DC starter motor Q&A/opinions- NGC

[Pressureangle]

I'm attending to the electric start on my '74 Aermacchi. They're famously weak and unobtanium. 
Here's my issue; a '72 Suzuki 750 water buffalo starter is a direct fit with an armature replacement, for the shaft fitment.
Problem is, rotation is opposite. Simple, right? not so much. Both starters are Nippondenso.

Original starter is Batt+ -> brush-> armature-> brush-> all 4 field coils-> ground.

Suzuki starter is Batt+ -> 2 field coils-> ground / Batt+ -> 2 field coils-> brush-> amature-> brush-> ground. 

The suzuki introduces Batt+ in the center of 4 coils, finding ground for 2 directly and grounding the other 2 through the armature. This makes it very hard to reverse the polarity only to the coils or only to the armature to reverse rotation. 
I can ground all the field coils directly easily enough, to keep their polarity. I assume since 2 were this way originally, the other 2 will tolerate it. 
The real question is, can I ground the armature brush directly, eliminating the resistance through the circuit by 2 field coils or am I looking for trouble? 

Problems, problems. It does have a kickstarter, but it's on the left side and the sidestand is a weak point.
 

[Kiwi_Roy]

To reverse rotation you must reverse either the current through the armature or through the fields, you seem to understand that

It doesn't matter which order the items are in just so long as the current flow is in the right direction.

[Pressureangle]

Yes. The problem is, 2 of the coils are wired into the armature, and 2 direct to ground. The only way I can reverse either/or is to isolate the armature. I don't know if the armature will tolerate the current. In the 'stock' Aermacchi motor, the armature grounds through all 4 field coils with a total of about 3 ohms. 

I *might* be able to determine what direction the windings are in each coil, and if they're the same as the Aermacchi motor, isolate the leads and wire the armature to ground though 3 ohms worth of them. 2 coils in the Suzuki motor come to about 2 ohms.

[Kiwi_Roy]

There are several different ways of wiring a starter motor, most are wired in series because thats a high torque arrangement and will wind up to quite a high speed. Traction motors are normally series type.

The Suzuki motor as you describe it is a compound motor, they can develop high torque but don't have such a high speed. The two "Shunt Fields" coils wired from positive to ground will be a higher resistance (over 1 Ohm). The Series fields are usually low, say 0.2 Ohms

It sounds like you are thinking of using the Aeromachi armature inside the Suzuki fields in order to have the right gear arrangement, how do you know it will fit?

How do you know which way it will rotate.

Why don't you try overhauling the Aeromachi starter, it will probably be easier than trying to reverse the Suzuki one,

A few pictures might help.

Perhaps a wiring sketch.

Do you have a document on the Aeromachi starter?

 

[Kiwi_Roy]

8 hours ago, Pressureangle said:

Yes. The problem is, 2 of the coils are wired into the armature, and 2 direct to ground. The only way I can reverse either/or is to isolate the armature. I don't know if the armature will tolerate the current. In the 'stock' Aermacchi motor, the armature grounds through all 4 field coils with a total of about 3 ohms. 

I *might* be able to determine what direction the windings are in each coil, and if they're the same as the Aermacchi motor, isolate the leads and wire the armature to ground though 3 ohms worth of them. 2 coils in the Suzuki motor come to about 2 ohms.

Its worth a try but keep the same field arrangement the Suzuki currently has 2 Shunt coils and 2 series coils, the armature will draw as much cauurent as the load calls for.

A picture is worth 1000 words.

[Pressureangle]

6 hours ago, Kiwi_Roy said:

Its worth a try but keep the same field arrangement the Suzuki currently has 2 Shunt coils and 2 series coils, the armature will draw as much cauurent as the load calls for.

A picture is worth 1000 words.

Here's the best I can do with the pictures. 

[Pressureangle]

14 hours ago, Kiwi_Roy said:

There are several different ways of wiring a starter motor, most are wired in series because thats a high torque arrangement and will wind up to quite a high speed. Traction motors are normally series type.

The Suzuki motor as you describe it is a compound motor, they can develop high torque but don't have such a high speed. The two "Shunt Fields" coils wired from positive to ground will be a higher resistance (over 1 Ohm). The Series fields are usually low, say 0.2 Ohms

It sounds like you are thinking of using the Aeromachi armature inside the Suzuki fields in order to have the right gear arrangement, how do you know it will fit?

How do you know which way it will rotate.

Why don't you try overhauling the Aeromachi starter, it will probably be easier than trying to reverse the Suzuki one,

A few pictures might help.

Perhaps a wiring sketch.

Do you have a document on the Aeromachi starter?

 

Don't know how I missed this post...

You're probably right, at this point; I'll post a pic here of the aermacchi starter fields. They're hand-wound crapola compared to the Suzuki unit. I have this Suz starter because somewhere in history someone said this works 'with some mods' or somesuch. The Nippondenso prefix is the same, 28000- and I assembled the suz motor on the bike with the Aermacchi armature (it measures the same) and it all bolted up nicely- but turns the wrong way. The Suz starter is infinitely more finely crafted inside. Since the fields are all to ground and common to the brush, I'll have to separate the leads to test them for shorts to ground. This could be the time to discover how hard it is to rewind it by hand, and add some power to it as well. But at this point, I have nothing to lose with experimentation but my patience. 
Looking closer at the photo, it appears there are 8 leads to the brush wire. meh

[Kiwi_Roy]

I assume the clean brush holder on the Left is Suzuki while the dirty one on the right is Aermacchi.

It looks as though the insulated brush on the Suzuki needs to be relocated to 12 O'clock to make it the same as the Aermacchi, that would change the direction.

[gstallons]

I hate to affect this conversation but , the starter drive splines on the armature are designed for the motor rotation as well as the sprag in the starter drive . You can get the starter to rotate in the opposite direction but , you can't fix this problem .

 I went to a buddy's house a few years ago where he replaced the battery on his Dixie Chopper . He replaced the battery and the starter would no longer engage .After an hour of work , I found the battery installed backward . The most important "moral of the story" . A permanent magnet motor will rotate backward when you install the battery backwards . 

[docc]

8 minutes ago, gstallons said:

I hate to affect this conversation but , the starter drive splines on the armature are designed for the motor rotation as well as the sprag in the starter drive . You can get the starter to rotate in the opposite direction but , you can't fix this problem .

 I went to a buddy's house a few years ago where he replaced the battery on his Dixie Chopper . He replaced the battery and the starter would no longer engage .After an hour of work , I found the battery installed backward . The most important "moral of the story" . A permanent magnet motor will rotate backward when you install the battery backwards . 

Is the V11 starter a "permanent magnet motor?"

[Kiwi_Roy]

48 minutes ago, docc said:

Is the V11 starter a "permanent magnet motor?"

The one on my VII Sport was, If you look at the outside of the case and see large screws holding the pole pieces in place its electro magnet, most of the permanent magnets I have seen are just glued in place.

You can barely see the screws in this picture, an impact driver is useful if you have to remove them. As an apprentice we would take the coils out and re-tape them with linen tape, often solves starter problems. (I'm not an auto electrician)

[Pressureangle]

1 hour ago, gstallons said:

I hate to affect this conversation but , the starter drive splines on the armature are designed for the motor rotation as well as the sprag in the starter drive . You can get the starter to rotate in the opposite direction but , you can't fix this problem .

 I went to a buddy's house a few years ago where he replaced the battery on his Dixie Chopper . He replaced the battery and the starter would no longer engage .After an hour of work , I found the battery installed backward . The most important "moral of the story" . A permanent magnet motor will rotate backward when you install the battery backwards . 

The Aermacchi armature engages a planetary gear arrangement. The armature will turn in the same direction as before in any case. I considered going to +ground, and it's still not an impossibility, but I'd have to sort the ignition and return to incandescent lamps from LED. 

[Pressureangle]

13 hours ago, Kiwi_Roy said:

I assume the clean brush holder on the Left is Suzuki while the dirty one on the right is Aermacchi.

It looks as though the insulated brush on the Suzuki needs to be relocated to 12 O'clock to make it the same as the Aermacchi, that would change the direction.

Clean= Suzuki, yes. 

At first blush that seems simple- is it so easy? Bring the field brush to 12:00, and move the ground brush to 9:00? Of course I'll have to use the insulated Aermacchi brush plate, but that seems easy enough if I can manage the extension of the brush lead. 
Won't that also change the polarity of the fields attached to the armature? 

[gstallons]

1 hour ago, docc said:

Is the V11 starter a "permanent magnet motor?"

Yes . the case is one solid cylinder with no countersunk screws in the motor case .

 The smaller diameter motors are permanent magnet . 99% of all mowers along with automotive vehicles  are permanent magnet starters . Some time ago , one of these forums discussed the magnet coming loose from the housing and causing no-start conditions . There was an adhesive to re-glue this magnet back in to the housing .  Sidenote = never hit the starting motor with a hammer if a no-start condition exists . These magnets are brittle and will break leaving you with a museum piece .

[gstallons]

In all the pics I see on this thread , the fields (field windings) are wound and not permanent magnet fields .

 Also , power window motors , etc. are permanent magnet . Many factors . size , cost , etc . Nothing wrong with them , I wouldn't want one on a diesel pick-up though .