Glow-engine powered generator?

[rc_sjo]

So i'm looking to design me a new flight box. I had a moment of inspiration (as i'm moving mainly to electric models in the future) to create a glow-engine generator to sit in the new flight box!

So i'm invisaging a small glow engine from a car (for the pull-start mainly). Probably something .15ci size (should be adequate). I only need 5 amps at 12v. It should be able to produce this at idle (although it wont have enough torque to sustain that, no doubt, so some speed will be required)..

So i'm thinking: engine, alternator/dynamo, regulator. What i'm wondering though is how to do the alternator? I've looked at motorcycle ones, but they tend to be internal to the engine/transmission and not seperate units. Obviously I want it as small as possible.

I wonder if it'd be possible to just use say a 540 style motor with an external regulator? I don't know much about alternators unfortunately.


... but perhaps you guys have some ideas? :cool:

Thanks :D

[vintage1]

Sure.

a 15 sized engine will do about what..150 watts at what..10k RPM?

a 540 motor should produce about 20-35v at 10K RPM, falling a lot under load though. You might get 10-15A out of it.


You won't get that power out at idle though..need to be up around 6K rpm at least I'd say.


Feed the motor to a single power diode rated at 20A or more, and a 25v 1000uF capacitor or simlar, and apply to a 12V 5A regulator bolted to a large heatsink! Or simply use a 12v gel cell, and make this the 'charger'.

A brushless motor with a 6 diode 3 phase rectifier makes a better alternative to the 540 motor.

[phil_g]

I bought an 850 watt chinese petrol genny for £30 brand new from B&Q, it runs for hours on a gallon of 50:1 premix and has 240v & 12v outputs. Wouldnt a glow genny gobble up juice & cost a mint to run? What I'm getting at is for £30 is it worth it? :)
Phil

[rc_sjo]

vintage1- yeah, a brushless motor would be the superior idea, less wear too!! I may use some kind of 'throttle jacker' to up the engine speed when under load, but I feel I may need some kind of large cap to handle the transient.. i'll get my calculator out!

phil_g- if the project was about practicality and cost-effectiveness i'd definately agree, but the idea behind this is to use what is commonly used in the hobby anyway (now both glow engines and brushless motors, and the fuel obviously).. it's a 'fun/cool' project.. but yeah, fuel economy does concern me a bit.. ha ha!

[phil_g]

yeah, a brushless motor would be the superior idea,
And smoother since you've 3 overlapping phases...
Must admit a really tiny genny might be handy sometimes...
Phil

[vintage1]

And smoother since you've 3 overlapping phases...
Must admit a really tiny genny might be handy sometimes...
Phil
speed 540 is a three phase motor too, with overlapping phases..it just uses 'mechanical' diodes...

[ebill3]

Certainly, not practical for sjo's project, but the Sullivan alternators (http://www.sullivanuav.com/home.html) are interesting.

Bill

[andrew b]

But how do you intend to cool the glow motor? Just sat running stationary it's going to get as hot a h**l and seize up pronto

[Dan Baldwin]

But how do you intend to cool the glow motor? Just sat running stationary it's going to get as hot a h**l and seize up pronto

A small prop attached to the shaft before the generator and perhaps some shrowding to direct all of the air around the motor should take care of the heat.

Dan

[phil_g]

But how do you intend to cool the glow motor? Just sat running stationary it's going to get as hot a h**l and seize up pronto

i'm invisaging a small glow engine from a car

Model car motors have huge finned heatsinks & are ok with no draft...

I'm coming round to the idea of a pocket generator... :rolleyes:

[rc_sjo]

I was contemplating modifying the heatsink/head and fitting perhaps a CPU cooler and fan arrangement onto it.. they can get rid of 150W of heat quite effectively!

If necessary, of course.. a brushless fan with ducting may suffice.

[rc_sjo]

I was chatting to a friend today and ultimately I think it will be too noisy with a 2-stroke engine. Sure, big generators are quiet because they run at a comparatively low speed! A small engine running at 10,000rpm is never, ever gonna be quiet, whatever I do to it and obviously people want it nice and relaxing at the flying field..

I may investigate using a 4-stroke engine for this! That'll definately require additional cooling..

[vintage1]

Get an old briggs and stratton powered ride on lawnmower and remove the cutter deck: they hace a 12v battery on board, and they will charge it.

You can use it to haul a trailer full of planes around as well.

If you leave the cutter deck on, you can even mow the strip.
:eek:

[pilotpete2]

Vintage,
I think you deserves a pint of Guinness for that idea :cool:
Actually, anything cold would be real nice about now :)
Pete