Question For The Machinists...

[oldlugs]

Hi folks, I finally bought myself a small 7x10 lathe for hobby use, and want to make a few .21 size flywheels and cones to convert car/buggy engines to marine. My question is, about chucking reamers... The cranks have a 7mm shaft. Should I use a 7mm chucking reamer to bore the flywheel cones, or go with a slightly smaller reamer to get a tighter fit? Will the hole bored by the 7mm reamer fit the cranks well...or?

Thanks, Duane

 

[Hydro Junkie]

Something you might want to check is if the shaft has a taper on it. I've seen some that do and others that use a sleeve between the shaft and flywheel

 

[oldlugs]

The NovaRossi and AXE Rossi (and a couple others I have) all use a 7mm straight shaft, but have an SG clutch end that I'll trim off. The brass cones I'll be cutting, have the taper to lock onto the flywheel... I'll be making some similar in size and appearance to the NovaRossi marine flywheels and cones, only a bit shorter on the flywheel face. The cable collets need to grab those fewer threads that SG cranks have.

BTW- I was thinking of turning a couple of flywheels from 360 brass, and using 6061 aluminum for their cones... Will 360 brass stay together OK at 30,000+ RPM?

Duane

 

[El Zorro]

Duane,

I have made flywheel cones for some Picco's in years past, and I did NOT drill and ream the shaft bores. I always drilled the hole about .030 under size and then bored the hole to size, with about a .002 slip fit on the crankshaft. It actually can be a bit smaller than this, as the bore will open up some when you split the cone ( I split mine with a thin saw blade ). Why did I do it this way? Anything that's going to be spinning at 25-30K RPM's I want to make sure that it's as true as possible. Machine the entire cone in one operation while chucked in the lathe..........you won't be sorry!

Dick Tyndall

 

[El Zorro]

The NovaRossi and AXE Rossi (and a couple others I have) all use a 7mm straight shaft, but have an SG clutch end that I'll trim off. The brass cones I'll be cutting, have the taper to lock onto the flywheel... I'll be making some similar in size and appearance to the NovaRossi marine flywheels and cones, only a bit shorter on the flywheel face. The cable collets need to grab those fewer threads that SG cranks have.
BTW- I was thinking of turning a couple of flywheels from 360 brass, and using 6061 aluminum for their cones... Will 360 brass stay together OK at 30,000+ RPM?

Duane

Another suggestion.........use the aluminum for the flywheels, the brass for the cones.

Dick

 

[oldlugs]

Another suggestion.........use the aluminum for the flywheels, the brass for the cones.
Dick

Thanks, Dick. I was planning on turning a few flywheels out of aluminum, and a couple of brass, as well. I think the brass ones my help launching and milling on the really high timed engines...(?). Anyway, they'll look good all polished up.

Duane

 

[Jerry Wyss]

Oop's , your talking about I/B engines, O.S. makes a nice looking one for the VZ-M, haven't used one though.