Posted by Mark on January 24, 2003 at 23:02:18:
In Reply to: Re: Re: 56j design flaws posted by 56j componants on January 23, 2003 at 13:13:08:
ACTUALLY:
The fourth valve on the 5xJ is an even more ingenious (and economical) hat trick:
The fourth valve itself IS a stock .687 bore King 4th valve, not a .734 Conn grafted on!
If you have the chance to see the 5xJ up close, you'll see the 4th valve branch tapers (via a special tapered knuckle) up to the larger bore, then steps back down to finish the trip thru the valve, and steps up again after the valve, enroute to the main slide. This dual bore trick is a dirty little secret too good to be kept quiet.
the "trick" works, because the changes are subtle and executed smoothly enough to avoid turbulence. Hey, look at what goes on inside any piston valve airways - lots of bumps from adjacent airways; no problem. Just tiny air velocity changes, not too turbulent, which average out to be negligible. Heck, they probably even help "flexibility" and keep things from being too slotty.
Chuck: replumb a straight section or two those King 4th valves with .718" tubing (.679 outer slide stock)- no tooling req'd. Just chamfer the .689 inside ends thin (more like .7xx) where the change takes place. This was done on my re-valved York BBb for only a foot or so. It makes a BIG difference.
I'm bettin' they used .734 bore on the 5xJ' s simply 'cuz the crooks were readily available from the 20K. Darn practical.
-- Mark "If it blows like a .734", and it sounds like a .734..." Mazak