So, the other day, I got this idea stuck in my head. I wanted to figure out how to make a sort of “pound of lift calculator.” Not some fancy software, mind you, just a way to get a real feel for how much stuff, like, a propeller or a small ducted fan could actually lift. You see these things in projects, and I just got curious about the actual numbers in pounds.
My first thought was, “This can’t be too hard, right?” I had an old digital kitchen scale lying around. The kind you use for baking. I figured I could just point a motor with a propeller downwards onto the scale and see what it reads. Simple.
Well, that was the theory. I rigged up a little motor – one of those brushless ones for RC planes – with a propeller. I tried holding it over the scale, and then I tried to build a quick, wobbly stand out of some cardboard. It was a bit of a mess. The airflow from the propeller was blowing all over the place, and I wasn’t sure if the scale was measuring the thrust or just the air pushing down on its surface. The numbers were jumping around like crazy. Definitely not a reliable calculator at that point.
Getting a Bit More Serious
Okay, so Plan A was a bust. I realized I needed something more stable and a way to direct the force properly. I rummaged through my garage and found some scraps of wood and a few L-brackets. My goal was to build a small, sturdy frame that could hold the motor pointing straight down, with the propeller spinning just above the scale, but without the frame itself resting on the scale’s weighing part.
Here’s what I did:
- I built a little platform, sort of like a mini table, tall enough for the kitchen scale to slide underneath.
- Then, I mounted the motor upside down, securely fastened to the underside of this platform’s top.
- The propeller was now spinning in the space between the platform and where the scale would sit.
The idea was that the motor would try to lift the platform, but since the platform was heavy and stable (well, stable-ish after a few adjustments), the main force measured by the scale placed under the motor (but not touching the propwash directly) would be the reaction force, or effectively, the lift generated if the motor was trying to pull something up. Or, if I inverted the thinking, if the motor pushed air down, and the scale was measuring the whole rig, an increase in weight when the motor was off versus a decrease when it was on could also work. I actually tried it both ways – measuring the push on a separate plate on the scale and measuring the reduction in weight of the test stand itself.
This setup was a bit better. The readings were more consistent. I made sure the platform itself wasn’t wiggling too much and that the air from the propeller had a clear path downwards without hitting the sides of the scale or creating weird pressure zones.
The “Calculator” Takes Shape
So, how did this become a “calculator”? Well, once I had a setup that gave me somewhat trustworthy numbers, I started playing with different power levels for the motor. I’d set the throttle to, say, 25%, let it stabilize, and note down the reading on the scale in grams (my scale did grams, which I then mentally converted to pounds, or you could just use an online converter later). Then 50%, 75%, and full blast (which was a bit scary, not gonna lie, things vibrated a lot).
I jotted all these down in a notebook:
- Throttle Percentage vs. Grams of “Lift” (or Thrust)
After a few runs with a specific motor and propeller combination, I had a little table of values. That table, for me, became the “pound of lift calculator” for that specific setup. If I wanted to know how much lift I could expect at, say, 60% throttle, I could look at my table and get a pretty good estimate. It wasn’t super precise, like some engineering formula, but it was real-world data from my own hands-on test.
I even tried a couple of different propellers to see how much difference they made. It was quite interesting to see the numbers change. Some props gave more thrust at lower power, others really shone at high RPMs.
What I Figured Out
This whole exercise wasn’t about building the world’s most accurate thrust stand. It was more about getting a practical understanding. And I learned a few things:
- Direct measurement is tricky. Airflow is a mischievous thing.
- A stable test rig is super important. Any wobbles or loose parts, and your readings are junk.
- Even a simple kitchen scale can be useful if you’re a bit clever about how you use it.
- Making a little chart of your own findings is incredibly satisfying. It’s your data.
So yeah, that was my journey into making a very basic, very hands-on “pound of lift calculator.” It’s more of a method and a set of notes than a device, but it works for my tinkering needs. It was a fun little project, and I actually got some useful numbers out of it for some other little gadgets I’m thinking of building.