[Konrad]

Greeting to all at slingshotforum,

I have a dilemma and I would like to see if anyone has any answers.

My slingshot rifle has a draw length of 700mm (27.5inches) active band length of 140mm (5.5inches). The bands are tappered 50mm at the fork to 20mm at the pouch. The factory bands are 1mm.

The factory bands shoot 8mm steel at 117.5m/s (385fps) 8mm lead at 110.8 m/s (363.51fps) 1mm bands.

Theraband gold single's at the same tapper and length get 97m/s (318fps) 8mm lead (0.65mm thick)

Theraband gold double bands at the same tapper and length get 104m/s (341fps) (0.65x2=1.3mm thick)

I spoke to the guy at Catty shack hunter (Wayne) I think his name is Wayne and here is a copy of the conversation:

(in the comments section)

Does anyone know why my short draw length with 1mm or 1.3mm thick bands is shooting 8mm faster than a single band. The collective expertice of slingshotforum's members would be very much appreciated.

Here are some pics of the rifle on a previous post, scroll down please. https://slingshotforum.com/topic/123738-questions-about-getting-max-perfomance-on-the-flymars-a-hunting-slingshot-rifle-with-12mm-lead/

Salutations to all at slingshotforum. Paul.K

 

[mattwalt]

Sounds like you're using a heck load of rubber...

I suspect - but could be totally wrong ... Is they you're way overpowered for the setup. The system has to move the weight of the rubber itself - as well as the pouch and projectile (and some energy is lost in friction etc.)

So what I think may be happening as you're overpowered is that the weight of the extra rubber is in fact 'balancing out' the extra energy...

The simple test would be to halve the rubber of the singles and see what the velocities are with that setup. See if its in fact faster, or not.

 

[ghost0311/8541]

It's faster

 

[Griffo]

I think you've already found your sweet spot (or close to it) and your results are as expected.

The thinner Theraband single (0.65mm versus 1mm) will store less energy hence lower velocity with your weight of ammo.

The thicker Theraband double ((0.65mm x 2) versus 1mm) has greater overall mass hence lower acceleration and lower velocity with your weight of ammo.

The sweet spot as you've already discovered is at or around 1mm. Tweak closer around 1mm would be my suggestion.

There will be some hairy equations to quantify all of this but I don't know what they are. I enjoyed reading your results.

 

[Konrad]

10mm lead, Single bands 50mm-20mm tapper active band length of 140mm (5.5inches) Theraband Gold dropped off dramatically, 74m/s (242fps).

Thankyou very much to all who responded. This is such a great community. Dan Kung's SHESHOU guru 1mm has been ordered and is on the way.

Salutations to all. :thumbsup:

 

[Konrad]

I think you've already found your sweet spot (or close to it) and your results are as expected.

The thinner Theraband single (0.65mm versus 1mm) will store less energy hence lower velocity with your weight of ammo.

The thicker Theraband double ((0.65mm x 2) versus 1mm) has greater overall mass hence lower acceleration and lower velocity with your weight of ammo.

The sweet spot as you've already discovered is at or around 1mm. Tweak closer around 1mm would be my suggestion.

There will be some hairy equations to quantify all of this but I don't know what they are. I enjoyed reading your results.

Griffo, you where right. I tried GZK black 0.65mm, 25 to 10 tapper 600% elongation and got 89.9m/s. I tried 0.7mm (50 to 20 tapper) no name the factory sent me and got 106.8m/s. My last band set I made with 1mm Sheshou guru was 46 to 18mm tapper and got 112.8m/s all 8mm steel.

Cheers.