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Old Nov 17, 2012, 02:39 AM
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Nightstone's Avatar
United States, AZ, Phoenix
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Whats the deal with these motors?

I have been using these HK motors for about 3 months. I owned 2 of the original ones. These run 17a on a 9050 and 21a on a 10x4.7. No issues

http://www.hobbyking.com/hobbyking/s...or_1200kv.html

So I buy 4 more. I notice the bell housing is machined a bit different otherwise they look the same. Put them on 3 new builds. 3rd build catches fire in air. Motor burned and esc melted to goo.

I test the remaining 3 motors. 25a on a 9x4.7 and 28-33a on a 10x4.7. @#$%&^$%%.... I'm assuming these are no longer 1200kv motors? This kind of stuff happen alot? Do I need to test each and every motor? Is the variance that much? Or is this something else? I have no way to test KV.

Does Turnigy use blind one armed monkeys to build these?

Thanks
Nightstone
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Old Nov 17, 2012, 08:06 AM
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tacx's Avatar
United States, MI, Macomb
Joined Apr 2009
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When dealing with the Chinese manufactures you have to remember there is very little ,if any, regulations imposed on them. What you got last week may not be what you get today.

Until, we start holding their feet to the fire you are just going to get what you get.
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Old Nov 17, 2012, 08:59 AM
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United States, NJ, Frenchtown
Joined Mar 2003
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If it is different looking ??

possibly a different company is supplying that part # motor now.

I believe KV is simply applying a accurate NO LOAD voltage like 3volts & measuring the motor shaft rpms WITH NO PROP ON IT.

So the 1200 KV motor would spin at 6000 rpms on 5 volts. I have black plastic set screwed gears with a white line across them for the tachometer to read as a propellor.

A quick check of your tachometer is to point them at a light bulb. & read it as rpms.
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Old Nov 17, 2012, 05:15 PM
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Ron H's Avatar
Bishopville S.C.
Joined May 2003
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Quote:
Originally Posted by Nightstone View Post
Do I need to test each and every motor?
Nightstone
Maybe it's just me, but I bench test before I make any changes in the power system.
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Old Nov 17, 2012, 05:28 PM
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United States, NJ, Frenchtown
Joined Mar 2003
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I am with Ron.

I do the KV test. A run at the maximum rpm it would run with a fast prop on it ..With no prop on. I run it on a loose piece of plywood . Any stutters are very easily heard as rpm jumps. It also points out any out of balance motors.

I keep a record of no load currents.
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Old Nov 18, 2012, 07:47 AM
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Kingston, Canada
Joined Jun 2004
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Over amping the motors to start with. It's rated for 16 amps and your running 17 and 21. Use props that run the amps just below its amp rating and it'll be happy. If you want to run a bigger prop, go to a lower KV motor. That particular style of motor was one of the first style of brushless motors to come out. Fairly low quality. I ran them fairly early on and found I had to put epoxy inside the bell as they were very out of balance. HK does have some high quality motors at the other end of the scale.

Gord.
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Old Nov 18, 2012, 09:04 AM
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Nightstone's Avatar
United States, AZ, Phoenix
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Originally Posted by flypaper 2 View Post
Over amping the motors to start with. It's rated for 16 amps and your running 17 and 21. Use props that run the amps just below its amp rating and it'll be happy. If you want to run a bigger prop, go to a lower KV motor. That particular style of motor was one of the first style of brushless motors to come out. Fairly low quality. I ran them fairly early on and found I had to put epoxy inside the bell as they were very out of balance. HK does have some high quality motors at the other end of the scale.

Gord.
The listed ratings from what I have found through my own testing is often very wrong. I never take whats up on HK's site as gospel. I Test. My mistake was taking it for granted that each motor is roughly the same ( will not do that again ). If the motor is not getting hot then I'm not over amping it. I have 80 plus flights on the first 2 I purchased without an issue. Including a few dirt dives and a mid air into a metal light pole.

My experience as a whole from these hobby parts vendors on the information they publish has not been to great. I don't think they actually test these motors real well and the information they publish is often whats posted from users. Now add variance from sloppy manufacturing and that posted information is useless.

Just another lesson to learn. My new method = TEST EVERYTHING.

Nightstone
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Old Nov 19, 2012, 10:03 PM
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Just wanted to post my own followup. Had some issues with my DT700 motors and certain ESC's. My test meter was showing as much as 35% variance between esc's on amperage output. This put me in research mode and I came to the following conclusions.

Esc can vary in output amperage as well as the motors. Shoddy esc quality and poor firmware coupled with an overall lack of quality control on some of these cheap motors can result in alot of variability when it comes to amperage. Test every combo and take nothing for granted. Nothing.

Nightstone
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Old Nov 20, 2012, 09:02 PM
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Canada, NB
Joined Apr 2006
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Quote:
Originally Posted by tacx View Post
When dealing with the Chinese manufactures you have to remember there is very little ,if any, regulations imposed on them. What you got last week may not be what you get today.

Until, we start holding their feet to the fire you are just going to get what you get.
Unfortunately I fear that when we do, the price will magically increase without due cause. It's bad enough people have to pay $60-$200 for a little styrofoam airframe.
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Old Nov 21, 2012, 01:33 AM
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Unfortunately I fear that when we do, the price will magically increase without due cause. It's bad enough people have to pay $60-$200 for a little styrofoam airframe.
I saw that right at the beginning going into this sport. Ii chose to build my own. I'm sooooo glad I went that way.

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Old Nov 29, 2012, 02:10 PM
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Canada, NB
Joined Apr 2006
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I hear you loud and clear. The EPS foam planes are made from the same material they are packed in, pre-expanded or non-expanded polystyrene, and the cost is minimal. The molds are cnc carved from wood or aluminum based on a scaled file, modified to house our fans, ducting, servos and packs, then fiber-glassed and coated with a release agent. The packaging was made the same way. 550 Grams of bargain basement EPS beads enters a heated hydraulic mold and suddenly turns into $200. I don't get it.

Motors are the same. A piece of round stock aluminum enters an automated lathe and is machined. Two bearings are pressed inside and a precut or molded armature is wound in sub assemblies and is interference mounted by hand of machine. The bell magnet housing and shaft are press fit, repeat for next motor.
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Old Nov 29, 2012, 02:32 PM
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manuel v's Avatar
Mexico, BC, Mexicali
Joined Aug 2004
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bad prop selections for this motor.

180 watts in max is necesary only. around 17a.

The best prop is GWS 9x5.
Don't use with SF, RS propeller.
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