QRP Club

Ham Radio Activity => Telegraphy => Topic started by: G0BVZ on January 11, 2014, 16:00:10 UTC

Title: HEAVY key bases in Kent keys -using Ebay -shoulder washers
Post by: G0BVZ on January 11, 2014, 16:00:10 UTC
I noticed I've become heavy handed since I returned to the bands and my key tends to wander about  if I tense up or get excited when sending.  One common solution is to fix the entire key to a heavy piece of steel plate waste of suitable size after  cleaning, deburring and shaping with a standard angle grinder and slapping on a coat or two of paint. Many keys come with fixing holes from new, to ease the job.

The disadvantages?  The finished job can look..... agricultural and depending on the dimensions of the plate, the knob can become too high for comfort so if using this method, take into account the eventual height of the key knob. I can live with a rustic looking key but an uncomfortably high one is another story.

I could not resist buying an old Kent straight key for a very low price on Ebay. The brass was dull and corroded, it was a *very* sad key.  The idea was to take it apart and clean it up. That was easy and after a lot of hard work it gleamed like new and there was no play in the bearings. So far, so good.

I decided to mount just the brass of the key on steel plate I already had. I know Kent offer a very fine key metal base conversion kit but I was looking for a personal solution. (Ages ago I bought a 1.5mx7.5cmx1cm thick steel offcut from a small steel stockist for a few pounds.) I cut a suitable length off using an angle grinder and tidied it up.  I used the holes in the wooden base as a template for drilling holes in the new base and I drilled the new base accordingly.

There was one teensy problem: steel conducts electricity much better than mahogany: if I mounted everything as per the original, there would be a dead short and the key useless.  The lower contact mounted on the steel base has to be insulated from it, as does one of the wire mounting posts.  But how?

Rejecting crude solutions I turned to Ebay.co.uk.  I then realised that I did not know the name for the sort of washer I was looking for.  Eventually I discovered that what I needed was called a shoulder washer, made of nylon.  Searching Ebay for "shoulder washers" produced plenty of hits and I purchased a small bag of assorted nylon metric shoulder washers in sizes M4, M5, M6.  A shoulder washer looks like a minature straw boater hat with the circular crown missing. The hat fits into the hole and the brim surrounds it so fitting one top and bottom of a hole in metal keeps fixing bolts centrally located and electrically insulated from the steel. That felt like a professional solution. I used one under the far bump stop to keep things symmetrical.

The threads on my key were commonly available metric sizes.  The lower contact spigot was a perfect fit in the upper shoulder washer and the fixing bolt was metric. I forgot to mention that where I used shoulder washers I had to overdrill the holes to a larger size to accommodate the extra width of the washer body.

To keep all components in the same relative positions as in the original, I used a brass shim to raise the central bearing block the same height as the thickness of the washer shoulder.  You don't have to use brass shim, you could simply use small brass washers on each of the bearing block fixing bolts or simply use a piece of plastic of the right thickness underneath it to get the same effect.

I rewired the key and tested it.  It was a real 'clacker' with a medium wide gap and a wooden base.  It was much quieter with the steel base -think loudish clicks. When adjusted to a gap less than the thickness of a piece of cheap copier paper it just made refined clicks, really quite quiet. The difference between a loud click and a quiet click is about one quarter turn of the adjusting screw.  Eventually I discovered that one twelfth of a turn made a noticeable difference.  Now all I have to do is learn how to produce CW that doesn't sound as though the op is a camel sending left-footed!!  :)

When content with the key I took it apart, painted the base and reassembled it. I'm happy with the result and the very low total cost.  The method I used is adaptable to other brands of key and is one way of making an unbranded, undistinguished key into something highly personalised and very heavy.  You must be careful about the fixing screws and bolts. Not all will be obligingly metric so you may have to re use originals.

One big plea: please don't do this to a fine old key with historical value; that would be vandalism.

One further improvement I'm considering is extending the keying arm with a thin piece of very slightly flexible metal. The extension would be concealed by the knob skirt.  Why would I do that?  Well, there are some very beautiful long arm keys around which have the arm contact on the upper far end of heavy keying arms. Pressing the knob down moves the contact UP,  to make contact with the other contact, which is above it.  Here's the thing: the contact point on the key arm is mounted on a slightly flexible steel tongue.

I believe those great keys feel so good because there is a minute amount of spring in the system and because the key arm is long, so I'm looking to introduce a little length and spring too, but at the knob end of the arm. Mechanically it does not matter where the 'spring' is introduced but possibly more will be required at the knob end of the key arm.  I'll have to experiment in this area: I hope to develop a little of that 'long key feel' without making a modification which cannot be reversed. As it is I have a neat key which feels 'screwed down', looks good and which offers scope for further refinement.

I hope these ruminations serve to prompt others to experiment. I've rambled on a lot because I can't operate at the moment and this seemed a good use of the time...

Vic /possibly the worst mechanical bodger in the world.....
Title: Re: HEAVY key bases in Kent keys -using Ebay -shoulder washers
Post by: GM0LVI on January 11, 2014, 19:24:09 UTC
It would be nice if you could post a photo of the key and base Vic.
Title: Re: HEAVY key bases in Kent keys -using Ebay -shoulder washers
Post by: G0BVZ on January 12, 2014, 16:13:22 UTC
Hi Dave,

Maybe I can do better than that. 

At a radio rally today I snapped up another basket case Kent straight key at a sacrificially low price.  I'll go through the whole process again and I'll try photographing my progress as I go. 

This will be a real challenge because on those rare occasions when I remember to take off the lens cap I end up with my thumb over the lens or the camera strap gets into the pic; I'm altogether a sad case....  Then I'll have to learn how to upload pix to this site. Gee whiz...

This time I think I'll try annealing the steel:  this stuff is awful HARD, possibly rolling hardened it. A nightmare to drill, it blunts taps fast so I'll take it to red heat and let it cool slowly in dry sand. Anything for an easy life.

If I can source the good stuff, I fancy finishing the base in black wrinkle paint this time even though it has a bad rep usability-wise.

Might take a while to get my ducks in a row but I'll give it a go: how's that sound as a plan?


Title: Re: HEAVY key bases in Kent keys -using Ebay -shoulder washers
Post by: GM0LVI on January 12, 2014, 20:53:13 UTC
Looking forward to the pixs Vic.
I made heavy bases out of black marble hearth tiles, one to an Admiralty (NATO) key that had a super action and another base for an ex-army 'Key WT 8 amp'. Wish now I'd hung onto the first key, but wanted a memory keyer and needed the cash!
If you never tried it marble is easily cut with a hacksaw.