Starter motor problems.

[davidwheeler]

1. A new distemper has affected my starter motor.    I have just fitted new ratchet, spring and cog and put the starter on the car today to be greeted by a skizz as the ratchet slipped.  I looked at it all ways and even got the idea that the ratchet had been made back to front!  Experimentation with all possible combinations of other ratchets, springs etc. disposed of that idea.  I now have a starter on Boot with all new parts and a fully charged battery which engages with the flywheel but does not turn it, merely stays still while the shaft spins and the ratchet slips.  I have fitted the ratchet to the anterior end of the spring so that the spring drives the ratchet.  This is exactly the same, geometrically, it seems to me, to having it at the posterior end so that the ratchet drives the spring but does it make a difference?   The setup works perfectly on the bench under hand power and worked fine until two weeks ago when I lost the nut on the end and subsequently the spring ratchet and gear (horribly expensive!) which necessitated taking it off and fitting new parts.  It does not work any better with an old and slightly loose gear either.

2. My other starter fails to engage at all, merely bouncing forward and then retiring to spin uselessly.  I presume it is induced magnetism that throws it forward.  The commutator, brushes etc are all in excellent condition and there is no sign to the eye of burnout.  Any ideas?

[davidwheeler]

"When you have eliminated the impossible whatever remains, however improbable, must be the truth."    So I went out to look and, yes, the starter motor is running backwards.  I have reversed polarity on a dynamo so I imagine a similar procedure will work for a motor.  Tomorrow will tell.

That still does not solve problem 2.

[JohnMillham]

Bosch starter motors for Lambdas can be made to run in either direction, depending on the car to which they will be fitted. I bought one of mine in France, where it came from an Alfa Romeo which ran the wrong way for use on a Lambda, so I converted it. Bronze brush holders, pinions, springs and ratchets are available from the Lambda Consortium. I imagine the consortium will only stock the appropriately handed ones for Lambdas, so I would be inclined to check that your springs and ratchets in particular are the correct ones, as they will only work in one direction. i expect you realise that the idea is that the initial voltage throws the pinion into mesh with the flywheel teeth, then the full voltage is applied to turn it with more force. Once the engine fires, the ratchet and spring will allow the pinion to free-wheel to avoid damaging the starter motor. Regards, John

[davidwheeler]

Ow, my brain hurts.  I have spent a most frustrating day, flashing field coils and changing armatures, all to no avail.   The two motors have slightly different arrangements so I cannot change the field coils. You have just added to my frustration by saying "...so I converted it"  and not said how!!   This is an original Lambda starter motor (with new brush holders etc.) that worked perfectly well until a week ago.  Unless you come up with the goods tonight, John, I shall have to go down to my local old fashioned auto electrician tomorrow which is an admission of failure but also a learning opportunity.

(Apart from that, grandmothers, eggs, mutter mutter.)

Any ideas about the other motor which will not engage properly?  I have checked the field coils and they seem OK and fitted the armature from the other motor and that does not help either.   Might it be something to do with that curious switch worked by its little solenoid with its lever arrangement underneath?  I am not sure what is the purpose of the lever.  The armature flings forward but without any great conviction and not enough to engage the pinion with the flywheel.

[JohnMillham]

There are two types of Bosch starter motor fitted to Lambdas, each of which can be reversed. I'll look out some photos and report back. I recall that there's an arrow somewhere to tell you which way round it's going to work, but I'll have to take a look at one to refresh my memory. I must get into the garage first and compete my head gasket renewal this morning, as it blew on Thursday on our way home from the Phoenix lunch!
 Regards, John

[davidwheeler]

John has solved this one for me see the photo of the reversible strip (so that is why it is symmetrical) the arrow of which shows the direction of rotation.  Photo John Millham.
I'll also post this on the technical information thread.

[simonandjuliet]

Don't you have a starting handle - surely it would be easier ...... Only joking, the quality of the parts is amazing, real hand-built machinery, heavy weight materials - all but forgotten nowadays

[davidwheeler]

I have been wielding it regularly.      John has sent further information on the motor which should enable me to sort  out the engagement problem.  I have posted it on the technical data thread.

[davidwheeler]

Well now, I had both starter motors on the bench, the one that works and the one that didn't.    I looked for the holding field coil that, according to the literature (see the technical data thread) should be in parallel with the auxiliary coil but connected to earth not to the brushes and found no evidence in either motor.  The theory is that the aux coil moves the armature forward, the main coil is then energised by the switch when it is released by the pawl and trip lever and the armature is held in place by the holding coil,  as the reverse emf generated in the field coils by the armature reduces the magnetic pull.   As there is no holding coil in the Lambda version of the Bosch starter motor, it must be down, thought I, to fine tuning of the solenoid switch.  So, I filed a bit off the bottom end of the copper yoke until the armature had had a good chance to extend before the pawl released the trip lever that allowed the switch to send full power to the main field coil together with a little adjustment of the bend in the lever itself.
It worked!

[davidwheeler]

But, unfortunately, not very often.  Further study on the bench revealed that the pawl was releasing the trip lever when the armature had only advanced 15mm and not got a proper engagement with the starter ring.  (see P 449).   I contemplated making a new pawl and then realised that all I needed to do was take off the trip lever, build up the lower part of the aperture for the pawl with weld and file it so that the bottom had about 2mm added to it and trial and error until the pawl did not release the trip until the armature had advanced some 25mm.  I then hardened it again and installed it and this time it works every time!  It is necessary to be sure that there is free movement of the yoke on the Bakelite mounting and that the upper end of the yoke engages fully whilst the lower end is held off from contact until the trip lever is released, a matter of filing the yoke and bending the trip lever slightly.

[davidwheeler]

Here is a picture of the mechanism.  Note that this is from an VIIIth series car, the VIIth is slightly different (and rather more robust looking).

[davidwheeler]

Ooops