Slingshot Lab

It is obvious: Thicker rubber generates bigger force. If you use flat bands, it is easy to calculate the area of the flat band (see my drawing) area=width*thickness. (If the flat band is tapered, you have to use the width at the middle.) If you would like to pick an elastic tube, which has similar strength, you have to calculate the area of the cross section of the tube. Elementary school geometry. It is actually the difference of a large circle and a small circle. You can find the formula in the drawing. For example, if you pick 1632 tube size (1.6mm inner diameter, 3.2mm outer diameter) then the area of the cross section is cca 6 mm^2 (square mm). If you use 0.5mm thick flat band, then a 12mm wide one will be similarily strong. Similarily. This is a very complex issue in reality, it is easier to measure. You will need a fishers' digital scale for that. I think, all the serious slingshooters must have one.

 The most simple and convenient ball speed measuring method is the shooting chronograph. Until my instrument arrives, I use my smartphone to measure ball speed. Primary school physics: speed=distance/time. If we know, distance is 10 meters, then we just have to measure the time between the release and the target hit. It is possible with a smartphone: We take an audio record of the shot, then open the audio file in an audio editor, and read out the release time and the hit time. The difference of the two times is NOT the ball fly time! Think of this: If the phone is at you while shooting, the sound of the release arrives to the phone in negligible time. But the sound of the target hit has to fly 10 meters. The velocity of sound is 330 m/sec, and time=distance/speed, so it takes 10/330=0.03 sec (30 msec) for the sound to arrive at the phone. So, fly time=hit time-release time-30 msec. (If distance is 10 meters.) Now, we can calculate: ball speed=10 meters/fly time.  You can find...

  Precise is one of the market leading slingshot band manufacturers. In their website, at the product description they write: "5 to 6 times the super tensile strength, safe and stable." We can consider this, 500%...600% as the recommended maximal safe elongation range.  Tapered bands are wider at the fork end and narrower at the pouch end, so they are stronger at the fork end, weaker at the pouch end. When we pull the band, the elongation will be higher at the pouch end. How much is the TOTAL elongation, when the pouch end elongation is in the middle of the factory recommended range? Test description I cut a band from 0.6mm Precise elastic, 18/12mm taper. 180mm long. I fix its narrow end to the bench. I draw a thin line 1cm far from the fixing block, and another line at 16cm.  Then I pull the wide end until the pouch end elongation is 550%, and read the total elongation. Then I pull further the wide end, until the pouch end elongation is 600% (safety limit). Then I ...

Hi Fellow Slingshooters, I started slingshooting 1 year ago, and I have watched many videos, I have read many forum posts, etc. Many, many reviews, opinions, instructions, suggestions, recommendations, and so few data. I am an engineer of industrial measurements, so I miss those facts.  In this blog I will publish my simple and cheap, but technically correct tests, which - I hope - will help the slingshooting community to develop. My posts will be text based, not videos. Why? This is much easier, faster and cheaper to make. My lab equipment is very humble, but enables me to perform quite useful tests. In my tests I will use SI (metric) units. In the numbers I will use decimal points. My equipment list today: - an electronic fishing scale (0...20 kg, accuracy: +/- 2 gram) - a measuring tape (0...5 meter, Class I, max error on 1 meter is 0.5mm) - a digital caliper (0...170mm, accuracy: +/- 0.05mm)) Ordered equipment (arrives in January) - a shooting speedmeter (cronograph, 0...1000m/...