Spintron Demo showing Norton cam & lifter wear

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Nice video, Jim. Very clear explanation of your points. Not sure I believe it's quite that simple, but I don't think there's any argument over using the lowest spring pressure that still keeps the valve train under control at the target rpm. And my experience with BSA lifters with both Axtell and Norris cams with profiles designed for them has been very good. But my experience (so far) has also been very good with stock flat tappet lifters and race cams (except for one, when the base fell off the lifter). But I have seen more wear on them than with the BSA radiused lifters. The caveat for that is that all my flat tappet experience is with a max red line of 7200 rpm, and reasonable profile road race cams, not the super aggressive N480 sorts of grinds. I have had good luck with the BSA lifters ground to a smaller radius and the Norris N460 cam, which is pretty aggressive. I've run that combo in a short stroke 750 for road racing, and in a 920 in a fair number of road races and several Bonneville landspeed events, with almost no wear. For what it's worth, all those experiences were with either S&W valve springs (back in the day), or very similar RD springs after S&W quit the business. I think once you get into the ultra short stroke, high rpm engines, with serious cam profiles, you almost have to use something like the BSA lifters. I've been having some difficulties with one of those engines, but not sure yet if it has much to do with cams, lifters, and springs. Trying to sort that out now. I've also been running a Webcam 12A for several years now in an 883 street Commando, with stock lifters ground to a radius by Jim Comstock, and it seems to be holding up very well.

I think the Norton community is fortunate to have so much research going on in the can and valve train area by folks like you and Jim Comstock, as well as the lifter design work at Andover Norton. There are a lot more options available now than when I started racing them back in the early '70s.

Ken
 
When I was racing I didn’t have access to a spintron or slow mo video camera. But what we did do was remove the valve covers, run the bike on the rolling road, and point an ign timing strobe light at the valve gear. It was surprising what we saw doing something so simple.

At the time, I was going down the route of lighter and lighter valve gear and really light springs. But I had suffered a couple of dropped valves, and was trying to work out why, hence the strobe light.

To cut a long story short, what we saw really surprised and scared me. The valve gear was bending and springing and fretting and bouncing all over the place! After only a few seconds looking I thought it no wonder I’d dropped a couple of valves, the surprise was I’d not dropped more!

The bottom line was we’d gone too far. The springs are not only there to close the valve, they are there to control the valve train. Too much pressure is bad for wear and power, too little means loss of control which is bad for wear and dropped valves!

I rode bikes where we’d got it right, and the minimal spring weight could be felt directly, with the motor picking up and dropping revs very quickly. But none of us were clever enough to actually work any of this out properly beforehand, we were just doing trail and error, which got to be quite time and cash consuming and was resulting in too many DNFs !
 
Fast Eddie said:
When I was racing I didn’t have access to a spintron or slow mo video camera. But what we did do was remove the valve covers, run the bike on the rolling road, and point an ign timing strobe light at the valve gear. It was surprising what we saw doing something so simple.

At the time, I was going down the route of lighter and lighter valve gear and really light springs. But I had suffered a couple of dropped valves, and was trying to work out why, hence the strobe light.

To cut a long story short, what we saw really surprised and scared me. The valve gear was bending and springing and fretting and bouncing all over the place! After only a few seconds looking I thought it no wonder I’d dropped a couple of valves, the surprise was I’d not dropped more!

The bottom line was we’d gone too far. The springs are not only there to close the valve, they are there to control the valve train. Too much pressure is bad for wear and power, too little means loss of control which is bad for wear and dropped valves!

I rode bikes where we’d got it right, and the minimal spring weight could be felt directly, with the motor picking up and dropping revs very quickly. But none of us were clever enough to actually work any of this out properly beforehand, we were just doing trail and error, which got to be quite time and cash consuming and was resulting in too many DNFs !
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Should have gone for a Desmodromic valve system, weak springs and a cam to close the valves!
 
Fast Eddie said:
I’ve got one, soon to be two of those now !
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Spintron Demo showing Norton cam & lifter wear
 
What happens with street cams is somewhat predictable as shown with the spintron. The purpose of the vid was to show how wear occurs on street RPM Norton cams and lifters.

But when race cams get up to 9000 RPM weird things can happen and you have to do whatever is needed to keep from dropping a valve and that means reducing reciprocating weight (without creating flex or weakness) and reducing valve bounce with more gradual closing ramps (also asymmetrical cams).

I saw one very strange cam with the phenomenon of a wear line on the heel of only one cam lobe (the rest were fine) where nothing should have been rubbing the cam because the valve was on the seat at that point. And this wear line was located later than valve bounce would occur. Explain that one to me.
 
grandpaul said:
Why not build some trick roller lifters? ALA new Norton...
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Weslake 500cc speedway roller lifters can be adapted but they are problematic if not set up accurately. The BSA lifters are more reliable.
 
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As much as I like the idea of a roller lifter cam, they have their issues too, at least when applied to Commandos. Doesn't mean it can't be done, but I don't think it is as simple as plug and play. Small lobes, small diameter rollers, and no center cam bearing all make it a difficult application. Works for the 961 because Kenny made sure to leave room for larger diameter, wider rollers. I would guess the cam lobes are a bit larger in diameter also, judging from pictures, but I can't be sure.

I've seen it done for a Triumph twin flat track bike, and it worked well. The same lifters have been used in a Commando conversion, but as far as I know that one was never tested in a running engine.

With all the work going on lately with both standard design lifters and BSA style lifters, as well as cams, I think we'll end up with combinations that work well for long term street use reliability as well as seriously abused, high rev race engines, but they might not be the same solutions.

Ken
 
Matchless used roller followers in the G45, admittedly with a very aggresive cam, & from what I have read they don't seem to have been all that reliable.

Martyn.
 
Here it is with Weslake parts (I think). Someone go for it and make a fortune (ha ha). I'll come up with the cams.

Spintron Demo showing Norton cam & lifter wear
 
This is a picture of them in the cylinders, taken from the Cootes' excellent series of manuals. You can see why you couldn't adapt them to the older Commandos.

Spintron Demo showing Norton cam & lifter wear


Ken
 
I was wondering if a spring could be used at the follower itself to control it, then spring pressure can be lessened at the valve so its sharing the load
 
Bernhard said:
Hmmm indeed, you would only make it more complicated, it's the valves that need to be controlled.
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When valves bounce is it the spring loosing control or a combination of lifter as well, there is no spintron footage of what the lifter is doing,
Rolls Royce also used camshaft dampers to stop the cam flicking or jumping

How do i post a photo from a pc onto here?
 
Valves bounce back off the seat at high RPM from inadequate closing ramps. And Spintron tests have shown that the Norton cam flexes enough at high RPM that it can actually push back on the lifter (after the valve hits the seat) and lift the valve the same as valve bounce. A half moon bronze support under the cam center helps eliminate cam flex.

Someone please help Jason Wright with photo posting options. There should be a link somewhere on this forum.
 
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