About time for the spintron

comnoz · May 27, 2015

I got the bar a little higher yet.

Here is the 386C cam with the lifters I had profiled for the 312A cam. This gives me almost no loss of area under the curve. It is running with the IRL springs.

This should give us an 8500 rpm power peak with 9000 rpm overrun capability with the shortstroke 750.

It is amazing how much difference there is in the sound of the spintron at speed. With some cams you need to wear ear protection but with this cam and lifter setup it is smooth and quiet.

I stumbled into a deal I couldn't refuse last night. I bought a cam grinding machine !!!

[video]https://youtu.be/KEDRNLR1918[/video]

Hobot · May 27, 2015

The lower noise level implied less wasted motion moving air moecules and heating metal grains. Is this d/t more to better stable components or more components moving distorying vibrating oppositely and together enough to cancel?

Been pondering the usefullness of this higher rpm short stroke vs biger slower displacement. For sure higher rpm can pay off in peddling up acceleration via ratio advantage but best top speed may not rev much past torque peak. Best wishes juggling it all for some record making memories blowing minds not parts.

comnoz · May 28, 2015

hobot said:
The lower noise level implied less wasted motion moving air moecules and heating metal grains. Is this d/t more to better stable components or more components moving distorying vibrating oppositely and together enough to cancel?

Been pondering the usefullness of this higher rpm short stroke vs biger slower displacement. For sure higher rpm can pay off in peddling up acceleration via ratio advantage but best top speed may not rev much past torque peak. Best wishes juggling it all for some record making memories blowing minds not parts.

It just means the valve train is operating smoothly all together, under control of the cam lobe instead of inertia -and the valve is being lowered onto the seat instead of dropping on the seat with a bang and a bounce.

This will be the valve motion I will be using in my streetbike also -whether I do it by profiling a lifter or creating a master and grinding the profile into the cam.

I am all for long stroke -big displacement engines on the street. But on the track with displacement limits, the only way to beat a well developed Yamaha twin on a long track is with horsepower from high RPM. Jim

jseng1 · May 28, 2015

According to the spintron videos, the JS2 cam gets another 500 or 1000 RPM more than the PW3 cam before the intake valves begin to bounce.

In the PW3 video on page 6 Comstock's text says:
"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."

Then page 17 Comstock says:
“I used much higher spring pressure in the video with the JS2 cam than I did in the video with the PW3.”

The Honda springs are set up at 140 lbs for the PW3 video and the Beehive springs are setup at 142 lbs for the JS2 cam video - thats only 2 lbs difference. It makes the BSA lifters look very good. But if the PW3 iron cam flex is a problem then comparisons are blown.

I am concerned about exhaust valve float because when the ex valve floats it crashes into the intake valve and causes catastrophic destruction. I had problems with valves rubbing each other when over revved and knew other racers who tangled their valves and destroyed their motors and it was ugly. I never had problems with valve heads breaking off or valves dropping.

Snotzo
Making longer ramps to ease bounce is on my mind. In particular I am interested in splicing on the longer JS0/BSA spitfire closing ramp onto the JS2 cam at .1" and below (same as the 86C ramp at .1 and below, see my graph page 17). If the closing ramps are longer then at what point does the duration get too long and what will happen if it does? Also - the duration will still be less than an 86C so why is there any concern? Why couldn't the longer ramp splice onto all Norton cams?

What you say in this quote from page 17 gives me pause

"Modifying the ramp at the foot of the lift curve is not where the problem originates from, but it comes from earlier on the closing flank.
In an earlier post Comnoz presented a valve lift comparison of a cam with the results of a flat lifter measurement and a radius lifter meaurement super imposed. From the graph it can be clearly seen where and by how much the accelleration differs between the two measured profiles.

By changine the accelleration periods at either end of the design to be twice the original length, while still keeping the maximum designed valve lift, the rate of accelleration is drastically reduced, but unfortunately at the cost of having to accommodate a much longer overall duration."

Are you telling me I can't have it both ways?

snail · May 28, 2015

SteveA said:
edgefinder said:

Hi Jim, I'm not familiar with all these interchangeable British parts and wondered why you haven't made some BSA lifters with enough material in the right place to put a radius on like you want to try? If its a matter of not enough time I can understand that but they look like a simple part compared to all the other work you've done. Really interesting read and want to be at the salt flats to see and hear it run!

Click to expand...

Lots of things look easy

I wanted to source some BSA lifters and had a dialogue with SRM, BSA specialists, over a period of time. The stellite foot used on various vintage british designs requires a specialist process to join it on to the lifter. I understand tha this is not only expensive, particularly for low volume, and that cost will come over in the price to you, but it is something not many component manufacturers are doing today.

One assumes that AN have managed to do purchasing at a suitabe volume to maintain the price where it is for stock Norton lifters, whichh use the same process. Way back when BSA were making these parts they had the capability to do it in house.

SRM were prototyping and testing alternative BSA lifter manufacturing processes. They were unhappy with the results after testing, so they did not go to market. (maybe later with more prototyping and testing, I am sure there are a few BSA owners hoping that will be soon).

When Jim said earlier in this thread he had used a set of NOS BSA lifters, I had assumed that was because that is all that is currently available.

Might be a red herring, but has anyone ever used lifters from a Daimler V8 250? They're shorter than the BSA version and have a
1/2 " stem, but the radius face is 0.750 long. Radius is smaller than a BSA , don't have anything to measure that at the moment.
Weight is approx 3g more

SteveA · May 28, 2015

snail said:
Might be a red herring, but has anyone ever used lifters from a Daimler V8 250? They're shorter than the BSA version and have a
1/2 " stem, but the radius face is 0.750 long. Radius is smaller than a BSA , don't have anything to measure that at the moment.
Weight is approx 3g more

I can't quite work out how these are inserted into the lifter holes (or 'tappet block'), with that ridge at the ball end?

comnoz · May 28, 2015

snail said:
Might be a red herring, but has anyone ever used lifters from a Daimler V8 250? They're shorter than the BSA version and have a
1/2 " stem, but the radius face is 0.750 long. Radius is smaller than a BSA , don't have anything to measure that at the moment.
Weight is approx 3g more

I have never seen one before but it looks like it would be a good setup. Are they available? Jim

cjandme · May 28, 2015

comnoz said:
.........I stumbled into a deal I couldn't refuse last night. I bought a cam grinding machine !!!

Well check you out Jim.....Now, I can look forward to that thread too....... :mrgreen:

comnoz · May 28, 2015

cjandme said:
comnoz said:

.........I stumbled into a deal I couldn't refuse last night. I bought a cam grinding machine !!!

Click to expand...

Well check you out Jim.....Now, I can look forward to that thread too....... :mrgreen:

It could be fun. It's actually a small cylindrical grinder with a rocking bed attachment for grinding small industrial motor cams up to 14 inches long.
I had been looking for a cylindrical grinder for some time. The cam attachment was just a bonus.
They guy I got it from said he didn't think the cam attachment had ever been used. He wasn't even sure it was all there so I may have to make some pieces.
It will be a while before I get it. It's presently in California and weighs 3000 lbs. Jim

Dances with Shrapnel · May 28, 2015

So when do you begin staffing up?

Hobot · May 28, 2015

Thanx for keeping us all on the edges of our valve seats. I know this level has no relation to real life so my question about power band does not concern that but how it might pay off in some contest. So how can you predict where the torque peak will occur? My SuVee with rev over 10.5K but its only useful in 1st 3 gears then worthwhile pull only lasts to about 9K and top about same in 5th as 6th. I would chip in for a sonic spectrum analyzer to start creating a data base of what this and than rattle and ringing sound means before its too late. Oh yeah hope I did not forgot to mention cryo tempering to test to, especially springs.

comnoz · May 28, 2015

hobot said:
Thanx for keeping us all on the edges of our valve seats. I know this level has no relation to real life so my question about power band does not concern that but how it might pay off in some contest. So how can you predict where the torque peak will occur?

Engine analyzer software is pretty accurate.

SteveA · May 28, 2015

comnoz said:
snail said:

Might be a red herring, but has anyone ever used lifters from a Daimler V8 250? They're shorter than the BSA version and have a
1/2 " stem, but the radius face is 0.750 long. Radius is smaller than a BSA , don't have anything to measure that at the moment.
Weight is approx 3g more

Click to expand...

I have never seen one before but it looks like it would be a good setup. Are they available? Jim

http://www.jagspares.co.uk/Manners/Pricelists/V8250.htm

£30 each!

comnoz · May 28, 2015

SteveA said:
http://www.jagspares.co.uk/Manners/Pricelists/V8250.htm

£30 each!

Yeah, I found them.
The foot is not quite long enough to do what I am doing now but they could have some future uses. Thanks, Jim

So far the only thing I have found that might replace the Norton lifter for foot length is this B25 lifter.

jaydee75 · May 28, 2015

Quote: I can't quite work out how these are inserted into the lifter holes (or 'tappet block'), with that ridge at the ball end?

If you look closely it looks like that ridge is just a retaining ring.
Jaydee

comnoz · May 28, 2015

jaydee75 said:
Quote: I can't quite work out how these are inserted into the lifter holes (or 'tappet block'), with that ridge at the ball end?

If you look closely it looks like that ridge is just a retaining ring.
Jaydee

Some pictures show the top, including the ridge, removed from the shank. I don't know more than that. Jim

Snotzo · May 28, 2015

Are you telling me I can't have it both ways?

JS,
yes you can have it both ways, but whichever you choose will be a compromise to some extent.
In trying to run up to higher engine speeds, although the cam duration is fixed, the time available gets shorter the higher the engine speed rises.

Three ways most used to tackle this problem are:- 1/ decrease valve lift while retaining duration, 2/ keep current valve lift but extend cam duration, and 3/ use a combination of 1 and 2.

A commonly used rule of thumb to estimate the amount a valve would need to lift to present adequate flow through the curtain area is 36% of the inner seat diameter. Most very high output engines are using 40% and even higher.
Street engines will not require lifts of this magnitude, 25% to 30% generally being more appropriate.

For an intake valve having a 1.535 in. mm ID seat, 36% would indicate a valve lift requirement of 0.588 thou. At 40% the lift requirement is even higher.

At low engine speeds such lifts would be possible, but as engine speeds rise and time gets shorter, the valves would soon run out of spring control.
It becomes something of a juggling act, balancing gains against losses. Certainly the area under the lift curve is a very necessary part of a sucessful engine, and it is very easy to design such a cam that will satisfy the requirements. The hard part is to do so and have a cam that is fully compatible with the rest of the valve train, such that it will allow the engine to reach the desired peak speeds with everything under control, and most important - making the target horsepower and perhaps a bit more for good measure.

An alternative often employed is to increase the size of the valve and limit the lift. The valve weight goes up, but duration can be increased to provide sufficient area under the lift curve. It's a compromise but it can be made to work, but of course there can be so much more to it such as how much bigger can the valves go and still have valve clash and piston clearance.

There is design software available these days that is becoming increasingly better at sucessfully calculating the effects of detail changes within an engine, and used sensibly can give a great insight into what will and will not work, and most importantly, why.

jseng1 · May 28, 2015

Snotzo

What you say about smaller valves reminds me of when I was racing at National races with Dr Johns 1000cc Guzzi to compete against. He pushed his valve train limits to the point that the steel was turning colors and annealing. So he backed off on the valve diameters to bring down the reciprocating valve weight and keep things together.

I'm going through a lot of cam mapping right now. One thing that I would like to see is more info on the Norris RX, (HPI 7) which may be the same as the Megacycle 560NSS. I raced with this cam because it was long duration with relatively low lift and had the same proportions as the Axtell #3 It was a big cam and good for high RPM. Unfortunately this cam was not developed for BSA lifters. I'm thinking that the RX and the Axtel#3 (which I already have available for BSA lifters) are the cam shapes I want. They just need to be scaled up or down where I want them. I'd like one close to the parameters of the PW3 (JS2). I know that's a simplification but you get the idea.

snail · May 28, 2015

comnoz said:
SteveA said:

http://www.jagspares.co.uk/Manners/Pricelists/V8250.htm

£30 each!

Click to expand...

Yeah, I found them.
The foot is not quite long enough to do what I am doing now but they could have some future uses. Thanks, Jim

So far the only thing I have found that might replace the Norton lifter for foot length is this B25 lifter.

Yep, about the price of AN rod bolts!. I 'm the proud owner of 48 of those lifters, pity they're all used....
I have a Norris 480 cam which runs dangerously close to the edge of a BSA lifter. Strangely enough, there were a couple of B25 lifters in the spares box. Looks like someone else was thinking the same thing.

Snotzo · May 29, 2015

JS
I haven't seen any mention of the Norris RX being on the spintron, so I have to answer your comments without spintron backup.

I have measured the Norris RX cam and find it quite an interesting one. As you say, it certainly has duration, much more than any other Commando cam that has come my way. I find it somewhat surprising that you favored it as a race cam, but no doubt you had the rest of the engine arranged to make good use of it.

To re design it so that when used with a BSA lifter it would have the same valve lift curve as with the standard flat lifter is no big deal, the problem is getting a cam shop to grind it up.

Having run through this scenario I can say that the lift of the valves at TDC comes out at approx 0.166 thou, that is with the cam sitting on equal lift. The cam I measured had lobes separated 107.64 degrees, and the valve drop is based on that same separation.

The most interesting part I came to was when I ran a simulation with a Ti valve, alloy pushrod, steel re profiled cam, BSA lifters and your beehive springs set at 1.378 inches.

Keeping going up and up with engine speeds and no bounce or separation, eventually finding the first trace of separation occurred at 10500 rpm.
The wear path across the BSA lifter was calculated to be 0.516 inch, much less than the standard track length of 0.610 inch.

Before anyone queries who would want to run a Commando engine at this speed, I must stress that at this stage it is purely an exercise on paper and computer, intended to explore possibilities for controlling valve separation and bounce, but it does serve to indicate just what might be possible if all critical aspects can be arranged to work together in harmony.

The way things are going Comnoz will perhaps be looking to upgrade his spintron motor.