Ted shuffled out of his cave and grunted these great (and sometimes not
so great) words of knowledge:
A "BALL PARK" figure would be 100 watts of motor per pound.
I have found this works reasonably well for converting 40 size planes to
electric outrunner power.
For instance: The manufacturer states that the dry weight of the plane
is 5 - 5.5 lbs. A 500 - 600 watt outrunner, using lipos, will give
equal (sometimes better )performance to a 40 - 46 engine in the plane.
The April 2007 edition of Tower Talk, the Tower Hobbies monthly catalog, has
a really good electric motor guide on page 10 for its Ammo and Rimfire
brushless motors that matches a complete power set to the equivelant glow or
standard power system.
The chart includes motor, ESC, prop adapter, motor mount, propeller, and
recommended minimum LiPo size.
You can look up a brushless replacement for a typical Speed 370 electric
motor, a high performance upgrade for a Speed 400 electric motor, a glow
conversion setup for a .46 2-stroke, or a glow conversion setup for a .91
What was eye opening to me was comparing the price of a brushless power
setup versus a comparable 4-stroke glow setup. I paid $225 for my Saito .72
engine, and the cost of a Rimfire 42-60-480 outrunner and Silver Series 60A
ESC is only $179.99 for the pair. If I can find somebody who's giving away
6S 3200mah LiPo packs, I could save $45!!!
I would hope Great Planes or Tower Hobbies would publish this wonderful
chart online somewhere, but I hadn't seen it until I was flipping through
the Tower Talk Catalog.
Great Planes does have an online recommendation tool that is kind of handy
at their website. You punch in the weight and flying style (trainer, sport,
scale, 3D) of the model and the web application will provide you with a
Well factor in that you could share that pack between two or more
planes, and also that there is no fuel cost..and do the sums..oh..and
remember to subtract the throttle servo from the cost.
How much DOES fuel cost and how much does a .72 burn per minute?
You should get around at least 30-40 hours total flying time off a
pack..maybe as much as 100 hours.
You may go here to order the April (current) catalogue
http://www2.towerhobbies.com/cgi-bin/wtm001pt Or you can bring up the PDF
file by going to the Tower Hobbies home page (www.towerhobbies.com) and
scrolling down (left frame) until you see "Catalogues." Under "Airplane
Flyer" click on "view online." It's a PDF file so you need Adobe Reader or
anything else that will allow you to view PDF files. I haven't checked it
out but Great Planes has some comparisons here; http://tinyurl.com/39n43q
Ed Forsythe's links were good ones. The bulk of the glow conversion chart
is actually right here:
The Tower verison simply provides pricing next to all of the components that
are listed for the power system.
I scanned my copy of Tower Talk and e-mailed Red a copy of page 10.
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