This is key 156 and this thing below is a C-flex bearing, they are VERY unusual having built in spring tension, they are also VERY  expensive, this one was a donation to see if I could build a special key around it, The main problem with a C-flex key it how to tension it, with this design I hope to adjust it by gripping the outer parts of the bearing in special bearing mounts, then the rest contact is moved out on a swivel, the arm dropped down below the rest contact position the centre part is then locked in place  the key arm lifted above the rest position which brings the key into tension, and then the rest contact is swivelled back into position and also locked into place, it sounds complicated but it will be much easier to do than describe, There is another way it could be done by fixing both parts of the bearing in place and then altering the rake angle of the key arm , or even a combination of both, As this key is highly experimental the design may need to be changed whilst it is being built.
Already I have changed the design from the initial design sketch below by putting the centre bearing grip in front of the bearing instead of behind, the reason for this is so I can make this revolutionary key resemble a vintage Swedish design, as experience has taught me that if a key looks unusual or ugly then its condemned or ridiculed even before its been tried. :()  I'm hoping that this key will not only look good with Classic lines but will also have an action you only dream about :))))
Because the key arm is quite narrow the bearing will need a slotted sleeve to steady it when it is being locked into place, below you can see the sleeve pushed onto the bearing as the first parts of construction, and below that the basic arm completed with the sleeve now slotted and fixed in place, (The knob is just temporary to give an idea how it will look) you can see how by tightening the knob the centre of the bearing will be gripped, One of the secrets of exceptional key action is getting the tensioner as close to the pivot point as is possible, on this key the tensioner IS the pivot point!!! so I am expecting great things from it,
Below is the key arm now mounted on its bearing holders, supported by the tension of the C-Flex bearing, the bearing holders were a problem, I had hoped to use something similar to a Swedish bearing but that proved impossible owing to the fact that the C-Flex bearing ends have to be gripped, so they are now similar to the Marconi 365 type, also owing to the shape of the C-Flex the key is quite narrow, the base is also a problem, it just doesn't suit a wooden base which seems to high up, also a plastic or Delrin base doesn't look good either, The Swedish design idea just isn't going to work as the key is just the wrong shape, so seeing as the new tensioning idea is more like an Amplidan key I thought I might make this one a bit "Amplidanish" hi!!!!
And now it's got to the point where I can test it, here it is as originally envisaged, it is possible to tension the key from the C-Flex bearing by simply slackening the large knob which releases the C-Flex, then gripping the bearing tightly with forefinger and thumb and turning the outer edges, then quickly tightening the knob again  the C-Flex is then tensioned and the key operates. The problem with this is it is a one off operation, if you don't turn it enough then the key is to light, to much and its to heavy, also at the same time you have to make sure the key arm is central or it tries to grip the outer edge of the bearing and it all goes tight. Anyway it is some key!!  light and responsive, one of the best low angle keys I've used, I think a redesign of the tension arrangements is really required using a coil spring to compliment the flat springs in the C-Flex, similar to the Amplidan
Below you can see the key almost finished mechanically, it needs some front terminals and a clean and polish but that's about it, to be really honest the bearings work best as just bearings for a Morse key, putting bias on them one way or another doesn't seem to add anything to the performance, if fact I'd go so far as to say fitting the coil spring has improved the action, there is of course a tiny bias against the coil spring owing to the way the C-Flex is made, also the bearing was a bit big, a smaller one would have been easier to work with, however saying all that this is one special key! the action is almost identical to the Amp, a tad softer perhaps but close, very close..
I have kept the adjusters and terminals very simple, the tension is just a simple spring puller and the gap adjuster is a simple knurled screw with a locking ring with tiny tommy bar, and the contact post is also very simple a hex bar with an isolated resting screw, 
And finally below the finished Key156 with conclusions.
Well this key was a real voyage of discovery, I learnt a lot about C-Flex bearings!! they are very good no doubt about it, and do take out a lot of the problems of alignment with ballrace bearings, but they are expensive, whether they would justify the cost in a Morse key I'm not sure, this is an excellent key, it has that effortless feel to it which is hard to describe, I think it is slightly tail heavy but then low angle keys seem to benefit from that and of course this key can counter that with a positive bias from the C-Flex (which I have done) Also the knob is a new design, I have made a lollypop knob but scalloped out the centre and left a fine ridge on the outer edge to give a little more grip, the knob itself is lifted slightly so it could be used for upright and well as low angle method of sending, at the moment I can't think of any key that I have used that could out perform it, I'll be honest and say it didn't quite work out as I expected as far as looks go, instead it turned into a "YUH Special" which isn't a bad thing,