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Sir Nibble

CAV Co-axial starter rebuild

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There's also shims to set the end float. I loop a bit of wire through them to keep them together and identify them as being the external group.

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At the front end are two plastic plugs, or steel core plugs.

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  • Greenie 1

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They have to come out to reveal the field coil connections. This is an S115 starter, that is the metric version of the old CA45 4.5inch starter. Metric, yea right. The threads on these screws are UNC and the hex is 2BA! They have to come out.

IMG_20200205_093355.jpg

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Returning to the back end, the nuts have to come off the negative terminal and the second stud 180° opposite. Then the through bolts and the comm end bracket can be removed. Behind it are these insulators and there SHOULD be O rings as well. Notice the internal group of end float shims which I identify by looping a doubled over length of wire through them.

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Now the brushes can come out. UNF screws now, and the brush holder can be removed.

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And off with the yoke/field coil assembly.

IMG_20200205_094525.jpg

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With the armature in the vice (soft jaws) the LEFT HAND THREADED nut can be removed.

IMG_20200205_094634.jpg

The pinion can be wound up the spiral spline

 

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Edited by Sir Nibble
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And with the drive end bracket pushed back

IMG_20200205_094755.jpg

The whole assembly can be withdrawn from the armature, liberating 12 steel balls.

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Remove the circlip, trip plate, washer, spring and collar and the pinion can be removed from the solenoid assembly.

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Ok. Solenoid assembly. First the resistor has to come out. That's another UNC 2BA screw where it connects to the moving contact and should be two rivets, one at each end. Screws and nuts in this case but all sorts of bodges rear their heads on these things. You can see the resistor around the outside of the casing.

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Then the solenoid terminals come out, a screw removed from where the fixed contact joins the positive terminal, two screws holding the assembly in and out it comes.

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This is the factory tool for removing the drive end bush.

IMG_20200205_103651.jpg

The clawed end goes in like this

IMG_20200205_103910.jpg

Then the shaft section is inserted and you beat it out with a nammer. So it ends up like this.

IMG_20200205_103945.jpg

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Without the tool you can put a hacksaw through the bush, cut a slot opposite the one that's already there and collapse the bush to get it out.

IMG_20200205_103520.jpg

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To strip the solenoid, the trip lever should be removed, rivets holding the trip lever frame and contact retainer drilled out and the moving contact and plunger withdrawn. The fixed contact plate will now come off and the spring holding the moving contact to the plunger removed to separate them. I will make this clear at the assembly stage.

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The solenoid plunger has an internal groove which carries four segments held together with a garter spring.

IMG_20200205_104418.jpg

These segments engage a shoulder on the pinion to carry it forward. They come out very easily. If you have the knack of putting them back in then there's nothing to learn in this thread as you must have done it all before. If you don't have that knack and you value your sanity, leave them in!

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All that's left now is to use a serious impact driver to shift the pole screws and remove the field coils. This coil shows damage typical of the insulation being bitten by expanding rust and they will need to be stripped and re-taped.

IMG_20200205_105700.jpg

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One coil stripped, one re-taped. Top tip. You know how raindrops catch on the hairs on a woolly jumper and don't soak in? Well I want the varnish to soak into the fresh tape so I waft a blowlamp flame over it to take the surface fibres off.

IMG_20200205_163930.jpg

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Last picture today. The commutator. The thing to notice here is the colour of the patina. A colour like this is a sure sign of a happy armature. 

IMG_20200205_105739.jpg

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3 hours ago, Man 'o Kent said:

An excellent "how to" presentation, I do like the indivudal images and related comments. Thank you!

Thank you. When I get the chance I will do something with a unit more typical of those on a narrowboat engine.

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Very interesting thread.  The starter on my engine is an "axial" and I understand how it operates but what does the term co-axial actually refer to? Is it a large inertia unit?  (I suspect there's more to it)

Pic of my engine below shows the starter, you'll know what model it is, I've forgotten.

 

 

IMG_0088.JPG

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That's a BS5. Co-axial refers to the solenoid and armature sharing a common axis.

Lovely engine by the way.

I shall explain how it works as and when. There's people building these who don't wholly understand it.

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1 hour ago, Sir Nibble said:

One coil stripped, one re-taped. Top tip. You know how raindrops catch on the hairs on a woolly jumper and don't soak in? Well I want the varnish to soak into the fresh tape so I waft a blowlamp flame over it to take the surface fibres off.

IMG_20200205_163930.jpg

 

Really neat job. I had my starter overhauled by a semi retired auto electrician, who'd done the job since leaving school.  The only time I phoned for an update, he told me he was "just re varnishing the coils" l didn't trouble him again.

 

 

3 minutes ago, Sir Nibble said:

That's a BS5. Co-axial refers to the solenoid and armature sharing a common axis.

Lovely engine by the way.

I shall explain how it works as and when. There's people building these who don't wholly understand it.

Brilliant, thanks.  Even google doesn't know, lol....

 

 

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I enjoy the fact that I get a lot of vintage stuff to play with.

2 minutes ago, NB Esk said:

 

Really neat job. I had my starter overhauled by a semi retired auto electrician, who'd done the job since leaving school.  The only time I phoned for an update, he told me he was "just re varnishing the coils" l didn't trouble him again.

 

 

Brilliant, thanks.  Even google doesn't know, lol....

 

 

The basic operation is fairly simple. It's the overspeed protection people don't get, that's where those fiddly sprung segments come in.

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Well parts are in the process of cleaning and inspection and replacements identified. So I shall use the gap in narrative to do an "inquest". Why did it fail? This is an important part of the process for me. First off, you get to recognise your own work even years down the line. You also, if you see it often enough recognise other people's work and I'm pretty sure who last saw the inside of this machine. I'm not in the business of badmouthing another blokes work not least because I am fallible too, so I shan't say more on the subject.

One of the best indicators of what's been going on is the condition of the brushes. In this case wear has not even spread across the full width of the contact surface, the brushes are not yet worn in so failure has been extremely premature. The drive end bush on these is white metal surfaced or more recently bronze. It should be lubricated by an oil soaked wick held in contact with the pinion by a spring. The spring was absent and only a small fragment of wick fitted. In consequence the pinion has picked up on the bush and was smeared with white metal. The bush is worn out and the armature has been in contact with the field pole shoes. There is extensive rust partly because the field coils weren't removed just the whole assembly sprayed over. Surface treatments on some components has been removed by buffing on a wire wheel and sealing O rings left out. In short, failure is due to sub standard overhaul. Shame on you matey!

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To give this some context. A new starter from the manufacturer is £1,214.58. A cheap exchange unit (at this point I'm staring at the ceiling whistling) about £300. Both these prices are ex vat.

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Field pole shoes. Two showing untreated rust and damage from armature rubbing. Two cleaned up with a coat of zinc plating flashed over them. This is a marine unit off a saltwater boat. Corrosion isn't defeated with a wire brush and wishful thinking.

IMG_20200206_113243.jpg

Edited by Sir Nibble

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