Bacon slicer advice needed

[Keith Dobinson]

Just a thought, is everything going in the correct direction ?  It may have the wrong bends as they are not unique to A7s, vertually every car used that type but starters were mounted all over. My Lagonda has the same bender with a different rotation

[AllAlloyCup]

Thanks folks For all the helpful
ideas. I was hoping that someone else had had a similar
problem that might throw light on what’s going on.

I’ll have a look at the brush gear to see if that’s been miswired previously.

In extremis I’ll consult a local auto electrician.

I’m loathe to ship it to someone as it’s so bulky and heavy.

Regards

Bill G

Ps I do have a working starting handle so perhaps I should prioritise
the dynamo issues!!

[Hedd_Jones]

simple check. You know which way the flywheel should turn with the engine running. If the thing would engage. Would it turn the right way, or the wrong way. The answer points you to the problem

[AllAlloyCup]

Hi Hedd

At the starting handle the engine turns clockwise, looking from the cockpit the flywheel turns
Anti-clockwise, so the starter pinion needs to turn clockwise....
but it’s not it’s spinning anti-clockwise......

The opposite of what it needs to send the pinion along the spiral thread?

Still bemused!!

Regards

Bill G

[Ruairidh Dunford]

Can you post a picture of the actual motor?

[AllAlloyCup]

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Hi Ruairidh 

Here are some photos. It all looks in great condition and not had too hard a life.
Perhaps the position of the brushes may give a clue.

Not sure what the internal wiring comprises?

I could either: 

1.  move the brushes?

2.  Swap the wires to each brush?

Not sure what other options are open to me?

Regards

Bill G

[Austin Carr]

This forum may help:-

https://www.google.com/amp/s/www.mytract...ml%3famp=1

[Dennis Nicholas]

Hi Hedd

At the starting handle the engine turns clockwise,  looking from the cockpit the flywheel turns
Anti-clockwise, so the starter pinion needs to turn clockwise....
but it’s not it’s spinning anti-clockwise......

The opposite of what it needs to send the pinion along the spiral thread?

Still bemused!!

Regards

Bill G

Bill you have the answer already.
1. Since you say the pinion needs to turn clock but it is turning anti-clock AND the gear is flying in instead of out on the bendix to the flywheel then a. the bendix is the right thread and b. the motor is thus turning backwards.

Assuming negative earth I will call the main terminal the +
2. The motor action works with two different components: a. field coil windings  b. Rotor windings (with commutator segments that the brushes sit on)
a. electricity flows from + terminal which is connected to one brush and to one end of the field coils (the field coils are composed of a single length of wire from the + terminal wound round a former  and then on to a second coil on the other side of the motor body (both field coils are mounted on a solid separate pole piece) then connected to the motor body..ie earth or negative.)
b. The electricity flowing in the field coils makes one Field winding (and pole piece) North and one pole South......a magnetic field FORCE exists between the North and South.  (The field coil can be wound in two different directions so making a N or S pole)
c.  Electricity flowing from + terminal goes through the brush onto the commutator,  through one of the several windings forming the rotor to the commutator segment on the opposite side of the commutator and through the second brush and wire connection to the motor body: thus there is a loop of wire carrying a current which is lying within a magnetic field force.
d. That current in the commutator loop makes its own magnetic field FORCE which reacts with the N/S FIELD COIL force to move the commutator wire loop........direction of travel depends on direction of the N/S magnetic field from the field coils and direction of current in rotor windings.  Thus change EITHER N/S poles or direction of current in rotor windings and you change the motor direction.

c. To change N/S polarity and thus direction of rotation, take field winding connection from + brush terminal and connect it to motor body AND remove the other end of the field windings from the motor body and connect it to the + brush terminal.

ALTERNATIVELY

d. Take one brush connecting wire off the + terminal and connect it to the motor body AND take the other brush connecting wire off the motor body and connect it to the + terminal.

I know you say you have not touched internal wiring but as suggested someone else may have, including the field coils having been re-wound the opposite way round but with the same length of wire sticking out each end so they appear to be connected correctly to + and body because each length only reaches those terminations.

(To the knowledgable....yes I know electricity...i.e. electrons actually travel from negative to positive but that may just muddy the waters here  )

Sorry it seems a bit long winded (and maybe a bit simplified) but if you need any of it further explained just ask.

Dennis   (retired sea going professional electronics/electrical engineer)

[AllAlloyCup]

Thanks a lot Dennis for the time given to
write this note and explain how motor normally works.

I peered into the commutator end of the motor
and it all looks remarkably untouched, except
The two clamping screws which can be adjusted at the end of the casing.
I may try and move these, a simple screwdriver job to see it makes a difference
if the brushes touch differently spaced commutator segments.

The internal brush leads are relatively short so not easily
modified, plus I’d have to completely disassemble the whole motor
to see where connections go to the motor body.

Will let you know how I get on, thanks again for
everyone’s help with this daft problem.

Regards

Bill G

[Ruairidh Dunford]

The wire on this photo looks to be stretched a bit too much - has the end cap been replaced in the incorrect orientation?



Compare your wire and brush location to this...