200A and 202 reproduction
frames back
in stock.

TwoCanoes

In a recent thread regarding a stove that would not shut down (https://www.colemancollectorsforum.com/post/new-restoration-tank-not-shutting-down-10676554?pid=1312842417), I suggested, ‘The valve has double-start thread.  Back the packing nut out and unscrew the valve being careful to feel when the stem releases from the female thread.  Turn the valve stem 180 degrees and thread it back in.  I've had this happen twice, once on a stove that wouldn't shut off, and once just a couple of days ago on a lantern that wouldn't shut off.’

   Rob (Dubblbubbl) asked in response, ‘Help me out here, starting the valve stem 180 out does what exactly?  Is this a work around for a worn valve tip?’

   In answer to Rob’s question, I say, “I don’t know.”  A search for double start thread on this site reveals discussions of double-start thread in the past, primarily explanations of the how and why of double-start threads on the valves.  So, my question is the same as Rob’s.  In both of the cases I’ve dealt with, the needle didn’t look bad – I couldn’t get a good look at the seat, but if it had a nick, how would a 180 flip of the needle help it seal?  Do the female threads terminate within a half-turn of the valve closing?  [Edited:  This last question, I think now, is unreasonable.  The threads start at the same elevation so they'll come to a stop at the same depth, right?]   I suppose one thing I should do is take a properly functioning valve, turn it 180 degrees and see whether the valve then refuses to shut off.  Any of you engineers care to comment?  Thanks.

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Majicwrench
I'm no engineer, but I have always cast a wary eye at this way of "fixing" the issue.  If it works for you, great, but the  valve is the same no matter which thread you start on.
Looking forward to more info...
Keith
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Dubblbubbl
Gonna be watching this thread with interest.
Rob in NC
MilSpecOps Syndicate #1962
Coleman 275 Appreciation Syndicate #1962

Sometimes we are the windshield, Sometimes we are the bug...
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outlawmws
I don't think I've seen any double threaded pump stems or anything else on a GPA with double treads.  While surely double threads exist, its rare anywhere, other than maybe jar lids.

Pics?
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Coleman Blue's 243's #341 - 275 Appreciation Syndicate member 0242
FAS #001 Confusing Future Generations of Collectors, One Lantern at a Time!

“A Human Being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, give orders, take orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook  a tasty meal, fight efficiently, die gallantly.  Specialization is for insects.”            - Lazarus Long


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TwoCanoes
outlawmws wrote:
I don't think I've seen any double threaded pump stems or anything else on a GPA with double treads.  While surely double threads exist, its rare anywhere, other than maybe jar lids.

Pics?

First photo is a valve from a 200A from 1960.  Second photo is one thread start.  Third photo is thread start 180 degrees from Photo #2. DSC02006.jpg  WIN_20200906_11_03_58_Pro.jpg  WIN_20200906_11_04_17_Pro.jpg 
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outlawmws
I can't say I've had to many valve stems out, but I sure never noticed one being double threaded!
[Logo%20Outlaw-half] 
Coleman Blue's 243's #341 - 275 Appreciation Syndicate member 0242
FAS #001 Confusing Future Generations of Collectors, One Lantern at a Time!

“A Human Being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, give orders, take orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook  a tasty meal, fight efficiently, die gallantly.  Specialization is for insects.”            - Lazarus Long


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outlawmws
Thinking on this I know whenever a thread is loaded,  The load is placed on the leading threads and they upset slightly under compression.  with a double I could see one taking more load that the other, making the load imbalanced? 

I'm sure  the original engineers probably thought they would be better balanced with the double thread, but that assumes they were perfectly 180 to one another.  Probably pretty hard to do in practice.  

With wear over time this could get the thing needing to be in the same placement orientation, and if reversed making the valve needle no longer concentric.  This could vary from one lantern to another, so some might display this issue, while others not.  

My 2c worth...
[Logo%20Outlaw-half] 
Coleman Blue's 243's #341 - 275 Appreciation Syndicate member 0242
FAS #001 Confusing Future Generations of Collectors, One Lantern at a Time!

“A Human Being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, give orders, take orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook  a tasty meal, fight efficiently, die gallantly.  Specialization is for insects.”            - Lazarus Long


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Gunhippie
The needle end of the valve shaft and the seat in the valve wear in together. Getting the stem off 180 degrees upsets that wear pattern. You chances of getting it right are 50-50.

I've fixed a couple of leaking valves this way, thanks to the advice of folks here. The double-start threads aren't obvious at all.
It's priceless until someone puts a price on it.
Walk a mile in a man's shoes before you criticize him--then you're a mile away, and he has no shoes.
Texan's last words: "Y'all--hold my beer--I wanta' try sumptin'."
Timm--Middle of nowhere, near the end of the road, Oregon.
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Rfieldbuilds
Have you tried polishing the end of valve stem with some very fine wet dry? The tapered part, not the point.  
Randy
QL #15, Slant Saver #59, #0269 Turd Hurdler, #0269 Mil Spec Syndicate, Coleman Blues 243 #0269, BernzOmatic Appreciation Club #072, and a few others too.
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TwoCanoes
Have you tried polishing the end of valve stem with some very fine wet dry? The tapered part, not the point.  

I've done this with the needle on a leaking air stem (air stems have single-start threads).  I was able to reduce the leakage, but not eliminate it.  I'm sure I could have reduced the leakage further, but I ran out of patience.
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Gunhippie
I have several tricks for polishing the seating area of a valve shaft--or just building it up with solder--but if all it takes is turning the stem 180 degrees to match the orientation it wore in at, why bother?
It's priceless until someone puts a price on it.
Walk a mile in a man's shoes before you criticize him--then you're a mile away, and he has no shoes.
Texan's last words: "Y'all--hold my beer--I wanta' try sumptin'."
Timm--Middle of nowhere, near the end of the road, Oregon.
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Deanofid
outlawmws wrote:
Thinking on this I know whenever a thread is loaded,  The load is placed on the leading threads and they upset slightly under compression.  with a double I could see one taking more load that the other, making the load imbalanced? 

I'm sure  the original engineers probably thought they would be better balanced with the double thread, but that assumes they were perfectly 180 to one another.  Probably pretty hard to do in practice.  

With wear over time this could get the thing needing to be in the same placement orientation, and if reversed making the valve needle no longer concentric.  This could vary from one lantern to another, so some might display this issue, while others not.  

My 2c worth...

Coleman used this double start thread from the time of the first instant start lantern until the first schrader valve lantern.  Some 40-ish years.  A multi-start thread is normally used to increase lateral movement along the thread axis.  When Coleman wrote on the valve direction disc that they wanted you to open the valve all the way, they really wanted you to open the valve all the way, so they used a double start thread to cut the knob rotations in half. 

Other thread counts go up to six, for a very fast movement of the threaded item, and also for load bearing threads like acme work driving threads at a high lateral movement per rotation ratio.  It's a pretty old use of increasing movement vs power need.
Dean -Midnight Kerosene Ritualist--http://www.deansmachine.com  ICCC #1220.   275 commiseration #0018.
"In Him was life, and His life was the Light of men."  John 1:4
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