Entry posted by Fen End Pit
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Now this locomotive has been very long in the making. Originally constructed from an Alan Gibson kit while I was at university 25 years ago this has always been a bit of a 'problem child'. The 2-4-2 wheel arrangement makes it virtually impossible to get around any kind of curve without resorting to some way of getting the leading and trailing axles to turn into the curve. Obviously the prototypical way of dealing with this would have been radial axle boxes but these are fiendishly difficult to make without resorting to a lathe and some serious engineering. This version of the chassis isn't exactly pretty, will probably horrify the hard-core springy beam fans and leave me open to intense critism from the purists. However it works!
The two carrying axles run in bearings connected via a strip of brass pivotted from the centre line of the locomotive. The chassis is beam compensated with a single beam between th front and front-driving axle and two beams between the rear-driving and rear axle. I had a bit of fun getting the pivot points right to get the correct distribution of weight between the driving and carrying axles. Too little on the carrying wheels and they won't turn, too much and the locomotive looses traction and slips with anykind of load.
I need to sort out another inside for the cab on this one, just like the N7 rebuild of a few weeks back. Also I need to get some pipework back on the front buffer beam and even out the weathering.
Last up for the current loco builds another picture of the D16/3 which is now finished with the exception of getting a smokebox number. The cab windows got glazed after a fair bit of fiddling.
Our little group met round at mine last week and we ran a few trains round and round. This was fun but really showed the limitations of the existing fiddleyard. Plans have been drawn up and an order went out earlier on in the week for a fair bit of aluminium section, I've decided to put aside thoughts of a radical re-design (linear paternoster, cassette moving robot etc) and go for what I hope to be is a better engineered version of what I had built already. I also hoping to make it about 10cm longer so I can accomadate slightly longer trains. Going from 100cm to 110cm will make quite a bit of difference. At the moment I can only run 3 mark-1s with a 'short' loco like the N7. Adding the exact 10cm means I can use the Claud. Also the typical freight will go up to loco+10+brake which looks much better than the current 8 wagons. I should be able to get 6 'levels' on the fiddle yard which will allow for a through road to be kept clear while storing 2 x Express Passenger, 2 x local Passenger, 2 x parcels, 2 x general freight, 2 x coal. The current plan is that the top 'deck' features a crossover so I can get stock from the up to down line off-scene for example to reverse a DMU. I'm also wondering about making a loco length cassette on the top deck so you can swap a loco without having to handle it.
The original version never got the complete 6 decks, while it essentially worked ok it was never going to be possible to automate because the alignment bolts always needs a bit too much force to ldeal with the twist and slope in the various levels. This was cause mainly by building the levels one at a time. I'm hoping if I make the whole thing accurately, using Easi-rec aluminium tube as the main structure, it should make alignment more reliable.
Watch this space!
David
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6
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