DIgital Torque Meter for Rubber Powered Planes
Description
This digital torque meter is used to carefully wind rubber for indoor rubber powered model airplanes. I designed this around a scale that can have the auto-off disabled. The selected scale is also a low profile display, which allows tilting to a higher angle for better distance visibility. This meter approach borrows heavily from Jake's. Print Details: You will need to print one of each, except choose only one arm length to print. The arm lengths allow different units as follows: 2.8" arm, set scale to g, readout is in oz-in * 10. This is my preferred setting. 0.5 oz in will display as 5.0. 50mm arm, set scale to carats, readout is in g-cm 1-inch arm, set scale to Oz, readout is in inch-oz You will need to print two of the collars. Assembly: The assembly is very similar to Jake's, and details can be seen at [HPA](https://www.hippocketaeronautics.com/hpa_forum/index.php?topic=22468.0) The meter is more similar to the later version, so be sure to read through to the end. You will need the following items in addition: * Scale: Amir 500g scale, [Amir Scale](https://www.amazon.com/gp/product/B01HCKQG7G). MUST BE AMIR, not a look-alike, to be able to disable auto off, and to ensure parts fit * Dubro 1/8" wheel collars (3) * Dubro 4.0 x 14mm socket head cap screws (2) * 4-40 x 1/4" set screws, such as [Set Screws](https://www.amazon.com/gp/product/B07GFJXBDN) (3) * 1/8" ball bearing assemblies, [Bearings](https://www.amazon.com/gp/product/B00X8KXAFG) (2) (I liked these better than the roller bearings) * 1/8" music wire or shaft, about 3" long * 1/32" music wire for hook, about 3" * 1/32" music wire for anchor, about 1/2" long * Kevlar fishing line, I used 60# test The scale must be carefully disassembled before use. Carefully pry the SS tray off the platform, using a small screwdriver. Careful to not distort or load the load cell. Once that is off, you can get to all the screws to disassemble. Keep the small screws. When removing the electronics, keep track of what buttons go where. Use a Dremel to cut out the battery holder, or purchase a 2xAAA battery holder online. Mount the electronics in the front face panel, reusing screws from the scale. Pass the load cell and battery box through the largest opening on the front, then place the display face on, top first, and snap down into place. Use two of the longer tiny screws form the scale to screw the faceplate on from under the torque meter. Glue the battery box in with Shoe Goo or Goop. Mount the load cell on the appropriate stand depending on the length of the load arm. Use two 4mm bolts, and use the spacer form teh original scale. Be sure to mount the correct end, the same end that was fixed in the scale. the wheel collars are a tight fit into the collars and the arm, at least with my printer. Put a Dubro (supplied with collar) set screw into the collar, and screw down well below the collar surface. Now align the hole in the plastic with the set screw hole in the collar, and press the collar in with pliers. You may need to tap it in with a drift. Unscrew the set screw, and it will cut threads in the plastic as it comes out. Now insert a 1/4" long set screw through the plastic. If you don;t do it in this order, you will have great trouble getting the set screw aligned into the collar. Follow the Hip Pocket tutorial for assembly of the shaft. The front (outside the case) needs to be long enough for the plastic collar to clear the display faceplate. Grind a small flat for each set screw to ensure it does not slip. Be sure motion is free. If not, try re-seating the bearings.
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