RPM, flex, bearings, BF, cases galore

Here's bickering subject to beat the winter time oil and storage season themes.
I'm sticking with factory on my factory limited Combat but I'm non committal on weird Peel with variable BF and way to witness crank flex before destructive rpm. I think BF has more to do with just bike frame and pilot protection, mid 50's if BSA and Triumph and rubbery Nortons and way over that for clunker solid mount commuters and elite solid mount fancy framed racers. This is actually an extension of my 13 yr asking everyone what limits rpm in Commando engines. Many things, but which most often, then next and so on ...

So here's the teaser from Ben English a long mentor of mine to start the flames

BSA & Triumph use ball bearings, so why rollers on Nortons?
Knut Sonsteby opined about Frank Holden's ball timing side main bearing "..... angular realignment of a ball bearing is comparatively small ....."


I find it pretty hard to believe that the "comparatively small" alignment tolerance of a ball bearing is not sufficient for a Commando timing side. The question it seems to me is whether eliminating the problem of shimming for end float is worth the lesser capacity of the ball bearing.

The undiscussed question is - do Norton crankshafts really flex more than BSA and Triumph twin cranks, and if so why? BSA & Triumph get away with balls and plain rollers just fine, don't they? Is it just that Nortons get to rev higher because of the Isolastics?

Ben English (ben.english@dmvms.mailnet.state.ny.us) on NOC-L 16th. Apr 1997

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http://www.nortonownersclub.org/support ... n-bearings
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I don't recall seeing much discussion/comparison of the facr that BSA & Triumph cranks are 1 piece with a bolt-on flywheel, and Nortons are bolted-up 3 piece assemblies.

I'm sure that is a considerable factor.

May be a later tuning fing on XRs that I havnt put on . But They Required Superblends , Also . :!: read here . ; brien-folly-t12060.html



The Deal is the LOAD bearing ( pun ) CAPEABILITY .

Been wondering if Plain Rollers'd be fine in a Race Motor , Norton . IF CHANGED every 1.000 miles . As youd get more HORSEPOWER , as ball races absorb less . Less Drag .

Young Dunstall did his big Eight Ball Heavy Duty roller Bearings , slotted to accept balls ( notched so they fed in . ) these were MORE RIDGID .

So the CRANKSHAFTS BROKE .

The Ransome & Marles and Hoffman BARRELLED ROLLERS allow axial misalignment ( as per Hiem Joint / Sphereical connector , to a limited degree .

Therefore have the LOAD BEARING capeability of a plain roller bearing ( CONTACT Area . ) and a capeability of accepting missalignment . A Ball Race has Niether .

The BARRELLED ROLLERS are Just That . Not as some berks infer ' Rounded ends to stop them digging in ' ( The Ends of the rollers apparently did , if plain roller )
the infernal things are produced with a large radius , like a wooden wine / beer barrel , as are the tracks . The Crank can whip with the power impulses
without cracking up the next week link . Just like the H.D. XR 750 . Therfore you need a near ridgid crank with the other bearings .

Even a 72 Crank in a 650 Tri will root the bearings at 25.000 or earlier , if theyre ball , and it revs to 8.000 plus . A good thirty thou clearance at that stage .
As well it had 'lost its edge' at 20.000 .
If it'd kept the original output the excess clearances would have allowed ' MOVEMENT ' which translates to missalignment and shock load ( thru Slack ) exceeding
perhaps the ability to contain itself or suchlike . As in Correct tollerances are essential to optimum output . As well as Loctite .

hobot said:

This is actually an extension of my 13 yr asking everyone what limits rpm in Commando engines.

Click to expand...

What limits rpm in Commando engines is that they are not designed for high rpm. The engine parts are not strong enough to hold their shape at high rpm/power. The valve sizes are small because it is an undersquare engine. This is all pretty obvious.

This is why the state of the art "vintage racers" do not use Norton engines and in many cases Norton gearboxes and chassis anymore, they make new parts that look close to the original ones that will run at high rpm/power.

It is a bored rich-man's folly. The best thing for the 99%ers to do with their Norton twins is to run them basically as they were built and keep the rpm down to 6000 rpm, that way you can use all the nice old cheap parts that are laying around very successfully. And if you put as much work into finding torque and power below 6000 rpm as the rich people do trying to find it above that rpm, you will probably be able to out-run them in any practical scenarios anyway for much less money.
In the 1980s I beat a 750 Suzuki DOHC four down a 1/4 mile strip shifting a stock 850 Norton at 6000 rpm, just because my bike was so easy to ride that I pulled a huge lead off the line which the Suzuki rider never got back in that distance. He would have got it back if it was a longer straightaway, but it was not. I probably would have gone even faster if I would have had the brains to shift at 5000-5500.
I also beat a purpose-built, bored and stroked Harley shovelhead drag bike with a large slick and wheelie bars down the quarter mile with that 850! It had some teething/tuning/rider problems....

If I had stuffed a radical cam into the Norton, ported the head and stuck big carbs and exhaust pipes on that 850, then It would have taken a lot more riding talent and money to beat the Suzuki.

Same thing with automobiles, I had a 63' Chevy BelAir when I was younger that had an engine made up of all stock chevrolet parts. A stock 350 bottom end, 327 heads and an L-82 camshaft, cast iron intake and stock four-barrel carb. I beat a lot of cars at the drag strip that had been specially built and brought to the drag strip on trailers.

So there is my two cents. I enjoy the art of refining the stock Norton parts. If someone has the ability to tune and massage stock parts into doing a good job I can respect that a lot more than someone who dumps a wheelbarrow load of money onto something, erasing what it was and trying to make it into something it isn't for some poor reason.

Let the stock Norton twin power contest begin. Who will make the best dyno run with a Norton twin using all original or Andover replacement parts? Stock valve springs and cam and pistons and castings and carb sizes? Go ahead and mill the head, lighten the rockers, port it etc.. Just see what you can do with the stock parts.

Most of the guys who bolt a bunch of hot-rod parts together never get anything for the effort besides being able to say they own them.

What limits rpm in Commando engines is that they are not designed for high rpm. The engine parts are not strong enough to hold their shape at high rpm/power. The valve sizes are small because it is an undersquare engine. This is all pretty obvious.

This is why the state of the art "vintage racers" do not use Norton engines and in many cases Norton gearboxes and chassis anymore, they make new parts that look close to the original ones that will run at high rpm/power.

It is a bored rich-man's folly. The best thing for the 99%ers to do with their Norton twins is to run them basically as they were built and keep the rpm down to 6000 rpm, that way you can use all the nice old cheap parts that are laying around very successfully. And if you put as much work into finding torque and power below 6000 rpm as the rich people do trying to find it above that rpm, you will probably be able to out-run them in any practical scenarios anyway for much less money.
In the 1980s I beat a 750 Suzuki DOHC four down a 1/4 mile strip shifting a stock 850 Norton at 6000 rpm, just because my bike was so easy to ride that I pulled a huge lead off the line which the Suzuki rider never got back in that distance. He would have got it back if it was a longer straightaway, but it was not. I probably would have gone even faster if I would have had the brains to shift at 5000-5500.
I also beat a purpose-built, bored and stroked Harley shovelhead drag bike with a large slick and wheelie bars down the quarter mile with that 850! It had some teething/tuning/rider problems....

If I had stuffed a radical cam into the Norton, ported the head and stuck big carbs and exhaust pipes on that 850, then It would have taken a lot more riding talent and money to beat the Suzuki.

Same thing with automobiles, I had a 63' Chevy BelAir when I was younger that had an engine made up of all stock chevrolet parts. A stock 350 bottom end, 327 heads and an L-82 camshaft, cast iron intake and stock four-barrel carb. I beat a lot of cars at the drag strip that had been specially built and brought to the drag strip on trailers.

So there is my two cents. I enjoy the art of refining the stock Norton parts. If someone has the ability to tune and massage stock parts into doing a good job I can respect that a lot more than someone who dumps a wheelbarrow load of money onto something, erasing what it was and trying to make it into something it isn't for some poor reason.

Let the stock Norton twin power contest begin. Who will make the best dyno run with a Norton twin using all original or Andover replacement parts? Stock valve springs and cam and pistons and castings and carb sizes? Go ahead and mill the head, lighten the rockers, port it etc.. Just see what you can do with the stock parts.

Most of the guys who bolt a bunch of hot-rod parts together never get anything for the effort besides being able to say they own them.

Click to expand...

Oh My Beng, you blew me away with this unexpected but pertinent deviation response and will flash back on your surprise sprinting power a long time. I'm going to do it like you say, make one that not really a Norton but they won't understand that once catching up at stops and another with just Norton stuff that blew me and real life other away, it needs to be tested again and cheap enough even a poor un-bored guy can pull it off. Thanks for more uplift than my am coffee.

Beng, I totally agree with what you've said. If the balance factor in an 850 motor is 72 % it is extremely smooth at 6,500 rpm. What shags bearings and cases is the large weight being thrown around out of balance at high revs. When it happens at low revs, it is nowhere near as destructive. My Seeley commando is set up to handle and use as much torque as I can get it to deliver. Torque is the strength of the norton motor. If you want high revs, buy a weslake motor, and you will start where you finish with a norton motor. My own 850 motor is almost standard, but I use a two into one pipe and tapered ports. The cam appears to be standard 850, but I advanced it 15 degrees. The bike is very quick and nimble. I use methanol fuel.