Saturday, July 13, 2013
Tuesday, July 9, 2013
Sculpted German Walnut
I have a very old walnut tree in my garden. It still gives us many walnuts, but it also has several dead limbs. So I took my trusted chain saw sword and cut one of them off.
It must have been dead for a looong time, bone dry and with lots of growth on the bark.
Stripped the bark of and applied the outlines - a narrowed version of the Hand Mortar design.
I cut the frame out and did the file- and sanding work.
The marrow was brittle, I removed it and filled the holes with epoxy+sawdust.
Here is the piece oiled and sanded (80 grit), awaiting the polyurethane coating (I always like to do that on pieces that are as old as this one).
Will post some pics from the final finish, as soon as the coatings are done.
It must have been dead for a looong time, bone dry and with lots of growth on the bark.
Stripped the bark of and applied the outlines - a narrowed version of the Hand Mortar design.
I cut the frame out and did the file- and sanding work.
The marrow was brittle, I removed it and filled the holes with epoxy+sawdust.
Here is the piece oiled and sanded (80 grit), awaiting the polyurethane coating (I always like to do that on pieces that are as old as this one).
Will post some pics from the final finish, as soon as the coatings are done.
Monday, July 8, 2013
Monday, July 1, 2013
The "TUMahawk" University Project
The loverboy of my niece Julia (she lives with us) is studying engineering at the Technische Universität München (TUM). He had to design a survival tool and his group settled on an axe - but with extra gimmicks!
The boys visited me yesterday, we had some fun.
The boys visited me yesterday, we had some fun.
Monday, June 24, 2013
Tuesday, June 18, 2013
Spiegel Online covers Jörg Sprave
SPON (SPiegel ONline), one of Germany's biggest online news magazines, has covered The Slingshot Channel with an article that made the formats title page yesterday.
Read the article (German language)
SPON had almost 200 million visits in May 2013 - after bild.de (a much more low level magazine that covered me a few months ago), it is number 2.
I think the reporter did a really good job in capturing my personality.
Read the article (German language)
SPON had almost 200 million visits in May 2013 - after bild.de (a much more low level magazine that covered me a few months ago), it is number 2.
I think the reporter did a really good job in capturing my personality.
Monday, June 17, 2013
Thursday, June 13, 2013
Mini Pistol - now 51 lbs draw weight!
Added some more rubber - now it has 8cm of TBG per side, pretty serious. This is over 50 lb draw!
Still a toy... but of the scary type!
Still a toy... but of the scary type!
Tuesday, June 11, 2013
Mini sling pistol
I had so much leftover plywood from the big projects that I decided to make a small, fun pistol.
Design is pretty standard, but for a more gun like look I turned the three layers of 9mm plywood into a round rod, then attached the handle and trigger guard (made from 18mm plywood).
It shoots pencils (see how nicely the muzzle fits? Epoxy, mixed with sawdust, and an oiled pencil made this work).
I made a "devilled pencil" with a nail. Some string (constrictor knot) stabilizes the tip. Works great!
A fun little toy to play and plink.
Design is pretty standard, but for a more gun like look I turned the three layers of 9mm plywood into a round rod, then attached the handle and trigger guard (made from 18mm plywood).
It shoots pencils (see how nicely the muzzle fits? Epoxy, mixed with sawdust, and an oiled pencil made this work).
I made a "devilled pencil" with a nail. Some string (constrictor knot) stabilizes the tip. Works great!
A fun little toy to play and plink.
Saturday, June 8, 2013
Wednesday, June 5, 2013
Potato Bazooka Progress
Pretty much done! The final touches will be done when the film team is here, so there is some footage from the built.
Also, had a reporter from a huge German on/offline news magazine (Der Spiegel) here today, he wanted to see me shooting many different pieces of my arsenal. I actually had to prepare some of the older weapon, exchanging bands and so on.
Most impressive was the impact of the witch bazooka with the bayonet on a stick. It shot all the way through the 40mm (1.57") massive oak board... with a heavenly sweet sound, too.
Also, had a reporter from a huge German on/offline news magazine (Der Spiegel) here today, he wanted to see me shooting many different pieces of my arsenal. I actually had to prepare some of the older weapon, exchanging bands and so on.
Most impressive was the impact of the witch bazooka with the bayonet on a stick. It shot all the way through the 40mm (1.57") massive oak board... with a heavenly sweet sound, too.
Monday, June 3, 2013
I want to shoot potatoes against a wall, against watermelons, and also test frozen ones, too. Should look cool on slomo!
The design is a bit like my cannon with winch, but this time I want a faster cocking method. Just a normal pull up slide!
I used the clamp method from the car sized cannon, but the trigger from my trusted old bone crushing crossbow. That trigger has the advantage of less play.
Effective draw length is 106 cm (total length 130 cm). I tested two full TBG bands per side, but then it is cockable only in the vise. But it holds! Normal shooting strength is one TBG band per side, still a nice 36 kg draw.
If you pull up the sled, it locks back automatically thanks to two hooks at the end.
The potatoes fly far, and fast. This hit against a rock left a wet stain and some mashed potatoes, that is all :)
This cannon will need much work on the looks. I want to make a bazooka out of it, with a pistol grip. But it already is shooting nicely.
Thursday, May 30, 2013
Mesquite fork
John from Texas gave me this natural fork. It was very rustic, and obviously the grubs had been at it for some time. Seems like it was dead for at least a year, bone dry for sure.
First, I removed the bark. The grub canals came to dailight quickly.
I then decided upon the shape. I wanted to retain the forward canted angle of the fork, and at the same time I needed enough solid wood to make this a functional, strong slingshot. Took me while.
Then I cut the front and back. The typical hammer handle shape emerged for the first time. You can also see that the grub holes aren't that bad.
I closed the grub canals with a mix of the wood's own sawdust and tow component epoxy glue.
Then, I filed everything flush and started the sandpaper work. Here you can see it at the 80 grit stage.
This is the final slingshot, all polished and oiled (raw linseed oil)!
Some more pics of the beautiful frame:
First, I removed the bark. The grub canals came to dailight quickly.
I then decided upon the shape. I wanted to retain the forward canted angle of the fork, and at the same time I needed enough solid wood to make this a functional, strong slingshot. Took me while.
Then I cut the front and back. The typical hammer handle shape emerged for the first time. You can also see that the grub holes aren't that bad.
I closed the grub canals with a mix of the wood's own sawdust and tow component epoxy glue.
Then, I filed everything flush and started the sandpaper work. Here you can see it at the 80 grit stage.
This is the final slingshot, all polished and oiled (raw linseed oil)!
Some more pics of the beautiful frame:
Wednesday, May 29, 2013
Be a TV star!
Next week Friday (June 7th), a German film team will visit me in my home at Burgkunstadt/Oberfranken.
They'd love to see and film some other slingshot fanatics, and therefore I cordially invite people to come over then. Filming will be in the afternoon, we'll do some slingshot shooting during and after that. BBQ in the evening!
Let me know if you want to join us.
jsprave@macrosystem.de
They'd love to see and film some other slingshot fanatics, and therefore I cordially invite people to come over then. Filming will be in the afternoon, we'll do some slingshot shooting during and after that. BBQ in the evening!
Let me know if you want to join us.
jsprave@macrosystem.de
Lawrence Ross and Waterhead Show
I had a great (recorded) chat with the three guys from the LRWS. Enjoyed it a lot!
The podcast is here:
Monday, May 27, 2013
Rubber science: Slingshot fridge
As shown earlier, rubber stores energy thermally. If you stretch a rubber band, it gets warm. If you relax it again, it gets cold.
This video uses a specifically designed contraption that uses this effect to cool a can of beer with nothing more than muscle power and rubber. In fact this may be the first rubber based artificial cooling device ever. Wikipedia is by now in need of an update!
The video clearly shows how an (empty) beer can is cooled down by 2 degrees centigrade in an instant. This is the proof of concept - the rest is design optimzation.
Of course the contraption doubles as a mini trebuchet - after all, this IS The Slingshot Channel :)
This video uses a specifically designed contraption that uses this effect to cool a can of beer with nothing more than muscle power and rubber. In fact this may be the first rubber based artificial cooling device ever. Wikipedia is by now in need of an update!
The video clearly shows how an (empty) beer can is cooled down by 2 degrees centigrade in an instant. This is the proof of concept - the rest is design optimzation.
Of course the contraption doubles as a mini trebuchet - after all, this IS The Slingshot Channel :)
Sunday, May 19, 2013
Greetings from sunny Gran Canaria!
No new video today, The Slingshot Channel is on vacation for a week!
Sunday, May 12, 2013
RUB-15: First "Upper Slingshot Receiver" finished
Even though I am not happy with the looks, the thing works too good to be thrown away... so I painted it black and attached a scope mount. I used a cheapo red dot.
I think I will make several other uppers, now that I know how this works.
I think I will make several other uppers, now that I know how this works.
Saturday, May 11, 2013
Toilet brush machine gun: Getting closer
Worked some more on the weapon today. Added a nice front handle, Moorhammer style. Banded all four forks up.
I quickly encountered a huge problem: Return to senders and misfirings!
Those returners are dangerous. I mean seriously dangerous. One hit the door right next to my head... two inches to the right and I'd be in trouble now.
I don't really know what is going on - what I found out is that it works as long as you turn really slow. The fast spinning action of the battery drill is probably too much, destabilizes the "bolts" in flight.
I attached thin rubber bands to at least avoid the return to senders - this works fine. But there is still the issue of the tumbling bolts. About half of them do that. It must have something to do with the rotation - no problems at all if I turn by hand and push the bands up one at a time.
If all else fails, I will convert this baby to manual repeating action.
But it does look cool!
I quickly encountered a huge problem: Return to senders and misfirings!
Those returners are dangerous. I mean seriously dangerous. One hit the door right next to my head... two inches to the right and I'd be in trouble now.
I don't really know what is going on - what I found out is that it works as long as you turn really slow. The fast spinning action of the battery drill is probably too much, destabilizes the "bolts" in flight.
I attached thin rubber bands to at least avoid the return to senders - this works fine. But there is still the issue of the tumbling bolts. About half of them do that. It must have something to do with the rotation - no problems at all if I turn by hand and push the bands up one at a time.
If all else fails, I will convert this baby to manual repeating action.
But it does look cool!
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