The Tale of the RAF Museum Hendon's Hudson Turret.

[abaddon1]

Or... Miracles take a little longer.

One day, our Chairman... the late, much-missed Tony Southern, phoned me when I was disposals officer of the Cotswold Aircraft Restoration Group; and asked me whether I thought that we could rebuild a Boulton Paul Type C. Mk II mid-upper turret for the RAF Museum's Hudson.
The remains of two were languishing in deep storage at Cardington; and he had been approached to see if the CARG "miracles take a little longer" crew could turn the remains into something that they could display alongside the Hudson exhibit. The turret aperture in old lady's fuselage had been faired in; and the turret support ring had been removed; so this would eventually be a free-standing exhibit alongside her.

The first question was "Why not Cosford?" The word was that they were up to their eyeballs with far more important jobs; and some hero at Hendon had come up with the suggestion that CARG was a possibility.
A trip was duly organised to inspect the suspects.

The turret history was as follows:
When the Aussie fly-boys pensioned their Hudsons off; many were placed into storage at RAAF Richmond in New South Wales; and offered for disposal during 1946. Many were de-militarised for freight and flying school use which involved removing armaments and ancillary Military odds and sods. The two turrets in question had been recovered from their dumping site in the Outback where they had languished under the hot Aussie sun; being subjected to being pee-d on by Dingos and Kangaroos for many years.

The inspection at Cardington turned out better than anticipated. The cupola was relatively intact; but missing most of its perspex. The gun mounts, frame hoop; armour plates and base plates were intact; one of them even still had the ammo bin and attached fixings. It was only the rotation ring that was moth-eaten... but one good one could be made up from the two examples... (Oh, foolish optimism)... but more of that later.
In fact; the remaining fittings and fixtures... right down to the ammo box locations, operating table; seat and belt feed chutes were there in various states of dilapidation; albeit the feed chutes, although complete; were bakelite mouldings and were badly cracked and warped from sun exposure.

Tony glanced at me.
"Well? can your straighten them out?"
The first thought that flashed through my mind was:
"Bakelite? I've got as much chance of that as sprouting wings and doing a couple of low circuits of the airship shed!"
But, under the dubious gaze of the Cardington custodians, and with CARG's reputation at stake; I nodded tentatively.
Arrangements were then made to collect the remains and transport them to our workshops at RAF Innsworth.

To Be Continued.

 

[vikingBerserker]

Awesome!

 

[nuuumannn]

Marvellous! Looking forward to the rest. I see the Beaufighter nose section in the background.

 

[Capt. Vick]

Noice!

 

[abaddon1]

The Tale of the RAF Museum Hendon's Hudson Turret. Part 2.

Having trailered the turret remains back from Cardington to the workshop at Innsworth; our rivet bashers started to assess what needed to be done to the somewhat battered cupola, whilst I was stitched up with separating the gun mounts from the ring and frame assembly; and sorting out the whizzy bits as far as the hydraulics and electrics were concerned; with the terse comment:
"You work at Smiths Industries... (as it was named back then)... here's what we've got of the AP... sort out what's missing."
As it turned out; the hydraulics (Ram; pipework, etc) were in reasonably good condition; except for the pump which was very sluggish and difficult to turn. This was due to the fact that the system still contained hydraulic fluid which, as we later discovered, resembled a cross between toffee and treacle due to being baked for forty-odd years in the Outback sun.
The electrical wiring had succumbed in the usual way... the rubber insulation just crumbled away when touched.

Whilst I was checking and dis-assembling; one keen type (who shall remain nameless) decided to take it upon himself to separate the upper rotating ring from the lower fixed gear ring which was badly corroded. Before we could stop him, he found himself with the rotating ring in his hands, the fixed gear ring on the bench; and two hundred-plus 5/16th" ball bearings all over the floor. We recovered most of them; but fortunately, we had another ring assembly from which we could recover those that had rolled away to God knows where. Next time, when it came to splitting the rings it would be done over a stretched sheet!

Meanwhile; the rivet bashers were trying to remove the the stainless steel gun slot shutters; which proved to be a real fun game. They managed to save the rollers which allow the shutters to move smoothly against each other in the tracks as the guns are elevated and depressed; but the corroded retaining rivets (which were once, mild steel) popped every time they moved the shutters; causing the stainless retaining strips to slip between the said shutters and jam the system. Leaving them to cuss and blind about Boulton Paul's complex engineering finesse, we turned our attention to the Bakelite ammunition belt feed chutes.
Both of these have a curved, ninety-degree twist along the length of the chute from each gun mount circular feed aperture back to the ammunition slots above the five hundred-round ammunition boxes. (The Port chute twists anti-clockwise, and the Starboard chute twists clockwise.)
The alignment on both chutes was almost an inch out at the gun mount circular feed aperture when the ammo box feed slot was lined up with the lower end of the chute. These curved twists had started to untwist themselves as they expanded and warped under the Aussie sun; and the shaped end-caps that held the upper feed rollers had cracked open on both chutes. Fortunately, all the chute fittings were still in place.
So... what to do? First victim... the Port chute.

Thinks...
Bakelite is a thermosetting phenol formaldehyde resin... (Smart-ass)... and is virtually impossible to bond if it's under tension. "Under tension" didn't even come close to what was needed to be done to get the curved twist back. OK; so firstly remove the metal fittings before we really push our luck with my tenuous idea of how to deal with this.
Next; fabricate some thin 1/4"x 1" alloy bars to screw across the end-cap splits. This will support the end-caps when the desperate measures begin... they need to be desperate because there are no replacement chutes to be had.
Next; borrow a two-thousand watt heat gun that we used at work for heat-shrink tubing; take a deep breath, put on a pair of heavy gloves; switch on, and point at the area of the chute that needed to be re-twisted.

To various helpful mutterings of "You'll never do it" and "That's a bit bloody optimistic" from my fellow CARG companions; and, with the ammo box end of the chute firmly clamped in a soft-jawed vice, and the other end held in my gloved hand; we began to carefully heat the bakelite target area... too little heat, and nothing would happen; too much, and we ran the risk of blistering the surface. I began to gently add pressure in the direction we wanted the chute to twist... half expecting the sodding thing to go off like a hand grenade at any moment. Keeping the heat gun moving; I heated the entire area whilst carefully applying the pressure. At last, the chute began to move... slowly... painfully slowly. OK... that's enough... let it cool and stabilise. I gingerly released my grip; half expecting it to untwist back to the shape it had taken before we began... but, as it cooled it stayed exactly where I had managed to position it.

This course of action was repeated several times, over a period of about two hours; with trial fits each time that the Bakelite had cooled. Finally, the chute lined up. Now, it was time to repeat the process with the cracked end-cap. This was also successful; albeit whilst the crack was still open, a thin smear of Araldite epoxy was added to consolidate the repair, which was then reinforced with the previously fabricated alloy bars screwed across the area of the crack...

Yellow Circle: The Bakelite Ammunition Belt Feed Chute.
Red Circle: The Reinforcing Bar.

OK; that's the port chute done. Reassemble the rollers and fittings and cast a jaundiced eye at the starboard one. Will that one behave itself? Its condition was much the same as the port chute.
Eventually; using the same procedures as inflicted on the port chute; we managed to get it back to the shape it had originally been; and, when stabilised with the reinforcing alloy bars, it lined up perfectly with the gun mount circular feed aperture and the ammunition box feed slot.

I love the smell of hot Bakelite in the morning!

To Be Continued.

 

[abaddon1]

The Tale of the RAF Museum Hendon's Hudson Turret. Part 3.

With the Bakelite ammunition belt feed chutes rectified; it was time to turn our attention to the major component lumps. Most of the steel components were corroded solid. Time for the secret witches brew. This is a mix of Acetone Nail Polish Remover and EP90 gear oil For use as a penetrating oil, it makes WD40 and Plus Gas look limp-wristed. You could always use Diesel... that works almost as well... but is smelly and does you no good at all if you decide to eat you lunch without cleaning up first.
The steel gear ring was carefully separated from its moth-eaten mounting ring and de-rusted. At this point the manual rotation handle was dis-assembled to see why it failed to actually rotate the turret. We discovered that the lower third of the bevel gear cone at the bottom of the handle shaft was completely devoid of teeth... not normal wear at all! The thinking was; that over the years, passing stock men and assorted Outback wanderers had probably succumbed to the temptation to play gunners and had tried to use the handle to rotate the turret when in fact, it was seized solid.
Oh, Soddit!... no parts catalogues nowadays!
Trawling through various gearing manufacturer's catalogues failed to come up with anything remotely resembling the knackered gear... this one had a sixty-degree angle to inter-mesh with the gear ring; and most of what was easily available (without breaking the bank) were cut to mesh at right-angles.
OK; let's get the gear off the shaft. This was easier said than done. The Dowel pin was solid in spite of judicious use of hammer and pin punch. It was obviously time to revert to the Harland and Wolff shipbuilders well-proven, and subtle engineering adage...
"Hit it with a big hammer... and if that doesn't work... hit it with a bigger hammer."
(This series of adages also include...
"If it moves when it shouldn't... use a spanner."
and
"If it doesn't move when it should.... hit it with a hammer."
and
"Torque value is relative. With the correct-size spanner; two grunts and it's torqued.")

OK, fingers out of the way. Eventually the tapered dowel pin came free... but my trusty old Starrett pin punch was now beginning to develop a distinctly banana-shaped profile.

It was time to call in a couple of favours. Next morning, I took a stroll down to see the Training officer at work, and explained our problem. After a little horse-trading; (and the promise of a couple of pints over at the Clubhouse)... he said that this would be a perfect exercise for one of his more adept apprentices in the machine shop. Two days later, he called me and said that the replacement was ready. In his office he produced the bevel gear and grinned
"That's a few beers you owe me and the lad... his second attempt; and he cut it to within +/- 0.0003" on the pitch diameter of the original!"
(And this was before our whizz-kid apprentice had a CNC rig to play with)...Fair enough!
He pulled out a small sealable plastic bag containing a dowel pin...
"And just to show that he is a first-rate smart-ass... he turned a new tapered dowel pin that has a ten- micron tolerance for the hole in the gear collar!"
Back at the Innsworth workshop we tried a trial fit to the manual rotation handle shaft. A perfect sliding fit... and the new tapered dowel pin simply slid into the hole, and would require only the merest tap to drive it home.

The next big job was to remove the gun mounts and cross-beam; lower centre piece and footrests; seat assembly, control table and side support plate castings; armour plates, and the sighting arm complete with its pivot arm.
The electric motor/hydraulic generator unit then came out, and we found that the commutator still turned easily... not that it mattered... it would never be powered up again... but at least, it cut down on time spent on refurbishment. All it would need would be cleaning out the treacle in the hydraulic parts.
We then began to separate the gun mount inner plates and recoil mountings from the outboard castings... wondering if anything nasty was about to crawl out. It didn't, but we collected a container full of Aussie wind-blown Outback dust from the depths of the stationary outboard castings. (Funny, that alloy-mag doesn't corrode over there... and we benefited from years of nature's-own sand-blasting in the process!)
It was now time to separate the frame hoop from the remaining support platform, It was decided to leave the electrical power and sight switch boxes, inspection lamps and fuse boxes in situ... bad decision; the hoop was heavy on its own; with all the attachments, it took two blokes to support it whilst I pulled the bolts; but with it out on the workshop floor we could now begin the cleaning and restoration process.

My next fun game was purging and cleaning the hydraulics. The ram was OK, so no requirement to strip that one down. Isaac's Law had ordained that the hydraulic fluid had descended to the lower levels and the ram operated... albeit stickily. All five pipes that run around the rear of the turret from the generator to the hydraulic pump...(better known as the hydraulic motor)... were clogged solid; as were the banjo connections and feed to the ram. The control valve for the "Free/Locked" operating lever was also solid.
With no high pressure air line in the workshop... (which would have been distinctly mucky, if we had gone down that road)... we lashed up a king-sized equivalent of a rifle pull-through with hemp rope and baling wire, and proceeded to de-treacle the pipes, whilst I began to dis-assemble the hydraulic pump/motor. This was a very clever piece of engineering that employed an internal elliptical guide rail, within which rotated an armature supporting seven pistons; each piston's stroke being operated by a shaft attached to a horizontal wheel that ran around the elliptical guide rail as the armature rotated; thus pushing the piston in and out in sequence, and operating the pump. Clever or not; it turned out to be a complete pain in the butt.

Hydraulic Pump/ Motor... Cutaway View.

Opening this motor up was akin to prising the lid off a tin of Lyle's Black Treacle... it was solid, sticky and black.... the sort of thing Grandma used to make soda bread. If it had been like Lyle's Golden Syrup it wouldn't have been so bad... but this stuff... how the hell d'you find... let alone prise anything out of this muck? The only way seemed to be to lift out the complete armature and clean it before we started to pull out the pistons. Hopefully, a quick paraffin wash would not get through the piston bores to the seals; bunged full of treacle as they were. Yeah, right! As we tugged at the armature; slowly it began moving; making much the same sound effect as you get trying to pull your wellie out of a farmyard manure heap.
Eventually it glooped its way free; was quickly immersed in a bowl of paraffin and attacked ruthlessly with stiff-bristled paint brushes. As we thought, the gunge down the piston bores completely shrugged off our efforts with the brushes.
Back on the workbench; the now-recognisable armature showed no signs of any corrosion whatsoever. It was now time to withdraw the pistons... easy said, but a complete sod to accomplish. The suction was unbelievable... (shades of sucking a golf ball through a garden hose seemed to cover it quite succinctly.) Finally, after an hour or so of sweating and cursing; seven pistons lay on the bench... and the seals were as good as the day they inserted them at the factory in Pendeford Lane, Wolverhampton; but they needed a good clean.
Fortunately in deep store, we still had half a can of Air Ministry Spec. DTD44B Hydraulic Fluid... (dated 1941... which we considered would be kinder to the ancient seals than modern brake fluid)... with which to carefully clean the pistons, bores, and seals. So... rubber gloves on and off we go. As soon as the gunge had been removed; it was into a bath of distilled water, washing up liquid, and a bottle brush, and then a thorough drying with kitchen towels. Each seal was then carefully removed from its seat; coated in Vaseline and refitted. Meanwhile another CARG hero was tasked with cleaning out the motor housing and connection ports whilst we carefully re-introduced the pistons into their bores.

To be continued....

 

[Njaco]

I do say, this is a gripping account for something I never thought could be! Bravo on the story!!

 

[Airframes]

Excellent!
Just last week I was looking at the FN rear turret, restored at Duxford, and wondering just how much work had been involved since I last looked at in detail, some five or more years ago.
Now I know!
Great work, and a great account.

 

[stona]

I agree, a very interesting account. I had no idea that the turrets were so complicated!
Cheers
Steve

 

[abaddon1]

The Tale of the RAF Museum Hendon's Hudson Turret. Part 4.

The cleaned housing was returned to us without a trace of treacle. Now all we have to do is to remember how to put it all back together! Meanwhile our housing cleaning hero was getting stuck in to the ancillary hydraulic components.
With a liberal smear of Vaseline... (its really good stuff... and completely inert)... around the elliptical guide rail; the armature and assembled piston array was eased back into position. We needed to turn the armature as it was inserted, and depress each piston in turn, with a slip gauge inserted between the horizontal wheel at the end of the piston and elliptical guide rail to depress said piston into its bore as we positioned it into the guide rail.
With the armature inserted and all moving successfully, it was time to put it all back together.
The five hydraulic feed pipes had now been fully de-glooped... (we managed to get almost half a pound of solid black treacle out of them)... and it was time to figure out what went where. Obviously, the hydraulic system couldn't be fitted until the turret base platform was completed.

OK. time to take a deep breath; and remembering the fun game of two hundred-plus 5/16th" ball bearings all over the floor when the rotation rings were split; let's take a look at this. The lower fixed gear ring has a horizontal bearing channel... the rotating upper mounting ring channel is inverted and vertical.
Bearing in mind the words of the venerated prophet... "Issac always wins;" let's go with the first stab at this conundrum... grease up the lower channel and insert the required number of ball bearings.
"A piece of cake"... as the man said to the Lyons tea-room waitress.
Now; how the heck to do the top ring... AND mate them together?
Enter left stage, our wise old ex-RAF armament trades plumber with an ancient tube of Aeroshell 7 which he liberally smeared into the rotating ring channel.
He grinned.

"Now bung in the bearings and mate up the rings. They'll stick like sh*t to a blanket!"

Timidly we lifted the upper ring; half expecting the merry tinkle as half of the ball bearings hit the floor... but, with it carefully positioned and warily lowered... nothing happened. A couple of quick, judicious thumps, and the rings mated... and actually revolved! We breathed a sigh of relief. OLd Plumber grinned again.

"See? Old and cunning beats young and smart-ass every time!"

We could now begin the reassembly of the side gun platform castings and gun mounts which had been cleaned and primed.
Meanwhile the ammo tub was next on the list. Relatively intact; it still had the side ammo box receptacles and the spent cartridge case/link container intact, and in one piece; and the curved leg protector panels were undamaged; except for the leather protective edge strips which had succumbed to the Outback.
The zipped canvas covers for the three spent cartridge removal apertures in the front of the tub had also gone the same way.

Two replica ammo boxes were fashioned from 18 gauge aluminium sheet; complete with hinged lids. Two spring catches to keep the boxes in place, fashioned on the same lines as vintage car bonnet catches were also fabricated; as were the ammo box removal strap handles.
The zipped canvas covers for the three spent cartridge removal apertures showed faint signs of a pale bluish colour. Blue canvas?... very nice, dearie!
OK. what to use? Then a light bulb moment from one of the galley slaves.
How about old, faded Levi Jeans denim material? (Much muttering in the back row about authenticity)... but wait! Modern canvas is usually made of cotton or linen... and Denim is a tough cotton weave... and the zips are about the correct colour, shape, and size, according to measurements taken from the bits of the AP in our possession.
(Worked out in the old-fashioned way of measuring a known and available part and translating that to the measurement of the illustration in the AP.)

To be continued....

 

[fubar57]

Great story, I'm on the edge of my seat.

Geo

 

[Shortround6]

A most interesting tale. much appreciated.

 

[vikingBerserker]

Excellent thread!

 

[Siddley]

This is just the sort of thing I love to read, ta very muchly

 

[abaddon1]

The Tale of the RAF Museum, Hendon's Hudson Turret. Part 5.

With the rotation rings married up and bolted down to the assembly table that had been professionally constructed by one of our members who owned a woodworking company it was time to commence the reassembly. All the heavy metal had been previously cleaned of corrosion, rectified where necessary, and primed. (Amazing what galley slaves can do with a little bribery of endless cups of tea and coffee!)
First job was to fit the port and starboard platform castings, This was followed by bolting the port and starboard rotating gun mount castings into position on their respective platforms... with a liberal application of Aeroshell 7 grease added to the mating surfaces, before the completed port shelf was loosely attached to the rotation ring. The forward cross-member that supported the front armour plate was lined up into position with the studs on the port gun mount casting, and supported whilst the starboard platform was tweaked into position and lined up.
The forward cross-member was first to be bolted up. This guaranteed that the platform castings would be correctly positioned on the rotating ring when they were finally torqued down... and fingers crossed... the cupola hoop would fit into place. With everything tightened, the gun mounts rotated smoothly.
The actual gun mounting brackets fore and aft could now be properly tidied up... their inside faces de-gunged, cleaned; primed and painted. The spring adjusters on the forward gun mount brackets were removed, de-rusted; stabilised, and repainted.
The spring-loaded spigots on the rear gun mount brackets were freed off, de-rusted; stabilised, and repainted; and everything was then lubricated and re-assembled. We now had something that could accept a pair of Brownings!

The Port and Starboard firing solenoids were then removed, and yours truly was given the job of trying to make them look pretty... and operational!
(Same old stuff... "You work for Smiths Aerospace... they're electrical... get on with it!")
Pulling the victims down wasn't too difficult. getting them working again was another matter... and, from where do I get Bowden cables to fit them?
All that was left of the originals was half an inch of inner and outer dangling pathetically from the solenoid bodies. Micrometer out! Measure the diameter.
OK; that's about the same size as the bonnet release cable on my MGB Roadster! A quick trip to the local breaker's yard; half an hour's rummaging about... and two pristine, black outer covering, Bowden cables. A tad long... but... I've retained the soldered nipples from the originals and a quick once-over with a decent pair of cutters and a proper-sized soldering iron, and... voilà! two replacement Bowdens of the correct size, appearance, and length... cost? £1.50.

OK; First victim... the port solenoid.
With the Bowden cable nipple happily ensconced in the guts of the solenoid, the armature cleaned up; the internal return spring checked, and the coil checked for continuity, it was time to stick it all back together and see what happened.
Small technical hitch... these little sods are 24volts, and I've only got a 12volt heavy-duty car battery. Here goes nothing! Plonk the cables onto the contacts, and... with a pathetic sort of wheezing noise, the armature crept back into the body of the solenoid. OK... at least it tried. Armature out again... clean and polish and stick it back in. Why bother?... it's not as though anyone will ever want it to work.That's really not the point. CARG restorations are proper restorations.
So... all back together and try again. Touch the battery leads to the solenoid contacts, and... "Thunk!" the armature shot back into the body of the solenoid like a rat up the proverbial drain pipe. Lift off the battery cable from the contact, and the return spring shoved the armature back with one more satisfying "Thunk." One down... one to go.
The Starboard Solenoid also behaved itself. The answer seems to be just to clean and polish.The clearance between the inner body of the solenoid and armature is minute. Any lubrication will attract dust and may jam the armature. In our case it didn't matter; but in the case of a live one, it most certainly would.
Time to cast a jaundiced eye over what we've got so far. Anything that needs to go on at this stage before we mount the cupola hoop?
Perhaps, the electric motor/hydraulic generator... although we managed to get that out while the hoop was still in place. So; time to get the hoop into position. This was a three-man job... two to hold the hoop steady, and in position... one to feed in the bolts. Five minutes later; it was starting to look like a turret.

The next main job would be to assemble and fabricate parts for the ammo tub. Much of this had been already completed; but, the lower crossbar and footrest needed to be attended to... and the job that I knew I would be stitched up with... and was really not looking forward to one little bit... the moth-eaten distributor.
Not a pretty sight... almost intact; but the casing holed in two places, and the wiring interconnections?... not a chance! Old, vulcanised rubber sheathing and Outback sun does not mix! All that was left was an elegant spiderweb of verdigris... but... with luck, I might just be able to re-wire it by following what was left.

Red circle... the main suspect.

At this point, the word came that, after much horse-trading; the Boys at Hendon had managed to prise a pair of 0.303in. Brownings out of deep storage at RAF Stafford. A pair of bangers! Now, it will look like a real turret and not a high-tech garden cloche!

To be Continued

 

[Siddley]

Who deacs the guns for you ? I've got a mate back in the UK who is a Sec 5 firearms dealer with a huge interest in militaria who would probably cut you a good deal on that sort of stuff.

 

[Airframes]

Great stuff.
If it's not too much trouble, is there any chance of a photo or two of the interior, and the turret basket? It would be of enormous help for a future model project for a 2 Grp Ventura.