# 890 fps possible with a slingshot??



## torsten (Feb 9, 2010)

Hello,

Did some tests with very fast bands and 7,5 mm steelballs again: first under normal conditions - chrony shooting and can penetration. And then speed tests with heated bands. The numbers with heated bands are ALL far about 700 fps??!!
I took a bottle with cooked water to heat up the bands a few minutes before every shot. And then this numbers? Are there any experiences with chrony tests and heated bands. I think, these heated numbers are errors.
But ALL shots with non-heated bands were ok - all around 140 m/s; 460 fps! That`s strange - errors only with heated bands?! To fast for a chrony?
And: the water fast cooled down during the tests - the speed also decreased. The time between the first and the last shot was around 45 minutes.
I used 3 band sets - not more than 5 shots with every set :-(
And still no lengthwise tearing!

After the speed test I did some shots with this stuff on cans: a shot through 2 cans was no problem with this speed and ammo.
At the end of the video you see a little accident ( fortunately without injuries!!).

Here is the vid:






Regards
Torsten


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## joseph_curwen (Feb 8, 2010)

ENORME!!!!

I am fascinated by the capacity of these latex bands!

Thank you a lot for sharing with us


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## ZDP-189 (Mar 14, 2010)

It looks to be the real deal. I don't doubt the numbers. Extreme tapered, butterfly, very thin, heated flatbands and small light pellets should make for fast shooting. You are our resident speed demon.

I'd add that I'm not sure they'd make good commercial bands seeing as the reliability is low and danger factor high, but I guess you're not making them to mass-produce, eh?

BTW, get some glasses if you're doing these experiments! The Chrony could do with some polycarbonate shields too.


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## JoergS (Dec 17, 2009)

Torsten, I have done several tests with heated bands and also I have discussed the issue at length with my brother (who happens to be a top notch physicist).

My tests also show that the speed increase from heated rubber is immense. It is not so high on heavy bands and heavy ammo, but even then it is measurable. ARB has confirmed it with Thera Tube Silver on a braced frame.

I am thinking about a slingshot that heats the rubber, actually mentioned this a couple of month ago here. Currently I am evaluating the possibilities, always involving copper tubes around the rubber in uncocked condition (gas blow torch that heats copper tubes, "thermos" frame that uses hot water, battery powered heat wire).

Should be interesting.

My brother also explained to me why it works. Rubber takes all its energy from heat. You can feel the heat when you touch a drawn out band near the pouch with your upper lip. It looses the heat (actually cools down) when you release. That is also the reason for the tiring effect if you leave the bands stretched for too long.

We all know that hot, humid days are ideal for record breaking. The humidity transfers the heat in the air faster onto the bands, that is why humidity helps.

Pre-heated bands are clearly the key to more speed = more power.

Jörg


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## JoergS (Dec 17, 2009)

Torsten, regarding the lengthwise tearing, I have experienced that effect several times. But the length of the tear was never all the way from the fork to the pouch, it ran about 8 cm from the pouch towards the for only.

On slower bands, the tears have been much shorter.


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## torsten (Feb 9, 2010)

ZDP-189 said:


> It looks to be the real deal. I don't doubt the numbers. Extreme tapered, butterfly, very thin, heated flatbands and small light pellets should make for fast shooting. You are our resident speed demon.
> 
> I'd add that I'm not sure they'd make good commercial bands seeing as the reliability is low and danger factor high, but I guess you're not making them to mass-produce, eh?
> 
> BTW, get some glasses if you're doing these experiments! The Chrony could do with some polycarbonate shields too.


I do mass-produce such bands - for myself









Btw, yes, they are completely useless for daily use!
A fast and accurate hunting set with 330 - 340 fps and min. 100 shots - that would be a way to go. But certainly not for everyone...


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## Gandolphin (Jun 28, 2010)

I live in Israel, all i need is to use black thera bands and put them in the sun


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## torsten (Feb 9, 2010)

JoergS said:


> Torsten, regarding the lengthwise tearing, I have experienced that effect several times. But the length of the tear was never all the way from the fork to the pouch, it ran about 8 cm from the pouch towards the for only.
> 
> On slower bands, the tears have been much shorter.


I often have heard (Tex, you) of the problem of lengthwise tearing bands at high speed shots. Did hundreds of shots, hot and cold shots, but it never happened to me. Maybe because I stop shooting when I realize the first little tear in the band?
Or my bands are to long? I cut them all between 26 and 28 cm (long!).
I don`t know, what `ve been making wrong?


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## dgui (Jan 12, 2010)

Pocket warmers for bands to increase speed.


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## joseph_curwen (Feb 8, 2010)

dgui said:


> Pocket warmers for bands to increase speed.


had the same thougt


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## Tex-Shooter (Dec 17, 2009)

I had one tear almost full length that cut my plastic safety glasses enough to feel with your finger nail. I am glad it hit my glasses and not me. I have noticed the difference in speed from a cold day to a hot day is quite a lot. -- Tex


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## torsten (Feb 9, 2010)

How long were your bands? Was it thick latex? I used Thin black thera band.
And did you use extended forks?


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## whipcrackdeadbunny (May 22, 2010)

Almost, incredible.


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## NaturalFork (Jan 21, 2010)

Awesome video!


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## torsten (Feb 9, 2010)

dgui said:


> Pocket warmers for bands to increase speed.










Good at cold weather - for your fingers!
The bands fast cool down - they are warm only a few seconds. After one shot the temperature is almost normal. Plus: the bands tear faster!

I think, pre heated bands are ok for such tests. For usual shooting,hm...


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## Bugar (Dec 24, 2009)

Great Video, and super interesting, And I really enjoy the fact that the shooting was not in a controlled or labratory enviorment= Great Stuff, thanks for sharing=Absolutely GREAT


















torsten said:


> Pocket warmers for bands to increase speed.










Good at cold weather - for your fingers!
The bands fast cool down - they are warm only a few seconds. After one shot the temperature is almost normal. Plus: the bands tear faster!

I think, pre heated bands are ok for such tests. For usual shooting,hm...
[/quote]


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## Sam (Jul 5, 2010)

torsten said:


> It looks to be the real deal. I don't doubt the numbers. Extreme tapered, butterfly, very thin, heated flatbands and small light pellets should make for fast shooting. You are our resident speed demon.
> 
> I'd add that I'm not sure they'd make good commercial bands seeing as the reliability is low and danger factor high, but I guess you're not making them to mass-produce, eh?
> 
> BTW, get some glasses if you're doing these experiments! The Chrony could do with some polycarbonate shields too.


I do mass-produce such bands - for myself









Btw, yes, they are completely useless for daily use!
A fast and accurate hunting set with 330 - 340 fps and min. 100 shots - that would be a way to go. But certainly not for everyone...
[/quote]

If you could make that I'd buy it for my hunting! A high velocity low mass set-up is much safer if you think about it, as velocity depletes, whereas mas doesn't; if you miss your chosen target your bullet will have lost a lot of its original energy by the time it hits whatever it does... It's the principal air rifles and even shotguns (w/ birdshot,) operate on...


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## Sam (Jul 5, 2010)

Regarding heating up bands: couldn't we just make a portable heater that we warm our slingshot with every 5 or 10 minutes? It could even be a liquid with excellent heat retaining properties couldn't it?









*This has made me so excited! *


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## torsten (Feb 9, 2010)

Just found an interesting forum-comment to this topic from the other us-sling forum:

"Torsten,

Very impressive results! Regarding the possibility of 890 FPS being an error, it is possible to make some calculations (with assumptions about your slingshot and arms) to determine whether this is within reason, or likely to be a chronograph error.

First, the projectile: A 7.5-mm sphere has a calculated volume of approximately 0.01348 cubic inches. Assuming the material is steel, having a specific gravity of 7.86, the weight is about 0.0038148 pounds. At 890 feet per second, the kinetic energy of this projectile is 46.92 foot-pounds (63.6 joules).

The system must obey conservation of energy. After release and contraction, the kinetic energy of the projectile, bands, and pouch cannot exceed the work done during your draw. For a very light projectile such as this, slingshot efficiency will seldom exceed 50%. This is because the leather pouch and rearmost portion of the bands weigh about the same as the projectile, and they are accelerated to the same velocity, therefore they receive around half of the kinetic energy. This is why you get higher projectile energy from a heavy ball shot in the exact same slingshot. The rubber also never returns all of the energy input to it during draw, some is actually lost to heating.

If we assume 50% efficiency (you can vary this number to see the effect on the calculations), the energy input during draw will need to be 2 x 46.92 = 93.84 foot-pounds.

Energy input during draw is easily calculated as force times distance. Here I must make some assumptions about the length of your arms and the bands you are using. Again, you can modify the numbers based on what you know, but I believe my guess will not be too far off. I will assume that your arm span at full draw is six feet, and that the relaxed band/slingshot assembly is 18 inches long. Draw force then begins at zero when your hands are 1.5 feet apart, and tops out at the max draw weight when your hands are 6 feet apart. If we assume a linear relationship between draw and force, then the energy input to the bands is [(6 - 1.5)/2]*Fmax, which is 2.25*Fmax. Fmax is the force at full draw.

So for this case, if your full-draw force (Fmax) was 93.84/2.25 = 41.7 pounds, then the 890 FPS result at least does not seem to contradict physics.

If your max draw weight was more like 25 pounds, then the stored energy could be only 56.25 foot-lbs, projectile energy 28.125 foot-lbs, and projectile velocity would probably have to be less than 700 FPS (since velocity decreases as the square root of energy).

Further decreasing draw weight to 15 pounds moves the probable "best" velocity down to the 500 FPS range.

Can you measure your max draw weight when using these band sets?

Of course, the "real" results can be tweaked a little by using different assumptions for efficiency, draw length, and force/elongation profile (which can be fairly nonlinear, particularly for tapered bands)."

My english is a bit poor so I do not understand everything. But : my draw was max. 9 kg (or less) - then 890 fps are not possible.

The 142 m/s; 465 fps with non heated bands are much more realistic.


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## Sam (Jul 5, 2010)

torsten said:


> Just found an interesting forum-comment to this topic from the other us-sling forum:
> 
> "Torsten,
> 
> ...


I do not agree with his calculations, do the same using SI units (the units scientists use,) and you can clearly see that the slingshot is producing less energy than you are putting in it, thus obeying the laws of physics, afterall it'sproducing 63.9 Joules of Energy, afteral 1kg = 9.81N.

_*PS:* Chronographs can measure projectiles travelling at speeds of >1000m/s with 99.5% accuracy, so the increased speed definitely isn't going to cause an error. _


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## JoergS (Dec 17, 2009)

Torsten, may I suggest that in the future you post the link only, not the full text. Copyright issues are tightening on the web and for sure we don't want any hassle.

Links are always OK, but text and pics taken from other web pages should not be posted here without the prior permission of the owner of the copyright.

Jörg


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## torsten (Feb 9, 2010)

Oh, no problem, Jörg.

What do you (your brother?) think about the comment?
Any german translations for me?

Thanks 
Torsten


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## Sam (Jul 5, 2010)

JoergS said:


> Torsten, may I suggest that in the future you post the link only, not the full text. Copyright issues are tightening on the web and for sure we don't want any hassle.
> 
> Links are always OK, but text and pics taken from other web pages should not be posted here without the prior permission of the owner of the copyright.
> 
> Jörg


Yeah, it's crazy....







I thought you were allowed to as long as you blatantly displayed it as a quote though...


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## ARB (Dec 31, 2009)

That is astonishing! I hope it is true and not a chrony error. Somebody should try to replicate it, it would not be difficult to put a small slingshot in an oven at various temperatures and chrony it immediately. I have done rough experiments withTheraband in the oven at approx 100 deg C, it didn't seem to harm the rubber.


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## torsten (Feb 9, 2010)

ARB said:


> That is astonishing! I hope it is true and not a chrony error. Somebody should try to replicate it, it would not be difficult to put a small slingshot in an oven at various temperatures and chrony it immediately. I have done rough experiments withTheraband in the oven at approx 100 deg C, it didn't seem to harm the rubber.


Ha, another crazy guy with hot latex

What are your results? 
What was the difference between cold and hot bands?


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## dgui (Jan 12, 2010)

Torsten, there is only one thing that troubles me about all of this. You are not protecting your eyes.


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## boyntonstu (Jul 16, 2010)

Not to rain on your parade but today I saw very high reading using my Pro-Chrono.

I saw 895 fps and 1050 fps.

These were obviously way off the true value.

I have no idea of what is happening.

Some shots are OK, while others make me think of sending the unit back for a checkup.

BTW The true readings were between 218 and 236 fps.

I hope that your high chrony readings were correct.


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## Flatband (Dec 18, 2009)

Very high speeds with a slingshot are possible and a few of us have achieved high numbers on very hot days with thin latex. Heating rubber for a little while (and not too hot of a temperature) will not really hurt it. As far as numbers in the 900's and 1000's, well I did many tests and had some numbers that were going along pretty consistently and then all of a sudden I would get a big spike in speed-obviuosly wrong. Then I would clear the Chrony and start again. Sometimes I would get these big spikes in speed . I never could figure it out. It is amazing Torsten that you haven't torn a band lengthwise with those speeds. I'm also surprised at how much life you're getting from these thin bands-COOL! I guess I have to get the Chrony going again and see for myself. I'm a little skeptical of speeds of 800-1000 fps with a slingshot. I always thought 500 could be done but double that? I HAVE to try this again! Flatband


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## JoergS (Dec 17, 2009)

Well, I have NOT discussed Spiderman's point with my brother yet. Will certainly have a chat with him soon.

But I have to say that the 140 m/s using cold bands is very much what I have measured many times.

And it is absolutely certain that heating does make the shot faster, simply because the bands will be more efficient and less energy is lost. A proven, undisputed fact.

Question is how much faster. The 271 m/s seem a bit unrealistic indeed. That would mean the speed almost doubled. I believe a speed increase of about 30% is realistic, for extremely heated bands (the max. heat you should not exceed is about 80 degrees centigrade).

What could have gone wrong? Well, first off how far have you been away from the Chrony? The bands on a butterfly OTP slingshots can fly very far, and if they cross the sensors of the Chrony the tests will be disturbed. In most cases an error message is what you get, but sometimes crazy results can come out.

Also I noticed you do not use the diffusors. In bright sunlight, you have to use them in order to avoid false results. This info is taken from the Chrony manual, here:

http://www.shootingchrony.com/english_QS_F1M1.htm

I suggest you repeat the tests with the diffusors installed, or during a cloudy day. Make sure you are at least 2,5 meters away from the chrony.

And use glasses. I can assure you from my own, painful experiences that a torn band hitting your unprotected eye is not exactly fun. The fact that it did not happen to you so far only increases your chances that it will happen on the very next shot.

Last not least protect the chrony. I have two chrony carcasses that did not survive a hit to the front. RIP.

Jörg


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## ZDP-189 (Mar 14, 2010)

I've hit my Chrony too many times to count. Thanks to Jörg's warning, I put 1/4" Lexan over the front and back sensors and it still works fine.


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## torsten (Feb 9, 2010)

OK, thanks guys for our helpfull comments!!!
Very nice to have such a great www. - community!!

Well, these high numbers seemed to be very unrealistic. After reading our interesting posts - also in other forums - i`m now pretty sure about that these results are errors!!
Btw., all these tests of the last weeks were VERY interesting for me!!

I like more the tests under normal conditions - they are more usefull for my "daily" shooting.
I have now bands with around 120 - 125 m/s (410 fps) and not sooo high draw weight that last 20 - 40 shots. Shooting with this speed is amazing for me!! 40 shots at this speed is also ok FOR ME! 2 -3 bandsets - and I will have VERY much fun for two hours of long range shooting!
Also nice bands with around 105 m/s (340 - 350 fps) for heavier ammo and around 100 - 150 shots, with low draw weight too and accurate.

That is OK so far!

Going higher than 140 m/s (460 fps) increases the draw weight a lot! Not helpfull for me `cause accuracy decreases - also the number of shots.

The influence of temperature in point of speed and durability of bands is remarkable! Also I have to be VERY carefull (only SHARP rollcutter etc.) while making those fast bands: little mistakes will dramatically decrease the number of shots!

I did all my tests with butterfly bands. I shoot this style most of my "slingshot-life" and now don`t come along with the regular style.
Low draw weight, high speed and accuracy is what i like and easier to reach for me with butterfly (means NOT, regular style is a worse style!!!).

At least:
I think nobody needs such fast bands.

I LIKE THEM - UP TO 125 M/S! They make sense for me at long range and - a bit slower - for hunting (of course not in germany)! And for FUN!!!

For common target shooting this would be the wrong stuff!
Here I use much slower and much more durable bands.

Regards
Torsten


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## Darb (Sep 14, 2010)

> What could have gone wrong? Well, first off how far have you been away from the Chrony? The bands on a butterfly OTP slingshots can fly very far, and if they cross the sensors of the Chrony the tests will be disturbed. In most cases an error message is what you get, but sometimes crazy results can come out.


The speed readings for the 5 shots in the video were: 141 & 141 for the unheated bands at the first location, and then 272 & 233 & 217 for the heated bands at the wilderness location. Some comments, in no particular order:

* First, the most obvious question - are you absolutely certain that these numbers aren't actually *FPS* rather than the M/S you're indicating ? If so, the numbers would make complete sense.
* Per JoergS' comment above, I did spot an "Errr2" code just before the last shot, so clearly you were getting some errors. Also, you were kneeling closer to the sensor in the heated bands sequence than you were in the first two with unheated bands, so perhaps JoergS was right about being too close possibly affecting the readings.
* Interesting how the last 3 speeds show a clearly decreasing pattern, possibly as the bands cool off.

The phenomena of bands being more efficient when warmed seems to make theoretical sense, but I'm decidedly skeptical of an improvement of more than say 50-60%.


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## Darb (Sep 14, 2010)

Torsten: how were the bands heated, and to what temperature ?


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## torsten (Feb 9, 2010)

Darb said:


> > What could have gone wrong? Well, first off how far have you been away from the Chrony? The bands on a butterfly OTP slingshots can fly very far, and if they cross the sensors of the Chrony the tests will be disturbed. In most cases an error message is what you get, but sometimes crazy results can come out.
> 
> 
> The speed readings for the 5 shots in the video were: 141 & 141 for the unheated bands at the first location, and then 272 & 233 & 217 for the heated bands at the wilderness location. Some comments, in no particular order:
> ...


Darb,

it is a m/s chrony!
Errr2 or Errr1 is to be seen, if the shot passes not straight over the chrony and misses the front or back sensor - no datas are to be seen, only "errr1 or 2". But iwas kneeling far enough away from the chrony.

I pre heated the bands on a bottle filled with hot water - maybe at the beginning at 80 °C and around 50 - 60 °C at the last shot.
I think the high m/s datas are crazy results. 100% more speed then the cold bands means 4 times more energy! Only from heating the bands? I have strong doubts!!

Regards
Torsten


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## ARB (Dec 31, 2009)

I would really encourage Torsten or somebody else who can shoot butterfly style to try to repeat these tests. If anybody can get close to those speeds using heated bands it is very big news for slingshooting.

As regards possible errors, I think the fact that Torsten got three super fast readings means that a random chrony error is unlikely. Also, I would have thought that the bands flying forward over the chrony and recoiling after the shot would result in an Err1 or Err2 but perhaps I'm wrong. Even if the chrony is reading the speed of the rubber rather than the speed of the ball, 890 FPS from the rubber would be very significant.

The readings definitely are not in FPS - there is no doubt that Torsten's setup shoots much faster than 280 FPS.

Other possibilities - if an F1 chrony is not fully "open" the speed can be overstated as the sensors are closer together than the chrony's brain thinks they are. But that still would not explain such dramatic speeds.

PS I achieved 325-330 FPS using a 0.451 cal lead ball (~138 grains) using heated gold theraband and a big starship. I believe Torsten's butterfly draw length is longer, the rubber he is using is thinner and faster, the projectile he is using is 7.5 mm steel (~30 grains) 890 FPS seems unlikely but I'm keeping an open mind.


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## torsten (Feb 9, 2010)

Well, so let`s get new results from new tests!

But I`m out of the game now- the weather for new speed records is over here in good old Germany!! Six months of lousy weather are coming...








Indoor shooting would be possible - but it is not so much fun!

Regards
Torsten


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## fish (Dec 24, 2009)

some how i missed this vid,wow! bloody amazing!


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## Darb (Sep 14, 2010)

If I wanted to buy a speed measuring device, what make and model do people recommend ?


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## Tex-Shooter (Dec 17, 2009)

Chrony F1 -- Tex


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## Darb (Sep 14, 2010)

Thanks, Tex.

http://shootingchron...ucts_SCMMCM.htm

Looks like Item 5 (F-1 Archery Variant) is the one for me ... if I ever opt to buy one.


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## Tex-Shooter (Dec 17, 2009)

Why? The F1 does just fine at slow speeds! -- Tex


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## Tex-Shooter (Dec 17, 2009)

Putting the Chrony aside for the moment lets think about another test for an 890 FPS speed. If a shot leaves a slingshot at 890 FPS, there should be a sonic boom or crack like that of a whip both from the shot and also from the bands. -- Tex


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## Henry the Hermit (Jun 2, 2010)

Tex-Shooter said:


> Putting the Chrony aside for the moment lets think about another test for an 890 FPS speed. If a shot leaves a slingshot at 890 FPS, there should be a sonic boom or crack like that of a whip both from the shot and also from the bands. -- Tex


Not quite, Tex. The speed of sound is about 1100 fps.


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## Tex-Shooter (Dec 17, 2009)

Oh yea, I got my miles per hour and feet per second mixed up for tha speed of sound. -- Tex


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## A+ Slingshots (Jan 22, 2010)

[quote name='torsten' date='23 September 2010 - 11:36 PM' timestamp='1285310201' post='27466'Torsten[/quote]

Very interesting indeed!!!! The properties of rubber still amazes me!!! Great vid. Torsten








BTW I like you bike too!!! Do you use it to get around everywhere or just to slingshot sites??? My wife and I have been avid bicyclers in the past! Is that a second seat I see on the top tube???


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## torsten (Feb 9, 2010)

A+ Slingshots said:


> Very interesting indeed!!!! The properties of rubber still amazes me!!! Great vid. Torsten
> 
> 
> 
> ...


When we lived in the city, I used my bikes for nearly all my ways - job, kids, shopping, culture, etc.... Now living in the country side, we have to take the car for all these things








But mountainbiking is still my main hobby. A few years ago downhill and dirtjump, now with a bit less adrenaline... "only" for body an soul.
The second seat...I`m often the taxi for my youngest childs







They like the strong wind...


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