12/13/2025 - Setting criteria and designing a base

I did some simple research to look at the type of test stand I want. I will be making a horizontal test stand, although it wouldn't be difficult to convert it into a vertical one.

I've decided that I will use either a linear rail or a linear rod for it. Other than that, I will use a beam-style load cell, as that's the one I bought. I searched for the specification online. It has to be paired with an amplifier, and for wireless transmission, we'll be using an ESP32. We will also need mounting points to the ground so that the thrust doesn't tip the test stand over.

The solid bars represent 2020 aluminium extrusions.

12/14/2025 12 AM - Mounting the load cell

I had to redo the dimensions for the load cell, as cheap Chinese components, for whatever reason do not follow the specified dimensions.

It took me quite some time to figure out how to properly mount a strain gauge-style load cell so that it produces accurate results. This is because it has 4 holes, do I mount on the first or the second? Turns out it just has to be symmetrical. This was actually deduced by looking at products such as scales that use the same load cell. They either have one each on the further end or closer end, but always symmetrical. I had no other way of knowing because of how poorly documented it is (maybe I have a bit of a skill issue with googling as well).

It was very awkward to position the load cell; it really took me a very long time to figure out where, I might still change it but for now I'm ok with it.

I also did some planning with the electronics to make the whole process faster.

The current setup can be setup as both a vertical and a horizontal stand.

12/14/2025 9 PM - Code and wiring for ESP32

Features:

• ESP32 Wi-Fi AP
• HX711 force reading
• 80 Hz binary telemetry (as HX711 can be )
• Physical arming switch
• Software arming
• Heartbeat + link-loss auto-disarm
• Single-shot ignition pulse

I pictured the wiring and it seemed simple enough so I plan to just wing it or if deemed required plan later. I made a simple sketch to see where the wires are gonna go. Instead of wasting money on a PCB I plan to use a perfboard which I have on hand. PCB will be easier to solder as it's all THT components but we can practice our soldering skills with perfboard + we get to save shipping time. The ARM cable is to check continuity and ignition is to drive the MOSFET (IRLZ44N). I will make this fully wireless by using a 18650 battery that I made earlier, that is wired with a JST connector so I only need that + LDO. Or even simpler with a power bank.

3/8/2026 - Changed the Load Cell mounting

I figured, rather than a goofy weak aluminium extrusion, why not design and manufacture a stainless steel part that can be CNC or manually machined.

I've been wanting to learn how to machine a part using a CNC/manual mill like a true machinist. At my school, we have a manual mill that I'm not sure if it's still functional, but I can try asking the technician and as long as I get a grant for the material I'm sure my teacher or technician will be willing to teach me.

This part slides on and can be attached using T nuts or tapped holes. It also can be tapped so that the loadcell fits perfectly.