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Old Jul 30, 2001, 07:30 AM
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6Volt 400 Shake Rattle & Roll

New Graupner 6 Volt 400 broken in using water technique.Re-timed in proper direction for geared use.Timing was moved about 4 mm when it was observed that the brushes were not arcing at all.Motor bearings were lubed with one drop of appropriate oil.Motor was installed in a brand new Graupner gear box that had the rear bushing changed to a ball bearing before it was ever run.The output shaft on the box spins free without binds when the motor is not installed. The pinion is brand new and appears to have no defects when viewed with a magnifying glass.I installed the assembled unit in a plane using 8 cell 1250scr battery pack and a Jeti 35 ESC. Motor runs great up to 3/4 throttle when all hell breaks loose.Tremendous vibration and visible brush arcing.I disassembled the entire installation about 25 times to no avail.Changed the motor(same gear box) and it ran smooth as silk.Put the new one back in and had the same problem.Neglected to say that the prop is balanced and nothing is loose.The gear mesh is also o.k.Out of frustation I let the sucker run at high throttle and the problem has now become intermitant with non vibration periods lasting about one minute. At high motor when running well it tachs 7200RPM .The gear ratio is 2.33:1. Anyone got any ideas?

[This message has been edited by mml4 (edited 07-30-2001).]
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Old Jul 30, 2001, 09:48 AM
Speed Demon
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Antioch,CA,USA
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Don't use that motor. These things are mass produced and real cheap, theres bound to be a reject here and there.
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Old Jul 30, 2001, 10:31 AM
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Hi Greg! I agree with your non use suggestion but I am soooooooo curious as to what the defect is in this motor. I even checked to see if the commutator was loose-it isn't.Believe me it's not the $10 for the motor,I just don't believe in the concept of the "lemon".There is a reason why this is happening.Like the Dirty Harry movie"I gots to know"!
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Old Jul 30, 2001, 01:12 PM
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A possible explanation is that the bushings are a tiny bit oversize for whatever reason. Try putting a drop of fairly heavy oil on the bushings, or automatic transmission fluid. If this reduces or fixes it, then that's the probable cause. In any case, use a different motor in the plane or plan on re-oiling it every flight or two.
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Old Jul 30, 2001, 08:15 PM
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co usa earth
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I have experienced the same thing in speed 300 motors. In my case the motor bushings wore out just enough to let the motor have spells of terrible wobbly running, then it would just smoothe out. To look at the bushings and try to move the shaft resulted in nothing. I couldnt tell that there was too much play. When power was hooked up, it ran smoothe until high throttle settings, then would go crazy, make alot of vibration noise, and drop to about half of full rpm. When the motor first started doing this it was intermitant. As the motor wore out more, it just got worse, and became unuseable. Cheap motors, cheap motor bushings. I have had the same problem with non rebuildable roar stock motors. Come to think of it, I have wore out a few 540's that way too. The smaller motors seem to wear out faster. Using the water break in will speed up the process. All it takes is a few seconds in the water to get the break in job done. Any more than that will cause increased wear. Be sure to lube the motor bushings before using water break in. Then, relube them. If the endbell was put on even just slightly tweaked, it would have caused the premature wear as well.

[This message has been edited by tickettothemoon (edited 07-30-2001).]
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Old Jul 31, 2001, 08:14 AM
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Hi Bob&Ticket! You guys made my day.The idea of lubricating the bushings before the water treatment is well taken.I didn't do that but I followed the break in procedure as explained on the EZONE.The total time in the water was only till the liquid began to change color.Now that I have a reasonable explanation I will experiment a little bit by trying to swap out the bushings for ball bearings as we did on slot car can motors 30 years ago.I really appreciate the help as I am new to electric flight and probably would have ruined more motors by not lubricating the bearings BEFORE as well as after the break in process! Thanks again to you both--Marc
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Old Aug 01, 2001, 10:54 AM
Heli Bouncer
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Have you considered that the retiming may mis-align the rear bearing plate, I know this is a long shot but apparently some speed 400 motors don't have self aliging bushings. I have a pair of Multiplex ^v 400's, and was amazed that they didn't have this feature! Even cheap shaded pole 110 v AC fan motors have self-aligning bushings.

Looee
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Old Aug 01, 2001, 04:19 PM
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Hi Looooeeee! Hope I got the correct # of Os' and Es'. I called Boca bearing today and discussed the availability of replacements. They told me that while the bearings are available the cost will be about $20. This seems like a lot to put into a $10 motor since I really am not 100% sure this will cure the problem. Being new to Electric flight I did nothing more than follow the instructions for re-timing that I found posted on the E ZONE.Could you please explain how the alignment was altered by the re-timing process.The vibration only starts at about 1/2 to 3/4 throttle and then this condition does not happen all the time.If the bearings were misalligned wouldn't there be some symptoms at other rpm.About 60% of the time the motor runs smoothly and really behaves. The vibration is so severe when it occurs and is so loud that I am beginning to think that the armature is hitting the magnets. Some of our Ezone colleagues have said that they think the bushings may be worn. I don't know enough to dispute this but visual inpection and spinning the shaft by hand show nothing out of sorts.What really bugs me is that I can't produce conditions that will make it either behave or run wild.It seems to have a mind of it's own. Remember this is a never flown motor and gearbox having never suffered any crash trauma at all.I am going to open up the can this weekend and do thorough inspection. If I can convince myself as to what the problem is I will try to repair it as an academic exercise. I don't believe I would ever trust it to power a model unless the problem is something as obvious as an incorrectly mounted magnet.Thanks for your input. I will definitely look at the allignment of the bearings again. Marc

[This message has been edited by mml4 (edited 08-01-2001).]
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Old Aug 02, 2001, 12:15 AM
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Marc

I guess the first thing to look for is whether your motor has either a metal rear plate with a fixed round bushing or a nylon, (white soft plasticy) plate with a cylindrical projection housing a round BB sized bushing.

(Der Zip is of the opinion that these motors don't benefit much from water break-ins. I'm running in one of my 6v motors in the stand on the geardrive at static with short bursts to full followed by long slow runs until battery needs recharging. No problems so far. Don't tell anyone this, on the E-zone, real big secret, shhhh.. )

Anywho, the self-aligning bushing usually resides in plastic housings, but probably can be found in metal ones, (Not that I've seen.) If you pull motor apart see if the shaft in the rear bushing can pivot around at angles other that straight on, thats a self-aligning bushing. It's funny you mention this, as one of my 2/3rds length speed 400's has shown this behaviour also at static. I'm wondering if it will go away in flight as it might be amp related. The other thing to check, I suppose, would be any obvious slop in either bushing.

My speculation on how the rear plate might by warped, is maybe due to the fact that these plates are fairly thin metal, you twist them slightly using needle noses in some sort of holder, am I correct? If it spun freely after the retiming, than this theory is schputz, and you can disregard my ramblings.

The only other thing that might be the problem is gear eccentricity, but this would show up as a tightening and loosening of the gear mesh. (As many o's and e's as you want to use...)

Looee
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Old Aug 02, 2001, 08:31 AM
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Hi Looeee!Think I might try your secret breakin method on my replacement 6 volt.Why would the vibration be amp related? As far as the re-timing method, I used a tool dedicated for this purpose from Hobby Lobby. Getting back to the vibration-It occurred to me on the way in to work this morning that the brushes and their springs may in some way be causing this problem. This is my first experience with internal brush assemblies and I must admit I miss the opportunity to stretch the retaining springs and inspect the brushes. Thanks for your thoughts! Marc
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Old Aug 02, 2001, 09:59 AM
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Marc

Some time ago Grupner had a hole production of S400 with bad bushings, they wore out in only 1 flight in a pylon plane, at leest those we could get here in Denmark, you could have got one of them.
I have allso had one where the amature was out of balance. It ran ok at 1/2 - 2/3 of power, but after that ..... !! Itīs like your car, if a weell is out of balance it doesnīt shake all time, maybe only at 50mhr.

Hans
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Old Aug 02, 2001, 09:59 AM
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Joined May 2000
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My experience with these gearboxes is that they are very sensitive to motor vibration and will exaggerate it at certain RPMs. The motor is only suspended by the front face with two screws. It is easy to bend the front faceplate which misaligns the bushing on that end. I've had them get bent just from the weight of the motor after hard 'landings'. Once this happens its almost impossible to ever get it to run smooth again. Sometimes I can correct it by just grabbing the motor while its mounted to the gearbox and bending it carefully upwards or downwards while it runs and listening for the vibration. I can often find the 'sweet spot' where it will quiet down.
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Old Aug 02, 2001, 05:11 PM
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Auckland New Zealand
Joined Mar 2001
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Quote:
Originally posted by Hans:
I have allso had one where the amature was out of balance. It ran ok at 1/2 - 2/3 of power, but after that ..... !! Itīs like your car, if a weell is out of balance it doesnīt shake all time, maybe only at 50mhr.

Hans
IMHO it will be armature balance causing most of your problem. Poor balance will soon slog out the bushings.
As these motors are mass produced you will often find that they have not been balanced, altho my experience with the Graupner ones is that they usually are.
Run the motor with a balanced prop on it (without the gearbox) & see if it vibrates then.
If you are reall keen, pull the motor to bits & see if the armature is balanced properly. ie re balance it.



[This message has been edited by Keithw (edited 08-02-2001).]
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