Don’t forget the nut-lock

When I bought a complete set of new legs to replace the ones whose landing skids had been bent by a crash (OTT as it turned out, as I swapped to using 8mm carbon fibre tubes from ebay), it turned out the design has changed subtly for the better: the previous model used a commbination of bolt/washer/leg or body/washer/split-washer/nut or inter-leg strut.  This made sure nothing shook loose, but all those washers were a faff, and I think were part of the reason when I could never get all 4 legs to touch a flat surface.

The new version removed all the washers, and used lock nuts for the body-to-leg bolts; the leg-to-struts bolts had nothing.  The use of lock-nuts is great – the increased strength and stability of the body was clear.  But the cross-leg joists now had nothing to stop their bolts wiggling loose.  I realized that but assumed it must be OK.

But after a couple more trampoline and lawn (!) test flights today, I could feel the frame was wobbling a bit.  Nothing dangerous, but it proved that nut-lock is needed for the bolts connecting the legs to the cross-struts.  Makes sense really given that every bolt on the body has nut-lock to stop it shaking apart.

P.S. Today’s flights were all about yaw tuning which I failed completely to improve.  I think I’ll spend the rest of the day looking for better yaw tuning gains on-line.  On the plus side, I took the drone out of the trampoline, and it flew nicely, except she drifted towards me in the 10mph ‘breeze’ that was blowing!  Luckily I do have an abort signal handler built into the code, so no damage was done to either of us.

P.P.S. She needs a name now she’s alive; I’m thinking of Phoebe (“Fee Bee”) just because I like it, but I’m open to suggestions.

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