Servicing leaflet

Repairing and Servicing the No.1 Clockwork Motor

WARNING: Please be aware that clockwork motor springs are highly dangerous if released uncontrollably.  The use of these instructions is at your own risk, and no responsibility can be accepted for any damage or injury caused.  Do not dismantle any clockwork motor unless you feel confident to do so, and always wear safety goggles.

Refurbishing and Assembling the No 1 Meccano Clockwork Motor by Graham Jost

These notes are intended to assist in refurbishing the broken spring of a No 1 Meccano Clockwork Motor, the usual reason for its having died, and the subsequent reassembly of the motor. There is more than one opinion as to how to best deal with the spring. I detail below the method I prefer, and use.

Broken spring

Recovering a broken spring
The photograph shows the pierced end of an intact spring at the winding spindle. The elongated hole fits over a matching retaining pin on the winding shaft. The spring usually breaks through this attachment hole, which is pierced near the end of the annealed inner inch or two of the spring. In this scan you can even see the demarcation between the annealed section, left, and the tempered part to the right. I cannot now recall how this particular severed example, with its intact hole, came to me. I must be suffering from Oz-pollies or Oz-tallpoppies amnesia.

Note: It sometimes happens that an inch or so of the remaining spring at its inner end is still annealed - judge this by the difference in temper colour of the steel, or by the ease or difficulty in drilling. In this case you can thank Binns Road's supplier for being so cavalier about how much of the spring has been annealed, and omit reference to the next paragraph. Otherwise proceed as follows.

First lever the innermost 2/3 or so of the coil of the spring out of its plane and retain thus using a suitable piece of metal sheet or plate slipped between the out-of-plane coil and the rest of the spring - the deformed assembly will be found to be quite stable. Next, using a modest gas torch, play the flame over the end 1" or so of the spring - the out-of-plane section - to anneal the metal. The purpose of the metal plate is to prevent the flame from accidentally reaching the tempered part of the spring, and to facilitate localised heating. Heating will take only seconds, and the change in colour of the heated metal will readily be seen. It is totally unnecessary to heat the spring to red heat. Allow to cool in air - and certainly do not quench. This process is necessary to anneal the inner part of the spring to permit the drilling and filing to shape of the hole as shown above.

Centre-pop a dimple in the centre of the width of the spring about 3/8" from the end, and then drill a 5/32" diameter hole. (This is easier said than done - you will need a bench drill though). Use a fine round file to elongate this hole to achieve the shape shown - take care not to impinge on other parts of the spring while you are doing this. Clip the broken end of the spring to approximate that shown, using tinsnips or aviation shears.

As filing of the hole progresses, check its fit over the retaining pin on the winding shaft at intervals - the head of the pin must be oriented with its long axis at right angles to the shaft. When finally correct, assemble the spring onto the winding shaft, locate and fit over the pin, rotate the pin by a quarter turn to lock the spring in place using needle-nosed pliers, and relax - Phase One has been successfully completed! Make quite sure you have spring and winding shaft assembled correctly - check with the assembly drawing above. I cannot resist curving the free end of the spring at the spindle around its adjacent surface. I suppose this must happen on the first full winding anyway, but I prefer to do it now - needle-nosed pliers required again.

Coiling and containing the spring, and inserting into the motor
Note: A deal of sensible caution is required in carrying out the following. It is also essential that you wear safety glasses/goggles.
Grip the square section of the winding spindle vertically and firmly in the vice. Wind the spring by rotating the free end clockwise (looking down) around the fixed winding shaft. To do this, insert a suitable screwdriver (I use one with a 3/16" diameter, 6" long blade) into the loop of the free end of the spring, and wind the spring about eight (8) full turns - be sure to contain any tendency for the loop to open out. Then insert the end of the screwdriver blade firmly into the slightly open vice jaws to retain the spring in this partially wound state. Take a 10" length of soft iron wire - I use 18-gauge (0.048") - and pass around the spring, twisting the ends together to retain same, the join being made at the loop end of the spring - where the screwdriver is. Make sure the wire is as central as possible, side to side, around the spring - we don't want it flying off at some future stage. Tighten the twist somewhat, but try not to break the wire by virtue of excessive exuberance. Now, retaining a firm hold on the screwdriver, release it carefully from between the jaws, and carefully allow the spring to unwind to take up its natural state within its wire constraint - this will be about two full turns. Remove screwdriver. The assembly may now be removed from the vice. Apply a little grease of your choice to the winding mechanism on the surface of the main gear - you may never get this chance again! Assemble the unit to the sideplate containing the pillars, with gear closest to sideplate, having first slipped the longer spacing collar on the pillar over which the looped end of the spring fits - see the assembly drawing below. You should also now be able to locate the winding spindle into its bearing on this plate with little tendency for it to jump out. Phase Two is now complete - and the rest is beer and skittles!

Motor assembly
There is little to add here beyond what is indicated by the assembly drawing. After balancing all captive gears/spindles in place on the (horizontal) pillared sideplate, I begin by attaching the other sideplate with the two screws at the spring end - loosely - several turns. Then squeeze the sideplates together over the brake lever pillar, and insert its screw - but only a turn or two. Insert the fourth screw loosely. The distance between the sideplates is now narrowest at the spring end, and a maximum at the governor end - this (slight) taper allows for a sequential insertion and securing of the spindles in place, beginning with the first driven gear, and ending with the governor spindle and its driver. Tighten each screw a little at intervals to hold inserted spindles in place, yet allowing still-free spindles to be manipulated into place. Once all spindles are in place, all screws can then be fully tightened. Just one note of caution - the top sideplate (right sideplate above) has a projecting lug whose purpose is to limit the extent of unwinding of the spring. Make sure that the mainspring is clear of this lug when attaching the sideplate.

Having assembled the motor, insert the final output drive shaft and its pinion - parts 4475 and 4607 above. With the brake lever applied, wind the motor sufficiently to release the load on the wire containing the spring. Snip the wire and remove. Apply a little engine oil to all bearings and pinion surfaces. Release the brake, and enjoy the results of your handiwork. Hey presto - another long-defunct motor has been revived!

In conclusion
The notes above assume the refurbishment and assembly of clean components. Essential cleaning should obviously first be carried out on parts presenting themselves otherwise. Any damaged gears should also be replaced before assembly. The pinion on the first driven gear is a prime candidate here - part 4597 above.

The above may appear long-winded, or even pedantic. I've simply tried to include all aspects as I've experienced them - skip what you feel is unnecessary for you. And of course even the simplest actions sometimes defy concise description!


The following notes on mainspring repair were written by Thomas D. Smith:
Disassemble the motor, making careful WRITTEN records of just which shaft goes in which holes, and which way the gears are on the shafts etc. You will find that the mainspring is broken at the inside end around the winding shaft. One must retrieve the broken fragment(s), and carefully observe the means of attachment to the shaft, including the shape of the spring. This involves a bend in the end of the spring, and a hole in the spring. Since the metal of the spring is highly tempered, one must first make the last 1 to 1 1/2 cm of the spring soft, so that it can be bent and drilled. Heat the end of the spring with a match or a candle, and let it cool slowly. (A couple of tries may be necessary to get the right softness, but it's a long spring and if you lose a couple of centimeters it won't matter a bit.) Then drill a small hole through the soft metal, and file with a small jeweller's file to duplicate the shape of the original (probably doesn't need to be a perfect match), then bend to duplicate the shape of the end of the original. Then put it all back together! This is the tricky part. It can be done. Some suggest winding the spring and holding it wound with tape and/or string. I have found that unnecessary, as one can leave it unwound , assemble it with the long spring attached to the winding shaft but unattached on the outer end, then just winding it around and around until the outer end catches at its usual attachment site. (I guess it needed to be hanging out from the right location to accomplish this, but it makes an elegant last manoeuvre).


The following notes on reassembly were provided by Robert Simpson:
I recently repaired a reversible clockwork motor. The most important thing is to leave the spring disconnected from the outer post until everything else is back together. Put all the cogs in the right place on one of the plates and then loosely bolt the top plate on (so there is still enough room to move the cogs around). The technique is then basically to gradually tighten up the bolts while lining up the cogs with the top plate. With some experimentation, you should be able to click the cogs in the top plate one at a time (the exact order will depend on your motor and what order you tighten up the bolts). When everything is done, wind up the motor until you can push the end of the spring back on the post.

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