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Author Topic: 3D Printed Digital Torque Meter Build Thread  (Read 6025 times)
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dslusarc
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« Reply #25 on: September 20, 2017, 11:38:56 PM »

I have a feeling that on these cheap scales they give slightly different values depending on where the load is applied to the load cell and that the precise centre is not necessarily,consistently the best.

If you look at the photo before I take off the 2 screws holding the load cell to the bottom of the pan, the stamping has a smaller rectangular section that touches the load cell. I found that if a weight was added to the load cell anywhere in that width (about 3-4 mm on either side of the screw centerlines) the weight was the same, as I got closer to the center of the cell, about 6mm from the centerline it changed .01gr. So there is a pretty wide range for the load to be applied. On this design, the transfer washer at the 1" arm length is right at the centerline of those tapped holes.
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Tapio Linkosalo
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« Reply #26 on: September 21, 2017, 12:30:49 AM »


Maybe use rechargeable NiMh cells and charge them in-situ?
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Hepcat
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« Reply #27 on: September 21, 2017, 08:01:27 AM »

Response to #23.

Thank you Andrew,
Of course I immediately opened my scale to prove you wrong. I had a convenient bottle that weighs about 20g.  I put it on each corner (to be honest overlapping a little) of the platform. I was amazed that the only difference was an occasional flicker in the second decimal place (20.12 or 20.13). Education can be embarassingly quick with the right teacher!
John

 
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John Barker UK - Will be missed by all that knew him.
jakepF1D
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« Reply #28 on: September 21, 2017, 11:50:26 AM »

These are pictures of a newer prototype, but as you can see, it's not difficult to remove the batteries.
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dslusarc
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« Reply #29 on: September 24, 2017, 11:09:19 PM »

I printed out the new version that uses a fiber supper for the thrust load and it is not completed. The new design required a new enclosure to be printed as well an  new cover (slide on and off cover) , and the new collar to hold the thread fiber.

First photo is the load cell and battery holder transferred to the new enclosure.

Second photo, I also installed two rulon J bearings into the new case then used a single edge razor to slice off the excess.

The new shaft is only 1.75" long for this revised design. A short piece of .047 wire about .35" long is needed to hold the thread, in this case spider wire brand fishing line. I cut about a 12" long piece of spider wire and I feed the two ends through the new collar. I drilled a .047 hole in the collar for the thread to come out. You put the short piece of music wire into the new collar so that the loop of the spider wire goes around it. Then press the music wire into the groove on the collar to hold it into place.
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dslusarc
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« Reply #30 on: September 24, 2017, 11:18:16 PM »

Then the rubber hook was installed as well as the torque arm assembly and the new collar to hold the spider wire. Make sure the torque arm is positioned so that the transfer washer does not touch the front of the case.

Cur a piece of .047 wire about .65" long, this will hold the thread to the back of the case. Press the wire into the hole until flush with the top of the case.

Thread the the two ends of the spider wire through the hole on the back of the meter. One thread end needs to be on one side of the music wire stop and the other thread on the other side of the music wire stop. Pull the thread ends and then tie a knot making sure the knot goes down into the hole. Then I tied about 6 or 7 more knots to ensure the knots don't slip when winding when the rubber is pulling. I then used a scale and pulled on the hook on the front to about 8 pounds to make sure nothing slipped.
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dslusarc
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« Reply #31 on: September 24, 2017, 11:23:25 PM »

Here is how it looks all tied. Again make sure when pulling on the hook that the transfer washer does not hit the case anywhere, or the collar holding the thread. When I tied mine I pulled until the hook collar was rubbing on the face of the meter, after it was tied there was a little slop so the hook collar cleared. You may need to do this step a few times to get it tied just right.


The last photo is the finished product with the new case cover slid in position. This meter when I pull on it now with a rubber motor there is no longer the friction from the pull on the front sleeve that was in the earlier version I did at the beginning of the thread.

Don
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« Reply #32 on: September 25, 2017, 03:09:57 AM »

How do you attach this winder to your tripod  winding stooge?
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jakepF1D
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« Reply #33 on: September 25, 2017, 01:48:51 PM »

I wind on top of my model box, and I use 3M dual lock to attach it.  It's basically Velcro on steroids and I've never had my torque meter come loose, although I'm only winding F1D motors.
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jakepF1D
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« Reply #34 on: September 25, 2017, 03:09:33 PM »

Then I tied about 6 or 7 more knots to ensure the knots don't slip when winding when the rubber is pulling. I then used a scale and pulled on the hook on the front to about 8 pounds to make sure nothing slipped.

I used a simple overhand knot, and adjusted the length until it was just right.  Then I added a square knot behind the overhand knot, and put a drop of thin CA on it.  I've pulled as hard as I'm comfortable with, and the knot hasn't slipped at all.
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Skymon
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« Reply #35 on: September 25, 2017, 03:36:17 PM »

Some really great development work happening here. It's turning in to a very nice product.
Had you considered putting it on shapeways or does Thingverse off the same type of printing service??
Could you look to reduce the wall thickness to reduce the cost and time of printing??
Best regards
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jakepF1D
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« Reply #36 on: September 25, 2017, 04:12:07 PM »

Some really great development work happening here. It's turning in to a very nice product.
Had you considered putting it on shapeways or does Thingverse off the same type of printing service??
Could you look to reduce the wall thickness to reduce the cost and time of printing??
Best regards

Thingiverse does offer a printing service, but I'm also about to announce availability of complete torque meters.  I'm selling them as a fundraiser for the junior F1D team.  I haven't figured out how much to ask, but they cost me about $15-$20 each to build.  Anything beyond that will go as a donation to the junior team.

The file versions I plan to post tonight will be the final version.  I can reduce the wall thicknesses a bit, but it honestly doesn't make a major difference in regards to print time.  With my printer and slicer settings it takes about 6 hours to print a complete torque meter, and reducing the wall thickness might drop that by 20-30 minutes.
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jakepF1D
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« Reply #37 on: September 26, 2017, 11:16:09 AM »

I posted what I think will be the final version of the files last night on Thingiverse.  Most of the changes are cosmetic, but I did thin out the walls a bit to reduce print time slightly.
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AlpineWarren
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« Reply #38 on: April 14, 2018, 07:31:23 PM »

Quote
I'm also about to announce availability of complete torque meters.  I'm selling them as a fundraiser for the junior F1D team.  I haven't figured out how much to ask, but they cost me about $15-$20 each to build.  Anything beyond that will go as a donation to the junior team.

Sent you a message Jake.  Smiley
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ceandra
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« Reply #39 on: December 24, 2019, 02:36:45 PM »

My modified version of Jake's torque meter.

We built this around a scale we found that can have the auto-off disabled. Not needed for most classes, but for extremely long SO rubber and thin, the torque does not change enough in the middle of winding and the scale shuts down.

The box is wider to accommodate the scale electronics. This allows choosing a 2.835" lever arm (Set scale to g, read oz-in*10), a 50mm arm (set to CT, read g-cm), or 1" arm (set to oz, read oz-in). I used a printed lever arm as well. The display is tilted 45 degrees, which also helps with the very long rubber.  Otherwise a lot of Jake's built in here.

I also have one of Jake's meters. His display is a bit larger, which is nice.

Chuck
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« Reply #40 on: April 03, 2021, 10:46:29 PM »

Hello,

I have been working on a project behind the scenes on a project that takes heavily from the ideas here, most heavily from Jake but the ideas of others are present as well, and some of my own and the team that I worked on this project together with.

This torque meter was built up around an Arduino Uno which allows it have some features not available in other meters. Currently the main difference is the real time graphing of torque vs time, but we are working on some other features in the future.

The cad files are available on Thingiverse under user "jaycub_fly" or at this link: https://www.thingiverse.com/thing:4815406/files

These files are named in an odd manner, but because of some design choices between my team and I, we included each of our preferred set ups, as well as offered some that we thought may be wanted.
Body:
Standard vs Extended Length: the difference between these is that the extended has a slightly longer top side that allows the cap to go under a ledge which allows for a different fit.
Ledge vs No Ledge: because everyone uses different methods of mounting their torque meter to their box, we have a ledge version where in the ledge slides into a small overhang built onto our box and has a front ledge to keep it from sliding forward. The no ledge model has no ledge and is currently held in place using velcro on our setup.
Front Cover:
2 vs 4 hole: this is just a choice between having 2 or 4 holes to mount your OLED to the front of the meter depending on the builder. This cover is meant to protect the OLED from any potential damage but do note that the OLED can still be damage in some circumstances.
Cap:
Standard vs Extended: this goes with body, simply choose the same length as the body you want to print.
Finger Hole vs No Finger Hole: this is a small notch in the lid, about the width of a finger that can make it easier to remove the lid.
Lever Arm:
Pin vs No Pin: the pin is a .062 music wire pin that allows the load to be applied in a single spot. We are not fully sure how drastic the difference is between the pin vs no pin lever arms, but we have given both for those are unable to acquire or simply do not want to cut such thick music wire.
Hook to Shaft:
this is very similar to the other torque meters in this thread and just connects the driving shaft to the winding hook
Wire to Shaft:
this is very similar to the other torque meters in this thread and has space for a .062 music wire pin to be dropped in with some kevlar fishing line(like spiderwire) to allow for minimum friction loss while retaining the shaft from being pulled out of the meter.
* for those unable to access or cut the .062 music wire, we are currently researching other alternatives and see potential in a thicker gauge paperclip, brad nails, and T-pins, however, mileage may vary as this was originally designed around using .062 music wire.
** the parts were made with respect to our printers and our tolerances, your mileage may vary on some of the interlocking parts - like the cap

The code is available on Github under user "jaycub-fly" or at this link: https://github.com/jaycub-fly/torque-meter

You will also need to download the HX711 and U8g2 libraries, which can be done through Sketch->Include Library->Manage Libraries->then type in each library name and download.

There are parts that you will need to purchase for this which can be found at this Amazon list: https://www.amazon.com/hz/wishlist/ls/31A5X0OZNRRX7?ref_=wl_share

Aside from those parts from Amazon, you will need to purchase some things from the hardware store:
- 2x 6-32 set screws
- 2x 8-32 nuts
- 8-32 threaded rod
- 8-32 ID bushings
- some Dupont connectors and wires
- .032 music wire
- .062 music wire
* some m3 screws, 4x 6mm and 4x 12mm can be purchased if you do not want to buy the whole lot from Amazon, but be warned you should be careful as some screw heads are too large for this design, particularly around the Arduino and load cell amplification board mounting holes.

The code found on Github has the same wiring information commented as below but I thought I might as well include it here.

Wiring Guide:
Load Cell:
- connect the red wire from the load cell to the E+ header on the load cell amplification board
- connect the black wire from the load cell to the E- header on the load cell amplification board
- connect the white wire from the load cell to the A- header on the load cell amplification board
- connect the green wire from the load cell to the A+ header on the load cell amplification board
OLED:
- connect the "GND" header to the 5V header on the Arduino
- connect the "VCC" header to the ground header on the Arduino
- connect the "SCL" header to the A5 header on the Arduino
- connect the "SDA" header to the A4 header on the Arduino
Load Cell Amplification Board:
- connect the "GND" header to the "GND" header on the Arduino board along the digital side of the board
- connect the "DT" header to the digital 2(D2) header on the Arduino board
- connect the "SCK" header to the D3 header on the Arduino board
- connect the "VCC" header to the 3.3V header on the Arduino board
Tare Button:
- connect one end to the bottom right ground header of the 6-pin section labeled ICSP on the Arduino - this step is oriented reading ICSP left to right
- connect the other end to the D4 header on the Arduino
Battery Pack/Power Switch:
- connect the negative wire(black) to the "GND" header on the Arduino
- connect the positive wire(red) to the switch header nearest the middle
- connect the other header of the switch to the "Vin" header on the Power section of the Arduino

To calibrate for in-oz, we simply used a 20g calibration weight and used the following steps:
Steps to Calibrate:
1.
Modify the arm_length in code to 1.0 — so that the display is in ounce.
2. Compile and download the code.
3. Make sure there is no weight on the load cell when the meter turns ON and tares. Move the lever arm off the loadcell.
4. Make adjustments to the constant to get correct reading.
5. Change the arm_length in code to match your meter’s arm length.
        Note — if you do not have the pin, it’s hard to know where the arm actually pushes down on the load cell.  You could start with the center of the arm.

If you have the Arduino attached, the serial log will have both the weight and torque reported.  In this case, you do not have to make the arm_length 1.0.  Just get the weight from the serial log.

Here’s an example output:
count:  36      raw: 4294873999         weight: 0.703    torque: 0.816
count:  37      raw: 4294873882         weight: 0.703    torque: 0.816
count:  38      raw: 4294873910         weight: 0.702    torque: 0.816
count:  39      raw: 4294873918         weight: 0.702    torque: 0.816
count:  40      raw: 4294873914         weight: 0.702    torque: 0.816

Note: Because we are currently in our beta test phase and we want to hear any feedback you have, we are not currently selling this. You are free to attempt this build and we will try our best to provide any support for issues that arise along the way. Any feedback is greatly appreciated either through PMs or as a comment in this thread.

Jaycub
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dslusarc
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« Reply #41 on: April 04, 2021, 12:43:04 PM »

Nice looking meter. I do not see any files on Thingiverse?
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« Reply #42 on: April 04, 2021, 01:42:52 PM »

Thank you! The files are in 24 hour cooldown as of yesterday morning because my Thingiverse account is new. If the link does not work by tonight, I will reupload and post a new link.
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« Reply #43 on: April 07, 2021, 12:17:02 AM »

New Thingiverse link: https://www.thingiverse.com/thing:4819879
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« Reply #44 on: July 28, 2021, 08:11:23 PM »


This is my first post on this forum.  I'm new to indoor FF but have been a stick & HLG modeler and R/C glider pilot since I was a kid (50 yrs).  I have always wanted to try a Penny Plane, so here I am.  I came across this thread as I was going through the content.  I am a software developer by trade and have "tinkered" with the Arduino platform so this post was of some interest to me.

Jaycub, Thank you for this!  I managed to hookup this project using an Uno and it's working fine.  I will most likely use an Adafruit ItsyBitsy 32u4 w/lipoly for the final implementation.  I set the arm length to 1.0" and I included a screenshot of the serial monitor with a 20g weight on the 100g load cell.  This is going to be fun as I can combine my modeling skills with programming & 3D printing.  

Thanks all, glad that I found this forum.

Rick
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