Author Topic: Motor quality issues ??? (Read 3542 times)

Dan Bregar · « **on:** August 29, 2011, 06:21:27 PM »

This is a question to the electric C/L stunt community. Have we been doing this long enough to be seeing quality issues with different brands of motors. Are we getting 500 flights with brand X motor and no issues, and getting 150 flights with brand Z motor and having to replace the bearings. You get my drift I'm sure. Since I have only built and flown (So far) One airplane with about 60 flights to date, I'm a rookie at this. But I have plans to build a few more and before I use brand Z motor again I thought I would query the guys who have way more experience than I. At least then I will have some experienced input when I pick a new motor or two for my new airframe projects. So you guys who have been doing this for 2 or 3 years now, what say you ? And I hope we don't start a Fox VS Supertigre, or a Ford VS Chevy war. Please refrain from that jazz, please, please.

Wynn Robins · « **Reply #1 on:** August 29, 2011, 06:26:59 PM »

all i'll say is that you definately get what you pay for.......

I started out using turnigy motors (cheap introduction into ECL) they lasted less than 3 months

I went to scorpion - so far so good - have had one running for 2 years and it still seems OK HOWEVER

I am now using Plettenberg - and dont think I'll ever go back to anything else!!!!!

Dan Bregar · « **Reply #2 on:** August 29, 2011, 06:32:03 PM »

Wynn

How many flights on the Scorpion in 2 years ? Your educated guess.

Crist Rigotti · « **Reply #3 on:** August 30, 2011, 12:50:05 PM »

Quote from: Wynn Robins on August 29, 2011, 06:26:59 PM

all i'll say is that you definately get what you pay for.......

I started out using turnigy motors (cheap introduction into ECL) they lasted less than 3 months

I went to scorpion - so far so good - have had one running for 2 years and it still seems OK HOWEVER

I am now using Plettenberg - and dont think I'll ever go back to anything else!!!!!

Wynn,
Would you mind going into detail on why you like the Plettenberg motors? Thanks.

William DeMauro · « **Reply #4 on:** August 30, 2011, 12:57:24 PM »

Dan,
I have a Scorpion with 140 flights and still going strong. I have another in my SV 22 with 100 exactly and still going strong. I have a third Scorpion that I had a bearing failure after 110 flights but that may have been due to a slightly out of balance spinner. Now here is my take on this whole thing. If I were to only get 100 flights on a set of bearings I'm doing well!!!! A set of stock bearings for the Scorpion cost about $5. A decent glow plug cost about around $5. I bet that very few of us used to leave glow plugs in for 100+ flight(yes I'm sure some people did). Now I'm not even counting other types of wear and tear that occurs on glow engines or cleaning materials used to clean your plane after a flying session or for 100 flights. See where this is going!!!!! I'm NOT going to complain if the only wearout items I have on our motors is a set of bearings every 100 flights or so. If we don't crash or overheat them,they can be restored to new like condition by just a simple bearing replacement. If we want we can oil them every 50 flights or so.That may extend their life. We can spend a bit more money and buy a higher quality bearing if we want also. These days decent bearings are available to us for any motor we run budget or Plett. Right now I'm trying to decide if I should just replace the SV 22 bearing or run them to failure to see how long they last. Either way I feel those bearings have served me well.

David Hoover · « **Reply #5 on:** August 30, 2011, 01:49:14 PM »

Wynn,

What makes the Plettenberg worth about 90% more than the same sized AXI?

Wynn Robins · « **Reply #6 on:** August 30, 2011, 02:52:24 PM »

Quote from: David Hoover on August 30, 2011, 01:49:14 PM

Wynn,

What makes the Plettenberg worth about 90% more than the same sized AXI?

Zee German engineering! HA...

I have AXI as well - and they are very nice motors...

Wynn Robins · « **Reply #7 on:** August 30, 2011, 02:54:48 PM »

Quote from: Crist Rigotti on August 30, 2011, 12:50:05 PM

Wynn,
Would you mind going into detail on why you like the Plettenberg motors? Thanks.

each to their own I guess - i dont really have an affinitity to plettenberg - I jut like them- all the motors I have used (bar the turnigy) have been great - the Pletts just have something the others dont- maybe its like the "halo' effect.

Crist Rigotti · « **Reply #8 on:** August 30, 2011, 03:44:51 PM »

Quote from: Wynn Robins on August 30, 2011, 02:54:48 PM

each to their own I guess - i dont really have an affinitity to plettenberg - I jut like them- all the motors I have used (bar the turnigy) have been great - the Pletts just have something the others dont- maybe its like the "halo' effect.

Wynn,
Nothing definitive?

John Hammonds · « **Reply #9 on:** August 30, 2011, 03:50:10 PM »

Quote from: William DeMauro on August 30, 2011, 12:57:24 PM

Right now I'm trying to decide if I should just replace the SV 22 bearing or run them to failure to see how long they last. Either way I feel those bearings have served me well.

Hi Will,
I know I'm preaching to the converted on this but I had a bearing "Tighten Up" on my Boxcar Chief, (E-Power 2815/09) it all happened very quickly, I guess the Phoenix just pumped in more amps trying to maintain the RPM until it shut down. Fortunately??? I was inverted at the time so just ended up having to replace the vertical stab. I dread to think what would have happened had I been half way through a vertical 8 or O/H. If I had an SV 22 and I knew the bearings were a bit suspect I'd be straight down the bearing shop..

Like you say, treat em like glow plugs with the added advantage that once replaced as long as the motor has not been mistreated it will be like new again.

TTFN
John.

Dan Bregar · « **Reply #10 on:** August 30, 2011, 04:57:00 PM »

William

Thanks for your great comments. Your point is well taken and certainly has merit. However I am lazy so I would rather have a motor that goes 500 flights before it needs new bearings as opposed to one that only goes 120 flights before bearing replacement. Of course if one costs four times more than the other, then I could stop being lazy.

William DeMauro · « **Reply #11 on:** August 30, 2011, 06:23:59 PM »

John and Dan,
Point well taken, I will not wait for failure,especially since this SV 22 is the best flying plane I ever built or owned. I will not wait for a failure. I do have one spare Scorpion set on hand and 2 more on the way. That way I can change out the two 100 flight plus be left with a spare set. As far as the Pletts go I have a few but only one is mounted at the moment. I have been flying a 15-18 in my SV 11, that i put in to test out and liked it alot. It is an extremely smooth running motor, with plenty of power. I do like Gov Mode which forces me to use the Shulze Speed Control, which is heavier than the Phx 45 and I have to carry an external BEC. I do pay A slight weight penalty but it really works well!!!!! If I can get my next plane a few ounces lighter I would use my Plett 20 series in it. I also barely fly the SV11. If your counting dollars then there is a much bigger penalty. I don't think most people will justify the cost for what most may not even be able to see in performance. The Pletts are well made but are not for everyone.I also believe some of the top fliers do have 500+ flights on their pletts. Again it comes down to what works best for you.

Wynn Robins · « **Reply #12 on:** August 30, 2011, 06:41:08 PM »

Quote from: Crist Rigotti on August 30, 2011, 03:44:51 PM

Wynn,
Nothing definitive?

nope - I just like em is all.

Dan Bregar · « **Reply #13 on:** August 31, 2011, 04:12:43 PM »

So far all we have talked about concerning "motor quality" is bearing life. There are other factors which determine "motor quality" for sure. What immediately comes to mind is efficiency. Or to say it a different way, how many watts out for how many watts in. The difference is used up as creating heat. For a given load (prop) how much current is drawn. Makes a difference in how much batt. we use up. I have heard of motors being rated at 80% efficiency. Some may be more or less efficient. Also I don't know if all motor manufacturers use the same method to calculate efficiency. Probably not if it makes their motor look better in the specs they use their own method. So what say you guys. Surely there must be a guru or two lurking about.

Tim Wescott · « **Reply #14 on:** August 31, 2011, 04:45:36 PM »

Back in the days when most motors were brushed and used ceramic magnets, efficiency was a big issue -- it wasn't uncommon for a direct-drive setup to load up the motor to less than 50% efficiency, and if you were getting more than 65% efficiency with a geared can motor you were doing good.

Now, I don't see nearly as much about it -- I assume that this is because most motors are pretty efficient. When you get right down to it, with LiPo batteries and brushless motors, just motor efficiency takes a back seat to a lot of other issues.

Having said that -- it'd be nice to see more reviews of motors that include getting them onto test stands and actually measuring electrical power in and mechanical power out. Ditto ESCs, and they are not without their own losses.

You can come pretty close to calculating a motor's efficiency if you know how much current it draws unloaded, what its resistance is, how much current it draws loaded, and its Kv rating.

Dan Bregar · « **Reply #15 on:** September 01, 2011, 07:17:54 PM »

Tim

Thanks for your input. I know you have been flying E-C/L for a couple of years now. Have you found any particular brand of motors more prone to failure in your experience ?

Andrew Borgogna · « **Reply #16 on:** September 01, 2011, 07:55:34 PM »

I agree with Dan, efficiency is more important than how long the bearings last. Well let me restate that, 150 flights on a $45 motor, 300 flight on a $90 motor their quality is equal in my mind. All my motors are firwall mounted four nut/bolts and they are out. Efficiency is a different story, that goes straight to how big a battery I will have to use. In electric stunt every ounce counts. One of these days I will work up the courage to change a set of bearings, but I haven't had a problem yet. Well there is that pesky Arrowind motor but it still pulls the 1/2a Pathfinder around like a champ and has never given me any problems other than how it feels. The Turnigy motor I have is a good dollar value unit, it may not last that long, but it didn't cost very much and it pulls my Trophy Trainer around like a freight train. If I were flying at the expert class in high value contests my take would be much different, but I am a Sunday flier having a great time with electric planes.
Andy

Tim Wescott · « **Reply #17 on:** September 01, 2011, 07:58:50 PM »

Quote from: Dan Bregar on September 01, 2011, 07:17:54 PM

Thanks for your input. I know you have been flying E-C/L for a couple of years now. Have you found any particular brand of motors more prone to failure in your experience ?

Dang. I've been forgetting my disclaimers. I think I assumed that everyone knew, but I forget that there's a constant influx of new people...

Actually -- if you discount some attempts in the early '80's -- I've been flying RC electric for about 15 years, and I've been doing engineering work on various aerospace and industrial applications involving electric motors for about 20. So I have tons of knowledge that applies.

But I've only recently gotten back into the control line fold, and have yet free up an electric power system for flying on strings! I'm also a tightwad, and tend to milk whatever I have for as long as it'll work. I'm much more likely to identify the problems with something and rework it than I am to go out and s-s-s-s-p-p-p-end m-m-m-m-o-n-n-n-ey on hobby stuff. So unless folks in my area start showing me stuff that they've crashed I'm not good for for things that require me to have gone through a dozen different motors. Theoretical knowledge -- yes. Knowledge that transports well from industrial use -- yes (and our motors are a lot like industrial brushless motors in many ways). Knowledge that transports well from RC use -- yes. Specifics about particular brands -- nope.

In general, from what I've seen on the RC flying field, most of the motors show a strong correlation between quality and how much you pay for them: the really cheap stuff isn't manufactured to great precision, or they use cheaper adhesives, or they leave out dressings for the wires, etc., and it breaks faster. I think the biggest single difference between RC and CL is that we tend to turn a lot tighter, so a motor that's otherwise good for 'zoomy fast' RC flying, or hotliner powered sailplanes, or RC scale, etc., may suffer from premature bearing failure when you start doing all those square maneuvers. So what you're asking for -- specifics about brands -- is what I want to see, too.

(I'm tempted, in fact, to put an ad in the classifieds for broken motors -- I suspect that if you were willing to take the right mid-range motor apart and put it back together with better adhesives, bearings, materials, and possibly a bit of light machine work, you'd end up with something as good as a top of the line motor, for less $$. But you'd have to try it out on several brands before you knew for sure, and that'd take a lot of energy).

Dennis Toth · « **Reply #18 on:** September 02, 2011, 10:20:56 AM »

Guys,
Seems like most of the major brands (AXI, Scorpion, Hacker, Plettenberg, Rimfire, Thrust, even some Turnigy's) are OK for some 150 flights. We typically just take them from the box and put them in the ship and fly. Having just gone through a bearing replacement on my AXI 2826/10 after about 300 flights, I found out from Boca Bearing that it is a good idea to "oil" the bearing periodically. Both Boca Bearing and Scorpion sell a light bearing oil in a extended tip dispenser that will do the job. If we were to externally oil the bearing periodically I think the bearing life would increase significantly for the stock steel ball bearings that the motors come stock with.

Other quality issues - I look at the motor spec and choose the one with the lower resistance and highest Wattage rating for the kV I want to run. Another check to make is for a straight drive shaft. You can do a quick eyeball check before you install by rotating the bell and looking at the tip of the shaft to see if its running true. A more accurate way is once it is mounted to put a piece of straight plate stock say 12" long on the prop shaft (could also use a straight prop) and measure from the tip back to the wing LE, then rotate the motor and measure the other half to the same point, they should match if not you need to find out what is either out of alignment or bent.

Best, DennisT

Dan Bregar · « **Reply #19 on:** September 02, 2011, 04:11:03 PM »

Dennis

Good information ! About 300 flights on your Axi before bearing replacement. Good yardstick. And the oil sounds like a good practice also. Just as long as we don't get the oil in places other than the bearing and cause other issues. Are not these bearings sealed or at least shielded ? Makes for more difficult job. Maybe this extended tip gizzmo makes it easier. Thanks for your good comments !

Larry Renger · « **Reply #20 on:** September 06, 2011, 09:10:14 PM »

At least you can't get oil on the commutator and varnish it!

John Cralley · « **Reply #21 on:** September 07, 2011, 02:56:01 PM »

I oiled all of my motors after reading this thread. The bearings do not appear to be sealed.

Used a 1 cc syringe and a 1 1/2 inch 21 gauge needle. Easy to reach in the inside with a tiny drop.

Dave Adamisin · « **Reply #22 on:** September 07, 2011, 04:19:42 PM »

Quote from: John Cralley on September 07, 2011, 02:56:01 PM

I oiled all of my motors after reading this thread. The bearings do not appear to be sealed.

Used a 1 cc syringe and a 1 1/2 inch 21 gauge needle. Easy to reach in the inside with a tiny drop.

Simple.... and you are now in control of that varible. Nice work.

Author Topic: Motor quality issues ??? (Read 3542 times)

Dave Adamisin