# Heated rubber



## JoergS (Dec 17, 2009)

I am lying in the sun and let my mind come up with new slingshot ideas.

As you know, bands perform better when they are warm. That is why hot and humid days are record breaking times.

What if I design a frame where the bands are kept inside in relaxed condition, like in the "V", only for flat bands of course, and further, what if I attach heating devices to that frame so the bands would be heated to, say, 50 centigrade inside of the frame?

Little pocket warmers sold for hunters come to mind, based on burning carbide bits.

Even on a cold winter day, the bands would always be warm and fast.

What do you think? Ideas for heat sources?

Jörg


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## smitty (Dec 17, 2009)

Motorcycle heated grips ? 
Other kinds of heated gloves and clothing made for the motorcycle crowd might be adapted somehow. They plug in to the 12 volt system of the bike.


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## JoergS (Dec 17, 2009)

Hmmmm... carrying a 12 V acid filled battery might not be very practical.


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## smitty (Dec 17, 2009)

They also make 9 volt stuff like socks and gloves. Are you looking to go without a battery and try to use a chemical heat like the hand warmers you mentioned?


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## ZDP-189 (Mar 14, 2010)

Considering we don't know how hot to go, I'd start with an electric system than can be dialed up or down.


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## Norwegian Wood (Jan 12, 2010)

Hi, What if you use one of the soft thermobags that is ment for sixpacks, whith a couple of handwarmers in it, to keep your slingshot in. But offcourse you have to reheat the slingshot quite often.


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## boyntonstu (Jul 16, 2010)

Norwegian Wood said:


> Hi, What if you use one of the soft thermobags that is ment for sixpacks, whith a couple of handwarmers in it, to keep your slingshot in. But offcourse you have to reheat the slingshot quite often.


Keep it warm by holding it you armpit ~40* C?

Use 2 slingshots, one warming and one shooting.

Or: Exhale into a bag containing the slingshot. (is moisture a problem?)

Or: Place the rubber inside a tube and use a slider to create heat with friction.


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## JoergS (Dec 17, 2009)

I think Dan is right, we need to find out at what temperature we get the best performance. I am suspicious that this may be a lot warmer than we think, maybe between 60 and 80 centigrade or even higher.

I need to devise a test setup first.

If we know the optimum, then we need to come up with a practical solution.

Aah, a new variable in the eternal hunt for the most powerful slingshot!

Jörg


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## boyntonstu (Jul 16, 2010)

JoergS said:


> I think Dan is right, we need to find out at what temperature we get the best performance. I am suspicious that this may be a lot warmer than we think, maybe between 60 and 80 centigrade or even higher.
> 
> I need to devise a test setup first.
> 
> ...


Another factor is the release time.

Drawing creates heat.

Waiting releases heat and energy.

The draw/release should take no more than a few seconds to aim and fire.


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## Tex-Shooter (Dec 17, 2009)

Stretch a rubber band and hold it against your cheek. After it cools let it back to normal and hold it against your cheek again. I often thought that you could make a small cooling system using this principle. -- Tex


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## JoergS (Dec 17, 2009)

Bill, you are right, which clearly demonstrates how much of the stretch is converted (lost) into heat. This means that in hot condition the efficiency is much better.

My brother, who is a physicist and electronics genius, recommends simple heating wire that you can buy in many temperature types. These wires will stop consuming electricity once they reach a certain temp. Energy consumption is so low that a rechargeable set of four AAA NiMH cells will last hours.

I envision a W type slingshot with rectangular steel profiles as fork arms. The flat rubber and also the heating wire runs inside of the tubes. The cells are mounted on the bottom of the frame. The hollow fork arms would be insulated with plumbing material (foam tubes).

Rollers on top, of course.


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## ZDP-189 (Mar 14, 2010)

I never knew of any wire with a built in thermostat. Very clever.

You must name this the hotshot.


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## Brooklyn00003 (Feb 28, 2010)

Cant wait to see this concept.
I would add one thing probably worht tryig with aa batteryas first as they are very cheap ,but if the concept works you could upgrade the batteries to cr123 or 18650 depending on voltage needs and put them inside the rotating handle as I supose there will be one. this way dont need to use bulky 4 aa then one cant even see if its battery operated.


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## JoergS (Dec 17, 2009)

This kind of wire is used in car window heaters for defrosting.


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## Joe T (Jul 11, 2010)

Sometimes before I shoot I will pull the bands 3 or 4 times to warm them and loosen them up.Depending on the rubber sometimes the first shot can be kind of slow.In cold weather it might pay to stretch out and warm the rubber before every shot.---Joe


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## ZDP-189 (Mar 14, 2010)

That's odd, I find subsequent shots to be slower (though more consistent)


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## JoergS (Dec 17, 2009)

Rubber is an elastomer. This means it takes energy in the form of heat from its environment. Theoretically, the ideal temperature is just below the point where the chains disintegrate.

Can someone with a chrony do a little test for me?

Take a slingshot, shoot various ammo through the chrony and record the results. Then put it in the oven and heat it to 40, 50, 60 and then 70 centigrade and shoot again.

Can't do it from here!

Jörg


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## ARB (Dec 31, 2009)

I did a rough experiment this evening. Small starship, 1250 grain ammo, Silver Thera tubing

Without heating, temperature ~15 deg C
speed 138-139 fps

Put slingshot in the oven until the tubes were warm to the touch. 
speed 145 fps at first dropping to 141-142 after a few shots.

I don't know the temperature as I couldn't fit the slingshot in the oven and had to leave the door half open! But I think it shows that temperature of the rubber is something that should be investigated further.


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## Trent (May 30, 2010)

Carry the slingshot with the bands around your neck underneath your shirt and coat. That is what I used to do during the winter when I was a kid.


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## Flatband (Dec 18, 2009)

I held mine in my armpit to keep them warm. Will we ever stop this experimenting-HOPE NOT! Too much fun-heated bands-can you believe it-COOL!







Flatband


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## USASlingshot (Feb 25, 2010)

i would say heated socks is your best bet, i was thinking about tieing the sock to the slingshot somehow. that seems like the lightest option besides using hand warkers


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## JoergS (Dec 17, 2009)

My info is getting better after some online research.

It seems that 60, maybe even 80 centigrade will greatly enhance the retraction speed and efficiency.

My current idea us to use my roller equipped "W" design and let the flat bands run in aluminum tubes. Heating wire will be wound around the tubes and make them really hot.

RC car rechargeable batteries for the hefty energy consumption.

The tubes will be wrapped with isolating heat resistant foil for insulation and safety.

Should be fun!

Jörg


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