Author Topic: Electric motor repairable? (Read 2537 times)

jonda500 · « **on:** June 03, 2017, 07:16:20 PM »

I recently couldn't get a spark out of my petrol mower - it has no points so I'm stumped there.
So I grabbed an old (patented 1934) electric motor I had lying around in the shed and made a bracket so I could bolt it to my 70's victa base.
First I just bolted the base plate with the blades on it to the motor shaft (big centre bolt into hole tapped in motor shaft, three smaller bolts into a collar grub screwed to shaft), sat the motor on the bench and plugged it in... BAD idea - gave me quite a fright - it wasn't quite balanced and almost jumped off the bench into my Hondas before I could unplug it..
Any way I got it fitted to the base and balanced by carefully centring the base plate exactly before tightening the four bolts.
I got to mow the lawn maybe a dozen times with no problems, but the last time at the exact moment when I unplugged it, it made a loud electrical crack and the house fuse blew. I reset the fuse and plugged the mower back in and it instantly made a loud noise accompanied by big sparks shooting out the top which blew the fuse again.

Is this motor likely to be quite dead and not viable to try and fix, or could there be a simple short circuit inside maybe?
thanks, John

Steve F · « **Reply #1 on:** June 04, 2017, 05:50:19 PM »

Just break down and buy a new GAS mower before you electrocute yourself or chop off a foot or worse.
Hospital bills are WAAAAAAaaay more costly than a new mower.

jonda500 · « **Reply #2 on:** June 04, 2017, 07:50:15 PM »

The petrol engine has more horsepower and higher rpm, but the electric motor seems to have way more torque. I seriously doubt either would be capable of severing a human foot though! I prefer gasoline mowers because, yes there is a very real danger of running over the power lead with electricity powered models. Apart from that flaw though electric mowers are quiet, free from toxic fumes/smoke/gases, need no maintenance, take no gas or oil and always start turning as soon as you plug them in (until they don't!).
I was hoping this vintage electric motor would outlast the gas motors that keep regularly dying on me....... doh!

BomberMann650 · « **Reply #3 on:** June 04, 2017, 11:35:49 PM »

Old motor like that is probably easy to rebuild.
Seems you could use some more advanced circuitry to control the power jolts at startup and shutdown.

BobbyR · « **Reply #4 on:** June 05, 2017, 06:21:10 AM »

That electric motor is dead. The windings have probably burned and are shorting out. Your observation is correct, an electric motor has all of it's torque at startup unlike a gas motor. The electric motor under load will draw more amps as the load increases. When the load gets high enough it will draw more amps and try to keep going and it will overheat. If you want to continue using an electric motor, you need to get one with a horsepower rating equal to or higher than the gas motor. You can rewind and electric motor, but it is very expensive.

Duke McDukiedook · « **Reply #5 on:** June 05, 2017, 06:39:29 AM »

If you want to stick with an electric motor for that mower get one with an electric fan that will help keep it from overheating like yours did.
Like Bobby said you could rewind the coils but unless that is an old Delta or Baldor motor it probably isn't worth rewinding.

jonda500 · « **Reply #6 on:** June 05, 2017, 07:12:37 AM »

Yeah I figured it is probably burned out too good to be worth trying to fix, funny thing is though, it wasn't very hot the day it died - previously I worked it so hard that it was too hot to touch, but not on the day it died- I had only mowed a small area and it was running free under no load when I unplugged it, the loud click when I unplugged it I thought nothing of, but when I went inside the house fuse had tripped, then when I tried to finish the lawn - well that moment when I plugged it back in, that was when it's little heart stopped beating for good!

John

strynboen · « **Reply #7 on:** June 05, 2017, 10:07:52 AM »

that non European types engines ...use a knikser koupler vith a sentifugal moved shifter..so it can be that vho are broken up..some use a kondensator..other have 2 set Windings..a start coil..and a runing coil..the start vill be cut off vhen the rpm are at top speed..it vill get to hot..if it not Works like that

so tru to take the 2 small schrevs and take the small top plate off..and thek for Loose vires..or burned kontaktors...there must be a short..or a Loose vire make problems

RAFster122s · « **Reply #8 on:** June 05, 2017, 01:05:41 PM »

Strynboen, I got part of what you said but, have you ever considered firing up Google translator to translate your Danish to English? The first part I did not understand. Granted your English is far far better than my attempts at anything close to your language.

strynboen · « **Reply #9 on:** June 05, 2017, 01:14:46 PM »

have thekked the translator..but it gives often a even more strange,translation then my viking English..but il vill try to look in it Again..if it gives a better resultat..i had 4 year English in the mittel scool..so only have a very basis understanding.

vfourfreak · « **Reply #10 on:** June 05, 2017, 01:21:53 PM »

Oddly enough I can follow Strynboen's quixotic English perfectly. There again, all my ancestors were pillaged and worse by the Vikings, hence my blue eyes that svay all ze vomen.

If I can help perform as intermediary please let me know.

Duke McDukiedook · « **Reply #11 on:** June 05, 2017, 01:35:35 PM »

Quote from: RAF122S on June 05, 2017, 01:05:41 PM

Strynboen, I got part of what you said but, have you ever considered firing up Google translator to translate your Danish to English? The first part I did not understand. Granted your English is far far better than my attempts at anything close to your language.

His keyboard won't type certain English characters so it can make it tough for him to spell out some engrish words.

jonda500 · « **Reply #12 on:** June 05, 2017, 06:29:09 PM »

So, I took off the little cover under the two little brass nuts - inside is just where the power cord connects and there's no sign of any arcing in there...

Edit note: A PO has rattle canned the motor black without masking the holes, so everything inside is somewhat black from the overspray entering through all the holes. There was a sticker loose in there which under the black paint says "to reverse interchange coloured leads".

jonda500 · « **Reply #13 on:** June 05, 2017, 06:33:19 PM »

I removed the bearing end cap and the top cover, but still can't see any burnt wires or windings...

jonda500 · « **Reply #14 on:** June 05, 2017, 06:40:10 PM »

It does seem to have some sort of centrifugally operated err thing in there, looks like I am gonna have to remove it from the mower base to get the bottom cover off and pull the guts out so I can see where the damage is...

TwoTired · « **Reply #15 on:** June 05, 2017, 06:54:08 PM »

Is there a data plate on it somewhere?

jonda500 · « **Reply #16 on:** June 05, 2017, 07:02:57 PM »

Yes, under the paint, I found it has an attractive brass data plate...

TwoTired · « **Reply #17 on:** June 05, 2017, 07:10:41 PM »

Made in Sydney?
What size blade was it turning?
Were you running it on 230v 50 cycle?
Does that say 37 amps?
What gauge extension cord were you using? And how long?

eigenvector · « **Reply #18 on:** June 05, 2017, 07:12:44 PM »

3.7 Amps

jonda500 · « **Reply #19 on:** June 05, 2017, 07:34:17 PM »

Yep, Made in Sydney.
The blade plate is 12.5" diameter, the total cut width is 18.1". I had to trim the length of the blades a little to make a rover plate fit into the victa cowl.
I ran it on 240v 50 cycle (what we have here).
3.7 amps, I believe that makes it 888watts.
I've been using two 15amp extension leads, but when it died it was only running through the shorter one (the area that I mowed is right next to the 10amp outside powerpoint I use(my shorter lead has a 10amp plug fitted to the male end)).
Thanks for your time guys, however unlikely it is, I'd love to be able to fix this thing!
John

scottly · « **Reply #20 on:** June 05, 2017, 07:48:49 PM »

Does the centrifugally operated start switch operate freely?

jonda500 · « **Reply #21 on:** June 05, 2017, 08:06:48 PM »

Yep, the centrifugally operated switch operates freely - the mechanism pulls the top disc part down and then it pops back up when the speed is slow enough. I can push it down and it pops straight back up when I release it...

scottly · « **Reply #22 on:** June 05, 2017, 08:15:00 PM »

How do the points look? Any evidence of arcing or carbon tracking in the surrounding area? With a 230V potential, ground up plant fibers can be conductive.

jonda500 · « **Reply #23 on:** June 05, 2017, 08:25:14 PM »

I can't see any evidence of arcing or carbon tracking but I 'll be able to look better and see how the points look when I disassemble it further...

Going by the ferocity and magnitude of the electrical flames that shot out the top I felt sure I would find something severely melted/burned under the top cover

scottly · « **Reply #24 on:** June 05, 2017, 08:38:15 PM »

Quote from: jonda500 on June 05, 2017, 06:29:09 PM

So, I took of the little cover under the two little brass nuts - inside is just where the power cord connects and there's no sign of any arcing in there...

Take a closer look at the wire on the right, something looks funky where the wire meets the terminal, and it is very close to the outer cable (earthed) fitting. Any signs of arcing on the underside of the cover?

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Author Topic: Electric motor repairable? (Read 2537 times)