The Stupid Car failed it’s MOT on knackered bushes in the shocks and the Panhard rod. I knew this day was coming as they looked pretty ropy last year when I took this photo This is not something I’d ever done before, so new stuff to learn and maybe an excuse for new tools! First port of call was the Spax website to see if they had suitable bushes. TL;DR was “We don’t support old shocks, want to buy some new ones?
My plane currently weighs 235g (minus a few grammes of control surface connections), but it has a weight problem. I used FreeCAD to design and print a simple balance frame. (I should have put a nice chamfer on the joints) I then removed the battery (27g 600mAh 2S LiPo) and put some scales under the tail. They read 25g. In order to get the plane to balance, I’d need to place the battery somewhere about 300mm in front of the centre of gravity.
It’s A Plane When I was a teenager, I used to belong to the Chester Model Flying Club (which now appears to be defunct :( ) and I flew electric powered gliders of about 2M wingspan. Typically a balsa framework, with a 540 motor and a 6 cell NiCad battery. Power (& skill) were marginal, weight was high, but I had fun. I’ve always hankered getting back into it, partly becuase my route to and from work can go via the Nomansland Common where there are facilities to fly planes.
After my last post I drank some more wine, read the comments it generated and got down to some jolly good proper thinking. I realised that I was distracting myself with standard deviation and such like, and a more empirical approach may work. The rough pseudo code is for each log entry that isn't filtered out by temp/RPM etc Find the AFR in the future by doing a bilinear interpolation on a delay table Find the actual VE by doing a bilinear interpolation on this record Find the target AFR by doing a bilinear interpolation on this record Work out how far out of whack the actual AFR is For each of the 4 cells involved in the current reading, add a weighted adjustment record depending on where the bilinear interpolation lands for each cell that has more adjustment records than the minimum number of hits required Calculate a weighted average adjustment to apply to the cell create a new VE table by applying the adjustments to the base table And it seems to work.
I’ve been doing more fiddling with log file and VE analysis, and I’m a little stumped as to where to go with it next. A Bit Of Background VE analysis is basically looking at what the air/fuel ratio the car is running at at a specific load/speed, comparing that to what we think it should be, and then fiddling with the fueling to get it closer to the ideal. The authors of the original Megasquirt firmware published a PDF that went in the basic maths of this.