About time for the spintron

Thanks for trying to set me straighter Dances but I know an ignored-over looked factor > that once engine prepped so not to miss a beat over 10 grand > stuff outside the crank cases then fails. I now think if I was smarter I'd of just replaced Peels cam, oil pump, tensioned, chain and cogs to stick on the Drouin and be having a blast by now. Dances you had a 9,000 tolerant Commando engine like my P!!, how'd they do that & why don't we hear of that anymore? After I cleared the molten-slag form alternator rotor/stator clashing it worked fine and eventually sold off at a rally to keep their lights bright at low rpms. I ran Peel 2000 more miles w/o a cam tensioner, cracked loose oil pump, 1/8" DS/1/16"TS bend crank and missing RH exhaust lobe for another 2000 miles with huge winter screen up to 110 mph but lost its easy 120 mph commutes in opens & whiplashing power response and 1098 Ducati came on scene so decided on bigger engine - which should of been done half a decade ago but for other major hits to my home and life survival. I'd recommend everything possible be cryo tempered and dry friction coats over micro polished surfaces. New saw chains arrived so them plus Trixie's 2S cam and 2 head studs for comnoz to test are off to freezer soon. Next Peel will re-use the 15 yr old technology valve kit Kenny Dreer sold for Combat head which Canaga examined after the over rev event to find no issues but bigger squish bands and new bolt hole to slap on 920 block. The mech drive tach can only register 10k before needle bounces off peg stop to fast to see...

hobot said:

why don't we hear of that anymore?

Click to expand...

Dances with Shrapnel said:

There are other challenges that I will not expound on here.

Click to expand...

So here we go.

Last time the 500 was running the timing pinion key on the crank sheared and the pinion split. Some carnage to the top end. I attribute the failure in part due to the exceptionally high valve spring forces as well as the wonky things that a 180 degree cam/firing timing subjects the cam drive to. A new version will be rising from the ashes including billet crank with OS main journals and a Full Auto head. Really nothing off-the-shelf" to rebuild these things with other than valve covers and valve cover nuts.

The take away is a 180 degree crank was not necessary and caused more problems than it was perceived to solve.

The illustration shows the mathematical model for a push rod valve train in 4StHead. As Dances so rightly observed, Prof Blair treated all components as springs.
The replacement of an alloy pushrod with a steel item is not always a good move, and will depend on the compatibility of the pushrod with other items in the valve train, most especially the valve springs, the cam being used, and the desired engine speed.

Hobot, you will note in the illustration there is a spring sign under the cam. The deflection of this item is calculated based on the force applied, the stiffness of the shaft, the spacing of the bearings, and the location of a lobe relative to the bearing. The stifness of the shaft in turn is determined from the material used, outside diameter of the shaft, and the diameterof any hole thru the shaft. In the case of the Norton camshafts, the cast iron items are not as stiff as a steel one of the same dimensions.

Snotzo - thanks for the schematic of the simulation set-up.

I'm both amazed and dumbfounded at the thoroughness of the model! As Dances and Ken noted, it is an incredibly complete model. Whoever said "a picture is worth a 1000 words" grossly understated the value of a picture!

Although the model does show a plethora of springs it should be noted that for every spring there is also a dashpot (springs and dashpots are set up in parallel), in order to address both the purely elastic nature of the system (spring) as well as any energy loss (friction, heat, etc) occurring in the system (dashpot).

This forum is an unbelievable source of knowledge and teaching, and this thread in particular has been stellar in terms of conveying great information.

Here is video I shot today with a PW3 cam, stock lifters, stock pushrods, lightened rocker arms and the best race springs I have tested so far.
The springs were lifted from Sir Eddies racebike for this test. They are performance springs for a Honda with a set of Ti retainers I made up.
They are set at around 140 lbs of seat pressure.
The valve clearances were set at .004 in for this video. At .008 in. clearance the bounce was worse.

[video]https://youtu.be/L0_pud6vcuw[/video]

I ran this setup up to 9100 rpm with no serious loss of spring control -just a lot of bounce, they started to rotate slightly at this speed. Jim

Scope of wonder increases as mysteries decreasing comnoz. Wondered when Sir Eddie's kit would get a whirl. PW3's is advertised with special efforts put in to be milder on valves than other hot cams. Looks like could survive a few dyno runs just for fun. Bet ya can't stop now till temporary type Ti valves tired.

Hey Jim,
Thanks for putting dad's springs to see how they performed. You say these are the best racing springs you have tested so far???
It looks to me that the bounce is pretty severe.

Are you able to fit the asymmetrical cam out of the racer into these cases to see if the radical closing rate reduces the bounce or maybe make it worse?
Thank you very much for checking these springs out! Thoughts?

hobot said:

Scope of wonder increases as mysteries decreasing comnoz. Wondered when Sir Eddie's kit would get a whirl. PW3's is advertised with special efforts put in to be milder on valves than other hot cams. Looks like could survive a few dyno runs just for fun. Bet ya can't stop now till temporary type Ti valves tired.

Click to expand...

I have about a dozen Ti valves to play with. I will have to fit a new guide first as they are all 7mm.

I have to wonder what they did to the PW3 I have for ramps -like maybe they forgot them.....

I have also ran a webcam 86C which is a bigger cam than the PW3 and it has very little valve bounce.

I suspect much of my testing from now on will be on the 86c or a couple other Web grinds I have. They will obviously be better for high RPM use. Jim

Son of Siredward said:

Hey Jim,
Thanks for putting dad's springs to see how they performed. You say these are the best racing springs you have tested so far???
It looks to me that the bounce is pretty severe.

Are you able to fit the asymmetrical cam out of the racer into these cases to see if the radical closing rate reduces the bounce or maybe make it worse?
Thank you very much for checking these springs out! Thoughts?

Click to expand...

Yes, I do want to see what your dads cam does when combined with your springs. It is a grind I have never seen before. I will need to get the BSA followers mounted up. I'm not sure if my 3 horse motor has enough stuff to turn it up to 10,500.... Jim

comnoz said:

Son of Siredward said:

Hey Jim,
Thanks for putting dad's springs to see how they performed. You say these are the best racing springs you have tested so far???
It looks to me that the bounce is pretty severe.

Are you able to fit the asymmetrical cam out of the racer into these cases to see if the radical closing rate reduces the bounce or maybe make it worse?
Thank you very much for checking these springs out! Thoughts?

Click to expand...

Yes, I do want to see what your dads cam does when combined with your springs. It is a grind I have never seen before. I will need to get the BSA followers mounted up. I'm not sure if my 3 horse motor has enough stuff to turn it up to 10,500.... Jim

Click to expand...

Your up a little late...
So you are happy with the way the springs stay in contact with the retainer but not the bounce?

Son of Siredward said:

comnoz said:

Son of Siredward said:

Hey Jim,
Thanks for putting dad's springs to see how they performed. You say these are the best racing springs you have tested so far???
It looks to me that the bounce is pretty severe.

Are you able to fit the asymmetrical cam out of the racer into these cases to see if the radical closing rate reduces the bounce or maybe make it worse?
Thank you very much for checking these springs out! Thoughts?

Click to expand...

Yes, I do want to see what your dads cam does when combined with your springs. It is a grind I have never seen before. I will need to get the BSA followers mounted up. I'm not sure if my 3 horse motor has enough stuff to turn it up to 10,500.... Jim

Click to expand...

Your up a little late...
So you are happy with the way the springs stay in contact with the retainer but not the bounce?

Click to expand...

Yes,
Too much bounce in my opinion. I do not think any spring would stop the bounce I am seeing. Jim

The root cause of the bounce problem lies in the fact that most, if not all Commando owners have to indulge in a mix and match exercise with existing components that happen to be available at any given time. Those who are able to both design and have manufactured their own cams are very few and far between. And by design I mean actual design working from sound principles, not grinding off by hand some of the base circle. Then again it's another guessing game in trying to match a spring to work with a particular cam profile for a given purpose. It can be done for sure, but there is a huge element of luck involved in getting a good working match.
Which way to go about sorting this little problem out ?
Most would probably be inclined to select a cam that gave the timing and lift that seemed most appropriate, with a keen eye on the area under the lift curve, and then sort through the various spring suppliers catalogues to see if any spring appeared suitable. Here a short cut may be possible by referring to springs known to be used and/or recommended by others.
So you end up paying your money and taking your pick, but Jim's spintron clearly shows some undesirable bounce with just about every spring he's tested. What Jim cannot yet show, but will almost certainly be working towards, is the separation of components during the opening and closing flanks of the cam. If bounce can be clearly seen, it is almost certain that somewhere over the opening and closing periods some separation is also taking place,
the question is where, and how much ?
Hopefully in the fullness of time Jim's spintron will reveal all.

I plan to put some numbers on these pictures.

Unfortunately the laser sensor I had was too slow to give any meaningful info. They are really proud of those high speed laser sensors.

I snagged a sensor today on e-bay that should do a good job. I hope to have it set up by the weekend. Jim

Snotzo said:

Which way to go about sorting this little problem out ?

Click to expand...

Tiny dampers for the valve springs.

Greg

gjr said:

Snotzo said:

Which way to go about sorting this little problem out ?

Click to expand...

Tiny dampers for the valve springs.

Greg

Click to expand...

That is what an interference fit inner spring is for. Jim

comnoz said:

That is what an interference fit inner spring is for. Jim

Click to expand...

Do two interference fit springs work better than all the other options ? Would some other type of damper have less drag ( I don't know how to refer to the friction of the damper) ? If two springs are moving the harmonics around, can you make 'em vibrate at 200kHz at 10k rpm ?

Greg

Don't hold breath for much more dealing with springs only - read article Ken left us above - which depressingly concludes - even with interference fit dampener Between the dual springs of dissimilar coils its only restrains valve bounce a few more 100 rpms. Where will all this nonsense end? Hm a 'hi' rpm tolerant 180' shortish stroke twin might feed a turbo decently but then exhaust valves might not tolerate it.

What would a Ti upgrade cost, $100 for each valve and each spring and $50 for retainer etc, $500-600?
Two lifters $3-400, Maybe $1000 total if a market to buy in batches as ya know they wear out sooner when stressed.

gjr said:

comnoz said:

That is what an interference fit inner spring is for. Jim

Click to expand...

Do two interference fit springs work better than all the other options ? Would some other type of damper have less drag ( I don't know how to refer to the friction of the damper) ? If two springs are moving the harmonics around, can you make 'em vibrate at 200kHz at 10k rpm ?

Greg

Click to expand...

Interference fit springs have their good points along with bad points.

They are undoubtedly capable of operating at the highest rpm over the widest range without spring surge .
Two lighter springs can be used so the wire diameter can be smaller. That can be a benefit when you want high lift with short springs.

They create heat from the rubbing friction so they need to be changed more often or they will loose there tension.

They are usually heavier and may make lofting problems worse with some cam profiles.

I generally prefer double springs with interference damping for race use with a big cam but I prefer the single coil springs for most street use.

I am still testing different setups as I get time and I may change my mind -but not yet. Jim

There's a solution... you're just not going to like it. :mrgreen:

Oh, good nice!
Look out, you're about to re-ignite an incendiary discussion from the Desmo Norton thread.

Everybody, RUN!!