Twitch - or Collins' Folly
                                                                 01-05-03      

  Many years ago a set of Tich castings was bought and clever clogs set about improving (?) on LBSC's design.

 As well as hollow pistons fitted with 'O' rings, valves were balanced, marine type links fitted to allow larger bearing surfaces, cross heads were re-designed and a cross head driven pump fitted.  The first snag appeared when I pushed the nearly finished chassis along the bench and discovered that as soon as one of the springs was compressed the mechanism jammed!  Most of my previous experience had been with small I/C engines where close fitting bearings are essential if they are to retain an oil film - a philosophy which simply doesn't apply to an engine with a flexible geometry.  Reluctant to waggle a reamer in the bushes, I set to and designed self aligning big-ends. These were successful and the chassis could now be pushed along smoothly (and making an intriguing 'plopping' noise) with any of the corners depressed.

  Sadly, expensive disaster struck when I made a complete nonsense of the boiler - and then discovered that the, intractable, drawn phosphor bronze which I had so laboriously used for most of the bushes was a very poor bearing material.  Never mind, it had been a lot of fun and a great deal had been learned, so poor Twitch joined the castings ripening under the bench --------

             

  ------- and there it stayed gently rusting and almost forgotten for many years while I played with hot air engines.  Until last Christmas when Peter, one of my sons, presented me with a certificated boiler!
    Temporary plumbing was fitted to connect up the cylinders and, for the first time ever, it ran on compressed air. Now to dismantle and de-rust ---

      04-06-03
 Rear boiler fixing angles have been filed to fit over the external projections of the blind bushes provided for the fixing screws, rather than relying on 7BA screws in shear.  Smoke box saddle casting ordered.
 Made arrangements for getting oil to inaccessible axle boxes by plumbing with capillary tube back to the foot plate..
 Fitted a stainless steel grate, requiring a deeper ash pan, and a non-standard grate dropping arrangement operated from the foot plate has been fitted.
 Replacing the eccentric driven feed pump by a cross head driven one has required a different oil pump driving arrangement, now taken from one of the links.
 Several long forgotten bodges discovered and rectified while de-rusting and tidying up continues.

                                                                                                     
                Self aligning rods                                                                                                                        First month's progress   

  To be continued.

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