New non symmetrical cams finally

[jseng1]

It’s taken a couple years with some help from John Andrews cams and his (polynumerical etc) cam design software. But the non symmetrical (asymmentrical) Norton cams are finally here. The point of being non symmetrical is to find the ideal shape for the opening side and also for the closing side, The requirements of each is different. The opening ramp cam be more abrupt as long as you don’t overstress the rocker arm and other cam train components. Changing the opening ramp changes the entire opening side cam profile along with it. The closing side needs a more gentle ramp to bring the valve down softly to prevent valve bounce. Bounce occurs at high RPM and if its too severe then the opening intake valve can tangle with the closing exhaust valve resulting in a damaged head. With too much bounce the exhaust gases will contaminate the intake charge.

You don’t want the closing intake valve to bounce either or you will lose compression and power. Its a balancing act.

The profile below is close to the lift and duration of a stock Norton cam. If you look closely you can see that the opening ramp on the left is shorter than the closing ramp on the right. Other differences between the opening and closing flanks are too fine to see in the image but all the numbers are different.

Below is some of the cam software data. On the right side you can see that the closing ramp has a lower jerk curve. You can see the different inputs for the ramps in the lower left corner.

Its not a radical departure from existing Norton cam designs. But its more refined. Easier on the valve train and more efficient.

Plasma nitrided hardened tool steel billets at extra cost for longevity.

 

[texasSlick]

Nice. I have long wondered why someone did not pursue this approach.

Slick

 

[Fast Eddie]

Interesting stuff Jim, are they for BSA lifters or Norton?

Are you doing performance versions with the same logic?

 

[acotrel]

I don't know about BSA lifters, but in the stellite tipped Triumph lifters there are two radiuses. With the E3134 race cams, It is important to use the R-type which have the bigger radius. What interests me is not so much the actual opening and closing rates, but the timings. With two-strokes the port timings determine the position of the power band within the usable rev range. The same thing happens with valve timings in a four stroke, and the exhaust system type is just as important. With a four stroke, because there is more torque, any nasty bump in the way power is delivered, makes a bike much harder to ride well. If a race cam's timings are adjusted to suit a two into one exhaust system , the power delivery is often stronger and smoother. So If I was designing a cam, I would try to develop it in conjunction with a two into one exhaust system rather than with separate pipes.

 

[acotrel]

With a Commando engine, making provision for it to spin safely over 7000 RPM is expensive. So developing a cam to gain horsepower by raising the usable rev range is not the way to go. However, with a 2 into 1 exhaust system, you should be able to put the usable rev range where you want it with any cam.

 

[jseng1]

Fast Eddie and Acotrel

They are for 1-1/8" radiused BSA A65 lifters. Or I can radius your stock Norton lifters to 1-1/8"

And yes the non-symmetrical (asymmetrical) profile is good for both street and racing.

The JS3 is a hot race cam and needs special 7/8" radiused lifters to keep from riding off the edge of the lifters because of its long duration.

The "R" lifter Acotrel refers to is a Triumph 1-1/8" radius lifter. Its called an "R" because it gives longer duration with the same cam as a Triumph with "S" 7/8" radiused lifters (standard lifters).

All BSA A65 lifters were 1-1/8"

 

[Fast Eddie]

Jim, what I meant was; are you going to do non symmetrical versions of your JS#1,2,3 profiles?

 

[acotrel]

standard 750 timings at 0.013 inch lift are
IO BTDC 50
IC ABDC 74
EO BBDC 82
EC ATDC 42

What timings are recommended for your new asymetric cam, if separate pipes are used ? Are the lobe centres different ?

 

[jseng1]

Jim, what I meant was; are you going to do non symmetrical versions of your JS#1,2,3 profiles?

Yes I have the non symmetrical profiles for JS0 (lift/dur similar to stock), JS1 (lift/dur similar to Axtell #3), JS2 (lift/dur similar to PW3), JS3 (lift/dur similar to D+), but only a few of each were made this first batch so I could verify the specs. For the time being you have to ask for them but I'm pretty sure I will be going all in with this design.

Complete cam timing specs come with the instructions.

Here's an image of all 4 profiles with the shorter opening side on the left.

 

[MexicoMike]

While I appreciate the research/machining involved in such work, what does this cam profile have to offer over the stock Commando cam when used on a stock Commando? I can certainly understand an improved profile if the goal is to make a higher RPM Norton motor, which would also require a change to other major engine parts, but I don't see any benefit to a stock motor. But perhaps I am missing something? Or, could I be just "massively Retarded?"

 

[acotrel]

If you use a cam which delivers more top end power, you can sometimes reduce the rev level at which max horsepower occurs by using a 2 into 1 exhaust system. But I use a near-standard 850 cam which is advanced 12 degrees with a 2 into 1 exhaust system to get more torque and it will go straight through the top, if I let it. I always try to keep the revs below 7000, but I always see about 7,500 on the way up through the box. It is almost impossible to avoid over-revving.

 

[Fast Eddie]

While I appreciate the research/machining involved in such work, what does this cam profile have to offer over the stock Commando cam when used on a stock Commando? I can certainly understand an improved profile if the goal is to make a higher RPM Norton motor, which would also require a change to other major engine parts, but I don't see any benefit to a stock motor. But perhaps I am missing something? Or, could I be just "massively Retarded?"

Less stress on the valve train, longer life of valve train components, the ability to lower spring rates. Etc.

In theory at least.

 

[Snotzo]

jseng1 said :
"The point of being non symmetrical is to find the ideal shape for the opening side and also for the closing side, The requirements of each is different. The opening ramp cam be more abrupt as long as you don’t overstress the rocker arm and other cam train components. Changing the opening ramp changes the entire opening side cam profile along with it. The closing side needs a more gentle ramp to bring the valve down softly to prevent valve bounce. Bounce occurs at high RPM and if its too severe then the opening intake valve can tangle with the closing exhaust valve resulting in a damaged head. With too much bounce the exhaust gases will contaminate the intake charge."

Without testing the above is so much speculation. It looks good on paper but that is no guarantee that it will work well installed in an engine. The comment about valve bounce is also misleading. Valve bounce can occur at engine speeds not necessarily high, and are occasioned by a clash of valve train harmonics, of which the cam profile is but one of six main sources of harmonic disruption.

The opening ramp is (or should be) there in order that initial tappet clearance may be taken up so that the valve train is loaded ready to assume the initial lift off of the valve, and ideally this in a properly warmed up engine with appropriate tappet settings, will occur at the knee bend of the velocity curve, at approx. -8 degrees on the second graph. Obviously a cold engine first started will have a different tappet clearance than when at normal running temperature, so during this warm up period the point at which the valve train will become loaded will shift along the ramp somewhat.
On valve closing the ramp plays little or no part in preventing valve bounce, the rate at which the valve is closing is determined by the closing flank of the profile, and it is possible to produce a valve lift design with little or no closing ramp, certainly not of the type indicated on the graph

Is it co-incidence perhaps, that this topic has returned for a second time after Comnoz mentioned in his new engine build that he was using a non symetrical camshaft of his own design ?

 

[Brooking 850]

Jim, I have two of your cams, a JS2 version one and a JS2 version two.
The version one is still in my race bike and not sure how long before I get to test version two.
Has anyone tested your new cams ( ill call them version three) or done any comparisons between versions 1,2 & 3 perhaps on a dyno?
Regards Mike

 

[acotrel]

Are we supposed to buy these cams without them having been tested in a race bike and speculate that they might be better than what has gone before ? Anything can be made to work as long as it is half-reasonable, but getting the best is a different story - race-proven is a much better incentive to purchase, than theory. One thing which makes me wonder are the valve timings. With 2 into 1 exhaust systems, advancing a standard cam can give more torque, however if the valve opening points are earlier, the closing points might be able to be moved back to their original positions, to provide better cylinder-filling. So what type of exhaust system is used during cam development is important. I would think that most race bikes these days use 2 into1 exhaust systems and most road bikes use separate pipes. Which one does the new cam suit ?

 

[jseng1]

Mike (Brooking 850) - The 1st version of the JS2 was pretty much identical to the PW3. The 2nd “smoothramp” version borrowed on HDXR750 cam technology with its more gradual closing ramps and cured the high stress valve bounce problem of the PW3. The 3rd “asymmetrical version has a reduced intake ramp length compared to the “smoothramp” but overall performance will be about the same. If I were you I would put the “smoothramp” version in your racebike first chance you get and leave it in there..

Snotzo and Actrol - The JS asymmetrical cams have more gradual closing ramps than opening ramps. We all know that the Harley XR 750 cam puts out tons of HP and we are all familiar with the PW3 cam and its limitations. I can design ramps anywhere between those two extremes and know what to expect. The 1st version JS2/PW3 cam dynoed at 78 HP (850cc) and the JS2 smoothramp dynoed at 85HP (920cc). The JS2 asymmetrical cam profile falls inbetween those two cams as shown in the diagram below. The HP output of the JS2 asymmetrical cam will be about the same as either but the advantage is reduced strain on the valve train compared to the PW3 and other Norton cams.

Snotzo – When I’m talking about the “ramp” I’m not just talking about the tail end that takes up tappet clearance. I’m talking about the high stress swooped section from 0 lift to appox .1” lift. This is the area that controls valve bounce, cam flex and slows down the valve before it slams down on the seat. Note the extreme difference between the PW3 (bad bounce) and the HDXR (no bounce). The HDXR profile in the image was corrected for Norton geometry.

I can’t explain all the race/street bike and spintron development that went into these cam designs. I’ll just say that its endless. The JS cams are all over the world now. My cam designing began about 2 years ago and resulted with smooth ramps for the JS2&3 race cams. I also started looking at asymmetrical profiles and their advantages.

June 30 2018 I posted results of my asymmetrical cam design here:

https://www.accessnorton.com/NortonCommando/cam-designing.25499/#post-379626

see post #12

That post shows one of the asymmetrical cams that I am currently making (JS2). The 1st batch was just delivered and that is why I am making the announcement. They will be available in 4 versions from stock street to full race.

(edited)

For your convenience I have reposted my June 30 2018 post below.

*******************************************************************************************************************************
Here's an example of what the JA software can do for a PW3 cam - Smoothing out the closing ramp to avoid valve bounce while shortening up the opening ramp. You can see that the velocity (black) and jerk (blue) curves are higher on the opening side but that is usually acceptable with modern cam designs.

You just have to be sure the cam grinder knows what he's doing and doesn't mix up the opening and closing sides (tell him the cam turns counterclockwise as indicated on lower right side).

The input values (lower left area) for the ramp lift and ramp vel (velocity) are different for opening and closing making this an asymmetrical profile cam lobe. Note the shorter left side opening ramp (green) compared to the closing right side.

 

[Brooking 850]

thanks Jim appreciate the effort
Regards Mike

 

[lcrken]

That post shows one of the cams that I am currently making and as far as I know these are the first asymmetrical Norton cam designs mentioned and they predate any other asymmetrical (nonsymmetrical) Norton cam. The 1st batch was just delivered and that is why I am making the announcement. They are available in 4 versions from stock street to full race.

Don't take this wrong, Jim. I'm impressed with all the work you've put into looking for ways to improve Norton valve trains, and I hope you continue. This is not a criticism, just some historical info. Yours is not the first Asymmetrical Norton cam design. Axtell developed an asymmetrical grind for Nortons that he called the Allegro, which had different opening and closing profiles, somewhere back in the '70s, as I recall. I never had the chance to check one out, but I know he used them in some of Ron Wood's engines. I think that was only after Ron went to the short stroke engines. There might have been other users, but he's the only one I know of.

Ken

 

[jseng1]

Sorry Ken - As I said in my post "as far as I know". I never owned an "Allegro" cam and wasn't aware that it was asymmetrical. Now I've been educated.

Anyone who knows the history of Norton race bikes knows about the great work C.R. Axtell did and I'm not surprised by that he was the first.

Please post an image of the Allegro profile if you can.

BTW I remembered something in the middle of the night and dug up some data this morning. Jim Door at Megacycle sent me some cam data of an improved PW3 profile and yes its asymmetrical. So I'm editing my earlier post because this has been done before more than once. See the Megacycle ramps compared to the original PW3 below.

 

[Snotzo]

JS
two years designing cams and you know so much ?

I've been involved in this work for nearly half my life and I learn something new most every day, and one thing I came to understand a long while back is that no one can 'learn' how to successfully design cams in two years !

The emphasis here is on the word 'successfully'.

I am familiar with John Andrews software, having used examples some years back when he made versions available for test from his web site. The software may be very different now, but back then the versions I tested did not contain any provision whatever for adding the complexities of the pushrod valve train into the computation.

The spintron testing you claim has gone into these designs would be interesting to see, because I know of no Spintron equipment that is fully instrumented to enable meaningful results to be obtained for either a single or a twin cylinder engine, and the device you used whereby you motored an engine to make a dubious estimate of cam wear is not and never will be a Spintron in the form that was then used.

IMHO your efforts would be more to your credit had you first engaged in some extensive testing to confirm the soundness of your designs, and then follow by announcing them on your web site rather than use this forum to promote untried and untested products.