Clearing out the garage. I have an electric strimmer that was hardly ever used but has been hanging up for about 10 years. When I plug it in and switch it on the motor turns but slow and sluggishly. Is it worth opening up and spraying with WD40 or should I just put it straight in the bin?
ISTR I had a similar issue with one like that - the main bearing had seized and rotation was being permitted by the bearing housing being spun against significant resistance in its (plastic) housing. A situation than ended up hot gloopy, and melted in quick order!
So if that is the case on yours, and you can free (or replace) the bearing, then it might still be ok.
(although it could be the armature has lost a winding, in which case probably beyond economic repair)
Rednadnerb presented the following explanation :
Don't spray WD40 inside the motor, it will wreck the commutator very quickly. Does the spindle turn freely - if not, it might suggest seized bearings.
Does it have the strimmer cord on it and is it over long?
Possibly.
No. ;-)
It depends on your skills.
If it's not been used much (and not actually damaged) then it could be the brushes have swollen and stuck, assuming nothing has seized up.
Cheers, T i m
Put a few drops of ATF on the motor bearings each end. Leave it overnight then turn it by hand. If it's fairly free, see if it runs ok. At this point if it turns freely yet barely moves under power it's had it. But in most cases this is enough to get a working machine again.
Apply all relevant safety cautions. Do not slash eyeball etc.
NT
ATF automotive transmission fluid? can I use 3 in 1 instead?
Yeah, ATF is noticeably better but any oil will help.
NT
1) Bearing check.
Strimmer is direct drive, no gear box. Check by rotating the working end, that rotation works freely. Listen for grinding noises from the brush assembly in the motor housing. There should be no "critching" nor grinding.
2) Ohmic switch.Unlikely to be a bad switch. You could use an ohmmeter on the switch if you suspect otherwise.
3) Bad brushes.This is the number one reason for strimmer failure. The brushes wear down, being carbon graphite and pressing against the commutator. Sometimes one brush wears more than the other.
At the store, they sell so many brushes, they keep a tray of them under the front counter, so they don't have to walk back into the parts aisles to get them.
On the old B&D, a portion of the brush holder would melt from the heat. The unit was then, unrepairable. For a while, I would send people away if they asked me to fix those.
My current (non B&D) is around 30 years old, and the plastic main housing, a portion cracked off the other day. Other than that, no sign of brush problems yet. Full power available.
When you go to the B&D/Dewalt store to buy a pair of brushes, don't forget to ask for "two crimps" to go with the "two brushes" you are buying. The crimps are necessary to join the brushes to the wiring. You have to know how to crimp, for the repair to be successful. I didn't have the right tool, the last one I did, but the crimp turned out very nice anyway, using a larger tool I did have. Not all my crimps are "pretty", and I've also managed to do some that any QA person would reject :-)
*Do not* succumb to the temptation to "clean the commutator".The only time you should pay attention to that array of shiny metal plates where the brushes touch, is if it is obvious that some burrs on the commutator, are tearing brushes apart. And causing premature failure and ohmic contact. Even if you see burrs, it can be almost impossible to do anything about it, without ruining something in the process.
You can only do a limited number of brush changeouts, before you have to replace the wiring harness to get enough wire to crimp in the new brush. If the brush contact had been done a different way, you could "deal with" bad commutator, by just frequent brush changes.
On big motors, the commutator plates are thick. Thick enough that the commutator can be machined on a lathe. All metal shavings must be carefully removed, if/when doing this. Only a large motor shop would have the setup for large motor commutator turning.
On a small motor commutator, it is too easy to leave burrs on the edges of the commutator plates. Even the act of cleaning it using DIY techniques, can do more damage than good. There's not enough metal, for turning it down.
Don't touch that part, unless it's obvious the commutator is so bad, it'll rip the brushes apart on first powerup. Don't spray any crap on there either. Not even contact cleaner! OK ? The brushes will eventually conform to the pattern of grooves in the commutators, as the brush will wear down until it seats and mates nicely with its new neighbor.
The odds of being able to buy a replacement rotor assembly should be almost zero. And if one is offered, it'll be expensive (to encourage you to throw away the strimmer and buy a new one). If I needed one, I'd just see if there was a junker I could acquire and do a swap.
Paul
+1 for i) not using wd40 ii) and not spraying it around
In which case one drop of a thick oil on each bearing and leaving for a day or two may work. If you have a certain cars you can get one drop of oil from your dipstick.
I think you can open it up, check the motor for tightness in the bearings. It could just be muck. I'd imagine unless it was not used due to it being under powered then it still will be. Also of course the cord it cuts with will be brittle and useless and depending on age, you may find the same for the spool holder as well, so if you cannot get spares it might still end up in the bin.. I have two you can have in various states of degradation grin. Brian
I once mended one of these things that was refusing to turn unless helped... turned out the gaps on the commutator were full of carbon build up, kitchen knife, bit of scraping, & back in business
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