# "Band Heater" Experimental Slingshot



## JoergS (Dec 17, 2009)

As announced, I have made a slingshot that heats its bands. I want to be able to break records even when it is NOT humid and hot outside! So there was no alternative.

I used water filled copper tubes, as water and copper have the highest available heat capacity.

The bands are put over the copper pipes that are filled with hot water, then the insulation is closed over the bands. They heat up in no time, about ten seconds from room temp to over 50 centigrade. I filled the tubes with hot, but not boiling water as I am not sure how much heat they tolerate.

The slingshot is ugly as heck, but not a bad shooter, it is a "W" after all. And the copper pipes work like a stabilizer.

I don't know about the speed increase as it is too dark now, but we shall see tomorrow!





































Jörg


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## Paul (Jun 15, 2010)

Please let us know how it responds.
Thanks for all of your freely shared ideas.
Paul


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## Flatband (Dec 18, 2009)

Plumbing comes to slingshots!!!! I love your enthusiasm Joerg! Heated bands, water storage in pipe-prongs,temperature gauges,gate valves,"THE PLUMBER" arrives!!! I got a kick out of this one Bud! Interested to see the speed increase because of the heat. COOL!! Flatband


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## Darb (Sep 14, 2010)

Proof positive that some people will do just about anything to get their balls into a hot sling.


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## huey224 (Apr 12, 2010)

you are right it is ugly! but if you can get high speeds!


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## Darb (Sep 14, 2010)

There's a joke in there somewhere about German engineering, but I'm too too much the gentle soul to crack it.


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## ARB (Dec 31, 2009)

You will definitely get some extra speed. But based on my own experiments it may be 10% or slightly less. I have found this with gold Theraband, silver Theratube and black Theratube. Would be interested to see what you would get with thinner blue, black or green Theraband. In any case I'm looking forward to the video!


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## Dayhiker (Mar 13, 2010)

This doesn't seem unwieldy and impractical to you? I don't get it.


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## NaturalFork (Jan 21, 2010)

AWESOME!


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## Darb (Sep 14, 2010)

Dayhiker said:


> This doesn't seem unwieldy and impractical to you? I don't get it.


Of course it's unweildy and impractical.

The point is to have a little good natured fun while also being innovative and busting new technological sod. The fact that it's ugly and impractical just makes it that much more fun, quirky, and impressive.

Surely as a young lad, your inner mad scientist clapped its hands with meglomaniacal glee the first time it saw the Van de Graaff Generators and Jacob's Ladders (aka 'high voltage travelling arcs') crackle to life in Frankenstein's lab ?

Mine did, and still is.


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## JoergS (Dec 17, 2009)

Of course it is impractical and unwieldy. But it is shootable, and it heats the bands.

It is an experimental slingshot, not a candidate for a beauty contest, tournament favorite, or preferred hunting weapon.

It is one more step towards the ultimate goal, THE STRONGEST SLINGSHOT MANKIND HAS EVER INVENTED.










Jörg


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## danny (Aug 24, 2010)

what weapon?


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## Dayhiker (Mar 13, 2010)

Well. I surely do love experimentation and I like looking at non-gun weaponry. But it seems to me that a battery-powered hand warmer could accomplish the same task. Am I wrong?


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## ZDP-189 (Mar 14, 2010)

JoergS said:


> Well. I surely do love experimentation and I like looking at non-gun weaponry. But it seems to me that a battery-powered hand warmer could accomplish the same task. Am I wrong?


You _are _wrong.

Because Jörg's probably our most experienced experimenter and I am sure he considered his options.

You would also be wrong to assume that every slingshot posted is a tutorial and a recommendation for others to follow. I am just grateful that this is one involved and complicated path that I will not feel the need to experiment with, as it seems Jörg has that well handled.


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## lucifer93 (May 4, 2010)

I love it Jörg but how will it get it through airport security. I am looking forward to seeing the videos on this new design


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## JoergS (Dec 17, 2009)

Well, a pocket warmer could NOT achieve the same result. The copper has to be so hot that you can't touch it with your bare hands, it takes a lot of energy to warm the rubber up to over 50 centigrade.

My tests are done, and ARB is right, with Thera Gold the difference is maybe 10%. But it was a warm day today, so even unheated the rubber had 19 degrees centigrade. On a cold winter day, the advantage would be more obvious.

Video will follow!

@Dan: A steam operated slingshot? Hmmm... that's an idea.









Jörg


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## Dayhiker (Mar 13, 2010)

Dayhiker said:


> Well. I surely do love experimentation and I like looking at non-gun weaponry. But it seems to me that a battery-powered hand warmer could accomplish the same task. Am I wrong?





ZDP-189 said:


> You _are _wrong.
> 
> Because Jörg's probably our most experienced experimenter and I am sure he considered his options.










That's not as scientific a statement as we are used to hearing from you, Dan.

But it's true that I seem to be missing the whole point of this line of experimentation. I think it is because I think of the slingshot as a practical field weapon, sort of like a pocketable bow and arrow. I mean the road this is on, _i.e_., forgetting about practicality, why don't you just go a step further and hook the valves up to some steam lines from a boiler, so you can keep the heat constant?


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## whipcrackdeadbunny (May 22, 2010)

I love the idea, I'm surprised you used water though ... I would've thought electricity would've been more user friendly, flick a switch, heat the handle, wrap the bands and warm your hands. That was the first one that popped to my mind.


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## JoergS (Dec 17, 2009)

Here is the video:


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## Darb (Sep 14, 2010)

I wonder if the difference is more significant for one of the other types of bands.


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## shot in the foot (Jan 3, 2010)

Just a thought how about gas filled curling tongs what women use to curl there hair, they would heat up quicker and you could just rap the bands round it, jeff


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## JoergS (Dec 17, 2009)

Well, I am just not sure about the heating thing in general. 10% more power is really not much, I am quite disappointed.


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## ZDP-189 (Mar 14, 2010)

whipcrackdeadbunny said:


> I love the idea, I'm surprised you used water though ... I would've thought electricity would've been more user friendly, flick a switch, heat the handle, wrap the bands and warm your hands. That was the first one that popped to my mind.


Electric requires a control curcuit. Chemical heaters are uncontrolled. Thermal capacity is tunable with the temperature of water used initially and remains relatively stable. It means he can test shoot and get consistent results without making a control circuit. But, yes, ultimately electric is better.


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## 919h (Aug 27, 2010)

_Excellent demonstration.
But I'm a little disappointed with the result. For 18 °to 55 ° c, we pass 59.61m/s to﻿ 65m / s, a gain of 9%, I thought the gap would be more important.
Maybe the result will be more impressive with temperatures below 0 ° c
Excellent work._


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## ARB (Dec 31, 2009)

Even though <10% increase in speed seems disappointing, obviously a small increase in speed can translate into a larger increase in KE. I did a test with heated Thera black tubes where the speed increased by 8% but the KE increased by 17%. I was using heavy balls and the KE increase was something like 63 ft/lbs to 74 ft/lbs.

Something that I noticed with the tubes was that if the rubber was heated beyond a certain point, the draw weight seemed to increae considerably. Also I got some very poor shots and flyers, it was like shooting with unevenly pulled or twisted bands. Then as the bands cooled a little they seemed to reach a "sweet spot" where they shot well and faster than normal.

Joerg if you have not done so already could you fit your slingshot with lighter, thinner bands and chrony it (no need for a video) using very light projectiles. I'm still intrigued by the speeds that torsten saw on his chrony, they were probably errors but it would be nice to confirm either way.


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## ZDP-189 (Mar 14, 2010)

Dayhiker said:


> That's not as scientific a statement as we are used to hearing from you, Dan.


Yeah, it's neither scientific, not particularly fair of me (and for that I apologise), but when doing things in big teams I have found it pays not to second guess the decisions of specialists except when I know from personal experience

Not only that, but I am deeply grateful to Jörg for sharing this with us. He could have just shot lots of record breaking speed shots on video and left us guessing how he did it. Thanks, Jörg!


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## ZDP-189 (Mar 14, 2010)

JoergS said:


> Well, I am just not sure about the heating thing in general. 10% more power is really not much, I am quite disappointed.


It's good news. It means I won't have to build one!


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## Darb (Sep 14, 2010)

That's one of the things I like about this place ... not only are there people who are unafraid to design and test new things in the name of improved understanding and performance, but they'll freely share the results with the community.


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## ZDP-189 (Mar 14, 2010)

And not afraid to admit when it didn't work out. Jörg, in the name of science, would you please use frozen or sub-freezing liquid (brine, alcohol or antifreeze) and do another run? That way we'll have three or four temperature data points that we can use to estimate a curve.

If you do I may take time to do some temperature hysteresis curves and we'll understand more about the process.


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## Darb (Sep 14, 2010)

The other thing I like about this place is that there are some erudite and talented professionals here. They, more than anything else, are the reason I check in as often as I do.


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## Darb (Sep 14, 2010)

JoergS: it's too bad the improvement is so modest. If the improvement were enough to warrant it, I think the next logical improvement to your clever design could be to integrate a digitially controlled copper "heatstick" to maintain the hot water temp. They sell such things in online homebrewing supply websites, for people who build recirculating infusion mash systems (RIMS), and they can readily be fitted with digitial thermostats. I built something similar years ago, when I was dabbling with all-grain beer brewing. With an ac/dc inverter, you could run it off a small portable ATV battery, or perhaps a lithium-ion power tool battery. That way, the only limit to the number of uses would bed the lifespan of the bands, and the charge in the battery.


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## Darb (Sep 14, 2010)

JoergS: Here's an example of a copper "heatstick" in a homebrewing RIMS system. The one in this video is 25A, and would obviously be too powerful for a slingshot ... I'm sure there are much smaller units available somewhere. Anyway, the relevent time indexes in the following video are from 1:30 to 3:00.


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## JoergS (Dec 17, 2009)

Of course I have to do some more tests with cold bands. 20 centigrade is much above the average temperature in Germany, the speed increase may be much higher if compared to 5 centigrade days.

A temperature curve is indeed needed, as it is a completely different task to keep bands at 20 degrees (body warmth would work fairly well) instead of 50 degrees.

I haven't invested in the thermometer gun just for one test! Still, I was disappointed. Maybe it was Torsten's test that pumped up my expectations.

Regarding electric heating systems, the power consumption would be huge. 10 Amps as a peak is realistic. This would require massive batt packs. I decided against this way for now.

Water and copper have a very high heat capacity, very effective heating systems indeed.

Jörg


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## 919h (Aug 27, 2010)

Torsten is sure that 2 bands are at the same temperature and uniform because the tramp in warm water, for Joerg it is less obvious.

But it's strange the differente result ??

Darb, I absolutly nothing understand, But It's Not You, It's me the raison ....


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## JoergS (Dec 17, 2009)

Well, I think Torten's results may have been errors. Torsten seems to think so as well.

But the water bath may have some effects, too! Who knows, wet bands may have different features than dry bands.

One thing is clear: Wet bands cool down waaayyy quicker, because of the evaporation cooling effect.

Jörg


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## whipcrackdeadbunny (May 22, 2010)

ZDP-189 said:


> I love the idea, I'm surprised you used water though ... I would've thought electricity would've been more user friendly, flick a switch, heat the handle, wrap the bands and warm your hands. That was the first one that popped to my mind.


Electric requires a control curcuit. Chemical heaters are uncontrolled. Thermal capacity is tunable with the temperature of water used initially and remains relatively stable. It means he can test shoot and get consistent results without making a control circuit. But, yes, ultimately electric is better.
[/quote]

Thanks Dan.


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## whipcrackdeadbunny (May 22, 2010)

JoergS said:


> Of course I have to do some more tests with cold bands. 20 centigrade is much above the average temperature in Germany, the speed increase may be much higher if compared to 5 centigrade days.
> 
> A temperature curve is indeed needed, as it is a completely different task to keep bands at 20 degrees (body warmth would work fairly well) instead of 50 degrees.
> 
> ...


Thank Joerg.


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## whipcrackdeadbunny (May 22, 2010)

After reading, it seems an even heating is most important, maybe this will optimize. Maybe the percentage will not make it viable though.


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## Bill Hays (Aug 9, 2010)

JoergS said:


> Regarding electric heating systems, the power consumption would be huge. 10 Amps as a peak is realistic. This would require massive batt packs. I decided against this way for now.
> 
> Water and copper have a very high heat capacity, very effective heating systems indeed.
> 
> Jörg


My thought on the subject is, heating coils would be an inefficient way to produce the heat you're after in a tube. Think heat created by friction instead. Two small motors spinning up long brushes against the insides of the copper will produce however much heat you need, and fairly quickly. A portable drill battery pack attached to the bottom of your slingshot... and even a drill's electronics would be enough to drive the unit.
Of course this isn't something I'm going to do... it really doesn't get cold enough here to mess with all of that!


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## Sam (Jul 5, 2010)

Darb said:


> I wonder if the difference is more significant for one of the other types of bands.


Yes I was also thinking along those lines, ATM the results are quite underwhelming, I believe the results will be significantly compounded by increasing the surface area of the bands, by using *Theraband Black,* and using an extended draw length. It would be very interesting to see what the butterfly draw can achieve with these optimisations in terms of velocity and kinetic energy!


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