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story of a repro TR6 wiper-motor, 14W type


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A member contacted me via HQ and offered me the new TR6 motor, that he had just bought. 

The story was that this had run a turn or so, but then blew the fuse and now was short-circuit.  He clearly thought this had destroyed itself in a major way.  I thought this unlikely, but by then he had bought another.

I don't usually rebuild these 14W types because there are lots of cheap new ones about.  But I offered to collect this one, on the basis that the forum could learn something from it.

It's one of those that come from India in a red box marked Lucas. It didn't actually take much to remedy it and in a little while the forum WILL learn something!

But right now I want to get this ready to pass on to somebody that can use it.  However the sweep-angle is NOT marked on the gear, like the original ones were. So in order to make sure this is correct for a TR6, I need some help from the forum.

I made some pencil marks next to the slider that guides the end of the wire-rack cable.  This allowed me to measure the distance traveled by the end of the crank-arm.  This is easier than trying to measure the distance of the crank-pin from the axis of the gear.

So could an owner with a 14W motor that sweeps properly,  tell me how much the end of the wire-rack moves, as the blades move from one extreme to the other.  You only have to get this to within a few millimetres or so, so that holding a rule next to it would do.

These motors are reasonably good and this one only had a simple manufacturing error.  But it amused me to find that the fit of the main-gear into the Oilite bush is pretty loose.  Technical term is "rattle-fit".

If I dismantled a DR2 made in 1957,  that had had a hard working life and the gear was as loose as this, I would extract the Oilite bush and fit a new one!

 

 

 

 

 

 

 

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Sounds like the motor was made by the same people as repro wheel boxes. 

A pair I recently saw had spindles that were more sloppy than the original 40 year old ones that were being renewed. 

Peter W

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This is the inside of the switch from the 14W motor, made in India.  I'd expect they are all rather similar.

I've removed the top two terminals because are just flat copper sheet that joins the wires coming out of the motor through to the plug on the cable harness.  These switches are glued together, so of course I had to break into this one.

So what you can see is:

1.  the earth terminal on the right, note how it runs right across the top of the switch.

2.  two contacts at the bottom, these are the self-parking-switch

3. on the left the plunger that is activated by the cam on the back of the gear wheel

Note that when the plunger is OUT,  as in the photo,  the two self-parker terminals touch. When the plunger is moved up by the cam,  the self-park terminals are pushed apart.  More exactly the right-hand contact (switch output side) is lifted away from the left-hand contact (12V supply).

But something else unexpected happens too.  The right-hand contact is lifted so that it touches the earth-terminal.  This connects the motor armature to earth and this provides a braking action to bring the motor to rest suddenly.  I doubt this is really required, earlier DR3 type motors don't do this. But this does introduce extra complexity and with this comes "points of failure'.

You see that on this example, the earth terminal DOES NOT run straight across the switch but "dips down", so that it makes an unwanted contact to the self-parking terminal. This is because it is BENT.  The second photo shows this bend was caused by a failed attempt to spot-weld the two parts of the earth-terminal.

I tuned-up this terminal with my nippers and all was well.

The third photo shows the cam on the back of the gear.   In order to change these motors from parking with the rack pushed OUT to rack pulled IN, you prise out the cam and fit it on the other side of the gear.  No fine tuning!  Just two fixed positions.

This motor, bought as being for a TR6, was parking OUT.  Unless I am mistaken this would be for a LHD car or maybe just wrong.

 

 

 

14W-riklog-4.jpg

14W-riklog-5.jpg

14W-riklog-7.jpg

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