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The Slingshot Channel Thread

All non-spudgun related discussion goes here such as projects, theories, serious questions, etc. All "off-topic" posts (aka useless posting, determined by moderators) will be removed.
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Unread postAuthor: JoergS » Thu Jul 08, 2010 6:35 am

Well, simply because I just use a bit wider and shorter bands. This leads to a higher draw weight, but it is still very doable.

In other words, in order to achieve power, a longer "barrel" means a lower draw weight for the same projectile speed. It is quite logical, right?
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Unread postAuthor: boyntonstu » Thu Jul 08, 2010 8:08 am

JoergS wrote:Well, simply because I just use a bit wider and shorter bands. This leads to a higher draw weight, but it is still very doable.

In other words, in order to achieve power, a longer "barrel" means a lower draw weight for the same projectile speed. It is quite logical, right?


Your logic is perfect.

Why don't Theraband tubes perform as well as their bands?

My goal is 105 m/s (345 f/s) with a ball weighing 10 grams (55 Joule).

For a draw of 91 cm what band would you recommend?
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Unread postAuthor: JoergS » Thu Jul 08, 2010 8:23 am

Simply because the walls of the tubes are thicker. Thicker means more inner friction between the rubber molecules. Friction means a lesser efficiency.

Stu, I think you can achieve 55 Joules, but not with a 10 gram ball.

I have tested this extensively. Even if you use thin, extremely tapered bands and micro pouches, you won't ever see that kind of speed with 91 cm draw length and a 10 gram (14mm) ball.

I got to 105 m/s with a 9,5mm ball (4 grams), with Thera Band Gold, tapered from 9 cm (fork) to 1 cm (pouch). That band set shot .177 BBs at 140 m/s. But it breaks very quickly. 10 to 20 shots it is. Rubber does not like such a high retraction speed. That is why you should never dry fire a slingshot.

The way to see serious energy from a slingshot is high ammo weight.

Use .75 (19mm) lead BBs, those weigh 36 gramms. A band set that will propel them to 55 m/s is still manageable, use 12 cm x 8 cm x 23 cm Thera Band Gold per side. You may cut it into three or four stripes for a cleaner look. You will loose about 4 to 5 cm for the attachments, so effective band length will be about 18 cm. Just about right for a 91 cm draw.

Trust me on this, I have invested half a lifetime in these tests.
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Unread postAuthor: boyntonstu » Thu Jul 08, 2010 8:58 am

JoergS wrote:Simply because the walls of the tubes are thicker. Thicker means more inner friction between the rubber molecules. Friction means a lesser efficiency.

Stu, I think you can achieve 55 Joules, but not with a 10 gram ball.

I have tested this extensively. Even if you use thin, extremely tapered bands and micro pouches, you won't ever see that kind of speed with 91 cm draw length and a 10 gram (14mm) ball.

I got to 105 m/s with a 9,5mm ball (4 grams), with Thera Band Gold, tapered from 9 cm (fork) to 1 cm (pouch). That band set shot .177 BBs at 140 m/s. But it breaks very quickly. 10 to 20 shots it is. Rubber does not like such a high retraction speed. That is why you should never dry fire a slingshot.

The way to see serious energy from a slingshot is high ammo weight.

Use .75 (19mm) lead BBs, those weigh 36 gramms. A band set that will propel them to 55 m/s is still manageable, use 12 cm x 8 cm x 23 cm Thera Band Gold per side. You may cut it into three or four stripes for a cleaner look. You will loose about 4 to 5 cm for the attachments, so effective band length will be about 18 cm. Just about right for a 91 cm draw.

Trust me on this, I have invested half a lifetime in these tests.


I trust you, I do.

BTW I thought of a way to add velocity without using rollers, etc.

Put on your thinking cap.
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Unread postAuthor: boyntonstu » Fri Jul 09, 2010 8:58 pm

Choosing Theraband bands

Is it more cost effective to use multiple bands of black or silver to gain power than to buy the more expensive gold?

IOW Other than thickness and color are there any other differences?
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Unread postAuthor: Gun Freak » Sat Jul 10, 2010 2:45 pm

I'm making a crossbow soon, just thought I'd let y'all know :)
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Unread postAuthor: deathbyDWV » Sat Jul 10, 2010 5:10 pm

One that works like a real one with the power coming from the bow or with rubber as the power?
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Unread postAuthor: Gun Freak » Sat Jul 10, 2010 7:10 pm

Power from the bow, I'll probably use some sort of metal cable for the string and pvc shaped for the arms. Sorry, my terminology isn't that great :happy8:
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Unread postAuthor: deathbyDWV » Sat Jul 10, 2010 8:08 pm

Gun Freak wrote:Power from the bow, I'll probably use some sort of metal cable for the string and pvc shaped for the arms. Sorry, my terminology isn't that great :happy8:

Ah... Ok... Just be careful so the PVC doesn't shatter...
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Unread postAuthor: Gun Freak » Sat Jul 10, 2010 8:15 pm

Nah it won't, I'm cutting the pipe lengthways so its only half the pipe for the bow but I'm doing three layers, 1" to 3/4" to 1/2" welded together and bolted to the frame.
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Unread postAuthor: Heimo » Sat Jul 10, 2010 9:37 pm

Gun Freak wrote:Power from the bow, I'll probably use some sort of metal cable for the string and pvc shaped for the arms. Sorry, my terminology isn't that great :happy8:


I have build traditional bows in the past I know a few things about bow making

1 metal cable for a string :shock: not very wise besides it will be slow and dangerous proper bow strings are made from Dacron B50 or Kevlar.
Dacron B50 is not too expensive

2 PVC for bow limbs, again not the best choice, even if the PVC don't snap it will develop string follow (BAD)
you can use Osage orange, yew and ash wood to make bow limbs from and the limbs need to be backed with something like bamboo, carbon fiber or some special type of fiberglass that I have been unable to identify.

For detailed instruction on building a proper crossbow go Here
those plans might be old but I am fairly sure they should work
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C&P from another Forum. Joerg?

Unread postAuthor: boyntonstu » Sun Jul 11, 2010 6:54 am

If you take a band set of, for example, black thera with the same pull weight and tapering like a bandset from the golden band, the black set delivers more speed than the golden.

I can only speak about my sets. I use it for ammo sizes between 7, 6 and 12,7 mm. Here is the difference remarkable!! So I decided to stop using the golden since nearly one year. And I really don`t miss it!!

If you use havier ammo, for whatever reason, you need many layers from the thinner band. I think this causes friction between the single layers. Therefore the difference will be not so dramatically. I did very much testings with all colors of thera band - and black is my choice for the ammo i actually use.

You speak german? It `s a little bit heavy for me to explain all the facts that I would like to tell - I have learned more Russian then English in my schooltime...

Regards
Torsten
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Unread postAuthor: JoergS » Sun Jul 11, 2010 9:24 am

Baumstamm, a world reknown slingshot maker from Germany, recently sent me 2 of his handmade beauties. Amazing products! I was most excited about his wristbands, woven from colorful paracord. These bands are so sturdy that they actually hold the slingshot for you, you can relax your fingers and there is practically no shaking. I love them!

One is a multiplex boardcut, in black, and the other one is natural fork.

Here is the video:

http://www.youtube.com/watch?v=FnvlNt-LZfg

Regards

Jörg
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Unread postAuthor: JoergS » Sun Jul 11, 2010 11:21 am

The slingshot news magazine July 11 is online!

Here:

http://www.youtube.com/watch?v=xlziCb0glhE

Regards


Jörg
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Unread postAuthor: Gun Freak » Sun Jul 11, 2010 1:03 pm

Hey Jorg I want to make a slingshot and I want to know if these are the right bands, thanks.
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