Laser spine testing

PaulH

New member
I have thought about a cheap laser arrow spine tester for a while. Having found that you friendly auction site sells 1w laser pointers for less than ?3 I thought I would have a go.

It appears to work really well. It is very sensitive to spine variation. I'm in the process of calibrating it using a digital caliper, but for now it allows me to check how well matched my Cartels are.

The laser is suspended from the arrow undertest at one end. The weight, suspended below, is a calibrated 2lb bottle of water and hung from the midpoint through the base board. As the arrow bends under the weight the laser dot moves along the base board, currently on a linear (rule) scale, but when calibrated it looks like it will be a logarithmic scale.

Total cost approx ?6

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DavidH

New member
I've recently made a spine tester using a caliper. It just measure the deflection in increments of an inch. That can be used to calculate spine very easily, for woods at least

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PaulH

New member
I've recently made a spine tester using a caliper. It just measure the deflection in increments of an inch. That can be used to calculate spine very easily, for woods at least
I tried virtually the same design initially as the deflection reading is the final spine deflection if you null the caliper. I found it tricky to rotate the arrow without interference from the caliper as the caliper was quite stiff, but it worked well. I still need the caliper to calibrate it, but the laser allows me to rotate the arrow for spine variation without touching anything other than the arrow pile or nock.

I guess for wood arrows you are only interested in the spine when aligned with the grain direction.
 

DavidH

New member
I guess for wood arrows you are only interested in the spine when aligned with the grain direction.
well no, we should actually check to find at what point it is stiffest and align opposite that, I can see what you mean about rotating, I intend to stick a flat onto the caliper - my design is still a work in progress:)

Having said that, it works fine, I don't like the dial ones, trying to calibrate it I think would be difficult.
 

PaulH

New member
well no, we should actually check to find at what point it is stiffest and align opposite that
Ahh, I see what you mean.

I intend to stick a flat onto the caliper - my design is still a work in progress:)
I actually used the caliper the other way round (upside down) to how you show it. I then used the depth guage on the caliper to drop onto the arrow as it has a very small surface area.
 

DavidH

New member
I then used the depth guage on the caliper to drop onto the arrow as it has a very small surface area.
unfortunately my cheapo doesn't have a depth gauge, I've seen that done and it does seem easier and more precise
 
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