More crank problems

It's been almost exactly a year since I posted here so I'm long overdue for a new entry. I've made pitifully little progress and more backwards than forwards at times, but you may be interested in the latest problems with my Backwoods Ingersoll-Rand gas-electric.

In the previous post I showed it sitting on its elderly but intact and working Liliput OBB 2095 diesel chassis. These are fairly difficult to find nowadays and I was quite pleased to find this one - this was tempered with disappointment shortly after I made my last post when I dropped one of the power bogies and managed to crack all four of the plastic cranks. This was not a positive development.

You may just be able to see in the photo that there's a crack running from the centre boss up through the crankpin hole to the outside of the crank. The cranks seem be moulded in nylon and although it is possible to glue them (with the magic of Dr Mike's) this doesn't hold once the push-fit crankpins go in - I'd have been quite surprised if it had.

So it sat in the display case for months while I tried to think of a solution that didn't involve buying a new chassis. Now, I've been working on a couple of new kits recently and there was space on one of the etches for a few odds and ends, so I set to work to see if I could make a solution...

And I came up with these. They're a fold-up crank with 0.3mm pilot holes for the crankpin and the axles.

I wasn't sure how I was going to progress from there but it was a start. After the customary few weeks sitting in a drawer I doodled a design and started to turn up eight axle bosses. The Liliput axles are 1.50mm and I've bored them 1.3omm to give plenty of room for reaming out. I haven't decided on how to do the crankpins yet but I fancy some sort of screwed system rather than washers soldered on the end of plain crankpins I'd like to re-use the original plastic coupling rods if possible, so keeping them clear of the soldering iron seems a good idea. I've broken enough bits already.

The last photos show a soldered-up crank and the blank for one of the bosses, and pair of cranks, one with a boss soldered in place and trimmed and the other without its boss.

I think I've now worked out how to finish off the cranks and just need to solder up all eight cranks, fit the bosses and finish them off. I then have to work out how to fit them. I'd like to press fit them but I'm not sure about the tolerances required to get this just right so may depend on Loctite or lowmelt solder in the end. I also have to work out a plan for the crankpins an I suspect that doing those properly may take time (and money).

The Living Dinosaur

I've restarted work recently on a Backwoods Ingersoll-Rand boxcab kit which I've had for many years now, so here are a few early shots. The kit isn't - as far as I know - based on a particular prototype as I don't think they ever had outside frames, but it gives it plenty of character on its Liliput 2095 chassis.

This the the basic body and roof assembly - the roof is a large lump of cast whitemetal which won't do its centre of gravity any good, but it gives pretty good traction. I assembled the roof with the radiator and exhaust assemblies removable. The plan was that I'd replace the roof with a cast resin copy to reduce its weight, but I'm not sure if I'll proceed with this. This next photo shows the roof dismantled into sub-assemblies.

The last photo shows the current state of progress. It's a nice runner, but there's still a long way to go...

More on the Japanese 0-4-0T

In the true spirit of this blog, a) this is my first posting for months and b) it's about something I haven't quite finished yet. The little 0-4-0T is sold as a "Feldbahn" by Yoshiya Kobayashi (see his website). I think a few people have interpreted this as meaning it's "Feldbahn" as in a WW1 German Army prototype, but the term is also used in Germany to designate any small industrial railway, and that's what this appears to depict here.

It appears to be a fairly accurate copy of the original Eggerbahn "No.2" locomotive - I do have a scan from an old Egger catalogue of this loco but was wary of reproducing it here, as I'm not certain of the copyright since a Swiss firm started to produce very expensive replicas of the old Egger range under the same name.

I think it's probably based on a small Koppel, so that's what I'll call it for clarity's sake. I've made a few modifications to the original, some of which you can see in the photos. The first was a tool to hold the crankpins, which featured in my blog back in November - this was made purely because I couldn't assemble the kit any other way as the parts were so small. The fact that the crankpins are screws with no slots doesn't help. Other modifications include:

Cutting a vertical slot through the motor bracket so that it could be removed along with the chassis. The chassis - the main portion of which is a Japanese 3-axle motor bogie with one axle cut off - is slightly odd in that while it screws to the bottom of the footplate, the motor screws separately to the top. This means that if you build it as supplied, once the motor pickup wires are soldered on at both ends, you can't drop the chassis out. This slot allowed me to do that. The photo below just shows the slot in the front of the bracket. The next photo down shows the main body components.


Making a completely new pair of crossheads. The originals, while being only about 3mm x 3mm, were designed to be soldered up from a flat piece of N/S sheet, with a U-shaped strip soldered across the back which had a 0.3mm N/S wire soldered into it to represent the piston rod. Once this was done, the whole lot had to be kept in one piece while soldering in the con rod small end crankpin. Needless to say, I found this impossible. I milled a new pair out of solid brass, and they work just fine.

The cylinder castings are meant to be glued to the motor bogie-derived chassis, which is made from some sort of ungluable nylon. After a few attempt with epoxies, I managed to get them to stick with Dr Mike's - a fantastic product which, whilst a bit expensive, is the only thing I know of which will glue this stuff.

So there you are - a nearly finished Koppel. Since I took the photos he's had the awful mistake of the gloss black cylinder paint rectified and wears a neat set of "No. 2" number plates as supplied with the kit. And lastly, a photo of the little feller wandering through the foothills of Snowdonia - how bizarre...

Disaster - my cranks have fallen off!

It had to happen. After gloating in a previous post about how well Lancashire was running, I moved on to adding the valve gear and con rod to the left side. The valve gear is now built up into thre sub-assemblies and ready for fitting.


LHS gear ready for fitting

So Lancashire took to the test track to limber up before the first stage of adding the rods. And while trundling along happily at low speed, this happened.


Calamity on the test track

Yes, the flycrank has come off. In fact both the fly cranks fell off at the same time. Remarkable.

The closer photo below sheds a little light on what's happened. It looks as though I've soldered on both cranks with only a small amount of solder actually making the connection, resulting in a weak joint. In addition to this, there's been quite a bit of flux left behind inside the crank, corroding the axle. Presumably this has worked away at the joint until there wasn't enough left to maintain the joint. The morals of the story seem to be:

• Make the crank a tight fit on the axle to ensure nothing nasty can live in the gap
• Only add the flux from the outside
• Make sure you get enough solder on to make a proper joint
  

This ain't one going much further...

'Canopus' - disassembly for painting

My Backwoods Canopus has been around for many years and I still haven't finished that either. I've got it to the stage where the chassis is complete and running - although I have to admit it's not very smooth - and the body is complete and just about painted.

Canopus in her present state

The whole thing is designed to dismantle quite nicely into the three major assemblies of cab/footplate, boiler/tank and chassis. I went one step further and attached the tank to the boiler with a 12BA screw to allow it to be removed for painting. This is great until any strain is put on the screw - in my case it to was due to a child-related incident...

The problem is that tapping into whitemetal isn't a great idea, as it works well initially but wears quickly if you take the screw in and out a lot of it or if the hole was a bit too big when you initially drilled it - in the latter case there's not much thread on the whitemetal to start with and it quickly wears away. In my case, a shock to the thread managed to strip it completely.

Canopus boiler and saddle tank

In the photos you can see that I've added little tapped 12BA brass inserts to the two tapped holes, one in the end of boiler weight where it's attached to the cab, and and one in the bottom of the tank. These are glues into tight-fitting holes with cyanoacrylate ("Dr Mike's", in this case). These are turned up from scrap brass and tapped 12BA, but you can do it easily enough without the aid of a lathe by using a 12BA nut or a length of brass tube tapped 12BA. The tricky bit is not getting the glue into the threads, but you can avoid this by lightly oiling a screw and running it into the thread, then cleaning off any oil on the outside before glueing it.

Cruel front-end enlargement

Quartering jig parts

For those who appreciate blurry photos of bits of brass, here's one of the quartering jig parts.



They are (top to bottom)

1. Top - 2mm mild steel drilling jig. All the other parts are drilled from this and it's what gives the jig its accuracy.
2. Row of 6 brass spacer bobbins. The inner two are the smaller back-to-back spacers, the outer four are to space out the crank locating plates.
3. Left side - two 2mm silver steel rods tapped 8BA to clamp it all together
4. Centre - left and right are the 2mm steel crank locating plates, centre are the two brass supports for the axle - note the cutout at the top.
5. Bottom - two 3mm silver steel rods - these are a fairly tight pushfit through the various plates and allow it all to line up consistently.
   

Lancashire's Boiler

I'm having some difficulty in getting Lancashire's boiler, firebox top and smokebox to line up. The firebox top casting (see first photo) fits between the tanks and makes contact with the top of the brass boiler, but there isn't really any room to make a positive connection between firebox and tanks to ensure that all is level and square.


Boiler parts

So I produced the jig seen inside the boiler using some old bits of brass (and a huge lump of 1/2" silver steel - don't ask what that was intended for). This also involved drilling a 2mm hole through the length of the boiler weight. The whole lot was strung together on a bit of 2mm silver steel threaded 8BA at the ends (yes, like the Quartering Jig - I'm not wasting my new 8BA die) which clamps it all up solid. The idea is now that I can create something to hold the whole lot steady within the body while the smokebox and firebox top are fixed in place, leaving the rest all nicely lined up.


The boiler on the jig


The jig in all its glory