Motor still noisy...

[sdg111]

Well, I thought I'd fixed my noisy motor but took a short test video and played it back and it sounds much the same as it did in my last two videos.

I've stripped it all down, twice, and I think the noise I hear is the teeth on the prop shaft and the motor when they turn together. I can hear it when I turn the propshaft with my fingers and think this is the same noise, albeit louder and faster, that I hear with the on board camera.

The shaft is turning freely and everything else is nice and tight. I don't know how noisy the two cogs should be when turning?

The only other query is how tight should the first nut after the clear spacer be? This clearly has an effect on the movement of the prop shaft against the motor. I have less than 1mm of slack when I tighten it, is that about right?

Thanks for any suggestion.

[flydiver]

There IS gear noise, one of the reasons some people hate them.
If either the motor or the gearbox shaft is bent even a little it'll be worse if it makes the meshing erratic. I had another GB that was really noisy and it turned out to be just an ever so slightly bent motor shaft. Fixed the > amazing how much quieter and smoother it became.

I wouldn't be surprised if the resonance through the foam makes it sound worse than it might actually be. Difficult to determine what is normal off a video from one of those little cameras unless it's obviously out of whack.

I have used a DRY Teflon spray lube I found in a hardware store to help quiet the gears a bit.
Also, put a drop of oil (now WD40) on each end of the motor where the shaft comes out. Wipe off excess.

1mm of slack and no binding should be OK. No old system to look at so I'm not definitive about this.
I don't think there is any way to adjust the gear mesh (lateral movement) on this system, right? Too tight and it binds, too loose and it rattles. Both will tear up teeth faster.

[sdg111]

Thanks Fly, very helpful as usual. I'm not at home now so can't examine the motor, but how easy is it to check/replace a bent motor shaft?

I'm assuming it's not the prop shaft you're referring to but the actual shaft within the motor housing? Can you get spares for the motor or do you just need to replace it?

[flydiver]

You need to replace the whole motor if there is a problem. I've taken one apart-not too hard. Could not get it back together though. Don't know how they get those brushes in there.
They are cheap anyway.

It would seem unlikely you would bend the motor shaft since it is facing backward and is very short. Possible I suppose in a nasty enough crash.

Generally you can replace brushless shafts. Something to consider when you get to that stage. Some of the cheaper motors may not have that option.

[sdg111]

Thanks again Fly. I'll try some dry lube and see how it goes. Can't think of anything else 'cos it all looks okay.

[sdg111]

Fly, another thought. Can you actually get replacement brushed motors for the Cub? I can't see any on the spares list.

Not that I'm intending replacing it, that would be a last resort when the present one packs in.

[flydiver]

Doesn't appear to be a problem, at least in the US.
HobbyZone HBZ7134 secure.hobbyzone.com/search/HBZ7134.html

[sdg111]

Okay, found it. Not as widely available as many other parts as my usual online store doesn't stock or list it, which I guess says something about the longevity of the motor.

It seems the most expensive part to replace, by some margin, is the receiver/ESC unit, at a hefty £35.

Thanks Fly for all the advice.

[flydiver]

Yes, the RX/ESC combo is the most expensive part. A 20A ESC will set you back $20 anyway at least and Spektrum RX seem to go for $50 for the real ones. They have a good deal with those RX. Then they figured out B-n-F. Dang good marketing.

[sdg111]

Still plagued by this noisy motor. Took it all apart again and what I've noticed is that the prop shaft doesn't slide in and out of the motor housing as smoothly as it did when it was new. It's as if there's some binding/catching going on.

I've powered the motor on its own and its nice and quiet, but as soon as I add the propshaft to the equation it's much louder.

Not sure whether to buy another gearbox housing (which come with the propshaft) or not. When I bought this the last time the bearings, front and rear, came separately and have to be pushed in. The only thing I can think of is that I've put these in wrongly. Anyway, I'm poisitve it should be quieter than it is.....

[kenninny]

take the prop shaft out,and put it on the edge of a table with the gear over the table, give a little push,
and watch it roll, if its bent, even a little you should see the gear wobble. hope this helps

[flydiver]

Wrongly assembled - can't help you there, I don't have one around anymore. Maybe someone has a picture.

Crack in the gearbox - check VERY closely while pushing and pulling strategic parts. Don't bother to glue that plastic. It won't hold well. Replace if needed.

Bent shaft - replace. VERY VERY minor (hard to see) bends in the shaft will cause noticeable problems with gear meshing. I could not see the bend in mine but when replaced the noise quieted down substantially. If you've bashed it a good assumption is you may have bent it. Even breaking props with a nose-over while still spinning under power will bend it.

Check the firewall for cracks.
Check the GB screws.
Can't think of anything else. Replace the shaft.

Tired of the whole thing - upgrade to brushless.
Of course you can certainly bash, bend, break, and otherwise ruin those also.

[Capt.Crunch]

I just bought a prop shaft and have the same issue,turns out the plastic gear has wobble from not being pressed on to the shaft correctly at the factory.

[flydiver]

A wobble in the gear would have same effect for a different reason. The gears vacillate between meshing too tight, then too loose, and do so very fast making a racket.

[iandhunt]

I got a brushed motor and brushed ESC for the cub in my garage. If you want I can ship it to you for a few bucks. Let me know via message if you are interested.