powerandpassionSmiths electrical fuel contents gauges make a prototype appearance in 1934-5 Air Annual of the British Empire and in the following year’s volume with the familiar look of the mystery gauge. In AP 1275 Instrument Manual 1937, reprinted in Jan 1939, they are described, but the statement is made that they are not part of the RAF Stores system, so the fixing of a 6A number implies a post 1939 instrument. I concur with my learned colleagues that the lack of the tail down scale implies a flying boat, as much as the gross quantity of fuel.
The Short Bros Empire Flying boats of 1936 were initially equipped with 600 gallons of fuel capacity but this was later increased up to threefold. However the “No 6009” is reminiscent of Supermarine part numbering. Supermarine Stranraer? Hold it closely to your ear and see if you can hear some faint Glen Miller, which would place it about 1940…
powerandpassionDP 55206/2
You have a DH Blade drawing???? You have a DH Blade Drawing???? Matt
Beermat,
Here’s another one, albeit incomplete, DP55206/2 from DH Australia, please explain !
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powerandpassionThank you! Very interesting stuff. Very encouraging that HVOF is being used. Will take a few months to set up the test, strip down the Cheetahs and look at all the crankshafts, bearings. Will pop back up with this in 2017. Very, very interesting….
powerandpassionI’ve spent a good bit of time trying to make HVOF coated flying parts work, and they do;- But as ever, the devil is in the detail;- in particular the surface finish. So brush up on your Ra, Rb, Rc, Rz, Rmz etc
Vega ECM, I am a lost lamb in the woods on this, but want to learn.
Can you confirm that HVOF is accepted in the serious side of the game.
Um, what is Ra-Rmz?
The particular interest is vintage crankshafts, most of them nickel chromium alloy. The back of the cereal packet says that bonding between substrate and coating was the first issue of concern. Can you confirm that 2016 HVOF has resolved this ? Is it necessary to machine to original surface to allow HVOF to fix better?
Does impregnation of oil and other contaminants in the crankshaft metal require some pretreatment to remove?
What are your thoughts on HVOF applied to nitrided parts?
In terms of oil holding capacity and finish, I assume this means that 2016 HVOF results in a working finish, ie no machining afterwards?
So many questions! I would be immensely grateful if you would guide the experimentation on the Cheetah crankshaft, all in good time…
powerandpassionThanks Robbiesmurf. Will try and report back what happens. Will take a few years….
powerandpassionAnd, if you want a boisterous fire-side pub discussion-topic for a long winter’s evening (that is guaranteed to drive any female company further away than they already were) how about this: why machine everything on the bearing to sub-thousandths of an inch to keep the oil in and then cut two dirty great chamfer tunnels along each split-line edge for the oil to pee out of?
Chicks dig tribology! I have rubbed against a few and tried different lubricants, in the name of science, and I encourage all youth serious about the topic to investigate and learn how they too can get a free running crankshaft!
In terms of inexplicable chamfers I recollect a conversation with a free talking engineer who dropped the mask of confident authority when discussing a particular engine out in the market. They had no idea about fixing foaming in the sump. The configuration had been set up in the Jurassic era by some forgotten authority and never questioned. Then they cut a window in and observed what was happening inside. There are so many unique conditions set up with each configuration that it was only old fashioned observation and experiment that resolved the issue. I guess that lots of different things have been tried and unpredictable results obtained that seem counter intuitive. Maybe a partial vacuum is set up that sucks lubricant in. Maybe the chamfer aligns with the earths magnetic field and sends a signal out to alien life forms, that then back channel Ghostbusters type goo, which is they way they communicate. I hope my suggestions are being useful!
powerandpassionI think the bearings are cut into two halves, clamped back together, and then line-bored (or broached probably).
The repair scheme for centricast RR Kestrel big end bearings allows this as a once off refurbishment. There is plenty of bearing meat. There is far less meat on the Kestrel Main bearings and even less meat on later silver -indium bearings for new fangled engines like Merlins, so the risk is the actual bearing material is removed at the clamping edges, if this is done. I still think the bearings were line bored as an intact circle, then split. I think that differential expansion, between a nickel chromium alloy crankshaft, and a plain carbon steel shell with copper-lead-silver coating would require some clearance. The bearing shell would need to expand without buckling. I guess this was part of the bearing maker’s ‘black art’, how much clearance to allow, and what sort of blade to use to split the shell to arrive at this clearance.
There is a mob reasonably close by who make bearings for racing engines, I will have to ask. If I am found floating face down in a river, they told me the secret…
powerandpassionSeafire, I have to acknowledge that the Gilman Bearing and the Allison Engine Co’s inventiveness, all God fearing Apple Pie American stuff, saved the Free World, and for this, we are in your debt, Sir.
Americans are also better at fitting bearings, because thermal transfer from a Texan gut resting against a crankcase allows the caps to slip in easier….:)
As an Australian, our only contribution is in pioneering the use of flip flops, part of the national costume, to drive sticking parts in, or to plug leaks..
You will always need an Aussie mechanic in flip flops somewhere in the hangar, in case you need to quickly cut an oil seal.
powerandpassionAA, I understand this issue. It is dismal and holds back so much that could be inspiring in our own heritage. It might be easier to do a Japanese engine, with nothing but science to rely on in determining what is safe and insurable. The point to consider is that 70 year old repair schemes do not encompass 2016 technology. More, the confident practitioners of the art, who wrote the original repair stuff, have moved to the great golf course of the sky, so no one is left to put a nappy around this stuff. So back to the basics of test and control, scientific data, proof, disproof, progress and God forbid, fun! I am really interested in the why and the why not. Some of the crankshaft resurfacing is used in industrial applications that exceed the service pressures and service exposures of things like Cheetahs, so the Godess of science says ‘seek and Ye shall prosper’.
powerandpassionGosh, an Oxford only has two! I promise not to diminish the stock of engines. Any decent experiment will require a test and control, so one engine, entirely unaltered, and one engine with a key element altered, running side by side. In the first test, both crankshafts ground down, at minimum, within spec, control on original oversize main bearing, test on new oversize main bearing, to determine if new main bearing OK. Then, pushing, crankshaft built up to standard size using HVOF on test, new standard size main bearing, see what happens. Probably bisect built up crankshaft after test to examine bond between old and new material, so only one crankshaft lost. To gain might be a method of revitalising all your Cheetahs, turning scrap into gold. Why Cheetah? Because after doing it on some old diesel cranks subject to greater forces, you still won’t believe it until you see it. And then we can tippy toe into something terribly rare. I bet that the method will work for engines designed for copper lead main bearing type pressures, but not silver indium bearings, so pre 1943 types, that need something like this to ever have a hope of getting up, interesting once off type engines…
powerandpassionThe exciting bit is that the CSIR, charged with research and development, then started a program of refining techniques for the making of copper lead (and other) bearings, so there is a cook book around….
Have found the CSIR bearings literature, and have now stood upon the Everest of vintage aeroplane engine bearings literature, and the view is good. Bearings from various Japanese radial engines are examined as well as techniques for casting Allison, Kestrel, Merlin and PW radial crankshaft bearings. Time to get in the kitchen and rattle some pots and pans.
What I still don’t get, because it is assumedknowledge in all the literature, is that a round shell bearing, split into two, cannot be all encompassing around a crankshaft journal. In other words, when you cut a line bored, round shell bearing into two halves, some dimension, the thickness of the cutting blade, must be lost from the circumference. I assume a very fine blade was used to split the round shell. So when you clamp the two halves back together, you get an egg shape, not a full circle. That’s assuming that the two half shell ends meet, or is there some float between the two? One piece of literature talks about the desirability of nothaving a pure circle, in that it forces the bearing into better contact with the crankshaft journal. By splitting the circular bearing, you would also release stresses imparted during the high temperature bearing casting process, so the halves would open up to a certain extent. I cannot image these halves, within their packaging, also holding their shape as they were rattled around from factory to workshop, and dropped on the floor by a mechanic attempting to fit a bearing while eating a donut (only Americans do this), or the modern equivalent, while taking a customer call on a mobile phone cradled against the ear…
So the important dimension is the outside dimension of the steel backed bearing, that integrates accurately with the crankcase, that clamps an egg shaped bearing shell around a crankshaft journal, me thinks..
powerandpassionHere is a list of prop records held at UK National Archives, Kew. Some very interesting records that I would love to see. Stuff on Welkin, Mosquito, data on aerofoils.
How does one get to see this stuff….
http://www.enginehistory.org/References/UKNA/Prop-DSIR.shtml
powerandpassionWheel should be a magnesium alloy. Remember P&P I still have your landing lamps!
Please feed them occasionally !
powerandpassionEd, unless originality is a must, I would ditch the decagonal bead and go with a standard bead/tyre combo. If the wheel isn’t driven or braked, there won’t be any relative rotation between tyre and rim, unless perhaps if the bearing were to seize in the wheel!
White tell-tale markings on the tyre will let you know if it is moving.
Bigger wheels don’t need it as they have plenty of square inches pushing on the bead to ensure there is no slippage!Thanks for the update 🙂
Cheers
Graham
Graham, it’s a good point, re no seized bearings mean no tyre slip. I have learnt to wait though before I move on from something without clearly understanding the ‘why’. The reasons are always surprising and the product of the thought of many well trained men integrated with a flying test program and feedback from many contemporary users. It will be something weird out of left field like 68% more electrical contact between conductive tyre and wheel….
powerandpassionThis P-38 wheel below has both a casting number and a Dow metal material identification on it, showing Heat Treated Dow H magnesium was used, making life easy.
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Because I have just gone through an election I have been conditioned by politico speech to avoid the plain truth. So, “due to market forces I wish to reposition my stance on my previous comment which was made in the context of circumstances that have now changed”, specifically the metal in the Bendix wheel is Dow H-HT, not Dow H as I previously stated. All this because I am spending a lot of time reading through old engineering books and staring at old wheels. Dow H-HT is actually a very sexy magnesium alloy with interesting herbs and spices like Nickel and Copper. It’s ultimate strength and elasticity is better than the DTD alloy used in Mosquito wheels. I had a hunch that the Bendix wheels had to be made of something interesting because they are quite an optimized design, very little wasted metal. The Mosquito wheel is kind of a heavy boned fish wife next to the Bendix svelte young thing. Dunlop seemed to chose a simple alloy and loaded plenty of redundancy into the design. I wonder how much Bendix wheels were designed for organized tarmac and Dunlop wheels for grass and mud fields.
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