Zimmerman Valves for a 21 motor

[Martin Hamilton]

Glen did you have a Novarossi .21 turned around with a Zimmerman valve or some other type of valve fitted. Seem to remember pictures of boat and engine a while back. Martin

 

[mtruex]

Glen did you have a Novarossi .21 turned around with a Zimmerman valve or some other type of valve fitted. Seem to remember pictures of boat and engine a while back. Martin

h34r:

 

[Martin Hamilton]

My question is how to over come the piston hitting the crank at bdc, Was the crank relieved on the crank web or longer conrod fitted to raise the piston and then liner lifted to compensate. Or another way. Many thanks Martin.

 

[tnrcboatracer]

Jim Allen's pictorial on bell rotors look like the most efficient for crank case pumping.

Jon

 

[Glenn Quarles]

Glen did you have a Novarossi .21 turned around with a Zimmerman valve or some other type of valve fitted. Seem to remember pictures of boat and engine a while back. Martin

Martin, I have a couple of .12 that David Hall built for me...As you see Martin T has a 21.

Glenn

 

[Martin Hamilton]

Still looking as the best way on a Nova 21 for the piston to miss the crank at bdc when turning the motor around, ie relieve crank web or longer rod to lift the piston and raise liner to compensate. Or any better ideas, This is on a shaft of my own manufacture. Ive done this many many times over the years but never quite had this problem to this degree of the piston going this low at bdc because of the longer stroke and wrist pin higher in the piston. Any ideas. Best regards Martin.

 

[Tim_Duggan]

Martin,

The long stroke Thunder Tiger PRO21BXR engine has a beautiful rod in it and is longer than the NR rod. Cheap too. I tortured the h*ll out of one with a gear reduction unit and short pipe and no problems at all with the rod.

The next problem is you'll have to raise the sleeve and the ports in the case the appropriate amount.

Another alternative might be something I saw on speedmodelcar. At the bottom of This page

 

[Martin Hamilton]

Design problem re piston and crank now solved useing original rod. Tim the motor your refering to is made by Evgenie Soloveiv, He gets around this problem with a longer rod (1mm longer)+ the motor was designed taller with liner ports and port passages higher up. Regards Martin.