About time for the spintron

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JS
remember the spintron is operating cold, and not experiencing the heat of a running engine, consequently clearances set will not change on the spintron, but they most certainly will on a running engine.

Your experience with the tappets on a BSA is common. Clearances could be set to nil, but with the pushrods free to rotate. This positioned the valve train to start taking up the slack while the follower was still on the early part of the ramp, and it would be in a similar position when closing.

When the engine is hot and working at high rpm, the flexure and bending of valve train components will ensure that the valve will open when the cam reaches the point where the velocity curve starts to suddenly change from constant velocity to begin pushing the valve open - unless of course the tappets have been set too wide to start with, then the ramps, however well designed, will have no effect, and the cam on opening will crash against the follower causing tremendously high stress in valve train components, particularly pushrod, and will also close the valve in a similarly violent manner.

An examination of a cam profile as graphed for cam lift via software such as Cam Analyser or similar, will show the ramps in detail, and it will be readily apparent that a good starting point for consideration of initial tappet setting is by using a clearance that will place the opening point about halfway along the ramp. From the ramps shown in earlier posts, it is clear that all ramps are not equal, and depending on the cams in question, can vary in both rate of lift, and duration of ramp.

The foregoing at best can only be a generalisation. All engines do not respond in the same way, even those of the same make and model.
It has been said that one should consider all engines as being made of materials that , although called steel, aluminium, titanium or whatever, can in fact be best considered as being some peculiar kind of rubber, because every single item that goes to make up an engine, if subjected to sufficient force, will distort, bend, deflect, twist, or in some way deviate from it's unstressed condition, and when the force is removed, hopefully, it will return more or less, to it's original form.

In a way this ideally explains the workings of a pushrod valve train.
 
jseng1 said:
I've adjusted my clearance figures a couple thou.

Its best to adjust them hot with .004' intake and .006" exhaust clearance. Then measure cold and keep records so you can always adjust cold. But 1st you want to check hot because cold measurements will be different with alum or iron barrels. Personally I've been running mine at .003 and .005" and I haven't noticed it changing. Its quieter and easier on the valve train.

.002" looser won't hurt anything and I've run them this way as well (but looser will add high RPM valve bounce).


When I worked at a BSA shop we used to adjust them as tight as possible (no feeler gauge) with the slightest amount of play that you could barely feel and still never burned a valve.

Jim Comstock - It would be good for you to verify if tighter tappet clearance really means less bounce. It could just as well be that the cam flexing and bouncing back is causing the valve to bounce and a lot of clearance (such as .015" or .020") might eliminate the rocker arm from pushing the valve open and causing it to bounce. If it worked then this would be an easy fix.

I tried it at .004 and then did 1 run at .002 -6500 rpm. There didn't seem to be any obvious difference. Increasing the clearance would definitely make the problem worse.
 
So I made it past 9000 rpm. 9200 rpm to be exact -then I thought I was going to be picking up parts.

This is the 312A grind cam with a flat to 4 in. radius profiled stock lifter. Stock pushrods and the conical springs at 125lbs on the seat.

[video]https://youtu.be/Y7X_-wKoGsA[/video]

It definitely launches the valve over the nose. Now is where some lightweight followers may be of some value but I can't find any grinds suitable for the BSA follower at the RPM we need for Sir Eddies bike.

I will be trying some different springs next -and maybe lighten the lifters a bit. Jim
 
Jim Comstock - Is the 86C the best ramp you've seen so far with either a flat or BSA 650cc 1-1/8' radiused lifter?

Snotzo - I understand what you're saying - thats why I set the tappet clearance hot - so things won't tighten up.
 
jseng1 said:
Jim Comstock - Is the 86C the best ramp you've seen so far with either a flat or BSA 650cc 1-1/8' radiused lifter?

Snotzo - I understand what you're saying - thats why I set the tappet clearance hot - so things won't tighten up.

Well...I would say that the 86c is the best behaved big cam I have tested yet.

Of course the ramp needs to match the balance of the profile. Jim
 
Until the spintron results are installed in your real motorcycle! I too am loving every minute of it.
 
comnoz said:
So I made it past 9000 rpm. 9200 rpm to be exact -then I thought I was going to be picking up parts.

This is the 312A grind cam with a flat to 4 in. radius profiled stock lifter. Stock pushrods and the conical springs at 125lbs on the seat.

[video]https://youtu.be/Y7X_-wKoGsA[/video]

It definitely launches the valve over the nose. Now is where some lightweight followers may be of some value but I can't find any grinds suitable for the BSA follower at the RPM we need for Sir Eddies bike.

I will be trying some different springs next -and maybe lighten the lifters a bit. Jim

Looks like you found something with the asymmetrical lifter profile to help eliminate the bounce. You have got to be excited with the results, I can say that I am!
I sat here with a big smile watching this posting @ 9200 rpm! WOW!!!
Thank you Jim for all you are doing with the development to make my dads dream come true! You could stop here for all other short stroke motors and know that mission is accomplished.
YOU ARE AN AMAZING GUY!
10,500 here we come!!!
 
Well here it is.
10,300 was a fast as my spintron would go. 312A cam, profiled stock lifters, stock pushrods, expensive..irl springs.
Now with a little lifter lightening and the lighter valve that is in the Sir Eddies bike we will have 10,500 with a little breathing room.
Time for a brew.

[video]https://youtu.be/cRsjDufGlKo[/video]
 
comnoz said:
Well here it is.
10,300 was a fast as my spintron would go. 312A cam, profiled stock lifters, stock pushrods, expensive..irl springs.
Now with a little lifter lightening and the lighter valve that is in the Sir Eddies bike we will have 10,500 with a little breathing room.
Time for a brew.

Jim,

Enjoy that brew, you earned it!

Have a question. On the subject of the Sir Eddie 69 mm stroke engine, it sounds like you've got a viable cam alternative that will allow extremely high speed engine operation. At 10,000 rpm the average piston speed is just a smidge north of 4,500 ft/min so that too is in the realm of reality. Based on the majority of the published airflow potential of Norton big valve heads (mostly if not all your data) it appears that entitlement is somewhere in the neighborhood of ~ 155 cfm at 28" WC. Published relationships I see equating airflow to rpm potential for a specific size engine, suggest that the given airflow of 155 cfm will not support 10,000 rpm operation.

Given that I have no idea what the actual airflow of the Sir Eddie head is, and that the literature I am looking at might not reflect present day reality, it would be interesting to hear your thoughts on the subject. I know you do a bit of modeling in Performance Trends software, so perhaps you've already sorted all this out. Either way it would be interesting to hear your thoughts on rpm potential of a specific engine based on airflow.
 
WZ507 said:
comnoz said:
Well here it is.
10,300 was a fast as my spintron would go. 312A cam, profiled stock lifters, stock pushrods, expensive..irl springs.
Now with a little lifter lightening and the lighter valve that is in the Sir Eddies bike we will have 10,500 with a little breathing room.
Time for a brew.

Jim,

Enjoy that brew, you earned it!

Have a question. On the subject of the Sir Eddie 69 mm stroke engine, it sounds like you've got a viable cam alternative that will allow extremely high speed engine operation. At 10,000 rpm the average piston speed is just a smidge north of 4,500 ft/min so that too is in the realm of reality. Based on the majority of the published airflow potential of Norton big valve heads (mostly if not all your data) it appears that entitlement is somewhere in the neighborhood of ~ 155 cfm at 28" WC. Published relationships I see equating airflow to rpm potential for a specific size engine, suggest that the given airflow of 155 cfm will not support 10,000 rpm operation.

Given that I have no idea what the actual airflow of the Sir Eddie head is, and that the literature I am looking at might not reflect present day reality, it would be interesting to hear your thoughts on the subject. I know you do a bit of modeling in Performance Trends software, so perhaps you've already sorted all this out. Either way it would be interesting to hear your thoughts on rpm potential of a specific engine based on airflow.


Sir Eddies engine is 500 cc with a 73mm bore. That puts the stroke around 59mm. I do not yet know what the cylinder head flows.

It is the 750 roadracer thet uses an 83 X 69 mm bore and stroke. That engine will be using the 386C cam with the offset radius lifter. I expect to run it around 8500. Jim
 
comnoz said:
Well here it is.
10,300 was a fast as my spintron would go. 312A cam, profiled stock lifters, stock pushrods, expensive..irl springs.
Now with a little lifter lightening and the lighter valve that is in the Sir Eddies bike we will have 10,500 with a little breathing room.
Time for a brew.

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

This is amazing Jim, what great news. I will be sure to share it when I head up to visit my dad today and honor the many veterans that served our country.
You had a note that you are using the profiled stock lifters with the 0 to 4 inch radius. Does the BSA lifters have enough room to have a radius of 0 to 4?
Looks like I am going to have to go out and dig a can up in the back yard for the irl springs. Great news Jim! THANK YOU!
 
Son of Siredward said:
comnoz said:
Well here it is.
10,300 was a fast as my spintron would go. 312A cam, profiled stock lifters, stock pushrods, expensive..irl springs.
Now with a little lifter lightening and the lighter valve that is in the Sir Eddies bike we will have 10,500 with a little breathing room.
Time for a brew.

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

This is amazing Jim, what great news. I will be sure to share it when I head up to visit my dad today and honor the many veterans that served our country.
You had a note that you are using the profiled stock lifters with the 0 to 4 inch radius. Does the BSA lifters have enough room to have a radius of 0 to 4?
Looks like I am going to have to go out and dig a can up in the back yard for the irl springs. Great news Jim! THANK YOU!

No, unfortunately I have not found a way to use the BSA A65 lifter. There is not enough length for the necessary contact area.
Pretty much stuck with the stock Norton lifter unless I can figure out how to get a BSA B25 lifter in there. Jim
 
pete.v said:
What is an irl spring?

It is a spring designed for an Indy car engine.
In this case it is a small diameter, double spring that has been plasma nitride treated and designed with a very high resonant frequency.
 
comnoz said:
pete.v said:
What is an irl spring?

It is a spring designed for an Indy car engine.
In this case it is a small diameter, double spring that has been plasma nitride treated and designed with a very high resonant frequency.

IRL, of course. Indycar Racing League came to mind becauce of the acronym and the race yesterday but I didn't put the 2 together. Now it's obvious.

Your timing is rather apropriate.
 
what about Norton lifters cut to slabs then skeletonized as I think Ludwig showed us? Used inserts in cylinder bores to hold the slab aligned. No time to find photo right now but scary impressive mass reduction. chow.
 
hobot said:
what about Norton lifters cut to slabs then skeletonized as I think Ludwig showed us? Used inserts in cylinder bores to hold the slab aligned. No time to find photo right now but scary impressive mass reduction. chow.

That could be done but lifter mass does not seem to be a problem as it is.

Heavy lifters create loft. Some loft is desired in this case as it makes for additional duration at high speed. Loft is OK as long as the lifter "lands" on the right area of the cam.

Fitting stock lifters into Sir Eddies billet cylinders is the problem...
 
I`m really excited about your progress Jim, improving all the time .

Just a question, the 86C cam test with offset 3" radius stock lifters, what seat and over the nose pressure did you used?

Sten
 
billet said:
I`m really excited about your progress Jim, improving all the time .

Just a question, the 86C cam test with offset 3" radius stock lifters, what seat and over the nose pressure did you used?

Sten

A rather low 100 and 230 lbs.
 
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