As the new test rig is working, I’m going to swap the quad blades from the slightly damaged set back to nigh-on perfect ones. Nigh-on because they need balancing. So I thought I’d share with you how I’m doing it, as it’s now taking just a minute or two per blade (compared to when I did my first few, which took up to 20 minutes each and, as it turned out, still weren’t actually balanced as well as they could be).
- a dremel drill (which I already had)
- an abrasive disk for it
- protective eye glasses – seriously – a carbon or metal shard in your eyes is uncomfortable at best, blinding at worst – it’s not worth risking – I just use my Oakleys from skiing and they work perfectly.
- a magnetic prop balancer
The key part is the balancer itself. The axle has sharp ends and is attached by super strong neodymium magnets at both ends; this gives virtually zero friction, and yet makes it simple to remove the blade from the jig for sanding.
Even the subtlest blade imbalance results in the propeller rotating until one blade taps on the work surface. Once you’re sure which blade it is, then you can use the dremel to take a small amount from the underside of the heavier blade. Then wipe it with a slightly damp cloth to remove the dust, dry it, pop it back on the balancer and check again.
You’ll soon develop a gut feel for how much sanding needs doing depending on how quickly one side of the blade hits the floor.
An here’s what you end up with:
One final thought: this time when I attach the new blades to the drone, I’ll be using nut-lock – although the blades have never unscrewed themselves (except when scrapping with the gravel), I’d hate for my first experience of it to be when they are 10m above my head!
Another afterthought: I’ve just balanced the stockpile of 10 blades I’d bought in preparation for many more crashes. They’re all the same as the above picture, all sourced from China originally, although bought from ebay, quadcopters.co.uk and flyduino.net, yet each has subtle differences: some have been pre-balanced – you can spot this as one of the wings has signs of sanding; others have had the axles sanded too to ensure they are completely flat (a good thing). So look carefully at any you have to make sure they are all the same once you’ve done balancing them.