# At last: A powerful Thera Band crossbow



## JoergS (Dec 17, 2009)

OK, it was time for this.

Took the trigger part from my slingshot pistol and eliminated the two problems I had with it:

1. The low power (I simply gave it 87 cm draw length)

2. The dangerous and awkward loading (I added a sliding fork, so you can load it easily and cock it when you are ready to fire).

This is technically and legally a crossbow now, so you have to be 18 to own it in Germany (no problem here - sigh...).

It is a great shooter! I am amazed by its accuracy. I may add a good sighting system.

Enjoy!


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## harpersgrace (Jan 28, 2010)

Congrats, That is a great design can't wait to see it after you upgrade it


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## shot in the foot (Jan 3, 2010)

Sorry but cant see the point unless its a fun thing, some air rifle is shorter and more accurate, sorry just my thought, but i did like your last slingshot, jeff


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## JoergS (Dec 17, 2009)

Jeff, most air rifles are a lot weaker than 39 Joules. Here in Germany, they are limited to 7,5 Joules, 1/5th of what my weapon does.

I could put stronger bands on it and go to 80 Joules or so... with 19 mm lead balls.

Jörg


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## harpersgrace (Jan 28, 2010)

I'm luck in that my shoulder problems aren't too severe (most of the time) so I can still shoot a standard slingshot with light to moderate bands, if however it gets worse something like that might be a option, plus it is quieter than my air rifle ( a old Sheridan Blue Streak ) and looks like a lot of fun....


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## Skit Slunga (Apr 14, 2010)

Love it! Is the forward cocking piece full length or a short section that telescopes over the frame?


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## JoergS (Dec 17, 2009)

Short section, just enough to make it stable (approx. four inches). Full length would be too much friction, weight and extension (it would protude very far in cocked condition).


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## Tex-Shooter (Dec 17, 2009)

Very nice concept Joerg. I am impressed!!! -- Tex


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## Fork Hunter (Apr 19, 2010)

True German engineering ! Outstanding concept Joerg !


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## watcher by night (Jun 14, 2010)

That's such an extremely fun-looking crossbow design, Joerg! One-handed operation, even...
I loved the big holes it made entering and exiting the "tin" can...









I really like the idea of first securing the pouch/shot in the trigger clamp, then stretching the bands forward. That seems like much better ergonomics (not to mention safer) than struggling around with drawing a loaded pouch back and trying to set it in the clamp under tension.

I've seen a more conventional crossbow (with a fiberglass bowstave) that used a concept a little bit similar, in that the crossbow string is latched into place on the trigger "nut" and then a long lever forces the bow assembly forward, bending the bow to full draw.... unfortunately I can't find a link to it tonight (after just having spent a few minutes searching). This seems pretty new for a slingshot though...

Anybody trying to build their own version might (?) be able to use a bar clamp like the one shown here...
The bar clamp might take enable sufficient support and locking for the sliding fork that locks in an extended position.
Not sure about any easy-to-find off the shelf components for making the nice rollers clamp...


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## A+ Slingshots (Jan 22, 2010)

IMPRESSIVE!!!!







I need one!!!!


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## JoergS (Dec 17, 2009)

watcher by night said:


> That seems like much better ergonomics (not to mention safer) than struggling around with drawing a loaded pouch back and trying to set it in the clamp under tension.


Yes, that was my main concern when I made the original pistol - I hit my thumb accidentially while trying to draw back the pouch, it slipped before I could put it between the rollers.

This works. Next weekend, I will make stock and also add a red dot sight.

Jörg


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## JoergS (Dec 17, 2009)

Have bought this stock today, will put the slingshot crossbow into it and attach a red dot sighting system.


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## Brooklyn00003 (Feb 28, 2010)

I am looking forward for this to come together.Its a great idea.


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## Rayshot (Feb 1, 2010)

Very good concept with the extending and shooting so as not to loose energy. Even though I am not "gun type", I love that creation!!


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## watcher by night (Jun 14, 2010)

Hmmmm.... just took "stock" of the situation (hee hee, bad pun alert)...

It will be a treat to see the mechanical action bedded on that wooden stock, with red dot sight installed. 70 meter gongs, look out!

By the way, I found the unconventional type of conventional (with a bent bow) crossbow I mentioned earlier in the thread. It is also an interesting design, and similar to Joerg's new crossbow in that one first engages the string (or pouch) before actually bending the bow (or stretching the power bands). It's called a "Twinbow", and you can see a Youtube video demonstrating how it works at the link below. The stock actually is hinged like a scissors and breaks open to move the entire bow/string assembly backwards to engage the trigger nut... then the bottom half of the stock acts as a cocking lever to force the bow assembly back forward and bend the bow.

Twinbow on Youtube


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## JoergS (Dec 17, 2009)

I just upped the rubber... added a third strip of Thera Gold per side. 50% stronger than hunter bands.

Clocked it at 63 m/s with the 26 gramms 16 mm lead balls! That is about 52 Joules.

Still manageable, but that is pretty much the limit.

Serious power... this will break bones, and it is very accurate. Pretty much the ideal poacher's weapon.


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## Brooklyn00003 (Feb 28, 2010)

Cool!
This is asking for some serious destruction video.There will be one right?
Ps :I miss those old destruction videos with the meat and etc.


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## JoergS (Dec 17, 2009)

Good to hear SOMEONE likes my meat tests... they got me banned in a couple forums, censored in some more, and they pissed of the German paper puncher fraction big time. I rather enjoy them anyway.

I could shoot as hard beforehand, but with this weapon, you can hit RELIABLY with that kind of power. Makes a big difference.

Jörg


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## smitty (Dec 17, 2009)

I miss the slow motion studies and the destruction of full cans and such. My "Gloveshot" is fun to destroy stuff with too ! The slow motion videos have helped me a lot when designing my own slingshots to shoot. Watching stuff blow up is just pure fun to see.







Thanks a million for all your efforts Joerg !

Best regards;
Smitty


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## dgui (Jan 12, 2010)

Very Impressive.

Could you translate into FPS.


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## harpersgrace (Jan 28, 2010)

*1 meter = 3.2808399 feet*
there are any number of conversion sites if you do a search then all you have to do is plug in the value you want to convert no math involved


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## JoergS (Dec 17, 2009)

The speed is 207 fps. Not bad for a 16 mm lead ball (.63", 416 gr.).


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