Le Tonkinois Varnish
B & D Murkin
UK main importers for
Le Tonkinois varnish
It is unlikely this motor would be used again so there was no real reason to repair it. However we decided to replace them for instruction photographs and practical ‘how to’ experience. Suitable bearings were found on Ebay May 2016 at £1.44 each post free. These were described as 626 ZZ 6mm Ball Bearing aka 626ZZ or 626-
Previous pages describe dismantling the motor to get to this point.
Click on images for better quality
This plate held the faulty bearing. The shaft was tapped out gently with a hammer and drift.
The bearing before oiling, very corroded and stiff. Oiling loosened it up so it rotated more freely but it still wobbled and grabbed and sounded noisy. Derek’s comment "Square ball bearings", Mine "Knackered"
Driving the faulty bearing out with a drift and a club hammer. A very light tap and it came out very easily.
The housing and faulty bearing.
After the ease of removing the first bearing we unsuccessfully tried this method to remove the second.
It would not be a good idea to lever on the commutator. There was a circlip between the bearing and commutator, it was in the way but it removed easily.
With the circlip removed the bearing could have been removed by using a suitable sprocket puller. We used an alternative method.
We improvised with an old offcut of angle iron. It took several hard blows with a heavy 4 lb club hammer before the shaft finally moved.
The lefthand circlip on the shaft broke when removed to do some cleaning so we replaced both of them. We decided not to use abrasives on the shaft as we wanted to keep the shaft tight in the bearings. The commutator was in good condition so left alone.
Two new bearings and circlips. Bearings dimensions 19 mm outer diameter, 6 mm inner diameter, 6 mm thick, £1.44 each post free Ebay. Circlip 5 mm, £1.05 for pack of 10 post free Ebay.
The bearing tapped easily into the end plate. A piece of wood was quicker than searching for the length of steel rod we normally use as a large drift. The shaft had already been tapped into the other bearing up to the circlip. Despite the force it originally took to remove the old bearing from the shaft the new one drove in with very gentle taps.
The shaft partially tapped into the end plate. Note the bearing is not held rigidly in the plate, this allows the far end of the shaft to move side to side by about half the shaft diameter. This is not due to wear in the bearing or housing but can easily be mistaken for it. The disassembly page shows the shaft fully inserted.
Shaft clamped in vice.
Four offcuts of 6 mm mdf. The lower ones fitted between the rotor and end plate which held them in place. The upper ones increased the spacing. Other spacing material would be just as suitable.
Inside view of motor body, brushes held in place by the wires. I checked the wiring and electrical connections were clear of the shaft and motor body.
Top view of motor body, ready to be fitted onto shaft.
Shaft refitted, the magnets then held everything together. The shaft was rotated to check it was reasonably free.
Because the brush plate had been refitted I checked the straight edges reveal equal amounts of the magnets below. I inserted the fixing bolts here temporarily just to show where they pass the brush plate.
The end cap had two spacing washers, the bottom one flat, the top crinkly. I made sure they remained in the recess whilst fitting the cap.
The cutouts had to be lined up with the brush plate before the end cap was tapped fully home into the body. The endcap holds the brush plate securely in position so the plate retaining lug which broke off during earlier rotor assembly trials was not important.
The mdf prevented shaft going all the way into the motor body. This stopped the bearing pushing hard against the brushes so they could be eased outwards onto the bearing.
The mdf only allowed the shaft into the body far enough for about 1 mm of the brush to rest on the bearing, slightly thinner material might have been better. I also tried a long wooden wedge which gave variable thickness and worked well. The shaft moved sideways when the mdf was removed dislodging the brushes so it took a couple of attempts before everything went together ok.
Refitting the shaft into the motor body took a little patience.
Nearly ready for fitting the two securing bolts. I forgot the upper plate holes are not symmetrical when taking the photo, the plate should be rotated another 180 degrees. Tip for fitting bolts: Hold the motor vertical above a light background as shown and look through the upper hole. Rotate the rotor plate until the lower hole is visible and aligns. Keep the motor vertical and insert the bolt. It may take a few attempts before the bolt will screw in. Repeat the procedure for the second bolt.
The reassembled motor with plate in correct position. The permanent magnets caused a drag on the rotor so the shaft did not spin as easily with no electrical power applied as modern motors with field coils. Motor was tested on 12v to check everything was working, current drawn about 2 amps. Definitely a lot quieter than before. There was no cooling air flow so the test was kept short.
The impeller was fitted at this stage but it would have been better to do it later after the fan segments nut was tightened. The impeller was positioned with the alignment marks made before it was removed. A block of wood protected the impeller as it was tapped onto the shaft. There is no guarantee it will still be balanced but if fitted in the wrong position it could be made much worse. A small imbalance usually makes no difference. Larger imbalances could cause vibration and shorten the life of the bearing.
There was nothing to prevent the impeller being driven too far onto the shaft so we did it gently in stages measuring the length of the exposed shaft. We had not measured it before removing so used the same 9 mm as the second motor.
The stepped spacer fitted onto the shaft with the smaller diameter closest to the motor. The combustion port could be mounted back to front, the fixing screws must fit in recesses. It was also possible to fit in 3 positions which determined where the motor wiring would be on the assembled heater.
Burner and blower ready to be bolted together.
Reassembly should be straightforward.
One of the smaller fan segments plus the spacer in place. Next the lugs on the larger segment located into recesses near the holes. This segment does not rotate with the shaft. The second smaller segment fitted on top. A nut and washer locked the fan segments in place. Photo taken before orange impeller fitted.
Fit a new gasket when joining, failure could leak dangerous fumes into the blown air supply. New gasket available from dealers for under £3 +pp but not bought for this burner as it is not expected to be reused.
Initially I considered freeing the wires where they pass through the hard grommet in the metal body to give enough slack to allow the brush plate to be fitted after the shaft. This would have made the task far easier but the risk of damaging the wires was high and it might be difficult to ensure the connections are clear of the body and commutator. You can do this if the other methods fail.
The bearing and commutator are the same diameter so once the brushes rest on the bearing they can move onto the commutator. The brushes are spring loaded and easily come completely out of their guides, fiddly to get back without the shaft, extremely difficult with it partially in place. The photo shows one out, the end of the spring is protruding and just visible. I used some thin copper wire about 1 mm diameter to hold the brushes in place while fitting the shaft. Wire is not critical, it just needs to be strong enough to hold the brushes. The bearing diameter is only about 1.5 mm smaller than the hole and there is not enough clearance for the bearing to pass through without pushing the wires out of the way but the wires often kept the brushes in place long enough for them to rest on the shaft or the bearing. Tip -
During assembly as soon as the shaft entered the body the permanent magnets aggressively grabbed the shaft to the side. By rocking the shaft it could be pushed further in. Then the second effect of the magnets kicked in, they pulled the shaft very forcibly into the body, just as if it was on a strong spring. I held the brush plate in position and tried to get the shaft to pass between the brushes. It was impossible to fully control, all that could be done was to slow down the movement. One or both of the brush retaining wires was always displaced by the shaft. If the brush came out completely the shaft was removed before making another attempt. If the brush rested on the shaft the brush could be pulled back and the shaft allowed to move further. Once both brushes rested on the bearing the shaft went all the way in. I took care not to force anything against the brushes to avoid damaging them. Success rate was low, only about 1 in 10 attempts succeeded. If this had been a working motor I would not have reassembled it more than was necessary. This motor is unlikely to be used again so I could repeatedly try alternative methods. During initial tries I was sometimes successful this way but after a large number of tries to find out better methods the brush plate became looser each time it was knocked out of position and then one of the retaining lugs broke off and it became almost impossible to hold in place during shaft replacement with this method. The lug is not important for the assembled motor. The brushes were also showing some chipping, not enough to cause a problem but not desirable.
After quite a lot of experimentation I found the easiest way was to hold the shaft in a vice and to use pieces of wood or mdf etc to prevent the shaft being pulled fully into the body. This had a 2 out of 3 success rate.