key120

My Amplidan Morse Key Project

At long last my version of this famous Key, many times I have thought along the lines of a replica or look-alike call it what you will but resisted the temptation, for many reasons, the word "replica" always rings danger bells for me, after all what exactly is a replica? all things to all people it seems, to me a replica is an exact copy, indistinguishable from an original, and that, especially with an Amplidan would be almost impossible, I have seen other "replicas" of this key and thought it high time I had a go :() So what am I aiming for here, well in my opinion when you attempt to make a "replica" you have to be realistic, in as much as not only your own skill limitations, but also limitations in tooling and materials, all of which will affect the final result, so for me and my attempt on the Amp, its going to be a replication of the action, or as close to its "feel" as I can get by trying to make a close copy of the original mechanics of it, obviously I'm going to have to make some compromises along the way as my very primitive tooling can not remotely compare with the original machining that was used to produce this excellent key, and I will describe and photograph my progress for my own records and for anyone that is interested in a similar project, and at the end of it we should be able to tell if I made a reasonable attempt or a total bog of it, :))

Above left is a picture of the Amps handle, I have no idea how they made the sweeping lines, whether they cut it out of a solid lump of brass or moulded it in some way, I suspect it was made by power pressing a large sheet of thick brass and then cutting the handles off like ribs off a carcass, I have made mine by cutting a larger piece of brass down to size using my lathe and a large slotting blade, I have made an adapter for my lathe using a drilling vice, which does the job really well and only cost a few pence to make, and is an excellent way of cutting small pieces of brass to size.
there would of course other ways to do it like heat bending or casting, the first I have never had much luck with and the second never tried. above right is my handle, same size and weight and as close as I can get it to the original, the Amp handle is of course Nickel plated and my one will also be plated as I have my own homebrew plating system which is relatively simple to do. first step and so far so good :)) (Day1)

Above is my cutting modification to my lathe, it is simply a steel angle bracket fitted to the tool holder and on it is mounted a record drilling vice, mounted vertically, you notice there is only a single bolt holding it to the bracket which enables the vice to be swung round to any angle over the slotting blade for fine cuts at any angle it is a very useful item for amateur key making.

And now for the bearing holder and bearings, they are really strange on the Amp as can be seen above left, really they are not that special, and quite resistive in my opinion, they consist of two steel bolts with hollowed ends gripping a centre spindle in the arm with machined points, very similar idea to the famous standard American J type keys, only in this case a bit bigger, and the way they are kept tight is quite primitive, the threaded holder has a slot cut in it and the thread of the bolt or holder is slightly over size so its a tight fit, any access in tightness it taken up by the spring of the slot, on the Amp it looks as if the bearing holder is made from one piece of machined brass, I have made mine from three pieces bolted and soldered together, seen above right, in the Amp they have used about an 8mm bolt, I'm starting off with a 6mm one, I may go up in size later but 6mm is easier for me to work with and I can't see it will affect the action much but that is a compromise and I'm aware of it also my slots are slightly wider by .5mm another compromise, I have a feeling I will be doing more of this as I go along :) time to fit the handle onto the bearings (Day2)

The bearings are now fitted, I have used the same principle of a shaped point into hollow adjuster, I can't say it's my favourite way of pivoting a key as from a practical homebrew viewpoint it is quite difficult to achieve an exact alignment, I have used 6mm pivots and all brass, in the Amp they are steel, there isn't a lot of difference in performance I've found if they are lubricated, I could easily change them to steel at a later date if I think it's needed, the sunk in tension adjuster is another compromise, I haven't flattened the base yet and the knurling is a bit coarser, this is really just cosmetic and and won't affect the action, (Day3)

Today I made the gap adjuster mechanism, it is quite complicated on the amp, it consists of a hollow tube with a slot cut in it so that it sits over the gap adjustment support arm, inside is a large spring which applies tension to the gap adjustment knob, so the adjustment is smooth and stays put after its been set, most keys have a ring tightener, I suppose it's the sort of thing that makes the amp a bit special, above right you can see my brass ones and the amps plated ones, On the left you can see my Amp against the original, this is just a mock up just to give an idea, my parts are resting on the back of a TV controller :() but I do like to get an idea of what it will look like which tends to spur me on when interest is waning, (Day4)

Not much time to spend on Key making today so I thought I would make the special "Comforter" Amp knob, it's a strange looking knob for a Morse key yet it works well and is a distinctive part of the Amp, I have made mine in Delrin, a sort of black plastic that can be machined, but for any prospective amateur key makers Beware Delrin!! it can melt and stick, also it can easily come loose from the chuck if you are turning or cutting it, a 6 by 2 inch piece of Delrin coming lose at 300rpm gives a new meaning to the phase "being hit by a blunt instrument" been there etc. you can see the two keys side by side, I'm a bit concerned about the gap adjuster supports they are smaller than the original and give it a "spindly" look, may have to change them for beefier ones, also my piece of hex bar under the knob is smaller as I have nothing bigger, may have to change that later, more compromises, nose contact arrangement next and then start thinking of some sort of assembly, (Day5)

Today I made the nose contact arrangement, in the original Amp the main arm of the key is isolated, the contact current is passed from the contact bar down the flat counter spring to its fixing on the base of the key, which means its quite tricky to make as insulators have to be made and fitted in the nose, I had trouble with the counter spring as this is flat tensile steel, you can't drill it, so fixing holes have to be punched into it, see above left, on the right is a partial assembly with blocks of scrap brass under the contact position so I can line it all up and see how it's all going to fit together.

On the above right you can see the basic action idea of the Amp, the floating top contact is not fitted yet and the bottom rest is a few blocks of scrap brass but there is enough there to do a first test, there are problems, it has the makings of a fine action but at the moment it certainly isn't the same as the Amp, it has a dead feel to it, in the original Amp if the tension is slackened right off the key resonates, The Amp uses a tried and tested method of producing a fine action, it has a main coil spring offset by a flat counter spring, I have used this method before in some of my early keys and some Swedish keys use this idea and in some cases the counter spring also doubles as a pivot, it's a good idea but extremely difficult to get right as the two springs counter each other and the tension has to be just right in each one, I think the coil spring I'm using at the moment may be to hard, so I shall experiment with that, and also the brass bearings may be a bit stiff, I hoped they wouldn't be but it's not really a problem to change them (Day6)

I've decided to change the bearing adjusters to steel ones, this proved to be a good decision, tests are now quite positive, and at last this key is now starting to feel like an Amp, also fitted the stop and the moving top contact, the post that holds this contact is a little bigger and closer in than the original Amp, will fix that later, next is the real tricky bit of finishing and fitting the spring loaded contact adjuster knob

Today I fitted the spring loaded gap adjuster which went better than expected, getting everything to fit and work smoothly was a challenge for my limited tools and skills but now it is starting to look and adjust more like the original Amp, more compromises with the steel base as I've used what I have and its slightly wider and shorter than original the sprung top contact post has been resized and all that remains to do is fit the wiring terminals and cable clamp, a stop on the tension adjuster, and then a complete strip down to smooth out any machining marks and then the Nickel plating, which is just as well as interest is fading fast, I started on the 29th and it's now the 6th so 9days into the project averaging about 4 hrs a day about 36hrs work

Here is My Homebrew Amp, finally finished, plated and most of the odd bits and pieces sorted, It was a completely different experience making a copy than an original YUH design, I had to make so many compromises, with materials, sizes and shapes that it tended to spoil the fun a little, as to the action compared to the original, well it's close :) very nice, smooth and precise, I learnt a lot, given some extra tools and correct materials I could probably have made a better job, but I knew I could never make a replica when I started, at least I know a lot more about making an Amp copy than when I began this project so time for another go on the next key :()

An insight into the original Amplidan 50713