About time for the spintron

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I did some more testing with the new conical springs today.

So far I have run them with the stock cam at 1.380 installed height and they had perfect control over 7500 rpm

I tested them at 1.360 installed height with the Webcam 12 and 12a grinds, they were perfect until over 8000 rpm where I began to see a little bounce. No spring separation was evident through 8500 rpm.

Here is some video of testing them with the 86C grind cam. I would say the 86C grind is nearing the limit of the springs although they would be fine for street use.

Still no audio -the new sound card I installed to use as a scope input has disabled the audio.
The video starts out at 6500 rpm -no bounce
After the pause it goes to 7200 rpm. There is a small amount of bounce evident but no spring separation.
At 8200 rpm there is some bounce and some spring rotation indicating separation.

Then there is a spring view at 7200 rpm -then 8000 rpm with some spring rotation -then 9000 rpm with spring separation and rotation.

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

I have some more double coil springs on the way for high rpm and racing with larger cams. I want to see how they compare to Sir Eddie's Honda springs and I will be ordering up some retainers to fit the better of the two. Jim
 
Hi Jim
Enjoying your work.
With this last run there doesn't appear to be as much valve stem flex is it because of the mushroom adjusters?
You can see now why in the old days they had so much trouble with valve spring failures, the inertia of the spring coils and harmonics etc.

Regards
Burgs
 
Jim,

What about the 3 piece valve springs (outer coil, flat damper, inner coil)?

About time for the spintron
 
johntickle said:
Jim,

What about the 3 piece valve springs (outer coil, flat damper, inner coil)?
Click to expand...

They work OK. It is a dual spring with a flat friction damper. They are a bit heavy and create heat like any friction damped spring. Jim
 
Burgs said:
Hi Jim
Enjoying your work.
With this last run there doesn't appear to be as much valve stem flex is it because of the mushroom adjusters?
You can see now why in the old days they had so much trouble with valve spring failures, the inertia of the spring coils and harmonics etc.

Regards
Burgs
Click to expand...

I suspect the reduced flex is due to the reduced spring pressure and less aggressive cam more than anything. I was using the same adjusters with the larger springs and bigger cam and they flexed a lot.
 
Hi Jim,
Really enjoying the spintron research, fascinating stuff.
One question (which may have been answered somewhere in the thread) - I understand the purpose of getting up and over 8,000RPM in terms of power, but what is the diminishing return in respect to piston speed?
I was under the impression that over 7,500RPM, the Commando stroke struggles to yield any useful gain?

Thanks,
Mick
 
ML said:
Hi Jim,
Really enjoying the spintron research, fascinating stuff.
One question (which may have been answered somewhere in the thread) - I understand the purpose of getting up and over 8,000RPM in terms of power, but what is the diminishing return in respect to piston speed?
I was under the impression that over 7,500RPM, the Commando stroke struggles to yield any useful gain?

Thanks,
Mick
Click to expand...

Think Short Stroke........

Jim points that out at the start of the thread, the work has a specific purpose as well as general applicability.
 
Jim,
Would valve seat geometry influence valve bounce when pushing it to the extreme RPM pursuit limits? I am thinking the contact area from the sealing surface between the seat and valve. Would a wider land or contact surface act as a cushioning effect? Gas/Air flow would possibly change to a negative net result.
Cheers,
Thomas
CNN
 
CanukNortonNut said:
Jim,
Would valve seat geometry influence valve bounce when pushing it to the extreme RPM pursuit limits? I am thinking the contact area from the sealing surface between the seat and valve. Would a wider land or contact surface act as a cushioning effect? Gas/Air flow would possibly change to a negative net result.
Cheers,
Thomas
CNN
Click to expand...

I would think a wider seat seat would be a poor trade even if it did help the bounce. Both because of the affect on airfow and the poor sealing from excess width. Jim
 
While Jim is busy withadditions/adjustments to his spintron, the following may be of interest to those having Maney angines and/or Maney camshafts.

Some time back I had opportunity to measure up a 750 Maney engine. With an 89 mm stroke, this would not normally be expected to exceed 7000 rpm even in racing mode.

I looked at the cams and valve train at an extreme engine speed of 8500 rpm, and my findings were extremely interesting.
Taking the intake side first, the valve was a 42 mm diameter steel item weighing 66 grams. The pushrods were steel, and the valve springs were double, parallel wound with a free fit inner, at installed heights of 1.27" for the outer, 1.21" for the inner.
At this elevated engine speed the springs held the valve train together with no separation or bounce.
I should add here that substituting the dual springs with Jim's conical item, the results were identical.

The exhaust side was where the interest really occurred. Here with a steel valve of 33 mm diameter weighing 62 grams, steel pushrods, and the same double valve springs, but adjusted to give an outer installed length of 1.18", and an inner installed length of 1.12", at the same engine speed of 8500 rpm, the simulation showed very severe separation on the closing flank with equally severe bounce.
Re adjusting the installed heights to the same values as for the intake and all separation and bounce was gone. The performance of both exhaust and intake became virtually identical.

Now who in their right mind would want to rev this long stroke engine to 8500 rpm ? No doubt some one somewhere will have tried.
This exercise is intended to show, not that it can be done, but what the result might be when the spring seated pressure is increased in an attempt to better control a valve train that is already of the edge of stability.

I stress this is only applicable to the engine and components I have measured. With a different engine the results may be completely different .
Again, I do not know whether the springs in the engine were those that Steve Maney supplies.

The above described behaviour and much more will be revealed when Jim increases the scope of measurement of his spintron.
Incidentally Jim, there is a peculiar feature just prior to the closing ramp of the WC86C exhaust lobe that you might have an opportunity to examine sometime.
 
Sir Eddies rocket used to have lighter BSA lifters in it. If heavy stock type flat lifters are being considered - why?
 
jseng1 said:
Sir Eddies rocket used to have lighter BSA lifters in it. If heavy stock type flat lifters are being considered - why?
Click to expand...


" If heavy stock type flat lifters are being considered"

What would give you that impression?
 
comnoz said:
jseng1 said:
Sir Eddies rocket used to have lighter BSA lifters in it. If heavy stock type flat lifters are being considered - why?
Click to expand...


" If heavy stock type flat lifters are being considered"

What would give you that impression?
Click to expand...

Oops - I was jumping to conclusions
 
Snotzo said:
Taking the intake side first, the valve was a 42 mm diameter steel item weighing 66 grams. The pushrods were steel, and the valve springs were double, parallel wound with a free fit inner, at installed heights of 1.27" for the outer, 1.21" for the inner.
At this elevated engine speed the springs held the valve train together with no separation or bounce.

The exhaust side was where the interest really occurred. Here with a steel valve of 33 mm diameter weighing 62 grams, steel pushrods, and the same double valve springs, but adjusted to give an outer installed length of 1.18", and an inner installed length of 1.12", at the same engine speed of 8500 rpm, the simulation showed very severe separation on the closing flank with equally severe bounce.
Re adjusting the installed heights to the same values as for the intake and all separation and bounce was gone. The performance of both exhaust and intake became virtually identical.
Click to expand...

Why would one shim the lighter exhaust valves thighter then the heavier intake valves in the first place :?: and more interesting what corresponding pressure figures are involved in specified installed lengths :?:
 
nortonspeed said:
Why would one shim the lighter exhaust valves thighter then the heavier intake valves in the first place :?: and more interesting what corresponding pressure figures are involved in specified installed lengths :?:
Click to expand...

I generally wouldn't agree with that practice except when a Ti intake is used but ...

-it was once pretty common practice to keep valve prints off the piston and to keep the valves from tangling when the springs had too low a spring rate. Jim
 
^^ Sounds very similar to the system Lotus had a go at years ago.
One of the features if I remember correctly was instead of any sort of throttle, the variable valve timing would have such a wide range as to control engine speed and power output - the absence of the throttle restriction giving improved volumetric efficiency.
 
I have re-learned a couple things this weekend concerning the valve bounce I have been watching. I have tried several more combinations of parts including a hairpin type spring on the intake rocker.

It is looking like JS is right in the fact that the big valve bounce on closing is more than just the bounce of the valve on the seat. It is coming from the recoil of the camshaft after each lobe passes.

That helps explain why the more flexible PW3 cam produces more bounce than the steel 86c even though the lobe profile is pretty similar. The cast cam produces as much bounce at 6200 as the steel cam produces at 7500.

The duration of that bounce at 7000 rpm with the PW3 cam is close to 50 degrees of crankshaft revolution. Since this bounce happens during the compression stroke -it is bound to have an affect on power.

I used a VR sensor in the center of the cam and watched the output on a dual trace scope. As a marker on the second trace I monitored the digital "off-on" output of the laser sensor. The spring and rebound of the cam was right in step with the bounce, making it clear that it is the recoil of the cam that is opening the valve -causing the first big bounce after the valve seats.

Now I know why using a center support on the cam in my racebike made an improvement in power.

Here is a video of the valve to rocker at 8500 RPM with the 86c cam and a hairpin spring on the rocker arm. You can see, the rocker does push the valve back open after closing. You can see the loop of the spring under the rocker.
You can also see the continued flexing of the cam after the bounce. I could also see that with the sensor I have in the center of the cam.

[video]https://youtu.be/r5KYg-Zvido[/video]

Here is a shot of the whole valve assembly at 8500 rpm with the hairpin spring on the rocker.

[video]https://youtu.be/IzDsBc7gkwU[/video]
 
Thanks for the better vid of whats happening at the rocker arm tip.

Webcam says that the 86C cam is a combat cam. Is this right?
 
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