[JASling]

Hello everyone I hope you all are doing well I have a question and I hope some of you can help (Hopefully it hasn't been ask before)
So I have been wanting to get my hands in a Chronograph but that money spend there could go to another sling or so.
Anyhow my question is if it's possible to get an average speed by shooting a certain object or thing.

For Example.
I am using "X" band thickness with "Y" taper shooting 9.5 steel or any other steel. If I where to shoot the bottom of some tuna cans( for example) and the still ball just dents it I could guess that the fps of the steel was (ex) 170- 200fps depending on the dent left in the object as well.
After this I change my taper or same taper different band thickness... Etc.. but this time it goes through now I can guess that the steel is moving at or faster than 250fps.

So I guess the simple question is:

What thing can I shoot that when the steel goes through that object or several of them stacked together I know that my steel is flying at or faster than 250fps.
(Or how deep it goes into clay but clay can have different density and such)

This way if I where to change bands or ammo as long as it makes it through that object/s I know that it's flying at or faster than 250fps no matter the combination.

I remember seen somewhere that if your ammo went through a tuna can bottom from 30ft you have a good hunting set-up. So this made me think of this question.

Thanks for looking and helping out in advance.

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[KawKan]

I don't think anyone has done the basic chrony work that we could use as a basis for estimates like this. If they have, I haven't seen it. Results would vary with ammunition, of course.

My google search indicates there are such estimates for BBs and Airsoft. I suppose slingshooters could use those for that ammo.

 

[wll]

All I can say is you can guess but you will probably be wrong, i have done it and been way off. The only way to get a real reading is with a chrono sorry to say .. ya they are a PITA, and the sun has to be right and, and, and ... but if you really want to know, a chrono is a must.

Just last week I was sure i was getting 250-275fps with hopes it might be close to 300fps with the tubes I was using ... not a chance, 225fps to 239sps was it with the looped tubes I was using, the flats didn't really look that much faster but they were going 257fps. I thought the single 1745's were not that great but they were shooting 225fps ... right up there with the looped 2040's and looped 3050's.

Get yourself a chrono and be sure if it is that important to you ... take it "for what its worth" * ;- )

* For what it's Worth - Buffalo Springfield - Released Dec. 23rd 1966, Written by Stephen Stills

wll

 

[flipgun]

As for the money? You can trade for or build a lot better slingshot than you can a chrony.

 

[thelzer101]

Dan Ambrosius does a youtube video clocking the fps on few different kinds of bands.

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[treefork]

Here is a way to do it with a phone application.

https://slingshotforum.com/topic/21084-smartphone-chrony-setup-tutorial/

 

[Valery]

Вот способ сделать это с помощью телефонного приложения.

https://slingshotforum.com/topic/21084-smartphone-chrony-setup-tutorial/

Приложение для телефона не обеспечивает точных измерений, но оно подходит для сравнения скорости различных ремней и боеприпасов. Если вам нужны точные данные, вы не можете обойтись без хронографа.

 

[mattwalt]

yeah was going to say what Treefork said - think there is an app. If I remember it uses sound...

 

[Griffo]

All I can say is you can guess but you will probably be wrong, i have done it and been way off. The only way to get a real reading is with a chrono sorry to say .. ya they are a PITA, and the sun has to be right and, and, and ... but if you really want to know, a chrono is a must.

^ This.

Estimating actual velocity by assessment of impact damage has too many variables ever to be properly accurate. The phone app could be worth investigating.

Another route is to look at recorded results made with a chronograph and match the details of those results to the specifics of what you are shooting. This should get you ballpark.

Like these test results: https://slingshotforum.com/topic/118528-test-results-sumeike-precise-sobong%E2%80%A6part-1-sumeike/

 

[Sean Khan]

Yes, there is an app. It's called "Chrono Connect".... However it has a poor rating on the Google Store.

If it doesn't work for you... like crashes all over the place... here is a post I made a long time ago in Joerg's forum.... I'll copy/paste. Might be helpful.

My method does the same thing but without the app. I believe it's more accurate.

---------------------------------

1. Take any mobile phone with sound editing app.

2. Go to known distance away from target. Like 6 feet in my case.

3. Set mobile to record sound.

4. Fire.

5. stop recording.

6. You will see THIS:

That spike is the sound of impact. But is it all that is?

Zoom in. Keep zooming in until you see THIS:

You will see two events. One is the sound of projectile hitting the target. And before that is the sound of the bands snapping.

Write down the time when the second event just starts from background noise.

And then write down the time when the bands have snapped and released your ammo. I assume it is at the highest point of the first event.

Now then.... 22.33 seconds minus 22.30 seconds is 0.03 seconds.
6 feet divided by 0.03 equals 200.

My projectile was traveling at 200 feet per second.

Slingshot, target and marble used in speed measuring exercise.

Of course, you can use your computer to analyze the sound wave (eg, "Audacity" for Linux)... don't have to do it all on the phone...

Who needs a Chronograph/Speed-Gun? Spend the money on wife/wives instead.

 

[jazz]

Among very good ideas given to you above, you can also use my Slingshot Setup Designer and input Ammo Weight, Rubber Weight, Pouch Weight, Draw Length, Stretch Ratio and Draw Power and the program will tell you Exit Velocity and Exit Energy immediately. If you also click on Shoot! button you will get Velocity and Energy at the moment of impact.

The results are very close to reality (always a bit higher than the reality), I tested it.

I must admit that the program in this version does not work with tapered bands or tubes.

Normally you will assume that a taper will propel the ammo faster, however, this is true only for certain combinations of taper and ammo weight, namely, higher taper, say, 25 mm to 5 mm will propel very light ammo faster than the straight cut of 15 mm, but the same taper of 25 to 5 mm will propel heavier ammo less, or slower, than the straight cut. I made limited test of this and I do not have much reliable data yet as to share with you except this indicative relation.

You can download the program at: https://slingshotsetupdesigner.com/

cheers,

jazz

 

[Griffo]

Of course, you can use your computer to analyze the sound wave (eg, "Audacity" for Linux)... don't have to do it all on the phone...

Who needs a Chronograph/Speed-Gun? Spend the money on wife/wives instead.

I'm going to try this. Measuring using sound not spending money on the wife I mean. ^_^

 

[Pebble Shooter]

By definition, if a set of (probably significantly tapered) bands or tubes enables the steel ammo of a given size to perforate a sheet metal-based tin can (everyone here knows "Heinz baked beans" tins, right? Yes, that sort of tin can), it's probably fair to assume that it will be quite effective on small game at reasonable ranges. Of course, ballistic issues such as hardness, shape, and weight of the projectile play a major role, not to mention the physical limitations of the retraction speed of rubber after the pouch is released - even with extreme tapering, which entails longevity problems of flat bands in particular.

With slingshots, more projectile weight, tapering, and increased draw length is the only way to boost power output. Ultimately, it's a case of finding a happy compromise between an acceptable draw weight and the type of ammo performance needed for a specific objective.

Several years ago, I used Thera-Band blue cut to 29 cm length and tapered from 26 mm at the forks to 16 mm at the pouch, double layered, for 12 mm steel ammo to perforate 10 mm particle board at 2 to 3 meters distance: clean holes like Swiss cheese! A 10 mm lead ball shot with this zippy rubber would doubtlessly yield some interesting results on game, but hunting with slingshots is not allowed in the land of Heidi - so I don't know.

Bottom line in my opinion: keep it simple, and opt for a 40% taper for bands suitable for a semi-butterfly shooting style to maximize projectile velocity. Thinner rubber is usually more zippy than thicker rubber. One needs to experiment.

 

[robbo]

i have found a few charts over the years one bloke.did flats; tubes ,flat straight cuts 20mm theraband from memory and tapered 20x18 from memory 6mm steel up to 9.5 steel and led i think it was for a 30inch draw and a 32inch draw there was red dub dub and looped 1845.not counting the recent precise vs sobong.vs sumieke test there have been at least 2 other big lots of test data posted by very keen shooters over the years .WHAT I WOULD LIKE TO NO IS THE SPEED DIFFERENCE BETWEEN A 26 INCH DRAW AND A 30 INCH DRAW ALL OTHER THINGS EQUAL OF COURSE BAND LENGTH AJUSTED SO STRETCH FACTOR IS THE SAME BILL HAYES HAS LIMITED INFO ON .THIS.AN EXAMPLE WOULD BE 20X10 THERABAND GOLD 140MM STRETCHED TO 700MM 8MM STEEL. 200MM STRETCHED TO 1000MM 8MM STEEL.