Something that Camlobe said in another thread has a fundamental bearing on the Whirly project, so I am bringing it up again in the hope of resolving something.
If De Havilland-produced counterweight and Hydromatic hubs sometimes carried the Hamilton Standard designations as well as their own (so that a DH 4/4 is also a 3DX40), then that implies exact spec equivalence.
This means that we can use a retired 3D40 (as per Otter etc) on our Whirlwind with complete authenticity. This would be a massive coup, as anyone who knows how hard-to-source DH prop stuff is will understand 😀
Anyone who can produce primary evidence will be mentioned in despatches!
By: Beermat - 28th August 2011 at 23:50
Thank you Anon. All that really is very encouraging. I will be starting to put out feelers for 3D40’s tomorrow!
Spline size – yep, it was shank size equivalence I was worrying about, always being vaguely aware that splines were going to be different. The thing is, barring the shed-find to end all shed-finds, we won’t be bothered by having to match the hubs to the SBAC 4’s of a pair of RR Peregrines.. I wish we had that problem!
Thanks again!
By: Beermat - 28th August 2011 at 23:50
Thank you Anon. All that really is very encouraging. I will be starting to put out feelers for 3D40’s tomorrow!
Spline size – yep, it was shank size equivalence I was worrying about, always being vaguely aware that splines were going to be different. The thing is, barring the shed-find to end all shed-finds, we won’t be bothered by having to match the hubs to the SBAC 4’s of a pair of RR Peregrines.. I wish we had that problem!
Thanks again!
By: Arabella-Cox - 28th August 2011 at 20:29
Props
Beermat,
You may find that, although the designs are pretty much the same and blade and other component interchangeability is possible, the decider as to what you can use in lieu is the spline type.
For example, the SAE 50 (US type) spline is different from the SBAC 50 (UK) spline so whilst the hubs and other parts can be swapped, the prop wouldn’t fit on the engine shaft.
Whilst I think the small shaft size splines had some commonality the 40 and 50-size shaft splines were certainly different and non-compatible.
The (war time) de-H props were initially manufactured by Ham-Stan until production got under way in the UK (using US-built machines) and all parts were interchangeable. Lots of development work went on with refinement of the original H-S designs by de-H until they began producing their own designs. They, effectively, took the original and excellent H-S designs and made them even better, as well as bringing out new designs, producing a wide range of props for many applications.
The de-H company even bought licences to produce H-S’s rival, Curtiss’s propellers and used the best of the hydromatic technology to replace the troublesome electric pitch-change units (the Achilles heel of this company’s propellers) of the Curtiss designs leading to excellent high-power units.
Anyway, I digress. To return to the original issue, simply, H-S and de-H props followed parallel paths during WW2 so any prop from either manufacturer would be interchangeable with the other – as long as your engine had the same spline.
Solution? swap the internal spider or, have the splines re-cut to suit your engine – ideal for a ground runner or static.
Anon.
By: Arabella-Cox - 28th August 2011 at 20:29
Props
Beermat,
You may find that, although the designs are pretty much the same and blade and other component interchangeability is possible, the decider as to what you can use in lieu is the spline type.
For example, the SAE 50 (US type) spline is different from the SBAC 50 (UK) spline so whilst the hubs and other parts can be swapped, the prop wouldn’t fit on the engine shaft.
Whilst I think the small shaft size splines had some commonality the 40 and 50-size shaft splines were certainly different and non-compatible.
The (war time) de-H props were initially manufactured by Ham-Stan until production got under way in the UK (using US-built machines) and all parts were interchangeable. Lots of development work went on with refinement of the original H-S designs by de-H until they began producing their own designs. They, effectively, took the original and excellent H-S designs and made them even better, as well as bringing out new designs, producing a wide range of props for many applications.
The de-H company even bought licences to produce H-S’s rival, Curtiss’s propellers and used the best of the hydromatic technology to replace the troublesome electric pitch-change units (the Achilles heel of this company’s propellers) of the Curtiss designs leading to excellent high-power units.
Anyway, I digress. To return to the original issue, simply, H-S and de-H props followed parallel paths during WW2 so any prop from either manufacturer would be interchangeable with the other – as long as your engine had the same spline.
Solution? swap the internal spider or, have the splines re-cut to suit your engine – ideal for a ground runner or static.
Anon.
By: Beermat - 27th August 2011 at 23:21
Bump!
I am not surprised to see 169 views and no answer – I’ve noticed before that there is a ‘hole’ in the normally comprehensive knowledge of the fraternity around this. So many aircraft were equipped with either DH or Ham Stand props – in fact the vast majority of the allied ‘greats’ – but ask about dimensions or whether the two were in fact the same item given the same shaft size, and quite genuinely nobody knows!
It’s not like its impossible TO know. If someone was able to take a tape measure to the blade shanks of, say, a Blenheim and a DHC Otter (4/3 and 3D40), or the Shuttleworth Spit V and a DC3 (5/39 and 23E50)..
In fact, I’ll be approaching ARCo with said tape measure at DX next weekend 🙂
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August 26, 2011 at 9:41 am