FTS Projects

[AchimEngels]

Hope the Thanksgiving hollidays have been a joy to the US community.

Make sure to store the rest of your turkey properly.....

We are in the final stages of the manufacture of the turnbuckles. All 60 we need are done and only a few of them still need to get the eye hole drilled into them.

Here is how I do it.


This showes a special shaped drill to make the rounded hole into the eye.

I have been able to locate the set of norms used at the end of WWI to simplify aicraft construction. As you know we Germans are big in standardising things.

These norms have been issued by the "Norms Committee of the Airplane Industry" in late 1918, so they may not apply at 100% to the shape of the turnbuckles used by Fokker during early 1918.

However, these are the closest sources we have found so far.

As you know I am one of these rivet counters, and we will certainly not know for sure until we see the original order Forms by Fokker that confirm what Company product was used. And even if we have this, we do not yet have the original working drawing from that company.......

O.K. All I have to say is that I am satisfied with our result. The only discrepancy indeed is the tapering of the barrel. We did our´s straight. These documents confirm that the taper was from 6.2mm in the center to 5.6mm at the tip. Ours are straight 6mm of diameter over all lenght.

I am talking about No. 4 in this documents. All other dimensions are exactly the way we did. I really wonder about that...... B)





Enjoy!

Achim

[jumpinjan]

Achim, You know my mind was buzzing as to how I would produce the holes in the ends of the turnbuckles (during the earlier part in this thread) and I must admit, I didn't think of doing it in the way that you have demonstrated. That's a more elegant way of drilling the holes. I noticed in the drawing that the holes are completely radiused and yours are just chamfered. Are you going to complete the radius? Are there any wire thimbles that are inserted in the turnbuckle eye or is there just the bare cable through the eyes? Just curious.
Jan

[AchimEngels]

Hello,

Curiosity is always a good thing.

Actually the norm drawing is diferent from my eyes in this respect. Since I wanted to leave the eye bolts slightly thicker. Therefore the radius is not going all through the eye as seen in the drawing.

I did this to make sure I reproduce the actual procedure of how Wullffo´s original turnbuckles have been made. You can clearly see the drill marks there, although some are forged. Non of these original eye bolts is identical, nore is the shape of the rouded inner surface of the whole. Most important appears to be that it is there to prevent the wire from getting twinkled.

However, doing it exactly as seen in the drawing would not mean a problem. All you have to do is to carve the drill accordingly.

Here are some images of the first use of the turnbuckles in the frame ant their attachment.


First set of new made ferrules











Enjoy!

Achim

Achim, how much tension is put on the wires supporting the airframe? Do you adjust by number of turns or until a certain pitch is given after tapping the wire? This is something I have been wondering about for years.

[AchimEngels]

Hello Tim,

Happy to see you here finally!

Well, good question about the tension.

The steel wire itself is of 200kg/square milimeter in tensional strenght. This material is quite hard.

You have to carefully meassure the distance of one half of the loop of the wire in this design, because this determines the lenght of the wire on one side.

There is no way to adjust a too long loop by pulling it through the corner gusset using the turnbuckle. And on the other hand you have only 20mm way left to bring the required tension in, using these small turnbuckles.

The tension given to the wires is not regulated in any document I found, you have to make sure to adjust it at least equally to two opposed wire systems.

We do it by a number of turns and by feeling and by listening to the sound of the wire. We have a tension meter as well and usually check for a uniform tension in each bay in the end.

To be honest, I have no source as to how they did it back then. I suppose just by feeling since it would work well.

Once the wire is put under tension there is no way the frame could move in any direction.

The wires provide the ridgidy of the structure.

And remember: Final tension is applied to the wire under load in flight, so the less you apply in static condition, the better it is. There is no need to pull the wire as tight as possible. This just applies a not neccessary load factor to the turnbuckle.

Achim

Thanks for the info Achim. I had always thought that braided wires were used and was intrigued to see the picture above with the single strand looped together.

It's good to see that your projects are coming along successfuly.

[Volker_Nemsch]

Hallo Achim!

Nun hab´ ich eine ganze Weile nicht an den Arbeiten teilnehmen können und sehe jetzt erst die enormen Fortschritte. Das muß ich mir wirklich irgendwann mal selbst ansehen ...
B)


Ach ja, ich bin jetzt wieder regulär per mail, Forum und Telefon erreichbar. Wie sieht es denn mit dem "Spad CD" und der anschließenden Übersetzung der "Fliegerei CD" aus?

Bis dann!
Volker

[AchimEngels]

Hallo Volker,

schön dass Du wieder da bist!

Great to have you back!

Sotry, but as you can see we have been really busy here.

I am working on the translation, but the progress is slow.

Come on over to my house as soon as you can. We can have some beer and talk aircraft all day long!

Achim

[retread]

Achim,
How much time do you figure per turnbuckle (machining)? Also, is the brass hardened? It seems in a worse case scenario the threads on the turnbuckle body would strip before the wire gave way. Did you state the diameter of the wire used? From the photos it looks to be no more than 1/16th in. via the (old) English Standard . In the neighborhood of 15-16mm diameter?
As regards Tim Sielbeck's observation about stranded wire (or the lack of it) do you know if solid wire was the norm in Germany or only with particular types of aircraft? I know Curtiss often used a 19/1 galvanized strand, I believe of varying diameters.
Sorry for the flood of questions but one leads to another. Beautiful work and a tremendous thread.
Thanks

[AchimEngels]

Weldboy,

It takes me almost 2 1/2 hours to get one tunrbuckle done until it is finished. Remember: this is pure hand work.

The brass is hardened stock material.

I doubt that the thread would give way. We have roughly calculated the maximum load of this design to almost 800 kg for one wire loop (remember that the thread indeed is the unknown factor in the equation). You have to see that the main advantage of this design is the fact that Fokker indeed used a continous loop of the bracing wire, so any load applied is devided into two.

However, we have the load test results of the McCook Field report that was conducted in the 1920ies and the weak point in this design actually was the welded steel frame structure and not the wire or the turnbuckle. We are preparing right now to conduct a semiliar test with a dummy fuselage frame cross section including this wire bracing system. We hope to replicate the efffect seen in the McCook field report photographs and reports. We also plan to film and photograph this strenght test and post the results here.

The diameter of the steel wire varries from front to rear. In the cockpit area and immediately behind it is 2mm, while it reduces to 1,5mm over 1,75mm towards te rear section. The tensional strenght of the wire is 200 kg/sqmm.

In Germany normally solid wires have been used for internal bracings. But I am not knowing enough about all designers, so there may well have been some who used stranded wires as well. Fokker did not use stranded wires for internal bracings, at least not as far as I know. But for sure not in the D.VII!

Enjoy!

Achim

P.S. Don´t hesitate to ask questions like that!