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Oct 04, 2006, 03:27 PM
Thread OP
Question

difference between "electric" and "fuel" driven propellers?


I am getting into electric power more and had some questions about props.

Aside from some of the obvious visual appearances, what is the difference between an electric prop versus a fuel driven prop? Is there some unwritten rule keeping me from putting what I would call a normal propeller on an electric powered airplane? I am sure some are designed to be lighter and for slower RPM's, but when an electric motor is spinning at say 7000 RPM, what type prop do you use? Is there RPM limitations on electric props?

Thanks, Chuck.
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Oct 04, 2006, 03:29 PM
3d and EDF, some scale
MustangAce17's Avatar
post this in glow to electric conversions or pm guapoman2000,he could tell you im sure
Oct 04, 2006, 03:37 PM
Meow-meow Godwin
Full Fast's Avatar
Glow/gas props are designed to withstand the power surges of an internal combustion engine, and are stronger, heavier, and designed for (usually) larger diameter shaft mounts. Electric props are lighter, and props designated for Slow Fly use tend to have wider blades for greater efficiency at lower RPM. APC is one manufacture that offers glow, electric, and slowflyer (electric) props. GWS doesn't make glow props that I know of, but they make electric and slowflyer versions.

I don't know if there are any thrust disadvantages of using a glow prop on an electric motor. Some people like to use wooden Zinger props for scale models.
Oct 04, 2006, 03:52 PM
Registered User
As the guys say electric props are generally lighter and more efficient at relatively low revs. There's nothing stopping you using a conventional prop on an electric motor and plenty of people do just that, particularly for larger models.

But it would be a very bad idea to use an electric prop on a IC engine.

Steve
Oct 04, 2006, 04:05 PM
Thread OP
The newer electric brushless motors seem to have the same or more torque than their fuel based counterparts these days. I just didn't know if you need a specific "electric" classified prop for that purpose. I know that using an electric prop on a fuel engine will result in destruction of that prop, and I did plan on using normal "fuel" driven props for my electric purposes. I just didn't know for sure if there was something I didn't know.

Thanks guys.

Chuck
Oct 04, 2006, 04:54 PM
It is generally better to match electric prop to electric motor, but you don't have to. The most you could lose is 0-10 mph or a tiny chunk of battery life. Only if you are trying to make a speed or trying to make the airplane that stayed in the air the longest would it really matter which type of prop you'd use. Fuel props are just more durable to withstand the huge vibrations of a fuel engine.
Oct 04, 2006, 05:12 PM
Meow-meow Godwin
Full Fast's Avatar
Quote:
Originally Posted by CHAMM128
I did plan on using normal "fuel" driven props for my electric purposes.
Another thing to consider is that an IC prop may survive a ground strike and pass that impact on to the more expensive motor or gearbox shaft, where an electric-only prop would break first.

What size props and motor system are you working with? Just curious.
Oct 04, 2006, 05:27 PM
BEC
BEC
Registered User
BEC's Avatar
Karl has it pretty much nailed. For APC, which makes both types, the RPM limits for their "thin electric" props are the same as their sport series glow props. The electric props have a bunch less meat around the hub as they don't have to stand up to the pounding that comes from the continual acceleration/deceleration caused by a single-cylinder engine. So they're lighter, and they probably take a bit less power to turn at a given speed due to lower drag.

The slowfly props are for lower power, slower applications and are limited to 1/3 the RPM of the others. Data is on APC's site. (www.apcprop.com)

For the Master Airscrew family - their electric props are aimed at lower RPM applications and have thin, deeply undercambered blades. For RPMS much over about 4000 you're better off with their regular glow props than their E props - but at low speeds the MA-Es pull well.

Before there were special electric props, the Graupner Super Nylon glow props were about the best we could use.
Oct 04, 2006, 09:20 PM
Thread OP
I am working with an AXI 5320/28. Putting it in a 71 inch span A6M5 Zero. I want to put a 3 blade prop on it also, but just am not sure what size and pitch I can go with as of yet. It will be around 10 pounds.

Chuck
Oct 05, 2006, 04:12 AM
An itch?. Scratch build.
eflightray's Avatar
A search on 5320/28 should bring up plenty of information though maybe not on the three blade, worth a search.

A quick look found - https://www.rcgroups.com/forums/show...28#post6162046

also Model Motors site for the 5320/28 shows recommended two blades - http://www.modelmotors.cz/index.php?...e=28&line=GOLD

Searches can be a pain to work through, but they should give you some ball park ideas of what people are using. Even a search on 3 blade, may come up with recommended drop in size from a 2 blade.
Oct 06, 2006, 10:10 AM
Oldie but goodie
Popsflyer's Avatar
I've done a little experimenting over the years.

In electric S-400 size applications, I prefer to use glow props in the 5"-7" range over "e" designs.
In a gearbox however, larger glow props always gave me less thrust at higher amp draws vs electric SF versions.

I see no reason why a glow prop would not work effectively as long as it is being spun at rpms it was designed for. The prop does not know what it is attached to.
Oct 06, 2006, 11:32 AM
RonC911
Testing with a Himax 2025-5200 with a 5:1 gearbox showed that the grey E props are about 10%-15% more efficient than eg the black Master air screw or Yellow nylon IC props. for the same size prop. Plus I'd rather break a pro than bend a shaft.

Ron...
Oct 06, 2006, 04:01 PM
Thread OP
Is there anyone that makes 3 bladed E-props?
Oct 07, 2006, 11:40 AM
Balsa to the Wall
Gws and Vario, to name two.


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