension, isolastic rubber hardness, and tire/wheel weight might result in a perfectly balanced combo that didn't need the spring to compensate, are slim to none.

Hence, the few dollars to add those bits would almost certainly NOT be a waste.

I'm more than a bit surprised that nobody has chimed in to back me up on this subject...

 

[Fast Eddie]

What I’m struggling with is this, the improvement is what... reduced vibration?

I thought Commandos were smooth?

I‘m not being facetious here, just wanting to know what the actual improvement is.

If it is reduced vibes... then I know I won’t benefit from one.

 

[EstuaryBoy]

According to Mick Duckworth's book it was introduced because of the 'extra weight' of the Mk3 engine...
So would 'earlier' benefit?
You pays yer money.....

 

[Fast Eddie]

My Commando had a horrible vibration, particularly when decelerating down through 3,000rpm. I am convinced the bottom and had never been disturbed, and thus that’s how it left the factory.

Maybe the spring was cheaper than properly balancing the cranks...?

 

[grandpaul]

What I’m struggling with is this, the improvement is what... reduced vibration?

I thought Commandos were smooth?

I‘m not being facetious here, just wanting to know what the actual improvement is.

If it is reduced vibes... then I know I won’t benefit from one.

Yes, reduced vibration.

...but also, longer life of the front and top isolastic rubber bits.

 

[Fast Eddie]

Yes, reduced vibration.

...but also, longer life of the front and top isolastic rubber bits.

That’s fair enough, and will appeal to some sensible folk I’m sure.

But personally, I’m just thinking ‘how smooth do folk want their Nortons to be’? I don’t want or need my Commando to be any smoother than it is now. And I’m pretty sure the isos in mine will outlast me. So I’m out !

 

[Time Warp]

Don't forget the secondary (inner) rubbers in the isolastic tubes.
I do not think the stock box heady steady is that bad (if it was more rigid) but the rubber cushions it uses have some limitations and the hanger spring might very well been to support those cushions.

Those cushions are certainly not there to take any weight, they are only a (intended) control for axial and radial forces within their working range (hence the slot adjustment, maybe with the wheels on the ground, maybe even with the rider aboard ? )

I will stick with my thoughts on where Dr B got the basic idea.



I believe ? RGM has been making replacement isolastic kits for longer than even AN.
If they were 'no good the word would have been out by now.

There was talk some years ago of kits with harder rubber and maybe more vibration than stock, the maker ?

 

[batrider]

Mk3 springs with CNW head steady.

 

[robs ss]

Mk3 springs with CNW head steady.View attachment 21247

A couple of questions:
That doesn't appear to be the standard bracket (that has the vertical stud the the trunnion is adjusted on) - what is it?
There looks to be an electrical connection to that bracket - why
Cheers
Rob