Classic UK Minitrix Models  -  Black 9F

Having 6 axles for the loco and 3 axles for the tender provides plenty of pickup points for electricity, which usually means that this loco is one of the most steady over points, round curves and over dirty track.

In fact, there are 5 positive (right) side pickups and 6 negative (left) side pickups.

Front bogie:  Negative pickup
Front 3 drive wheels - Each has a positive and a negative pickup on the right and left sides respectively.
Tender. The front and rear axles provide positive and negative pickup on the right and left sides respectively.

A clear view of the pickups on the left hand side of the loco.  Note that the contact on the fron wheel is not made.  At some point the copper strip has been bent upwards, and only the centre wheel is connected to the negative (left) rail.  The rear two axles do not provide electrical contact, they have traction tyres fitted, although there may be occasional contact with the flanges, through the axles and the chassis.


Here is an overhead view of the two copper conductivity strips.  Note the contact points for each wheel, and the extra contact at the front of the loco for the positive end of the light bulb.  This picture also shows the red lead from the choke coil connected to the top brush of the motor.  If the motor is replaced upside down, this wire will be at the bottom, and the engine will run backwards when it should be moving forwards !

The cheese-head screw next to the red wax which coats the choke coil, provides the main connection between the left hand copper strip (negative) and the chassis.  On some locos, (like this one), this is the only secure connection to the chassis.

Here is the copper strip being lifted out.  The black wire is the positive connection for the right wheel pickups in the tender.  The loco should run quite happily without this, although it may stutter over points without the extra pickups provided in the tender.
Here is a different 9F from the right hand side with the circuit board in place.  Black wire goes to the tender.  The green wire is different, and is explained further down the page.  Desoldering the strips is easy, as soon as the solder melts, the strip spring away (or up) from the circuit board.  Re-soldering is a bit more awkward.  You need one hand for the soldering iron, one for the solder, and another to hold the screwdriver which holds the vertical copper strip in its place until the solder cools.  Don't let go before the solder has set properly, or you will get a dry joint, which will not conduct electricity properly.
The tender, without its weight.  The rear of the tender is to the left of the photo.  Note the contacts on the wheels at each of the four 'corners'.  The tab at the rear has a hole in it, but has never been soldered.  This tab should stick up slightly.  It makes contact with the tender weight, when the weight is clipped into place.  (Note the 4 plastic clips sticking up from the chassis.)  The weight provides electrical continuity, as described in the section below.  The right copper strip (bottom of photo) has a soldered tab sticking straight up.  This should have the black wire attached to it, which protrudes through the hole in the metal weight.  A plastic sleeve prevents any chance of this tab and wire making contact with the negative weight.  Note the wire emerges from the tender below the coal shute  at the front of the tender.
Underneath the tender which is attached to the loco.  The loco is on the left in this picture, so the negative (left) side of the loco is at the top of the photo.  You can see the clear plastic insulation on the right hand wheels at the bottom of the picture.  There is a wire spring which provides the electrical continuity between the loco body and the tender weight.   The spring contacts the joining screw, although in the models that I have, the screw has a shoulder and doesn't tighten onto the eye of the spring.  You should make sure that the electrical contact is sound though, parts have been known to have been painted where electrical contact is necessary.  Even when brand new.  The open end of the wire is sprung against the screw thread which protrudes from the bottom of the tender weight.  Grahame got in touch about a problem he was having.  His 9F would work fine when going backwards, but was very erratic going forwards.  The problem was traced to a poor electrical contact between the eye of the spring, and the middle joining screw which has accumulated a load of muck over the years.  He managed to establish that electrical contact to the tender was broken when the tender and loco were pulled apart slightly, but contact was restored when pushed together again.  Cleaning middle join solved the problem.
The connecting bar between the loco and the tender is articulated, having 3 pivot points.  The pivot point at the loco end can be seen on the photo opposite (left hand end), and is unlikely to cause a problem, but if the loco has been stood for a number of years, you may want to check it out.  A similar arrangement provides the continuity at the right hand end for the front bogie.
The front bogie has a negative (left side) pickup from the copper strip on the axle.  This is transferred to the chassis at the joint shown on the right hand side of the photo in the section above.  These bogies are actually from a 2MT, but they are identical to the one for the 9F and Evening Star.
For completeness.  The motor, brushes, brush housing, springs and brush caps.
As promised, two different variations of the wiring for the 9f.  On the left, the green wire connects the left hand pickup strip to the bottom brush cap of the motor.  In the photo underneath, there is no green wire.  The bottom brush of the motor picks up its negative connection by the sprung tab on the brush end cap pressing against the chassis.
No green wire connecting to the bottom brush cap.  Left hand contacts not touching the front two wheels, spring tab on bottom brush cap is touching the chassis, but the chassis is painted.  Surprising that this loco runs at all really !
  Worth checking.  The boiler weight is screwed to the chassis with a long brass screw through the loco body.  The two little studs at the rear should not make contact with the copper strips - particularly the one on the right !  Normally it will not do this, but if the contact on the middle wheel has been bent up slightly .....
Please excuse the photos.  Looks like my lens needs a clean.

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