Taffy said:
I'm not :wink:
I'm probably one of the people who is most aware of it as it seems I have been the only one to be able to post the data :roll:
And the .65mm is really the max figure..
Taffy said:
i also totally disagree with holding the crank hard left or right as the rollers will graunch hard against this lip everyone is on about. you want to hold the crank still: what have i advocated? angular contact ball race bearings!
I was not talking about holding it hard left, it is simply a spacer of the correct dimension to hold it in place. That does not mean there is a preload on the bearing.
I'm also not the only one. There are plenty of engine builders who use this, whether right or wrong. One of them I believe is JBS of the 750.
Taffy said:
the next one si, is that on the ball race dale doesn't recommend a C4 (the loosest fit) nor the C2 which is almost an interference fit but the C3 which one could describe as "taking up the slack under the normal thermal expansion found in yer average motor!". this i suspect cuts out the question i had put up previously and you do now: is the inner race crushing the balls and therefore squeezing the oil out?
You haven't understood my statement taffy.
It is possible to use a C4 even if Dale recommends a C3. Personally, I would also select a C3 bearing. C4 is not the largest internal clearance, or loosest as you put it, a C5 is.
I have taken C4 bearings out of these engines that came from the factory even.
In my previous statement I am talking about the interference fit on the crank shaft of the inner bearing race. If the fit is too tight it can change the shape of that inner race and cause problems from there. Including unnecessary vibration, increase stress on the rollers and so forth, including reducing the internal clearance from spec.
A sign of such an impending problem can be a slightly interference fit when installing the crank.
There are also plenty of engine builders out there who will machine the bearings or internal engine components the make sure the tolerances are good.
Taffy said:
i will now add a question as you are on about the crank: my ducati had excellent primary balance coz it was a V-twin and each cylinder was only a baby 250cc. yet the bearings were 72mm od and 80mm od. as well as that, the crank journalks were 35mm and not the 62mm and 30mm of the 650 so come on folks.....they have upped and upped the CC over the years, they have shortened the stroke and made every one of the three engines well over square. i think the crank is part of the problem.
Well, you are confusing two separate things here. However, the two bikes have totally different design parameters and Husaberg will have designed the mains to be the minimum size required for racing.
I go completely with Enginehardware's comment to that effect. In these engines they are not designed to last a lifetime. The Duc. will have had a much longer lifetime in the design parameters.
However, what I want to know is that I can have mains that last a specific number of hours and know that they will last that time. The problem lies here - in many cases they don't last even the short time required.
Taffy said:
i think it was Drc who said that the big end was the wrong diameter versus it's width but i suggest that as long as you don't make the big end wider but make it fatter you have helped stiffen the crank surely?!?! you gain more contact area ayt the press fit and surely dan's scenario is not going to happen? so why the move to 35mm big end when - and correct me if i'm wrong? - the 650 big end was having no trouble?
In supermoto, as soon as you increased the compression, big end problems did arise. They increased the 650 compression in several stages, the first of which was in 2003.
It is worth keeping in mind that the force onto the big end pin is distributed almost across its entire width, it's not like it's a 2 foot cantilever. The force acting upon it at peak acceleration is therefore more a shearing force than a bending force, but I suppose that resultant forces may cause a bending force.
If you are considering loads on the crank, you also have to consider conrod length as this will also have an affect on peak acceleration and therefore crankshaft load.
Because it's a larger diameter the big end will also add stiffness and it will also change the resonant frequency of the whole crankshaft assembly.
The other thing that should be mentioned is that it is generally thought that peak force on the crank is at tdc on the exhaust stroke, not from combustion pressure.
Taffy said:
it's interesting that dale doesn't 'give up' on the roller bottom end, he maintains that if the housings are correct, if the alignment is right then rollers aren't a problem!
And that should be a clue on the crank and he added mass quite happily to the things.
But in every occasion he removed the counterbalancer, particularly in his racing engines.
This should be an even bigger clue.
Let me explain a little more about my harmonic theory.
I think that the crank shaft may be flexing naturally but under most conditions it is not enough to cause any problems. in most things we expect some flexion anyway. But by and large the crank on its own is stiff enough.
Add to the crank a significant weight spinning away contrary to the crank shaft which, while the engine is running adds noise and vibration to the whole assembly. On many occasions this works absolutely fine. Then on top of that you have vibrations added by the running gear etc. through the primary gear and so on.
However, there are certain times where the vibrations end up matching the resonant frequency of, lets for arguments sake say the crank shaft and suddenly the vibrations amplify causing that dangerous significant movement in the crankshaft assembly.
It is a bit like those first generation suspension bridges that under normal circumstances happily took the load of the traffic but when the wind blew in a certain way, the bridge shook itself to bits -
without any load on it
This doesn't mean I think that the crank is woefully bending but I think it end up vibrating in such a way as to cause damage.
It can be a very distructive force, like adding all the amplifiers in a nighclub to the output of your ipod headphones.
So to quote your words of wisdom "i think the crank is part of the problem"
But I don't think it
is the problem per se. If you know what I mean.:wink:
This is also why I don't think it is quite a simple as the factor making the big end fatter.
If it were just crank flexion, I think they'd have solved it ages ago, becuase it would be simple and cheap. KTM and Husaberg are pretty good mechanics.....
All the best,
Simon
