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Old Jan 23, 2013, 05:41 PM
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Originally Posted by Wild Deuce View Post
That's a great idea...ok 8mm on the smooth part behind the threads....thanks! When you ream a prop I'm guessing I need to rebalance...

Paul
Only if you get off on your center. If you use a drill press and a good prop boring tool, it will stay pretty good on the balance if it is already balanced. I usually balance my Durafly prop before boring, because my balancers' tapered ends go in the bore too far and hit each other before coming up agaist the prop hub after I bore out the hole. I can turn one of those ends around to balance after boring, but I've not had as good of results doing it that way because the prop is not held as secure while balancing it.
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Old Jan 23, 2013, 07:20 PM
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Puerto Rico, Carolina
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Trying to give a new look to an old friend. Not the best since I did it on a boring afternoon in a hurry. At least it looks like a different plane. I like it! Now I need to put some yellow stripes on the wings. Prop is only for the photo, it is from a HK A1 Skyraider. Ordered to try it but Amps are to high, I installed a 810Kv Turnigy G15 thinking that it would do the trick but it looks like I had to go to a lower Kv motor to be able to use it.
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Old Jan 23, 2013, 07:22 PM
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Take 2
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Old Jan 23, 2013, 07:25 PM
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that prop should have a nice sound
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Old Jan 23, 2013, 07:29 PM
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United States, FL, Hollywood
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Originally Posted by IndyMatt View Post
Did you put that on a Wattmeter and see what you are pulling?
yes i did i was pulling 41 amps on static and minuse 15-20% once its in the air you are ok
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Old Jan 23, 2013, 07:40 PM
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Originally Posted by BlinkguY View Post
that prop should have a nice sound
Yes, looks and sounds good!
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Old Jan 23, 2013, 07:43 PM
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Originally Posted by walter3rd View Post
thanks for this education. i apreciate all the guidence. i m going to run the stock setup for a bit with extra 300 prop that is on there now, but i know i want to go hobby lobby 4 blade at some point and thought the bigger esc was a must. i now see a bigger motor will be required as well. i am going to stay with 3 cell batts so that wont change. i will go to ecalc and try to figure it out there as well. watt meter is backordered! pain!
Just for fun, thought and conversation I would like to just throw out something that I have been mulling around in my small brain for those of us who like the 4 blade prop. An airframe at x amount of airspeed will require x amount of energy to maintain that speed. If you do not increase that airspeed with prop change, the aircraft should not require much more if any additional watts to fly level at x airspeed and weight, except the 4 blade will use up some more energy just overcoming it's own mass and drag. A 4 blade prop produces more thrust than a 2 blade so when you begin to climb, the airplane is not going to slow down as much, but the prop will only see it's total static thrust watt consumption if and when the weight and drag become equal to you holding it by the tail and making it pull as hard as it can. If you just flew it scale and can resist the temptation of all out climbing into outerspace and not ever coming close to approaching maximum thrust by slowly backing off of the throttle when you go into a steep or fast climb, the stock motor with say a 50 amp esc could maybe hang in there with a 4 blade prop much longer than most would have thought possible? Sure would be neat to be able to see actual loads during flying through manuevers. I believe even the real airplane could only produce maximum power for a short period of time without shortened engine life, so it would be really flying scale to have to fly so as to not burn out your engine. I am using this motor in my old Corsair with a 11x7x3 prop on a 4 cell battery. It pulls 44 amps static. I only have flown it total about 4 or 5 flights on cool days, and I haven't been especially easy on it, but so far so good. Temperature is the biggest enemy with electric motors, so when summer gets here I will be nice and gentle with her as I'm playing test pilot. Would I do this in an airplane I had to ride in? Nope : )
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Old Jan 23, 2013, 09:29 PM
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Don't wind up with a trash bag full of foam. Go get a Turnigy AE-45A for $25 and be done with this "I bet I can get away with...".

It might be nice to push the limits, except:
1. The stock ESC is almost worthless. I've had more than one die out on me without pushing its limits. I'm never going to fly another plane on those ESCs again. Pushing it to nearly 200% it's rating??
2. When it does go and that plane drills in to someone's property, or even worse, somebody, I don't ever want to have to try and rationalize why it was worth the attempt, even if I'm just talking to myself.
3. This plane is too good to risk all by itself. Remember, if the ESC goes, your RX loses power. We're not talking about a dead stick landing here. We're talking about complete loss of control.
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Old Jan 23, 2013, 09:33 PM
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Wait, never mind. I thought you were talking about running 50A through the stock ESC... It's late
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Old Jan 23, 2013, 09:39 PM
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44A static on the stock motor may be ok. In the air, that's only 40A, which is a common enough rating for a lot of similar sized motors. The pain in the butt is not knowing what it can actually handle since there are no specs.

I've been having a lot of success lately with exceed rocket 3020 motors in 3d planes. The 950kv version is rated for 44A. I also use an 860kv version to swing a larger prop. The cool part is that they are only ~$20!

I'm getting 550W+ out of them on 3s. Just food for thought in case your BL15 does go out.
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Old Jan 23, 2013, 09:49 PM
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Originally Posted by jtaylor996 View Post
Wait, never mind. I thought you were talking about running 50A through the stock ESC... It's late
i was about to let you know that
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Old Jan 23, 2013, 09:57 PM
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United States, MD, Towson
Joined Aug 2012
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what are you guys using to pad out props that are thinner than the pz ones? i put an apc prop on the jug and it was thin to the point that the nut will bottom out on the end of threads before snugging down on the motor shaft. i added about a 1/8 washer just to get it to bite to look at it but its steel, heavy and the center hole is bigger than the shaft so its not centered. again just using it for looks but what is the real solution to this? thanks, walt.
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Old Jan 24, 2013, 02:07 AM
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Uk South Wales
Joined Aug 2009
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Originally Posted by redbarn View Post
Just for fun, thought and conversation I would like to just throw out something that I have been mulling around in my small brain for those of us who like the 4 blade prop. An airframe at x amount of airspeed will require x amount of energy to maintain that speed. If you do not increase that airspeed with prop change, the aircraft should not require much more if any additional watts to fly level at x airspeed and weight, except the 4 blade will use up some more energy just overcoming it's own mass and drag. A 4 blade prop produces more thrust than a 2 blade so when you begin to climb, the airplane is not going to slow down as much, but the prop will only see it's total static thrust watt consumption if and when the weight and drag become equal to you holding it by the tail and making it pull as hard as it can. If you just flew it scale and can resist the temptation of all out climbing into outerspace and not ever coming close to approaching maximum thrust by slowly backing off of the throttle when you go into a steep or fast climb, the stock motor with say a 50 amp esc could maybe hang in there with a 4 blade prop much longer than most would have thought possible? Sure would be neat to be able to see actual loads during flying through manuevers. I believe even the real airplane could only produce maximum power for a short period of time without shortened engine life, so it would be really flying scale to have to fly so as to not burn out your engine. I am using this motor in my old Corsair with a 11x7x3 prop on a 4 cell battery. It pulls 44 amps static. I only have flown it total about 4 or 5 flights on cool days, and I haven't been especially easy on it, but so far so good. Temperature is the biggest enemy with electric motors, so when summer gets here I will be nice and gentle with her as I'm playing test pilot. Would I do this in an airplane I had to ride in? Nope : )
Your theory is right up to a point, some ESCs actually draw high amps even when not at full throttle, they switch the current on and off rapidly so sometimes amps are higher, I have several that will come down just as hot if not hotter when the plane has been flown at 1/3 all flight.

Also you have human nature to contend with, once you see how well it pulls and how quick it can go its addictive willYOU resist the temptation.......after 30 years I cant......lol

Better to spend a few bucks and get the right kit, a HL 4 blade prop can have the pitch altered so get a watt meter and measure the current then just reduce the pitch to a safe level...........peace of mind.

In the UK our insurance cover states that the plane should only be flown 'if the pilot thinks it safe to do so' in other words stuff it into someone/something and try to make a claim you would be on shaky ground with a power system that was not up to it. Lets be honest insurance companies will do anything not to pay up.......dont give them any ammo.

Most of us have done it at some time but I have too many dead stick landings with dead ESCs ( I use separate BEC in all my planes) under my belt to want any more........lol

Dave

Fly safe, have fun
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Old Jan 24, 2013, 05:20 AM
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Indianapolis, IN
Joined Oct 2010
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Originally Posted by jdm2ner View Post
yes i did i was pulling 41 amps on static and minuse 15-20% once its in the air you are ok
That sounds great, I am redoing my Jug and will be putting that motor in her with a 60A esc. I have the larger HL prop, 11", need to take a reading on 3S with the larger prop.
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Old Jan 24, 2013, 07:14 AM
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United States, MI, Grand Traverse
Joined Oct 2008
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Quote:
Originally Posted by redbarn View Post
Just for fun, thought and conversation I would like to just throw out something that I have been mulling around in my small brain for those of us who like the 4 blade prop. An airframe at x amount of airspeed will require x amount of energy to maintain that speed. If you do not increase that airspeed with prop change, the aircraft should not require much more if any additional watts to fly level at x airspeed and weight, except the 4 blade will use up some more energy just overcoming it's own mass and drag. A 4 blade prop produces more thrust than a 2 blade so when you begin to climb, the airplane is not going to slow down as much, but the prop will only see it's total static thrust watt consumption if and when the weight and drag become equal to you holding it by the tail and making it pull as hard as it can. If you just flew it scale and can resist the temptation of all out climbing into outerspace and not ever coming close to approaching maximum thrust by slowly backing off of the throttle when you go into a steep or fast climb, the stock motor with say a 50 amp esc could maybe hang in there with a 4 blade prop much longer than most would have thought possible? Sure would be neat to be able to see actual loads during flying through manuevers. I believe even the real airplane could only produce maximum power for a short period of time without shortened engine life, so it would be really flying scale to have to fly so as to not burn out your engine. I am using this motor in my old Corsair with a 11x7x3 prop on a 4 cell battery. It pulls 44 amps static. I only have flown it total about 4 or 5 flights on cool days, and I haven't been especially easy on it, but so far so good. Temperature is the biggest enemy with electric motors, so when summer gets here I will be nice and gentle with her as I'm playing test pilot. Would I do this in an airplane I had to ride in? Nope : )
This is completely untrue and comes from a common misunderstanding of how the ESC + motor work. The above scenario would work if the ESC varied the voltage to the motor to adjust throttle, however it does NOT!
A brushless ESC works by varying the on-off pulse time to the motor. Why is this important? Because when it is on it sees 100% power for the time it is on. Throttle management can not reduce this. Granted this on-off-on-off all happens at millisecond speeds. But while the it is in the "on" it will be drawing the max possible power it can. I.E. if a WOT amp reading on your motor+prop+battery combo gives you 53 amps, that is what the motor is drawing when it is "on". The reason the reading on the wattmeter goes down at less throttle is that the off cycle is longer, not that the motor is asking for less power.

Here would be what the motor sees over a given time period at low throttle:
0-0-0-53 0-0-0-53 0-0-0-53 0-0-0-53: The watt meter would read 13.25amps and 147 watts(assuming 3 cells) because that is the average amp draw. However average doesn't mean you motor didn't get the full 53 amps and 588 watts for that on part.

What throttle management does for the motor is help keep it from heating as rapidly as it has longer off time to dissipate heat, however it only delays the heating as the motor will eventually get to that 588watt temp and melt, if the ESC doesn't burn up from having to deal with the 53amps it's holding back 3/4 of the time(in the above example)!

Bottom line make sure every component in the chain is capable of handling the WOT amps/watts your system can produce then you will be safe. The only way to safely change this number is actual physical hardware changes. usually prop diameter and/or pitch.

-Brian
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