FOUR BOLT 104 inch prop

[w1fik]

Gentlemen:
Here are the specs and the url at bottom of post should provide some pictures of this prop; the four bolts seem to be the big stumbling block. Any help to id this would be appreciated.

Shaft hole center to blade tip 52 in.
Overall length 104 in.
Hub Outside Diameter 13 in.
Shaft Inside Diameter 3.25 in.
Edge bullet nick 22" from center
Two mid-prop nicks 30.5" from center
Hub max thickness 4.875 in
Laminations mahogany 6
Hub mounting bolt holes 4 holes; 0.5" dia.
Bolt hole circle 8 in.
S/N stamped at outside of hub cut 226b
Outside hub flange depth 0.75"
Rear hub outer flange depth 1.25"
Rear hub inner flange depth 0.625"
Stencilled on left blade outside face:
"THIS PROPELLER NOT FIT
FOR FURTHER SERVICE
CONDEMNED DATE 5.11.19"

[Date numbers are stamped into wood]

http://picasaweb.google.com/lincoln1...ey=KSlfGt7ftp8

[Dwight]

The link does not work...
Dwight

[abufletcher]

Just take off the [/url] tag and then the link works:

http://picasaweb.google.com/lincoln1...ey=KSlfGt7ftp8

[Dave]

That's almost certainly a Liberty propeller, I believe either for a Curtiss HS1 or HS 16 flying boat. I just sold one like it (for someone else) on eBay a few days ago. I have one with the same drawing number (LP401) that was used on an H16. I think yours got rejected or stockpiled before the final hub drilling.

The center notch cut indicates that it was part of a 4 blade combination.

[Bob Gardner]

Firstly, the four bolt holes and their positioning suggest that the prop had a Rupp fastener. This was a German quick release device to enable props to be changed more quickly and consisted of four studs onto which the hub slid, and a modified central nut on the end of the drive shaft. Thus only one nut held the prop on instead of the usual eight. The four holes for the studs did not go all the way through the hub.

On this prop the four holes appear to go through the boss, if the photographs show both sides. If so, it probably isn't a Rupp hub, but a later modification when the prop was out of service, possibly for use as a ceiling fan.

However, six laminations is not common for a German prop.

The shape of the prop is very much similar to a Lang Propeller design, drg no LP710. This was widely used by the British with the principal rotary engine; Gnome, Le Rhone; Clerget; on aircraft such as the Sopwith Pup and Strutter, the Avro 504 and the AW FK8. But this prop was 108 ins in diameter c.f. the 104 ins on yours. Does yours shown any sign that 2ins have been cropped from each end? Lang did make a prop of 104ins diameter for the Sopwith Camel, but it was not widely used and I don't know if it was of this shape.

Although Lang was a British Company they set up an American subsidary company in 1917, which stamped the prop data around the edge of the face of the hub rather than in the European style where it is stamped on the curved side of the hub. Are there any traces of these stampings on your prop?

With regards,

Bob

[Bob Gardner]

Ah! Just read Dave's post. The answer seems to be that this is a Lang prop made by the American company. I don't have LP410 listed so I'll add it to my database. Anyone got drg nos from other American LP props?

With regards,

Bob

[Bob Gardner]

Hi Dave,

I have just read your ebay description of your prop and I see that you think LP in the drg number means Liberty Props whereas in England LP indicates Lang Propellers; and Lang Props had an American company. And this prop is the shape of a Lang Propeller.

Have you seen a prop with a Liberty decal stamped with an LP drg no? Did the Liberty Propeller company buy designs from Lang, or subcontract to them? Or was the Liberty prop co. a later name for the Lang outlet. Or did Lang subcontract an order to Mathews because it didn't have the manufacturing capacity. This seems more likely than Liberty getting the design from Lang and then subcontracting to Mathews. What do you think?

Postscript; Is there a connection between Liberty props and the Liberty engine company?

Bob

[w1fik]

Thanks!

Thanks, gentlemen, for your excellent discussions. I have corrected the link to picasa and added several more images which might help with some of the questions raised so far.
There are no signs that the prop was cut down to 104 from 108 inches; the riveted sheathing at the tips looks original and in good condition. One of the images added shows what I have always considered to be one of the 'bullet nicks' in the prop.
As a youth, circa 1952, I found the prop in a field near Concord, Massachusetts, a few miles from Hanscom Air Base.
Regards, MAB

[Bob Gardner]

Thanks for the photos. The side view shows very well how the two halves were bolted together. Dave Bahnson (who founded this forum) has identified the prop but I look forward to his views on who made it.

With regards,

Bob

[w1fik]

Lang "shield" decal and LACK of bolt holes

Upon carefully cleaning subject prop, we find:

a. Remains of a "shield" shaped decal 2.75 in wide and 4.0" high, placed 23.5" from center of engine shaft hole on leading edge [image added to picture link Jan 05]. Shield shape and size appear quite similar to the excellent images of Lang Mfg. decals available elsewhere in the WP Forum.

b. "Bolt holes" in center hub are not drilled through; four drill-point indentations on both sides of hub are only 3/8" deep. There are no traces of stampings in the hub other than the previously mentioned "226 b".

c. Material from which prop is laminated appears to be clear mahogany.

d. The undrilled hub bolt holes and fine condition of tips, etc. seem to support Dave's contention that this prop was 'rejected or stockpiled' before being fitted to an aircraft.

e. However, the apparent round bulllet-like nicks, especially in the leading edge of the prop, are hard to explain. Could a blank, unfinished prop have been set up to test the timing of guns which were designed to fire through the prop?

Regards, MAB

[Bob Gardner]

Well done! That shield must have been difficult to find and it is certainly a Lang Propeller shield, which matches the shape of the prop and the drg no which begins with LP.

The four bolt holes are a puzzle. Here are my thoughts.

They are the female side of four studs in the other prop to ensure that the two halves marry up properly. This seems logical, but I haven't seen it before. Dave, have you seen four holes on the contact face of such a prop, which would meet the other half?

Second thought is that Lang Propellers experimented with a Rupp fastener captured from the Germans The spacing is very similar, but then it would be because both these ideas invlolve four locating studs.

Regards,

Bob

[Dave]

Hi Dave,

I have just read your ebay description of your prop and I see that you think LP in the drg number means Liberty Props whereas in England LP indicates Lang Propellers; and Lang Props had an American company. And this prop is the shape of a Lang Propeller.

Have you seen a prop with a Liberty decal stamped with an LP drg no? Did the Liberty Propeller company buy designs from Lang, or subcontract to them? Or was the Liberty prop co. a later name for the Lang outlet. Or did Lang subcontract an order to Mathews because it didn't have the manufacturing capacity. This seems more likely than Liberty getting the design from Lang and then subcontracting to Mathews. What do you think?

Postscript; Is there a connection between Liberty props and the Liberty engine company?

Bob

Bob,

No, the LP in this does in fact indicate Lang Propeller. I'll dig out a letter I have from the teens directing various major companies to stamp their props to indicate the manufacturer, but I do recall that Lang (of America) was "LP", and I remember that the American Propeller Co was "PP" (for Paragon Propeller).

With respect to the holes, to me they don't even look fully drilled, although that part is hard to tell. Again, I suspect that it was rejected at some phase of its construction or possibly left undrilled on purpose for some reason, but I think it was likely intended to be used on a Liberty engine.


EDIT:

Actually, I already posted those abbreviations on this page, with the asterisked items being taken from that letter to the manufacturers. Generally, those letters will proceed a drawing number, very similar to many British props.