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PostPosted: Tue Dec 13, 2016 7:54 pm 
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Joined: Mon Apr 17, 2006 9:31 pm
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Location: New Mexico
Age: 65
Homemade Automatic Resetting AR500 Rifle Target
To keep my club members of NM MILSURPS interested in my matches, we looked into buying an automatic resetting AR500 target for rifle fire 100 yards and further.
Companies that make such things are rare and very expensive. Most were in the thousands of dollars to purchase. The lesser ones were powered by compressed air or 12/24 volt batteries. Neither option is practical or cost effective for an all day match. Some even have to be sent back to the factory to be re-charged!
I looked for on-line plans and found none other than some wire pulled targets.
I was on my own. I knew what I wanted the target to do. The target needed to erect itself; fall when hit with almost anything fired at it, and be able to take any rifle round hit under .50 BMG.
While it sounds simple in concept, there are factors in play that must be accounted for in order to build the device.
The target must be large enough to be seen with open sights at 200 yards or father. The target must be able to hide behind a firing range impact berm, or at least be able to be protected from a “bad shot” and destroying the drive motor or electronics components.
The system used to reset the target must be able to lift the weight of the target and erect it to be shot again. It must be able to do this quickly and safely.
The system needs to be man portable by one or two men at most.
The system must be dependable and able to run in any weather condition within reason.
The complete system needs to be cost effective and easy to set up.
I had my work cut out for me.
After working for the last 50 years I had picked up a few things that are life’s truths. When moving a heavy load, use a lever. Amplify torque though a gear reduction. DC motors are very powerful for their size. A higher DC voltage is very efficient and prevents motor brush burn out.
Use strong material and over engineer the design by at least 20%.
Keep it as simple as possible. Keep moving parts down to a bare minimum. Use gravity when you can. Kinetic energy can be good and bad.
I had a good “mind’s eye” plan in my head. If I could cobble it together, it should work. I never use a written plan or schematic. I see the project finished and work to make it so. Such as the sculptor who sees a statue in a rock.
I would build a prototype to test my ideas and range test it for proper operation.
First thing needed was a good strong dependable drive motor. I found a 90 VDC gear reduction motor and driver board used in the Dairy business on Ebay. Motor is 1/8TH HP and has lots of torque. I would further increase the torque though a #40 drive chain and sprocket size. Motor is about 8 pounds.
Motor and control board/power supply found on Ebay for less than 50 bucks with shipping.
Next up was the frame to hold the motor and the driving forces it will develop to lift the AR500 target.
I found scrap steel at our range and the city said “take all you need”. Other steel was found at a Junk Yard. Total out of pocket was less than 8 bucks.
I wanted to reduce friction of the support shafts for the chain drive and axles for the lifting arm and target base. Ebay had 5/8” heavy duty Pillow-Block bearings, 22 dollars for four with shipping.
I needed a way to help “cushion” the falling target arm and the heavy target. A section of Road-Alligator and a discarded old car tire. Free.
Now I needed to think about controlling the target. Very simple in theory. In practicality, it would take several hours to work out. There are factors most would never consider until the target was built and it did not work as planned.
The target must be raised past the 12 o’clock position. This is critical for two reasons. One, the target must be “wind proof” There must be enough mass at rest to overcome any wind gust. Two, the target must be held at this position for a known time until the target nodes subside. Remember, the target is being raised quickly and the target is several feet above the ground. When the target strikes the positive stop there will be nodes similar to the action of a diving board. Until these nodes subside, the target will try to fall back towards the ground by gravity alone.
I will be using two methods to prevent these nodes from causing the target falling backwards after it was reset. I used a powerful rare earth magnet and a pair of One Way Air Springs. These springs dampen the forward movement of the heavy target slowing it down as if brakes were applied. These springs only slow in one direction. They reset instantly and do not push on the target frame when fully compressed.
Controlling the drive motor is the key to dependability. How the target is raised is paramount. Too fast and the frame will be damaged. Too slow and the target will take too long in a timed match.
The motor must be turned on and stay on instantly. This is done by a control circuit board that has a Latching Relay being triggered by a momentary switch. This switch will be activated by the target as it struck by a bullet and falls by gravity and hits the At Home stop. This stop is higher than where the chain driven lifting arm rest to allow the lifting arm a “running start” to help lift the target faster. The At Home stop is also covered by a piece of road alligator. This does some modest cushioning of the falling target and houses the momentary “start” switch. The main falling target cushion is the old car tire. It takes 99% of the falling target force. I have never found a better device to use.
The latching relay on the circuit board is turned on by the switch in the At Home stop and turns on the motor which then turns the chain that raises the lifting arm which has a roller blade wheel bolted to it to reduce friction. Since the relay is latched in the “ON” it has to be turned off by another switch or the motor will continue to run burning out the drive motor or blowing a fuse.
This is where the Target nodes have to be accounted for. Having a second switch to stop the motor will not work; yes, the motor will turn off but the target nodes (diving board effect) will cause the target to spring back and fall backwards instantly.
To allow for these nodes to die out, I’m using a Time Delay Relay (TDR). You dial in the seconds or fractions thereof, to allow these nodes to die out. The lifting arm will set the target and continue to drive for a few seconds and stop the nodes, then stop the drive motor. Then after the TDR has timed out, the lifting arm can be returned to the Start position.
Once again, lessons in life came into play. I could reverse the DC motor and drive the lifting arm back to home. It is just more switches and things to fail. Remember keep it simple.
You have stored energy in the drive chain and DC motor that has just driven the target into its raised stop. If you leave a little slack in the chain, the slack will wind up on the drive sprocket and work as a spring under tension. Once the time delay relay has stopped the drive motor, the chain will instantly “unwind” allowing the lifting arm to free fall back into the start position. It works very well.
There are other electric/electronic devices needed to run this target.
To put the target in motion, here are items I’m using to allow safe, dependable operation.
I use a terminal strip to wire my components. I use two primary voltages. 120 VAC and 12 VDC. DC voltage is very stable and does not require 60 cycles to work properly. It also is not lethal. (The motor controller has its own built in 90 VDC power supply)
The terminal strip allows clear viewing and trouble shooting of all circuits hooked to it.
The latching relay board controls a small low amperage control relay. This small relay feeds 120 VAC to the time delay relay when the start switch is triggered. The TDR in turn provides 120 volts to the coil of a 40 amp contactor, which closes and provides a path for 90 VDC from the motor control board directly to the motor. This contactor will be channeling many amps to the drive motor when lifting and is driving the target into the positive stop to stop the target nodes. This contactor needs to be able to handle 150% of the actual load. Too small of an amp rated contactor and the silver contacts will vaporize.
The target is raised as the TDR times out, and the TDR sends a re-set signal though contacts to turn OFF the latched relay, the motor stops, the chain unwinds allowing the lifting arm to fall to the start position waiting for the target to be struck, fall and make the At Home switch. From start to finish the whole operation takes less than four seconds for the complete cycle. The target is upright in 1.5 seconds. Stopping the nodes takes 2 seconds.
The old car tire provides a needed boost to raise the target. As the target falls and hits the At Home stop with the Start switch, the tire resting on the ground right behind the lifting arm stops the target arm from having whipping* action, compresses the tires sidewall, and then springs back, pushing the target upward. Since the switch had been made, the lifting motor has already started to move the lifting arm. This “boost” from the tire springing back helps overcome the “body at rest” phenomenon and the target takes less energy to rise to the up-right since it is already in motion. This switch making and bounce back of the tire happens so fast you almost cannot see it in operation.
*The whipping action of the support arm can be so violent when it strikes the At Home stop it can bend or snap the target supporting arm in half. AR500 steel is heavy. Trust me on this as I just snapped a 1” in diameter aluminum bar 48” long in half testing this target due to uncontrolled whipping action.
I power the target system from a 4 KW gasoline generator. It provides power via an extension cord. The generator is far from the target and it is well protected from a “stray shot”. The 4KW generator handles the stalled DC motor very well. A too small generator will bog down under load and burn out the motors winding/brushes or blow a fuse.
At the positive target stop, the stop itself is angled towards the shooter by three degrees. This angle is the “wind proofing” and it works. However, the slightest hand push will cause the target to fall. Any center fire pistol and rifle caliber should cause the target to fall. I have felled the target by using 6.5 Swede,8mm Mauser,7.62x39,7.62x54R and 6.5 Grendel so far as a test. I have many more calibers to test.
I have not yet tried .22 LR and .25 ACP at 25 yards as yet. These would be the least energy producing rounds to try.
Back at the positive stop. To help stop target support arm nodes, the support arm strikes the two Air Springs, these slow the weight and inertia of the target being raised in a controlled manner. No matter how fast or hard these air spring are struck, they always slow at the same rate.
A note on this raising target energy being stopped; it is impressive. So much so I had to add “legs” at the base of the unit that extend towards the shooter by three feet. These legs prevent the whole system from flipping over towards the shooter. A body in motion, etc. AR500 is heavy, get it moving fast and it wants to keep moving.
The target support arm now is in range of the pull of the rare earth magnet. This pull holds the target upright against the positive stop and prevents any wind or missed shot striking a protection plate from shocking the target into falling. This free air pull is about two pounds. This tiny force is far less than any bullet strike.
The target is mounted to a fence T-post that fits into a double section of Uni-Strut. There is just enough play between the two to allow the target to slightly turn, deflecting* bullet energy away from the system components. This slight movement not only protects the support arm and T-post, it moves the support arm out of the magnetic field. The target can only move backwards as gravity takes over and the target falls, starting the whole cycle all over again. This happens in a blink of an eye.
Directly under the target, mounted to a non-moving part of the target stand, is a 1/8th inch steel shrapnel deflection plate. This must be used to protect the Air Springs, magnet, switches and the lower drive mechanisms. My first test plate was mounted parallel to the ground. The steel plate was deeply scared by bullet fragments moving at high velocity. My new shield is angled like a pitched roof at 60 degrees. The angled plate works much better.
It has taken me 70 hours to build this target and make adjustments to allow 100% dependability.
There was no machining needed, and other than a welder; everything was made with hand tools.
I will enclose the electronics in a weather resistant container in my final version.
Bill of Fare:
Latching relay board-Ebay 5 dollars free shipping
40 amp/50 amp surge contactor-Ebay 18 dollars with shipping
10 amp Ice cube relay and mount-salvaged from discarded electronics-Free
Steel plate, flat stock, and angle iron, Free from range as scrap. (Old range target frames/stands)
Momentary switches, Normally Open (NO) contacts-salvaged-free
Wiring 18,16,14,10 gauge-salvaged-free
Road Alligator-Free
Old car Tire-Free
5/8” heavy duty pillow block bearings Ebay-22 Dollars Free shipping
¼” cold rolled Steel plate from Junk Yard- 8 dollars

Two 5/8” mild steel drive/support shafts 24” each- local purchase – 20 dollars.
Welding rod- donated-free.
Terminal strip- salvaged-free
Nuts, Bolts, screws, washers, salvaged –Free
Electrical lugs, spade connectors, loop connectors-Harbor Freight- 7 dollars for 100 kit.
Paint- El Cheapo Flat black- two cans- Home Depot- six dollars.
Uni-Strut steel –donated-Free.
T-post- abandoned-salvaged-free
AR500 Armor plate ½” thick (bullet resistant at 100 yards for high power rifle) - Sizes vary by diameter and shape. 20-75 dollars each. 50 dollars was average.
90 Volt DC drive motor and control board- 50 dollars.
My labor-Free-70 hours.
Out of pocket was $186.00. If you like to scrounge around, ask friends or ask your shooting range, you’d be surprised what you may find for free or very little cost.
Ebay has a wealth of electronics from all over the world. Many items are over-runs or obsolete stores and you can get the items for next to nothing. Many with free shipping. It is hard to beat that.
I built my target for less than 200 bucks. This beats the heck out of the $3,500 target that does the very same thing for more and does not include shipping and does need to be sent back to be “re-charged”!
If I can build my target from scratch, you can too!
*All of my targets are angled slightly downward towards the ground. All bullets/Shrapnel are directed into the ground/shield. Edge hits are deflected into the range impact berms. There is no possible way for a bullet to ricochet back at the shooter in my designs. Always use AR500 armor plate. Never use less than AR500 steel.
I hope you enjoyed my article.
Rapidrob.

A short Video of the resetting target operating.
https://youtu.be/mCA9-11SLLY

_________________
Tonkin Gulf Yacht Club
President NM MILSURPS


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PostPosted: Wed Dec 14, 2016 1:16 am 
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Mil-Surp Shooter
Mil-Surp Shooter

Joined: Fri Apr 10, 2015 9:20 pm
Posts: 139
Location: NEW Mexico
Age: 68
Looks really good Rob! Can't wait to try it out Sunday.


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