I've just stripped a 'bacon slicer' type starter motor that hasn't been used for some time, to clean and inspect it.

When I took the drive spring off the Bendix drive to release the drive dog, I found that the female dog (there's a joke waiting there) was quite separate from the rest of the quickthread assembly. Surely this isn't correct, because then all the drive would have to pass through the drive spring (and there would be no point having male and female dogs). And yet it seems unlikely that there would be enough power to have sheared the female dog off.

Obviously I'm missing something and would be grateful if somebody would explain.

Thanks in anticipation

John

PS. The thread on the quickthread is in very good condition, and the threads in the dogs for the set screws that secure the drive spring seem pretty good, too.

John I am far from an expert on this but my understanding is that the drive IS taken by the bendix spring and the function of the dog couplings is to provide a spacer to stop the bendix spring winding up and shrinking radially (think hourglass). The female dog should be atached to the quickthread but still be able to rotate on it. cheers Russell

Location: oz

Thanks, Russell. Quite a sophisticated design, then.

On closer inspection, in daylight, it's pretty clear that the collar of the female dog (more canine joke potential) has cracked. See picture below.

I'm wondering if it was originally swaged onto the end of the quickthread, in the groove, but that it engaged with the drive dog with enough force to crack it.

Not quite sure what to do now, but tempted to just put it back as is.

John if you can't locate a replacement female dog, an auto electrician should have a box full, what about a speedy sleeve from your bearing supplier?
I should have quit after the previous post shouldn't I cheers Russell

Location: oz

The same thing happened to the chummy on our trip through the Americas. If memory serves, David Williams of The Austineers either repaired or perhaps had new ones made. This component seems to take a hammering in service and at 80 simply gives up the struggle.
I hope this helps

Location: Devon for the week

Thanks again, Russell, and thanks Oxford Jack for making the picture a bit clearer. I've been thinking of ways of making a repair, but have to admit that I still don't fully understand its design or how it functions. When did the Austineers repair yours?

It's shown as part of the quickthread in the exploded diagrams, rather than a replaceable component, so perhaps I need to find a usable quickthread somewhere (which doesn't seem very likely!).

Anyway thank you both again for your help

John

Hi John,
The repair/replacement was done in 2013. I am assuming you are talking of the small part on the right of the picture, I think this was fastened to the quick thread with a pin, however I have been to sleep several times since then and my memory may be at fault. I do remember there was a deal of discussion at the time between Bradford on Avon and Lima, later the engine was removed to replace some piston rings and on replacing the starter one of the two fixing threads gave up the struggle. A ratchet strap around the starter motor and bell housing held until we got back to Blighty.
I believe the broken ring was welded and machined back to size and David supplied a newly manufactured item, which we used is beyond me.
Give him a call and enquire
Regards Kingsbridge Jack

Location: Devon for the week

John you are correct it IS swaged on but loosely so that it can rotate.
When the starter pinion engages with the ring gear it becomes momentarily stationary, but the commutator continues to rotate thus winding up the bendix spring. At this point the bendix spring shrinks in diameter clamping down on the 2 dogs. The driveline now becomes solid and the pinion begins to rotate( starts the car). If the 2 dogs were not in place the bendix would continue to wind up (hourglass) till it breaks. The dogs are always engaged but take no drive load. hope this is correct. am always nervous being in the company of experts, cheers Russell

Location: oz

Hi Squeak,

It is my understanding that your explanation is correct- the piece is only a spring support and does not play any part in the drive.

Cheers, Tony.

Location: Melbourne. Victoria, Australia.

Again, thank you Russell and Tony.

Finally, I've got the picture and in fact it should work just as well with the female dog being cracked and loose as it is. As the spring winds up, it will close the crack

John

I think the spring absorbs some of the initial shock as the pinion engages on the flywheel. Perhaps the spring is not as good as it once was.