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Testing Chinese Tubes


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#21 pgandy

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Posted 26 December 2011 - 03:01 PM

Many thanks Henry. I had been considering a Dankung. The primary reason for quick change thinking it ideal for the tube bands I’ve been planning on. I had suspicions about the comfort of that frame with high draw forces and you proved me correct. I now plan to order the bands and pouches in within the next couple of weeks and use on my PSs. I even have a new PS1 on order as they fit my hand to a T distributing draw forces well.

#22 AZshooter

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Posted 26 December 2011 - 04:12 PM

Mr. Stubby looks like a good solution for the hand cramp problem...Having some chinese frames myself I find it comfoting to build a wood handle onto the metal frame...Dankung sells them already fit with wood handle, but I prefer to make my own....You might try Fimo molded handles, but I guess most craftsmen here have experimented with Fimo clay....

#23 Henry the Hermit

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Posted 26 December 2011 - 04:59 PM

It has been a most interesting day. With the same bandset I used in the last reported results, I asked my 34 year old 6'4" son to try a few shots. I'll let the pictures tell the story.

henry3.jpg

chrony-300+-02.jpg

I am properly humbled.

#24 Performance Catapults

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Posted 26 December 2011 - 05:05 PM

Looks like he means business.

I was always intrigued by the dankungs as well. I didn't like always having to re-position the frame in my hand. Hence the SPS.

#25 Rayshot

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Posted 26 December 2011 - 06:00 PM

It has been a most interesting day. With the same bandset I used in the last reported results, I asked my 34 year old 6'4" son to try a few shots. I'll let the pictures tell the story.

henry3.jpg

chrony-300+-02.jpg

I am properly humbled.


309 and 364 are with a .177 if I am following your thread, yes?

#26 Henry the Hermit

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Posted 26 December 2011 - 06:10 PM

It has been a most interesting day. With the same bandset I used in the last reported results, I asked my 34 year old 6'4" son to try a few shots. I'll let the pictures tell the story.

henry3.jpg

chrony-300+-02.jpg

I am properly humbled.


309 and 364 are with a .177 if I am following your thread, yes?


No, 309 was with .25 steel as was my son's 364. .177 BBs were a flop. I have now achieved 300+ with .304 lead. More later.

#27 Henry the Hermit

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Posted 28 December 2011 - 10:42 AM

I am now as close to the optimum configuration for maximum speed with light ammo as I consider needful and practical. I won't go into all the details of how I arrived at these dimensions, suffice to say I tied a lot of bandsets and made a lot of measurements. With each new set, I would make the looped portion longer and then trim the single portion a half inch at a time until the bands could not be stretched (by me) any further. Almost every set started at an overall length of 8 inches and maxed out at 5 1/2 to 6 inches. Each time I increased the looped portion length, once I had cut back to about 6 1/2 inches, I got velocity increases. There is, of course, a limit.

I have learned that double sets (like those supplied by Dankung may have lower velocity for light ammo than these, which I will call “tapered” for lack of a better term. I settled on a 4:3 ratio of doubled to single with a total length of 7 inches (17.8 cm). There is more velocity available than I achieved with this configuration, but at the expense of short band and pouch life.

If you want to duplicate these, cut the tubes to 11.5 inches (29.2 cm) Loop one end back so that there are 3 1/2 inches of single tube left (loop 8 inches). Clamp the looped end very near the end with a hemostat. I use a bench vise to hold the hemostat. Pre-stretch the loop and tie as close to the hemostat as possible. I use white waxed string and a constrictor knot. Whatever you use make sure the tie is very tight or you may experience slippage. I tie the pouch by feeding 1/2 inch (1.27 cm) through the pouch hole, clamping with the hemostat, lots of pre-stretch and a constrictor knot as close to the pouch as I can. I will post a tutorial on making these soon.

If you use a short draw, you can adjust the dimensions. Just maintain the 4:3 ratio. I'm drawing about 38 inches to get the velocities below. That is 5.4 stretch factor. I thought my draw was 34 inches, but it seems I've gained some arm strength in the last 6 months.

Today's measurements: All listed are 5 shot averages.

.25 cal (6.35mm) steel – 308.7 fps (94.1 ms) 3.44 lbs/ft (4.66 joules)
.304 (7.7mm) lead – 283.3 fps (86.3 ms) 7.43 lbs/ft (10.07 joules)
.375 (9.5mm) steel – 273.7 fps (83.4 ms) * 9.12 lbs/ft (12.36 joules)
.363 (9.2mm) lead – 242 fps (73.76 ms) * 9.25 lbs/ft (12.51 joules)
.429 (10.9mm) lead – 205.5 fps (62.6 ms) 10.98 lbs/ft (14.89 joules)

* Note: the .375 steel weighs 51 grains and the .363 lead weighs 71, which accounts for the smaller lead ball having a lower velocity than the steel.

As we have seen in previous posts, there is more speed to be had from 1842 rubber, but I'm hoping this configuration will be a happy compromise between raw speed and band life. I hope some of you folks will build your own tapered 1842 bands and report your results.

This is not the end of my experiments, but bandsets built to these dimensions will give you a significant increase in velocity over the standard Dankung double sets for ammo lighter than 3/8 lead. I will continue to post results as I get improvements.

Here's Mr. Stubby with the bands installed.

stubby-1842.jpg

Edited by Henry in Panama, 28 December 2011 - 11:40 AM.


#28 Charles

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Posted 28 December 2011 - 11:22 AM

Very nice results, Henry. And well presented too! I am anxiously awaiting my 1842 tubes to give this a try.

Cheers ....... Charles

#29 Henry the Hermit

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Posted 29 December 2011 - 08:57 AM

I made a brief side trip into the raw power side of tapered 1842. I wanted to see if I could get 200+ fps with .495 lead balls. I got 222 fps (67.7 ms), 19.96 lbs/ft (26.69 joules). I have no doubt there is more power there, but I'm not strong enough to pull past 32 inches without shaking enough to endanger my Chrony. I'll have my son take a crack at it later. This is Mr. Stubby with the double tapered set.

double-tapered.jpg

#30 M.J

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Posted 29 December 2011 - 10:30 AM

Oh yeah!!
I find it hard to beat the simplicity, power and long life of a regular set of looped 1842s but I'll be giving this a shot just to see what it's like.
"Mr. Stubby" looks to be a very fine slingshot as well :thumbsup:

Edited by M_J, 29 December 2011 - 10:32 AM.


#31 pgandy

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Posted 29 December 2011 - 11:26 AM

Thanks for the information Henry. You have taken much work out of me finding a good starting point. My 1842 is out there somewhere and hopefully will arrive in a few more weeks. My goal is to increase band life while equalling, if not to exceed present power, which while acceptable is not all that great. Your findings make me optimistic. Hopefully this will save money as it costs much to import the Theraband. Advise when your new video is out.

#32 Henry the Hermit

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Posted 29 December 2011 - 01:33 PM

Oh yeah!!
I find it hard to beat the simplicity, power and long life of a regular set of looped 1842s but I'll be giving this a shot just to see what it's like.
"Mr. Stubby" looks to be a very fine slingshot as well :thumbsup:


Mr. Stubby is a fine shooter. It doesn't show in the pictures, but there is an offset natural palm swell which fits my hand perfectly.

@pgandy - I haven't done any videos, but I will produce a picture tutorial on tying these bands in the next few days.

Back to the double set, I knew the power was there, and my son just proved it. His fastest shot with the double bands and .495 (12.6mm) lead ball was 259.1 fps (79.97 ms) for 26.8 lbs/ft (36.36 joules). He also took a shot at a fallen green coconut. The ball penetrated all the way through the husk and shell and we could hear it rattle inside when we shook it.

His one shot with a 3/8 lead ball was 327.9 fps, but some seriously painful band slap stopped that line of exploration.

My next phase of the project is to count shots with the tapered set to see if they last.

Edited by Henry in Panama, 29 December 2011 - 03:28 PM.
Correct mistake


#33 nutthrower

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Posted 29 December 2011 - 04:59 PM

say guy's can you give me some info on what you use to aquire you weight of ammo, and your weight in draw. I've been ask to do some of these and can't, also maybe I can also bother you in how to put in photos .... I've got some real uglys to show ya

#34 Charles

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Posted 29 December 2011 - 07:45 PM

say guy's can you give me some info on what you use to aquire you weight of ammo, and your weight in draw. I've been ask to do some of these and can't, also maybe I can also bother you in how to put in photos .... I've got some real uglys to show ya


To measure the weight of you ammo, I have not found anything better than this, and it is cheap:

http://www.leevalley...352&cat=2,40725

To measure draw weight, I use this gizmo:

http://www.leevalley...733,40734,67613

Again, it is cheap and accurate ... just hook the pouch and pull to your draw length ... presto!

Cheers ...... Charles

#35 bullseyeben!

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Posted 29 December 2011 - 07:56 PM

Well 330fps with 3/8 lead! Does that out- joule my 338fps with 9mm? Bloody close id say lol, great research mate.., Ben

#36 Performance Catapults

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Posted 29 December 2011 - 08:00 PM

I made a brief side trip into the raw power side of tapered 1842. I wanted to see if I could get 200+ fps with .495 lead balls. I got 222 fps (67.7 ms), 19.96 lbs/ft (26.69 joules). I have no doubt there is more power there, but I'm not strong enough to pull past 32 inches without shaking enough to endanger my Chrony. I'll have my son take a crack at it later. This is Mr. Stubby with the double tapered set.

double-tapered.jpg


Glad you didn't use my pouch with this setup. I doubt it is strong enough to use safely, as it is not intended to be. It is great to see the exporation you are doing with the tubes however. ;)

#37 Hrawk

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Posted 29 December 2011 - 08:02 PM

Ben, if you want a cheap set of scales that will do grams and grains, check this one, $12.99 with free delivery in AU.

LINK

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#38 nutthrower

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Posted 29 December 2011 - 08:25 PM

excellent guys, will look into both items - thanks

#39 bullseyeben!

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Posted 29 December 2011 - 08:29 PM

Sweet, cheers mate! Have to get me one of them too...

#40 nutthrower

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Posted 29 December 2011 - 09:14 PM

Henry, I got to tell ya "Mr. Stubby" is just plain coooooool looking - I think at some point I read here how you installed those eye-bolts if ya wouldn't mind going through it again it would be appreciated.......thanks

had I knew how efficient those 1842 bands were I would have ordered those too, thanks for your info




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