E3L rebuild - new grumbling noise

[mikeb]

Hello
i've fiited a new armature and other bits, including bearings, tho on reassembly there's a slight grumbling noise on rotation. it sounds like a bearing tho when dis-assembled they rotate smoothly and freely. it will run when assembled - with noise that i can feel.

the new armature measures upto 0.35mm larger diameter than the old one so it could be contact between that and the field coil or case, but there are no clear marks to show. I haven't measured if its concentric to the centre (not sure how).

what to do? one option is turn the new armature in the lathe and take off any high spots. or just attack any high spots with emery paper.
another option could be to open out the case-field coil chamber. I don't have the machinery to bore this accurately tho again could just attack it with emery paper (if i could figure out the location of high spots).

any thoughts?
thanks

[Rex]

Emery paper won't take off anything more than surface corrosion. Slow rotation of the armature by hand should show if there's any contact between the field pole and the armature, though if the noise is a rumbling I'd suspect the bearings.
Sure you didn't preload the bearings when you assembled it?

[Triton Thrasher]

If it’s touching, there should be witness marks.

[Bsareg]

If you're motoring the dynamo by joining the F & D together,  they all do that sir. Don't  know why, may be some magnetic effect.  If you use the F & D as feed and return (no case connection) it'll spin with less power but with no noise.

[mikeb]

thanks for the suggestions. i stuck the new armature in the lathe and cleaned it up. i noticed the ceramic bit at the brushes end was a little wider at places so that may have been touching and not leaving obvious marks as not metal on metal. I also put an old bearing back in the brushes end as could feel some roughness in the new one - I may have preloaded or otherwise injured the new bearing on first installation.
anyway, two things corrected and it now runs smoothly (and motors on the bench).

as an aside, the new armature had the problem noted above and very tight threads that needed cleaning up (maybe wrong thread pitch angle?) so is a bit disappointing. lets hope in generates reliably. I fell for the 'UK made' slogan and of course it has no brand or manufacturers identity. gotta love new parts.

[Rex]

Gotta love new pattern parts.
Probably never been near any UK factory.

[RDfella]

So a new armature needs machining and a new bearing feels rough. Did you actually pay money for these parts? If so I'd want a refund.

[KiwiGF]

From memory the bearings in the dynamo are “std” metric ones that skate boarders use in considerable quantiies, the local SKF shop should stock them and sell em cheap. Say less than $10. I put sealed version bearings in my dynamo.

[mikeb]

i think i have to take to credit for that bearing damage - a bit ham-fisted sometimes. good to know Kiwi - i may have my next dynamo failure outside a skate park. but the armature did need some cleaning up. i meant thread angle (above) not thread pitch.

this may have been a pointless thread as I answered my own question but from my end no one said not to machine the armature, so i did, and of that I wasn't sure. so thanks for the comments.

RD at this end of the earth there's not many people to complain to. at risk of sounding a bit paranoid there's a theory that all the real crap gets put on the boat to this end of the world coz they know the postage means you'll never send it back.

[Triton Thrasher]

there's a theory that all the real crap gets put on the boat to this end of the world coz they know the postage means you'll never send it back

The bike business has always had its share of undesirables, but I can’t see anyone opening all the bearing boxes to find the one bad bearing out of thousands, to send to the Antipodes.