STop me before crank destruction!

I'm tired of reading about shooting in the dark on red line limiting so ask if there is any sense how much flywheel deflection is start of too much. Would it make sense to run an insulated probe in with a wire up to crank rim then back off say .001" and have it short out ignition or light up on contract to know what rpm to nearly does it in ahead of time?

00.1 [inch] thats not much! if a norton crank only flexed a thou there would have been no superblends required ,try 20 thou plus!

The other day Rohan was being very smart and snide and told me that the superblends fixed the bearing problem because they have a higher load rating. I always thought it was more about their ability to self-align when the crank flexed ?

acotrel said:

The other day Rohan was being very smart and snide and told me that the superblends fixed the bearing problem because they have a higher load rating. I always thought it was more about their ability to self-align when the crank flexed ?

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I am afraid Rohan was right. Superblend bearings have straight rollers -not barrel shaped as the long standing myth has been. They get there advantage through very high load capability. Jim

I am afraid Rohan was right. Superblend bearings have straight rollers -not barrel shaped as the long standing myth has been. They get there advantage through very high load capability. Jim

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wow Jim

right from their introduction the strong consensus on every thread I have read is that the Superblends were put in because they better handled the crankshaft's whipping by having the roller ends slightly beveled, if that is the correct term, and that in effect that lessened the tendency of the crank to "dig into" the bearings?

My understanding is that Norton fitted the Superblends to solve that problem which was giving the factory large numbers of warranty claims in as little as only 5000 miles brought on by the comparative ease of the higher revving 19 tooth sprocket fitted to the Combats.

But now you are saying the Superblends were fitted because they have a higher load bearing and do not have any difference versus the previous bearings otherwise?

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edit: sorry hobot for having no answer to your question and instead asking Jim a question!

hobot, can you give us a more detailed explanation of your concern?

My understanding from reading your posts is that your bike has been off the road for a while now and it is undergoing some kind of extensive rebuild and that you are building it to be very high revving for more power and so are concerned about your crankshaft and bearings being able to handle the flex at your new motor's upper limits? Is that right?

Can I ask why you don't simply build a strong but "safe" motor that is not likely to bring on these concerns of possible future damage? thanks

1up3down said:

I am afraid Rohan was right. Superblend bearings have straight rollers -not barrel shaped as the long standing myth has been. They get there advantage through very high load capability. Jim

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wow Jim

right from their introduction the strong consensus on every thread I have read is that the Superblends were put in because they better handled the crankshaft's whipping by having the roller ends slightly beveled, if that is the correct term, and that in effect that lessened the tendency of the crank to "dig into" the bearings?

My understanding is that Norton fitted the Superblends to solve that problem which was giving the factory large numbers of warranty claims in as little as only 5000 miles brought on by the comparative ease of the higher revving 19 tooth sprocket fitted to the Combats.

But now you are saying the Superblends were fitted because they have a higher load bearing and do not have any difference versus the previous bearings otherwise?

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The ends of the rollers do have a radius on them -as do all roller bearings -but for 80% of the rollers length they are as straight as I can measure using an electronic guage that is accurate to .00001 inch. Jim

The term superblend referred to the way the straight section of the bearing was blended into the radius at the ends of the roller.

Early roller bearings were not smooth as the straight section entered the radius section which would cause a high load point if there was slight miss-alignment and lead to failure. It was simply as good as could be done with the machinery of the day.

Superblend referred to improved manufacturing that made a smooth match of the radius to the straight section that is common on all roller bearings today.

So I wouldn't call the hyped Superblend advantage all wrong as it does help the bearing to live through slight missalignment for short periods without immediate damage.

But it certainly has little in common with a self-algining bearing with barrel shaped rollers. Jim

hobot said:

I'm tired of reading about shooting in the dark on red line limiting so ask if there is any sense how much flywheel deflection is start of too much. Would it make sense to run an insulated probe in with a wire up to crank rim then back off say .001" and have it short out ignition or light up on contract to know what rpm to nearly does it in ahead of time?

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What about metal fatigue?? If you are planning to subject the crank assembly to higher loads than those of a standard engine then it may be fine at "X" amount of distortion for "Y" amount of time but then fail after that at less than your max distortion.
I think you may have huge problem trying to find a safe limit that at the same time lets you take the engine to its max rpm.

Holy crap, Jim, what an explanation. I really appreciate that. I never really thought about what "superblend" meant. I just kind of thought it was a commercial term for a metallurgy blend. Shows what a dumb ol' farmer like me knows! This was one of those "light bulb" moments! :shock:

SquareHead said:

Holy crap, Jim, what an explanation. I really appreciate that. I never really thought about what "superblend" meant. I just kind of thought it was a commercial term for a metallurgy blend. Shows what a dumb ol' farmer like me knows! This was one of those "light bulb" moments! :shock:

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I wanted to know once too -about 1980. I wrote letters [real snail mail] to FAG and Timken. That is the basics of what they told me. Jim

Its common knowledge among the ancient NOC-UK members the superdupers were just better blended and build better though prior racers got away with 11 HD ball bearings replaced more often in thin cases to take some extra flex.

Peel's engine spent last 7 yrs with Ken Canaga waiting for new hi end items to be offered and me catching up on major injuries or homestead or car recoveries. Essentially everything has been cryo tempered and crank welded up then nitrided. Valve train tested well beyond 10 grand. Peel is geared to lug engine down on shifts so hi boost can build fast. I'm more interested in harsh acceleration than top end so hope to get some sense when crank flex might become significant and a way to detect that before exceeding it. Peel's going torque route more than rpm path to power but still got to know when to shift up of give up my lead to survive.

My impression is there's some threshold of flex that can suddenly go way past tolerance of crank or the rod shells or bearing wedgies. My eyes could hardly change focus fast enough to see chicane aim points clearly to just miss outside edge paint line so can't look at clocks accelerating into turns so seek some rev limiter to alert me to shift up and ease throttle to keep tire in best slippage traction to slow up in time for another sharper direction change.

I'm afraid it may be too late if .020 flex hits but how much less who the hell knows right now.

0.001" would be too optimistic. You'd flex a crank more than that with finger pressure.
On high revving Triumphs,they allow 0.060" clearance between flywheel and cam lobes. You'll get away with 0.045" for a street bike.
Cranks don't break from a single one-time gross overload, although that can start the fatigue cracks. If the fatigue cracks are detectable after one hour of use, it could take 10 hours of similar use for the crank to break.
If fatigue cracks are detectable but the crank never again experiences the same amount of stress that caused them, it could take 1000 hours before the crank breaks.

Thanks xfile that gives me some ranges to think about. I guess I could see what rpm .001" contacts, then .002" and up till maybe .030" and see what rpm that occurs in Peel hopeful resistant construction. I have refrained from reporting what online calculators imply for Peel at 8grand and I have refrained from even plugging in 9000 -

So next question where would one drill-tap a probe to flywheel. & How would ya make the conducting probe install?

I had hours on a outlaw 400+cc 2smoke that didn't move till on race chamber pipe before race type clutch engaged, did some rock&roll rear dancing on extra wide axle nearly 60 skewing-roostering on THE Gravel and mowed paths in my tall pasture grass till got tossed off and bruised leg in gap in armor but did get it out my system while learning why quads don't win Baja type races while motorcycles do. Quads are kids toys compared to flat trackers but easier to slide more slowly.

hobot said:

Thanks xfile that gives me some ranges to think about. I guess I could see what rpm .001" contacts, then .002" and up till maybe .030" and see what rpm that occurs in Peel hopeful resistant construction. I have refrained from reporting what online calculators imply for Peel at 8grand and I have refrained from even plugging in 9000 -

So next question where would one drill-tap a probe to flywheel. & How would ya make the conducting probe install?

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If you really wanted to see the flex you could use a proximity sensor and a machined ring around the center of the crank. The output from a prox sensor would tell how far away the crank was very accurately. You could watch the output on a scope or log it for slow motion playback. Jim

Ugh Jim that's you're league of capability, to follow up in spare time but Peel engine is buttoned up and proximity sensor is too complex and time delaying for Peel. The Triumph clearances were rather informative and scary to me. Do you have sense of acceptable deflection in a crank like Peel's? Friction and impeller cavitation and stock size valves may be self limiting by torque loss after normal hi rpm to worry about it. Still its seems deepest darkest mystery left to objectify.

You could work it out, the un-balanced mass x rpm will give the upward/downward Energy , then place the crank in V blocks and apply the same force .use a DTI to measure the Bend , I would guess the crank will bend a few thou with very little effort,where the webs meet the bearing jurnals .
Doubling the RPM x4 the force...think about the crank un-balance , it shakes the entire package..the machine and you!

Norton later Dommy and Commando cranks often break at the drive side big ends outer radius because the 'skilled men' who produced the cranks shoved a drill up the inside of the drive side half to clean it out and left the sharp corner of the drill finishing directly beneath the outer radius. I.E. you get the crank grinder to incorporate a nice STRESS REDUCING 90 thou radius at the point of MAXIMUM stress and the idiots left a perfect example of a stress raiser inside the crank at the point of MAXIMUM stress!! Many years ago when NVT were thinking of having new crank halves manufactured they had some test machined by Laystalll Engineering (Wolverhampton)......I heard about it whilst trying to determine who had made the 68mm stroke one piece 1 3/4 big end crank a friend had found and bought which was one of two Laystall Engineering had manufactured for the Gus Kuhns' short stroke 500 motor (68 x 68).....and as Mr Negus was showing me the first off new crankcases at Shenstone at the time I naturally asked if the new cranks were also going to incorporate the stress raiser......after enquiring how the hell I knew about the crank machining Mr Negus later examined the drawings and had them changed. However the machining costs were so high no crank halves were actually produced for sale to the public.( As I looked at the new crankcases I also asked Mr Negus where is the camshaft oil bath Mr Hopwood had so carefully designed into his original Dominator crankcases so the cam was correctly lubricated at all times and would not fail prematurely....or as Mr Hopwood wrote to me and I quote 'The camshaft tunnel of the Dominator engine was designed to retain as much oil as possible and the lip was designed to run within 1/8 -3/32 of the flywheel rim to pick up oil from it'. Later the idiots at Norton and later NVT designed it out with every new crankcase pattern made........its not had to put it back in!!

The ORIGINAL and in my opinion ONLY real superblend bearings produced were special bearings produced by RHP in the UK at the old Ransome and Marles factory in Newark. They have not ben produced for decades. They had smaller diameter and width rollers which were very slightly barrel shaped so that as the crank flexed the edges of the rollers did not dig into the inner and outer raceways causing premature bearing failure. The old Atlas and early Commando (Atlas Mk3) roller mains were stamped 8MRJA30 and the new 'superblend' ones were stamped, on the outer raceway, MRJA30 with a 6 eched in front giving 6MRJA30. Both types had a brass cage. The static and dynamic load ratings for the 'superblend' 6MRJA30 bearing were LOWER than that for the older 8MRJA30 version. Of course these bearing designations were shown in Mr Nicholsons book written many yearsago .... Modern Motorcycle Mechanics.

The above information and much more such as how the Commando clutch works and why Norton employed at least 4 different diaphragm springs in them etc etc etc can be found on some bumph I put together and then lost interest in till many years later a friend had me update and shove them on the web. They can be found, assuming the site is up and running, on http://nortoncommandoclutch.zxq.net/netindex.htm.

This link will work. Thanks beltdriveman.
http://nortoncommandoclutch.zxq.net
Bill G

John a bit late for me to do static strain measures but sure hope someone attempts it while we still care.
Blew me away beltwhipman on the history lesion from bearings to cam bath and crank clearance. 1/8" = .125". Now how to detect even half of that to get a sense of how risky to get to stay away from flexing cam taking its clearance away too. I'll get Peel going first and see if I can tolerate approaching crank worry rpm but definitely want to know what's going on in Peel. I can't get over other worldly reactions of me and strangers on an overgrown lawmower like Commando power so want more of it in spades. Its taken the worldwide village to get Peels features developed so don't really think of her as all mine anymore.

Steve,theres not a lot of men could work out the dynamic in-balance or un-balance ? that a crank generates at 7000 rpm. but we are aware that the forces cause "a lot of flex! History teach's us..Norton race shop busy rebuilding blow ups...Design office out for tea..but we have been there before.