New product release - smooth ramp PW3/JS2 cam

OK - the cats out of the bag.

I have given the PW3 cam profile a smoother ramp to make things easier on the valve train and avoid bounce. It uses lightweight radiused BSA lifters (less wear than flat lifters). It comes as a complete kit with lifter blocks etc. This is a special order cam.

Designing the new profile was a tremendous amount of work.

The ramp stress (jerk) of the PW3 has been dramatically reduced by appox half as shown in the chart below.

Chart for the new smooth ramp JS2/PW3


The ramps of the new JS2 smooth ramp cam are smoother than any other Norton cam. Nothing else even comes close (not including profiled lifters).

See graph of ramp comparisons below.

Are those drawings raw polylines, and is the actual result a smoother structured polyline?

Your smooth ramp profile line appears to be relatively "stepped" rather than relatively smooth as the original PW3 line is.

grandpaul said:

Are those drawings raw polylines, and is the actual result a smoother structured polyline?

Your smooth ramp profile line appears to be relatively "stepped" rather than relatively smooth as the original PW3 line is.

Click to expand...

The drawing in my 1st post above has been updated to show that the profile is not stepped. I have so many cam profiles to draw that sometimes I save time by drawing straight lines between every 10 degrees instead of every degree. If I want to see a more accurate image I enter in the lift for each deg of duration. The grinder gets the lift data in each degree of course - and to an accuracy of 7 digits.

Here is the finished product . This is the popular PW3 profile - now with a smoother ramp for lighter lifters - named "JS2 smooth ramp". I came up with this cam because people were asking for it - to reduce the valve bounce and jerk stress of their favorite cam which was originally designed by the great Peter Williams (thank you Peter).

jseng1 said:

The drawing in my 1st post above has been updated to show that the profile is not stepped. I have so many cam profiles to draw that sometimes I save time by drawing straight lines between every 10 degrees instead of every degree. If I want to see a more accurate image I enter in the lift for each deg of duration. The grinder gets the lift data in each degree of course - and to an accuracy of 7 digits.

Click to expand...

The reason I asked is that as long as the "real world" performance of the cam is in fact smooth, all you have to do is "pedit" (polyling edit) the line on the drawing, and the CAD program should smooth it for you, retaining the track of the line at the data points. This will not be "faking" results, it is only smoothing the track of the datum.

grandpaul said:

jseng1 said:

The drawing in my 1st post above has been updated to show that the profile is not stepped. I have so many cam profiles to draw that sometimes I save time by drawing straight lines between every 10 degrees instead of every degree. If I want to see a more accurate image I enter in the lift for each deg of duration. The grinder gets the lift data in each degree of course - and to an accuracy of 7 digits.

Click to expand...

The reason I asked is that as long as the "real world" performance of the cam is in fact smooth, all you have to do is "pedit" (polyling edit) the line on the drawing, and the CAD program should smooth it for you, retaining the track of the line at the data points. This will not be "faking" results, it is only smoothing the track of the datum.

Click to expand...

Yes - you're talking about the "spline" option. I used that a lot when I was designing saxophone bells & necks etc. The "cam smoothing passes" in the cam software work in a similar way.

Very nice results for a trick cam. Maybe I'll sell my Megacycle 560 that's sitting on the shelf with my VR880 parts, and replace it with one of your. Would standard radiused lifters work?

grandpaul said:

Very nice results for a trick cam. Maybe I'll sell my Megacycle 560 that's sitting on the shelf with my VR880 parts, and replace it with one of your. Would standard radiused lifters work?

Click to expand...

Standard stock flat lifters are usually radiused to 3" and that's too big because the JS 0, 1 and 2 cams use 1-1/8" radiused lifters. You might be able to radius a stock lifter to that dimension. If you send me a stock lifter I'll look at it and see if it's possible and if so I'll give it a try (the lifter may need a step just below the stellite). The early stock lifters with the chamfered corners would also work for this experiment. I no longer have any stock flat lifters.

Send it to:

Jim Schmidt
4480 N. Academy
Sanger, CA 93657

jseng1 said:

Standard stock flat lifters are usually radiused to 3" and that's too big because the JS 0, 1 and 2 cams use 1-1/8" radiused lifters. You might be able to radius a stock lifter to that dimension. If you send me a stock lifter I'll look at it and see if it's possible and if so I'll give it a try (the lifter may need a step just below the stellite). The early stock lifters with the chamfered corners would also work for this experiment. I no longer have any stock flat lifters.

Click to expand...

I might have one good stock lifter left, I know I have a couple of trashed ones. I'll dig it out and send it to you.

JS
your graph depicting the ramp difference between your revised version of the PW3 profile and the actual PW3 needs some further explanation.
You do not indicate the method used to measure the ramps, and if a translating follower is used, is it of the type associated with the cam in normal use, such as a flat foot follower in the case of the PW3, and the BSA radius follower as in your modified version?

I would assume this is the case, because if it is not then the comparison would be pointless. However, there remains a further problem, the notation of the ramps is either unintentionally transposed, or the modified ramp is harsher than the PW3 original.

Or perhaps there is some other explanation that I am missing?

Snotzo said:

... You do not indicate ... if a translating follower is used, is it of the type associated with the cam in normal use, such as a flat foot follower in the case of the PW3, and the BSA radius follower as in your modified version?

Click to expand...

iN THE ORIGINAL POST:

jseng1 said:

It uses lightweight radiused BSA lifters (less wear than flat lifters). It comes as a complete kit with lifter blocks etc. This is a special order cam.

Click to expand...

Snotzo said:

JS .... is it of the type associated with the cam in normal use, such as a flat foot follower in the case of the PW3, and the BSA radius follower as in your modified version?

I would assume this is the case, because if it is not then the comparison would be pointless....

Click to expand...

Snotzo
I'm pretty sure I showed this profile to you awhile back before it was finalized and produced. I think you called it an "incredibly smooth ramp" or something to that effect. It is indeed a representation of the PW3 with flat lifters (blue) compared to the New JS2 smooth ramp with 1-1/8" radiused lifters (black). Shown again below complete for comparison (and pedit splined for Grandpaul).

jseng1 said:

The grinder gets the lift data in each degree of course - and to an accuracy of 7 digits.

Click to expand...

Can your grinder actually grind accurately to 7 digits, we ask innocently....

Rohan said:

jseng1 said:

The grinder gets the lift data in each degree of course - and to an accuracy of 7 digits.

Click to expand...

Can your grinder actually grind accurately to 7 digits, we ask innocently....

Click to expand...

No, of course not. But the cam software carries it that far out for mathematical reasons that were explained to me and promptly forgotten.

Probably so it doesn't round it up or down, possibly to the next whole number - which may not be as intended.

"The drawing in my 1st post above has been updated to show that the profile is not stepped. I have so many cam profiles to draw that sometimes I save time by drawing straight lines between every 10 degrees instead of every degree. If I want to see a more accurate image I enter in the lift for each deg of duration. The grinder gets the lift data in each degree of course - and to an accuracy of 7 digits." quote

Re "sometimes I save time by drawing straight lines between every 10 degrees instead of every degree"



Thank god PW and others saw sense and used a cam grinder, not like a certain full race 750/Domi cam I once had -it had flats ground onto it EVERY 5 degrees :!: :shock:

Bernhard said:

Thank god PW and others saw sense and used a cam grinder, not like a certain full race 750/Domi cam I once had -it had flats ground onto it EVERY 5 degrees

Click to expand...

No problem, just chuck a stone into a hand drill and smooth them right up! 5 minute job.

Adds a new dimension to the term 'polydyne' !?!

Wonder if anyone tried them like that. ?
Be tough on the lifters, but with a good oil bath they'd last a race ?

grandpaul
I fear you missed the point of my question in my earlier post.
The reason for my query is as I then stated - the ramp is harsh, I could have said agressive, when compared to the PW3.
For the lift at the 90 degree marker to be approx. 3 times more than the PW3, how else would you describe it? To reach the same lift the PW3 uses approx. 20 degrees longer duration.




The graph here is an overlay of a Summerfield Manx Norton ramp on the PW3. The base line is much longer, but if you shorten it to a comparable length you will see that the JS2/PW3 ramp compares very closely to the Manx. Anyone who has had dealings with a Manx DOHC engine will understand how very rigid the valve train mechanism is as compared to a pushrod, and with the Summerfield cam, the opening of the valve may be likened to a blow from a hammer, such is the severity and agressive rate of opening.
If the same is tried with a pushrod valve train the end result is likely to be rather less than satisfactory, not at low engine speeds maybe, but in the region where a PW3 works well .

Smoothness with respect to valve lift design means the gradual and smooth progress of the data within a design where all derivatives are likewise, and not disruptive of the smooth continuation of the design. A very agressive design can (and should) be smooth in order to give maximum benefit without unwanted side issues. Conversely, a seemingly gentle ramp can be seriously rough as far as the smooth progress of the data within the design is concerned. It is important to correctly understand what smoothness is describing in this instance.

Snotzo said:

grandpaul, I fear you missed the point of my question in my earlier post.

Click to expand...

Quite likely.

I have been discussing a CAD drawing issue, not a mechanical engineering concept as relates to cam design and operation.

Snotzo said:

...the ramp is harsh, I could have said agressive, when compared to the PW3.
For the lift at the 90 degree marker to be approx. 3 times more than the PW3, how else would you describe it? ....
Snotzo

Click to expand...

You need to take into account that the ramp of the new JS2 smooth ramp starts earlier than the PW3.

If you move the PW3 ramp sideways for viewing convenience so the beginning of the PW3 ramp matches up with the JS2 smooth ramp you can see that the JS2 has LESS lift over the same amount of duration and is LESS aggressive than the PW3. The image below makes that clear. Note the short vertical line indicating the beginnings of the ramps (the opening and closing ramps are mirror images).



Also - I'd very much like to see the complete graph of the Manx cam with the degrees and lift numbers visible on the bottom and sides.