Magic Forest

Piezoelectric trigger for spud launcher

 

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Piezoelectric trigger

Introduction

This Kitchen Table Science experiment has been a long running idea first thought of by my close friend Peter . The general idea was that we wanted to build a large spud launcher, basically an enormous version of the childhood toy of the potato gun. We have been toying with the idea but never really found the time or place where we could get away from the wives to do it. We thought at first of using compressed air and then realised that it could get quite expensive so we decided that a butane gas explosion as a propellant was the way forward.

PLEASE NOTE THIS IS VERY DANGEROUS. ADULT SUPERVISION IS REQUIRED AT ALL TIMES

The video below shows the first ever explosion and the reaction from the Peter and I . Unbeknown to us Peter's brother-in-law, Ian was filming us!!!

The Challenge

Using a piezoelectric barbeque starter to explode butane gas

Constraints

£2.00

Items used

  1. Recycled piezo-electric BBQ starter
  2. Electrical wire
  3. 4 pint plastic milk bottle
  4. Butane gas for cigarette lighter
  5. Open space

Build Time

Total time 2 hours but only about 10 minutes without the laughs, jokes and experimentation

 

Method

Take a 4 pint plastic milk carton and thoroughly wash and dry it. The size of this carton is not important as it would work on a 1 pint or 2 pint carton. It jsut so happened that there was one in the bin at the time of the experiment.

A hole equal to the diameter of the spark section of the peizo asembly was made in the milk carton lid and the assembly then bolted into palce making a strong seal. The image directly on the left shows a small blue wire on the right hand side. This is the earth wire and is wrapped around the assembly and then attached to a metal tent peg in the ground. In a barbeque this would not be needed as the metal structure would act as earth.

 

Making the spark

As this was originally ripped out of a barbeque not all of the peizo assembly could be recovered due to the design of the barbeque. Therefore the addition of a thick copper arch was added to create a small gap between the tip and earth

We tried this out and then realised that although a spark was occuring no ignition was taking place due to a lack of oxygen in the closed container. Drastic action was required.

 

 
Making it all go bang

Drastic action was required and so we decided to cut the 4 pint container in half and half a make shift "cup". We sprayed in a liberal amount of butane into the up ended bottle and then pressed the trigger....POP....cheers now we knew there had to be a good mix of oxygen and after a few attempts worked out that you only needed a tiny amount of butane.

Finally we decided to put the base of the milk carton over the top of the other section creating a 2 pint container. We had already sprayed in some butane and let the air get to it and then we had a go at igniting it. You can see by my comment at the beginning of the clip above that I was laughing at the fact it didn't work when I tried again. The film shot above was the first time we had a proper ignition and for the end to pop off, hence the hilarity.

Just to put this into contect, I calculated whist doing a frame by frame view that the milk carton was actually doing 120mph at the time it left the frame...you have been warned this IS a dangerous experiment and I was follish enough to do it without protective equipment...next time I may not be so lucky...YOU HAVE BEEN WARNED

 

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