If the stud to hole clearances are greater than light press fit, which they always are for motorcycle engine mounting plates and casting holes, then that interface is doing no constraining of the forces while the nuts are properly torqued, so how can you call the binding of the plate to the engine case "additional load transfer."Friction provides an additional load transfer (in addition to bolt bearing) between overlapping plates when there are many bolts or rivets, this is called a bolt group. The prerequisite is metal to metal contact over a large area. See for example old truss bridges, the Eifel tower, etc. These conditions are not fulfilled for engine plates. Sorry, but no text book will back up your theory.
- Knut
I had noticed that too , and the french manual said 63% DRY , while the 850/750 factory said 52% DRY .....The original Factory factor for a Commando was 52% dry.
The Mark 3 has a 63% dry with a 52% wet factor.
Can anyone explain that?
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Printing error in the pre-Mk3 document. As oil fills the internal cavity, the quotient (MCW-MROT)/MTR is reduced, hence the lower BF of 52% (vs. 63% dry).The original Factory factor for a Commando was 52% dry.
The Mark 3 has a 63% dry with a 52% wet factor.
Can anyone explain that?
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I wonder how critical the BF is once isos are used?The original Factory factor for a Commando was 52% dry.
The Mark 3 has a 63% dry with a 52% wet factor.
Can anyone explain that?
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Discard entries 1, 4 and 9 of this chart! They are most likely based on wrong factory information. Faults repeated and repeated, etc.Edit... Ken Canaga posted this chart on aother thread.
https://www.accessnorton.com/Norton...ank-balance-question.37898/page-3#post-641237
Mick OlField has it 52% dry, I would think he knows what he's talking about.... So confusing....
I’ve often wondered if the rear ISO rubber mount is strictly necessary. If that was a pivot on some kind of bearings instead and the front ISO was left to absorb the vibes how much difference it would really make. Fore and aft vibrations would still be absorbed by front ISO / cradle pivot and passed through the tyre as normal, and the need for lateral control with tie rods etc. would be greatly reduced.From talking to someone who built a couple of featherlastics a while ago, I learnt that the issue of the rear wheel yanking the powertrain backwards in the frame (when the rear wheel is NOT also isolated) is a real issue and not one that’s easily resolved.
In my mind, even if you did install a rose joint linkage type set up, I don’t think they’re really designed or able to control that kind of force.
IMHO you’d be better off getting the motor as well balanced as you can and isolating other parts from vibration.
MZ 250s and some of the last triumph t140s were built like this I believeI’ve often wondered if the rear ISO rubber mount is strictly necessary. If that was a pivot on some kind of bearings instead and the front ISO was left to absorb the vibes how much difference it would really make. Fore and aft vibrations would still be absorbed by front ISO / cradle pivot and passed through the tyre as normal, and the need for lateral control with tie rods etc. would be greatly reduced.
Maybe that would be the answer to the featherlastic problem?
Actually Baz, I’ve owned quite a few MZ’s over the years, and it was their system that made me wonder. If memory serves, they do have silentblock bushes in the pivot point, but nothing like the ISO bushes.MZ 250s and some of the last triumph t140s were built like this I believe
With just a pivot at the back
Suzuki bandits have a rubber mount at the front of the motor but are bolted solid at the back
Herb Becker did something to the rear ISO on Doug MacRae's racer to get it to handle better. If the rear mount was a solid block of Teflon, the cradle would be forced to rotate around it when vibrating. The only time when balance factor matter is probably when it is too low. Then it can affect performance - the evergy of vibration has to go somewhere -preferably down the chain to distort the rear tyre. Single cylinder motorcycles put more power on the ground than twin cylinder. A Manx is better than a Domiracer.I’ve often wondered if the rear ISO rubber mount is strictly necessary. If that was a pivot on some kind of bearings instead and the front ISO was left to absorb the vibes how much difference it would really make. Fore and aft vibrations would still be absorbed by front ISO / cradle pivot and passed through the tyre as normal, and the need for lateral control with tie rods etc. would be greatly reduced.
Maybe that would be the answer to the featherlastic problem?
The front lugs were probably rigid at first and broke, so rubber bushes were added?Actually Baz, I’ve owned quite a few MZ’s over the years, and it was their system that made me wonder. If memory serves, they do have silentblock bushes in the pivot point, but nothing like the ISO bushes.
Interesting about the Bandit. I wonder why?
That’s kinda like how the late Meriden Triumph AV frame works.I’ve often wondered if the rear ISO rubber mount is strictly necessary. If that was a pivot on some kind of bearings instead and the front ISO was left to absorb the vibes how much difference it would really make. Fore and aft vibrations would still be absorbed by front ISO / cradle pivot and passed through the tyre as normal, and the need for lateral control with tie rods etc. would be greatly reduced.
Maybe that would be the answer to the featherlastic problem?
Actually, only one of the data entries, the first one stating the stock Commando BF as 52% dry, is based on possibly wrong factory info. I got that one from a factory service manual. All the other entries are from other sources, not based on factory info, with many from my own measurements. It is not a recommendation, simply a compilation of other peoples recommendations, as well as measured data from various crankshafts I have used.Discard this chart! It is most likely based on wrong factory information. Faults repeated and repeated, etc.
- Knut
I'm leaning towards ISOsI suppose you ( Baz) could try the dynamic balance. As you already know, it's a lot of work but not much cost.
I suspect the odds of that working sufficiently well are pretty low.
The other option is to go to a lighter reciprocating weight.
There are now multiple options there.
Cost is generally quite high and it's also a lot of work.
If the lightweight piston size was available for your bore , it should reduce the weight of the reciprocating assembly to somewhere around Norton Atlas level, if you go with the most expensive option, long rods and short light pistons.
That's probably not going to do the trick either.
Isos will though.
That sounds like a lot of work, but at least the cost would be low and we know it works.
Glen
This engine is supposedly a 920Rough figures it seems the lightweight piston option could make a solidly mounted 850 shake like a 750 Atlas, a 750 Atlas shake like a 650ss and , maybe, a 650ss shake like a 500ss. This is just approximate based on the various weight numbers that have been listed.
A 750 that shakes like a 650 isn't bad at all.
A 650 that was as smooth as a 500 could be quite wonderful.
An 850 that shakes like an Atlas might not be ideal.
Glen