Rotary valve engines
02-09-2008, 10:12 PM
#5
My Feedback: (29)
RE: Rotary valve engines
There may eventually be some ZDZ knockoffs but I doubt there will ever be any original designs from China. I set out to design a 50-80cc with conventional model engine architecture. I ran into some technical problems with the crankshaft. I found that ZDZ and DA designs weigh less and cost less to produce. Im sure that every other designer came to the same conclusion, thats why there aren't any jumbo size OS 40s out there.
02-09-2008, 10:33 PM
#6
RE: Rotary valve engines
I always wondered how the rotor part maintained a good seal ...more so as engine time adds up. Seems like any wear would degrade its performance. The power is sure there with rotary valve engines...when in good shape! Thanks Capt,n
02-09-2008, 11:21 PM
#7
RE: Rotary valve engines
The rear disc design is a VERY old design on twostrokes YS uses identical setup-as did earlier designs from years previous.
the rotor floats on a pin and the changes in crankcase pressure, seals or release seal as pressure changes .
wear really is not a factor.. scoring and poor lube IS a factor.
the materials have to self lap as they run and a proper oil seal is also desireable. a slapping noise in the ZDZ engine-whenidly flipping prop back n forth is the rotor sealing -releasing . The cantaleve crank used is also an old proven dsign - the pressed together cranks on weedies - is a cheap assy method but very good --- as long as it is not banged on the ground and the crank alignment knocked out of whack - it DOES happen . I have dug ZDZ80' out of ground from a crash - the screwed in prop screw is bent sometimes - I never have never seen a bent crank .
the rotor floats on a pin and the changes in crankcase pressure, seals or release seal as pressure changes .
wear really is not a factor.. scoring and poor lube IS a factor.
the materials have to self lap as they run and a proper oil seal is also desireable. a slapping noise in the ZDZ engine-whenidly flipping prop back n forth is the rotor sealing -releasing . The cantaleve crank used is also an old proven dsign - the pressed together cranks on weedies - is a cheap assy method but very good --- as long as it is not banged on the ground and the crank alignment knocked out of whack - it DOES happen . I have dug ZDZ80' out of ground from a crash - the screwed in prop screw is bent sometimes - I never have never seen a bent crank .
