discussion of transfer, boost,exh ports,int/exh rotor timing...

[Jim Allen]

delete

 

[Jim Allen]

delete

 

[brad nichols]

I see and understand that the rotation is minimal at the top end and strength would be more of an advantage so it is not pounded out along with good lubrication. I am thinking about the OPS engines with no top end bushing mite survive better with more lube. What size engine is the 10 bolt head??

Brad

 

[Jim Allen]

Lubrication to the top end & bottom ends would be improved with slots instead of holes. Slots have a larger area than holes. The Nelson .45 has 6, 6-32 bolts; my .90 engine has 8, 8-32 bolts; older QD's had 10, 5-40 bolts; QD Pioneers have 8, 8-32 bolts; MB-40 have 5, 4 mm bolts. All of these engines have head bolts that pass through the cylinder's lip; not outside the cylinder's lip. The MB-40 has no cylinder.

JA

 

[Michael Costanzo]

Even though the MB-40 has been around for many years, the technology used in the main transfers & the boost transfer is relatively new. It is also much easier to change the transfers & cylinder ports when they are seperate pieces compared to a one piece upper end that has no cylinder. These transfers with a radius inside & outside contradict Gordon Blairs idea of the tea cup handle shapped transfer.

Manufactured engines always look for the most cost effective method to make the engine. Maybe this is why a very few manufacturers have taken the time to learn how to hard chrome plate aluminum.

Jim Allen

jim,are you taking about a AAC motor?

 

[Michael Costanzo]

Upload of test pic, not part of this discussion

Don,

The photo you posted reminded me of something. I still use it on both the gas & nitro engines with great success.

Jim

jim,is this next stage after a double bubble head or are they completly different?

 

[Jim Allen]

That's correct Michael. Ask engine manufactures why they stopped making AAC engines? The MB-40, the Nelson 45 & the Jet 45 all have aluminum cylinders.

Ja

 

[Jim Allen]

Upload of test pic, not part of this discussion

Don,

The photo you posted reminded me of something. I still use it on both the gas & nitro engines with great success.

Jim

jim,is this next stage after a double bubble head or are they completly different?

The two types are completely different. We are still using the double bubble head on the 45 engines because there hasn"t been enough time to test the toroidal type. We also use a tappered seat plug in the smaller engines. It doesn't seem to have much effect in the larger size engines.

JA

 

[Mike Rappold]

Jim,

On the MB and Nelson engines that do not use a brass chromed sleeve, is the advantage of the aluminum cylinder due to weight? Or is it due to a more consistent thermal expansion rate of like materials - aluminum piston /aluminum cyl.?

Mike

 

[Jim Allen]

Mike,

There are some definite advantages of an aluminum cylinder over a brass cylinder. The first is the lighter weight, esecially when the large size design cylinder head bolts passing through the liners lip is being used. Also the aluminum's thermal conductivity is greater than the brass which helps dissipate the heat of combustion. The aluminum is also more rigid than brass.The reason that either brass or aluminum cylinders can be used in a ring less ABC or AAC engine is that the expansion rates of both materials change (become slightly larger) once the hard industrial chrome has been applied. Therefore, in either case, if the cold fit is properly done, the engine's piston should never skuff of jam in it's bore; even if the engine is run in an overlean condition for an extended period of time. It was thought at one time that high silicone pistons would prevent the common problem of piston scuffing. Our in depth testing of various piston alloys (A-390, Mahle 138, Dispal-250, RSA-431 & RSA-444) definitely prove that "CYLINDER TAPER & CYLINDER FINISH" are the controlling factors to eliminating cylinder scuffing. I previously explained, with photos, that the only damage found in returned engines, that had been flown over lean at WOT, was the loss of the tapper amount in the sealing area. Since all metals yield to some extent (both the piston & the cylinder in this case) the fact that the piston's OD is larger than the cylinder's ID at the sealing point, explains why this system works. Higher silicon pistons DO NOT prevent piston to cylinder scuffing, but they do greatly extend the life of the piston to liner fit. Testing & actual in the field use proves these facts beyond any doubt! The "SUPER FINISH" used in our engine's cylinders plus the precise roundness of both pieces also contributes to a longer piston to liner fit.

Jim Allen

 

[Michael Costanzo]

Mike,

There are some definite advantages of an aluminum cylinder over a brass cylinder. The first is the lighter weight, esecially when the large size design cylinder head bolts passing through the liners lip is being used. Also the aluminum's thermal conductivity is greater than the brass which helps dissipate the heat of combustion. The aluminum is also more rigid than brass.The reason that either brass or aluminum cylinders can be used in a ring less ABC or AAC engine is that the expansion rates of both materials change (become slightly larger) once the hard industrial chrome has been applied. Therefore, in either case, if the cold fit is properly done, the engine's piston should never skuff of jam in it's bore; even if the engine is run in an overlean condition for an extended period of time. It was thought at one time that high silicone pistons would prevent the common problem of piston scuffing. Our in depth testing of various piston alloys (A-390, Mahle 138, Dispal-250, RSA-431 & RSA-444) definitely prove that "CYLINDER TAPER & CYLINDER FINISH" are the controlling factors to eliminating cylinder scuffing. I previously explained, with photos, that the only damage found in returned engines, that had been flown over lean at WOT, was the loss of the tapper amount in the sealing area. Since all metals yield to some extent (both the piston & the cylinder in this case) the fact that the piston's OD is larger than the cylinder's ID at the sealing point, explains why this system works. Higher silicon pistons DO NOT prevent piston to cylinder scuffing, but they do greatly extend the life of the piston to liner fit. Testing & actual in the field use proves these facts beyond any doubt! The "SUPER FINISH" used in our engine's cylinders plus the precise roundness of both pieces also contributes to a longer piston to liner fit.

Jim Allen

hey jim,i owned a few AAC motors and what i noticed and heard from other guy's that owned AAC motors was that they lost there fit quickly even after proper break in and normal running. do you think this is because the motors were mass produced and not fitted correctly from the factory? also when i buy my high dollar on-road motors (N/R) all hand fit and built, the fit is outstanding and after proper break in they last a long time!

 

[Michael Costanzo]

more question's. on a drum style rotor is it OK to make the taper on the inlet side flat? it comes from the factory with a tapper in it.the reason i ask is if you look at a disc rotor it is flat. i have a motor that only has 57* at closing and need to get it up to 62*.thanks,mike.

 

[Jim Allen]

Mike,

There are some definite advantages of an aluminum cylinder over a brass cylinder. The first is the lighter weight, esecially when the large size design cylinder head bolts passing through the liners lip is being used. Also the aluminum's thermal conductivity is greater than the brass which helps dissipate the heat of combustion. The aluminum is also more rigid than brass.The reason that either brass or aluminum cylinders can be used in a ring less ABC or AAC engine is that the expansion rates of both materials change (become slightly larger) once the hard industrial chrome has been applied. Therefore, in either case, if the cold fit is properly done, the engine's piston should never skuff of jam in it's bore; even if the engine is run in an overlean condition for an extended period of time. It was thought at one time that high silicone pistons would prevent the common problem of piston scuffing. Our in depth testing of various piston alloys (A-390, Mahle 138, Dispal-250, RSA-431 & RSA-444) definitely prove that "CYLINDER TAPER & CYLINDER FINISH" are the controlling factors to eliminating cylinder scuffing. I previously explained, with photos, that the only damage found in returned engines, that had been flown over lean at WOT, was the loss of the tapper amount in the sealing area. Since all metals yield to some extent (both the piston & the cylinder in this case) the fact that the piston's OD is larger than the cylinder's ID at the sealing point, explains why this system works. Higher silicon pistons DO NOT prevent piston to cylinder scuffing, but they do greatly extend the life of the piston to liner fit. Testing & actual in the field use proves these facts beyond any doubt! The "SUPER FINISH" used in our engine's cylinders plus the precise roundness of both pieces also contributes to a longer piston to liner fit.

Jim Allen

hey jim,i owned a few AAC motors and what i noticed and heard from other guy's that owned AAC motors was that they lost there fit quickly even after proper break in and normal running. do you think this is because the motors were mass produced and not fitted correctly from the factory? also when i buy my high dollar on-road motors (N/R) all hand fit and built, the fit is outstanding and after proper break in they last a long time!

Mike

I think it is because the hardness of the chrome that is plated to the inside of the cylinder's wall is not hard enough. It is impossible to tell how hard the chrome is by looking, however it should be approximately1100 Vickers. Chrome this hard cannot but cut even with a C-5 grade of carbide. Things such as running the chrome bath at the wrong temperature, wrong current density, depleted chemicals, DC voltage ripple to high & chemical make up of the bath will have an adverse effect on the hardness of the plated surface.

Jim Allen

 

[Jim Allen]

more question's. on a drum style rotor is it OK to make the taper on the inlet side flat? it comes from the factory with a tapper in it.the reason i ask is if you look at a disc rotor it is flat. i have a motor that only has 57* at closing and need to get it up to 62*.thanks,mike.

Mike,

On the inverted type drums, such as the Rossi type there is an advantage to knife edging the inside & then opening the case window to what ever is necessary. I suggest using trigonometry to calculate exactly where to cut the case. A degree wheel will not suffice for this job!

JA

 

[Michael Costanzo]

more question's. on a drum style rotor is it OK to make the taper on the inlet side flat? it comes from the factory with a tapper in it.the reason i ask is if you look at a disc rotor it is flat. i have a motor that only has 57* at closing and need to get it up to 62*.thanks,mike.

Mike,

On the inverted type drums, such as the Rossi type there is an advantage to knife edging the inside & then opening the case window to what ever is necessary. I suggest using trigonometry to calculate exactly where to cut the case. A degree wheel will not suffice for this job!

JA

hi jim,sorry for the late reply,i think i am going to just cut the rotor and not mess with the case.thanks,mike.

 

[Jim Allen]

Mike,

When I return to the shop, I'll look up all the information concerning the Rossi standard drum dimensions, their case dimensions & the timings that would result. Some cases I machined from #2024 aluminum but all were sleeved with #360 free machining brass. I tested & used both types of cases, machined & cast in my straight away boat. I made a mistake when I referred to the Rossi drum type as inverted. It is a standard drum with the carburetor coming straight out; not angled upward or downward. I was able to use the standard drum types in all of my Andy Brown boats by placing the curve in the velocity stack over the boom tube instead of behind it.

Drum valves are extremely durable but have an inherent amount of drag. Testing showed that the best total internal clearance between the valve & it's brass insert was .003" to .004".

JA