Muir Hill rail tractor (Branchlines)
Entry posted by 47137 in Locomotives ·
3,850 views
7 June 2017
My new project is to build the Branchlines kit for a Muir Hill rail tractor in H0 scale - something a bit different for the layout. This kit is unusual in that, as well as being labelled as "00/H0" it really does build up into a passable model for either scale, though you have to decide which before starting. The prototype is so small that any discrepancies in major dimensions are going to be tiny. This is a complete kit, supplied as a set of whitemetal parts and a Tenshodo 'spud' motor bogie. I bought it from the Branchlines stand at the Chatham show last weekend.
In essence (to try to be succint), the kit is supplied to build for 00 with undersize wheels. For a better 00 model you can change the Tenshodo 10.5 mm wheels for 12 mm ones and omit a packing piece under the footplate. For H0, you keep the 10.5 mm wheels, omit the packing place and drill fresh holes to put the buffers closer together. If this sounds a bit "freelance", bear in mind the footplate is 27 mm wide, the wheelbase is 24.5 mm, and the most-eye-catching feature of these engines is their seemingly huge disc wheels. It really should work for a layout in either scale.
My first impressions are good. The instructions are clear and easy to understand - one side of A4 with a list of step-by-step instructions and an exploded diagram, with the parts numbered on the diagram to match the steps. Everything makes sense even if you don't have a photo of a prototype to hand.
All of the body parts are whitemetal. This is the cleanest set of parts I have seen for a whitemetal loco kit, but then again it is my first "modern" such kit. I've only tried kits from Wills and K's before, so this is a bit of a revelation to me.
On inspection, one of the buffer beams didn't get quite enough metal poured into the mould (perhaps there was an air pocket) so I have made a start on the kit by building this up with some slow-setting Araldite. I put a strip of clear sticky tape onto the front of the buffer beam, laid the part on the bench, and added a blob of the Araldite. When the glue was fairly firm (but not rock-hard), I peeled off the tape and trimmed the blob to size. The adhesive on the tape sticks to Araldite better than it sticks to the tape. The repaired buffer beam is at the bottom of the photo. The packing piece (which I won't be using for H0) is bottom-right in the photo.
8 June 2017
I imagine, construction will be in four stages:
1. The footplate and downwards.
2. Getting it to run.
3. Upwards from the footplate
4. Details and painting
At the moment I am thinking along the lines of a permanently-coupled wagon or even a brake van, so the engine can make its appearances on the layout as a sort of civil engineering / internal user train.The coupled wagon to have extra pickups. The engine to be painted yellow all over, as a last-ditch attempt at modernity by the railway company.
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I did a minor dummy run of construction yesterday to see how the footplate and buffer beams will sit in relation to the chassis, the wheels and the track. The model needs an insulating shim between the footplate and the chassis, to stop the footplate making a short circuit against the two motor terminals on the top of the chassis - the shim can be a slip of thin card or styrene or even paper. The Tenshodo motor bogie needs some ballast and adjustment to make it run on a layout. The quality of the Branchlines castings is top-notch, better than some plastic kits.
The bottom edges of the buffer beams will end up about 2 mm above the rails. For British H0 I want the centres of the buffers to be 20 mm apart and about 12mm above the rails, so I drilled new holes for these in the buffer beams. Then I filled in the original holes with a car body putty.
I found some turned brass buffers on an old K's kit for a wagon, and I will use these on the engine. There is nothing wrong with the cast buffers supplied by Branchlines, but the brass ones have a finer appearance. The brass buffers have a threaded shank, and I found I could screw these into 1.5mm holes in the buffer beams without needing to tap the holes. Dumb buffers from scraps of wood would be a good alternative.
I straightened the footplate between my fingers to make it flat, and then glued on the two solebars and then the two buffer beams. I have some low melting point solder but it seems difficult to solder small castings of white metal onto large castings, and even harder to solder large/thick castings together. So I followed the advice in the instructions, and tacked everything together with a thick / non-runny cyanoacrylate:
Then I had a look at the motor bogie. The wheel back-to-backs measured most of 15 mm, which would explain why the thing climbed off the track at the points. The axles have extended ends, so I put the wheels in the vise in a sandwich between two nuts, and then pressed everything together onto the back to back gauge (14.5 mm):
Then I put a cutting-off disc in the mini-drill. and cut off the extended axles flush with the faces of the wheels.
The model uses one of the U-shaped brackets supplied with the motor bogie to hold the sandboxes, so I put this bracket in along with the wheels:
Then I glued on the two sand boxes.
I have got my doubts about this motor bogie because the backs of the wheels now seem to be rubbing against the moulded chassis, with no sideplay at all. However it seems worthwhile to get this far so I can mix up some slow-setting epoxy resin (Araldite) and dribble this into the crevices of the joints:
Looking at this last photo I'll try to square up the crooked sand box before the glue sets.
The idea now is to attach the footplate assembly to the chassis, add temporary weight and a coupled wagon as needed, and get the model to run nicely before adding the superstructure.
9 May 2017
Setting the wheel back to backs yesterday almost locked the chassis up solid, so the first task this evening was to slacken them off a bit. It seems impossible to open up the back to backs in situ, so I took off the keeper plate again and reset them in the vise, with support from the B2B gauge and impact on the axle ends using a nail as a centre punch. The wheels are much tighter on their axles than some other brands.
I forgot to measure the new setting but they are now around 14.7 mm - wide enough to rotate, narrow enough to run through Peco Streamline turnouts (Code 75) but probably not reliable for H0-SF. This might be annoying, because my harbour section is H0-SF, but then again the engine probably won't get used here much.
The chassis is reasonably free-running now, but with a 14:1 reduction ratio and no flywheel it is a bit snappy. It starts without much prodding, and even runs fairly smoothly, but it seems more useful to call this the chief engineer's inspection loco rather than a shunter. With this in mind, I've given up on the idea of a permanently-coupled wagon with extra pickups, it will be more fun to send it out as a light engine. This also saves me trying to fit Kadee couplers.
So I am encouraged enough to go back to the superstructure. This needed a notch cutting behind one of the buffer beams to let the chassis fit snugly up inside. I put a bit of sticky tape under the footplate above the two motor contacts (which I don't need to use now) to prevent shorting, and two layers of thick paper at the other end to keep the footplate level on the chassis.
None of the above photographs very well, but the cab details do. I added the driver's seat, the brake and the transmission cover, and assembled the cab sides, all tacked together with cyanoacrylate:
The parts are nicely made - I ran a file around the brake column and along the bottom and top of the cab sides, but everything fits together without adjustments.
My approach now is to reinforce the joints with Araldite. I mix up the smallest blob I can, and warm it with a hot air gun. Then apply it around the joints with a cocktail stick, and apply the hot air again to let it draw itself into the joins by capillary action. The quantity of heat here is very small, just a few seconds. Then I glued the cab sides down onto the footplate with more Araldite, and this is the result:
The engine cover (bonnet) is still loose. I used it to make sure the cab sides are square on the footplate. Then the engine cover will fit without needing filler against the cab front. Quite cute really:
So again, progress stops to wait for the glue to set overnight. This is no great problem - I'm probably spending more time taking photos and writing it up than actually building the model. I shall have a think about using some etched brass ladders instead of the cast side steps.
10 June 2017
The more weight I add the the model, the better is runs so I started today's session filling the engine cover (bonnet) with molten whitemetal and then some lead shot. The molten whitemetal is a simple enough idea - put the offcuts of whitemetal in a foil dish, heat to melt with the hot air gun, allow to cool very slightly, and pour while still plastic. This works when the quantity of metal being poured is smaller (less heat capacity) than the casting you are trying to fill. It does not work(!) if the molten metal has a larger mass than the casting being filled. Let it suffice to say, it filled half the bonnet before burning through the top and leaving a lump of metal sticking out. Well, it won't fall out.
This did not actually destroy any detail, so I cut the lump off the bonnet with a hacksaw and filed it down to match the curvature of the casting. However, enough is enough so I filled the rest of the space with fine lead shot (sold as "Fluid Lead"), bedded down into puddles of cyanoacrylate. This takes the weight of the bonnet up to 23 g, and the whole model up to about 90 g.
Moving on do the starting handle, I drilled a small hole in the front of the bonnet (there is a blind hole here in the casting), and pushed in the length of brass wire supplied in the kit. I left the wire over length, bent it to form the handle and then trimmed the wire to length. Branchlines supply about six inches of wire, but this is the only detail where the wire is called up in the instructions.
There are two sets of footsteps, one each side of the footplate. The kit includes castings for these, but they look a bit chunky (especially in H0) so I used some brass signal ladder instead. I took the sections of ladder from the ends of the ladder etches where they join up with the selvedge. The selvedge bends around to form the bottom step, glued under the sand boxes.
The final details today are the four brake hangers. These are supposed to be fitted into holes drilled in the footplate but I don't have a fine drill bit long enough to reach past the wheels and buffer beams. I might have drilled the holes before I started, but finding the locations would have been been difficult. So I held the hangers in place with Blu-tak, and then put blobs of Araldite around the joins where they meet the footplate. Being whitemetal, they should bend easily enough later to make their final alignments.
I finished today adding Araldite around the bases of the footplate steps and on both sides of the cross-piece which holds the sandboxes. The cross-piece is supplied by Tenshodo, and it kept wobbling around. If I take off the keeper plate, the sandboxes and ladders will come away with it, but this should not be a problem. The brass ladders will be terribly fragile, but probably no worse than details on some modern RTR models, and they should look the part.
The only parts left now are the cab roof and the coupling hooks. I will omit the hooks while I see if I can find some brass ones, and I will fix the cab roof and the bonnet assembly after painting.
11 June 2017
This morning, the engine was essentially complete and the locations of the buffers are just right against this Roco 350hp EE shunter:
However the model would not run properly, getting hot after a minute of running.Heat means friction, and the only thing left (having opened up the back to backs again) seemed to be incorrect meshing of the worm gears to the worms. To try to ease this, I ran a flat file across the keeper plate where it retains the axles:
I put tiny drops of oil onto the motor bearings too, and after reassembly the running is a bit better. The engine does not have couplings but it will propel a couple of short coaches - no fear of buffer locking with a 25 mm wheelbase:
The model is more controllable when it is loaded up with a train, but it is still unable to start slowly or creep on a non-feedback analogue controller, and the motor bogie was hot to the touch after ten minutes of running around my circuit of Kato track. I can hope the motor brushes will bed in during the next few running sessions, but the model isn't going to be suitable as a shunter without a lot of manual intervention. To try to quantify its performance, it is about as good as a second-hand model sold at a swapmeet as "runs well" - it runs, and at a few different speeds, but it is poor compared with most any modern RTR model.
The model is good enough to run a short train along the main line of the layout, and it's size looks right against an H0 train. The Branchlines kit itself is marvellous, the castings are of good quality and go together easily, but the model deserves a better chassis. I cannot help thinking, Tenshodo must surely have built their reputation a better standard of motor bogie.
I need to think about drilling some holes for handrails, and then set about painting the model. I mentioned yellow earlier in this post, but I've found an aerosol of dull matt green, which will probably look better. I bought the kit last Sunday (4th May), and it is good to see results within a week.
9 July 2017
The motor bogie has been an appalling runner, seizing up after running for ten minutes or so and needing to be left to cool down before it will move again. This implying something is binding. Conversely, turning the wheels by hand the axle below the cab would turn with a clicking of gear teeth, as though the worm and worm gear were too far apart to mesh properly.
Looking for a quick way out have I removed the worm gear from this axle, so the engine is now running as an A1 (or a 1A) instead of a B. It has run for thirty minutes at middling to high speeds around my oval of track, getting slightly warm to the touch but not hot. Traction with only one axle driven is minimal, but the model does actually run. It is better with the cab leading, that is with the driven axle trailing, but “better” is still a long way short of “good”.
So … I need to decide whether to stop here and accept the model for what it is, or buy a replacement motor bogie. This design of motor bogie is always going to be a snappy sort of runner – the gear ratio is 14:1 and there is no flywheel, but I am sure it ought to be better than it is.
To anyone contemplating this kit (and it was fun and straightforward to build), I would build the body first, then fit the body to the motor bogie, and leave all the modifications to the motor bogie like trimming the axles and adding the sand boxes to the very end, after the model is seen to be running well. Perhaps, as Captain Kernow has suggested in one of his comments, there is an alternative power train out there.
11 July 2017
No more modelling yet, but here are some photos to help ideas for a better chassis following on from Captain Kernow's comment on 10 July ...
Firstly, looking square on underneath we can see the chunks of whitemetal behind the buffer beams. These are a little narrower than the Tenshodo chassis, and maybe they could remain to support the two sides of a scratch-built chassis:
Alternatively we could cut out one or both of them, for example to make room for a gear box. Here is a High Level motor/gear box assembly, the gear box is one with a double reduction gear. If building for 4mm scale then with slightly oversize wheels - say 13 mm instead of 12 mm - there would be just enough room to lift the final drive gear above the tops of the rails:
If I had not filled the bonnet with lead shot, it would contain the motor with the forward spindle cut off:
This would produce a model with little adhesion but it would be controllable at shunting speeds. Moving on, perhaps the driven axle should have traction tyres to get a bit more grip, and the engine be coupled to a wagon with extra pickups to keep it going over over points and so on. But if it is going to have a wagon permanently attached, the power train can be in the wagon. Shades of Kitmaster or perhaps a Wickham trolley I suppose, depending on your age.
This all really needs to be thought through before starting the build.
The engine could have gone out on the main line of my own layout for a bit of fun from time to time, but with only one axle driven now it won't cope with the gradients. I bought some spare gears with the kit (I was warned about splitting gears, though this hasn't happened yet), but I have lost them. I am reluctant to buy another Tenshodo motor bogie because even if a new one runs better, the 14:1 gear ratio will always be a bit limiting for me.
21 July 2017
I'm going to put this project on hold for a while. If I was starting this project from scratch I would buy and build the Quad Driver chassis (High Level Kits) and then modify the Branchlines kit to fit it - even if I had to make some deviations from the prototype to fit everything in. But I cannot face chopping up the model I have built so far. I would rather build a Quad Driver and then scratch build a body of something else to fit it.
It is good this is a hobby and there is no need to create a perfect deliverable from every project. Thank you for all the views and helpful comments.
High Level Kits have produced a small number of chassis kits for 3mm scale, and others in their range may be useful for British H0 too.
- Richard.
Edited by 47137
Edit to add entry category for blog
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