Thursday, July 5, 2018

Does This Look Like Fun?

Here's some Germans with a drone apparently capable of carrying a human passenger over some distance. Noting that Google also has a one-man drone they're flying on Lake Mead in Nevada, I'd say that the flying cars we've been waiting for are being prototyped right now. They just don't look like cars with wings.

Seemed like so much fun that I started collecting old battery powered electric lawnmowers for the motors. Seems the ones I got all had lead-acid batteries which I already know are prohibitively heavy, but that's why they make Lithiums, right?

Some time back when I was toying with the idea of an ultralight aircraft, I noticed that the magic minimum horsepower requirement for reliable flight seemed to be about 12HP. What this suggests is that the mower motors are dismally underpowered with the 24V types putting out about 1/4HP at 3400 rpm with a 24x10 propeller. Almost enough to lift itself. The 36V motor I got was rated at 1 HP at 4000 rpm which is certainly enough to get itself off the ground but...

The 36V motor listed a part number and maker from Canton province, PRC so I checked them out. They also make motors for treadmills rated at 2-3HP 4000-4500 rpm. Now we're talking. 6X2 or 4X3 = flying. Best part is that people put treadmills up on Craigs List for free on a regular basis. All I have to do it go get them, remove the usable parts, and toss the rest.

The 24V motors will get donated to the school robotics club. The big problem now seems to be sourcing appropriate propellers at a reasonable cost. Suggestions anybody?


3 comments:

Anonymous said...

Would an IVO prop do the job? Before you gag on the prices, you might consider EAA or an kitplane owner's group like Highlander or Kitfox. I reckon you could find a used prop lying around for a good price or trade.

http://www.ivoprop.com/

https://www.eaa.org/en/eaa/eaa-chapters?gclid=Cj0KCQjwpvzZBRCbARIsACe8vyKcSPp03fzEIpYsGHSglvZrIDyyzs37qE8f8gxbgA-JT0TW37SDmCkaAtkFEALw_wcB

https://justaircraft.com/

Rick

Anonymous said...

If IVO is too large for your purposes, you might consider 3D printing a scaled down version. Or laminate the blades and build the hub - assuming the prop will be fixed pitch.

If still not your cup of tea, maybe try the model aircraft crowd. Some of those birds are quite large these days with owners building everything but the engines from scratch. Heck, maybe a helicopter model would be suitable.


Rick

Richard G. Combs said...

Re: Some time back when I was toying with the idea of an ultralight aircraft, I noticed that the magic minimum horsepower requirement for reliable flight seemed to be about 12HP.

I am not an engineer (IANAE), but it seems to me that in a traditional aircraft, much of the lift depends on the area and profile of the wings. Does your horsepower requirement really translate directly to a wingless (drone or helicopter) configuration?