2-blade 10-bolt-hole hub ID help please

[jasong]

Hi Everyone,

I recently came across a large hub for a 2-blade propeller.

It has no markings on it at all but the dimensions are:

Hub diameter: 29cm (About 11 1/2 inches)
Hub thickness: 25cm (10 inches)

It has 10 bolt holes, and is fluted on the front of the hub for a few centimetres along the blades. (see photo attached)

The cross-section of the blade shows 12 layers of laminate, with 13 layers visible at the hub.

I have tried to ID it from the Hub page on this website, but with no luck.

This is not like any hub for an early wooden prop hub I have seen before. I'd be grateful for any input.

Cheers,
Jason

[pmdec]

Hi,
There is a standard French hub of the 20's with these measurements (millimeters):
- Hub diameter: 290
- Hub thickness: 255
- Bolt holes (10) size: 16
- Bolt holes circle diameter: 224
- Center hole: 90.5
It was named (type): "T long"*** and was in use on some aircarft fitted with 450HP engines.

Have you removed the metallic plate on the opposite side of your pic? It have to have markings at least on one rounded side of the hub, perhaps faint ones.

***There are two kinds of "T" hubs : long (thickness 255mm and bolts size 16mm) and short (thickness 210 and bolts size 14mm).

Regards,
PM

[jasong]

Thanks PM, that's really useful information. The hub forms the base of a lamp, and to remove the steel plate from the other side of the hub would involve taking the whole lamp apart, which wasn't possible at the time.

Do you have any idea what the overall length of the prop might have been, the name of a common maker, or the type of aircraft it might have been fitted to?

Thanks again for your insights.

Cheers,

Jason

[pmdec]

Hi Jason,

Before any guess about what you asked, you have to:
- tell about the bolt holes diameter circle, the size of the holes (the best is using bolts or drill bits) and the size on the central hole,
- show pics of the two sides of the hub.

Regards,
PM

[jasong]

Hi PM,

My measurements may not be 100% accurate, but the bolt hole diameter circle is 18.5cm, the size of the holes themselves is 2 or 2.2cm and the central hole itself is 10cm.

Unfortunately I can't remove the steel plate from the other side of the hub which might reveal any additional stampings at this stage.

Cheers,

Jason

[pmdec]

Hi,
From your pic, I can't understand how the bolt holes circle diameter (18.5 cm) could me smaller than two times the center hole diameter (10 x 2 = 20 cm) as it seems, on the pic, that it is 290 / 113 = ~2.5 larger:

[Dbahnson]

Originally Posted by pmdec

Hi,
From your pic, I can't understand how the bolt holes circle diameter (18.5 cm) could me smaller than two times the center hole diameter (10 x 2 = 20 cm) as it seems, on the pic, that it is 290 / 113 = ~2.5 larger:

I wonder if those holes were drilled to accommodate the lamp fixture.

It looks to me as if there may have been three separate bolt hole circles, with two of them now filled with dowels.

If you look closely at the hub I think I see witness marks from the metal hub on the left side (yellow arrows) in which case the only original bolt holes would be on the circle marked with a few yellow "x"s, and they look to me as if they have been filled with wooden dowels.

[pmdec]

Originally Posted by Dbahnson

I wonder if those holes were drilled to accommodate the lamp fixture.

It looks to me as if there may have been three separate bolt hole circles, with two of them now filled with dowels.

If you look closely at the hub I think I see witness marks from the metal hub on the left side (yellow arrows) in which case the only original bolt holes would be on the circle marked with a few yellow "x"s, and they look to me as if they have been filled with wooden dowels.

Hi Dave,

It is difficult to tell from the picture but I don't think there are any dowel on tne Jason's hub: all are witness marks from the metallic hub. Look at this "T short" hub from a Ratier serial 639 we have. On the view I post, all is the same that for T long hub, excepted the bolt holes size (14mm vs 16).

But it is sure at least two holes have been redrilled on Jason hub, perhaps all of them.

On French props from this era (1925-1939), there are markings:
- on the flat side: Date of making and prop number and/or prop serial, on this one: 17 8 34 for 17th August 1934 and SE 639 for the prop serial. I don't know the meaning of the number 36 (the prop number is 247).
- and on one of the rounded side the serial again, the prop number, aircraft code and engine code and power, the airworthy stamp, and, very often, a code or a stamp for the maker.

Regards,
PM

[jasong]

Thanks PM and Dave. I believe the holes are are original and the "dowels" are witness marks. Two of the holes have been rebored, possibly to mount the hub on a wall before it was later repurposed into a lampstand.
Unfortunately I am not able to remove the steel plate from the base of the lamp which covers the other side of the hub that could contain stampings such as in PM's sample photo. I don't currently have access to the hub, but if I can get the plate off and photograph that side, I will upload the photos to this thread.

Cheers,
Jason

[pmdec]

Hi Jason,

If you access the hub, even if you can't remove the steel plate, please post two pics of the sides: faint markings could be there.

Regards,
PM