Short-Wave baseboard 2

[Variometer]

I am slowly making and/or converting components to basboard mounting to build a small battery two-valver. The coil is home-made from black acrylic sheet, a plastic tube, a few nuts & bolts & solder tags. The wire is standard solid "bell-wire." The variable capacitor is home-made 150pF (described elsewhere in the forum). I now only have the fixed capacitors, reistors & aerial trimmer to prepare. As usual, the circuit will not be anything special, grid-leak with reaction followed by output stage. My main pleasure comes from building or adapting the components, the physical contruction with brass nuts & bolts, polished brass strips, polished wood base etc - plus of course - good performance.
Probably quite a number of days before everything is ready. Then I will build a "rough" prototype" & once it is working to my satisfaction, I will re-build it properly.
Here are the components to date:
Bob

[newlite4]

This is looking good Bob. There is something quite nice about this type of construction, even better since the component bases are built from scratch.
Neil

[Variometer]

Thanks Neil,
I got the idea some time ago when I wanted an acorn valve holder, but could not find one. I drew the proposed holder on a sheet of 3mm black acrylic then drilled the centre hole out for the valve "pip." Then drilled terminal & fixing holes round the outside. Finally, I cut the whole circle out & fitted it with nuts, bolts, solder tags & washers. The valve pins are trapped between two washers on each connection. A hole has to be drilled in the baseboard beneath the holder to take the "pip."
It was a great success & I soon realised that I could fit a standard B7G (or any other valve holder) in the middle & it would still produce a neat baseboard valveholder, although it still requirea a hole in the baseboard to take the projecting pins. They are wired up underneath with fine tinned copper wire.
Incidentally, I get the 3mm acrylic from Ebay in A4 sized sheets. Always plenty there! (I only mention this because I am always being asked where I get such an unusual item as black acrylic sheet from).

Anyway, here is my first attempt - the acorn holder.
Bob

[Colin]

Wonderful stuff Bob! How do you cut the circle out?

[Variometer]

I drill the hole in the centre with a wood-cutting drill bit. These are very inexpensive & common. The outer circle is cut using a small hobby type band saw, but it could be cut out with a jewellers saw or fretsaw, but it would, of course, take a lot longer. Alternatively, if you don't have a bandsaw, you could make a square one & that would be a lot easier to cut with a junior hacksaw.
Bob

[Colin]

Do you cut round a marked circle using hand, eye and judgement or do you use some kind of jig?

[Variometer]

The black acrylic has a protective backing on it that can be drawn on with ball pen. A normal ball pen will not fit in a pair of compasses, but the inner ink refill (Parker) will. I draw the circles with that. After central hole & terminal/fixing holes are drilled, I cut the outer circle out in the small bandsaw by simply rotating it against the blade. I could cut it out using a fretsaw, but it would take longer & need more care. Outer edge is smoothed off with Wet & Dry (carborundum) paper.

Some acrylic has a clear backing on which the drawing can not easily be seen. If this is the case, I just paste a piece of normal white paper on it using a water-soluable Glue Stick - it holds it well enough for the drawing & cutting & is peeled off with the backing when the ring is complete.
Bob

[Baggrus]

They look lovely, proper vintage styling. I saw the coil in it's can and the acorn valve in the other thread and was most impressed.

I happened to notice this today while digging out the tools to fit a yale lock to my back gate. The hole saw/drill thing I have looks ideal for making both the outer cut and the centre hole all in one go, perfectly round with the pilot hole in the middle in the true middle.

I can tell by the looks of your beautiful finished articles that the time and precision is a large part of the pleasure you get from creating these wonders, but I'm just thinking about possible ease of creation for those of us who may not have the hand/eye co-ordination we would wish for these days.

Ignore me.. I'm always looking at tools and thinking about "wrong" ways to use them. Just like my new desk phone which proclaims in the instructions.. "Warning!.. Not to be used for the other use" I'm sure I can think of one after such a determined challenge.

[Variometer]

Hell Baggrus,

I think you may be talking about the hole saw shown here on the right. I do not use these at all for the valveholders. The outer circle would have to be cut first or you would lose the centring hole. But to cut the centre hole after the outer one has been cut out would place fingers too close to the drill for my liking!

I cut the inner hole with a 16mm wood cutting bit as shown on the left. This fits a B7G valveholder. I find it easier to drill the terminal holes whilst the valveholder-to-be is still in a large sheet of acrylic. In this way, I can keep my fingers away from the drill bit. Cutting the outer circle is no great problem with a small bandsaw or electric fretsaw.

Making these items does not take me very long as I do them at odd moments when I grow weary of building ship models. To make a valveholder ring, complete with terminal holes, takes about ten minutes. I normally fit the nuts, bolts & solder tags later & that only takes a few minutes as well!

Once all the components are ready, the actual assembly of the prototype will probably only take half an hour. A lot more time is required to complete the final building neatly.

Bob

[Variometer]

Hello again,
I have just laboriously completed making an aerial trimmer. It was about three times the trouble of making the 150pF tuning capacitor. I guessed at two fixed vanes & one moving vane to give me about 50pF. Anyway, it turned out at 15pF. I then made some more both fixed & moving vanes & re-assembled it only to find it was then about £150pF. I removed them one by one, testing each time as the capacitance reduced, which was quite tedious as I had to take off back panel, nuts & washers each time & then re-align the plates. Finally, with three fixed & two moving, it was 0 - 62pF which I guess will suit me fine. Aboslutely fed up with variable capacitor making for the moment, so off to do something else - but here you are - the 0 - 62pF (just completed) is on the left & the 150pF tuning capacitor (built a few days ago) is on the right.
Bob: