Sleeve Porting: What does what?

[dwilfong]

Here is the new button chamber for my RS1.01. Have a few more things to think about be for I make the last cuts. plug depth for one.

The chamber is .143 deep and the plug is at .043. there will be .005 head clearance.

Do I put the plug at the center of the distance to the piston centering it in the chamber or keep the .048 to the piston measurement?

I know this is a cut and see kinda thing but you have to start some where.

The chamber is .95cc with the plug and .005 squash making it 9.2CR with 195 ex timing.

Any thoughts?

David

 

[Jim Allen]

Here is the new button chamber for my RS1.01. Have a few more things to think about be for I make the last cuts. plug depth for one.

The chamber is .143 deep and the plug is at .043. there will be .005 head clearance.

Do I put the plug at the center of the distance to the piston centering it in the chamber or keep the .048 to the piston measurement?

I know this is a cut and see kinda thing but you have to start some where.

The chamber is .95cc with the plug and .005 squash making it 9.2CR with 195 ex timing.

Any thoughts?

David

David,

From the numbers you posted it looks as though the chamber is much deeper than what I'm using on my .90 cu in engine. The measured chamber volume on the 26 cc gas engine is less than 1.2 cc. I haven't measured the .90 engine because I'm still cutting heads. I have posted a print of the head presently being tested. Everything is drawn at a 1:10 ratio. The round pieces allow me to easily determine what radius will cause what change. They also easily locate the center of whatever radius is used to enable accurate intersection of the squish band & the flat at the center. Only the numbers used to make the button are shown on the print. As drawn the deck clearance is .001" & the squish band angle is 1 deg into the bowl. Squish band area is still 50% of the bores area. The plug is dropped .030" below the .480" dimension & the .020" flat in the bowl's center. I machine plug washers from #172 full hard beryllium copper because repeated tightening of the same stock plug washer will crush the copper washer provided.

For any head to work the loop established from the transfer geometry must be correct. I do not believe that flat top pistons should have transfers that are angled upward. The incomming charge from the main transfers should be used to cool the piston crown. Failure to cool the piston crown leads to very high combustion chamber temperatures that cannot be controlled by any amount of water on the head button.

DO NOT FORGET TO TURN THE NEEDLE TO A VERY RICH SETTING WHEN STARTING TO USE THE TOROIDAL HEAD!!

Jim Allen

 

[Joe Wiebelhaus]

Not to get away from the Toroidal Head design, I hacked this up in 1990, back in the OPS days.

 

[Tom Foley]

Pretty cool Joe !! And of course it's got the serial number on it !!!!

 

[dwilfong]

Here is the new button chamber for my RS1.01. Have a few more things to think about be for I make the last cuts. plug depth for one.

The chamber is .143 deep and the plug is at .043. there will be .005 head clearance.

Do I put the plug at the center of the distance to the piston centering it in the chamber or keep the .048 to the piston measurement?

I know this is a cut and see kinda thing but you have to start some where.

The chamber is .95cc with the plug and .005 squash making it 9.2CR with 195 ex timing.

Any thoughts?

David

David,

From the numbers you posted it looks as though the chamber is much deeper than what I'm using on my .90 cu in engine. The measured chamber volume on the 26 cc gas engine is less than 1.2 cc. I haven't measured the .90 engine because I'm still cutting heads. I have posted a print of the head presently being tested. Everything is drawn at a 1:10 ratio. The round pieces allow me to easily determine what radius will cause what change. They also easily locate the center of whatever radius is used to enable accurate intersection of the squish band & the flat at the center. Only the numbers used to make the button are shown on the print. As drawn the deck clearance is .001" & the squish band angle is 1 deg into the bowl. Squish band area is still 50% of the bores area. The plug is dropped .030" below the .480" dimension & the .020" flat in the bowl's center. I machine plug washers from #172 full hard beryllium copper because repeated tightening of the same stock plug washer will crush the copper washer provided.

For any head to work the loop established from the transfer geometry must be correct. I do not believe that flat top pistons should have transfers that are angled upward. The incomming charge from the main transfers should be used to cool the piston crown. Failure to cool the piston crown leads to very high combustion chamber temperatures that cannot be controlled by any amount of water on the head button.

DO NOT FORGET TO TURN THE NEEDLE TO A VERY RICH SETTING WHEN STARTING TO USE THE TOROIDAL HEAD!!

Jim Allen

Jim the tool I used is .125 radius or .250 diameter. To get the cc I want it has to plunge in and leave a flat on the side if the chamber. the radius is centered at the plug hight right now.

With 50% squash at a 1 deg angle.

I know you stated that you run high CR but with the pipe that Scott made he said that I should keep the CR at 9.2 because the pipe will raise the cylinder pressure.

Do you calculate full stroke CR to set the head cc? Is this a better way of calculating CR as the pipe pressure is a unknown.

I have put the 1/32 radius cut on top of the piston and this makes a big change in the ex timing. From 188 stock flat top to 195 with the radius.

Yes I flatten the tops of the transfers with a flat top piston. that is the only mod to the stock ports for now.

David

 

[Norm Doerr]

Pretty cool Joe !! And of course it's got the serial number on it !!!!

LOL.. yes the identifying serial number. Joe brought that to one of our club meetings, best cut away "visable" engine. I have ever seen.

 

[Jim Allen]

"Jim the tool I used is .125 radius or .250 diameter. To get the cc I want it has to plunge in and leave a flat on the side if the chamber. the radius is centered at the plug hight right now.

With 50% squash at a 1 deg angle.

I know you stated that you run high CR but with the pipe that Scott made he said that I should keep the CR at 9.2 because the pipe will raise the cylinder pressure.

Do you calculate full stroke CR to set the head cc? Is this a better way of calculating CR as the pipe pressure is a unknown.

I have put the 1/32 radius cut on top of the piston and this makes a big change in the ex timing. From 188 stock flat top to 195 with the radius.

Yes I flatten the tops of the transfers with a flat top piston. that is the only mod to the stock ports for now."

David

There are no torodial head designs that have a flat or straight surface on the sides of the chamber. I'm sorry that you are not able to read the proprietary information on the Two Stroke Tech Site about toroidal heads & how they work. I really do not care what the exact geometric or effective compression ratio is, therefore I make a rough calculation by dividing the button's volume into the displacement of the engine.

The tuned pipes pressure has no effect on the toroidal design. The measured pressures in either my nitro pipe or gas pipe is well beyond anything being used. Part of the developement of that pressure is accomplished with stingers whose lengths are no less than 13 to 14 times their inside diameters.

It would be better to put a radius on both the piston edge & the top of the exhaust. .025" to .027" would be sufficient.

Jim Allen

 

[dwilfong]

"Jim the tool I used is .125 radius or .250 diameter. To get the cc I want it has to plunge in and leave a flat on the side if the chamber. the radius is centered at the plug hight right now.

With 50% squash at a 1 deg angle.

I know you stated that you run high CR but with the pipe that Scott made he said that I should keep the CR at 9.2 because the pipe will raise the cylinder pressure.

Do you calculate full stroke CR to set the head cc? Is this a better way of calculating CR as the pipe pressure is a unknown.

I have put the 1/32 radius cut on top of the piston and this makes a big change in the ex timing. From 188 stock flat top to 195 with the radius.

Yes I flatten the tops of the transfers with a flat top piston. that is the only mod to the stock ports for now."

David

There are no torodial head designs that have a flat or straight surface on the sides of the chamber. I'm sorry that you are not able to read the proprietary information on the Two Stroke Tech Site about toroidal heads & how they work. I really do not care what the exact geometric or effective compression ratio is, therefore I make a rough calculation by dividing the button's volume into the displacement of the engine.

The tuned pipes pressure has no effect on the toroidal design. The measured pressures in either my nitro pipe or gas pipe is well beyond anything being used. Part of the developement of that pressure is accomplished with stingers whose lengths are no less than 13 to 14 times their inside diameters.

It would be better to put a radius on both the piston edge & the top of the exhaust. .025" to .027" would be sufficient.

Jim Allen

So if I understand what you are saying. CR is not some thing you calculate to say.

If I do the math 16.6cc eng with a .95cc chamber is a 17.46 CR. Where do you start at in testing 19-1.

Just moving the donut up and down till the top end power is where you want it.

I can see where having a Dino is a must to tuning this head design.

I will try a new one and stop with the radius center at the band and see where I am.

Dose the plug distance to the piston mean more than it being centered in the chamber?

David

 

[Jim Allen]

Start with the plug depth shown on the drawing. If you are concerned about to much compression, use a .3125" (.1562" radius) ball nose end mill instead of the .375" (.1875" radius) shown on the print. Keep the .020" wide flat at the .480" depth.

Positioning either ball (.3125" or .375") so that their circumferences hit at the end of the .020" flat & the end of the 50% squish band point allows volume changes with everything else still the same. To do this you must know where the center of the radaii are located. This is the purpose of the 1:10 print, unless you have access to Pro-E.

Everything becomes very easy when you make these things on a rotary table or a dividing head. Machine, in the lathe, the entire top of the head botton first including the plug's thread. Using the plugs thread & the top of the button, mount the button upside down on the rotary table or dividing head. Zero the button to the milling machine spindle. Translate the required amount taken from the 1:10 print & plunge in to the required depth. Cut the squish band last while holding the button by it's threaded hole in a fixture, in the lathe.

You don't need a dyno to tell if the button is working. Turning the needle richer & being able to burn that extra fuel will become evident in the increased HP. To determine the maxium compression, continue to drop the toroidal down until the engine begins to drop of when over-reved.

Jim Allen

 

[stan simpson iv]

Start with the plug depth shown on the drawing. If you are concerned about to much compression, use a .3125" (.1562" radius) ball nose end mill instead of the .375" (.1875" radius) shown on the print. Keep the .020" wide flat at the .480" depth.

Positioning either ball (.3125" or .375") so that their circumferences hit at the end of the .020" flat & the end of the 50% squish band point allows volume changes with everything else still the same. To do this you must know where the center of the radaii are located. This is the purpose of the 1:10 print, unless you have access to Pro-E.

Everything becomes very easy when you make these things on a rotary table or a dividing head. Machine, in the lathe, the entire top of the head botton first including the plug's thread. Using the plugs thread & the top of the button, mount the button upside down on the rotary table or dividing head. Zero the button to the milling machine spindle. Translate the required amount taken from the 1:10 print & plunge in to the required depth. Cut the squish band last while holding the button by it's threaded hole in a fixture, in the lathe.

You don't need a dyno to tell if the button is working. Turning the needle richer & being able to burn that extra fuel will become evident in the increased HP. To determine the maxium compression, continue to drop the toroidal down until the engine begins to drop of when over-reved.

Jim Allen

Jim I have a question.I have been reading this thread,with this type of head will you still get the same RPM as the single/double bubble ? thx

 

[dwilfong]

Start with the plug depth shown on the drawing. If you are concerned about to much compression, use a .3125" (.1562" radius) ball nose end mill instead of the .375" (.1875" radius) shown on the print. Keep the .020" wide flat at the .480" depth.

Positioning either ball (.3125" or .375") so that their circumferences hit at the end of the .020" flat & the end of the 50% squish band point allows volume changes with everything else still the same. To do this you must know where the center of the radaii are located. This is the purpose of the 1:10 print, unless you have access to Pro-E.

Everything becomes very easy when you make these things on a rotary table or a dividing head. Machine, in the lathe, the entire top of the head botton first including the plug's thread. Using the plugs thread & the top of the button, mount the button upside down on the rotary table or dividing head. Zero the button to the milling machine spindle. Translate the required amount taken from the 1:10 print & plunge in to the required depth. Cut the squish band last while holding the button by it's threaded hole in a fixture, in the lathe.

You don't need a dyno to tell if the button is working. Turning the needle richer & being able to burn that extra fuel will become evident in the increased HP. To determine the maxium compression, continue to drop the toroidal down until the engine begins to drop of when over-reved.

Jim Allen

Thanks as always Jim.

Have to get some more tooling(end mills) and make the plug fixture and give this a good try.

I see where you can make a few blanks and once you get the table set up you only have to make one move to use the different mill sizes.

What kind of fixture are you using to mount the button to the table?

When you have a eng with a larger or smaller bore the mill sizes will have to change so you only work with the radius of the end mill.

I think I got it now.

David

 

[Jim Allen]

"What kind of fixture are you using to mount the button to the table?"

A small flat plate with a 1/4-32 stud sticking out that is bolted to the 1.000" tooling plate on my rotary table is what I use.

 

[dwilfong]

"What kind of fixture are you using to mount the button to the table?"

A small flat plate with a 1/4-32 stud sticking out that is bolted to the 1.000" tooling plate on my rotary table is what I use.

Sounds simple enough. will get right on it after the race next weekend. B)

Have to break in the new eng tomorrow. Got a 2920 and a 3020 to spin up tomorrow.

thanks Jim.

 

[Jim Allen]

"Jim I have a question.I have been reading this thread,with this type of head will you still get the same RPM as the single/double bubble ? thx "

I have dyno tested & run, various head shapes on both nitro & gas engines. All the engines had tuned pipes & used tuned pipe pressure to deliver an adequate amount of fuel. The head button types include; cones, trumphets, hemisphericals with straight sides & flat tops, plain hemisphericals of various radaii, double bubble hemisphericals, peep hole hemisphericals & toroidals.

On nitro engines, cones, double bubbles & toroidals gave the best HP at high RPM's. On gas engines, cones, hemisphericals with straight sides & flat tops, plain hemisphericals & toroidals were the best. The squish band clearances were always close (.001" to .005") & the squish band area held at 50%, if possible.

All of these head types would quickly go into detonation if the engine was over-compressed or over-leaned, with the exception of the torodials. When the toroidals were compressed to numbers that would be impossible for the other heads, there still was no detonation. However, over-compression did show a significant HP decrease at higher RPM's.

Jim Allen

 

[stan simpson iv]

"Jim I have a question.I have been reading this thread,with this type of head will you still get the same RPM as the single/double bubble ? thx "

I have dyno tested & run, various head shapes on both nitro & gas engines. All the engines had tuned pipes & used tuned pipe pressure to deliver an adequate amount of fuel. The head button types include; cones, trumphets, hemisphericals with straight sides & flat tops, plain hemisphericals of various radaii, double bubble hemisphericals, peep hole hemisphericals & toroidals.

On nitro engines, cones, double bubbles & toroidals gave the best HP at high RPM's. On gas engines, cones, hemisphericals with straight sides & flat tops, plain hemisphericals & toroidals were the best. The squish band clearances were always close (.001" to .005") & the squish band area held at 50%, if possible.

All of these head types would quickly go into detonation if the engine was over-compressed or over-leaned, with the exception of the torodials. When the toroidals were compressed to numbers that would be impossible for the other heads, there still was no detonation. However, over-compression did show a significant HP decrease at higher RPM's.

Jim Allen

Thx you for this information...

 

[Marty Davis]

Jim:

In order to maintain a 50% squish band area on a .21 sized engine, it is necessary to use a 3/32" cutter. If you use this cutter, there will be some straight side to the chamber. Do you have any feeling about this? I have tried almost everything I can think of to get a chamber without straight sides and the CR would be so high that it could never work.

Thoughts....

 

[dwilfong]

Marty is this with a constant radius as on a end mill?

I have found that it is this way with the bigger eng also. you can't get any volume. with out the strait sides.

Like you say the CR is over the top.

But maybe it will work if there is no detonation?

Have a feeling it will be hard on a stock eng.

Piston breaking and all the rest of the things that go bad rods and crank pins.

David

 

[Marty Davis]

David:

Yes, I will use a 3/32" tool. I really like using a lathe rather than rotary table mill. Our mill is not nearly as precise as being able to do it with a lathe. I can work very accurately with the lathe. Just no way to keep from straight sides with the amount of plug area that is taken up on a .21 sized engine. I used straight sides on all my engines with the previous buttons that I made with good success. The main reason that I am so interested in the Toroidal head shape is the lack of detonation and the ability to run higher CR. That would be awesome for me with the small engines. Would allow me to get away from so much pinch in the liner that I have to use to get adequate torque now. More HP and good torque would be awesome. Detonation makes my engines not last very long.

 

[RodneyPierce]

Marty, I just tired to make one, and botched it up at the end, but I ended up using an 1/8" tool and got the following: Plug face .036 away from the piston face. (.026 deep from the squish band, I had planned on .010 head clearance) .096 wide squish band at 1* angle. ended up at .17cc with the plug installed. I didnt keep track of how deep I plunged the cutter in, but its possible. It wouldnt be possible if you wanted much wider of a squish band then that though. At least not with the 1/8 inch radius cutter.

That .096 nets us a squish band of about 50% in a .21 GO/Nova if Im calculating that correctly. I did not end up with hardly any straight wall in the chamber.

 

[RodneyPierce]

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