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Grounding for a drum sanding motor

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Forum topic by gthomson posted 05-05-2015 02:28 PM 1074 views 0 times favorited 20 replies Add to Favorites Watch
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gthomson

15 posts in 595 days


05-05-2015 02:28 PM

Topic tags/keywords: sander

I have a home made drum sander that my grandfather made many years ago.
It uses this same motor for driving it – http://www.doublequicktime.com/item/description/id/72320447
The wiring was looking pretty old and in need of replacing, and the sparks that happened when I plugged into the wall helped to verify that, as well as the look of the wires on the motor side after that.

I wired in a new power cord – it was probably just a power cord from a PC.
Just connected the two wires, and it got it working.

I think it’s best if the ground wire is also connected, but I don’t know how that fits into it.

This is a look into the electrical connection area –
http://www.gthomson.us/projects/drumsander/motor-electrical.jpg

With the new power cord (in the picture linked above), I connected one to the left post, and the other to the right post. And the middle post (# 2 post) didn’t seem to be a ground.

Does it make sense to connect the ground wire from the power cord so that it contacts the metal body of the motor? Or does anybody know if that #2 post in the middle is where the ground wire should be connected.
The motor is probably 35+ years old – but still seems strong.
But 35+ years ago they didn’t do so much specific to grounding wires did they?

-- Techie by trade, tinkerer at heart


20 replies so far

View MrUnix's profile (online now)

MrUnix

4247 posts in 1667 days


#1 posted 05-05-2015 05:04 PM

Most old motors that I’ve run across were ungrounded, and I always add one when rebuilding. Just run the ground wire to the frame. Find a suitable mounting screw in the frame body. The picture you show looks like it’s an old GE motor. Here is one very similar that I added a ground connection to:

The ground wire comes out into the wiring area so it can be attached to the cord ground using a wire nut:

Just for grins… here is what that motor looked like when I got it:

It didn’t run, was butt ugly filthy inside and out, the Klixon thermal protector was fried from a PO wiring it wrong, was missing the wiring cover, one of the end shaft/felt covers was damaged, and the felt oilers were full of dirt/grime and dry as a bone. It is now in almost daily use and purrs like a kitten :)

Cheers,
Brad

PS: That #2 terminal is NOT a ground!

-- Brad in FL - To be old and wise, you must first be young and stupid

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exelectrician

2327 posts in 1895 days


#2 posted 05-05-2015 08:21 PM

I totally agree – Grounding is important, because it saves your life when things go wrong with the windings.

MrUnix – Wow! what a nice clear example for all of us to follow, great photos thanks for posting.

-- Love thy neighbour as thyself

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OldEd

39 posts in 1080 days


#3 posted 05-06-2015 04:55 AM

Yeah…. Okay, the way the power system works, is that they supply you with 220 center tapped.

The “black” wire is the “hot” side – one or the other end of the 220 volt side of the transformer. The “white” wire is the “neutral” “side” – the center tap.

THAT CENTER TAP IS NOT, REPEAT NOT ALWAYS GROUND!!!!!@

IT CAN FLOAT!!!!!

That is where the “green” wire comes in: THAT is tied to earth ground at the service entrance, which is normally the main breaker box.

YOU SHOULD TIE THE GREEN WIRE (IN THE CORD) TO THE FRAME!!! That way, if the motor should short out to the frame or whatever, it won’t be “hot” – touching it won’t fry you to a crisp.

If you have ANY question or doubt about what you are doing, I most STRONGLY suggest you take it to a motor repair shop to have the work done. Your life and health are worth far more than the cost of a competent job.

-- OldEd

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TheFridge

5765 posts in 954 days


#4 posted 05-06-2015 05:19 AM

Not much to it. Tie it to the frame. Forgot about it

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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dhazelton

2326 posts in 1764 days


#5 posted 05-06-2015 12:05 PM

Yeah, center post could be for 220 (can’t read the motor plate well). Put a spade terminal on the your green wire and put it on any nut on the motor housing and you are good.

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gthomson

15 posts in 595 days


#6 posted 05-07-2015 09:02 AM

Thanks all for the input – I know what I need to do at the most minimum level now.
And a special thanks to MrUnix for the photos – great photos and inspired me to think beyond just getting it working, and to understand it better and look to making it work well with some cleanup.

I may as well learn first on this one.
I have as a future project to cleanup a big old iron Delta Unisaw – early 1950’s I believe – another very much appreciated hand-me-down.
It still works fine, with some quirks, and served me well with some Corian work I was doing a few years back.
But I have no doubt it could use a good going over.

And OldEd, thank you as well for the suggestion to take it to a motor shop – I couldn’t agree more that I probably should :-)
My history working with electric has not been great.
Was untangling a cord to a hanging lamp once, and grabbed a section where it was frayed on both routes, and then it grabbed me. It only let me go when I shook so much I dropped the lamp and it broke.

And in the older CRTs, where they have that big red wire on top that says HIGH VOLTAGE in big red letters…
Well, I figured it was okay since I had just unplugged the monitor.
So I was messing around with that wire/plate on top with a screwdriver to see what was inside…
Didn’t grab onto me that time – threw me on my butt about 4-5 feet away.
Learned more about static electricity that time.
Ahhh… so that’s what SCE means when they need the line to de-energize before they work on it – stored electricity in the wires – similar to static electricity?

You did get me thinking about something else, though – I wonder if there’s a local place that teaches how to work on repairing/refurbishing motors like these. That might be a good place for me.

-- Techie by trade, tinkerer at heart

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robscastle

3393 posts in 1672 days


#7 posted 05-07-2015 09:51 AM

You may also wish to consider grounding the complete assembly to prevent static build up.
Its not lethal but can give a huge surprise when you least need it.

-- Regards Robert

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OldEd

39 posts in 1080 days


#8 posted 05-07-2015 03:48 PM


And OldEd, thank you as well for the suggestion to take it to a motor shop – I couldn t agree more that I probably should :-)

My history working with electric has not been great.

Was untangling a cord to a hanging lamp once, and grabbed a section where it was frayed on both routes, and then it grabbed me. It only let me go when I shook so much I dropped the lamp and it broke.

And in the older CRTs, where they have that big red wire on top that says HIGH VOLTAGE in big red letters…

Well, I figured it was okay since I had just unplugged the monitor.

So I was messing around with that wire/plate on top with a screwdriver to see what was inside…

Didn t grab onto me that time – threw me on my butt about 4-5 feet away.

Learned more about static electricity that time.

Ahhh… so that s what SCE means when they need the line to de-energize before they work on it – stored electricity in the wires – similar to static electricity?

You did get me thinking about something else, though – I wonder if there s a local place that teaches how to work on repairing/refurbishing motors like these. That might be a good place for me.
- gthomson


Okay…. Yes, you REALLY should take it to a motor repair shop, with that history. I can’t tell from the pictures just what sort of motor you have, aside from being an induction motor. There are several varieties. The motor shop will be able to wire it CORRECTLY, as well as checking out any capacitors.

As far as the CRT goes, what hit you was one, or both, of two things. Either the residual charge in the high voltage power supply filter capacitor, or the residual charge on the crt itself. Since the voltage is up in the kilovolt range, the insulation is VERY good, so it will take quite a while to leak away.

Yes – by ALL MEANS TAKE IT TO A MOTOR SHOP!!!

And no, it’s NOT “stored electricity in the wires”, it’s the live power from the power plant lots and lots of raw electrocution-type POWER.

Hate to read of a member electrocuting himself on a motor.

-- OldEd

View MrUnix's profile (online now)

MrUnix

4247 posts in 1667 days


#9 posted 05-07-2015 04:06 PM

Calm down Ed :)

It’s a GE motor almost identical to the one I pictured (sans the thermal protector), no capacitor, and it’s wired correctly. All Robert needs to do is connect the green ground wire to the frame somewhere, and it will still work even if it’s left unconnected (it wasn’t grounded at all originally). I try to tie them in internally so it looks better, but pretty much any screw on the frame will work, even the one holding on the wiring cover. No need to take it to a shop and spend money that doesn’t need to be spent!

Cheers,
Brad

-- Brad in FL - To be old and wise, you must first be young and stupid

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OldEd

39 posts in 1080 days


#10 posted 05-08-2015 12:56 AM

Well, if you are SURE it is “almost the same”...

On the other hand… I quote:

“My history working with electric has not been great.
Was untangling a cord to a hanging lamp once, and grabbed a section where it was frayed on both routes, and then it grabbed me. It only let me go when I shook so much I dropped the lamp and it broke.”

I really REALLY don’t want to find a post saying that gthompson managed to do himself in trying to get that motor working properly… Remember: we don’t know for sure what that motor has been through, and what internal shorts might be in the waiting…

-- OldEd

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dhazelton

2326 posts in 1764 days


#11 posted 05-09-2015 12:20 AM

I resoldered the vertical circuit of an older CRT T.V. I had last year and was very careful about touching the gun. There are ways to discharge the electricity built up, I just don’t know how. Electricity is not a mystery – it’s really a science anyone can learn. Just don’t go in the deep end first time out.

View gthomson's profile

gthomson

15 posts in 595 days


#12 posted 05-09-2015 09:04 PM

I attached the green wire to the metal body, and put everything back together.
All seems good, almost.
It ran smooth before, now it wobbles a little.
I’m sure that’s a result of the setup falling on the arbor/shaft, with the weight of the
motor on top of it, while I was working on it, when my pooch got interested.

For what it’s worth, this is how the motor was used for the home made
drum sander. I think it may have also been used as a router table, given
the other hole and three screw holes around it.

I thought the wood bracket was also interesting, in case somebody was looking
to do the same.

Plugged it in, and all seems good, except for the slight wobble.
And while I know this probably isn’t the best way to go about it…
A couple strategic hits with a rubber mallot helped to reduce the wobble
so it’s barely noticeable. Probably hard to tell from a still photo, but this
is it running, and very little visible wobble now.

And while this won’t mean much to anybody else, I thought it interesting…
This is a shot of the bottom side of the table.
What I thought interesting was that ‘L’ that was lightly cut into it to
reveal the layer below. My grandfather’s name was Leeland Thomson – I’m
wondering if that was his ‘branding’ of it as his.
Will never be known… but I’m curious if people did brand their
tools/jigs/templates in ways to let it be known it belonged to them?

And OldEd, I thank you for your persistence in emphasizing that I don’t know
what I’m doing with this stuff. You are very correct on that, and it could
be deadly in some cases. A long funny story behind my previous attempt to
learn about working with electricity, but that’s a story for another day…

I’ve started down the route to again try to learn it.
I think I’m at this level – https://www.youtube.com/watch?v=jabo8iTesqQ
And was starting with this as a set of things to check -
http://www.wikihow.com/Check-an-Electric-Motor
But I think the $20 multimeter is not sensitive enough to see the reading
it mentions in section 3 of part 3. Or it may just be that I need to better
learn how to use it.

In getting started learning about electricity, is the multimeter the best
device to start with? And then obviously – learn how to use it :-)

As dhazelton mentioned, it’s a science not a mystery.
And that’s the way I’m looking to learn it this time around.

And if there is a post saying that gthompson did himself in trying to
get that motor working properly…
I promise, you won’t ever hear that from me.

-- Techie by trade, tinkerer at heart

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TopamaxSurvivor

17677 posts in 3143 days


#13 posted 05-10-2015 03:35 AM

Was untangling a cord to a hanging lamp once, and grabbed a section where it was frayed on both routes, and then it grabbed me. It only let me go when I shook so much I dropped the lamp and it broke. gthomson

It didn’t grab you, you grabbed it. That 120 volts easily over powers the millivolts operating your nervous system causing your muscles to contract when you are trying to let go. You are very lucky to shake it hard enough to get lose. The ground is the most important part of an electric system or circuit. Being with out it is like driving without brakes.

In getting started learning about electricity, is the multimeter the best
device to start with? And then obviously – learn how to use it :-) gthomson

I suggest starting with a analog meter with a needle movement instead of a digital. Digitals will give you readings that don’t make any sense at times. You will not have the experience to know when it is leading you down the Yellow Brick Road ;-) Lots of electricians don’t know why they are seeing ghost voltages on digital meters.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View OldEd's profile

OldEd

39 posts in 1080 days


#14 posted 05-10-2015 05:45 AM


And OldEd, I thank you for your persistence in emphasizing that I don t know what I m doing with this stuff. You are very correct on that, and it could
be deadly in some cases.

Thank you. You have already come VERY close to being an EX-woodworker. I hope you realize that grabbing that frayed wire was nearly lethal. I believe that the only reason you are with us today is that BOTH leads were frayed, and thus you were not the only path to ground. If the ground side hadn’t been available to carry the bulk of the current you would long since been dead.

It doesn’t take much CURRENT to kill – only a few milliamps, which can be supplied by something as small as a watch battery. The reason you don’t die handling D-cells, for example, is that your skin offers a high resistance – NORMALLY – and it takes VOLTAGE to break down that resistance – your skin sort of cooks, then chars, then… you aren’t around anymore.

And if you don’t understand the difference between CURRENT and VOLTAGE… Well, I’d suggest going back to school. The Kahn Academy is a good place to start, but you should realize you are starting at the most basic level. You have a long way to go before you understand circuit theory, AC current and voltage and phase angle. Induction motors – the sort you have – are not simple to understand.

However, good luck with your studies.
A long funny story behind my previous attempt to learn about working with electricity, but that s a story for another day…

I ve started down the route to again try to learn it.
I think I m at this level – https://www.youtube.com/watch?v=jabo8iTesqQ
And was starting with this as a set of things to check -
http://www.wikihow.com/Check-an-Electric-Motor
But I think the $20 multimeter is not sensitive enough to see the reading
it mentions in section 3 of part 3. Or it may just be that I need to better
learn how to use it.

In getting started learning about electricity, is the multimeter the best
device to start with? And then obviously – learn how to use it :-)

As dhazelton mentioned, it s a science not a mystery.
And that s the way I m looking to learn it this time around.

And if there is a post saying that gthompson did himself in trying to
get that motor working properly…
I promise, you won t ever hear that from me.

- gthomson

-- OldEd

View TopamaxSurvivor's profile

TopamaxSurvivor

17677 posts in 3143 days


#15 posted 05-10-2015 06:23 PM


I ve started down the route to again try to learn it.
I think I m at this level – https://www.youtube.com/watch?v=jabo8iTesqQ
And was starting with this as a set of things to check -
http://www.wikihow.com/Check-an-Electric-Motor
But I think the $20 multimeter is not sensitive enough to see the reading
it mentions in section 3 of part 3. Or it may just be that I need to better
learn how to use it.

- OldEd

You are correct OldEd, a multi-meter will give you an idea if it is totally wasted, but you really need a high voltage megaohm meter to really check out a motor. That is really getting beyond the scope of the novice.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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