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T.6296 hub and replica propeller

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  • Dbahnson
    replied
    Originally posted by Garuda View Post

    I just had another look at the listing, and besides the price the seller only offers postage within the UK. I am on the other side of the world! I know that postage for such a propeller boss is not cheap, since the owner of another T.6296 boss very generously offered to send it from the USA to Australia, until he went to the USPS and got a quote for shipping!
    Mostly for future reference, propellers can be shipped internationally by using IPS, which uses discounts from FedEx, UPS, etc and also handles the brokerage service. I have shipped a number of full sized props around the world with them and their prices and services have been very reasonable. When I sell a propeller I crate it myself at my expense and charge the buyer only what it costs based on the IPS quote.

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  • Garuda
    replied
    Originally posted by JR44 View Post
    The seller seems to have doubled the buy it now price to £795 Plus £30 shipping.
    Dreamer!
    I just had another look at the listing, and besides the price the seller only offers postage within the UK. I am on the other side of the world! I know that postage for such a propeller boss is not cheap, since the owner of another T.6296 boss very generously offered to send it from the USA to Australia, until he went to the USPS and got a quote for shipping!

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  • JR44
    replied
    Yes exactly!

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  • Dbahnson
    replied
    Originally posted by JR44 View Post
    £550 now, bargain!!
    For me the bargain might start at 60 GBP and go down from there.

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  • JR44
    replied
    £550 now, bargain!!

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  • Garuda
    replied
    Yesterday I shaped the underside of the patterns up to section BB. The shape is slightly oversized, and approximate at this stage. In the first photo you can see where I checked the blade shape and angle against the ďextraĒ profile. It is very flat. Most RAF propellers have a curved underside until Section CC or DD. The T.6296 is unusual from the point of view that it seems to transition from a symmetrical section at Section AA to a flat underside approximately 2Ē outboard of Section AA. Although it does not seem possible, I was able to achieve this without any sharp bends or awkward transitions. It will be interesting to check the complete T.6296 to make sure that this is correct. I am very confident that my patterns will be very close. Unfortunately I have not been able to locate any photographs taken at the time. I suspect they are on an iPhone 4, which crashed. I have not been able to retrieve any data from this phone, but I will try to at least salvage the photos I took of the T.6296 blade.

    As a result of the lost data I do not have a record of the shapes of the top surface of the blade at Section BB. Starting from Section CC to the tip I have quite good measurements. The blade at Section BB was difficult to measure, so I was relying on photographic evidence. Still, I am very confident that I will be able to determine the shape of the blade out to Section CC. I will of course check these shapes and dimensions against the complete T.6296 at Narromine when I am able to get up there.

    The second photo shows the underside of the blade out to Section BB. The third photo shows how close I was able to get to pencil line on top of lamination 8, when I smoothed the laminations using information I had used to work upwards from laminations 1 through to 8. I am happy with the proximity to the pencil line. There is only a 3mm or so gap, which is about the amount I expect the original boss would have shrunk over the last century, hence the discrepancy. Closer to the boss the margin is much larger. I suspect I need to do a lot more sanding and shaping to obtain the correct shape. The fourth photo shows a quick check of the incidence at Section BB. The underside is slightly more shallow angle, which is ok because I will be able to rectify this with further sanding. Also, particularly towards the boss the leading edge radius tends to be larger than the trailing edge radius. As a result, the underside of the blade, even if it is flat tends to be at a shallower angle than the angle of incidence. The centreline is determined by the centres of the leading and trailing edge radii, not necessarily by the angle indicated by the underside of the propeller. When the leading edge radius is the same as the trailing edge radius, the flat underside is equivalent to the angle of incidence. It can be misleading if the principals used when designing these propellers are not known.
    Attached Files
    Last edited by Garuda; 03-01-2021, 08:31 AM. Reason: Grammatical error

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  • Garuda
    replied
    £795!

    Even when it was listed for £350 I was thinking to myself, how could I possibly get that much money together? Like most of us Iím sure, there are times when I have that much money to spend on something as non essential as a relic propeller boss, but this is not the case very often at all. At £795 + £30 postage / shipping it is now even more unaffordable.

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  • JR44
    replied
    The seller seems to have doubled the buy it now price to £795 Plus £30 shipping.
    Dreamer!

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  • Niduko
    replied
    Originally posted by JR44 View Post
    Here's another on ebay.
    'R.A.F. Wooden propeller hub from a WW1 British Reconnaissance/Light Bomber 1916'
    That's the heading I can't seem to find the item number.
    Hmmm, how much are they selling it for or betting right now? Would be curios to know about this specific model. I will try to find more info when I get back to my property in Spain here later on today after work.
    Last edited by Niduko; 02-12-2021, 11:00 AM.

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  • Garuda
    replied
    labour of love

    Yes, it certainly is a labour of love. I helped to restore a DH9. That was a labour of love too. A friend of mine is restoring a P.40, and we agree that we would be lucky to make $0.20 per hour from our projects, and even then this will only be possible if someone purchases them!

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  • JR44
    replied
    This is certainly a labour of love.

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  • Garuda
    replied
    Misalignment of laminations one and two

    The following three photos show the misalignment of laminations one and two. Once the holes are relocated, slightly anti clockwise, as viewed from the rear, laminations one and two will creep backwards, in a clockwise direction.

    Note the pencil line, visible in the third photo which indicates the leading edge of the propeller blade up to Section AA. I will allow about a 5mm margin, for shrinkage of the original boss, which will bring the leading edge to its exact location, within about 1mm.
    Attached Files

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  • Garuda
    replied
    Alignment of bolt holes and laminations

    The first photo shows the screws as I was fixing the laminations together. I have screwed these laminations together and unscrewed them many times. I will have to repeat this many more times. Whenever I am looking at the correct alignment of the laminations I check that the screws are straight. If they are screwed in at an angle, which can happen very easily if I am not paying sufficient attention, it affects the accuracy of the alignment of the laminations.

    The second photo shows the progression of each lamination. The angle between lamination one and eight is much larger than I would have expected it to be. It is, however correct, at least for Darracq built T.6296 propellers, since the blade I measured was manufactured by Darracq. It will be absolutely fantastic if I am able to find a T.6296 drawing. Other RAF drawings make reference to a separate drawing of the boss. I think I will be lucky enough to be able to find a T.6296 drawing, much less the prescribed drawing for the T.6296 boss. Still, even without the boss detail drawing I will be able to work the shapes and measurements out to a very reasonable degree of accuracy.

    The third and fourth photos show the discrepancy. Incidentally, a few weeks ago I decided to move the holes slightly anticlockwise, which will resolve these issues. It is yet another example of the constant revisions necessary to tweak the shapes and dimensions, in an effort to improve the accuracy of the reproduction propeller. Once the patterns are made, I will check them against the original T.6296 in Narromine, and make further adjustments as necessary. I will, of course have to allow for shrinkage. I have noted shrinkage of original relics of up to 12%.
    Attached Files
    Last edited by Garuda; 02-01-2021, 12:46 PM. Reason: spelling mistake

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  • Garuda
    replied
    Using the Augmented reality app to sketch lamination 8

    I was very pleasantly surprised by the accuracy I was able to attain using the augmented app to sketch the shape of lamination 8. I have a rough idea of the shape and position of lamination 8 from shaping the other laminations. Royal Aircraft Factory propeller laminations are numbered from the rear of the propeller. I know that the T.6296 has 8 laminations, from studying the broken T.6296 blade. Bosses and blades I have studied are typically 5 1/2Ē tall, but I suspect that the original timber used was 8 laminations of 3/4Ē to give a thickness of 6Ē. The shrinkage noted in the length of the blade is far less than the shrinkage I have noted in the thickness of the blades and existing bosses. This is a known phenomenon.

    The augmented reality app proved very difficult to use, but I am very happy with the results. It requires quite a knack to use effectively but I believe the results are very accurate. I can zoom in to a much greater degree than is possible with the iPhone alone. I can also vary the opacity. This is vital, since the only reference points I have to work from are the centre screw and the two screws placed where the bolt holes will eventually be drilled. The extended centreline of these holes viewed in front and rear elevation become the centreline of the propeller. For this reason it is vital that the holes are drilled accurately. When aligning the laminations I had issues with the alignment between the laminations and the jig I made to measure the progression of each lamination. I was easily able to measure these angles on the broken blade which I measured in 2011. Fortunately for me the half laps are a weak point of the design and this, of course is exactly where the blade broke off at the boss. I will explain the error, and the method I used to overcome it in the following few posts.
    Attached Files
    Last edited by Garuda; 02-01-2021, 01:05 AM.

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  • Garuda
    replied
    Laminations 1 - 7, up to section AA

    I have shaped the undersides of laminations 1,2,3,4,5,6 and 7 from the edge of the boss up to a point about 2" outboard of Section AA. It is oversized for two reasons. Firstly, I donít know the exact shapes and dimensions in this area, and secondly I donít know the exact angle and position of the blade as it emerges from the boss. With every relic and drawing I study for clues I am continually revising the shapes and dimensions. Although I donít know the exact dimensions yet Iím getting continually closer to determining them.

    The portion of blade I have shaped up to, about 2" outboard of Section AA is what I call the extra profile. It was not originally specified by the Royal Aircraft Factory when the T.6296 was drawn, but it has proven to be a very useful extra piece of information, since I am reverse engineering the design of this propeller without the convenience of access to a drawing of it. I measured the angle of the underside of the blade at two other locations. In addition I have an original T.6296 propeller blade tip. The more reference material I am able to obtain, the easier this task becomes.
    Attached Files
    Last edited by Garuda; 01-31-2021, 09:01 PM. Reason: correction to information relating to sectional shapes

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