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Pratt & Whitney Model B Mechanical Problems

schaefjb

Plastic
Joined
Apr 29, 2016
Hello everyone,
I know these beasts have been addressed in prior threads, so if I am posting a question that has already been answered, please forgive me. I've got a 16X30 Model B that we picked up from the local General Electric plant here in Ravenna that I've been toying with for the last year. In the process of learning about the ins and outs of this old girl, I'm trying to learn the trade as well. I've got a background in welding and fabricating, but with my interest in the industrial arts I can't let such a broad and interesting field as machining slip by without me diving into it.

But I digress. I'm discovering a few issues with my Model B now that I've taken some trial cuts and I'm playing with it. The clutch is slipping when it's engaged and when it's disengaged, the clutch still drags enough to turn the spindle when there's no load on it. This machine is also the 16 speed model with the high-low range and direct-back gear configuration. When I'm trying to hit the lower RPM's, I don't know if it's because the clutch assembly is slipping but there is a nasty growl/clatter in the bottom end.

The gear head in me says that if things sound like they're going to fly apart, it's best to shut them down before they self destruct. In high range, things seem fine unless I'm running it at 750 RPM's. Due to the clutch slippage, it takes a minute for it to wind up to that RPM, but it will achieve it. I'm just hoping to get some insight into how to adjust the clutch and whether there might be other culprits for the noises at low RPM's. Any field experience the folks here have or owners manuals, etc. would be appreciated. I know they don't make them like this anymore, so I'd like to not grenade it. Thank you all for your help!
 
Clutch is non adjustable as near as I can tell and is contained in the small "gear box" low on back of head stock - its a "Johnson Clutch" whatever that was

Private message me your email address and I'll send some scans

Growls are likely gearing not completely shifted - maybe due to worn out shifting forks

Before you run it a lot you will have to make sure oil pump back there down low is actually pumping oil up to distribution manifold in top of head stock. If this has been neglected for years, most every thing in there will be worn out

750 is stepping on out for plain bearings. Normal 16" top end was 525

On edit - here is a "spare" for you

Pratt&Whitney lathe model B

Here is some 1921 info on the clutch - says it adjusts with one screw

Chilton Tractor Journal Vol VI No 1 - Google Books
 
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Thanks to Johnoder's scan of the drive clutch assembly, I've figured out how to adjust the clutch pressure so the clutch no longer slips when it is engaged. For some reason, however, when disengaged the chuck still spins slowly. I'm going to look into the possibility of adjusting the cone brake yoke to apply more pressure to it when the clutch is disengaged. The cone looks a little worn so I'm guessing the wear has introduced additional clearance into it that is causing brake slippage. I'll post my findings once I fiddle with it.
 
Thumbnail shows oil pump on 20". Its on the end of the shaft that the gear half way thru back of bed is on

Also shown is the distribution manifold way up high
 

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