Cam followers - Andover to the rescue?

This just popped into my inbox, kudos to Andover for the investment in time and research:

"With metallurgists on both sides of the Atlantic looking at this, a new material was formulated that would allow casting but was a little under the required hardness we needed. This was spotted by the metallurgists who then used their experience to adjust it chemically to have a better wear characteristic compensating the small loss in hardness. This moved us away from the iron based material into a cobalt based material. The cost of this was looked at and the difference in increased cost and the lack of other options made it viable.

Finally a batch was cast and machined, dimensionally perfect and cosmetically looking more of an precision part than the old type. As for testing, some have been sent to a static test rig and a radiused set will be dropped into my bike in the week or so. We are pretty confident the testing will give the results expected, in which case they could be on sale in less than a month, price to be confirmed."

No more stellite feet popping off and destroying engines!

It is to be hoped that the comnoz test rig is being utilised for the static testing, and hopefully not just one, but several oils are used to obtain a spread of results.

Another major problem issue is the known variation of hardness among the cams now available for the engines, and how the followers will behave when used in conjunction with poor hardness examples.


I would like to see these followers be a success, their introduction shows a desire on the part of Andover Norton to improve a product where history has shown a need, and an innovative approach to improve the base metal itself is again to be commended.

For many Norton Commando owners though, for a while they'll still be in a suck it and see situation, and could well end up being acting but unpaid guinea pigs.

Awesome news. I'm surprised that AN took this project on. I've had one pad pop off while idling in the driveway, and I know of another norton rider who's engine was trashed by a delaminated pad that came off at speed on a ride. I always wondered what percentage of commando's eventually have this potentially catastrophic part failure occur....

@Snotzo yes, I suggested that Andover send a set to Jim a month ago. They said they’ve got no problem doing that once they’ve finished their own testing.

Snotzo said:

Another major problem issue is the known variation of hardness among the cams now available for the engines, and how the followers will behave when used in conjunction with poor hardness examples.

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They note cam differentiation as well:

"We needed a tappet that suited all cams in use and in the future, including hard faced welded cams, chill cast cams, nitrided cams and case hardened cams, which all present different hardness ranges that we had to consider leaving a very narrow window of hardness we could aim for. The investment castings were designed and a batch cast, but there was gassing issues with the material. This material, despite giving us the ideal hardness range window, would not cast well. Other materials were tried, but still gassing was an issue. The problem is that though plenty of materials exist to meet the hardness, many will not cast, or would cast but then not take a hardening process to suit what we needed."

I don't have a stock cam follower nearby to look at, but these new ones appear to be hollow in design, which should translate to lighter than the originals.
I always thought the stock ones looked large and heavy, and wondered about the negative effect this mass would have on the valve train.

Stephen Hill
Victoria, BC

Hi, Stephen. The factory followers (I guess that should be factories since it includes Bracebridge St, Plumstead Rd, and Marston Rd.) were hollow. John Hudson was concerned by the issue of the weight of the oil inside that hollow cavity so he encouraged the process of drilling a hole near the bottom of the inner face (the flat part) to allow oil to drain out. IWSTM that would direct additional oil to the cam lobe/lifter interface in use but I have no empirical data to support that.

I have around 35 hours of run time on the new followers. The results are not ready yet.

I can say one thing, the PW3 cam they sent for testing has really been tough on my spintron's valvetrain when I tried running it between 6000 and 7000 rpm for any length of time.

So far, one broken valve, two broken KPM racing spring retainers, one pulled through RD spring retainer, three bent valves and a few pushrods.

comnoz said:

I have around 35 hours of run time on the new followers. The results are not ready yet.

I can say one thing, the PW3 cam they sent for testing has really been tough on my spintron's valvetrain when I tried running it between 6000 and 7000 rpm for any length of time.

So far, one broken valve, two broken KPM racing spring retainers, one pulled through RD spring retainer, three bent valves and a few pushrods.

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Was that the cam's fault?

comnoz said:

I have around 35 hours of run time on the new followers. The results are not ready yet.

I can say one thing, the PW3 cam they sent for testing has really been tough on my spintron's valvetrain when I tried running it between 6000 and 7000 rpm for any length of time.

So far, one broken valve, two broken KPM racing spring retainers, one pulled through RD spring retainer, three bent valves and a few pushrods.
View attachment 13002 View attachment 13003

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This is very interesting and I’m surprised.

I used a PW3 cam bought from Mike Hennings about 2000 and used it for about 10 years in my 500 Domminator race bike. I estimate at least 30 hours of race time. Probably more like 50 hours. In later years I used a GoPro that also recorded a tacho video. The bike was routinely reved to 7500 to 8000.

I had not a single problem with the valve train and both cam and followers are in perfect condition. I always used Castrol R 40. I spent a lot of time checking for valve spring coil bind and setting up spring pressure.

I do know from measuring other cams that not all cams with the same label on them measure up the same.

It might be worth getting that cam measured and calculating the dynamics.

Regarding the weight, I got the newsletter too, and this is part of it:

"Many will be asking what the weight is of these, I checked them and found that compared to the previous Norton offering they were 9gms heavier, but this tappet was a redesign in 1984, so I decided to weigh some originals, which were just 4gms lighter than the new one piece design. I suspect this is due to the cobalt content being more dense than an iron based content."

Once they are full of oil I guess that will go up a little bit. But you have to applaud AN for their efforts.


Cheers,

cliffa.

swooshdave said:

Was that the cam's fault?

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The broken parts were a result of harsh closing ramps causing failure of the spring retainers. The KPM retainers were 10 degree aluminum. Both broke at about the same time after ~1 hour at 6000 rpm.
[I also know of some racers who have broken the KPM retainers when using a big cam. But this is the first time I have broken them]

The RD retainer was one of their early TI retainers and was quite lightweight. It allowed the collets to pull through on the intake after 10 minutes at 6500 rpm.

After I went ahead and installed a pair of my springs and retainers the only failure I had was breaking the bolts that held the quick change adapter, which let the cam move to the right. It had run quite a while at 7000.

The PW3 has always shown to produce a lot of valve bounce and has been one of the tougher cams to control.
It also produces the most noise of any cam I have run. Ear protection is an absolute must when running one in the spintron.
That's part of the reason I wanted to use it -to put the test to the followers.

Loud valves save lives. Glad to hear you are looking at these Jim.

Holy Guacamole!

Fun stuff.

Thank you all for the above, especially for Jim and the time and effort he has put in.
The result was mixed, the followers seemed to have had a hard time on the Chill cast PW3, maybe I should have sent the beast of PW4. known to me and Jim is that the hardness of this cobalt based material was in the top end of the hardness of chill cast. It ran for 31 hours, but wear was an issue, this could be due to purely the wear characteristic of the material holding it up. Strangely, the NOS cam test, where it would seem good hardness separation was had failed in less than 20 mins.
The parts will be assessed by the manufacturer when I get them back. As Jim will confirm, these were a stellite type material, containing some hefty base metals, on paper it should have held up. The problem is that cobalt, the balance material as found in Stellite is soft, hardness testing of stellite is also hard to determine because of this, as testing gets into the matrix, so despite having a lower reading the wear characteristic would be the equivalent of a higher reading in an iron based material. It seems it needs a tweak to get the matrix to form correctly.
These are nicely cast and machined, hopefully the metallurgists can see what has happened and tweak the chemistry, their concern was that they had no real test data to work from, now they do.
I might have lost this battle, but despite a crap day, I will win this war.
Then it will be, pushrods, exhaust valves, valve springs, con rods, etc all which it seems were all taken for granted by those in the 60's and 70's who could have checked and improved back then.

The con rod - unbeknown to many AN was the first to forge a high spec Kaiser alloy in Europe, and only one company in the USA has done it, sadly they will not disclose how to heat treat it, shame as we could have alloy forged rods 30% stronger than standard. I have just enough to try and pull test, but this not a priority at the moment.

My days do not stand still, and I will certainly challenge the 'that's the way we have always done it' just like cracked cylinder heads, now easily repaired by laser welding - just had to find someone with the equipment that was happy to use it for sub contract work. Some of the secrets must stay that way, like the soon to be mainshaft and layshaft that will actually have a chance of running parallel to each other.

If you are In the AN area, feel free to pop in and have a cuppa and gain a deeper insight to my day and AN plans.

Don't completely give up on the followers yet. I have found a plugged oil squirter that may have affected the NOS cam test. I don't know -so I am doing that test again.

Well, never mind.

When I cleaned up the machine after the last failure I found one of the four oil squirters was plugged. It still should have had plenty of lube but, I though there was a chance it caused the failure at 20 to 30 minutes with the NOS cam.
So I cleaned it out good and changed the oil and filter. I resurfaced the followers and moved them to the other side of the cam that was still untouched. This time I filled it with Castrol GTX instead of Mobil 1 v-twin oil.

This time it failed in 10 minutes. The cam to follower seizure was bad enough to actually stop the spintron.

Definitely not compatible.

Madnorton said:

If you are In the AN area, feel free to pop in and have a cuppa and gain a deeper insight to my day and AN plans.

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Pity they don't have a coffee machine.... commented on this to them yesterday