Fixing an SDS drill, armature gets hot.

[Adrian80]

Hi All,

Looking for some advice on fixing a sds drill.

The motor was burnt out so i bought a new field and armature. Replacement vs repair was a bit marginal.

After i stripped it down and reassembled it the base of the armature get really hot really quickly.

I’m not quite sure why this is.

I put the old bearings back on the armature, and the front one seems fine but the rear isn’t exactly free spinning.

Could a little bit of binding of a bearing heat up the armature that quickly?

There is not a lot of spark coming from the brushes which i think is good.

If anyone has any other suggestions that would be great.

Thanks
A

 

[RandomGrinch]

Could be a short on a winding where enamel has been nicked?
A bearing may cause heat issues, but I doubt any more than it would get under a drilling load, but I may be very wrong!
...any chance you know anyone with an IR camera!

 

[Adrian80]

Sadly don’t know anyone with an IR camera.
Don’t suppose they have an app for that on an iPhone?

 

[RandomGrinch]

A friendly local sparky may have one (or university, or fire service!). They are useful for locating hotspots in wiring.
I'm afraid no iPhone app unless you also pay a couple of hundred pounds for a camera add-on.
...and it depends what you mean when you say the 'base of the armature'. If this is the end by the bearing, it could very well be the bearing!

 

[Gasguru]

I first came across these 50 years ago in my Grandads workshop...

Wind forward to 4.30 when the action starts...

 

[conny]

I first came across these 50 years ago in my Grandads workshop...

Wind forward to 4.30 when the action starts...

It's commonly called a 'Growler' and is an old method of checking for shorts in the armature winding. Not a very good method in a workshop these days as there are so many modern devices to test properly with.
To the OP, as someone has already asked, what do you mean by 'hot at the base'?
Is it hot at the end where the bearing is 'dodgy'? You may have misaligned the bearing races when re-fitting it which has caused flat spots on the ball bearings but this wouldn't cause it to get hot very quickly. It sounds as though the windings or the commutator have been damaged during fitting. Without specialist testing equipment and knowledge of electrical winding then you need to give it to a repairman who does or find a local winding shop who may do a quick test of the unit for a couple of quid cash in the hand. your other alternative is to bite the bullet and buy a new drill.

 

[Adrian80]

Hi all, thanks for your input.

i tested the armature.

Axel to commutator, all ok
Bars next to each other, resistance roughly the same.
180 Degree test, resistance roughly equal.

The brushes seems ok. I had to replace one of the brush holders as I cracked it trying to remove /clean it. I lined up the new bush holder best I could. squared up the brushes on some wet and dry and refitted them.

I may be over thinking it, but how hot is an armature supposed to get in normal use?

I pulled it apart quite quickly after warming it up and it seems like its the copper bars get warm quite quickly.

Any other suggestions? I think I may have to admit defeat and ask the local repair shop for some advice….

Thanks A

 

[Adrian80]

Also if anyone knows of some bearing pullers with nice thin legs that would amazing…

 

[RandomGrinch]

Possibly just normal operation!
Drills do get hot.
Interesting link, temps in °F
https://toolguyd.com/thermal-image-of-a-cordless-drill/
And drill troubleshooting link:
https://www.ereplacementparts.com/repair-center/power-tool/electric-drill/motor-gets-hot/

 

[Adrian80]

I think it’s probably a little too toasty for normal operation. Feels like 50 to 60 C.

I’m wondering if the brushes need time to bed in and make better contact or something.

rear bearing is certainly not as smooth as it could be, but it’s not horrifically lumpy or grinding.

ill be on the phone to the repair shop I think.

 

[RandomGrinch]

You gave it a good go, theres no harm in trying!

 

[opps]

Sadly don’t know anyone with an IR camera.
Don’t suppose they have an app for that on an iPhone?

Some of the Android Caterpillar phones have IR cameras

https://www.catphones.com/en-gb/new...iciency-with-thermal-imaging-from-cat-phones/

There is one for sale (the S60) on ebay at the moment. With a day left. it is currently at £100.

https://www.ebay.co.uk/itm/234164523376?hash=item36854b1170:g:XOgAAOSwCd5hLIL1

A friend of mine (a plumber) used to have one. He said it was extremely useful for tracing underfloor heating. Unfortunately, he had to hand it back when he left the firm.

No idea if it would help the OP though.