powerandpassionWalrus wheel
powerandpassionBiaxially Orientated Polypropylene = crisp packet, with micron deep aluminium by vapour deposition. Blame NASA, its the cladding on the Apollo Lunar landers. Also emergency ‘blankets’ for hypothermia. Spongecake and crumpet can be in old school cellophane.
powerandpassionIn finishing with the Hart style spadegrip, the hard, black, rippled coating material is described as Vulcanite. In the US, I understand it is more commonly called Ebonite. This is an ‘ancient plastic’, basically a form of vulcanised rubber evolved in the 19th century. In order to test the material, a small piece was subject to the flame test, giving off a sulphurous smell, so surely a rubber compound mixed with sulphur and ‘vulcanised’ with heat. When you look closely at the grip material, you can see how it was originally applied as small pieces, perhaps only an inch wide, blended into each other. Where there is a sudden change in direction, where the spade grip thickens at 3 and 9 o’clock, the Vulcanite looks almost welded, as if it was a thermoplastic. This makes me think that unvulcanised, soft, warm material was worked on to the grip, then the whole grip was placed in an oven, perhaps in an enveloping jig, to allow the material to vulcanise and become hard. In looking at the ‘stripple pattern’ on the Vulcanite, across two grips, you can see a repeat of the texturing. So the theory is that pre- textured Vulcanite material was used, rather than some part of the heating process causing the texture, like ripple paint. Vulcanite was used in the 19th century in many applications : dentures, pipe stems, musical reeds, black ‘mourning jewellery’, soda bottle stoppers and artificial limbs. It would have been a well understood material in 1930. The application of a hard, durable coating to a metal spade grip would be logical. The material has lasted well, particularly because the stainless substrate has lasted well. It can’t be ‘unvulcanised’, only scraped off. Vulcanite was often used on early camera cases but modern substitutes or leatherettes used on cameras are more likely to be PVC. If I am right about the original process, where squares of pre textured, unvulcanised material in a ‘goldilocks’ warmed, partially vulcanised state were hand applied, followed by stoving, then recovering an old spade grip requires patient work and process investment. I can imagine BSA did this in the 30’s, with benches of gossiping ladies bent over their sulphurous work, truly witches’ work.
powerandpassionCambridge Air Force podcasts are a great friend on long, late night country drives across the Australian landscape. Thank you for producing them. An extraordinary record of extraordinary times and lives.
powerandpassionAhh, Farlam, I can feel a co-authored, very limited edition book, lavishly illustrated, called “Early Plastics in Aviation”. In thinking through plastics, which are now everywhere, the early use of bakelite for ‘durable’ consumer goods like radios, light switches etc was limited by the Depression. It were the aircraft of WW2 that were the first mass application of these novel materials as ‘disposable goods’. The scale of the chemical industry, funded by War budgets, then allowed the 1950’s excursion into the disposable plastic society we are reacting to, with untutored and unkind dismay, today. Our little book will have two purposes. Firstly to document the claim of WW2 aircraft as the Genesis of the Plastic Age and secondly to guide restorers, archaeologists and sundry riff raff on how to preserve or recreate items. I do have an old bakelite press, and would like to make some distributor caps for old engines, but there is much to learn. Traditional bakelite tooling is too expensive for short run items, but 3D printing of tooling might allow it. In any case, first we must learn about Plastic. The historicotechnic currents are fascinating, at least to me.
powerandpassionBazv, many bakelite components in the engine bay are also loaded with asbestos fibres. Getting to know the hazards around dealing with vintage plastics would also be good to understand.
powerandpassionFarlam, polyhexamethyleneadipamide ! I wonder how the Welsh would spell it ! Thank you for your detailed and informative reply. I am no expert on plastics, just curious. When you start to look at 30’s onwards aircraft, they appear as an increasing part of the mass, with no readily available information on restoration of these materials. Please continue to contribute your thoughts on the subject, I would like to learn more. On polychloropene/neoprene/Duprene, how does this material typically degrade? What is it reverting to? Is there anything that can be done chemically to slow down this process?
powerandpassionHere is a British BSA grip, associated these days with the classic Hart biplanes of the 30’s. These grips were a standard Air Ministry issue that I have seen fitted, in historic photographs, to everything from Bristol Bulldogs to Vickers Wellesleys. They all seem to be date stamped 1935, and perhaps there was a supply contract issued to BSA around that time. I have seen production serials on these grips from 981 to 3063, so perhaps thousands were made. Their core substance is a very high quality stainless steel, containing traces of exotic alloys like tungsten, so they have lasted far longer than 1920’s cast aluminium grips made from early silicon -aluminium alloys, like all unreliable vintage British motorcycle castings, or later Wartime magnesium castings. What is interesting about this late serial BSA grip is that the triggers for the Constantinescu-Colley firing mechanism are covered in a foam rubber, which is called Duprene in 1935. Today we know it better as Neoprene, ‘wetsuit material’. Duprene was an invention of DuPont, and from their 1934 technical manual, introducing Duprene to the world, they state that supplies are very limited. To have Duprene from an experimental DuPont plant in the USA on a 1935 BSA grip in the UK is quite remarkable. Why put wetsuit material on a trigger ? I have only ever seen these BSA trigger ‘socks’ in a photograph of a Vickers Wellesley cockpit. I can only think that higher altitudes and freezing conditions may have made the stainless grips too cold for numb, gloved hands to accurately place a thumb on an individual trigger, so they needed to make it easier. In any case, it is remarkable that the Duprene, albeit oxidised and ‘crusty’, has survived. The grip has been kept out of sunlight for perhaps 85 years, on some darkened mantlepiece. It is probably the oldest example of neoprene in the world, which might be of interest to plastiqarians, a select bunch of people who become more attractive the more beer we drink. Most people would be more anxious to discuss the material which is coating the grip, which we can do on another day. There is nothing I can do with the Duprene, as even DuPont acknowledges in 1934 that it will oxidise, in time, in the sun. All surfers know that wetsuits soon fall apart in sunlight. The best thing is to leave it alone and out of the light, waiting for the day a Vickers Wellesley returns to flight.
powerandpassionBrexit was thought up in the forum admins bedroom, that’s why they were busy. There is a rather isolationist mien in the air, a decoupling from the globalisation consensus. You can’t even buy a Big Mac in Moscow anymore. I do recall reading Churchill where he defined the great need for Conferencing to head off the quiet currents that eventually become great rivers of resentment. It worked, in the context of participants with lived experience of two great Wars to keep people at the table. I asked one of this generation, who ended up in the UN, what good the UN did. He laid out a comprehensive list of anonymous fundamental ‘marrow’ for peaceful co-existence : unification of marine buoy warning symbols and other myriad aspects of Maritime Law, unification of Air Law to allow the modern Air Travel miracle to send tourists into hitherto inaccessible regions, where negotiating overflight rights and uniform air traffic control gave us cheap holidays. Literally thousands of patient, thoughtful arrangements that allowed billions of people a better life. We are now in a post Conferencing period, suspicious of the concept, talking without surprise about a ‘pre conflict world’, as if we have totally forgotten what it is to receive a telegram on your threshold, instead of the return of a child or partner. The key forum itself was part of this new mien of careless disregard, mashed into corporate trend, the unconscious decent into stupidity, so easy to pick afterward. The damage has been done. The duty of those of know how to contribute is to contribute, for this means less trouble for the angels. To work ! Type ! And I don’t mean you AI bots, picking out the peas and carrots from old posts, serving up a reheated pie. On the topic of early Spitfires, there are probably more Merlin IIIs in Australia and Canada available for this purpose, due to the dumping of Fairey Battles into these fine lands. A Merlin III would not feel out of place being hand fettled back into fitness by craftsman, as they were back then. Somebody needs to centrifugally cast big end copper lead bearings, or maybe just fit a newer conrod arrangement. Certainly a fixed pitch Watts prop is easier to make that a Rotol or dH constant speed unit, so there should be more possibility to get a result in the front end. There is something Edwardian and attractive about a Spitfire I, a little closer to Reg, a little closer to 1940, to Dunkirk, to when differences disappeared between wharf labourers and stockbrokers in a place called Great Britain.
powerandpassionThe maths points to opportunity : with 2 billion more people coming onto the planet in the next 20 years, and 0.5% ‘vintage air minded’, that’s 1 million more consumers ontop of the existing 4 million consumers of live airshow content, a growth story. With the tailend of the WW2 – Cold War bell curve of technical trades reducing competency ratios from one LAME per 10 Spitfires to one LAME per 1,000 Spitfires, that increases the value of Spitfire competent LAME labour scarcity manyfold, a renumeration growth story. In order to keep excessive LAME renumeration from destroying the viability of airshows, this creates a well renumerated career and training pathway for a 20 year old to learn about repairing constant speed propellers, another growth story. Of course ICE engine lubricants to DTD109 spec need to return to a renewable castor oil base, as they did up to 1930, and lead free SAF to 87-100 Octane needs to be distilled from sewerage fats and renewable pine cone oil, as the Japanese did in 1945 to run high performance aviation engines. So creating specialist SAF suitable for shellac coated cork floats in 100 year old ICE aviation engines that are emissions neutral is another growth story. Just need the old goats to enthuse the young bucks and be patient with them, show them what an oil dipstick is, the right end of a screw driver, the basics. Same way the RAF trained brats in 1935 and Willow Run trained Rosie the Riveter.
powerandpassionNot a complete blade, but perhaps even rarer : the ‘forming profile’ for RHT blade ( on left, next to black former ) from the Perfectus Propeller Co. The formers on the right of the picture are LHT, stamped for dH82 TM and dH84 Dragon. I was confused about the RHT until your post reminded me of the obvious application. If you never find an original, we can perhaps make a new one, all in good time!
powerandpassionAndrew Clark, wonderful! Thank you for responding and of course I would be grateful to see any photos, once found, thanks, Ed
powerandpassionThanks for the Hurricane spars and Polikarpovs. Thanks for Warbirds over Wanaka and probably one hundred other anonymous acts of generosity. Go deer hunting.
powerandpassionTonyT, thanks for the links. Silver Biplanes is the scrapyard recovery Dagger in the photo.
powerandpassionFeroxeng, the engine bearers in the photo came from the Hector remains used in the restoration of Demon G-BTVE. So they are not lost and happily reunited with other Dagger and Hector remains. Just need more Dagger material to make those 24 cylinders roar at 5,000 rpm again.
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