Another project idea

I mentioned in my previous post that I’d come up with a new project that I want to work on, and that I’d describe it in my next post. Well, here’s the next post.

My wife and I are looking to buy a pistol. Her biggest concern (other than keeping it locked away, mostly from me) is the recoil. My biggest concerns are comfort, ease of maintenance, ability to shoot easily with, and durability. I’ve long liked Glocks. We’ve gone shooting a few times together, a couple times renting guns at the shooting range, a couple times with friends, and once with my dad. On top of that, I grew up shooting, received top accuracy in my hunter saftey course (wayyyyy back in the 90s) and was the youngest competitive shooter in my grandpa’s shooting club. So we have a few points of reference for the guns we’re interested in. My wife like’s 9mm pistols, .22 rifles, and my dad’s .38 special. She also had some fun with his .50 caliber black powder rifle but it was a bit more recoil than she wanted to deal with constantly. She hates 12 gauge shotguns and 30-06 rifles.

But in picking our own, she’s mostly worried about recoil. I’ve looked up charts of the energy that pushes back against the gun, but the way that energy is felt is affected by a number of factors, some of which include the weight of the gun, the amount of powder in the cartridge, the weight of the bullet, the momentum of the moving parts in the gun. Almost every site I’ve looked at though says that recoil is much more subjective than the numbers in a table. I’m sure there are many more that could be added to that list, but she doesn’t care about the math that goes into the recoil energy. Well, actually, that might interest her, she has a BS in applied mathematics and is working on her MS in data science. But as far as buying a gun, she cares about how the recoil feels.

So, I’ve been trying to think of a way to quantize the feel of the recoil of a gun. At first I thought of just putting a pressure sensor somewhere on the backstrap so that when the gun is fired the pressure of the recoil against the hand can be measured. But that doesn’t tell the whole story of what you’re feeling when you shoot. So I thought, what about an accelerometer? That would give me the momentum changes, and that should give you more information about the pressure and movement of the gun. That is, until I realized accelerometers only give measurements about momentum, not angular velocity (rotational energy). But gyroscopes give you angular changes. So I realized I’d have to include both an accelerometer and a gyroscope. There are chips known as IMUs (Inertial Measurement Unit) and they include both, and often also include a magnometer to measure changes in relation to the earth’s magnetosphere. I’m not sure how I’d incorporate the magnometer, but I think I could map the motion of the gun with the other two sensors into some data that she could use to select a gun based on the feel of just one or two.

Then I started thinking of how to connect the sensor to the gun. Maybe an under barel attatchment of some sort would work, but I think the mechanical stress of shooting the gun would require a more permanent attachment, something that the shooting range might not appriciate on their rental guns. The measurements made under the barrel might not accurately represent the feel of the recoil in the user’s hand either. But a glove that is worn on the user’s primary hand might do the trick. I could measure the motion of the user’s hand when shots are fired. This would also allow me to make the sensor portable and quick to ready. I could even embed a pressure sensor or two in the palm for measuring the pressure against the hand.

So there it is, a shooting glove that measures the telemetry of recoil when firing a pistol. There might be something out there like this, but I have no doubt it would be expensive. Doing it myself would cost me a few dollars for the pcb at JLC, about $10 for the IMU at digikey, and a couple of bucks for incidental components, and as little as $3 for a bluetooth module to relay the information back to my phone, or similar for a usb port and data logger. I have two 3D printers and could print out any housings I need after desiging it in FreeCAD. It would take me some time to develop firmware for the device, and then a bit more time to write an application to gather and display the data from the device, whether that be for my iPhone or my computers. I’m fairly comfortable with C, C++, and Ruby, am a little rusty on Java, C#, and Python, Javascript, and could pick up Swift as needed. So all in all, I could probably have this up and running for about $50 and a bunch of hours. Who knows, people might be interested in this thing if there isn’t something around like it. Maybe not.

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