ALL THINGS BIG BOY

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Re: UP Big Boy Steam Turret: Vents?

Postby joeburgard540 » Tue Oct 12, 2010 7:09 pm

I know this answer is a long time in coming...but here you go. :-D

The two plumes of steam coming from near the steam turret casing are the exhausts from the Pyle-National turbo-generator and the cold water centrifugal pump (mounted underneath the fireman's side of the cab). The centrifugal pump (Elesco type TP) pumped water from the tender to the exhaust steam injector (located underneath the running boards on the fireman's side of the smokebox).

Cheers
Joe
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UP Class 4-8-8-4 "Big Boy" Maximum Cut-Off

Postby joeburgard540 » Tue Oct 12, 2010 7:14 pm

Does anyone know for certain what the maximum cut-off was for the Big Boys in both forward and reverse (if the figures are different)? I'd assume it would be about the same as Challenger #3985 since they both use the 12" ALCO Type "M" power reverse and had very similiar designs.

I just revisited #4018 in Dallas, but the cab is locked so I couldn't see the reverse quadrant. I asked one of the employees, but he didn't have the keys.

Are any of the reverse quadrants clearly visible on any of the Big Boys that are on display?

Thanks,
Joe
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Re: UP Class 4-8-8-4 "Big Boy" Maximum Cut-Off

Postby Typewriters » Wed Oct 13, 2010 4:06 pm

Cutoff on the UP 4000's was 81% maximum, forward - haven't found a figure for reverse yet.

Comparable figures between the 4000's and the 3950-3969 include lap, lead and overall valve travel. RME lists the 4000's as having been equipped with ALCO Special Type H reverse, and the 3950's with Type H.

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Re: UP Class 4-8-8-4 "Big Boy" Maximum Cut-Off

Postby joeburgard540 » Wed Oct 13, 2010 6:59 pm

Thanks Will, nice to know my figures correspond. Just curious as to what source you got that from? Also what is RME?

I drew some Zeuner diagrams for full gear (hand drawn and CAD) based off the info on UP drawing 585 CA 30809, the valve diagram:
Valve Diameter - 12"
Valve Travel - 7"
Steam Lap - 1.375"
Lead - 0.25"
Exhaust Clearance - 0.125"

Results:
Lead Angle - 27.7 degrees
Cutoff - 81.6%
Release - 93.4%
Compression - 4.86%
Admission - 0.15%

As a side note, UP drawing 683 CA 31236 dated 5 August 1944 gives the Power Reverse Gear as the 12" ALCO Type "M". This is for locos 4-8-8-4 #4000-4024 and 4-6-6-4 #3930-3999.

Cheers - Joe
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Re: UP Class 4-8-8-4 "Big Boy" Maximum Cut-Off

Postby Typewriters » Thu Oct 14, 2010 8:03 pm

That's all from my brother's library, specifically the Gregg reprints of specific articles from RME or Railway Mechanical Engineer, which for those unfamiliar was the real biblical trade paper as far as new steam locomotive construction was concerned. I don't know why your drawings list "Type M" and RME states "Special Type H" unless they're one and the same with two different (ie earlier and later) designations.

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Re: UP Big Boy Steam Turret: Vents?

Postby joeburgard540 » Mon Jan 17, 2011 12:49 pm

My bad...I misread your question and to clarify. The two steam plumes on the turret (just ahead of the cab) are the exhuast for the cold water pump and the Nalco Automatic Blowdown. The third plume of steam nearly always seen is from the Pyle National turbo-generator (ahead and on the left or fireman's side of the turret).

Joe
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Big Boy

Postby tv737 » Mon Jan 27, 2014 8:33 am

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ALL THINGS BIG BOY

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