Pratt & Whitney 12 x 30 b, factory drive sheve specifications?

Greetings to all,
I've been lurking on this forum for a while. You folks are a gold mine of valuable information. Thank you.
Having recently acquired a serviceable P&W b lathe, I finally have some iron worthy of consideration.
The lathe has been modified from the original pulley drive, set up to double the RPM's. The original G.E. 3 hp motor has a A50B54 (5.750 O.D.) 2 groove B belt sheave. The driven sheave is a A46B50 (5.375 O.D.) sheave. Judging by the operators manual, It looks like the factory set-up was for a 5 groove sheave with the driven sheave having an O.D. of 8". Would anyone here have the specifications for the original set-up? I also have a Clausing 100 lathe for the small diameter, higher RPM work, and would like to return the P&W back to the original speed range and torque capabilities (conforming to specifications of war board). I am also scrapping of layers of gray/green/gray paint, and constructing a 7.5 hp phase converter following Fitch William's excellent recipe.
Thank you all for keeping American iron up and running.

alittlerusty said:

Greetings to all,
I've been lurking on this forum for a while. You folks are a gold mine of valuable information. Thank you.
Having recently acquired a serviceable P&W b lathe, I finally have some iron worthy of consideration.
The lathe has been modified from the original pulley drive, set up to double the RPM's. The original G.E. 3 hp motor has a A50B54 (5.750 O.D.) 2 groove B belt sheave. The driven sheave is a A46B50 (5.375 O.D.) sheave. Judging by the operators manual, It looks like the factory set-up was for a 5 groove sheave with the driven sheave having an O.D. of 8". Would anyone here have the specifications for the original set-up? I also have a Clausing 100 lathe for the small diameter, higher RPM work, and would like to return the P&W back to the original speed range and torque capabilities (conforming to specifications of war board). I am also scrapping of layers of gray/green/gray paint, and constructing a 7.5 hp phase converter following Fitch William's excellent recipe.
Thank you all for keeping American iron up and running.

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Been close to fifty years, so I could be wrong...

The A50 and B54 are probably the effective pitch-line diameters - the average point of where a Vee belt transfers power - on sheaves made for use with either of "A" section or "B" section belting.

Same again for the A46B50 with "A" at 4.6" and "B" at 5".

An old Browning or Morse catalog had all that sort of info in the calculations pages.

Gates and competitors probably have it online these days.

If you know the nameplate RPM ranges for the P&W, you can use those calculators and tables - not the "OD" of the sheaves - to select the correct mate. Or near-as-dammit.

On the 13, which the 12 was derived from, the input pulley was flat and 8" dia. The input pulley speed was 600 for a top end of 525 - but these older Model B lathes used 1150 RPM motors.

To turn the input pulley at 600 with a 1750 motor you need a ratio of close to 2.92 to 1. Gates, in their Heavy Duty V-Belt Drive Design Manual (1976) suggests A section belt and 3.6 and 10.6 pitch dia. sheaves for 595 RPM

http://pounceatron.dreamhosters.com...ttwhitney-circular402-model-b-lathes-1936.pdf

Thanks to Greg Menke for hosting this for me

Thank you
I will punch in the numbers to calculate the pitch diameters. The tag on belt cover calls out 600 rpm and the G.E. motor is 1150 rpm. Those double V, B size belt pulleys are not a good solution. The motor pulley hangs out at the end of the motor shaft to align with the driven pulley. which is limited by the depth to the bearing housing by being a tapered sleeve mount. I will pull the pulley off the motor shaft (also a taper sleeve) and measure the length of where the original pulley mounted. It is just an educated guess that the original pulley set was 5 belted sheaves. I count that many from the P&W operators manual drawing. The 8" pulley called out in the same drawing would mount deeper and actually shroud the bearing housing diameter to properly align with the motor pulley. Looking at what is available should give me a pretty good guess as to if the original 5 V pulley combo was A or B belt size.

3.6 and 7.0 in same book , A section, for 1150 RPM and 598 RPM

alittlerusty said:

Thank you
I will punch in the numbers to calculate the pitch diameters. The tag on belt cover calls out 600 rpm and the G.E. motor is 1150 rpm. Those double V, B size belt pulleys are not a good solution. The motor pulley hangs out at the end of the motor shaft to align with the driven pulley. which is limited by the depth to the bearing housing by being a tapered sleeve mount. I will pull the pulley off the motor shaft (also a taper sleeve) and measure the length of where the original pulley mounted. It is just an educated guess that the original pulley set was 5 belted sheaves. I count that many from the P&W operators manual drawing. The 8" pulley called out in the same drawing would mount deeper and actually shroud the bearing housing diameter to properly align with the motor pulley. Looking at what is available should give me a pretty good guess as to if the original 5 V pulley combo was A or B belt size.

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What John said. "A" section. They are NOT "4L". A proper "A" transfers power much better - even as a single.

From earliest days, "A" section belts have been made to a tighter factory tolerance so they "always match" and do not need hand-selection to be used in sets.

Good to NOT mix old and new however, as they do still wear and stretch.

Cast-Iron, (grips better..lasts longer) AND NOT shiney-wood, plus taper locking mounts are righteous, BTW. I like QD, but any of the better ones beat plain bore.

I appreciate the replies. I'm going to have to get the motor back on the lathe to check out the alignment before proceeding any further. It looks like the web was offset on the original driven sheave, and the 8" diameter sheave allowed clearance to "Shroud" the 3.875 diameter x 2.75 protrusion of the bearing housing (dimensions approximate) projecting from the rear face of the guard. The motor shaft shows were the original sheave mounted about 2.437 to 2.5 deeper on the shaft than the QD bushing now on it. The QD bushing takes up all of the clutch shaft stub, from the shoulder to the nuts out front. They were pushing it to get the QD bushing, 2 V sheave set-up to align. So, it looks like the ratio may be the easy part, shopping for the right fore and aft dimensions of the sheave face to web will be the kicker, and I haven't seen these dimensions called out on the spec. sheets.
Is there consensus that the original sheave set was indeed 5V, A belt?
Not that I'm dead set on originality, I just want this little beast to have it's balls back.

From the older 20" Model B. The flat belt days. The point here is that P&W DID NOT go down to the sheave store and buy pulleys - they designed and built what was needed. No such thing as taper lock bushings for them. You can be certain this practice was still prevailing in the vee belt days

alittlerusty said:

Not that I'm dead set on originality, I just want this little beast to have it's balls back.

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If so, life will be easier if you take advantage of PolyVee or MicroVee belting AKA "serpentine". And I mean "done proper-like" eg: with accurate grooves, not run nekked or inside-out atall.

Vee-count / belt width is arbitrary up to around the yard or meter in single-belt width the 'stock' is manufactured as. it then goes to "slitters' who slice to stock - or custom - Vee-count/width.

A single wide-enough, PolyVee/MicroVee belt and you have far more flexibility as to sheave positioning and mounting to the shaft, no need of matching separate belts, and pulley grooves so much shallower as to make sourcing material and crafting custom sheaves easier as well.

Research that as an option. It gets more grip into less width than a flat belt it otherwise resembles for its ability to stand reverse curves well.

Both PolyVee and MicroVee can - and do - work rather well. There'll be examples as close as whatever your car keys fit, where even the "skinny" ones are dealing with 5 HP total loads or so.

FWIW-not-much dept, eschew Gilmer and other synchronous belting. THEIR "pulleys" are de-facto gears, gain flexibility as to shaft centreline spacing, but otherwise must fit within tooth-count/diameter parameters just as a spur gear would, and need very good precision as to tooth form as well.

Thin Vee is a simpler linear exercise, far more forgiving, and you need no synchronization, anyway.

johnoder; Yes, you are right. The notion that I might have to turn my own has been at the back of my mind all along. Undoubtedly a bit costly in material, but a good maiden voyage for the new to me lathe.

Monarchist, I will certainly look into this, especially since I will most likely be conjuring up my own sheaves anyway. Thank you for bringing these belt types to my attention.

On this front, I'm thinking I'll scrounge some oversize V sheaves, turn them down and groove them for poly v. Hopefully I can shift the grooves laterally on the 8" driven sheave enough to allow bringing the motor sheave deeper on the shaft, while retaining my QD hubs.
Thank you, pardners, for steering me right.

alittlerusty said:

On this front, I'm thinking I'll scrounge some oversize V sheaves, turn them down and groove them for poly v. Hopefully I can shift the grooves laterally on the 8" driven sheave enough to allow bringing the motor sheave deeper on the shaft, while retaining my QD hubs.
Thank you, pardners, for steering me right.

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Lotta waste in that. PolyVee/MicroVee don't need a lot of depth.

One approach is a shiney-wood hub, "tire" shrunk-on of medium or heavy wall steel tubing, then grooved. Ditto modifying a flat-belt pulley. Shrunk-on tire if thin, directly grooved if thick enough.

Solid shiney-wood works, too. I just never liked its groove durability (NOT!) vs CI or steel, tiny-vee or legacy full-sized.

Take note that light-metal "serpentine" belt sheaves are uncommon under a motor vehicle hood. Most are pressed steel, some with a steel tire added.

Polymer idlers - or their bearings - may wear out. Much more rare for any of the steel sheaves to be worn-out, even by the time the vehicle heads for the crusher.

Monarchist, I hope "shiney-wood" hub does not involve the coffee table. Buying this lathe already has my Secretary of War on high alert. As the tattoo on her chest proclaims: "This machine conforms to specification of War Board". The lathe that is. Homeliness, robustness, and balls aside, the more I scrape and rub, the more she becomes my Baby B.

alittlerusty said:

Monarchist, I hope "shiney-wood" hub does not involve the coffee table.

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Just a personal preference. Such "shiney wood" - AKA Aluminium, AKA fuel for REDOX reactions - as I bother to work at all (not much..) is exiled to the sawdust-making side of the shop to be shaped with the near-as-dammit all-carbide woodchopping tools.

Useful enough stuff, shiney-wood is. I just don't care to work it whilst other folk do that better and I can still get decent hardwoods.