Being landlocked, I don’t really have a sense of how bad a boat degrades when out on the coast. When it comes to wind speeds, however, I will certainly be making sure that the InqWind Anemometer can hold up to gale force winds. Not that I’ll be actually in the boat in such conditions, but when its hauling down the highway, it’ll very likely be seeing hurricane speeds.
The other aspect that this installment is really meant to address is corrosion. Using Hall Effect based sensors, its pretty easy to hermetically seal the electronics away from the salt air. Using ABS plastic and fusing it together with acetone slurry can pretty much eliminate corrosion concerns. On the down side, this falls into the bad philosophy of a part that can’t be serviced. With $10 worth of materials, I’m not going fret too much about that.
Unfortunately, I don’t really have a good answer for the steel bearings. Having never been around a real marine anemometer, I wonder just how they keep the salty air and spray environment out of the bearings. Any kind of seals or gaskets must induce some friction and eventually lose lubrication and fail. Do $1000 anemometers come with a limited, expected life and people just live with this expense?
Just as an Experiment
I’ve seen how marine blocks are starting to go to plastics. It’s amazing how this doesn’t reduce the price in any way. And yes, I understand, they are not ordinary plastics. I’ve also seen the examples of the ball bearing prints on Thingiverse and have tried out several of the designs. It’s pretty cool how you can print things where they are already assembled as they come off the printer, but I’ve always come away rather disappointed in their performance. A simple nylon bushing results in a far smoother bearing. Anyway, I still wanted to try making some bearings with one minor change… using high-quality ball bearings. Instead of printing the balls, a bag of several thousand ceramic, competition BB’s will only set you back about $10. I can’t even think of enough projects over my lifetime that I could use all of them, but I’ve started thinking about printing printing some of my own blocks or even a Code Zero Furler.
The point being, with no metal, and light loading, an Anemometer seems like the perfect testbed for such an experiment. With the freedom of design, I can make the races part of the housing and in this case, set the diameter to hold the electronics inside. This gives a larger bearing surface and makes for a thin, more aerodynamic housing. Besides… making the CAD model is a nice diversion and something I enjoy doing anyway.
In this first stab at a design, I’ll only test the speed sensor since these bearings get more abuse than the directional vane. As hinted this housing includes the bearings, AS5600 sensor and magnet.
First Prototype
The first one is printed in ABS. The bearings seem to work fine, but they seem a bit noisy. I hope to start testing it over the next couple of days. At the very least, it’ll be a test mule to allow me to develop the software and start evaluating what is necessary to calibrate it for speed accuracy. Toward the end, I’ll start the destructive testing and see what speeds it’ll tolerate before coming apart. If the sound levels are acceptable, but it proves to be weak, I can always bump up to some Carbon Filled, Polycarbonate plastic that has been waiting for a worthy project. It should take a lot more abuse than the ABS.
Let the games begin…
Inq