super cool

I learn so much here.

Thanks, I'm learning too

Hamilton Standard plant assembling their two position variable pitch propellers that briefly dominated the world, 1940
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Comparing the photos above you'll see that the hydraulic cylinder on top of the hub and counterweights attached to the blades have changed positions, and you might notice the blade pitch has changed a little. Like the first photo, when the propeller is spinning centrifugal force on the disc shaped counterweights force them outwards, which causes the blades to rotate to a coarse pitch. There's a cam between the counterweights and the hydraulic cylinder, which the pilot can pressurize with engine oil.  When pressurized the cylinder extends and the cam forces the counterweights back in which rotates the props to fine pitch, like the second photo.

Counterweights out, cylinder is relaxed, coarse pitch
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Cylinder extended, counterweights forced in, fine pitch
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The counterweight variable pitch prop has the advantage of being relatively simple, but it has just the two positions, there was no way to set an intermediate position.  That left a lot of efficiency at intermediate pitches unrealized, increasingly so as the difference between min and max aircraft speed increased dramatically.

1938 saw the introduction of the next generation of Hamilton Standard propeller, the Hydromatic, which shared basic concepts with its predecessor but was much more complex and expensive to manufacture.  Nevertheless performance and safety advantages were compelling and the Hydromatic became the most common propeller of US frontline combat aircraft during the war.  Hamilton Standard and its three US licensees (appliance manufacturers Frigidaire and Nash-Kelvinator and typewriter and 1911 manufacturer Remington-Rand) shipped more than 530,000 complete Hydromatic propeller assemblies during the war.  Additionally they produced many spare parts and a minimum of 86,000 spare blades, and those are like as not grossly undercounted.  De Havilland Propellers, which was established in 1935 as a division of the British aircraft manufacturer when they acquired the license to manufacture then state of the art Hamilton Standard two position variables, also acquired the license to manufacture Hydromatics and equipped much of the RAF with them.

The Hydromatic made the two position variable obsolete in combat by giving the pilot both manual and "constant speed" automatic control over his exact prop pitch, which improved any aircraft's performance remarkably and introduced several revolutionary safety features (this graphic might be based on an early P-47, I'm not sure, regardless you get the general idea)
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The Hydromatic hydraulic cylinder is easily identified (here painted red, F4F Wildcat)
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Extremely simplified diagram.  The cam has greater range of motion than the old variable and is no longer exposed (having actually been moved inside the hydraulic cylinder, not in between as depicted).  Engine oil is fed into the hydraulic cylinder as before, but now there's also back pressure from engine oil fed into the other side of the cylinder by a governor mounted on the engine.  Balancing the two forces locks the piston which locks the cam which locks the blades at any pitch, while reducing or increasing oil pressure from the governor moves the piston which rotates the cam which rotates the blades
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Non-simplified cutaway is remarkably unsimple.  The governor, at top left, is a hydraulic pump powered by the engine's reduction gear and also uses that to sense RPM.  The governor increases or decreases hydraulic pressure to change the prop pitch as required to maintain steady RPM as set by the pilot.  
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The base of the blade got more expensive
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So did the hub
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If you have to ask what the cam and hydraulic cylinder assembly cost you couldn't afford one
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530,000 American made cams plus spares
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Rough forged spiders
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"Electro limit gauge" QC station checking finished spider tolerances.  Apparently spring loaded pins close a circuit and illuminate the warning board when over or under tolerance
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Assembling a Hydromatic
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De Havilland's manufacturing process for the Hydromatic was necessarily similar to Hamilton-Standard's, fortunately I found a short 1940 documentary of DH's Hydromatic factory that captures many of HS's manufacturing steps on film

I work a job where I get to see alot of old family photos. Ill try and start posting some of the various ones we scan in.

Below is a friend of mine who was stationed in Europe after ww2.

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Different man Mr. Jordan in Europe in ww2 unk location (assuming Rome)

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The Hydromatic was the first "feathering" propeller, a major safety improvement.  When the propeller stops in flight it stops producing thrust and instead only a lot of drag when left at its usual pitch.  Letting the prop "windmill" without power doesn't eliminate all drag and the vibration in the engine could get violent enough to rip the engine off of the aircraft. The Hydromatic range of pitch control meant that for the first time the prop could be turned from broad side on to edge on to the direction of travel, all but eliminating drag.  The practical result was that a transport or bomber with one or more engines broken down or shot out that would have crashed in enemy territory or at sea with any other prop now had a good chance to return to base and land intact.

First public demonstration of feathering in 1938, DC-3.  The Hydromatic was credited with a significant reduction in the civilian airline accident rate
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B-24 heading home with one smoking (bottom right) and one feathered (top left)
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RAF Lancasters were equipped with 13' DH Hydromatics, here one boldly demonstrates them with a low pass while feathering 3 engines simultaneously
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Distinctive prop hub found at an old Lancaster crash site in North Wales
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After the war the Hydromatic was taken another step further, with propellers that would rotate blades beyond feathered and into a reversed position to provide braking reverse thrust to reduce stopping distance during landing for multi-engine civilian planes.  First unit installed in 1946.

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Thanks.  I was unaware of the 37 mm AT gun having an optical sight.

You're welcome.
 
The gun commander was also issued the Binocular M3 type EE to spot and range targets and spot the fall of shot and correct aim, a slight modification of standard pre and early war US M3 field binoculars.
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Standard M3 binoculars had a reticle etched with horizontal mils for adjusting crew served weapon fire left or right and vertical ranging tics for providing infantry with artificial aim points for indirect fire, scaled for the ballistics of the 30-06 Springfield and Garand rifles and Browning MG.  (I have some Japanese made commercial binoculars from the 1960's or so that are almost identical to these, less the reticle, they seem to have been produced in large numbers under multiple brand names post war)
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Original M3 reticle with 30-06 indirect fire ranging tics
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Here's a summary of the indirect fire procedure written better than I can, found here  https://www.cloudynights.com/topic/630490-m3-binocular-reticle-explanation/

"The vertical scale on the right is graduated to 2,000 yards, read top to bottom. This was used to determine the proper sight setting for .30-06 caliber weapons. The method is complicated, and the scale is not useful unless intending to utilize indirect rifle or machine gun fire. I will detail it in the last paragraph. The horizontal line on the bottom is marked in 10 mil increments, 1=10, 2=20, etc., to determine adjustment for direct fire from larger weapons such as mortars, rocket launchers, tanks, artillery, etc. The two horizontal lines in the middle above the bottom line are 5 mils apart, and are used as a 'crosshair' or a reference point for placing over the target. The scale on the left is 5 mil increments to adjust indirect fire vertically.
Infantry would not have used the binoculars in place of the sights on their rifle, the 2,000 yard scale was used to determine the proper sight setting for infantry weapons to fire on a target that cannot be seen clearly at long ranges. The scale directly coincides with the impact point of a .30-06 bullet accounting for the parabolic arc of the bullets flightpath at a known distance. (There is a separate formula for determining distance/size of target/mils, I will post that separately.)   Say you are ahead of your infantry platoon and observing a machine gun nest in WWII. Your platoon is 900yds from the nest, but cannot see it. How can they fire on a target they cannot see? By using the 2,000 yard Eames Scale (that is what it is called). You take the distance your platoon is from the target nest, 900yds, and put that tick mark on the scale directly on top of the target. From there, look up and down the scale and find an object which is visible to the platoon, let's say the base of a tree on the 600yd tick, and have the platoon set their rifles to 600yds and fire at the base of the tree. They are firing at an artificial target. Due to the parabolic arc of the bullet, even though they are aiming at the tree with 600yds set on their rifles, the bullet will hit the target machine gun nest at 900yds."

Binocular M3 type EE reticle example, similar but with ranging tics scaled for 37mm ballistics; the gun commander has observed a row of heads of enemy infantry sticking up over the top of a trench 900 yards away, beyond the lip of an intervening ridge.  He estimates this is their position relative to the gun, hidden by the ridge, and holds the 900yd tic on the center of their position.  He doesn't want to move the gun to the lip of the ridge and expose it to enemy fire in order to aim directly, so he looks up and down the scale to find an artificial aiming point visible to the gunner.  He directs the gunner to set his range for 1800 (which is not the actual range) and hold on the bottom fence wire (not the actual target), starting 10 mils right of the bottom of that middle fence post, walk your fire back and forth 20 mils left and right.
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The indirect fire ranging tics disappeared from US binoculars during the war, perhaps phased out when experience found it rarely used and training was sharply abbreviated
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There was a detailed indirect MG fire thread here recently: https://www.ar15.com/forums/General/The-Lost-Art-of-Machinegunnery-/5-1395935/?page=1

Unlike most Hurricanes, RCAF night fighters (see exhaust flame glare shields just forward of the cockpit) were equipped with Hydromatics
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Experimental ski Hurricane
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Taxiing accident January 1943
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A full-scale wooden mockup of the Tiger II.

In 1940/41 Britain bought 600+ scoped and silenced Winchester Model 74 semi-auto .22's (front row left) as close range sniper rifles for Auxiliary Units, organized by the SOE as stay behind guerrillas in the event of invasion
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Edit: scanned page below is from "OSS Special Weapons and Equipment: Spy Devices of WWII" by Keith Melton, said to be a reproduction of the original SOE manual found in British Archives, text thought to be genuine but illustrations thought to be modern (Thanks Riter)
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Edit: Model 74 in the Imperial War Museum https://www.iwm.org.uk/collections/item/object/30029779
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Most of that stuff looks to be American.

I've been on projects that involved digging up old WWII dumpsites on Guam and Saipan and most had mixed US/Japanese stuff.

That’s pretty cool.  Of course, they probably all ended up locked up from being put on safety after being decocked.

RAF Lockheed Venturas from No. 1 Operational Training Unit practice flight with feathered Hydromatic props
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"24's Get Back"  Lots of B-24 feathered prop flight and landings, including two feathered on the same side.  Includes advice like using crew parachutes to slow the aircraft if the brakes are out, and shooting out your own main gear tire on one side if the enemy has shot out the other side


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B-29 with bird plug, Hydromatic with rubber "cuffs", which turned the rounded shanks into cooling fans
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Douglas Aircraft Company Plant, Long Beach California
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Miss Annette del Sur publicizing a salvage campaign at Douglas
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My Mom looked a lot like that lady when she was that age.

Maintainers study intimidating cutaway model.  The Hydromatic was much more complex than earlier propellers
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Prop replacement A-frame on an English airbase
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B-17 Hydromatic overhaul, primitive airstrip in the New Hebrides
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Note the carry handle threaded onto the hydraulic dome
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Servicing a De Havilland Hydromatic on a Spitfire, dome off and oil all over the place, 1944 New Guinea
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B-17 propeller installation

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The Hydromatic was considered highly reliable, but they could come apart from battle damage or experience overspeed, a failure of pitch control that causes the prop to turn to fine and rotate at increasing RPM until coming apart, or tearing the engine apart.  The propeller would then depart the aircraft violently, sometimes rejoining the aircraft an instant later and tearing into it.

Blown off by flak hit
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Overspeed propeller on takeoff hit the cockpit and pinwheeled over, breaking the pilot's wrist
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Propeller severed the pilot's leg
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After bombing Tokyo B-29 Holy Joe flew 17 hours back to Saipan with two engines out on the same side.  A propeller came apart and slashed the fuselage badly and speed fell to 150 knots.  During a crash landing the half severed nose was twisted off of the rest of the aircraft.  Remarkably there were only a few minor injuries among the crew, but one man was badly injured on the ground and another killed
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My uncle flew B-17s, said the engines were very reliable.  Later he flew DC-3s that used the 1820 engine.

I talked to a B-17 mechanic, he agreed but said the props gave some trouble.

this is the most interesting thread ARFCOM has ever had

I have a pair of those that might actually belong to the Army. 😇

1st photo has a Mosquito on the right.

More propeller failure damage - of course these are the ones that made it back, surely there were some that went down with pilots killed, or controls severed, or folded in half from catastrophic fuselage structural damage.

"Ray Peters from Monticello IA was the co-pilot on this B-24, The "Fishshack" when it was hit in the no.3 engine. They couldn't feather the prop and it eventually snapped off careening into the fuselage just below Ray's feet. The ground crew had added extra steel plating to the floor of the cockpit a few days before this happened which saved Ray's feet. They landed in Belgium with two engines and no loss of life."
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Failed Catalina prop speared the cockpit.  Don't know how bad it was for the pilot, but probably pretty bad
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B-17F of the 385th BG after 1943 Schweinfurt Raid
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B-29 damage similar to what decapitated Holy Joe, Iwo Jima
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Naturally there weren't a lot of single engine survivors of prop failure, but something has gone seriously awry on this P-47 for Republic test pilot Kenneth Jernstedt
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Preceding the Variables and Hydromatics were Hamilton Standard's Ground Adjustable propellers, which could be set to fine or coarse pitch to advantage either climbing or cruising by the ground crew with the engine off, but could not be changed in flight.  In WWII some US utility aircraft and trainers (notably the N3N Canary naval basic trainer) and the P-26 Peashooter fighter of 1932 vintage used them, so the Ground Adjustable just managed to see combat in WWII when Peashooters at Clark Field in the Philippines shot down several Japanese planes in the opening days of the war
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Joseph P. Kennedy Jr. poses in flight school with an N3N Canary trainer
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Float Canary
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Marine Corps glider training tow Canary
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One of the biplane flying boats, USCG Hall PH-2 or 3 I think
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Mal, thanks for posting these photos. I came across the photo of Bill Lee's 1911 with a bullet hole in it and felt like i had to respond with a story about that gun. My understanding is that Bill returned home to Chicago after the war bringing along that pistol as souvenir. At some point it was stolen from his or his family home (I believe from a home in Chicago). By now Bill had joined the NYPD and working to keep the streets of NYC safe. One of his partners of several years at the NYPD was a gentleman by the name of Sid. I met Sid when i was a young boy after he retired from the NYPD and moved in across the street from my family. Later in his career Sid was working at the NYPD armory near City Island when two detectives walked in with a damaged 1911 they taken from a perp and wanted to know if it could be repaired. Sid told me as soon as he saw it he knew exactly where that gun had come from. He removed the slide, gave it to the detectives and told them there was nothing he could do.  He gathered up the remaining undamaged parts and sent the pistol to Colt with note explaining the circumstances. Colt rebuilt the gun sent it back to Sid whereupon Sid returned to Plt. Sgt. Lee.

After Bill passed away Sid ended up with some of Bill's things, to include that pistol and the same photo you posted here. He showed me the pistol and photo about 20 years ago. Sid has since passed away. I'm not sure where the pistol is now, but it's out there somewhere.

Funny that prop work on a B-17 and a C-130 is not all that different. But then again there was only a few years between them

@LimeRickey That's awesome!  I'm sure that meant a hell of a lot to Lee. Thanks for that.  Funny how these things can turn back up unexpectedly.  


Halifax Wireless Operator, whose chair is visible in the hole, contemplates close shave
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I'm not sure that USAAF or USN even bothered very much, with so many spares being produced, but bent forged aluminum propeller blades could be straightened out after an accident or crash and RAF Maintenance Command repaired them throughout the war.  Looking over damaged Hydromatics, December 1941
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Disassembly of a Variable
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May 1945, blades before and after refurb
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I can't find photos or a description of the actual straightening operation, perhaps roughly flattening them with a hydraulic press then careful hand work with various mallets, anvils, and templates?  Somebody working at a metal shop would have a fair idea.  Propeller blade repairmen take lunch at their workbench
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Refurbed Hydromatic parts being polished prior to reassembly in a RAF repair shop
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British state civilian airline BOAC flew into harm's way at times, unarmed, and had their own repair facilities
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@Mal_means_bad

Had to take these photos for you during a recent visit to the Palm Springs Air Museum

A26 and its props (I believe placard said this bird never fought)

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PBY5 just needs some minor work to start flying again

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Bent props would have almost certainly had to have gone through some amount of heat treating and annealing after straightening, to ensure they wouldn't just shatter once they spun up the first time.   When aluminum (and most metals for that matter) are plastically deformed like that there is a lot of compromise in its strength.   Fixing that plastic deformation by plastically deforming again (back to the correct shape) further weakens it.   To get the strength back you'd have to take the metal back  through heat treatment to get the grain structure right again to ensure it has the right strength, and likely a pretty significant magnetic partical inspection to make sure there weren't cracks.

My bet was by the time they got that worked out we had enough production capacity to where refurbished blades were probably kept as emergency stock or maybe even just for one time ferry use or something like that.

Thanks!  Interesting collection.  If I were wealthy I would have a Catalina outfitted as a flying yacht - a couple of people did that in the 50's.




You're absolutely right about heat treatment, I checked and they did

Wiki "During World War Two, Morris Kestelman served as a full-time air-raid warden and also drew scenes of workers at an aircraft repair factory. One of these drawings was subsequently purchased by the War Artists' Advisory Committee and is now held by the Imperial War Museum."

IWM art collection, "Blade Heat-treatment Cage"
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😎   Somewhere out there my material science professor from 20 something years ago is happy I paid attention!

Awesome story.

The armory you're referring to is at Rodman's Neck, the NYPD's outdoor range. It's right by City Island and Orchard Beach in the Bronx. Cops from all over the city come to qualify 2X annually there, and ESU and other high speed units train regularly there.

The armory building has quite a few interesting firearms, mostly taken off the streets over the years or surrendered by Grandma after Grandpa died. I had the opportunity to handle a bring back StG44 and FG42, among many other interesting things, in a previous life.

Welcome to the site.

Overflowing RAF propeller warehouse
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Four and Five-bladed Rotol props in stock
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Five-bladed props probably for hot late war Griffon powered Spitfires like the XIV - Spitfires were flown in combat in WWII behind two, three, four, and five bladed propellers as engine power leapt forward
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A pair of three-bladed contrarotating Rotol props were flight tested on Spitfires in late WWII and equipped Seafires deployed on British carriers from the late 1940's to 1951
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Austin K6 6x4 lorry
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Transporting replacement propellers locally with vertical racks on "Queen Mary" airplane recovery flatbed trailers
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Broken wood props removed from hubs at a Rotol factory
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Punjabi craftsman repairing a wooden propeller blade in a workshop in Britain
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Woman repairing a damaged Rotol hub
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Maintenance Command propellers crated for shipping
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More fixed pitch wood propeller Hurricanes; one of the first off the production line
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Mechanics' trainer with the spinner nose off displaying the bolt pattern
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Yamashiro, IJN

Kawasaki Ha40 discovered

Wasn't that engine a copy of the DB-601?

I've got no idea, though the Japanese definilty copied stuff -- not to say they are like the Chinese, because even back then they came up with original ideas.

Thought it was an interesting story and hadn't heard of many liquid cooled aircraft engines back in that day.

Mal probably knows all.

Yes

I
I believe it was licensed build.

I would love to see a Ki61 get restored and back in the air. Its a pretty airplane.