WW2 Big Joe 5

Hello
Member from this forum for some month (but experienced French crossbow builder) I decided to bring my contribution whit one of my work: The OSS BJ5 replica. For this, many thanks to Dr Brunner whit his constant help and encouragement . I bring some modifications due to the fact that I have not the wealth of the OSS research department and I had to build it whit the usual hand tool that you by in any tool general store...I am not sure to master the pictures uploading. First a picture from the original,then my version in detail.

Don't pay attention to dates on the pictures the first camera never could be set in the right time!!!
If any questions ?

Wow that looks great! Definitely something different. How does it shoot? Do you have any stats on it like draw weight or arrow speed?

While I am asking questions, Do you have any information on the original, like if it was ever used or was it an OSS proof of concept?


You certainly captured the feel and look of the original. I really like this.

Deleted
Paul

Thank Basilisk.
THE LBJ5
Velocity: 180fps
Accurate lethal range: 60 yards/150 yards
Extreme range: 260 yards
dart: 44g (678 grain)
rubber pull: 550#
150 rubber ring x2 = 300 rubber ring
Draw 10"
You can find those stats and a lot more in the Bible of Dr BRUNNER.:
THE OSS CROSSBOW,
ISBN-0-932572-15-4

Some of the different models where send for trial in England,others in Sloma in South Pacific they where tried by Carlson's raiders, Alamo Scouts in new Guinea. But no report of there use in operations.
All of the different modèle (little Joe,Joe pedal, big Joe 4/5/6,William Tell) where proposed to the allied, but at this stage of the war other silents fire arms where in service some very efficient (verlord,Delisle,etc..)and preferred. Military are quite traditional,they believed and feared that a Jape whit a bolt in the neck would run in circel yelling like a chicken!!! Of cource they where wrong (Australian had Arrowspeed crossbow in New Guinea and at least they used for improve the pot!!)but the real weakness of those crossbow are the rubber: very fragile to heat greas moisture and difficult to replace.It is interesting to see that Since end of 1942 to 1945 a hall department of North West university work for this and make incredibly complicate a simple concept we have an expression for this in France : to produce a "wind machine".Nerveless this crossbow is incredibly interesting to produce and it work pretty well.

Thanks for the details.

Not quite the speed machine one would expect but I suppose with weight of the moving parts and what not it would keep the performance down.

But once again nice looking reproduction. I really like seeing people do out of the ordinary or odd reproductions. I guess I just like the strange and arcane.

It is not what I wanted to say: I mean that some time when you gather lot of brilliant brain around the same problems ,the result will be very complicate rather to be simple ...But you are right 180 fps for 500# is disappointing... This is the main problem whit rubber: when you stretch it quickly it produce some heat and lost lot of power and if you wait before realising the power drop even more!!! Richard Middleton produce a brilliant demonstration of this phenomena on his book: "Man-Powered Bullets". Here the rubber unit template :

Some rubber rings

jeep wrote:It is not what I wanted to say: I mean that some time when you gather lot of brilliant brain around the same problems ,the result will be very complicate rather to be simple

LoL That is so so true. I really get how that was originally designed. I think I have been on similar committees unfortunately



But thanks for the information on the limiting factor of the rubber. I do like the drawing

Hi jeep,

For the past few days I've been catching up slowly on my reading of the webarcherie forum. Very slowly and I haven't gotten to your build yet. I only know four languages, but it proves that knowing five or six would have been better.

Your build is very interesting, especially considering it's a "replica". The fact that you built it out of readily available materials with common tools is also another point worth alot of appreciation and experience gained in doing so is unmatched.

I have done a little bit of research on this crossbow a few years ago, but unfortunately I was also researching everything else at the time and didn't have a chance to truly dedicate myself to this particular design. However, it was very inspiring in a sense that it presents a few very interesting structural solutions that can be used in synthesizing new designs.

I don't have access to a computer at this moment, so all I can do is complement you on the job well done and thank you for this fantastic contribution. There is lots to discuss in this crossbow and perhaps you will be interested in hearing/seeing some unique thoughts we have floating around on this forum that might just fit as improvements on the given platform.

Thank you for sharing, it was a pleasure viewing this build and I hope to discuss it further in the near future.

Regards,

Ivo

Thank IVO. Of cource I would be interested to discussion about this item end possible improvements.I think that the designe is pretty good but it can be simplify ,it should be possible to use other mean of propulsion, I am sure engineers can tell us that new elastic tread can replace rubber whit better resilience and stability like carbon or else. In this case whit the use of lighter material for the frame this crossbow could be near perfect.If you want to see my work in webarcherie my pseudo is OWL