Primitive Archer
Main Discussion Area => Bows => Topic started by: gfugal on February 28, 2018, 03:48:31 pm
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Alright yall. I want to share with you my final physics project for my class last semester. My goal was to estimate arrow velocity using 4 different methods: chronograph, projectile motion, sound, and electric currents. Here is a link to a PDF of the poster as well as a picture of it.
https://drive.google.com/file/d/1sIaLNSEvLRSLbt6De_aokzuEgE4tHIuZ/view?usp=drivesdk
(https://lh3.googleusercontent.com/fTxdjaV5kFxJmWNMieZRFcIthxGlYBribvIqCeE_4Gsag9biWMdBLsanrFZGlwZ1gPk4TB3qInT42Cnm6JLro8rp0yTMJwnYyp5ZzDUIzrxS1VKL0qTpJbu00UCY3oDJ8lpj2M6ppAnbqmYV-4Qf2LSz8N6OZdswtWT5cbWBY74B7hmbDglxAwMukl3uyCPdmjcyKYVs3MNAWSPdINzpP-zAuW6KKljLX3DJnhw3nsR9ljSbFeeJTgSvzOm74-hvXp5AXpegZLaKYpG0GiRlEGQNaLAz4HPUSvd3AmCe_71wK9guzmpAxwa6le-SVHstFmXn0AUIH7tKuu26uyX5o7mfRnnXWOaTI6rgX5Cp5medTUp_TJw6RAD1w2ueR8Aqzfc2v35Y1B_brrj5H4ad8zdMXJgWmc3nIyOHvYY2QCf7-LtqkMLjmb3ogJJzo6WFnDXouv1NPBxePfrsU0-704GBD1qPeCGBsDTX_nff-qYYT9UZcOHKk8en0Q9vB8W1J7Yei4AFpESuya60IMcz6ji1ea_uayGDt0Bj5_xpvtMpET3IEcIhI2aBPBSiT-9_2_NvAfpQYWr4v7rhCTN7FT8L6L488F6dq43XzK2MZkvVnDQUrtojAy6AHnWeNGGb7-68T-7EInhcINP6Fo4wqS-ZMR9kswx9TQ=w982-h710-no)
For this project, I built a shooting machine so I could get more consistent and accurate results. Here's a picture of it.
(https://lh3.googleusercontent.com/Yi-7KsS_CkE-5KI1woqrDcTvwNq79aTznUDSHCMZ2fLa3yfdnYQ6GN3CMghiqR5hO0Ktoqv50w8ct35CSIrqVsg3t1VwBK2H4n_5gPjzRPMWOjFXU4XURURQfclLL-cmGvCR5jiIlyiabPuRmDrBNou9XpTKjvsnlctHosfkDKhIvnBrCw6h4GLUUeL4yRrE6TEV9TqhJd8OTBHV3GGobBZfCMnCXyPco9ratLs7r3nCzDNtRG9jhNH8DiOuAXiE6-Gs5lSHC7zFjV_Do-6b6KZNs1l-3lUW9epzxo-aACAwCvjaBBaFbPA_tYVyZz6MYQuVqmJLWfG1joretPr1_3bs2jgvjoPo-LOxuzU5QtaoO8_no9bdW_nBvyoU2V1friVqkV59248VihTmyF8rWKZ_IBY6hkJHHnoaFVbkgHpqLqYSOSNB3UitANLxYzzquNFqZq0G3yNKt3aDKUxMYpxlhtKJIYHAWJiO8OEw6zikIY9xWUzUaHsJ3x4nHi3S4KjfgCETgKTV59kog4KAN8nbDHBqNHulz6pPzTK5QVDyhx6a9IiOJ5ZFvW2a2QFAhBCu3wLRXiMUttAFZL9wPLnj_mTIrU-k-iZtwqoIlGyv3r-ibHf_tAZ768gZhIz0e4hbmjVEG0KU5SX-oNJxRcaPyrWgbTpIRQ=w533-h710-no)
(https://lh3.googleusercontent.com/wgoOrvZUuWLvXCsHOM0sCx3o71Ru2H4sSsQaIXPrDJFzuqyY12IgtJO0PKBRyRn7W5Y006vPmWsVDcGNVMygMnAA27W69t4c7dSv1cbEkZ_RMLLusb_eCw4pf6bXoKqudLCHBP3PK-13M1RIGaOWuC5ylMa6_6rQQmDBtzz9CYYzHFHz36296T5-bkuoXaMcZb-CpQHyfC-WRLAn7bLDNO6VBOotE9JygWMIgz6fRO8aRTFAJNzOiqNXclJM8n8RaA_GCm2pYcyoJO0swSCtjJyRZ1qTWI6X93PWZ7sqbiD6QK8HL07wOTvNbZ5iCJJo90pH9-uP8wvgEmIrXWjYsiPWNgZyCT2DJdwKwC1VwVjinlF_WeTRwhGXhnfHrTew7jgmQdHe4mdwvh6PtVQmZIiX5LyKZ2rvvHWTPrwP677MZ900WINIFjtVaGjvPo1ChSsyQIwSsH9S0pWVKQjjSejSZS_pB9JjND_3-UvDXCmaxgWeQlCoejgrUuGLe91x8Q34QEAGaef35_1YdzDN2O0AnBUTgXihaopedwl3GoY02t1S5CXmNPQ_rsncnWOYnaISluhzY5wW_NxSrvpF19EQS4kRp1PbVfGpgcpi=w533-h710-no)
Here's a youtube video that shows it in use, and gives you a little picture of how it works. (https://www.youtube.com/watch?v=O18ZtynJ2Do). I designed it so that it was adjustable so I can shoot it at -15°, 0°, 15°, 30°, and 45°.
The project was a continuation of an experiment I started a while ago. http://www.primitivearcher.com/smf/index.php/topic,59214.msg821468.html#msg821468.
Where I used this article (https://arxiv.org/ftp/arxiv/papers/1511/1511.02250.pdf) on pg 19 that sparked my interest.
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Pardon the fact that the bows on it aren't primitive wood bows ::). I didn't have one with me at the time that would have been suitable.
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very cool project, I would like to read more, as I am working on a similar one.
will hold off on too many questions until I can read the poster better
the link does not open for me.
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Cool Project, are you just looking for different ways to record speed?
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very cool project, I would like to read more, as I am working on a similar one.
will hold off on too many questions until I can read the poster better
the link does not open for me.
Yeah, I noticed that it wasn't working. I'll try to fix that by the end of the day. The poster doesn't go into how I built the shooting machine if that's what you're wondering. If so we could just discuss it.
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The poster doesn't go into how I built the shooting machine if that's what you're wondering. If so we could just discuss it.
Actually , my machine is a bit more of a fixture for take town limbs. The different speed measuring methods are something I am looking into at present. Trying to find a way to measure arrow speed down range, so that I can compare to speed readings at the bow. Alan posted a link to a company that is selling an pricey radar solution in a thread in the flight bow forum. I think I have to wait until that product matures some more or the price comes down.
I won' t be online for the afternoon/evening, so hope to post later. Thanks for offering.
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Cool Project, are you just looking for different ways to record speed?
Well, when I first got into archery I was frustrated by how expensive chronographs are. I used this physics project to convince the wife to get one since it was "a school supply" haha. But the idea behind this project is to offer alternative methods for people to determine their arrow velocity.
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I wish I could find a way to measure the speed of a flight arrow as it came out of the bow and at about 30 yards. The only thing I have noticed is that if I can see the arrow it is not a good shot, if I can't see the arrow it is usually a good shot.
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I wish I could find a way to measure the speed of a flight arrow as it came out of the bow and at about 30 yards. The only thing I have noticed is that if I can see the arrow it is not a good shot, if I can't see the arrow it is usually a good shot.
Yeah, the projectile equations I had to use were pretty complex if you take into consideration air drag, even then it's not completely accurate cause you have wind and the rod-like nature of the arrow and its fletchings which have such an impact on its trajectory. But still, I was able to get pretty close estimations from it. Regardless you are going to have to measure the distance the arrow went, so that method at least requires some way of measuring distance. I used a measuring wheel which was about $30 (1/3 the price of a chronograph). You technically don't need a shooting machine. There are imaging editing apps you can download for free that let you determine an angle in an image. So if you take a side view picture of the release you should be able to get the angle with that.
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I wish I could find a way to measure the speed of a flight arrow as it came out of the bow and at about 30 yards.
Steve, do you think that a reading at thirty yards is all you need? I wonder just how far out a good shot needs to stabilized by?
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I wish I could find a way to measure the speed of a flight arrow as it came out of the bow and at about 30 yards.
Steve, do you think that a reading at thirty yards is all you need? I wonder just how far out a good shot needs to stabilized by?
there should be a sweet spot. The longer it is in the air the more it can be messed with by the wind and stuff. Too short of a distance and minor errors in measuring that distance will result in big differences, plus the first several yards, before the fletchings stabilize the flight, are the most turbulent. The compound bow in the video shot at 160 fps. I put the shooting machine at 30° and it shot in the 160 yard range (or maybe it was meters I can't remember). I'm not sure where that sweet spot it is, but I'm guessing even 160 yards is overkill.
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That's a great project Greg.I would'nt mind having one of those around sometime.A friend of mine made one here and we found out because of the less friction release or trigger release that the machine shot a good 10 to 15 fps faster or more than finger realease.Depending on how well a person can release.
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I think the link for the poster should work now. Since it's formatted as a poster you will have to zoom in on a column to read it.
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Greg,
Nifty shooting machine! But what's that funny looking contraption on the end with wheels? >:D Lol! Sounds like a neat project, how did it score?
Hawkdancer
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With practice a human can outshoot the machine fairly easily.
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Greg, I read through the presentation poster a few times last night, and I hope you are open for a question or two. I am specifically interested in the sound/Audacity method. If I understand your set up correctly, you used one mic midway between the bow and the target? Then moved the target back some, and adjusted your equation for the second distance?
Since the equation above only gives the velocity at the distance of the target, it would be slower due to drag.
Wouldn't the speed be the average speed between the bow and the target, rather than the speed at the target?
Thanks
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Greg, I read through the presentation poster a few times last night, and I hope you are open for a question or two. I am specifically interested in the sound/Audacity method. If I understand your set up correctly, you used one mic midway between the bow and the target? Then moved the target back some, and adjusted your equation for the second distance?
It doesn't matter where the mic is honestly. We did it that way because the shooting machine was noisy and had a hard time picking up the impact. However, if your shooting by hand or had a less noisy machine, It might be better to have the mic next to you or behind you. You want to be able to hear both the release and the impact. Like I said there is no right spot for the mic, you just have to measure the distance it is from the bow, and the distance it is from the target. If you move yourself or the target to shoot at a different distance you have to readjust the equation since those distances have changed. Did I include that equation on the poster? if not it can be found on pg 19 of this article https://arxiv.org/ftp/arxiv/papers/1511/1511.02250.pdf
Since the equation above only gives the velocity at the distance of the target, it would be slower due to drag.
Wouldn't the speed be the average speed between the bow and the target, rather than the speed at the target?
Thanks
You are correct. It would be the average speed. However, there is still a decay, the average speed at 30 yards is going to be less than the average speed at 20. So I fibbed a little bit when I said it was the instantaneous velocity at the distance of the target. Most people wouldn't pick up on the idea of the whole average things as easily, so I used instantaneous Velocity as an easier way of explaining it. Regardless it shouldn't affect your ability to find the instantaneous velocity at release since the average of 1 yard is going to be pretty much that.
Another note I feel I should mention is that it's important to get several different readings at different distances in order to get that decay rate (unless you just cared about average velocity instead of instantaneous velocity at release). We originally wanted to do 20 yards, 25 yards, and 30 yards, but had an issue with changing draw lengths in the indoor range, so we only ended up with two viable distances. I would still go with at least three and I feel you would get a better slope for decay rate. It's also important to not shoot so close. There was a problem we were encountering in this thread ( http://www.primitivearcher.com/smf/index.php/topic,59214.msg821468.html#msg821468) where if you are shooting at too short of distances you have to be so much more accurate with your measurements, that even the difference of the arrow sound coming from the end of the arrow on release but the impact sound coming from the tip of the arrow on impact, made a big difference. It made it so you had to alter the equation to account for that arrow length to get accurate results. Even then it still had issues. I have learned that you probably don't want to shoot at any distances closer than 20 yards. I even think 15 yards would be pushing it. At further distances, the arrow length should be a negligible factor.
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With practice a human can outshoot the machine fairly easily.
I imagine so if they anchor too long with these wood bows.
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Thanks for the clarification, Greg. Hope you do not think that I am trying to be too picky with my questions, in fact you answered the next one I had also!
Perhaps you might have an idea about how to accomplish a slightly different task with Audacity? I hope to devise a method that actually measures the velocity of a single shot at various points down range, rather than extrapolating it from an assumed decay rate. The decay rate is actually the subject of the investigation.
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Thanks for the clarification, Greg. Hope you do not think that I am trying to be too picky with my questions, in fact you answered the next one I had also!
Perhaps you might have an idea about how to accomplish a slightly different task with Audacity? I hope to devise a method that actually measures the velocity of a single shot at various points down range, rather than extrapolating it from an assumed decay rate. The decay rate is actually the subject of the investigation.
I'm curious but not quite sure what you mean. are you talking about placing several mics at varying distance to pick up the arrow as it passes by? maybe you could do that with a whistling arrow and use the Doppler effect to determine when it passes the mic.
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I'm curious but not quite sure what you mean. are you talking about placing several mics at varying distance to pick up the arrow as it passes by?
several mics is a worthwhile possibility. I was hoping to avoid shooting through a series of paper targets to create a noise at each station, it might affect the velocity too much. I will have to look into Audacity to see what a frequency signature looks like. A sharp peak would be nice.
All ideas are welcome :)