"Phil" wrote in message
ps.com...


Very interesting. It doesn't mention how long it takes to charge the
batteries.

It looks like they're using an Etek motor which was increasingly common in
the superheavyweight Battlebots and Robot Wars. Real monsters. (Got
thumped by 'em a few times.) For perspective, I used four smaller
power-chair motors to propel a 250-pound machine that could pull my jeep,
but heating became a real problem. If the motor and batteries are cooled
properly they'll operate a lot longer on a charge. I don't think you'd get
two hours out of a charge, though. I used a total of 120 C-cell nicads
bundled in 6 clusters of 20 wired serial, with the clusters in parallel, and
got about 30 minutes with no additional load on the frame. That's the
equivalent of two 20-pound sealed lead acid lawnmower batteries. Also, the
runtime could drop to 5 minutes if the motors operated at full stall.

Depending on the battery types they can charge pretty fast. I can't
remember the figure but it was hours or less. What you'd need to do for a
day of flying is have one or two sets charging while you're flying.

The other factor is the discharge characteristics of the batteries; some
such as the $70 Hawker 12v SLAs will carry full charge and then crap out all
at once, whereas start at 100% and gradually decrease. Lithium Ion and
later change the metric quite a bit, but you still have to be able to
predict when and how your power will drop.

The weight for these batteries and hardware was about 40 pounds total, IIRC.

An electic motor should be more reliable than a piston engine. But I
wonder what the life span of the batteries would be.

If they're treated well and conditioned properly they should last quite
awhile, but they certainly won't last as long as a Rotax. It would be a joy
not to have an internal combustion engine roaring behind your head,
though....

Weird. Except for the ultralight itself, which I sold many years ago, I
have all of the components necessary to build a couple of these.

-c