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| boyntonstu |
 Posted: 07/11/2010 13:04 PM Post subject: Theraband: Does 1 + 1 = 2? |
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Joerg stated that thinner bands are faster than thicker bands.
If you want to power of a gold band can you parallel black bands to equal the power of gold and would it be as fast or faster?
Which Theraband is most cost effective with respect to price and power; blue, green, silver, gold? |
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| JoergS |
| Posted: 07/11/2010 14:35 PM Post subject: |
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Yes, you can equal out the bands. The thinnest bands will be the fastest (although the differences become smaller between the thin types).
Draw weight comes down to the weight of the bands. Equal weights mean equal draw weight. But the retraction is faster with the thinner bands.
Regarding Thera Band, gold gives you the most weight for the buck, so if you want to max out the energy (using heavy balls), then gold is clearly a good idea.
Thorsten is right with what he says, I concur with his statements 100%. But he likes light draw weights and is happy with small ammo. I want as much power as possible, so we are just in different disciplines. A .50 AE Desert Eagle would do poorly in olympic .22 tournaments. |
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| boyntonstu |
| Posted: 07/11/2010 14:44 PM Post subject: |
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| JoergS wrote: | Yes, you can equal out the bands. The thinnest bands will be the fastest (although the differences become smaller between the thin types).
Draw weight comes down to the weight of the bands. Equal weights mean equal draw weight. But the retraction is faster with the thinner bands.
Regarding Thera Band, gold gives you the most weight for the buck, so if you want to max out the energy (using heavy balls), then gold is clearly a good idea.
Thorsten is right with what he says, I concur with his statements 100%. But he likes light draw weights and is happy with small ammo. I want as much power as possible, so we are just in different disciplines. A .50 AE Desert Eagle would do poorly in olympic .22 tournaments. |
That is most helpful.
For 5-6 gram projectiles gold may too strong.
Black, silver, or blue for 91 cm total draw?
I like to shoot glass marbles.
AND:
What is the best method of up and over 180* rubber U-Turn?
It seems to me that a small diameter rod ~1/4" with a small diameter sleeve would be a good method to draw a rubber from beneath and over with little loss.
Has anyone a better way of building a low loss U-turn? |
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| JoergS |
| Posted: 07/11/2010 22:38 PM Post subject: |
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Stu, I worked with rollers a lot. If you don't use bearings, then your rollers should be thick, like 4 cm diameter.
Otherwise, the friction will make the rotation stuttery. This means that towards the end of the pull, the force on the rollers will be so high that it jams and needs much force to move.
But for a rifle, the gain in length is minimal. You can maybe safe 10 or 15 cm in length. But the price for this is high.
- There is chafing, so the band life will be short. Thinner rubber will tear the earliest.
- Loading will be problematic as the band will pass the rollers after the shot, and you have to get it back over them. You can add rods to stop it from doing that, but then the rubber will tear even earlier.
My advice is to design the crossbow in a way that the rubber flies freely and on its return does not come into contact with anything sharp or edgy, preferrably with nothing at all. Rubber is vulnerable.
For such a lightweight ball, use Thera Band Blue or Black. You won't need much of it.
But you may want to consider tapering. Maybe this thread from the slingshotforum will be helpful:
http://slingshotforum.com/topic/1216-tests-with-extreme-tapering/
I got the 4 gram .38" steel ball to over 100 m/s, with a draw weight a preteen boy can pull.
But the band life is short.
Jörg |
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| Gun Freak |
| Posted: 07/12/2010 9:58 AM Post subject: |
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The Anti Hybrid
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So for shooting little glass marbles with a standard slingshot, blue or black bands would be the best? Black is currently unavailible, so is blue ok for this application? Thanks.
Also, some lengths say "mils"... what is that? |
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| JoergS |
| Posted: 07/12/2010 15:19 PM Post subject: |
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| Use blue, cut it 7 cm ( fork) x 4 cm (pouch), 23 cm long. |
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| boyntonstu |
| Posted: 07/13/2010 5:03 AM Post subject: |
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| JoergS wrote: | | Use blue, cut it 7 cm ( fork) x 4 cm (pouch), 23 cm long. |
Is there a difference in performance between a band that is 1" at the fork and 1/2" at the pouch if:
1> The band is uniformly tapered on 2 sides?
2? The band is tapered on only one side? |
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| JoergS |
| Posted: 07/13/2010 18:06 PM Post subject: |
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| No noticeable difference, Stu. I always taper 1 side only. |
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| boyntonstu |
| Posted: 07/13/2010 18:33 PM Post subject: |
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| JoergS wrote: | | No noticeable difference, Stu. I always taper 1 side only. |
Thanks, I had to ask the expert.
Is there anything that you haven't tried?
I am going to try a U-Turn band system to emulate the 160 cm butterfly draw on my rifle.
BTW I believe that I have found a very, very simple roller.
PEX tubing that just fits a 1/4" rod.
It will rotate with just the weight of Thera-Band tubing drawn across it.
Imagine the band fixed just wide of the rifle trigger, going forward to the roller/fork, and back to the trigger.
I will be able to draw a 91 cm band to 182 cm.
I am hoping for 100+ M/sec for a 5.2 gm marble. |
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| JoergS |
| Posted: 07/13/2010 20:30 PM Post subject: |
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Stu, be careful. This means you will have to stretch the bands to fit over the rollers, which is not easy. Also, when I tried a setup like that, the ball did not shoot straight but went wild, ricochetting in a very scary way. Wear protective clothing and a full helmet for the tests.
I ended up sawing the rollers off and used a straight fork. |
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| JoergS |
| Posted: 07/17/2010 13:07 PM Post subject: |
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So many people begged me to do a how-to for the Sling-X-Bow.
Of course people don't have welding gear and lathes, so a tutorial can't require such equipment.
I thought about this for a long time, as there were numerous issues to be solved. But then I finalized my blueprints and got to work.
I used wood and off-the-shelf screws only, plus common household tools.
Making it took six hours, because of the constant filming and also because welding stuff together is a lot quicker than drilling holes and fixing screws...
I used Stu's ratchet idea for the cocking, but made my own ratchet out of a length of wood. It is easy, you just push the frame to the front until it hits the stopper, and then it swings into the notch.
I made the frame, the lock base plate, the lock arms and the trigger plate out of multiplex (most of it I found in the trash of my favorite DIY superstore).
This is real solid, shooting hunter bands is not a problem, lots of reserve.
The video will follow tomorrow, here are some pics for now!
Jörg |
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| JoergS |
| Posted: 07/17/2010 13:08 PM Post subject: |
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Lieutenant Colonel
Joined: 04 Aug 2009
Posts: 435
1516.80 Spud Bux
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So many people begged me to do a how-to for the Sling-X-Bow.
Of course people don't have welding gear and lathes, so a tutorial can't require such equipment.
I thought about this for a long time, as there were numerous issues to be solved. But then I finalized my blueprints and got to work.
I used wood and off-the-shelf screws only, plus common household tools.
Making it took six hours, because of the constant filming and also because welding stuff together is a lot quicker than drilling holes and fixing screws...
I used Stu's ratchet idea for the cocking, but made my own ratchet out of a length of wood. It is easy, you just push the frame to the front until it hits the stopper, and then it swings into the notch.
I made the frame, the lock base plate, the lock arms and the trigger plate out of multiplex (most of it I found in the trash of my favorite DIY superstore).
This is real solid, shooting hunter bands is not a problem, lots of reserve.
The video will follow tomorrow, here are some pics for now!
Jörg |
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| Gun Freak |
| Posted: 07/17/2010 13:16 PM Post subject: |
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The Anti Hybrid
Joined: 25 Jan 2010
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| Sweet, simple and doable for most people... I like it! |
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| boyntonstu |
| Posted: 07/17/2010 13:35 PM Post subject: |
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Brigadier General
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I love it too.
Wunderbar!
Please test the steel and the wood designs; chrony and pull weights.
It would make a great video.
BTW The Boynton-Banger does not use a spring. |
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| JoergS |
| Posted: 07/18/2010 8:10 AM Post subject: |
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