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Old May 11, 2012, 02:31 PM
RPoe
Joined Feb 2010
32 Posts
Question
Turnigy C3542-1250

I honestly tried to find the answer to my question in various forums and saved threads but could not. Maybe a newbie question, but....

I bought a L4-Grasshopper, 72" wingspan. The manual (terrible!) says the weight is 2000-2100g (4+ lbs). I had to put about 4 oz of weight in the nose. The manual suggested using a motor of "3548-890KW" (copied straight from the manual). I asked a club member to help and he ordered a Turnigy C3542-1250 and a thin plastic prop with NO numbers on it. It measures 10.5 inches but don't know the pitch. He also ordered a HKing ESC that has the number "50" on it, with "15V/4S LiPo, 6-12 NiMH and 2 amp MAX" also written on it. He also bought a Zippy 3000mah 3s 11.1v battery to power everything.

The plane would not get off the ground and I had no other prop to test with it.

MY QUESTION: Could someone suggest what numbers this motor should produce (just a range) so I can try to find another plane that would be a good fit for it? I was looking at a Super Cub 25e ARF by E-flite (EFL4625). Horizon Hobby recommends an EFlite Power 25 BL motor with a 3200mah 4s LiPo battery and a 60amp ESC. Would my setup (assuming a proper prop) power this plane? It is 5 lbs, 68" wingspan.

If I haven't provided enough info, could anyone tell me if a Turnigy 35 can produce the same or better numbers than a Power 25, assuming similar battery, ESC, prop setups?

Thank you so much for any help you can give - I'm afraid I should not have trusted the club member or if the manual specs were just badly off.

Russell
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Last edited by SuzieQ; May 11, 2012 at 02:34 PM. Reason: typo
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Old May 11, 2012, 09:02 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,844 Posts
Quote:
Originally Posted by SuzieQ View Post
I honestly tried to find the anstwer to my question in various forums and saved threads but could not. Maybe a newbie question, but....

I bought a L4-Grasshopper, 72" wingspan. The manual (terrible!) says the weight is 2000-2100g (4+ lbs). I had to put about 4 oz of weight in the nose. The manual suggested using a motor of "3548-890KW" (copied straight from the manual).
The 3548 is the O.D. and length of motor body, and if you did not know it, the 890 Kv (KW is a mistake for Kv) means that it will turn 890 RPM for each volt of of battery voltage. Here is a typical motor of the same size and quality (35mm x 48mm) and with a 900 Kv (minor difference).

http://www.headsuprc.com/servlet/the...h-09%29/Detail

If you look at the prop testing data there you can see that it would have plenty of power on 3S to fly your plane, a good prop would be an APC 13 x 8 Thin Electric.

Your 64 oz. plane will just fly with about 22 oz. of thrust, it will fly very well with 32 oz. of thrust, and it will be a very sporty flyer with 64 oz. or more of thrust. Those number are thrust to weight ratios of 0.33:1, 0.5:1, and 1:1 respectively.

Quote:
I asked a club member to help and he ordered a Turnigy C3542-1250 and a thin plastic prop with NO numbers on it. It measures 10.5 inches but don't know the pitch.
I can't find any test data for a Turnigy C3542-1250, here is some for a C3542-1000 (lower Kv):

http://www.flybrushless.com/motor/view/478

But bottom line is that the shorter (42mm versus 48mm) motor and the higher Kv (1250 versus 900) both combine to make that a less powerful motor and also one that needed to use a smaller prop. So the motor and prop combo are simply less powerful than what was recommended.

Quote:
He also ordered a HKing ESC that has the number "50" on it, with "15V/4S LiPo, 6-12 NiMH and 2 amp MAX" also written on it. He also bought a Zippy 3000mah 3s 11.1v battery to power everything.
That is a 50A max rated ESC, it is adequate for the motor we have been talking about here. You only want to use an ESC at about 75% of it's rated value so that is good up to about 38A or so. It would be OK with occasional bursts up an little higher than 38A but it would not be a good idea

Quote:
The plane would not get off the ground and I had no other prop to test with it.
And I don't suppose you had a watt meter or have any idea as to how much current the motor was drawing, do you? That would answer a lot of questions.

But is sounds like you have too small a motor, too high a Kv, and too small a prop. It is sort of unusual to find props without any markings at all on them, you really should pick up a prop of a known size and do some static run ups (checking for motor heating or over heating) to see what props you might be able to use with that. Was it this motor here:

http://www.hobbyking.com/hobbyking/s...50kv_700W.html

If so, a 10 x 6 or 11 x 5 would be good props to try on it. In the reviews there there is mention of that motor using an 11 x 7 on 3S so that may be worth trying too.

Quote:
MY QUESTION: Could someone suggest what numbers this motor should produce (just a range) so I can try to find another plane that would be a good fit for it? I was looking at a Super Cub 25e ARF by E-flite (EFL4625). Horizon Hobby recommends an EFlite Power 25 BL motor with a 3200mah 4s LiPo battery and a 60amp ESC. Would my setup (assuming a proper prop) power this plane? It is 5 lbs, 68" wingspan.
If it is the motor above it looks like it can handle an input of about 400W continuous, the 700W figure there is crazy wrong, a momentary peak just before it burns up and not usable power.

Quote:
If I haven't provided enough info, could anyone tell me if a Turnigy 35 can produce the same or better numbers than a Power 25, assuming similar battery, ESC, prop setups?

Thank you so much for any help you can give - I'm afraid I should not have trusted the club member or if the manual specs were just badly off.

Russell
We really need to get the motor you have identified better and maybe we can get some inputs from people that have used it. There is no such motor as a "Turnigy 35" and the Power 25 name is used for a number of different motors so if you can identify which Power 25 you mean, that would help.

Jack
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Old May 12, 2012, 10:49 AM
RPoe
Joined Feb 2010
32 Posts
Thank you very much for all the information you've provided. This is going to help me.

And no, I don't have a wattmeter but have been told I need to get one if I'm going to go electric, so I plan to buy one. I plan to ask a couple more questions at a later time, like what kind of wattmeter you guys use and like, and I have another electric motor I know nothing about I want to ask about - later.

Sorry, but I can't tell you anything more about the Turnigy motor except what was printed on the motor - "C3542-1250" and I don't think I have the receipt.

I'm certainly not in a position to disagree, but I thought EFlite's "Power XX" nomenclature only identified 1 motor. I have a Power46 powering a P51 and to my knowledge that model # identifies only 1 "kind" or power level of motor EFlite makes. That's why I listed the Power25, thinking it was only 1 kind of motor in it's "category". But, I think buying a wattmeter and some different props, and then testing the motor, will help me determine the motor numbers and thereby find a plane that will "fit" the motor.

Again, thanks for your help!
Russell
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Old May 12, 2012, 10:52 AM
Registered User
Canada
Joined Nov 2000
6,951 Posts
This Motor?
http://www.hobbyking.com/hobbyking/s...50Kv_600W.html
On the plus side it was only $15.
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Old May 12, 2012, 11:19 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,844 Posts
Quote:
Originally Posted by SuzieQ View Post
Thank you very much for all the information you've provided. This is going to help me.

And no, I don't have a wattmeter but have been told I need to get one if I'm going to go electric, so I plan to buy one. I plan to ask a couple more questions at a later time, like what kind of wattmeter you guys use and like, and I have another electric motor I know nothing about I want to ask about - later.

Sorry, but I can't tell you anything more about the Turnigy motor except what was printed on the motor - "C3542-1250" and I don't think I have the receipt.
What color is it? Isit the same as the links we've posted and asked about? Does it have square or rounded shoulders on the casing? Do you have a camera? Can you weigh it?

If you can weight it you can assume that it will handle 3 Watts of input power for each gram of motor weight. Then you can look for a prop that draws enough current to get that input power.

On a 3S at a full load the battery voltage will be down around 10.5V or so. So if your 150 gram/450W motor is drawing 8A at full throttle with a 10 x 5 prop, you can go to a bigger prop. Why? Because 8A at 11V is only 88W. To get the full 300W in you want a prop that pulls 30A at 10V.

Believe me, there is no real substitute for know what motor that is. And there no easy answers without a watt meter. Read about watt meters here:

http://www.rcgroups.com/forums/showthread.php?t=1650325

The price on that one is about as good as it gets. That is a $30 copy of a $50 or so Watts Up meter. Either that or the Chinaman that makes them for Watts Up is re-branding them and undercutting the American guy that put him in business.

Quote:
I'm certainly not in a position to disagree, but I thought EFlite's "Power XX" nomenclature only identified 1 motor. I have a Power46 powering a P51 and to my knowledge that model # identifies only 1 "kind" or power level of motor EFlite makes. That's why I listed the Power25, thinking it was only 1 kind of motor in it's "category". But, I think buying a wattmeter and some different props, and then testing the motor, will help me determine the motor numbers and thereby find a plane that will "fit" the motor.

Again, thanks for your help!
Russell
You might be right about the exact term "Power 25", but there are all kinds of "25" motors out there now and some are very close to the same, Monster Power 25, Power Up 25, etc...

And you are right on the money as to what testing with a watt meter will do for you.

Jack
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Old May 13, 2012, 02:27 PM
RPoe
Joined Feb 2010
32 Posts
It is not the one in the link. It has a orangish-brass color body with 4 curved "pillars" that run from the body to the prop connection. I've attached 2 pics of it and tried to show the length of the prop I'm using with a ruler...

I do appreciate the help and I'm sorry I can't provide more info - I don't have anything but a bathroom scale to weigh it - maybe one of my redneck neighbors has a scale that would work - nudge nudge wink wink say no mor'....

I think I'll buy the watt meter you've suggested, and print off the info you've given me and find a way to weigh it, and go from there.

And next time I ask a question I'll try to have all the info needed!!

Russell
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Old May 13, 2012, 05:23 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,844 Posts
That is a motor made by a company called XYH if I have it identified right. It was sold in that color as a Turnigy and in other colors by other dealers. Here is another example of it with some better specs and they mention it as being the same as the Turnigy too:

http://www.giantshark.co.uk/xyh3542-...-p-403280.html

It is a 132 gram motor and should handle about 400 Watts input by the 3 Watts per gram rule of thumb. That would be about 35-40A on 3S. As far as the prop size, I think the 10 x 5 or 11 x 5 would be a good starting point. If you run it up for 15 seconds or so and feel the base (non-rotating part) for heat, you'll be able tell if you're OK. If you can keep your finger on that after at 15 second full throttle run you are under 130F/54C and can probably go to a larger prop.

With the watt meter you'll be able to correlate the wattage reading and temperatures and after a while you'll know wha the limits are for the motor. For the plane you described, the same motor with a Kv down around 900 to 1000 or so would pull a larger prop and and you might be able to go from taxiing around to actually flying.

Jack
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Old May 13, 2012, 07:42 PM
RPoe
Joined Feb 2010
32 Posts
Sounds like you've solved the mystery!!

I REALLY appreciate your help - I was warned by other members of our club not to listen to or allow the member that helped me, help me. Guess there's a reason he's no longer with our club.

Maybe I won't always be a newbie, and I'm definitely going to buy that watt meter and test everything. I actually bought a Hangar9 P51 PTS (the "trainer") and installed an Eflite Power 46, Castle 50A ESC and 5s battery setup, recommended by our local hobby shop. After about 3 flights, apparently the ESC let go and I have yet to troubleshoot it. So, I took all that out, installed an Evolution .60 (I think, it's the .60 size motor in a .40 size "package") nitro and have yet to test fly it after the electric power. I even bought Robart retracts for it - I guess I'm just a glutton for punishment - more money than brains, maybe?!?

Thanks again for your help.
Russell
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Old May 14, 2012, 06:14 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,844 Posts
It is too bad about the guy misleading you. I think this is a better place for advice. I got started here about 4 years ago and it has been pretty painless. You'll often get conflicting opinions and an occasional "my way or no way" person but for the most part we keep each other honest and can learn from that.

Some like to fly at high throttle and fast, some prefer more sedate and mellow flying (that is me), and those kinds of things reflect in our opinions and what we recommend to others. Once you get the details in hand and mind you can take a power system calculator like the free Web-O-Calc and enter your details and it will all start to make more sense.

Let Web-O-Calc choose some of the power system components you are not sure about for you and then you can change things and get a feel for the effects of using different props batteries, motors, and stuff like that.

If you enter your plane's specs there I think you'll find the motor will be different than what you have now.

Jack
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