About time for the spintron

Snotzo,

Ever more fascinating stuff!

Can you tell us a little more about the RX cam, e.g., maximum lobe lift, duration at a lobe lift of 1 mm or 0.050", etc.

Also, when employing the Ti valve, what weight did you use for the Ti valve and what weight are you using for the simulations with the 3 mm OS steel valve in Comnoz' Dunstall spintron head?

If the 3 mm OS steel valve were substituted for the Ti valve in your Norris RX simulation, at what rpm would separation/bounce occur?

Thank you.

The stock valve is 66 grams.
The 3mm over valve is 68.8 grams.

WZ507
the Norris RX cam that I measured was not a new item. Lift measured at the cam was 0.375 inch. At 0.040 thou. lift, duration was 295 degrees.

The acelleration curve is shown plotted for comparison with the PW3. Notice two small reversals on the opening and closing side of the RX.

Having reached peak acelleration on opening, the rate is slowing as the cam moves towards peak lift, but suddenly over a short degree span, the acelleration speeds up - then slows again. This process is repeated on the closing side.




I note the colors are indistinct, and possibly hard to see for some people. Hopefully the description given will help identification when such is the case.

I haven't figured out how to post two pictures on the same post, so a comparison of the jerk traces will have to come separately.

The Norris RX and PW3 jerk curves compared.



Perhaps now the reason for the RX acelleration reversals shown in the previous post become clear.

The difference is considerable, but as I have mentioned in earlier posts, the PW3 was not intended to be a high engine speed cam, and is the cam of choice for many Commando owners

Dramatic difference of accelerations. What sort of Norton twin was spun high enough to out run the PW3 benefit and create a market & expense of designing and selling the RX cam? Would one expect more power from PW3 before too hi rpm cut its performance or would RX be expected to match PW3 below redline but carry on somewhat higher?

hobot said:

Dramatic difference of accelerations. What sort of Norton twin was spun high enough to out run the PW3 benefit and create a market & expense of designing and selling the RX cam? Would one expect more power from PW3 before too hi rpm cut its performance or would RX be expected to match PW3 below redline but carry on somewhat higher?

Click to expand...

The way I read it Steve, any Norton with a stroke of 80.4 or less has the potential get the PW3 into the rpm area where it becomes the limiting factor in the valve train.

Conversely, an 89mm Norton should work fine with the PW3.

Now you know why I am following with such interest.

Aw shoot SteveA we are all watching at edge of our valve seats on whats possible vs whats needed to thrill us enough. Much as I am disbelieved on INSANE corner load capacity with Peels ANTI-l logic Tri-links I want to power Peel up enough to spank the 200 hp wheelie & tire slip prone moderns up to 160 or so but know she will have to spin up dangerously with D+ cam on long strokes. I wonder if bigger valves with trimmed down lobes might help. So far highest speeds at Barbers is about 150 mph no matter how much faster the down force cars or puterized cycles can go in a bee line it does not help them handle sharpened turning. Peel and me are outlaws not race rule followers. Drouin instructions say limit rpm to 6200 but Tom tested to 8000 and recently gone quick dead John Mead told me he got away fine with Drouin on 11 CR and 4S cam in a Combat. He also said his father was killed in Mt Twisties when the Lake Injector slide stuck open on ordinary Combat. Death of engine and pilot is a constant state of mind for me discussing anything cycle related.

A favorite T-shirt of mine says, How Much Can I Get Away With And Still Go to Heaven...

Snotzo said:

WZ507
the Norris RX cam that I measured was not a new item. Lift measured at the cam was 0.375 inch. At 0.040 thou. lift, duration was 295 degrees.

The acelleration curve is shown plotted for comparison with the PW3. Notice two small reversals on the opening and closing side of the RX.

Having reached peak acelleration on opening, the rate is slowing as the cam moves towards peak lift, but suddenly over a short degree span, the acelleration speeds up - then slows again. This process is repeated on the closing side.

I note the colors are indistinct, and possibly hard to see for some people. Hopefully the description given will help identification when such is the case.

I haven't figured out how to post two pictures on the same post, so a comparison of the jerk traces will have to come separately.

Click to expand...

Snotzo,

Thank you for the info on the nature of the RX lobe profile. Since you are clearly an expert in valve train motion, components and cam design, I have a few more questions about the RX design. As you point out, the positive acceleration curve for the RX consists of the initial rise (nudging the system into motion) to a major peak followed by a minor peak before going negative. In the realm of cam archeology, this is the feature I'm simply curious about, and I suspect you know exactly why it was designed like this. I'm familiar with the common acceleration curves that consist of a tiny positive peak, where the valve train is nudged into action on the constant velocity ramp, followed by a single major positive peak before falling away to go negative. So I want to know what gives rise to the RX's double acceleration peak.

Assuming the cam was designed circa 1965-1970, the majority of common calculations were being carried out on a slide rule (at least in the lab I worked in), and perhaps cam design is no exception to this process. In other words, a cam design that may take 5 minutes to do nowadays, may have taken a day or multiple days to create back then, and may not have benefited from the myriad smoothing functions, available at the push of a button today, to blend the ramp to the flank.

In light of the foregoing, are the major/minor positive acceleration peaks of the RX lobe the result of the design process of that time period (1970), i.e., perhaps 2 different equations or algorithms meeting/joining in this region, or was the design specifically made to create exactly this specific bimodal acceleration peak?

The last question relates to the plot of acceleration and jerk you posted previously for the RX, where no Y axis labels were included. Could you divulge the maximum positive and negative accelerations for the RX and PW3 cams (mm/cam deg^2)? Thank you.

Like this.

WZ507 said

" Assuming the cam was designed circa 1965-1970, the majority of common calculations were being carried out on a slide rule (at least in the lab I worked in), and perhaps cam design is no exception to this process. In other words, a cam design that may take 5 minutes to do nowadays, may have taken a day or multiple days to create back then, and may not have benefited from the myriad smoothing functions, available at the push of a button today, to blend the ramp to the flank. "

Peter Williams told me personnaly that he used a computer at a university to help design the PW 3. But he went on to say they were really doing very new stuff for them and indeed curve smoothing programmes etc would likly not have been developed at that early stage (or available to them perhaps?).

WZ507

The features of the RX design that interest you may well go back to the 1960-70 period if JS is correct in his understanding that the design came from Offenhauser.

The design draughtsman at that time was Leo Goossen, an extremely gifted and innovative man. While undoubtedly a slide rule played some part in assisting with the calculations, inevitably long hand calculations would also have been necessary in order to gain the accuracy required.

I am of the opinion that the max/min acceleration feature was no accident, but designed deliberately.
Certainly such a feature was understood by the designers of the period, and Don Hubbard's 'Cam Reference Handbook' contains examples of such design, although not in the more acute form as found in the RX profile.
The purpose of the feature was to create a short period of constant velocity.

Re the acceleration rates of the RX and the PW3, the following are the max/min values in mm/degree^2.

PW3 opening 0.01269, closing 0.01282, negative -0.00574
RX opening 0.00788, closing 0.00839, negative -0.00507

Interestingly, the acceleration rates on the closing flanks are slightly greater than on the opening flanks, more so with the RX profile, the PW3 to all intents and purposes being a symetrical design.

Snotzo said:

WZ507
The purpose of the feature was to create a short period of constant velocity.

Click to expand...

Snotzo,

Thank you for the insight and information regarding the RX design - you're a rich and vital asset as we hunt through the field of cam archaeology. Your statement regarding the "short period of constant velocity" is difficult for me to understand because I thought acceleration had to go to zero for constant velocity to be achieved, and the plot of acceleration does not show this. I'm not questioning, arguing or nit-picking your contention, just attempting to better/fully understand the rationale for the design. Perhaps a short period of "reduced velocity"?

Since creation of the RX we are now benefactors of nearly 50 years of design knowledge and remarkable tools like 4stHead design software. In light of the present cam design knowledge, would a modern day designer ever employ a bimodal acceleration peak like the RX employs, or was that an idea of that era that has now been left behind? You recently re-designed an RX lobe profile for use with a BSA lifter, and in so doing, were you faithful to the original RX bimodal acceleration peak or was it modernized to employ a single acceleration peak? Thank you.

WZ507

We seem to have jumped thread here, but as the spintron and RX cam seem to be closely associated, I will continue.

While the purpose of the feature was to provide a period of near constant velocity, in the case of the RX it was used to slow the velocity down proir to reaching it's peak.

The feature well carried out is shown in the acompanying illustration of the graphics of a Summerfield Manx Norton intake cam.
Obviously there are two periods of constant velocity, but I have only indicated the closing side feature.



The redesign of the RX for use with a radius lifter was done to include all warts and blemishes. Were I doing a re vamp for a newly manufactured camshaft, I would iron out one or two small gliches, otherwise as it stands it's still a pretty good design, and the discrepancies may well be the result of some small wear on what was a used item that I measured.

Jim,

I really hope that you summarise all of your findings in a simple way for all of the thicko's on here, namely me!

Will you be able to offer a simple table or similar showing your conclusions by engine type, desired characteristics, best cam, ie:

High comp 850, max spread of power between 3,000 and 6,000 for road use, best cam = xxx
Low comp 850, max low rpm torque for touring use, not revved over 5,000, best cam = xxx

What say you sir?

Fast Eddie said:

Jim,

I really hope that you summarise all of your findings in a simple way for all of the thicko's on here, namely me!

Will you be able to offer a simple table or similar showing your conclusions by engine type, desired characteristics, best cam, ie:

High comp 850, max spread of power between 3,000 and 6,000 for road use, best cam = xxx
Low comp 850, max low rpm torque for touring use, not revved over 5,000, best cam = xxx

What say you sir?

Click to expand...

As I get on with more testing and collecting data I will do something like that. Jim

I did more testing today using Sir Eddiy's cylinder head on the spintron.

Since the valves in Sir Eddy's head were near standard size and the stems were 6mm they were substantially lighter so I though maybe I could get by with the Honda springs that were on it when I got it.
This is with the custom Webcam and proflled lifters that had run to 10,500 with the big valve head and the IRL springs.

[video]https://youtu.be/XtQZ9uvL7ys[/video]

After hitting valve float with the Honda springs I noticed a large increase in exhaust valve clearance. I knew what that meant. A lost Stelite pad. {*(%^&&*]



After profiling another lifter 10,200 rpm was obtained with around 130 lbs seat pressure.

Next problem. The ultra-lightweight Ti valve caps didn't like the increase in spring pressure. Note the collets have pulled through about .035 on the exhaust valve.



Now what I need is some 8 or 10 degree retainers or some heavier spring caps. Kibblewhite-help. Jim

All testing within this RPM range will bring out the best that Old Murphy has to offer.
This is some serious land speed barriers that you are approaching.
Chuck Yeager would say "Never wait for trouble"
Keep on keepin on.... Jim
Cheers,
Thomas
CNN

comnoz said:

Click to expand...

Ouchy! What does the lobe look like?

In your video, it looks like there's at least four different sets of tests. What changed during each of those (or did I miss that in your post)? Thanks for all the time you've dedicated to this, and especially for posting it for all to see!

Nathan

Nater_Potater said:

comnoz said:

Click to expand...

Ouchy! What does the lobe look like?

In your video, it looks like there's at least four different sets of tests. What changed during each of those (or did I miss that in your post)? Thanks for all the time you've dedicated to this, and especially for posting it for all to see!

Nathan

Click to expand...

There is audio with the video describing the changes

The first segment was 8000 rpm with the Honda springs installed at 105 lbs seat pressure.
Second was 9000 rpm with Honda springs.
Third was 10,000 rpm with Honda springs.

Fourth was 9000 rpm after shimming the Honda spring to near coil bind -around 120 lbs seat pressure
Fifth was 10,000 rpm, this is where valve float destroyed the lifter

Sixth was 9000 with IRL springs installed -around 130 lbs seat pressure
Seventh was 10,200 rpm with the IRL springs -success!!!

The new Webcam was damaged when the Stelite broke. Since the runtime to record the video is only about three seconds the damage was not too severe and I was able to continue using the same cam for the spintron testing but it is no longer usable in a real motor . Expensive test...

comnoz said:

There is audio with the video describing the changes

Click to expand...

Hm-m, audio; what a novel concept. Is that like one of those phonograph thingys? I never thought to turn up the volume. Thanks for the breakdown.