Various things have caused me to spend less time than usual in ˜The Tank" but I have managed some visits there. Unfortunately the time spent has not seen great progress with the J10 but the events have caused some important decisions, not only about the J10 but about future scratch builds. The title of this page may give some idea of what I'm going to pontificate about!

My mentors taught me how to make simple, split-axle chassis that run well and involve only very simple, basic engineering principles. I have followed what they began way back when rationing was still part of every day life and, though this smacks of bragging, I can claim that my chassis, be they scratch-built or based on kits, run very well, very smoothly and very slowly and all my locos will pull a suitable load on my layouts.

However I am willing to try new ideas and my original intentions for both the J10, and the Q4 which was to follow, was that they would have this much-talked-about continuous springy beam suspension, but only if I could meet all other parts of my specification for loco chassis like; split axle, split frame, ability to drop any axle easily, tender weight transfer.

I started with the two tender chassis but with what I considered to be a simplification that the axle boxes acted on the csb but were not attached to them. Use of frame spacers of solid cubes of accurately machined tufnol raised problems of how to fit the springs in place, and drilling clearance holes in the tufnol through which the springs would pass with plenty of clearance was a possible answer, as too was a chassis-long, thin tufnol spacer or copper laminate sheet spacers.

The latter were tried first but I considered that the whole frame assembly with them was too weak and difficult to get square. This lead to my considering that a long thin spacer would also be too weak, so block spacers at each end, each with csb holes as mentioned above, and with a copper laminate spacer above the spring adding some strength at the chassis mid-point. This seemed to work OK, and the two tender chassis were built in that form, one with Gibson wheels with the tyres shorted electrically to the axle and one with my home-made, all brass wheels. Initial running tests seemed OK but until the body and couplings are on a tender chassis it is not easy to test thoroughly.

The loco chassis was made following the same idea. I did not bash my brain with calculations for the csb, - in all cases I used the CLAG web site, where there are a choice of spreadsheets to do all the technical stuff for you. I kept religiously as possible to the figures resulting from feeding the spreadsheet.

As regular readers know, the body for the J10 is virtually complete and chassis and body have been introduced to each other and running tests carried out. I spent many hours tweaking before I could accept the running and at that stage started to doubt that the complexity of csb did not merit the extra effort I had needed to provide. However the loco on its own is now running sweetly.

When the J10 was attached to its intended tender, and all was beginning to look cosmetically good, the seeming inability of the tender to stay on the track raised further doubts. None the less I persisted, after-all, the loco had needed a fair amount of tweaking.

After far too many hours of tweaking, weight shifting, spring diameter changing, etc I decided that this CSB thing is not for me. Even if the J10 eventually proves to be capable of phenomenal pulling power, the complexity of CSB against the simplicity of my mentors ideas, ideas which I have proved I can easily copy, leaves my ancient system streets ahead of this newer idea as far as I am concerned.

The decision to build a new tender chassis to those old ideas was made on Sunday July 1^st. On Thursday July 12^th that chassis was fitted to the tender body and ran like a dream – not a nightmare! While 12 days may seem a long time, remember I have not been in the workshop every day and certainly not for any full day.

I said earlier that my friends used basic engineering principles; - what do I~ mean?

Well in the case of the tender, the frames have a full-length tufnol spacer with sides machined square and perpendicular to length. This has space milled out for axles and the simple spring system but it otherwise is as thick as the frame depth, making for a very solid frame assembly. The rear axle rides at the top of its axle slot which is positioned to give correct ride height, the other two axle slots are 0.020" (0.5mm) deeper but their axleboxes are sprung down by a simple cantilever spring made of 27SWG phosphor-bronze wire, the cantilever being 15 to 20 mm long; no great precision of tolerance is required. The front of the tender is carried on the drag bar to the loco and that gives three-point suspension to the tender and adds weight to the rear axle of the loco. Simple and basic! But it works so well

For locos similar deep block tufnol spacers are used but as here we usually need to be able to see through the frames, these are spaced front and back for loco to chassis fixing points and any where they are not seen elsewhere. The front and rear axle slots fix ride height, any middle axle slots are again 0.020" deeper. All axle boxes, except perhaps that carrying the transmission unit, are sprung down, again with a 27SWG P-B spring of 15-20 mm cantilever. My mentors started doing this as long ago as 1946 and their models will stand alongside those of today, and will perform better than many!

It's a proven system and this dinosaur has gone back to it and will be sticking with it in the future.

These pictures may clarify my words:

This shows the cantilever springs for the centre and leading axle. Also seen are dowel and screw holes to fix the frame to the spacer. All very simple; no great precision needed, simply adjust the spring to have a short horizontal section to run on top of the round axleboxes (bearings!) and giving light downward pressure when on the track..

The material is tufnol, preferably a grade based on fabric rather than paper; - it machines better! Space for the axles has been milled away and some of the screw holes and dowel holes show too. Notice the colour coding; it's nail varnish and ensures bits go back in their original positions. The upward pointing brass rod is a dowel which locates the axle retainer.

Every thing here is home made except the actual materials. Tufnol rod for the axle muffs; 1/16" dia. silver steel rod for the stub axles; brass rod for the wheels which are Manchester (i.e. Sid Stubbs) profile and brass rod for the plain round axleboxes.

Simplicity again! Copper laminate and copper wire (actually fuse wire; 30A I think). Two dowel holes for correct location and a countersunk screw to fix. The copper wire is nice and malleable allowing adjustment of axlebox fall.

A view under the tender;-. Colour coding is very obvious here; it will be less so after the tender has been in the paintshop! But smaller blobs will then be added for possible future strip-down

Dave