BeermatThe whole thing needs a radical policy re-think at the top level. The fundamental problem is that the generation that could be excited and/or inspired by a static artefact coupled with their own imagination, enough to travel to suburban North London, are becoming grandparents now. Things need to at least move. Bemoaning it won’t help, though it’s not a great state of affairs.
One idea that would work is a working museum, combining the BoBMF with the static content of the RAFM. Rather like Duxford, in fact. One facility for two operations, and double the draw. Just need a venue.
BeermatPS, that last ‘7’ is almost certainly seven inches removed. The Hornet blade ends ’36’ and is, according to this RAE document, a 15 foot design cut down to 12ft.
http://www.dtic.mil/dtic/tr/fulltext/u2/a800709.pdf
(Something odd going on with DH Hydromatic blade basic diameters that I am still trying to get to the bottom of via the numbering system).
BeermatJust to highlight, in case you missed the other thread, Graham, it looks like you need a 33EX
In English that’s a 55/ (or 5500) Hub – which you knew, it’s just that this doesn’t relate to the blade number, which has a 55 in it for a different reason (though if it was an ‘F’ shank the hub would be a 6000 – confused yet)?
By the way, re. blade numbers, I am back to thinking my system at least partially works – so 4551157 is 45 for Hydro, 5 for ‘E’ shank (ie 5,000 series). I vaguely recall the rare Spitfire Hydromatic blades were 454-something, and they were ‘D’ shank (4,000 series). British Hydromatic (and bracket) blade numbers don’t reflect shaft size/spline of the hub they are attached to, just their own shank size..
It seems DH were out to confuse everybody when they chose lots of 4’s and 5’s to mean several different things in different but related contexts.
BeermatIf it’s really 20 cm wide it’s too small 🙁 If we were looking at a commercial blade-bashing operation we’d need to be able to accommodate up to 16 inches / 40 cm
We can’t get Coopers Stout this end of the planet.. I’ll try to import some, as I expect it helps one come up with ideas like blade-twist-reversal.
The thing about the DH graph is it’s been re-interpreted by the RAE authors who were only interested in blade shape, not absolute dimensions – so they need to be added. The trick to testing whether its the same blade profile is to make an assumption of commonality and then work backwards to test it.
We know that the Spit blade is 64.5 inches hub centre to tip, so that helps – that’s your horizontal axis mark-upable right there. Take the chord at a station from the HS tabularlar figures (I used 42 inches as it’s the traditional ‘reference station’) then assume that the chord at that station on the DH blade graph has the same value. That gives you a vertical scale.. Mark up this scale of assumed absolute values on the vertical axis (I didn’t show that on the one I sent you), and then plot the rest. If it’s a different blade profile it will very quickly show up!
Re Typhoon hubs, these threads are useful: http://forum.keypublishing.com/showthread.php?133906-What-Does-This-Prop-Spider-Fit (Merlin Pete’s list) and http://forum.keypublishing.com/showthread.php?137760-Propellor-hub (The all-knowing Anneorac).
So what you really need, in a perfect world, is a DH 55/ (or 5500) hub – which is presumably equivalent to a HS 33E60.
There are crash relics out there, but airworthy might be another matter!
BeermatWhen I said about initially having to use an existing 6,000 series DH bracket prop (because the Hamilton 33E and the blades developed for it didn’t exist yet) I honestly had not seen this pic of the first prototype! Compare with the Spit/DC2 – the same, just longer 🙂
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BeermatThe waters here are quite murky.
A lot of the problem comes from the fact that even if shaft diameters were compatible (and here I bow to Anon’s practical experience), the scale of horsepower applications were different. The US were happy with SAE50 up to 2,000 horsepower. The UK went from SBAC5 to SBAC6 at – what – the 1,400 horsepower of early Hercules?
It looks like the Typhoon hub would have, initially, been neither a 33E or a 43E. The 33E was introduced in late 1941 (the type certificate was issued in March 42), to cope with horsepower above 2,000 so it looks like, at first, Typhoons would have flown with a copy of a blade designed for the 23EX, and some other kind of hub (on the assumption a 23EX machined out wouldn’t cut it, as per Anon). The other thing to bear in mind is that blades were interchangeable between hubs of the same shank size, and some are still certified as such, like the 15 ft blades on the C-46, which are certified on both the 33E60 and 23E50 hubs, at different power ratings.
De Havilland, in their brief potted history in a 1956 ‘Flight’ , say they redesigned the Hamilton bracket hub around 1939 to fit size 6 splines, as there were no US ones . These of course needed blades, and https://www.flightglobal.com/pdfarchive/view/1938/1938%20-%200090.html shows a potentially 14′ 6″ prop. As far as I can tell these were first used on the Hercules powering the Shorts G class (not the ‘1939 generation of bombers’ mentioned in the flight article).
DH weren’t designing blades in 1938, so the blades pictured would definitely have been based on a Hamilton blade design. (Interestingly, re the design numbers, the 14′ 6″ pictured would be 14′ 7″ on a Hydro hub).
I can only presume that, in the absence of what would be the 33E60 at the time of the Typhoon’s design and first flights Hawker – if specifying a Hydromatic – would have needed de Havilland to design their own Hydromatic SBAC6 hub – or fly the early aircraft with an SBAC6 bracket prop (more likely?), complete with existing big blade design minus 6.
Perhaps later, with the availability of 33E60′ and more importantly 33EX’s, this changed. – and I think I do detect a variation between prototype and in-service prop blade designs as well. I would be keen to measure a Typhoon blade against those 15 foot blades listed against the 33E60 in HS130.
Looking at the dates on the Type Certificate, the 43E60’s were post-war (DC-6 etc)? I stand to be corrected on this.
Looking at a few images, the standard ‘in service’ dp4551157 Typhoon prop is definitely, in my opinion from years spent staring at such things, not a full ‘basic diameter’ blade. From the ‘blunted’ tip it looks like something between -6 and -12
Just some observations really, I am sure it doesn’t help!
BeermatRats. Is it worth looking at those 15ft blades , eg 6491, “minus 12”? Might even have been what was done.. more blades were in fact used ‘cropped’ than ‘-0’
BeermatI don’t have a better version, normally the NASA search engine gives near-perfect copies but this time it points to this blobby one that’s also on AERADE.
I see those numbers too. As well as 6159, HS130 also gives 6359 (as 6159, but with chafing ring (sounds painful)), and 6895, 6899, 6921, 6969, 7019.
I expect those last five were later than the July 1943 document.
Worth measuring the blade the project has, see whether it’s a HS 6160A-0 as well as a DH – on the face of the figures, it looks similar. One thing I am sure of, my DH numbering system worked for bracket blades, but not Hydromatics.
BeermatQLDSpitty, pm me an email address, you might have noticed from other threads that thanks to Graham A I have a table of blade data you might find useful.
Beermat..and in case of doubt, the FAA Type Cert for the DC-2 has the original propeller fit as 6111A-6:
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BeermatYes please, those sound interesting..
After I’d been skipping around the room for a bit, Mrs Beermat said ‘Yes, but does anyone really care’? I kind of saw her point, but then I read her your comments and said ‘See! Told you!. What’s more, you do realise this will make me irresistible to women, don’t you’?. To which she replied ‘Well, I can bloody resist you’ and walked out of the room. Anyway..
Here’s the chart from an RAE research paper, as annotated by me – ‘Propeller V’ is the DH 55409 of the Spit Mk I.
I converted the ratio r/R into absolute dimensions, and plotted on the stations as laid out in HS130 (Red Lines). I shifted by half an inch to account for the differing hubs.
Taking the reference station at 42″ as my datum, I then plotted the chord figures for the 6339A at those stations (little green dots – they are there if you squint) – and VOILA!! Right on the line.
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HOWEVER I cannot make sense of the thickness/chord figures produced from the Hamilton Standard tables (as thick as a Spit 2-blade wooden prop??? Am I reading this wrong? Probably), and the ‘twist’ figures don’t match either.
So what we have here is a legacy plan-form, not the blade that the Spitfire’s was copied from but a ‘ghost’ of that blade, with a different twist. It does demonstrate one thing that we already knew, really, and that that these early DH blades were copies.
I do have an ace up my sleeve though – A 1943 NACA report shows the 6339 to share both basic diameter and ‘Activity Factor’ variation with length – and therefore exact planform, with two bracket/counterweight blade designs. These were 6103 AND 6111
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One of these two, I’ll bet my missus, is the Spitfire blade. 130B table 3 says the 6103 is thinner than the 6111, but that’s all it says. No numbers.
BeermatOK, so, the Basic 6339A looks like a Spitfire 55400 – or rather, a 6339A-9 would look very like a 55409. This is a Hydromatic blade, but tomorrow I will cross reference with Bracket types.
Unfortunately, most of the early needle blades, the ones DH would have copied, are name-checked in the document but not given tables – for example the 6127 I am looking for for the WW.
BeermatLooks like it. Which might make the ‘photo ship’ a Yugoslav built Do-17K.
BeermatThank you Graham – all received – it went to my ‘junk’ – some email software just doesn’t recognise gold when it sees it..
I am just doing some beer mat maths, in between pretending to do my day job, and will get back to y’all..
If this doesn’t get the ladies attention then I don’t know what will.
BeermatDeciding that it was getting silly, I did another search for SAE standards today, and I finally found a page of a 1943 standards document, one I was probably supposed to pay for, that I suspect slipped onto the ‘preview’ window by mistake.
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These are the SAE spline sizes used by US engines. Turns out that SAE40 was fractionally smaller than SBAC4 – ‘A’ is 3.124 and ‘C’ is 2.995 inches on the British shaft.
How does the ’60’ stack up against the SBAC 6 of the Sabre?
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