Bomb starter motor dismantling/rebuild

[Lynx]

Good afternoon!

 

I'm trying to dismantle my Lucas "bomb" type starter motor M4185 V164. The motor turns fine and pushes the bendix out but fails to turn the engine. I think that the coupling, (sleeve and rubber drive item#57 in the Moss catalogue) must have delaminated and I need to replace it.

I've never seen a starter like this before and I can't dismantle it. I've removed the bendix gear OK but I can't get any further. My "Autobooks" manual refers to a pin and at nut that I don't seem to have. I've attached some pictures with where I've got to. I cannot find how to remove the collar (arrowed). I wonder if it has a circlip inside the collar but I can't actually see one nor see how to get at it if it is there!

 

Once dismantled I'd appreciate any tips on the rebuild please.

 

Any suggestions most welcome.

 

Many thanks

Regards

Andrew King

Swanage

TR3a TS75982L

 

[Rodbr]

if you do a Google for "lucas bomb starter motor parts" and about half way down the page there is a paragraph "images for Lucas bomb starter motor parts.

Cycle through those and I'm sure you will find what you need. Pretty sure that the section remaining needs to come off the shaft. Check the replacement and you should see what is replaced.

 

Did you try it before dismantling to see if the Bendix kicked out?

[BlueTR3A-5EKT]

Yes probably it is the ring clip type holding that plate on the shaft. The other type is a nut. ( LH threaded from memory) if it is a nut it has two flats on it.

You need to compress the items on the shaft toward the comm end. I have a long screwed bendix compressor with a plate to sit the end of the shaft on.

With the rubber drive compressed toward the comm end you can fiddle the clip out.

Cheers

Peter W

[Lynx]

Evening Peter and Rodbr

Thanks for the suggestions. I found an image of a "naked" spindle on an Ebay advert which clearly shows a groove for a circlip. Made an Heath Robinson compressor this afternoon and have managed to dismantle the drive units; the collar was held with a hidden circlip. Appears that the sleeve and rubber coupling drive has delaminated from the shaft so throws the pinion out but then just slips round rather than turning the ring on the flywheel. So a replacement coupling sle3ve and rubber drive is called for.

 

Thanks again

Regards

Andrew

[Lebro]

This is the usual failure mode for these motors.

I replaced several of these rubber drives in the 70's

One failed on OFU while on Honeymoon in south England / Wales.

Had park on hills every day, & leave engine running while on a chain ferry in Dorset !

 

Bob.

[Lynx]

^{Thanks for the confirmation Bob - always good to have an answer from someone who's been there and done it! I know the chain ferry well it's just a few miles from me in Swanage and I use it most weeks. Now £3.50 a trip.}

^Andrew

[mleadbeater]

I dumped mine and fitted a modern geared starter unit, bit expensive but hopefuly worth it.

 

Mike

[Lynx]

Starter back in the car and all fine and dandy again! Thanks to everyone for their help and comments.

As I couldn't find any pictures of the disassembled starter on the web I'm posting this picture for reference in case it helps anyone in the future.

Andrew

[iain]

Picking up on this thread, I’ve dissembled a bomb starter, have removed the retaining nut on my version, slipped off the spring, but the final parts, arrowed in yellow won’t budge? Any clues welcome.

 

Edited February 1 by iain

[BlueTR3A-5EKT]

 Item arrowed red is probably threaded with a LH thread and the inner part is staked into a groove in the armature shaft,   Or it has a circular clip retaining it that will need the use of a bendix compressor to extract.     Only Lucas could come up with that!    Once that bit is off the silly rubber drive will slide off.  There is a bronze thrust washer in there somewhere too that breaks up.

Image of a NOS StanPart/Lucas starter bendix repair kit with both types of rubber drive retainer.   LH treaded and spring clip type.

The kit includes the bendix gear and the rubber drive plus all the drive washers, springs and other gubbins.   PM if interested as I doubt I will now need it.

[iain]

This is the stage I have got to.

Firstly I'm useless at electrical stuff. However the brushes look good, the armature looks to be little worn.

I've tried to follow the simple tests in the WSM. 

Checking the armature insulation I get a reading of 2.5 on the 20K scale of my meter when one probe is on the armature and one on the commutator shaft. Is this good?

If I check the field coils as in the WSM, I have continuity between opposing brushes which i guess is correct as well?

Finally I'm not sure how to test the insulation. Is this one probe on the power terminal and one on the outer casing( yoke?)

Also I appear not to have an "insulation piece" preventing the inter-coil connectors from contacting the yoke? 

Finally have a dropped a major clanger by not noting the positions of the pole shoes? :-(

Thanks in anticipation

 

 

[Lebro]

The biggest mistake may have been removing the field coils from the casing. They will be difficult to replace such that they do ot contact the spinning armature.

Regarding the insulation test, 2.5k is no where near high enough  but you may have just been measuring yourself ! If you were holding the probes onto the armature with bare fingers

Bob

Edited February 2 by Lebro

[BlueTR3A-5EKT]

I have a case with new fields fitted somewhere. Do you want me to go searching?

[iain]

Cheers Bob

No the reading was with me holding the insulation of the probes and touching the spindle and armature with each lead.

 

Umh...thanks Bob, good job its a practice :-)

Iain

 

Edited February 2 by iain

[iain]

2 minutes ago, BlueTR3A-5EKT said:

I have a case with new fields fitted somewhere. Do you want me to go searching?

Not sure yet Peter, I'll be in touch :-)

Iain

 

[stuart]

1 hour ago, iain said:

Not sure yet Peter, I'll be in touch :-)

Iain

 

Ian I have a complete working one here FOC if you want it.

Stuart.

[Lebro]

Me too !

Bob

[iain]

Cheers guys I might just be interested.

I have the following symptoms at present.

Extremely low speed cranking. Won’t start.

Tests completed.

Cleaned every terminal connection.

Tested battery, was at 70%, changed for a new one, no difference.

Bypassed the ignition isolator switch…no difference.

Bypassed the solenoid, by shorting across terminals, no difference.

Attached a supplementary earth from engine to battery….no difference.

The slow cranking has been developing for a while, now it’s terminal, not enough to start even with a jump start from a pucker battery/ starter.

So my guess is the starter rebuilt by Lucas in High Wycombe back in 1981 has had enough?

Any thoughts welcome, I’m not overly keen to buy a High torque job, but do need a reliable fix so Stuart or Bob might be getting a call for their offers :-)

Cheers

 

[BlueTR3A-5EKT]

1 hour ago, iain said:

Cheers guys I might just be interested.

I have the following symptoms at present.

Extremely low speed cranking. Won’t start.

Tests completed.

Cleaned every terminal connection.

Tested battery, was at 70%, changed for a new one, no difference.

Bypassed the ignition isolator switch…no difference.

Bypassed the solenoid, by shorting across terminals, no difference.

Attached a supplementary earth from engine to battery….no difference.

The slow cranking has been developing for a while, now it’s terminal, not enough to start even with a jump start from a pucker battery/ starter.

So my guess is the starter rebuilt by Lucas in High Wycombe back in 1981 has had enough?

Any thoughts welcome, I’m not overly keen to buy a High torque job, but do need a reliable fix so Stuart or Bob might be getting a call for their offers :-)

Cheers

 

First thing I would check is the length of the carbon brushes.   Replacing may revive it a bit.   The field coils get oil soaked or wet and the insulation breaks down.  New or re insulated fields is the fix there.    The bearings that support the armature wear.  The front in particular.  Renew both.   The commutator surface wears and goes out of round, skim on lathe to fix.

[Lebro]

Good tested & working Bomb starter motor (9 tooth for shrink on ring gear)  £50

    

 

Bob

[stuart]

Not cleaned but working fine FOC. with probably another for spares thrown in.

Stuart.

Edited February 3 by stuart