Boast vs Transfer

[Marty Davis]

Thanks. I tried to post a picture, but was it was too big (?) The picture along with a lot more on our CMB 35 testing and modification program is at http://www.modelgasboats.com/magazine/tech-articles-mainmenu-608/244-cmb-35-record-engine Our fooling with transfer port angles showed flat top transfers worked best. That shouldn't be the case in a well developed engine.

The modern 5 transfer engines use a large up angle on the A (closest to the exhaust) ports with a flatter angle and a horizontal hook on the B ports. The C (boost) ports have a large up angle. None of this information was helpful with the cruder style passages on a 3 transfer port engine. However, I think the angle cuts at the front edge of the side transfers did somewhat the same thing as the large up angle on the A ports. I would post pictures that show all this better, but I seem to be restricted to tiny picture posts.

Lohring Miller

Loring:

Please describe the reasoning for the horizontal slit below the exhaust port if you will....

 

[stan simpson iv]

Thanks. I tried to post a picture, but was it was too big (?) The picture along with a lot more on our CMB 35 testing and modification program is at http://www.modelgasboats.com/magazine/tech-articles-mainmenu-608/244-cmb-35-record-engine Our fooling with transfer port angles showed flat top transfers worked best. That shouldn't be the case in a well developed engine.

The modern 5 transfer engines use a large up angle on the A (closest to the exhaust) ports with a flatter angle and a horizontal hook on the B ports. The C (boost) ports have a large up angle. None of this information was helpful with the cruder style passages on a 3 transfer port engine. However, I think the angle cuts at the front edge of the side transfers did somewhat the same thing as the large up angle on the A ports. I would post pictures that show all this better, but I seem to be restricted to tiny picture posts.

Lohring Miller

Loring:

Please describe the reasoning for the horizontal slit below the exhaust port if you will....

Oil...

 

[NeilLickfold]

Peter Halman who used to make Irvine engines, has the same scallop cut on the exhaust side of the transfer port. He told me it improved flow and top end power.

I have not tried that at all but will do for sure.

Neil

 

[NeilLickfold]

Definitely an interesting thread. The MB40 with it's Jug handle mini motor bike port technology is an interesting engine. In saying that, the few that I have seen and run and did a power comparison on, while they did run well, had less torque and less power than the Nelson 40 F3D engine. The MB does have the ability to rev well beyond it's peak power, where as the N40 will only rev to about 33500 max witha peak hp from 30300 and flat to 31500 to 31800. Max torque is at 28500 rpm to 29000 depending on day and settings. It seems the advantage of the jug style ports is the ability to keep pumping effectively after peak power.

Looking at the articles, I did not see any mention of exhaust gasses going down the transfer passages until the pressures equalise then the transfer starts to happen.

Sometimes, very small changes( ie 0.05mm per side,) to the width of the bottom of the exhaust port to to the width of the transfer port, especially the ones closest to the exhaust can have quite a significant effect on total power out put or the torque from the engine. There does not seem to be an easy hard and fast rule to find these limits though. Cut and try works and when you have found a ration that works with a particular engine, the other same cut liners will perform the same in that series of engines.

Neil

 

[lohring]

Thanks. I tried to post a picture, but was it was too big (?) The picture along with a lot more on our CMB 35 testing and modification program is at http://www.modelgasboats.com/magazine/tech-articles-mainmenu-608/244-cmb-35-record-engine Our fooling with transfer port angles showed flat top transfers worked best. That shouldn't be the case in a well developed engine.

The modern 5 transfer engines use a large up angle on the A (closest to the exhaust) ports with a flatter angle and a horizontal hook on the B ports. The C (boost) ports have a large up angle. None of this information was helpful with the cruder style passages on a 3 transfer port engine. However, I think the angle cuts at the front edge of the side transfers did somewhat the same thing as the large up angle on the A ports. I would post pictures that show all this better, but I seem to be restricted to tiny picture posts.

Lohring Miller

Loring:

Please describe the reasoning for the horizontal slit below the exhaust port if you will....

Oil...

I think it was for piston oiling as well. It wasn't enough to make up for an out of round liner, though. The piston seized.

Lohring Miller

 

[Jim Allen]

Neil,

"Definitely an interesting thread. The MB40 with it's Jug handle mini motor bike port technology is an interesting engine. In saying that, the few that I have seen and run and did a power comparison on, while they did run well, had less torque and less power than the Nelson 40 F3D engine. The MB does have the ability to rev well beyond it's peak power, where as the N40 will only rev to about 33500 max with a peak hp from 30300 and flat to 31500 to 31800. Max torque is at 28500 rpm to 29000 depending on day and settings. It seems the advantage of the jug style ports is the ability to keep pumping effectively after peak power."

I find a similar conclusion in SAE paper 1999-01-3333, JSAE 9938088, on The Relationship between Port Shape & Engine Performance for Two-Stroke Engines. "As a result, we found that the maximum output is most related to the tangential inclination angles of the main transfer port, & the inner vent radius of the main transfer duct." I agree that finding the correct inside & outside radius appears to be a problem solved only by the cut & try method.

Jim A.

 

[Jim Allen]

Jim:

Brian Callahan sent me an image of the Aprilla ports as rubber molds of the inside of them. He called them "Tea Cup" style ports. Your description of an inside and outside radius is very graphic and exactly what I was talking about. The outside of the case was "Boulbous" sp?

I wrote to him asking if he still has the image, as I guess I have lost mine. If I get it, I will post.

<script type="text/javascript"> ipb.global.registerReputation( 'rep_post_674200', { domLikeStripId: 'like_post_674200', app: 'forums', type: 'pid', typeid: '674200' }, parseInt('') ); </script>

Marty Davis

​Marty,

Shown in the last photo are the curved transfers. The other photos show an engine with transfers all around the cylinder wall, even under the exhaust. This type of engine would have two exhausts, with two identical expansion chambers, to insure the arrival of the returning pulses at the same time. The scavenging pattern should be a centered column rising to the cylinder's head, pushing the exhaust gases down the cylinder's walls, out of the twin exhaust ports.

​JA

 

[Marty Davis]

Jim:

Brian Callahan sent me an image of the Aprilla ports as rubber molds of the inside of them. He called them "Tea Cup" style ports. Your description of an inside and outside radius is very graphic and exactly what I was talking about. The outside of the case was "Boulbous" sp?

I wrote to him asking if he still has the image, as I guess I have lost mine. If I get it, I will post.

<script type="text/javascript"> ipb.global.registerReputation( 'rep_post_674200', { domLikeStripId: 'like_post_674200', app: 'forums', type: 'pid', typeid: '674200' }, parseInt('') ); </script>


Marty Davis

​Marty,

Shown in the last photo are the curved transfers. The other photos show an engine with transfers all around the cylinder wall, even under the exhaust. This type of engine would have two exhausts, with two identical expansion chambers, to insure the arrival of the returning pulses at the same time. The scavenging pattern should be a centered column rising to the cylinder's head, pushing the exhaust gases down the cylinder's walls, out of the twin exhaust ports.

​JA

More like Lohring's image on his posts.... Yellow and Blue image.

 

[Andy Brown]

Jim:

Brian Callahan sent me an image of the Aprilla ports as rubber molds of the inside of them. He called them "Tea Cup" style ports. Your description of an inside and outside radius is very graphic and exactly what I was talking about. The outside of the case was "Boulbous" sp?

I wrote to him asking if he still has the image, as I guess I have lost mine. If I get it, I will post.

<script type="text/javascript"> ipb.global.registerReputation( 'rep_post_674200', { domLikeStripId: 'like_post_674200', app: 'forums', type: 'pid', typeid: '674200' }, parseInt('') ); </script>


Marty Davis

​Marty,

Shown in the last photo are the curved transfers. The other photos show an engine with transfers all around the cylinder wall, even under the exhaust. This type of engine would have two exhausts, with two identical expansion chambers, to insure the arrival of the returning pulses at the same time. The scavenging pattern should be a centered column rising to the cylinder's head, pushing the exhaust gases down the cylinder's walls, out of the twin exhaust ports.

​JA

Love those twin exhaust set ups Jimmy!

Weren't the home built engines of Ed Kaufus built with twin exhausts? Similar to the Cox .049 TD's. Two exhausts and two transfers.

Many twin exhaust set ups were built from during the 1930's and 1940's, on into the 1950's.

Here are a few.

 

[Andy Brown]

Jim:

Brian Callahan sent me an image of the Aprilla ports as rubber molds of the inside of them. He called them "Tea Cup" style ports. Your description of an inside and outside radius is very graphic and exactly what I was talking about. The outside of the case was "Boulbous" sp?

I wrote to him asking if he still has the image, as I guess I have lost mine. If I get it, I will post.

<script type="text/javascript"> ipb.global.registerReputation( 'rep_post_674200', { domLikeStripId: 'like_post_674200', app: 'forums', type: 'pid', typeid: '674200' }, parseInt('') ); </script>


Marty Davis

​Marty,

Shown in the last photo are the curved transfers. The other photos show an engine with transfers all around the cylinder wall, even under the exhaust. This type of engine would have two exhausts, with two identical expansion chambers, to insure the arrival of the returning pulses at the same time. The scavenging pattern should be a centered column rising to the cylinder's head, pushing the exhaust gases down the cylinder's walls, out of the twin exhaust ports.

​JA

Love those twin exhaust set ups Jimmy!

Weren't the home built engines of Ed Kaufus built with twin exhausts? Similar to the Cox .049 TD's. Two exhausts and two transfers.

Many twin exhaust set ups were built from during the 1930's and 1940's, on into the 1950's.

Here are a few.

More Twin exhaust pics.

And check out the Flat 4 with Slide box connecting rod. No rod angle issues here.

 

[John Beardslee]

Yes Andy, Ed's were splits. All the Quincy Looper full sized were as well

John

 

[timothy johnson]

Yes Andy, Eds White heat 4-60 engine had twin exhaust. He was running with us at a lake on Long Island in the 1960s, he would fly down from Poughkeepsi NY.

 

[Jim Allen]

Andy,

"Love those twin exhaust set ups Jimmy!

Weren't the home built engines of Ed Kalfus built with twin exhausts?"

The .90 cu in engine not only had twin exhausts & twin transfers, but also twin tuned pipes with exhaust baffles coupled to the .625" bore, barrel type carburetor. Look carefully at the linkages shown in the photo. All the linkage pieces were made of full hard tool steel. The engine's head & cylinder are one piece which is chromed, screwed & clamped to the crankcase. The pressurized fuel system used tuned pipe pressure from both pipe chambers to a float bowl to maintain an exact fuel level. The fuel system also had a check valve to maintain system pressure after the engine was started. This engine had many other features such as a Dykes piston ring, a hardened steel roller rod, a fully balanced phenolic rotor valve running on ball bearings, a piston with two windows & a hanger type wrist pin. The hanger type wrist pin piston allowed a very light weight piston because there are no piston bosses to support the wrist pin. This feature also allowed a connecting rod, stroke to length ratio of more than 1:2.

The twin tuned pipes had a total volume equal to the volume of a single chamber for the engine. Ed never used this setup in competition, however the entire setup was fully tested before Ed's death in his custom rigger. The testing was done at the lake on route #15 in New Jersey & Lake Ronkonkoma on Long Island.

Jim Allen

NOTE: The engine also had sub piston porting that was opened after initial starting. The plate screwed to the back side of the engine is where this lever type sliding valve was located. This is the same engine used in Ed's 4-60 steering strut hydro & his White heat 15 hydro.

 

[Andy Brown]

Andy,

"Love those twin exhaust set ups Jimmy!

Weren't the home built engines of Ed Kalfus built with twin exhausts?"

The .90 cu in engine not only had twin exhausts & twin transfers, but also twin tuned pipes with exhaust baffles coupled to the .625" bore, barrel type carburetor. Look carefully at the linkages shown in the photo. All the linkage pieces were made of full hard tool steel. The engine's head & cylinder are one piece which is chromed, screwed & clamped to the crankcase. The pressurized fuel system used tuned pipe pressure from both pipe chambers to a float bowl to maintain an exact fuel level. The fuel system also had a check valve to maintain system pressure after the engine was started. This engine had many other features such as a Dykes piston ring, a hardened steel roller rod, a fully balanced phenolic rotor valve running on ball bearings, a piston with two windows & a hanger type wrist pin. The hanger type wrist pin piston allowed a very light weight piston because there are no piston bosses to support the wrist pin. This feature also allowed a connecting rod, stroke to length ratio of more than 1:2.

The twin tuned pipes had a total volume equal to the volume of a single chamber for the engine. Ed never used this setup in competition, however the entire setup was fully tested before Ed's death in his custom rigger. The testing was done at the lake on route #15 in New Jersey & Lake Ronkonkoma on Long Island.

Jim Allen

NOTE: The engine also had sub piston porting that was opened after initial starting. The plate screwed to the back side of the engine is where this lever type sliding valve was located. This is the same engine used in Ed's 4-60 steering strut hydro & his White heat 15 hydro.

Thanks for posting Jimmy! Awesome stuff! My my brain has been dreaming about twin pipes for years.

 

[rbarile]

Andy B. got some twin exhaust photos for you.. Ed k. was at a namba straighaway in june of

1978 with his last boat , think it was a gator boat.. didn't have it ready but did a little show

and tell. It was my first attempt at the straightaways. He ran it late the in the fall with jim allen

in babalon NY. It was he last boat. Also some photo of Jim A . riggers from the 70s & 80s.

Rich B.

 

[Andy Brown]

Andy B. got some twin exhaust photos for you.. Ed k. was at a namba straighaway in june of

1978 with his last boat , think it was a gator boat.. didn't have it ready but did a little show

and tell. It was my first attempt at the straightaways. He ran it late the in the fall with jim allen

in babalon NY. It was he last boat. Also some photo of Jim A . riggers from the 70s & 80s.

Rich B.

Thanks for posting Rich! Those Twin pipes look awesome on the wide body Pinckert Gator!