Paul Townsend wrote:What is the etch thickness, it looks like 18 thou
It is 0.3mm / 12 thou.
Cheers,
Richard
Paul Townsend wrote:What is the etch thickness, it looks like 18 thou
Crepello wrote:Perhaps a small "T" for Top half-etched where the bogie pivot will cover it, would jog
the distracted/absent-minded into always starting with the correct side up?
Richard Oldfield wrote:Courtesy of the drawing skills of Colin Craig here are a couple of diagrams showing the springing system:-
Richard Oldfield wrote:Hi,
Courtesy of the drawing skills of Colin Craig here are a couple of diagrams showing the springing system:-
zebedeesknees wrote:There does not appear to me to be any kind of stop to prevent the spring wire moving longitudinally,............................]This could be prevented by filling the hook part of the bearing carriers with solder.
Will L wrote: I'd be interest to know which if any faces you leave unpainted?
zebedeesknees wrote:From here:- http://www.clag.org.uk/beam.html the design of the spring fulcrum makes it effectively a cantilever spring over each wheel with a length L (scaled from my monitor) of approximately 10mm. Experience and the maths suggest that this could be 'a bit stiff' with the chosen wire diameter. If too stiff, and 'no slop', then there could be a danger of derailments on abrupt changes of cant or a vertical misalignment of a rail joint on one side.
zebedeesknees wrote:There does not appear to me to be any kind of stop to prevent the spring wire moving longitudinally, unless the idea is that the wire is intended to have a 90°bend at one end to locate in the notch of one of the bearing carriers. Not both ends of course! This could be prevented by filling the hook part of the bearing carriers with solder. Experience again, the wires will 'walk' if not restrained.
zebedeesknees wrote:Chris Pendlenton was aware of the importance of secondary springing with his bogie design of decades ago, and an alternative was produced that is not integral with the bogie by Bill Bedford, both descibed here:- http://www.clag.org.uk/beam-annex5.html. If the Bedford etches are no longer available, it looks from the pictures that a version with similar dimensions could easily be fitted to the body floor using good ol' Markits handrail knobs.
zebedeesknees wrote:The proof(s) will be in the running, and if I may suggest, an idea would be to make up a pair of bogies slightly differently to test as follows; do not fold down the fulcrums that are just inside the brakes, and make up a fulcrum in the centre of the bolster with a piece of tube or handrail knob such that the wire can pivot about it in much the same way as the Johnson locomotive bogie design. This is in effect an inverted version of the design discussed here:- http://www.clag.org.uk/beam-annex2.html. For this a slightly thicker wire may be preferred, depending on the weight of the vehicle.
zebedeesknees wrote:I hope you find this helpful as intended and look forward to progress in whatever direction.
davebradwell wrote:...It's recorded that heavy coaches will splay out an MJT unit so will they not do the same with yours? The frame looks very flimsy and I'm wondering if with stiff springs it will just work like an MJT.
Crepello wrote:Hopefully the spring arrangement sketch was not pasted from the design drawings, as it suggests
the brakes only line up with the wheels when the bearings are bottomed in their slots?
davebradwell wrote:First point is it will be a waste of time pulling a few coaches round the layout as an evaluation - re-wheeled Bachmanns would pass this test so it's a very low bar. The whole point of springing is to get superior track holding when propelling stock so you'll need about 10 coaches and push them over pointwork into sidings, preferably with Pullman gangways in contact and buffers retracted as this is what coaches must do, but perhaps not on Mostyn.
davebradwell wrote:Is the top of your bogie strong enough? It's recorded that heavy coaches will splay out an MJT unit so will they not do the same with yours? The frame looks very flimsy and I'm wondering if with stiff springs it will just work like an MJT. Why not put a mark on outside of axleguards to indicate correct ride height? How do you plan to adjust this?
davebradwell wrote:I feel you're missing a trick with the secondary springs - correctly implemented you can dump the primaries. Others miss a key part of the design of the Pendlenton bogie. We've all seen the coach with a wobbly wheel, given away by the body trembling about a horizontal centre of rotation about half way up the body. With short secondary springs on top and a high bogie pivot, there is still a danger of this occurring. The Pendlenton bogie, which I believe was developed within the West of Scotland group a decade or so before it appeared in MRJ, forces the body to sway about a point low down so it's like an inverted pendulum rather than an oscillating balance wheel and crucially, with long springs, any oscillation is much slower - a sway rather than a wobble and well damped. The centre spacer is a box section so prevents the frame twisting. Throw in steps with supports and Jackson coupling mounting and nothing has come close.
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