Saturday, September 19, 2020

A fixed part for the E6 motor

Continuing the 'repair shop' treatment of the old Meccano electric motor; now the fixing-up of damaged parts. The base plate of the switch was damaged, with all four mounting pins broken off and a corner chipped. Not sure what the 'plastic' part is made of, possibly bakelite - notable is that it wasn't fully moulded, but at least partly machined. The studs were not moulded protrusions, but separate pegs that were inserted in drilled holes. Edit: or a previous owner tried to repair broken-off studs by drilling holes to fix with screws.

The pegs form studs that hold the switch in place when sandwiched between the motor side-plates. The holes in the side-plates are 3.2 mm diameter, or rather, 1/8". The holes in the switch base seem to have (had) thread, quite likely 6BA for mounting with screws. (Screw-mounting was used on earlier versions of the motor.) For repairing this motor, could have used new screws, but plastic pegs would be more correct for this 1933 Meccano motor, so scouting for 1/8" plastic pegs. 

Where to get black, rounded-top plastic pegs of 1/8" diameter?

It took me a while to realise, but there was a ready supply of 1/8" plastic rods in the house!

The Lego-brick is originally an English invention, and even today has a bit of a mix of imperial and metric dimensions. The base-dimension is 1/16" (~1.6mm), the wall-thickness of the brick. The height of a brick is 3/8", with the tile-bricks 1/8" thick - also the rods and antenna's are 1/8". Using the vast online marketplace for Lego parts, sourced a few extra of part 3957 (Antenna 1x4) in black.

The holes in the switch-plate needed drilling out to 3.2 mm. It's been remarked before that these motors are not precision instruments, the plate again confirmed this. The holes are not placed at the centre of the sides, but one set was significantly offset to the front. (Probably contributing to the chipping.) In the factory, a jig would surely have been used for drilling - this particular part must've been placed sloppily in the jig. (Or more likely - a wandering drill if done by a previous owner as a repair.)

With the plate clamped between the side-plates, the holes were drilled out without too much damage otherwise.

A short length of the rod makes a peg that was then glued in place. The chipped areas also built-up again with PVA and cut to create a reasonably flat surface again. Still visible as damage, but less glaring.

The pegs now jut through the holes and look exactly as the originals would have looked.

Next up to re-assemble and see about the windings.

Monday, September 14, 2020

A disassembled E6 motor

The Meccano E6 motor dates from an age when things were made repairable. It is mostly screwed together (of course - it's Meccano) and comes apart easily.

(The notion that you could make an expensive consumer product and explicitly design it so that it is near-impossible to repair was probably not yet mainstream.)

After disassembly and cleaning, this is what we've got:

The brass was only cleaned (soapy water) and not polished, except for the electrical contact surfaces. Decades of patina increase electrical contact-resistance and will slow these motors down or prevent them from running at all. Normally not visible, the switch-contacts are now brightly polished.

Nominally it is a 6 Volt motor, but by the look of the area around the brushes it may have been used at higher voltages, would not be surprising if a previous owner ran it at the 20 Volt that later Meccano motors needed. Not only does it look like it sparked fire, the commutator is also visibly worn down.

Now that they're clean, the fading of the paint can be seen very clearly from the difference between inner and outer face of the side-plates.

Were it not for the nicely surviving decal, these would be up for a re-paint. Maybe later - first to make it functional again. 

The bent lever of the switch was easily corrected - protecting the part with card, holding it in a vise and use parallel-pliers to gently 'form' the bent bit. (From typewriter-repair; 'forming' is bending when you mean to do it.) The brass pillars that hold the laminations likewise needed some straightening, probably more tweaking to come.

Up next; find a way to build-up and fix the broken black switch-base.

Friday, September 11, 2020

A damaged E6 motor

Vintage items bought online nearly always arrive well packed in boxes with lots of padding, some are very well packed indeed. Unfortunately this particular vintage item was merely put in a plastic envelope with two small, loose bits of foam-pad. It did not end well.

This is (or was) a Meccano E6 reversing 6 Volts electric motor. It's very sturdy, but also very heavy and got a nasty knock...  This bent and broke the switch-assembly and knocked the pillars out of shape, making the armature foul the stator. The seller was very good about the unfortunate event (he had completely run out of boxes that week), however leaves the question: what-to-do with this ~80 year old item.

As with every niche-subject, there is an astounding amount of information on the internet on Meccano and Meccano motors. From various detail features this specimen can be identified as an E6 manufactured in 1933. Originally it would have had bright brass and the paint would've been red.

The red & gold decal still looks fair, although the originally-red paint has faded to an almost-orange. It must've spent decades sitting on a shelf in a shed in the sun.

These motors are not exactly precision-built instruments, these are to a fairly 'rough' design originally dating back to around 1916. This means it should be 'forgiving' and practicable to attempt a re-build - seems a shame to have to discard (or dismantle for parts) this 87 year old toy motor. 

Will be having a 'tinker' to see what can be done.  :)

Friday, August 28, 2020

How to use Corona Floating Shift Models

 Have the typewriter, now also got the instructions to go with it.

Must admit to being a 'completist', and the Corona Speedline being a 1938 model with a gloss finish it should have a user manual that shows that finish (and not the 40-ies crinkle and stripes finish). So all illustrations in this printing show the typewriter with the plain, glossy finish.

The instruction booklet covers are a little yellowed, but other than that is in great condition. It scanned fine; so without any editing straight to PDF. Now available on The Archive: How to use Corona Floating Shift Models.

Again and still for the purpose to give all users of these brilliant portable typewriters clear and definite directions for the use and care of their machines:


Saturday, August 8, 2020

Igranic Honeycomb Coil

Browsing a Meccano Magazine back issue (the November 1924 edition), an advertisement for radio components caught the eye.

Specifically the coil pictured in the left-top corner. Hadn't paid much attention to these ads before, but last week a pair of coils for use with the crystal radio had arrived. (Ordered from the global bric-a-brac shop that is the internet).

The coil in the advertisement is labeled as the number 500 and this specimen is a number '150', but other than that it's the exact same type. Complete with frequency chart and the 'what the wild waves are saying' motto.

This neatly confirm that this coil is contemporary to the 1923 Edison Bell crystal radio set that it'll be kept with. This coil and another Edison Bell number 100 coil came plugged into a little tuning component, adjusting the coupling of two coils (De Forest).  

The nickelled fitting were badly corroded and dirty, but as is often the case with nickelled parts they came back fine from an encounter with Brasso and a cloth. The black parts are hard rubber, these were simply cleaned and given a thin polish with vaseline to help preserve and make them look better. 

The little setup was bought mainly because of the Edison Bell coil that looked intact - the Igranic coil was a bonus :) 

Wednesday, June 10, 2020

Hard rubber feet (small fix)

It's a common issue with a variety of old technology-items - the rubber feet have no grip.

The textile glue is actually latex and remains very 'rubbery'. The felt enables it to remain on the feet, otherwise it'd peel right off again. The felt can be glued to the hardened feet with the textile glue. Alternatively a spot of superglue (can also be removed again, dissolves with hot water).

For example the feet on this Corona Speedline typewriter had no grip on the table. Still pliant and 'rubber', but no grip.

A light sanding to roughen-up the circular 'base' of the rubber feet and a set of 1mm thick wool-felt pads ready to be glued on. A dab of the latex textile-glue and ready to be pressed on.

After setting of the pads, another small drop of latex is applied on the centre of the pad and given time to set well - that will then provide ample grip and not come unstuck from the thin felt layer. Depending on how much the visual appearance matters (the base of feet are not generally visible...), extra care can be taken on where to avoid getting the latex or to get an even coverage. As it is, went for functionality mainly.

Net result is multiple vintage items having functional feet again; a portable gramophone, crystal set and typewriter - a small, general retro-tech repair

Wednesday, May 20, 2020

Recreating 1920s crystal-set wiring

Continuing the restoration of the 1923 Edison Bell crystal wireless set, the wiring needed to be re-created. The remnants of wiring in the set as it arrived was clearly not original - at some stage the original wiring had been modified to probably use a 'modern' diode roughly screwed to the roughly drilled extra holes in the baseplate. The old wiring and all the lamp-parts were likely removed to make space for this. The thin cotton-covered wire itself also looked incorrect - the length of PVC-insulated wire was certainly not original.

Even though there is not that much information on the inside of these Edison Bell sets, or even on 1920s crystal sets in general, some pictures could be found online that showed the inside wiring. These are of three different units, so that common features to these three are likely to be original factory fitted parts.

From these images, it becomes clear that the set was originally wired with 'thick' wire rod. This was actually quite common in 1920s radios and electrics; bare wire forming a neat three-dimensional circuit. From the pictures made a guess at the diameter (probably just over a mm) and got some tinned copper fuse wire of just over a mm diameter.

To straighten the thick wire ('rod' material, really); the regular procedure. Unwind and manually un-bend a length of the wire. Then clamp one end in a vise (or clamp to the bench-edge) and the other end in a drill. By pulling and then twisting the wire left and right it gets nicely straightened. A hand drill is good to use as it gives a bit of 'feel' for how you're deforming the wire and when to twist back. For safety, always keep a bit of tape over the wire ends (cut wire is rather sharp and springy...).

With needle-nose pliers and a bit of 4mm tubing as former, bent loops in the wire ends and made the sections to fit the terminal posts. The first leads to fit were the connections to the crystal detector - these must've been formed in-place, as they pass through the small hole in the base-plate and should have loops at both ends. The loops at the detector crystal-covers need some tweaking with a kink in the lead to clear the glass. (Suspect the original may have used slightly thinner gauge wire, or perhaps even not made a loop there at all - just a straight wire-end?)

Following the same procedure and consulting the reference images of original sets, the complete wiring could be recreated and fitted again. Also the leads to the slightly-different reproduction lamp-fitting was added.

Bringing the leads to the far end of the variometer seems a bit odd - reversing the variometer to have the terminals closer to the baseplate would've saved some copper. But perhaps the ease of fitting (or whim) was more important than a few inches of copper wire back in 1923.

With some thinner cotton-covered wire to the battery-compartment, the lamp again works too. (From the pictures it could be seen that this should also be thick 'wire' with a green insulating sleeve - but there's a limit to authenticity here, this is more practical.)