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Trickling the entire charge, as the RCBS Chargemaster and Hornady Auto Charge do, can take a minute or longer. Throwing the bulk of each charge with a measure, to within a few tenths of a grain, and trickling from there, dramatically increases the speed of the entire system. No permanent modification is needed to automate the $84 RCBS Uniflow powder measure. The drum comes from the factory drilled and tapped to enable attachment of a handle or RCBS's press-activated linkage ... or a gear. Mounting a servo motor to the $22 RCBS Powder Measure Stand is almost as easy. A few holes must be drilled in the stand to attach the bracket as shown. Actobotics is a line of hobbyist robotic parts. Most of the needed parts are inexpensive precisely machined aluminum. A list to build the device shown is below. The servo motor itself is the most expensive part. One can get away with a less powerful (less expensive) motor, but I have found that a lot of torque is needed to guarantee that stick powders won't bind the powder measure. After trying several less powerful motors, I finally solved the problem with a 7.4 volt, 486 oz-in digital servo. In the photo, you can also see the 5/16" brass tube I use for my trickler, held in place with a $7.99 5/16" clamping hub. The other parts are: 37950S $149.99 HiTec HS-7950TH Digital Servo 44460 $49.99 HPP-21 Plus+ Servo Programmer (optional) 637110 $26.99 Servo Block (mount) 615234 $12.99 100T 32-pitch hub gear (goes on drum) 615190 $12.99 48T 32-pitch hub gear (goes on servo) 585442 $3.99 3" channel bracket 585628 $2.49 90 deg flat channel bracket 585532 $4.99 90 deg angle bracket (two needed) 534-3485 $.49 .250" 6-32 threaded aluminum standoffs (four needed) various 6-32 machine screws (an assortment of 1/4" to 1/2") To bolt the larger gear onto the drum with no wobble, in addition to a pair of 1/4-20 machine screws, some aluminum spacers are needed. These fit just right: Aluminum Spacer 1/4 OD x .192 ID x 1/8 Long (part # AS25-10-8, $.42 each). Total cost is about $380, including a Uniflow powder measure, stand, and all of the Actobotics parts. The servo programmer is optional but very helpful in configuring the digital servo. I use a $25 RCBS powder measure drop tube adapter (Sinclair part # 749-002-916) and some 5/8" OD brass tubing to drop powder into the pan on the scale. Some planning and bending is needed to get the powder to drop in a way that doesn't splash everywhere. The servo is controlled by software running on a PC communicating with it via an Arduino. See the other pages for information. |
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