Inswinger crossbow (Rubber powered)

First topic message reminder :

Here is my one version of the "in-swinging,springs (rubbers) propelled crossbow". It came from various inspirations like: oss William tell, French ww1 grenade launcher,manubalista etc...
The mock-up.



The test bench



The draw length: 18"



Next step is to put the rubbers and the winding-drum under the side
frame and the levers in the upper side of the frame. I actually use only
two packs of 15 rubbers but i can put lot more i will see that letter
on. I will probably use this trigger assembly:

Very nice compact design. I one I just finished is about 44" long! Hope it perform as well. Keep us informed of your progress.

Todd

Looks like we have a bull-pup revolution on our hands, mates.

See lots of cool little details in this build. See you've changed up the trigger mech a little, care to share what you did differently?

[EDIT]...would also be awesome to see it at full draw. Perhaps maybe even a video of it shooting (you can go full out in French, that would be a kick to hear)
Over all - I'm just loving it. Great to have you with us, jeep!

Ivo

It almost good but some off the basic materiel not strong enough , the 3mm alloy sheet used for the two triangular arms are to week, when crossbow is spanned they are banding giving a wrong position to the swinging members.

To fix the swinger i use bolt and rivet, it is not sufficiently rigid.

I am re-enforcing the alloy frame whit metal band.

The trigger will be more stronger, I use basic bull pup system

The work of the afternoon: Trigger assembly.

Stronger frame: Metal band assembly with rivets

Version n°3: all black components are new and stronger:

spanned but whit one rubber bundee of 15 more each side total 15 rings x 8 = 120

...

I can do it lot more powerful adding more rubbers but i will need a spanning device actually this is the maximum I can span whit hands. That will be for the next version :gear wheel new trigger welding for assembling.

looks awesome, I can see how that would be hard to cock with that string angle!

Have you taken any shots with it yet?

Todd

you are right Todd ! nearly impossible to cock whit this angle and a to big power even whit gloves . I try several spanning apparatus (rope,pulley,winch with hook .) no one work properly the draw-length of the in swinger is so long !!! this is also one of the few drawback of the bull-pup design :the frame is closed.. So the elegant and efficient solution will be a gear winch pulling a mobile trigger system. It is wy I will have to build a new one : the tiller architecture is different. width,groove etc...
Yes I did shoot , very powerful very nice and a lot of potential whit better materiel and less friction due to poor building!! I will do a video at the end of the week.

Try building a "sled" for cocking it Jeep. the acute string angle will want to "ride" on it so the sled might need a small pulley on each side. After engaging trigger, the string will be tight against the sides of the sled. A pulley on each side would allow the sled to move back out of the way without interference.
Now you know why I like the TAC15 crossbow platform to bolt a torsion "riser" to!

Alternatively one could leave the trigger set in place, and use the handle to move forward and "grab" the string bringing it back to the trigger. JoergS uses a similar design on one of his slingbow designs.

I am guessing since you are encountering problems of acute string angle that your draw weight is up 60 lbs or thereabouts. Its gets quite painful after a shooting session using the hands.

I just took delivery of a new Spiderweb 1.5 xl model rated at 450fps. I look forward to testing 150 - 200 lbs pull prototypes!

I will be looking at compression springs now as opposed to working with extension springs. Real left and right wound torsions are a little tricky to work out in such a short time for the ATA show in January.

The simplicity of the "Big Joe" rubber band power is a very intriguing and affordable design to explore. It also has a great history behind it!.

Am following your progress and good to see you progressing so well and so fast!.
you will never to be able to go back to an outswinger design...

Well still progressing here is model n°4 ! I decided to rebuilt entirely the "bow" regarding the the weight ( almost 150#) the frame were not stiff enough . Doing this I change all the dimension and I now I will have to rebuild a new stock!!!

;

;

I already stretch it but now the the draw length increase and i can't test it properly before building the new stock and new trigger!!! Endless work you say warhamer!!!

Lot of time needed to choose the stock design ,to create a new trigger system . Thank to the forum knowledge and proposal, it use to be a great ,inspiration .Very few component from the previous model.Here the new stock: ply wood,alloy cherry wood and brass.

Here the evolution of the baby during conception!!!

Actual model, new stock,new trigger,new colour, new sight:

Front sight:

Back sight (before painting): It can be folded when red dot in position

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