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Post by patmatgal on Oct 23, 2009 19:16:31 GMT 1
Used a GWS 10X6 on all 10 fights and not the Trojan prop (Trojan draws crazy amps, pulls the plane like all get out and is too much fun but will save it for limited engagements) OK so I figure now I gotta prop down. Would it be correct to think of only needing to reduce the pitch? (like go to a 10X5 or 10X4) Or will I only need to reduce the diameter and try something like a 9X6? Or will I have to reduce both diameter and pitch and maybe go to a 9X5? Any links to sites that help explain the relationship of changing diameter & pitch on a prop would be most helpful. So as to stay on topic, the heads Up RC 450 Sport seems to be working fine as can be. Bolted right onto the motor mount I had on the Super Cub and at half the price of the E Flite 450 I'm a happy camper.
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Post by flydiver on Oct 23, 2009 19:56:13 GMT 1
Like I said, read the HU recommendations. He's done your homework.
The concept is simple-more diameter pulls more amps, more pitch pulls more amps, fatter blades pull more amps.
Blade surface area (diameter and width) mostly equates to thrust. Pitch is speed.
The individual motor has a narrow operating band for best efficiency.
Prop design is all over the map and there is no good way to figure out efficiency without getting a wattmeter (and a thrust stand, temp meter, and tachometer) and doing the work yourself.
Just think all the possible permutations of prop sizes/types x motors----Arrrgh!
You are also running up against one of the limitations of cheaper motors-they are often less efficient. This means more of your battery is wasted not turning amps into go. This is a function of wire type/size, stator material and design, magnet quality, bearing quality, and assembly.
Towerpro motors are very much in this category. They are cheap, they work, and their efficiency is not any better than a brushed motor for the most part. Suppos are made better but are only a cut above TP for efficiency. I put Turnigy is the same class. Eflites are noticeably better but cost a lot more. Next step up is Axi or Hacker but you really pay for those. Clones, are merely that, clones. They absolutely do not use the same quality in materials that does make a difference in performance and efficiency.
So it goes. When you start out and all your motors tend to die a horrible death an expensive motor does not seem like a good idea and you can't tell the difference anyway. Now you are getting to the stage you can. Makes choices more challenging.
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Post by patmatgal on Oct 23, 2009 23:50:00 GMT 1
Hmm..
Challenging choices, no kidding. And I got into this hobby with a "Gee, this looks like it could be fun and not too complicated" LOL
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Post by flydiver on Oct 24, 2009 3:26:47 GMT 1
I have a buddy put a new motor on a new plane. He brought over a handful of props supposedly in the size appropriate for that motor. We hooked it up to a wattmeter and then a small fairly accurate scale. We started running props. First thing we noticed was the manuf. specs were garbage (common). One GWS DD was noticeably more efficient in terms of thrust/amps and didn't tax the motor. At the field he didn't like the way it flew. He needed a bit more throttle to get it up to speed. So he put on an APC SF and flies around a less efficient prop at half throttle. He cannot get a handle that more throttle on a more efficient setup is possibly better that less throttle on a less efficient setup.
Bottom line, don't over prop your motor unless you don't mind replacing burned out motors. After that it's up to you. The objective part is the motor's capability. The subjective is the way it flies. That's up to you.
BTW-I've never understood throwing more and more motor at a draggy airframe. Get a jet. ;D
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