Delph - Class 40 progress, with a deep breath
Entry posted by Dave Holt
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Work on the sprung chassis for the Class 40 has progressed with the PenBits etched brass kit assembled and work on modifying the Bachmann drive units and bogie frames started.
The PenBits chassis went together perfectly, with virtually no adjustments required other than minor filing to get various sliding parts to give a nice fit. This was mentioned in the very comprehensive assembly instructions available on the PenBits web site, so came as no surprise. I didn't bother trying to download or print off seventy-odd pages but just browsed on line as I worked - fortunately, my computer is right next to the work bench.
Although I've stated that the chassis is sprung, it's actually a mix of springing and compensation, with pairs of axles sprung using guitar string wires which are able to pivot in their mountings for the primary (on bogie) suspension and the bogies resting against secondary spring wires under the bogie mounts, again able to rock in the fore-aft direction. It all sounds rather complicated but actually goes together nicely with a bit of care and by being methodical, also being careful not to mix parts up between the two bogie assemblies.
Having done all the soldered parts, I had to move on to the modifications needed to marry them to the Bachmann parts. That's where the deep breath came in. It's quite daunting to have to start chopping up the workings of a £200 r-t-r model, knowing that there's no going back or manufaturer's warranty available.
The following photos show aspects of this recent work.
First, the Bachnamm drive train has to be dismantled and sawn into two pieces, with a sliver removed to allow articulation between the axles. This shows the result with the gears re-fitted to the larger piece and the bass transmission linking box in the background.
The remaining gears are inserted into the brass housing and the two sections re-connected by the final gear and its pin. Also visible is the bogie mounting with part of the Bachmann bogie mounting arrangement glued into the top.
The articulated drive train was then dropped into the etched bogie chassis just to check nothing was catching on something else. When the springs are in place, the plastic drive train will be held further up inside the brass chassis.
Next the bogie mounting was dropped over the bogie, again to check for clearances/clashes. Once the secondary springs are in, the mounting will sit higher up, giving even more clearance.
So far, everything appears to fit as it should with nothing catching or binding.
I can't really do much more with the trial assembly till I've put the driven wheel sets together. The Bachmann axles have to be taken apart to release the drive gears and these then have to be bored out to fit the full width 2 mm axles. A friend who does clock and watch making has very kindly offered to do this on one of his small lathes, so they are with him just now.
The trial assembly has allowed me to have some ideas about pick-up arrangements. Clearances require removal of the existing Bachmann phosphour-bronze strips. The PenBits instructions are based on shorting out the wheels on one side of each bogie but I don't fancy that and need to find suitable positions for conventional wiper pick-ups.
The final bit of work has been to start to get the plastic outer bogie frames ready to fit to the PenBits mountings. This entails cutting out the various cross struts and the base of the moulding and removing the coupling mount. The inner end strut has to be removed after gluing the frames to the brass mounting assembly. I've also cut out the holes where the extended axles of the front truck poke through. Suitable axles have been sourced from the part finished Lima conversion, mentioned below.
I'm rather disappointed by the Bachmann frame mouldings and some of the jumper cable details, which are way over scale. Years ago, I part finished Lima Class 40 in P4 and, to be honest, the bogie detail is far superior and much crisper. I'd also put on all the hoses, pipes, front bearers and even the AJ couplings, so I intend to try to reclaim and re-use some of these parts. The photo below illustrated the Lima and Bachmann frames (the Bachmann is neared the camera, so looks larger, but they're both the same size!). I broke one of the cab steps off the other Bachmann and these are much better than the Lima, being separate mouldings, but I'm not sure we've progressed much in the twenty years or so separating these products.
Dave.
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