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Discussion Starter · #1 ·
I built a homemade wide fork version of my favorite commercial slingshot, and I was curious to see whether wider forks were faster. So, I did some testing using (nearly) identical setups, and here are my results. I don't mean to start a flame war. I was just curious, and I'm just posting data for others to see and use.

In my data, the wide-fork version was about 4.1% faster than the narrow-fork version. The wide-fork version also gave substantially more consistent speeds. I did my best to make the setups consistent, but:

  • the wide-fork version had ever-so-slightly narrower and ever-so-slightly longer bands (actual measurements used), and
  • the narrow-fork version had an ever-so-slightly wider leather pouch versus the microfiber pouch on the narrow-fork version (okay, so sue me... I was too lazy to cut off one of the pouches to re-tie)

Here are the data (all metric):

Product Rectangle Font Parallel Symmetry


Created: 01/10/19 13:53
Description: PP Taurus 01
Notes 1:
Notes 2:
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 0.00
Temp: 15 °C
BP: 1022.00 inHg
Altitude: 0.00
# MPS joules PF
9 76 0.00 0.00
8 77 0.00 0.00
7 78 0.00 0.00
6 79 0.00 0.00
5 80 0.00 0.00
4 78 0.00 0.00
3 79 0.00 0.00
2 77 0.00 0.00
1 75 0.00 0.00
Average: 77.7 MPS
SD: 1.6 MPS
Min: 75 MPS
Max: 80 MPS
Spread: 4.9 MPS
Shot/sec: 0.1
True MV: 78 MPS
Group Size (in): 0.00

Created: 01/10/19 13:55
Description: Homemade Taurus 01
Notes 1:
Notes 2:
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 0.00
Temp: 15 °C
BP: 1022.00 inHg
Altitude: 0.00
# MPS joules PF
10 81 0.00 0.00
9 81 0.00 0.00
8 81 0.00 0.00
7 82 0.00 0.00
6 81 0.00 0.00
5 80 0.00 0.00
4 81 0.00 0.00
3 81 0.00 0.00
2 81 0.00 0.00
1 80 0.00 0.00
Average: 80.9 MPS
SD: 0.6 MPS
Min: 80 MPS
Max: 82 MPS
Spread: 2.1 MPS
Shot/sec: 0.2
True MV: 81 MPS
Group Size (in): 0.00
 

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With all respect the data you start from are so different that you have to have the differences in all measured parameters and it is difficult to assign those differences to the width of the forks only.

For example, each of your data:

pouch measures (therefore weight);

width at forks;

width at pouch;

active band length

will give you reasons for different velocity, energy etc.).

The test like this was made by Bill Hays in his video I suggest that you watch this and make your conclusions about the design of the experiment. But in short, wider forks - all other parameters being equal - give more ft/s because wider angled bands when stretched to the same point along the central line are stretched, in fact, more than the bands of the narrower forks. And more stretch of the same length of the bands again give more power, more velocity etc.- my interpretataion

It seems that the advantage of the wider forks is also that the stretch starts sooner than with narrow forks (question of slack).

But I have an impression that people who shoot PFS couldn't care less..

cheers,

jazz
 

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Discussion Starter · #4 ·
So, based on Jazz's comments (he's right, my testing conditions are far from laboratory quality :unsure: ), I switched bands between the two slingshots to balance out any differences between the band sets.

The results were very interesting. The wider forks are slower by 3.1% with the switched band sets (roughly the same amount as they were faster before), which means that the difference in speeds is very likely due to the differences in drag and weight of the pouch. I'm shooting very light ammo, so a 1g difference in pouch weight doubles my ammo weight.

The data are actually pretty consistent. Based on this, my conclusion is that the difference in speed between wide and narrow forks, if any, is small enough not to be noticeable. The wider forks do seem to help with speed consistency by a small amount.

Created: 01/10/19 16:14
Description: PP Taurus 01
Notes 1:
Notes 2:
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 0.00
Temp: 16 °C
BP: 1020.00 inHg
Altitude: 0.00
# MPS joules PF
10 80 0.00 0.00
9 78 0.00 0.00
8 81 0.00 0.00
7 80 0.00 0.00
6 78 0.00 0.00
5 79 0.00 0.00
4 78 0.00 0.00
3 79 0.00 0.00
2 79 0.00 0.00
1 80 0.00 0.00
Average: 79.2 MPS
SD: 1.0 MPS
Min: 78 MPS
Max: 81 MPS
Spread: 3.0 MPS
Shot/sec: 0.1
True MV: 79 MPS
Group Size (in): 0.00

Created: 01/10/19 16:13
Description: Homemade Taurus 01
Notes 1:
Notes 2:
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 0.00
Temp: N/A °C
BP: N/A inHg
Altitude: 0.00
# MPS joules PF
10 76 0.00 0.00
9 77 0.00 0.00
8 76 0.00 0.00
7 77 0.00 0.00
6 77 0.00 0.00
5 77 0.00 0.00
4 76 0.00 0.00
3 78 0.00 0.00
2 77 0.00 0.00
1 77 0.00 0.00
Average: 76.8 MPS
SD: 0.7 MPS
Min: 76 MPS
Max: 78 MPS
Spread: 2.1 MPS
Shot/sec: 0.2
True MV: 77 MPS
Group Size (in): 0.00
 

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I'm not a scientist or anything .. but what might have happened is being that the wider forks cause you to stretch the bands more than the narrow? .. maybe cut the bands a bit longer with the wider forks so that they are being stretched the same and re test just my 2 cents

Sent from my SM-G955U using Tapatalk
 

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I would like to see a pic of the homemade wide fork Taurus. How wide are the forks? Which version... OTT or TTF? How do you like the wider forks compared to the original PP version?
Here are a couple of photos. It's not finished, yet, but functional. I still need to finish shaping it, sanding it, and put a finish on it. It's made out of a wood called Ipe or Iron Wood, which is so dense that it doesn't float. I had some left over from another project.

I made it for two reasons:

  • I made it mostly because I have to aim far below the target with narrow forks using my preferred anchor point (thumbnail at the corner of my mouth), and wanted a wider fork to bring the fork closer to the target without having to change my anchor point. With the narrow forks, I have to move my anchor point up next to my nose to do that, which is less comfortable and causes my thumb to recoil against my cheekbone when I release. I love the Pocket Predator Taurus design because it's incredibly comfortable. It spreads out the force against my entire hand, versus other designs where I'm bracing with my thumb or against sharp corners (pinch grip).
  • I also made it to test out the idea that bands would last longer with a wider fork (the theory being that the bands smack less against the forks on release). I like to keep my shots above 75 m/s (about 250 ft/s) because I find slower speeds lack a certain "punch" that I like. However, I go through a bandset just about every day, which is annoying. I haven't used them long enough to determine whether there's any difference in band life, though.

As far as differences, I still like them both. The original PP Taurus is smaller, lighter, and more agile. The homemade Taurus is bigger and heftier by design, so I can fit more of my hand on it. The forks are 12cm (4.72 inches) wide on the outside versus 8cm(3.15 inches) for the original PP Taurus. Because of the extra mass, there's less recoil/movement at the slingshot after release, which I like. Honestly, they're both great and just as accurate as one another (as far as I can tell with my mediocre shooting skills...). They just have a different heft and feel to them.

When it's all finished, I'll post it in the homemade slingshots category.
 

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