Cam and follower tests.

Mr. Rick said:

my mind went to the Norton cam and its flexing propensity, and whether the attempts to control that flexing might possibly be counter-productive. Is it possible that the cam flexing is actually "absorbing" some of the hammering transmitted to the followers?

Click to expand...

Hardly. Think of the camshaft as a very stiff spring acting on the camshaft lifter. Spring needs to be stiff to ensure continuous contact with the lifter. Now let us reduce that stiffness. What happens? Firstly, the camshaft produces less lift. Secondly, on closing ramp the valve train and camshaft start to exhibit harmonic vibrations, causing intermittent contact between lifter and camshaft lobe. Dynamic forces are usually higher than the static forces - a factor of 2-3 is not uncommon. Thus you do want the camshaft to be as stiff as possible wrp. to the bending action. Fitting an hydraulic lifter is much more sensible for managing dynamics in the valve train.

-Knut

mdt-son said:

Fitting an hydraulic lifter is much more sensible for managing dynamics in the valve train. -Knut

Click to expand...

New to me. How? Hydraulics - incompressible fluid - solid?

Jim

As a material for hard facing the Norton followers I wonder what you think of this product. It is a brazing rod that is easily applied to various steels or cast iron. Hardness possibly not quite at Rc55-62. it was used on the Ariel cam followers to run on a stellite welded cam that you previously provided advice on. The followers were polished, with no visible wear, and the photos showed the damaged cam.

The manufacturers details are

9000 EUTECBOR

PRINCIPAL APPLICATIONS: Cams, augers, mixer blades OTHER USES: Patterns, guides, screws OUTSTANDING FEATURES: Polishes in service; Low heat application; High hardness and corrosion resistance; Outstanding frictional wear resistance RECOMMENDATIONS: For TeroCote protective coatings requiring severe abrasion-and-corrosion resisting deposits, and compressive load strength at elevated temperatures. For use on steel, alloyed steel, cast iron, high chromium and nickel alloys. Non-magnetic and non-heat treatable. Deposits accept a high polish and resist pitting and galling.

Hardness: Rc 55-62 Bonding temp: 965°C



http://www.smenco.com.au/wp-content/uploads/2016/07/DataBookDec2015.compressed.pdf

ando

Dances with Shrapnel said:

New to me. How? Hydraulics - incompressible fluid - solid?

Click to expand...

Hydraulics are easier on the system because there is no "clearance" so there is no impact when the lifter takes up the slack (clearance) and bangs into the rest of the valve train. The concept of the hydraulic lifter is better in every way than a solid BUT in practice there are RPM limits that makes typical HYDs not suitable for RPM much in excess of 6K.

Dances with Shrapnel said:

New to me. How? Hydraulics - incompressible fluid - solid?

Click to expand...

Yes, virtually incompressible in this low pressure domain (100 psi = 0.7 MPa), but remember the oil is saturated with air, i.e. due to the stirred action there will always be some air trapped in the oil which increasing compressibility quite a bit, and there is leakdown from the compression chamber of an hydraulic lifter , both of which will act as dampers. The main advantage is this though:
"Hydraulic lifters are also kinder on valvetrain components than solid lifters because zero valve lash reduces the hammering effect that occurs when the valves slam shut at higher engine speeds. There’s no air gap to fill so the valve simply follows the cam lobe as it closes for a more gentle landing. This also reduces noise and helps extend the life of the valvetrain components."

http://www.enginebuildermag.com/2017/09/basics-valve-lifters-beyond/


-Knut

MexicoMike said:

The concept of the hydraulic lifter is better in every way than a solid BUT in practice there are RPM limits that makes typical HYDs not suitable for RPM much in excess of 6K.

Click to expand...

True for yesterday's technology. Today there are hydraulic lifters capable of doing 8000 rpm. Even if the rev limit was set at 7000 rpm, this would be more than adequate for a Commando street bike, as max torque is gained at 5000 rpm for a long-stroke engine, and an estimated 6000 rpm for a modern shortstroke engine.
Even for 81x75mm ultra-shortstrokes, peak power delivery is in the 7200 rpm range.

Ref. Harley Davidson Sportster Performance Handbook. (c) 2006

-Knut

Honda CBX 750 engines used hydraulic tappets & they reved to 9500rpm if I remember.

Never thought hydraulic lifters could be that responsive at high speed to ameliorate hammering in the valve events that Jim C is reporting on. Hydraulic tappets were (to me) only hydraulic slack adjusters. If the high speed behavior as alluded to above is accurate, in my opinion, that would be treating the symptom, not the cause, with an heavier component that would only exasperate the problem.

ando said:

Jim

As a material for hard facing the Norton followers I wonder what you think of this product. It is a brazing rod that is easily applied to various steels or cast iron. Hardness possibly not quite at Rc55-62. it was used on the Ariel cam followers to run on a stellite welded cam that you previously provided advice on. The followers were polished, with no visible wear, and the photos showed the damaged cam.

The manufacturers details are

9000 EUTECBOR

PRINCIPAL APPLICATIONS: Cams, augers, mixer blades OTHER USES: Patterns, guides, screws OUTSTANDING FEATURES: Polishes in service; Low heat application; High hardness and corrosion resistance; Outstanding frictional wear resistance RECOMMENDATIONS: For TeroCote protective coatings requiring severe abrasion-and-corrosion resisting deposits, and compressive load strength at elevated temperatures. For use on steel, alloyed steel, cast iron, high chromium and nickel alloys. Non-magnetic and non-heat treatable. Deposits accept a high polish and resist pitting and galling.

Hardness: Rc 55-62 Bonding temp: 965°C



http://www.smenco.com.au/wp-content/uploads/2016/07/DataBookDec2015.compressed.pdf

ando

Click to expand...

I have that alloy here in a spray powder. I tried it on a couple followers but the hardness came out right around RHc55. Since that was about the same as the cam I did not try running it. Rod applied with a torch might be a little harder.

The best results so far seem to be with a hardness about 62 to 63.

Dances with Shrapnel said:

If the high speed behavior as alluded to above is accurate, in my opinion, that would be treating the symptom, not the cause, with an heavier component that would only exasperate the problem.

Click to expand...

If part of the problem _is_ the lash and it's amplification of the hammering effect, then hydraulic lifters treats that cause. You think the heavier lifter aggravates the hammering problem? Not so by experience. It is true that stronger valve springs are required to compensate for heavier lifters, and the spring weight goes into the inertial equataion by 1/3 of its mass. Since 1/3 of the _added_ spring weight (of stiffer springs) is a very small figure, the effect on the upper part of the valve train is virtually none. How much heavier is a hydraulic lifter vs. a solid lifter? Not that much, considering the hollow bodies, which probably can be made even lighter by using modern materials such as a titanium alloy.

However, if the main culprit is abrasive wear of camshaft and lifter, adding weight to the valve train would be a step in the wrong direction. However, hydraulic lifters have stood the test in other engines and I think it's a matter of choosing the correct materials for the task.

Please don't forget the benefit of longer duration valve lifting, less valve overlap and increased engine power due to a more efficient combustion process.

-Knut

S&S used to claim (maybe still does?) that their hydraulics can manage 8k RPM but whether they can function properly at that RPM depended on the cam profile. Crane cams recommended their hydraulics for no more than 6.5-7k, again, stating that max RPM capability depended on the cam profile. In the applications I'm most familiar with, the cam profile was somewhat (or very) aggressive and hydraulics just weren't up to 8k (or even 7) with those cams.

But, I admit I've been away from that world for several years now so maybe current Hyd lifters can handle that level of RPM regardless of profile. In any case, as noted, RPM-wise it's probably not a factor for a Norton motor regardless of cam profile!

RE CBX: The only Honda CBX I'm familiar with was the 6 cyl 1000cc. I didn't know they used "CBX" with any other bike so I've learned something about Hondas! I know the CBX 6yl used shims, having spent quite a bit of time cursing them ..."Do we REALLY NEED a bike with SIX F&^%#ng cylinders?!!!). However some Honda engines did have self adjusting valves using oil feed. But that was just a simple oil-feed adjuster, not as complex, large and heavy as the type of hydraulic valve lifter necessary for use in OHV engines.

mdt-son said:

If part of the problem _is_ the lash and it's amplification of the hammering effect, then hydraulic lifters treats that cause.

Click to expand...

“If”......Quite the hypothetical and not what we are talking about with JimC’s observations. Proper cam and valve train design is the solution. JimC is reporting hammering well past any lash event. Hydraulic lifters must maintain a foot, outer body and inner body, oh and filled to the top with oil. Suggesting you can make a hydraulic lifter lighter with Ti, well a properly designed non-hydraulic in Ti would be even lighter - but that is silly and off the mark for what are the apparent issues with Commandos: hammer past the nose, scuff and wear due to incompatible metallurgy (hardness?) and hard face coming off due to poor workmanship and process.
I read the article in the link you provided. The bit about the additional lift and duration is a bit of a red herring. Sure, if you swap out solid with hydraulic for a given cam this is true but you can also design a cam and solid follower to get he exact lift and duration you want. The article goes in to say one gives up flexibility in tuning with a hydraulic as you cannot adjust duration and lift like you can with solids.

mdt-son said:

If part of the problem _is_ the lash and it's amplification of the hammering effect, then hydraulic lifters treats that cause. You think the heavier lifter aggravates the hammering problem? Not so by experience. It is true that stronger valve springs are required to compensate for heavier lifters, and the spring weight goes into the inertial equataion by 1/3 of its mass. Since 1/3 of the _added_ spring weight (of stiffer springs) is a very small figure, the effect on the upper part of the valve train is virtually none. How much heavier is a hydraulic lifter vs. a solid lifter? Not that much, considering the hollow bodies, which probably can be made even lighter by using modern materials such as a titanium alloy.

However, if the main culprit is abrasive wear of camshaft and lifter, adding weight to the valve train would be a step in the wrong direction. However, hydraulic lifters have stood the test in other engines and I think it's a matter of choosing the correct materials for the task.

Please don't forget the benefit of longer duration valve lifting, less valve overlap and increased engine power due to a more efficient combustion process.

-Knut

Click to expand...

Reduced overlap and long duration has it's place in a more modern engine design that is capable of producing power at higher RPM levels. It definitely has advantages in reducing valve train loads but,
Personally I do not like what reduced overlap and long duration do to a Norton motor. It takes out that midrange surge that is the Norton's best attribute.

Dances with Shrapnel said:

“If”......Quite the hypothetical and not what we are talking about with JimC’s observations. Proper cam and valve train design is the solution. JimC is reporting hammering well past any lash event.

Click to expand...

Dear Dances, please let's not start a religious war here. Even though development of a hydraulic tappet is not on the table right now, it doesn't mean it can't be a topic in the future.

"If" is not a hypothetical statement, rather it idicates an uncertainty as to what is really going on at the lobe/tappet interface, which no one really comprehends according to my understanding of what has been written here. If you know otherwise, you should prescribe a solution right now! "Proper cam and valve design" is a rather vague and general statement! Sure - we want a proper design, but how? Is the valve train of our Norton engines "proper" otherwise? Obviously not, considering the camshaft flexing, etc. How well-designed the rockers, valves and springs are I don't know.

Apart from parts failing due to obvious manufacturing defects, which doesn't need further consideration, there are basically two known factors occuring at the camshaft lobe / lifter interface: Abrasive wear, and valve train dynamics (the hammering effect) causing spiky contact forces past the camshaft lobe apex. I haven't read a statment by JimC in which he correlates hammering and valve lash. This would be an extremely difficult observation, with the lube oil present, compression of push rods, deflection of the camshaft, various thermal elongations, etc. all occuring simultaneously. Maybe a high speed non-contact laser sensor paired with a built-in compression sension in the lifter enables recording time series of the lobe/follower contact area which would allow such statements to be made. The best laser sensors provide a resolution of .04 micrometer only and on short range will probably penetrate the oil splash. However, I don't think JimC is equipped for such measurements now.

It's interesting to note that abnormal wear of the tappets also affects the BMW airhead engines, despite that maker's rigorous quality control.

I rest my case.

-Knut

mdt-son said:

Dear Dances, please let's not start a religious war here. Even though development of a hydraulic tappet is not on the table right now, it doesn't mean it can't be a topic in the future.

"If" is not a hypothetical statement, rather it idicates an uncertainty as to what is really going on at the lobe/tappet interface, which no one really comprehends according to my understanding of what has been written here. If you know otherwise, you should prescribe a solution right now! "Proper cam and valve design" is a rather vague and general statement! Sure - we want a proper design, but how? Is the valve train of our Norton engines "proper" otherwise? Obviously not, considering the camshaft flexing, etc. How well-designed the rockers, valves and springs are I don't know.

Apart from parts failing due to obvious manufacturing defects, which doesn't need further consideration, there are basically two known factors occuring at the camshaft lobe / lifter interface: Abrasive wear, and valve train dynamics (the hammering effect) causing spiky contact forces past the camshaft lobe apex. I haven't read a statment by JimC in which he correlates hammering and valve lash. This would be an extremely difficult observation, with the lube oil present, compression of push rods, deflection of the camshaft, various thermal elongations, etc. all occuring simultaneously. Maybe a high speed non-contact laser sensor paired with a built-in compression sension in the lifter enables recording time series of the lobe/follower contact area which would allow such statements to be made. The best laser sensors provide a resolution of .04 micrometer only and on short range will probably penetrate the oil splash. However, I don't think JimC is equipped for such measurements now.

It's interesting to note that abnormal wear of the tappets also affects the BMW airhead engines, despite that maker's rigorous quality control.

I rest my case.

-Knut

Click to expand...

Actually I do have a follower with a load cell and a laser displacement sensor.

Getting meaningful information from them is questionable but I have monitored them with a digital scope and learned a few things.

Based on your last post Knut, I believe you got my point. Thanks.

comnoz said:

It definitely has advantages in reducing valve train loads but,
Personally I do not like what reduced overlap and long duration do to a Norton motor. It takes out that midrange surge that is the Norton's best attribute.

Click to expand...

Jim, just a clarification. Duration and overlap does not affect valve train load as I see it.
Hydraulic lifters usually reduces valve train loads due to the effects mentioned in my prevoius postings. I can't say how it would affect valve train dynamics in the Norton engine, for obvious reasons.

As far as overlap goes, the difference between solid and hydraulic lifters is that solid lifters doesn't allow precise valve control, while an hydraulic lifter does. Hence, the overlap necessary when designing a camshaft for hydraulic lifters can be shorter (steeper and shorter ramps), which also means the gas charge in the cylinder will be greater, hence better volumetric efficiency. Thus, the mid-range torque curve could actually improve over stock design when using hydraulic lifters and tailor-made camshafts.

-Knut

comnoz said:

It definitely has advantages in reducing valve train loads but,..........

Click to expand...

Do you honestly think a hydraulic follower would be of any benefit where you are seeing the apparent hammering of the cam lobe on a Norton Commando after the peak? I get the part about approaching the lobe and departing the lobe but when you approach valve float or other high speed motions or phenomena I doubt the hydraulic would respond in any consequential way other than maybe pump up and keep the valves from closing.

Dances, for your information the Norton 961 features hydraulic lifters and has an 8000 rpm redline ..... max power at 6500 rpm.
I think the racing fraternity should be satisfied by these figures. Those who want to rev past 8000 rpm should consider switching to some DOHC engine.

-Knut

Not debating the high speed capability to perform but they have their limitations and problems including weight and pumping up during valve float. The theoretical application of a hydraulic lifter to fix a problem that may very well not be "fixable" by a hydraulic lifter or even exasperated by a hydraulic lifter is my point. If one is going to go through all the trouble to design to a hydraulic lifter, I say direct design efforts towards fixing the problem. Staying on topic here - the Norton twins have a long history of performing well on street and race trim. There have been cases of cam failures and there have been cases of hard face separating from the follower. Some of these are OEM matters and some appear to be newly manufactured component failures. The solutions is out there, it is not that complicated and JimC and others have brought some useful and relevant insight to the issues.

My point is, as you say "maybe a topic for some future discussion". I see hydraulic lifters as a wonderful answer to maintenance free valve trains. My recollection was they were in widespread use in the US auto industry in the late 1940's to early 1950's (Cadillac in the 1930s) in what should have been relatively dimensionally stable water cooled cast iron engines with chromoly pushrods. One could have certainly made the case for some sort of use of hydraulic lifters for all the various air cooled pushrod motorcycle engines of that era and going forward with cast iron barrels, alloy pushrods and all sorts of permutations wreaking havoc on hot and cold valve lash. What better way to do away with the pesky valve adjustment interval.....................but they did not. Hmmm.

So you say the 961's run hydraulics, I say low maintenance feature - great! As for the racing fraternity, (at least with vintage motorcycles) I cannot name one high performance pushrod vintage bike that even ran hydraulic (or showed a gain in performance)....Hmmmm. I am sure someone can cite some obscure bike like Nimbus 3-1/2 cylinder race bike. My 750 Short stroke technically redlines (based on mean piston speed) at around 8,350 rpm and goes well beyond that. My 500 would go to +10,000 rpm though we restricted to around 9,500 with a rev limiter so yeah, we will sit here and consider a DOHC engine.

One reference even states "Also hydraulic lifters can create "valve bounce" at high RPM which is undesirable for performance uses. This is why engine tuners prefer solid lifters instead."

All things that glitter are not gold.