I see where they have small accelerometers that could be installed on to an arrow. I am wondering how finite of readings I can get from one of those. For instance would I be able to read the force applied to an arrow durring a shot at maybe 1" increments? It would also be cool to graph out an arrow that left the bow at a 45 degree angle and look for areas that could be improved on.
Wouldn’t the weight of the accelerometer (however small) alter the usual performance of an arrow? Perhaps instead could you take high-speed video of the motion of the arrow, perhaps with a scaled background. You could then compare the distance various arrows have traveled in a given time.
(But as you’re the one here who has been working in archery for a long time, I assume you’re already familiar with the methods that people use to compare performance of arrows.)
With the imaginary accelerometeres I’m thinking of you could get those data. I’d attempt to give you information for real accelerometers if you’d supplied references to the kinds you think could be mounted on an arrow.
My WAG though would be that you’d get more accurate and complete data, less complicated a set up, and more relevant information from analysing high speed footage of a shot.
Dewey I belong to a very small group of scientists who like to explore the inner working of the bow and the materials used to make them. My contribution to the group has been more in the way of looking at things from different angles and comparing things that haven’t yet been compared. I also do a lot of backyard testing and number crunching. I depend on them to refine my findings and compare that to their own.
As a bow maker I would like the ability to be able to build data bases that could easily reflect the effects of small changes in design and accurately show where these changes occured durring the power stroke.
If an accerometer can do what I hope it can do I see it as a valuable componet in any kind of scientific quality testing station,as well as the high speed photography.
I agree 100% with the high speed photography, we have and continue to learn a lot from that. The arrow sized accelerometer is allready in use. I will look for the link and try to post it. I still haven’t figured out how to post links here.
An accelerometer will give you the acceleration of the arrow when it is shot, so you will be able to deduce the force, indeed.
Whether you get information at 1" increment is another question. The typical off-the-shelf accelerometer has a sampling rate of 100 or 200Hz. You need to get the specifications of your arrow-compatible accelerometer to know its sampling rate, and get a rough idea of how fast an arrow is shot from a bow so you can get an estimate of how many data points you’ll get.
I imagine that your arrow undergoes a strong acceleration (several G?) when it is shot. Are you sure that your accelerometer won’t saturate ? Try to figure this out, too.
Plus orminus 1000g is the range it will be working in. I will look up the specs you mentioned.
For some reason I cannot copy and paste the link here.
Pardon my ignorance, but are these mini-accelerometers more than just sensors? Or, do they also have data logging capability?
Because, if they’re just sensors, you’re going to have to add a clock, some memory, a power source, and a microcontroller. Now you have a heavy arrow.
I emailed the contact source for more info but all contact info is now defunct?
If the data sampling rate is too low, you could compensate somewhat by making many launches. They’ll all have different phases relative to the sampling, so you could fill in the gaps.
Incidentally, do you have a robot-arm setup to launch arrows consistently? This would help enormously in controlled experiments.
Once an arrow leaves a bow, wouldn’t the only acceleration be gravity and wind resistance?
I use a shooting machine with mechanical set release point.
Most of what I would be looking for happens before launch durring the power phase but I would also like to study the deaccelration and forces present durring the entire flight of an arrow.
You will have a hard time studying the arrow’s flight. The accelerometer will measure the sum of gravity and deceleration (see here), and you won’t know how to separate one from the other.
The usual way to extract the deceleration from the accelerometer’s signal would be to track your arrow’s orientation relative to gravity so that you know the gravitational component and, by subtraction, you can compute the deceleration component. But I fear that the gyros in a small accelerometer (if any) won’t be accurate enough to do that.
The arrow is more or less in free fall so there wouldn’t be much gravity.
If the sensor is at the end of the arrow you would be able to measure the flexing of the arrow during flight.
Excellent point. However, I believe you could still learn a lot about bows by keeping the arrow constant and changing the bow, or vice versa for arrows.
I disagree. The gravity of the Earth will act on the arrow, along with other forces like the bow’s string and air resistance. As mentioned above, it isn’t trivial to tease these apart, but they’re forces affecting the arrow. However, I suspect G is trivial compared to the force of the string, so if we’re comparing bows, it can be ignored (and it’s constant for all bows, as well.)
The sense in which you’re right is if we’re talking about the geodesic in which the arrow would fly after leaving the bow if there were no wind resistance (or the continuous “sequence” of geodesics that it would fly in at any point during the launch if contact with the string ceased). My guess is that the math is far simpler to just assume the force of G perpendicular to the ground.
Great point, especially if you can put two of them in, one at each end of the arrow! Of course, the mass of the sensor will affect the flex, but that wouldn’t make it useless for comparing different arrows.
There are so many aspects we attempt to study that one device like an accelerometer would hopefully add just one more tool. We all have a lot of theories as to what happens to arrows once they leave the bow and it would be nice to be able to correlate some of these to changes we make in arrow design.
Flight shooting cannot be compared to target archery for a lot of reasons. Everything we do is right on the edge of deminishing returns and we have a hard time recognizing when we have crossed that line. We use extremely light arrows for highest speeds out of the bow but we are sacrificing momentum tha resists drag. We are also marginal in stiffness and if the arrow flexes too much the light arrows loose too much velocity before they can straighten back out.
Light arrows also pose problems in bow design as they tend to leave a lot of energy in the bow limbs instead of a launched arrow. How well the arrow can control the bow limbs in the last few inches of the power stroke is an area all of us flight shooters would love to be able to study.
We all have dreams of building the ideal test station. I find it amazing how little we have progressed in the past 400 years. We are at a point now where splitting hairs are the gains we are looking for.I’m a super-amateur in the area, but my Arduino sensor boards are pretty light. I imagine you could connect a metre or so of light-gauge wire to a stationary base station so the effect on the arrow would be minimal.
Ah. Well you’ve still got a problem then. 
I don’t know how light it needs to be, but the unit could be as minimal as an ultracapacitor, a microcontroller, and a MEMS accelerometer (all connected directly via wires). The ICs are about 20 mg each. An ultracap sufficient for several seconds of logging (enough to turn the thing on and get your fingers out of the way) is 50 or 60 mg. So, all told one could keep it under 0.1 grams.
Unfortunately, I can’t find any MEMS accelerometers that go above 500 gees, and HBDC says he needs 1000.
Would you get valuable data from having the accelerometers mounted in various positions on the bow limbs/string itself and using a “standard arrow” for comparison purposes? I’m thinking high speed photos would be more valuable to establish arrow flex characteristics.