A running chassis, at last!

The gearbox is in, the motor is secured, it's wired up, it's on the rolling road, the power's on and there are NO BINDS! Here's a photo of it in motion:

Here it is static, complete with grubby bits of white insulation for crankpin washers and ridiculous oversized screw holding the gearbox in:

This is what I did to the gearbox. My obsession with it-must-be-able-to-be-dismantled-ability meant that I wasn't happy about having it captive around the driving axles, so I cut a slot into the front of the gearbox which allows it to be fed into the chassis from underneath. It's secured by the screw at the back which makes the mesh adjustable. The axle bearings in the gearbox are just to keep the last two gears in mesh and there's still enough left this way to maintain this properly, and cutting in from the from the front means that it's not affected by up-and-down torque of the box - the only possible movement is fore-and-aft, and the locating screw takes care of this if it's tight enough. I cut the slots VERY carefully with a slitting disc, and was careful to use a bit of scrap 2mm silver steel in the bearing holes while doing it so that I didn't slip and carve a big lump out of the bearing. Even so, I had to file out the final bits and there are a few marks on the bearings, but they look like they'll be OK.

Since doing the photos in the previous post I've cut a small slot in the locating ring nut on the motor to allow it to be tightened. When it came to the crunch this wouldn't tighten up fully, so I've had to add a 6mm inside diameter x 0.5mm brass washer between the motor and the mount - this takes up the thickness of a small boss moulded onto the front of the motor. Yes, I [b][i]know[/i][/b] there's a crack in the solder joint between the gearbox and motor mounting plate (again).

"Linda" - gearbox and motor mount progress

Well, after a long interlude for a holiday in the USA and a few other things, I achieved a smooth rolling chassis. It had a slight bind for a long time which I think was down to:
1. The cranks which I thought were firmly attached, actually weren't. It seems that one of them moved slightly on every revolution. A tiny dab of Loctite B638 retainer solved this.
2. One of the front bearings was slightly too far back in the frames - it was set up with the coupling rod and an alignment jig and pulled forward slightly.

I've now started on the gearbox. I have to confess that I can't actually find the instructions at the moment (that accounts for a lot!) but I think the advice is to glue the motor into the gearbox. I din't like this as I'm more than likely to get it wrong, and it's not adjustable/removable for mesh or maintenance. The little coreless motor has a threaded boss on the front and I'd originally cooked up a rather rough arrangement with a thin nut soldered onto the gearbox etch and the motor screwed into that. I recently stripped down most of the gearbox and replaced it with what you see below.

I've made a small nut (although it doesn't look like one, as it has no flats and concave sides) to attach the motor to the gearbox. The strange shape is because it's dished to only just clear the large idler gear - space is very tight here. It's made from a nut from an old miniature toggle switch, i.e. the nut which is used to clamp the switch into a control panel via a threaded boss. The next photo shows a similar nut and the mandrel I made up from a very mangy old switch to turn down the motor mounting nut. The nut will eventually have a couple of notches to make it easier to tighten up. If you attempt anything similar, beware - these small switches have a wide variety of different thread diameters and pitches, and there doesn't seem to be a standard. I just happened to get lucky and find one with the same thread (I've no idea what standard it is but it's about 5mm diameter).

Lastly, a grainy photo (not sure what happened there) or the motor, nut and the idler shaft. The latter is a bit of 2mm silver steel tapped 8BA at one end and with a head soldered onto the other, to make the whole thing removable. It has a little 1.0mm brass bush to stop the gear wandering sideways out of mesh. 

Backwoods "Linda" Chassis

I've been posting progress on my Backwoods "Linda" project on the NRGM forum, and it only seems fair to add details here for those who aren't members (although it's well worth it if you are a narrow gauge modeller of any sort...)

I've dusted off my own long-stalled Backwoods "Linda" project. I last worked on this about six or seven years ago, and its sojourn in the draw has just gone to prove that you really should take care in removing all the flux, or your kit will fall apart after a few years. It was up to the badly-running chassis stage - the quartering was and out there were several binds, but there were so many problems with the soldering in the chassis I decided to strip it back and start again. The photos below show how far I've got.

Those who have built one of these will notice that the gearbox isn't fitted - I wasn't keen on the captive gearbox idea so I've decided to either adapt the current one to be removable or build a new one. Also, I've made a set of replacement cranks in 1.0mm brass with press-fitted steel crankpins. These aren't perfect but I'm quite pleased with them, although making them - even cutting them together in a batch of four - is a bit of a pain and I don't want to do it again. You may also notice that I've removed the compensation and rebuilt it with rigid bearing - sorry, far too fiddly for me.

At this point I got really ambitious and designed a set to be laser cut, which you can see in a couple of the photos. The eagle-eyed amongst you will notice that I've actually had them cut to completely the wrong size. I've no idea how I managed this since I had a very precise set of dimensions - I'll order up a few new sets and see how they come out. If they're OK, I'll be using some to replace the cranks on my Backwoods "Lancashire" (no, I haven't finished that yet either).

Regards,

Chris

Checking the bearings for parallel

Checking the bearings for parallel and level

First fit of wheels and new cranks

Chassis with unsuccessful laser cut cranks

Close shot of the laser cut cranks. Well, they look nice anyway. The bottom left hand one has had the pilot holes drilled out 0.5mm - the rest are as they come from the cutter

Split Infinitive...

...because it takes me an infinitely long time to finish anything?

Anyway, here are a couple of photos to prove that 1. I can work on more than one kit at a time and 2. I can write more than one post per day.

I decided that I didn't like the idea of Lancashire being rear-heavy and having to weigh down the front to keep it on the track like most model 0-4-4Ts, so I'm having a go at actually carrying some of the weight one the rear bogie. I reckoned that if it was carry weight, it would hold the track well and could usefully pick up current, so the next two photos show my attempts to split-frame the trailing bogie to provide wiper-less pickup.

The bogie link arm has been split by soldering on a small strip of PCB, cutting the insulation slot and then filling everything with epoxy to avoid getting dirt in the insulating gap. The bogie is split similarly but there's a paxolin boss tapped 8BA in the centre - this will take a screw with a large head (not the one on the left) which will act as both an adjustable height bearing pad and the conductor for the insulated side of the bogie - the loco has uninsulated drivers on one side, so there are only two pickups and the frame is live. I'm sure it'll be clear when it's all put together...

The wheels are the originals with the centre replaced with brass and stub axles inserted. Yes, the little black thing is an axle muff and yes, that means there's one missing. I've lost is somewhere, but it is only 4mm long so I think I that's a reasonable excuse.

Up On The Roof

(Well, everyone else uses either awful puns or song titles for their post headings).

I have a little detailing job on the roof of the Ingersoll-Rand Oil Electric (Did I call it a "gas-electric" previously? Yes, I did, but I now realise that it says "Oil Electric" on the box). The cooling unit is a big lump featuring what is presumably a large fan with a radiator on either side. This has six water pipes running into the roof and these locate in little cast plugs - basically these are small bits of tube which form part of the main roof casting.

I've built the cooling unit to be removable for painting and it's held with an 8BA screw from inside the roof casting, and the plan was to fit the pipes to the unit and have the ends loose in the roof fittings. My rather heavy handed assembly and the natural softness of whitemetal means that several roof fittings have been mangled, so I've worked up some replacements which hopefully look a bit more elegant. Anyone else would have just bought some brass tube, but I couldn't be bothered. And the shops had closed.

The pipework is 0.9mm brass wire, so I produced a couple of lengths of 1.6mm brass rod with a 0.9mm hole (i.e. the bit of brass tube that I didn't buy). This was cut into six lengths and the ends faced off in the lathe to be nice and presentable. I've started to slice off the original fittings and replace them with tube as shown in the photo on the left. Hopefully these now look like pipe flanges fitted to the surface of the roof, and won't leave unsightly gaps when the paint goes on. You can see where I've broken one of the original fittings on the inboard side of the cooler in the photo.

This shows the flanges a little better on  the two front water pipes. I wanted to make the pipes as close a fit as possible to be able to paint and weather the the cooling unit separately before fitting it to the roof. I've tried to make the roof modular as it has a lot of surface details and lumpy or overdone painting would show up badly (sets standard to fail be in near future...). 

This shows the inside ends of the pipes ready to be cut flush with the bottom of the roof. The brass screw in the centre holds the colling unit in place and below and to the right of that are the original holes for the other four coolant pipes. 

Finally, this is a view of a bit more of the roof including the exhaust units - the centre panel holding these is also removable and fixed by a 10BA screw from underneath. The collection of brass tube in the foreground is the other four cooling pipe flanges waiting to be fitted.

Hopefully this may be of use to anyone else building a Backwoods Box Cab Oil Electric. I can tell you now that - with the exception of a couple which Pete McParlin built himself - this is actually the only built one I've ever seen. Now there's a challenge.

The Boxcab - finally working

I seem to be making a habit of posting once every twelve months. I'm sure that's not what blogging it about so I'm going to make a real effort to be a bit more prolific.

I eventually got around to working on the boxcab, so here is a short video of it running on the rolling road with its new fly cranks.

Once it gets moving the loco starts to rock quite a bit - there's no binding in the cranks and this appears to be due to one of the wheelsets being eccentric on its axle.

Apologies for the wallpaper - the workshop really needs redecorating...