Starter 1000 3C

[michipons]

Hello!
I'm restoring the starter motor on my 3C, one of the last things I have left to do.
Before I opened it, it worked, but once it was opened, I wondered how it could work...
The brushes were almost falling apart in my hand, the brush holder plate was completely rusted, the paper around the coils was rotten, the insulating paper was rotten... curiously the armature shaft was in good condition.
The question is that I need spare parts for the restoration: insulating paper, brushes, it would be great to find a brusher plate...
Or if someone has a starter motor in good condition I'd also be interested, and if it's not in good condition I'd be interested too, so I can make one out of two.

Is there a website where I can find spare parts?

Greetings and thank you

 

[pf1]

I believe they are the same as on a Sanglas Miguel, the starters were made in Spain too. I could be wrong, that information was given to me years ago but I've never seen a Sanglas to check it out.

 

[chrisk]

I've never seen a Sanglas to check it out.

And so are the days of our lives.

 

[michipons]

Another application for Cerakote! I couldn’t plate it with the isolation of the +brushes, this looked like a good protective solution…

Regards

 

[sfcpiet]

Imho, you've shot yourself in the foot, Miguel.

If I'm not mistaken, the field cores need to be bare steel/iron to allow for proper magnetic current flow. Even rust in this area influences performance negatively. Same for the inside of the housing. If the brush holder hasn't a proper connection to ground, the sucker won't even nudge when you power it up. They're not left bare without reason.

Someone will surely be along to confirm, or flame me.

piet

 

[michipons]

Mmh! Is all not a big deal because i can blast it again.

Said that, i was talking to a friend (laverdist in the antipodes) regarding where the “negative” goes, to see if I could paint the brush holder or not, we reached the conclusion that the earth is done between the armature axis and the case bushes, nevertheless I was counting on assuring a good connection between the brush plate and the cases just in case.

For the field cores, no idea, they were totally rusted so i removed the rust blasting them and cerakoted to give it a try, i couldn’t see why they should be left uncoated as the fields are isolated with that tape from the cases and the cores…

Same for the cases, as far as they are connected to each other and with the aluminium part that bolts to the engine….

I was reading some theory regarding those starter motors to have some clear concepts, but otherwise my knowledge is 0. So every input is highly appreciated! Actually I believe it is a very interesting topic given the very little literature about it.

Miguel

 

[Dellortoman]

we reached the conclusion that the earth is done between the armature axis and the case bushes

No, I believe you've been led astray there. The armature (rotor) doesn't have an earth as such. Current flows to and from the windings via the commutator and brushes. Both the power supply and earth connection for the rotating armature winding is external to the armature itself. It doesn't require an earth connection through the shaft and bearings. In fact, if there's any current flowing through the bearings, then there's a failure of the insulation in the armature winding.

I'm not convinced by Piet's assertion that all internal surfaces need to be bare metal. Piet is rarely wrong in his technical advice, but perhaps in this case he's being a little over-cautious. As long as there's good earth connections for the rotor and stator windings, it should be OK. Paint coatings shouldn't affect magnetic fields. Just scrape off any coating where electrical contact needs to be made.

However, you could have a problem if the paint coating on the inside of the housing is thick. I'm unfamiliar with Cerakote so I dunno how thick the coating is. But there's not much clearance between the rotating and static components of the motor, and that clearance gap will close up by the thickness of the coating on the inside of the housing. It's probably very unlikely, but there's a possibility that you could end up with mechanical interference between rotor and stator.

 

[bazzee]

The casing is part of the magnetic circuit produced by the field coils, I would suggest metal-to-metal connection between the field poles and interior of the casing would be desirable. Even a thin coat of paint between the two will introduce magnetic resistance (reluctance) into the magnetic circuit. Cam's concern with physical clearances may be a more immediate problem.

bazzee

 

[Dellortoman]

The casing is part of the magnetic circuit produced by the field coils,

Are you sure about that Baz? It sounds very unlikely to me.

Electric motors require specific field intensities and polarities (N or S) in specific places around the perimeter of the motor. I suspect that the pretty much uncontrolled magnetic field induced into the annular casing would tend to dissipate the field strength rather than enhance it, which seems like an undesirable thing to my mind. I suspect the only role the metal case plays as far as magnetism is concerned is to shield any nearby components from stray magnetic fields.

But I'm not an electrical engineer. I have just enough knowledge and experience in the subject to be dangerous, so I could very well be wrong. I'm happy to be educated by anyone who's better informed on the subject of DC motors. My dad was a very smart electrical engineer who was an expert in electric motors and generators (among other things). I used to defer to him for such questions. Unfortunately he's been pushing up daisies since 2007 and I don't have a ouija board.

 

[martymoose]

Aren't the windings varnished? Like on a stator?

 

[Vince]

Encapsulated in Epoxy I think.

 

[sfcpiet]

I once wanted to build a lightweight starter with an aluminium alloy housing, a sparky friend explained it wouldn't work properly due to a possible interruption of the magnetic fields.

The field coils conduct electricity, and lots of it, therefore they need to be well insulated from all around. It is this electricity that produces the magnetic field that causes the motor to spin.

piet

 

[bazzee]

Now I'm going to have to find my class notes on DC motors and generators! However just saying that the field coils produce a fixed magnetic field which the rotor interacts with, on the inside of the field coils. The field also extends on the outside end of the field coils, and is then entrained within the material of the casing which is steel or iron, i.e. a ferromagnetic material. I've never seen a dc motor or generator with an aluminium housing.
If the field wasn't constrained it would interfere with any nearby magnetic components and I suspect would reduce the efficacy of the field coils.
Fecking hell I'm sounding like an academic! Sorry!

quick edit: added a diagram (below) found on the internet showing magnetic flux flow in a 4-pole machine.

bazzee

 

[Vince]

I have a vague memory of Radar interference with really early Ducati Superbikes at some circuit in England close to an airport.

 

[michipons]

Wow! Nice posts!

Well, I have proven that there is no continuity from the armature to its axis, so that means that the “negative” goes through the brushes to the plate and from there to the casing-engine. So i will have to assure a good grounding there.

On the other side, the inner part of the casing is coated with Cerakote which is 1 mil thickness, so 0’02 mm, which shouldn’t interfere with the armature-coils clearance.

Regarding if the coating can affect somehow the magnetic fields, we will know it soon when i receive the spare parts! i will try it first before removing the coating. Nevertheless, the cases where already coated with normal paint which is much thicker than Cerakote, so I want to believe that this will have no effect as far as all cases are not isolated from each other.

A protective thin coating must be better than 2mm of rust… taking into account that before was working…?

@bazzee nice diagram, is the onky one i’ve seen which shows conductivity between the coil cores and the cases! I will make sure the are also not isolated from each other!

Miguel

 

[Andy]

I don’t think there’s any problem with the coating. Electrical insulators aren’t magnetic isolators. Clearance may be a problem, but unlikely.
Also doubt that there is any adverse affects to removing the steel body. Lots of motors have plastic bodies.
[edit… I’m wrong there, a steel body will carry the magnetic circuit if the poles are separate, plastic bodied motors have a complete field coil… whoops ]

 

[Dellortoman]

Thanks for the explanation and diagram Baz. Makes sense now. Never too old to learn stuff.

You know those things that people have on their desks to keep pens and stuff in? Well, the one on my desk is a Laverda starter motor casing .
It's been sitting there for for years but it only just dawned on me that it's the exact thing we're talking about. I don't think this particular one has much magnetism going through it though.