Homemade Chronograph

[Wrangler John]

Like wizdumb said, I too prefer the Magnetospeed chronograph, based on experience with two Oehler chronographs an M-33 and 35P. The main flaw in screen based chronographs is the time and hassle of setting up the screens unless one has range facilities where the mounts can be permanently installed. With the advent of inexpensive chronographs such as the Chrony, there is little to recommend building an IR chronograph, except as a rewarding learning experience. The IR chronograph would have greater utility in shooting tunnel or other indoor applications and ballistic labs. I build rifles from manufactured parts, cobbling them together from commercial actions, custom aftermarket barrels, and semi finished stocks not for any other reason than I find it fun to do with a superior product as a result. Same with desktop computers. For all that, most of this stuff in the forums and magazines is the same old stuff rehashed, your chronograph would be something new and different. Sort of like resurrecting the old Heathkits, where us old fans of DIY learned basic electronic skills.

I'm waiting for someone to develop a rifle scope or spotting scope (recoil disturbance of a rifle mounted scope may preclude that option) that incorporates some sort of LASER, IR or RADAR chronograph into the design. The concept would feature constant velocity measurement of the bullet from muzzle to impact, with the ability to recall velocity data at any given distance interval. This could also generate a dynamic B.C. for each bullet weight, shape and constriction, over the range.

[Wrangler John]

I'm certain they know that this is something folks want. I'd expect to see a version in the coming year that connects to a picatinny rail on many handguns (and some rifles).
It's a bit trickier to attach it to others, sure, but it's not impossible.

WAY faster/easier to setup at the range.
No distance-from-muzzle correction calculations are required
Not sensitive to light.

The Magnetospeed Bayo can be attached to a modified rifle or pistol rest so the muzzle is properly spaced above the sensor. They show such a test rig on their web site. I would be reluctant to attach the Bayo to heavy recoiling revolvers, such as the .480 Ruger and up, because I have had scope turrets and front sights part company with these revolvers, broken transfer bars, screws that disappeared, and even a hammer spur fall off from metal fatigue. Not to mention the excitement of having the entire revolver fly out of one's grasp, causing a juggling performance suitable for the Three Stooges. Indeed, anyone that has spent long hours in load development for big bore rifles and hand cannons, has suffered concussions, excessive sound level exposure symptoms (dizziness and nausea), scope cuts, bruises, bleeding hands and fingers, elbow damage and eventual carpel tunnel syndrome and arthritis, if not outright bone fractures. I don't want to expose my chronograph to such pounding.

[kylix.rd]

Like wizdumb said, I too prefer the Magnetospeed chronograph, based on experience with two Oehler chronographs an M-33 and 35P. The main flaw in screen based chronographs is the time and hassle of setting up the screens unless one has range facilities where the mounts can be permanently installed. With the advent of inexpensive chronographs such as the Chrony, there is little to recommend building an IR chronograph, except as a rewarding learning experience. The IR chronograph would have greater utility in shooting tunnel or other indoor applications and ballistic labs.

I chose IR so that I would not be beholden to the weather or ambient conditions. I do understand the limits to an optical system. Even an IR system can be screwed up by ambient lighting. I've already seen that first hand where if I'm wearing lighter colored clothes and I stand next to the screens, the reflected IR energy from the florescent fixtures will send the detectors spasming :-).

I build rifles from manufactured parts, cobbling them together from commercial actions, custom aftermarket barrels, and semi finished stocks not for any other reason than I find it fun to do with a superior product as a result. Same with desktop computers. For all that, most of this stuff in the forums and magazines is the same old stuff rehashed, your chronograph would be something new and different. Sort of like resurrecting the old Heathkits, where us old fans of DIY learned basic electronic skills.

When I looked at the chronograph systems out there the inexpensive ones where very simple and didn't provide any built-in statistcal functions. The others that did have these functions were very expensive or you had to add lots of extra goo in the form of expsensive add-ons. I can twist and turn the data any which way I want by merely updating the code on the device. Something "wizdumb" brought up that I may look at adding is compensating for the distance from the muzzle. Since I can actually measure the deceleration rate of the projectile, I can extrapolate from that all the way back to the muzzle by telling the device how far away it is. I can then get a much more accurate reading of the actual velocity at the muzzle. With my simple air-rifle tests, I easily can see nearly a 5-10 fps drop between screens 1-2 vs. 2-3. As you would expect, BBs decelerate less quickly than flat-nosed pellets. Since I can see the deceleration rate, the B.C. could be calculated as well (or at least the drag coeficient).

I'm waiting for someone to develop a rifle scope or spotting scope (recoil disturbance of a rifle mounted scope may preclude that option) that incorporates some sort of LASER, IR or RADAR chronograph into the design. The concept would feature constant velocity measurement of the bullet from muzzle to impact, with the ability to recall velocity data at any given distance interval. This could also generate a dynamic B.C. for each bullet weight, shape and constriction, over the range.

Radar... hmmm... Those are based on doppler shift. I wonder how much reflected RF energy would come from a smaller projectile. If shooting away from the radar system, the frequency would drop. A flat bottom projectile would present the best cross-section, whereas muzzle-loaders with round lead balls would tend to scatter the energy in all directions and may not reflect enough energy back. I don't even know if the lead would tend absorb the RF energy and not reflect it.

Just thinking out loud... :-).

[spamsucker]

You mentioned it already but the first thing that occurred to be was that you can with 3 detectors also very accurately identify the effective BC given the precise local atmospheric conditions.

What was the total cost you poured in? I'm extremely interested as I have the skills to do it and the inclination as well but I'd rather know before investing too much time and $$ if it's going to be excessively expensive without having to do any actual shopping. Any detail you want to post or PM would be very much appreciated.

[kylix.rd]

You mentioned it already but the first thing that occurred to be was that you can with 3 detectors also very accurately identify the effective BC given the precise local atmospheric conditions.

Yes, I could add barometric and temperature sensors .

What was the total cost you poured in? I'm extremely interested as I have the skills to do it and the inclination as well but I'd rather know before investing too much time and $$ if it's going to be excessively expensive without having to do any actual shopping. Any detail you want to post or PM would be very much appreciated.

I covered some of the cost details in post #11 above.

[johnny1290]

This is ridiculous. I love it!

[semperfidelis354]

This is awesome. I'd be interested in seeing a tutorial!

[p1choco]

Holy S! That's badass.

[rsrocket1]

FYI the Chrony Beta Master (about $110) does give rudimentary statistical calculations of Low, High, Average, Extreme Spread and Standard Deviation of readings in each of 6 strings with up to 10 shots in a string. I keep all my shot data in an Excel spreadsheet (also usable with free OpenOffice Calc) so these functions are all easily programmed and all I really need to do is to enter the data. Transferring the data via USB/Bluetooth/Wifi would be convenient.
If you look at the Shooting Chrony website, you can get these manuals and see that it uses complicated button press sequences and a user interface conceived in the 80's.

Once you get it working, you might want to make this a little more "bullet proof" (pun intended). The skyscreen sticks should be capable of being shot without tearing out the mounts. I make mine out of easily replaceable wooden dowels. The front should have a deflector so when (not if) you shoot it, you'll minimize the damage and parts replaced.

You might look at some folks who modify their traps by putting black cloth along the "walls" and "roof" to increase the S/N ratio. Cloth instead of cardboard/paper because a slight wind turns the whole contraption into a sail.

Good luck.

[kylix.rd]

FYI the Chrony Beta Master (about $110) does give rudimentary statistical calculations of Low, High, Average, Extreme Spread and Standard Deviation of readings in each of 6 strings with up to 10 shots in a string. I keep all my shot data in an Excel spreadsheet (also usable with free OpenOffice Calc) so these functions are all easily programmed and all I really need to do is to enter the data. Transferring the data via USB/Bluetooth/Wifi would be convenient.

That's what I found when I was shopping around. To get those kinds of stats from the device, you start moving up in price. The physical hardware is the same, only the software changes.

If you look at the Shooting Chrony website, you can get these manuals and see that it uses complicated button press sequences and a user interface conceived in the 80's.

And if I were building commercially, I'd want to make it for as little as possible too. I don't fault them for keeping costs low. Their "user interface" is tedious to use. I am not constrained by that so I can go "go nuts" I have a fully functional touch screen with a keyboard and on-screen "buttons". It's also resistive so I can use a gloved hand or a small stylus. I've toyed with putting a real-time clock chip into it so that I could timestamp all shots and series so I have a record of the data/time so I could track the data over time. With the keyboard, you could even enter other comments and caliber/load information. Its only software at that point.

Once you get it working, you might want to make this a little more "bullet proof" (pun intended). The skyscreen sticks should be capable of being shot without tearing out the mounts. I make mine out of easily replaceable wooden dowels. The front should have a deflector so when (not if) you shoot it, you'll minimize the damage and parts replaced.

I intentionally did keep the "brains" separate from the core of the unit. That was one thing I did notice about the lower-end systems, espcially the Chrony stuff. It's certainly compact and easily transportable... but one errant round and you'll be leaving it in the trash bin at the range.

Using wood dowels is certainly a good suggestion. The way I currently have the rods attached is via 1" steel spacers that I tapped one end at 8-32 and drilled the other out to 3/16". The rods just slip in and out. They are friction fit and since the plastic top "U" channel flexes a little it keeps them from flopping around. I had a bunch of them in my parts bin... so I used what I had.

You might look at some folks who modify their traps by putting black cloth along the "walls" and "roof" to increase the S/N ratio. Cloth instead of cardboard/paper because a slight wind turns the whole contraption into a sail.

Good luck.

Hmmm... that's a good idea too. I could probably use that thin black, porous cloth that stage designers use for the back "scrim". It needs to block/absorb light while also not flop around on stage in any movement of the air.

Hopefully the use of high-output IR emitters will be enough, but if I run into issues that's still an option.

[rsrocket1]

I'll PM you for more technical discussions.
Good job in putting this together. I know it would cost less to simply buy one and be an "appliance operator", but this is a hobby and half the fun is in the making and tweaking of what we are doing.

[Rugerdaddy]

Wow! This is really great, and seriously, kudos to you! But, doesn't this belong in the thread "Home Made Time Machines, Phasers, and Other Devices from the 23rd Century You Can Make in Your Basement"?

[cjskalka]

This is pretty sweet, glad to see another ECE hobbyist putting their skills into a hobby they enjoy. That AVR micro doesn't have an embedded RTC? Should have gone with an MSP430

[SilentPea]

Speaking of MSP430s, I have about 12 bare DIP packages sitting in a box by my bed... I should really get around to doing something with them! I wonder if I can rig up a bluetooth module and start getting smartphone crazy? Hm...

[Alan Sales]

Hello Kilix.rd
Congratulations on the project, I found very interesting especially for those who do not have access to high-quality chronograph, like me.
I'm building one too, and used the detector amplifier circuit from the project: http://nutsvolts.texterity.com/nutsv...?folio=36#PG36 , but it did not work.
Have you made any changes on the amplifier circuit to work?
Could provide the amplifier circuit you used?
I am very grateful for your help.

Alan Sales