B61 starter and polarity

[skydawg]

If you take a starter from a neg ground truck and put it in a +ground truck,using the same connections as the starter you`re replacing,will it spin backwards?

[tjc transport]

yes. DC motors are polarity sensitive. 

it you wire the negative ground starter up as positive ground, it will spin the opposite direction. 

to use a negative ground starter in a positive ground vehicle, you would have to convert the vehicle to negative ground. 

[mrsmackpaul]

I think it should be fine, to reverse the direction you would have reverse the polarity of either field or the armature 

If you reverse both I feel you should get the motor to spin the same way

Only one way tell, hook it up and find out 

 

Paul

[doubleclutchinweasel]

I'm pretty sure the leads were swapped on my R when they switched it from pos. ground to neg. ground.

[doubleclutchinweasel]

Yeah, I think they had moved the leads from the starter case to the solenoid and vice-versa.  See the clip from an old wiring diagram.

 

[doubleclutchinweasel]

I’ve been thinking about this. I’m not sure that I remember this correctly. Maybe you should ignore me!

[phildirt]

Some of the information above is wrong.

A starter will not change direction of rotation by changing the polarity.

 

 

[tjc transport]

2 hours ago, phildirt said:

Some of the information above is wrong.

A starter will not change direction of rotation by changing the polarity.

 

 

try it some day. take a DC motor and reverse the polarity. it will spin the other way. how do you think power window motors work?
AC motors will not spin opposite direction if the power leads are reversed. 

[Big R]

I believe both systems use the same starter. Power to the starter should b the lug on the side of the starter. Neg cable for a positive ground/ pos cable for a negative ground

[doubleclutchinweasel]

I am trying to remember back when I was studying electricity and electronics (before I decided that was not for me).

I believe, if a motor uses PERMANENT MAGNETS, it is polarity sensitive, meaning it will reverse if the polarity of the inputs are swapped.

But, if a motor uses a STATOR WINDING to create the magnetic field, it is NOT polarity sensitive, and will run in the same direction regardless of input polarity.  To reverse those, I think you have to reverse EITHER the armature voltage OR the field voltage.

But, don't quote me on that.  It has been 45 years since I thought about it.  I'd say wire one up on the bench and find out.

[phildirt]

Just to be clear:

Changing the polarity of the wiring to a Mack 12 (or 24) volt starter will NOT change the direction of rotation.

[doubleclutchinweasel]

That would tend to suggest they are the "universal" type, not permanent magnet type.  Good to know.

[Draggin Wagon]

I converted the ole Draggin Wqgon from 24V positive ground to 12V negative ground and it still went backwards in reverse 

[phildirt]

D E L E T E D

Edited June 24, 2023 by phildirt

[mrsmackpaul]

15 hours ago, doubleclutchinweasel said:

I am trying to remember back when I was studying electricity and electronics (before I decided that was not for me).

I believe, if a motor uses PERMANENT MAGNETS, it is polarity sensitive, meaning it will reverse if the polarity of the inputs are swapped.

But, if a motor uses a STATOR WINDING to create the magnetic field, it is NOT polarity sensitive, and will run in the same direction regardless of input polarity.  To reverse those, I think you have to reverse EITHER the armature voltage OR the field voltage.

But, don't quote me on that.  It has been 45 years since I thought about it.  I'd say wire one up on the bench and find out.

I believe you are 100% correct

 

Paul

[Freightrain]

Starters do NOT reverse rotation with polarity changes.  The power goes into the armature and windings.  Thus reversing both which cause it to run the same direction no matter what.

Story:  Few years back, at the motor shop I use they were putting an FE on the dyno.  They threw one of their "shop" starters on it and it won't start or build oil pressure.  They were stumped for quite a while....until they pull the cap and saw the distributor was going the wrong way.  Seems, somehow they got their hands on a REVERSE Rotation starter(used on twin engine boats).   They only go ONE way no matter how the wires are put on.

[mechohaulic]

if a starter spun "backwards" it would NOT  throw out the bendix drive . high speed proper rotation causes the starter  drive to throw out and engage flywheel, does not mean A starter can't be built to throw opposite rotation. 

[doubleclutchinweasel]

3 hours ago, Freightrain said:

Starters do NOT reverse rotation with polarity changes.  The power goes into the armature and windings.  Thus reversing both which cause it to run the same direction no matter what.

Story:  Few years back, at the motor shop I use they were putting an FE on the dyno.  They threw one of their "shop" starters on it and it won't start or build oil pressure.  They were stumped for quite a while....until they pull the cap and saw the distributor was going the wrong way.  Seems, somehow they got their hands on a REVERSE Rotation starter(used on twin engine boats).   They only go ONE way no matter how the wires are put on.

That matches what I said above about changing polarity of EITHER the armature or the field to make it run backward.  As long as the armature and field windings are not disturbed, the polarity going to BOTH of them is reversed, and the motor would turn the same way.

Very good the way you stated it.  Makes everything sort of come together!

Thanks for that post!

[Vladislav]

Ok, I have a couple of cents to throw into the ring.

No theory (it's a late time at me so I'm not leaned toward thinking much)

I have two different starters on two different (old) Macks which did DIFFERENT changing polarity. One was installed on 1944 NM-model with 707 EY gasser. When I purchased the truck one of my guys put a battery on it after which I fired up the engine and drove the truck off a trailer and to my yard. The next day when I started investigating the things myself I found out my helper put the chassis wire to the negative terminal of the battery (he just didn't keep in mind existing of the positive ground system). But the truck could drive as I said and I found no hurt to generator or other electrical components.

The 2nd starter is for my NR-model with 519 ED Lanova diesel. It's 24V motor which operates with series-parallel setup. I rebuilt that starter and before putting it onto the engine I got to figuring on which terminal to connect to which polarity. Just tested both ways and found out DIFFERENT direction of rotation.

Of what I noted two starters had different design. The diesel one had 4 brushes and both armature and housing magnets were wire coils. The one on the gasser was not investigated by me (since it's on the truck and works) but as I recall at the moment I saw 6 brushes inside it.