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and oil that does it. The oil because it makes them easy to repair!
It had been put on the backburner because you don’t get many charges of a 14 cell
pack from a car battery in a day and it had a distressing tendency to bend the
undercarriage if a landing wasn’t absolutely perfect. I tend to average one out of
ten landings perfect, six out of ten acceptable and the rest I don’t want to mention.
There followed a feverish session on ElectriCalc assessing the possibilities. I ended
up with the 3s 3600mAh LiPo pack and an Astro 05 geared swinging an 11” x 7”,
the Astro simply because I had one in stock. This doesn’t seem possible until you
look at one of the useful numbers ElectriCalc works out – W/lb.
The 14 cell version is 89 W/lb., the LiPo version is 103 W/lb. The drop from 410W
to 310W is more than made up for by the massive weight saving. Have a look at
the pictures, the 14 cell powertrain weighs 44½oz. including a receiver battery,
the LiPo 18½oz. (no receiver battery required), a reduction of 26oz.
The whole ‘plane is 35% lighter! Looking at the ‘plane pictures you can see how
eerily empty it appears with the LiPo setup.
Off to the flying field to give it a go. This can’t work, can it? It can! Just as lively
and aerobatic as before and with a lighter feel, more like the Vermont Belle. The
landings were like a butterfly on thistledown.
Well, you know what I mean, it’s always easier to make a landing look good with
a light ‘plane than a heavy one. So it flies just as well for longer and I can get more
flights in a day since charging the LiPo hardly dents the capacity of the car battery.
As the Americans say, ‘a win-win situation’.
Lessons Learned 2
LiPo conversions aren’t necessarily just a simple substitution of one battery for
another, you really need to think about the whole power train before and after.
You may be surprised at how much weight you can save.
Anyone 36 want to buy a pile of NiCds? E.F.-U.K. Velly cheap!