# Do rollers on a slingshot rifle increase speed?



## mannitu78 (Sep 4, 2019)

hello people,

im about to build a slingshot rifle using my latex-training rubber and a slinghot-release ive ordered from amazon. Now ive seen that some slingshotguns use rolls for an extendet drawlengh/lengh of rubber. Now i cant figuere out in my head if these do have actual benefits. They are not moving but are fixed, therefore they dont actually translate in a higher drawspeed like on a compound crossbow. Also the distance over the steelball will be accelerated does not change. Its just doubling up the rubber lengh. Anybody can give an -educated- guess what the result will be? thx.


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## mannitu78 (Sep 4, 2019)

this is a regular slingshot gun youre probably all familiar with...just wantet to make clear its meant to shoot steelballs, not arrows. I just showed the 1st picture to show how the rolls are attached. Ill be using the same release device like this:


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## MakoPat (Mar 12, 2018)

I wish I could help...but I am definitely interested in what you discover.

There are some engineer types on here, but I have not saw from them in a while.

I wish the best of luck. I wonder if the rollers just extend band life or something to the effect.


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## Hobbit With A Slingshot (Mar 14, 2017)

My understanding is that the rollers will not increase the power, they just allow you to keep the slingshot rifle more compact. So the second slingshot rifle you showed could be made half as long if one used rollers. But that's just what I remember from watching Joerg Sprave's videos.


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## Pebble Shooter (Mar 29, 2014)

The key problem with rubber is its limited retraction speed when elongation related tension is released: to my knowledge, this lies somewhere around the 70 m.p.s (229 fps) mark, albeit that an optimized length and tapering will increase this quite significantly. Rubber stores energy in the form of heat, which is released as the bands (or tubes) retract: rubber left in a state of elongation for longer periods will cool down, which results in a lower projectile velocity.

Retraction speed is highest just after the release of the pouch, but decreases rapidly as the rubber returns to its normal state from a state of elongation. Adding rollers makes it possible to reduce the required length of a slingshot rifle, but this comes with the drawback of internal rotational friction, which can be minimized with ball bearings inside the rollers. Either way, the rollers will only have a very minimal effect on the retraction speed of the rubber.

All in all, I do not see any real added advantage to adding rollers (pulleys) in the hope of increasing projectile velocity, as a slingshot rifle does not have any powerful leverage mechanisms, such as those seen on compound bows, where the pulleys increase the effect of the bow arms leverage.

There is a US company, "Shoottech", that created the so-called "AR 480 Mark 2", which is essentially a crossbow specially designed to shoot larger steel ball bearings at very high velocities: it does not use rubber, though. See a video of this interesting contraption here:


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## Henry the Hermit (Jun 2, 2010)

I doubt there is any advantage to using rollers. They add complexity, weight, failure points, and friction and do not reduce the length of the sling rifle. Bear in mind that to stretch rubber to 500%+ the sling rifle must be at least 500% longer than the rubber.

*I think I may have over stretched my brain in thinking this. Of course, it reduces the required length of the frame, but I feel the disadvantages outweigh any advantages.


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## Ubamajuba (Jun 16, 2019)

I have dived in to this for the same reason, what do rollers offer. This is what i found:

1)With rollers you can make the steel ball accelerate longer, all the way to the fork, if the bands are streched out between the rollers in a relaxed state.

2) If the same condittion apply it will help with opening the pouch and minimize the risk of RTS.

Joerg made a slingshot with rollers. That gave more active band length for the same draw as with a normal slinghost. I think it reduced handslap too?






/Uba


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## mannitu78 (Sep 4, 2019)

to bad i dont have a chrony. I ll find another way to measure the impact though. Im still waiting for parts from china and it will take at least 2 more weeks. It will be about 35-40kg of draw weight...dont even know if thats too much...i only wanna shoot 8mm balls, not into shooting this huge balls.


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## Sachem (Dec 23, 2015)

Pebble Shooter said:


> The key problem with rubber is its limited retraction speed when elongation related tension is released: to my knowledge, this lies somewhere around the 70 m.p.s (229 fps) mark, albeit that an optimized length and tapering will increase this quite significantly. Rubber stores energy in the form of heat, which is released as the bands (or tubes) retract: rubber left in a state of elongation for longer periods will cool down, which results in a lower projectile velocity.
> 
> Retraction speed is highest just after the release of the pouch, but decreases rapidly as the rubber returns to its normal state from a state of elongation. Adding rollers makes it possible to reduce the required length of a slingshot rifle, but this comes with the drawback of internal rotational friction, which can be minimized with ball bearings inside the rollers. Either way, the rollers will only have a very minimal effect on the retraction speed of the rubber.
> 
> ...


Actually, someone announced this year: four 1842 tubes project 10 mm steel ball at 111 m/s (364 FPS). If we project small steel ball with flat bands, we can get much higher speed than this.

Rubber is a particular elastic material which doesn't follow Hooke's law, and "rubber left in a state of elongation for longer periods will cool down, which results in a lower projectile velocity." So any slingshot rifles have lower energy efficiency but more stability. Also they can work with stronger rubber sets because we needn't hold them with high power by ourselves after elongating the rubber.


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## mike160304 (Aug 10, 2018)

Interesting thread. I have learnt that, with slingshot rifles:

1. Low-friction, rotating rollers enable a slingshot rifle or starship to be shorter for the same performance.

2. The longer release is delayed, the more power is lost through rubber cooling. So to achieve consistency, draw+release time should be consistent, through practice.

Re (1), Joerg Sprave also made a non-rifle pocket slingshot with rollers, with most of the rubber inside the frame.

Re (2), this applies, of course, to any slingshot, but delays might be more frequent with rifle slingshots because of complexity.

Thank you all.


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## Lonewolf14779 (May 20, 2013)

Hi all its been some time since I been here but looking at slingshot rifles and this caught my eye and I also was this is something a came across

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I know this is long, real long but this is what it looks like


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