A note on developing products, even simple ones.

Lesson Learned

As I write, I recall making a tool to pull tappet guides in Lister Clones, some of the Erectors would hammer them in with very tight clearances, so I designed a “Tappet Jack” to help pull them.  After I had sold a decent number of them, I received some complaints which led to some emails inquiring about the diameter of the tappet shoulder that the tool grabbed onto.  What were the tolerances of tappet shoulder diameter? 

The reply was a little difficult for the Western mind to gasp, there was no spec, and every Erector (Builder) decided what was best for him.  My tool was made after measuring about 50 tappet guides, but they were all made by one manufacturer. 

Today’s Lesson

I bought some LilyGo T beam Lora radios to play with and quickly decided I needed some cases for the field.  I ordered a few off Etsy and was somewhat surprised as to how nice they looked. I knew there was no way I’d make anything close.

While stuffing the radio into the case I noted I needed to trim a few pins on the bottom side of the circuit board to get the board in the case and the lid on. The buttons didn’t always work, I needed the radio in the field the next day, so I’d live with it and use the app on the phone to make adjustments.  The next day, the radio made a 3-foot drop to the ground and the display broke.  It didn’t help my testing, but other gear wasn’t working, so I was out of business for the entire Cowiche trip.

Some spare parts arrived, it’s time to look at the T-Beams again.

Tonight I opened the case and removed the broken display, I soldered in a new display and all is good. I noted the case cover was hard on the delicate display, with no gap to protect it from a drop.  I looked at the design and noted that in order for the buttons and clearances to be right, the circuit board had to sit dead flat on the upper surface of the case. In no way was this was going to happen without some adjustments.

The first one was the need to make an indent so the pins protruding below the circuit board for the SMA antenna mount would have a place to nest.  I got out the dremel and easily made a pocket, and reassembled it. The board still rocked back and forth and resisted my efforts to seat it.

I turned the board over and noticed two solder connections that needed similar indents.  A little more dremel work took care of that, but still, the board rocked and would not snug up to the indented surface it was designed to index on.

At this point, even that solder battery connection had a dremel-made pocket to drop into.

Another test fit  

I was running out of ideas, but there it was, the circuit board rocking, rocking, rocking. I painted the bottom of the 18650 battery with some fingernail polish and quickly dropped it back in the case, and when I pulled it back out, there was polish in the bottom of the case, no clearance for a circuit board with the battery on the bottom, which is the standard. 

I got the Dremel out again and carved a groove in the bottom center of the case to make room for the battery, it was all making perfect sense now, the creator used a CAD drawing of the Tbeam to design the case. It’s possible he never put a working T beam in the case. 

A total of four areas prevented the board from indexing in its proper place.  Beware, with this condition, it’s very easy to destroy the buttons when trying to install the board, and as I mentioned, it’s pretty easy to mess up the display, you need proper clearance for it. 

But there’s one more thing you need to fix.

there’s nothing in the design to hold the board in its proper place, if you were to drop it and it landed with the display down, the circuit board would hammer into the cover and most likely break the display. For this, I added some double back take to build a wedge cushion between the cover and the board.

With all the adjustments made, the buttons work and nothing binds.  Still, the case is far nicer than anything I could build, this creator is a whiz with the 3D printer, and the plastic he used is high-quality stuff, he just needs to work with his hands on the real thing.

The Lilygo T-Beam Radio

It’s an amazing product, but why would you ever put an antenna in the middle, and why allow a drop to stress the circuit board in the area of the SMA antenna connector?  Lilygo has smarter designs now, and so do others, but these radios are cheap and full of fun and learning.

George B.



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6 Responses to A note on developing products, even simple ones.

  1. Bill Rogers says:

    George, it’s good to see you posting again. Hope all is well.

    “…cheap and full of fun and learning.” I’ve always liked the way you think! Hey at least you didn’t have to scrap it and start over. Any custom fab job that doesn’t result in some level of destruction is a success in my book. All the best.

    • George B. says:

      Good to hear from you Bill. With the help of some friends, I’m hoping we can establish a mesh network to haul data, and a secondary use for Meshtastic is sharing positions and text in the back Country. If you have some new stories, I’d love to hear them.

  2. Bill Rogers says:

    One of the items on my longterm to-do list was to figure some way to establish comms with neighbors in a post-crisis situation. It has to be simple and easy to use. The best thing I could come up with is the Baofeng UV5R. You ever messed around with them? Absolutely amazing little radios. They’re under $20 each now, easy to “fix,” and a pair of them can be configured as a repeater. I got 5 of them programmed up and ready to hand out if it ever becomes necessary.

    • George B. says:

      Thanks for your comment, no doubt those radios are good for an emergency, but the mesh network I’m putting up is fully encrypted, and very difficult for anyone to locate. It’s good for sending messages and you can send sensor data, GPS locations, weather data etc. There is a very serious version of the Military’s ATAK that interfaces into Meshtastic, some suggest it’s a great tool for search and rescue and more, but it’s likely overkill for me. My use is in the back country where there’s no cell phone signal. A well placed router on a mountain side can cover hundreds of square miles. I’m working on this project with John Gange, he works for a company that builds automated equipment for the food industry, and he’s very current in IoT, Industrial radios, etc., so he is working the smart end of this project that uses MQTT to store data from our private mesh. Open door alarms can trigger emails along with a message via text, or even spawn a message via the SMS gateway that a lot of ARPS use. I think he’s using the Raspberry Pi for the MQTT interface.

      I have the dumb end of this project, and I think I have the skills for it. I will build the KISS repeater/router nodes for our private mesh, they will handle sub zero temperatures, and will run for one month without needing the solar panel input for battery charging. In the case of the Cowiche Mountains, we can move state of charge data from solar power plants at cabin sites into a spread sheet via the mesh. We can then trigger on alarm thresholds and more. our internet portal is 25 miles away, and a clear line of site, it is here where a mesh node publishes into MQTT.

      I have a tech license, and you can use the 915mhz spectrum as a ham, but you can’t encrypt anything, I think this gets a little sticky, because you should really spell things out so people can’t charge it’s encrypted? Example H83, that would be good for me, but do you need to be more verbose and spell out it’s humidity?

      The down side is there is no video or audio, it’s all been given up to operate at low power and operate over some pretty good distances.

  3. George, it’s wonderful to know you’re publishing again. MESH technology is making its way into consumer products now. Encryption adds a nice level of security but isn’t allowed on ham bands. Digital modes bring a lot more security than analog. But maybe the key is to operate off the ham bands on spectrum that isn’t so restrictive?

    • George B. says:

      Great to hear from you Russell! My attraction to ham radio was in hauling data, I did spend some money on 2 Meter radios, and I’ve paid attention to APRS, and more. There are still a lot of places with no cell service, and this mesh network can function as a primary communication tool in our mountains, one of the things it might have over FRS, 2 meter, and others is extremely low power requirements and the ability to forward only the traffic it knows. This helps keep the power requirements low, and you can share your GPS location with node members VS the world. When I was looking at the HAM rules, it looked like you really needed to define everything you sent to keep from having someone claim you were using a form of encryption. The way I interpreted it, I’d be sending more data to define the data than the data string itself. I’m not sure that’s much of a problem, but in addition, meshtastic has a lot of interesting features beyond the solid encryption system. My favorite radio so far is the RAK4631, I think the repeater router I put together will easily run for a month with no sun, but a number of our nodes will be in cabins with existing solar PV power plants, so we can use radios less efficient there.

      Some of the things I’ve seen recently in the deep woods were a bit alarming. During all the corvid stuff, the DNR made it known you couldn’t be on their property. Most of the people who would visit utterpower would think that is perhaps the best possible to place to hang out during a time like that, somewhere in the deep outdoors alone, but no! For those who did not comply, we weren’t about to advertise our position.

      Another thing that annoyed me, the government shut down thousands of acres of property as no fly zones including my mountain property. I was not able to hover my drone at camera tripod height off the ground. It was a radicicolous restriction, and it helped ruin a one week stay at Cowiche.

      I really think about half the country expects the government to become even more intrusive, and maybe we’ll need an encrypted network. With the MQTT portals, we can get messages out of the back country to any cell phone. Most younger people prefer a text over a voice call, the bandwidth limitations may not be much of an issue.

      All the best to you Russell!


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