Little Help Please...

[Ghost_Lord]

I am currently looking for a piece of equipment to use in experiments I am conducting, and need to know where I can acquire, or how I can build, this piece of equipment. Here is what I need, and what the experiment will entail...

I need a device that can measure the force applied in a quick strike of one object against another. In specifics, I will be firing arrows at a target, and need to record the peak force of the impact. So it should be able to record values created in a short time span, such as the initial impact of an arrow. And it should run on an open timeframe, meaning it will not rely on me to press a button to record the weight, as it's almost impossible to time it correctly with the strike of the arrow. Arrows puncturing the measuring surface will not be a problem, as these are special arrows with blunt foam heads, designed not to pierce anything, I just need the force of impact recorded. I have seen in movies (and I realize that this could be a totaly made up item) pads used to measure the force of impact as from a punch or kick, this would probobly be ideal.

Do you know where or how I could acquire such an item? I am willing to spend up to 300 to 400 US Dollars on acquiring it, perhaps more. So please feel free to include items of this type that are in a high price range, as I do not feel too inhibited by cost. Though it is always nice to get a deal,

Thank you for your time, and I look forward to any and all information you can give me on this subject,

Ghost

 

[Nigel Goodwin]

The way the punch pads usually work is that they are basically a foam filled 'bag'. This bag has only one opening, and that's a small pipe out the back, so when you hit the bag, air is forced out the pipe, and the pressure of air down the pipe is a measure of the force used to hit the bag. You can get sensors which measure this air pressure, and then just display the pressure reading.

I presume you could construct something similar for your arrows to strike?.

 

[Pommie]

A couple of ideas.

This can be done mechanically with a pendulum but would need the arrow to strike in the same position each time.

Another way is to use the old method used for impact sensitive keyboards. The keys have two contacts - one when up - one when down. The electronics measure the time between the top contact opening and the bottom one closing to indicate how hard it was hit.

Another way maybe to use a cheap set of electronic kitchen scales. These have a load cell that would give a measurable pulse when struck.

Finally, why not put the point back on and use a telephone directory .

Mike.

 

[Nigel Goodwin]

Finally, why not put the point back on and use a telephone directory .

And draw lines round the shaft to indicate the depth :lol:

 

[Oznog]

I need a device that can measure the force applied in a quick strike of one object against another. In specifics, I will be firing arrows at a target, and need to record the peak force of the impact. So it should be able to record values created in a short time span, such as the initial impact of an arrow. And it should run on an open timeframe, meaning it will not rely on me to press a button to record the weight, as it's almost impossible to time it correctly with the strike of the arrow. Arrows puncturing the measuring surface will not be a problem, as these are special arrows with blunt foam heads, designed not to pierce anything, I just need the force of impact recorded. I have seen in movies (and I realize that this could be a totaly made up item) pads used to measure the force of impact as from a punch or kick, this would probobly be ideal.

Ghost

What an astounding coincidence! I happen to be a leading expert in the field of foam LARP arrows! No, seriously. I am!

There are some issues with measuring the force as you hope. It can be done but there's question of just how meaningful a number would be. First off, the load cell will measure total force, not the way the force is distributed across area, and that's critical. Second, the action on a rigid target is probably not too similar to striking flesh.

Which game is this for?

 

[tansis]

A piezo disc commonly used in alarm sounders can work in reverse
and is well suited to this application. This very system was used to record
the impact/landing of an ESA planetary probe (the name escapes me)

A PIC with its dedicated A/D channel might run fast enough for data aquisition, failing that a calibrated strip of tape on the screen of the oscilloscope.