B & D Murkin
UK main importers for
Le Tonkinois varnish
Flexidisc sander
Disassembling D1L heater Blower unit
The D1L servicing page shows two heaters being taken apart to get this point.
On most services the blower unit will be ok and not require dismantling. As a precaution check when disassembling that the parts are aligned as shown in the photos. Both of our D1L bodies came from the same source and assembly mistakes could have been made before we got them. We already know one of them was a 12v model in a 24v case so some caution is advisable.
Take care removing the three fan segments which are made of thin metal and are easily bent. Prising very gently with a small screwdriver at various points moved the segment. Once the segment had enough freedom to rock it was then gently manipulated until it released.
Disassembling the D1L blower motor
Blower motors should only need dismantling if they are faulty. We wanted to find out why this one was very stiff and to see if there was internal water damage. Before starting make alignment marks on the shaft and impeller so they can be reassembled in the same position. There is no guarantee it will still balance perfectly but it could be a lot worse if not aligned as before. Also measure the length of shaft protruding through the impeller. Alternatively photograph or measure the gap between the impeller and the motor flange. When driving out components a light tap with a heavy hammer is far more effective than a heavy blow with a light hammer. Our methods may sometimes look a bit Heath Robinson but we know our readers often do not have specialist tools so we often deliberately choose simple low cost solutions.
Fixing nut is rusted with deposits on it.
Remove the nut, washer and first fan segment. This is shown face down revealing the segment rear side.
There is a noticeable water level line on the plate. This shows prolonged partial immersion. Hold the orange impeller while unscrewing the fixing nut.
On this D1L the spacer was very tight and needed grips to work it loose. On the second D1L it removed a lot easier.
Remove the second segment. I used a small screwdriver inserted from the centre but be extremely careful to avoid bending either the edge in contact with the blade or the opposite edge. Again this is shown face down.
Remove the third segment.
This is identical to the first one.
Remove the three screws securing the combustion air inlet.
Heavy water deposits on this motor end casing. The two T shaped bits in the recesses are the ends of bolts holding the motor together.
Separate the combustion air inlet port.
This is shown face down.
The second fan segment is clipped in and does not rotate.
The final stepped spacer was extremely tight. It took a lot of force to remove, the teeth marks from the grips are quite deep. The only reason for its removal here was the motor was still very stiff and would have to be dismantled. The spacer on the second D1L was also solid so was not removed.
End of the motor after some mechanical cleaning. The bright ring visible round the base of the shaft is the outer edge of the bearing.
Page 2 continues with replacing the motor bearings
The orange impeller is a push fit on the shaft. Holding the impeller and hitting the end of the shaft hard with a light hammer did nothing except leave a mark on the shaft.
Two scrap plywood offcuts, the left one with a 73 mm hole which was a perfect fit to support the impeller. Part depth slots were an initial experiment, full depth better. The second 76 mm, a more common hole cutter size, was a looser fit but would support the outer part of the impeller ok. Definitely not quality workmanship but it was a very quick trial and successfully did the job.
The impeller needs solid support so it does not jump when the shaft is hit.
Photo was taken at an earlier stage.
What looks like damage to the tabs near the edge are manufacturers adjustments balancing the motor. This is why we marked the impeller and shaft before disassembly.
More evidence of immersion on both the impeller and motor casing. The two holes are for ventilation. There is a small notch on the edge of the end casing, no idea what for.
Unscrew the two fixing bolts and pull apart. The strong magnets tried to pull the rotor back into position. Once the end of the rotor was clear of the brushes the magnets pulled the rotor sideways and grabbed it. Photo taken earlier before impeller removed.
The two 75 mm bolts with the special screwdriver bit we used to remove them.
These bits are probably listed on Ebay as security / tamperproof bits
Plate and rotor pulled out complete with the far end bearing. Rotor had less water damage than we expected.
Plate and rotor separating from motor casing.
Bricks on a paving slab give a good solid base. The bricks were stood on end whenever more clearance was required. It only needed a light tap with a heavy club hammer via a drift (metal rod) to move the shaft. Using a Workmate might look simpler but that bounces when hit so much more force is required.
Brushes in very good condition, hardly worn. Springs push the brushes inwards onto the commutator. The braid is joined to the filter coils with crimped connections. Brushes measured 7.8 mm wide, 6.2 mm deep, 11 mm long. There was sufficient free play for brushes to have originally been maximum of 2 to 3 mm longer but I suspect very little wear. The filter coils reduce electrical interference.
The permanent magnets had deposits which rubbed off with a coarse cloth. We avoided using abrasives as abraded metal would stick to the magnets. Oddly many parts inside the motor showed no signs of immersion.
Although this bearing looks in bad condition it rotated freely, it is the one at the plate end that was very tight. The commutator was in good condition, the striations were not deep. The thickness of the metal on the commutator will come as a surprise to anyone used to modern motors.
Two shim washers remained in the end cap bearing recess.
One way to remove the end cap is to gently drive a drift onto the lip between the two magnets. Take care to avoid the black brush plate.
End cap with the two shim washers which were fitted under the bearing, one flat, the other crinkled to take up end play. Rust was only on the surface, looked far worse than it was.
Motor body and the brush plate under the end cap.
Brush plate lifted up for photo. The wires were tight and we had to carefully create some slack. We also found removing the plate loosened it so it had a tendency to be pushed out when replacing the shaft. This was not a big problem but it would better not to move it if it is not necessary. There are two thin protrusions on the plate which fit under the body lip. Take care when replacing plate not to damage them.
