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GRS kit Midland Johnson 1F 0-6-0T

Started by John Candy, Mar 13 2014 11:51

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John Candy

Heart surgery!

This evening, the 1F underwent the model loco equivalent of a heart transplant.

You will see from earlier posts that there was a problem with the gearbox jumping out of mesh on the rolling road test run and this damaged the phosphor-bronze gear wheel which engages with the steel worm.

A straight swap-out of the motor/gearbox was not possible since the wheelsets were not the usual Slater's type supplied with most GRS kits but a cast iron pattern with larger 10 mm diameter axles and a force-fit on the axles (supplied ready assembled and quartered).

I had a spare GRS motor/gearbox (bought a couple of years ago for a GNR Ivatt Atlantic tank which I have not yet got around to starting) but this has a different motor to the 1F kit, however, the gears ratios and components were same diameters. First step was to swap the primary gear wheel set (easily done since the spindle on which it rotates is located by two circlips) and then check the mesh..
That was successful but the nagging worry remained that the original problem appeared to have been caused by the worm "climbing" the gear teeth and causing the motor shaft to flex. It was noted that (unlike other motors supplied in GRS kits) this Buehler has a shaft diameter of only 2.3mm and that a "flat" was machined into this for the worm grub screw. The shaft was clearly a weak link and I was concerned that the same thing would happen again and damage the replacement gears. I also noted that the profile of the worm "spiral" was thicker and more "blunt-ended" than that on the potential replacement motor (which has a 3.2mm shaft and a force-fitted worm).

The variations which prevented a straight motor swap were the distances between centres of the screws which hold the motor to the gearbox and, more crucially, the diameter of the "nose" bearing housing, which locates the motor in the gearbox casing. The Buehler motor had a 12mm bearing case but the replacement is 13mm (and the replacement has the mounting screws closer to the centre).

The only answer was to ream out to 13mm the 12mm hole in the gearbox casing and enlarge the holes for the fixing screws (the motor is located and held in mesh by the bearing casing hole, so the screw hole sizes/locations are not critical).

The only awkward part was actually reaming the gearbox casing while still mounted in the chassis but the whole procedure took no more than 30 minutes and I now have a much more robust drive arrangement.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

Here are photos of the parts removed from the loco.
Note the "flat" on the very slim motor shaft, which contributed to the "flexing" under load and consequent gear meshing problem.
The close-up of the worm reveals that the spiral is very coarse and has a rather obtuse angle of attack, certainly when compared with other GRS gearsets and the replacement now fitted (shown in third photo).

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Peaky 556

The worm in your picture looks like a reject to me, as the helix is not cut down to the minor diameter along the whole length.  I am not surprised it jumped teeth, the depth of engagement looks very poor.
As a passing comment on the third picture, the worm seems to be a little offset from the centre of the wormwheel (or rather the other way around). Can you adjust the position of the wormwheel on the axle?
You do seem to have all the problems!

John Candy


The "off-set" looks worse than it is (angle from which picture taken accentuates).

There is no easy means of adjustment....the only method is desoldering the worm wheel from its axle and moving it!

I did  that with the wheel on the damaged (now redundant) gear set and replaced it the other way round (so the "better" edge was in contact with the worm).

I just looked at the gearbox on one of the Pannier tanks I am building and the wheel is even more off-set than on the 1F!

Typical of GRS standard of quality control, I fear.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

Well, two years on (and now the Dean Goods is well on its way to completion), the IF has been dragged into the daylight once again.

Most of the potential problems are documented earlier in this thread so, hopefully, I can make rapid progress since I know what to expect.

I have some parts left over from the 2F kit which I am hoping will act as replacements for the misshapen boiler  and smokebox etched items, as reported by Andy.

Watch this space!


My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

Work has restarted in earnest on the 1F, after completion of the Dean Goods and a couple of weeks since, working on pattern making for another project.

I ordered some 1/16inch thick brass angle (6mmx6mm) to replace the running plate hanging bars (valances) which were incorrect depth and very flimsy.

First items to receive attention are the boiler and smokebox units.
Firstly I checked the parts for concentricity, etc. and (fortunately) all mine are perfectly circular.

Before shaping the smokebox wrapper, I drilled the rivet positions (half etched for punching) to accept brass rivets. Next I annealed and rolled/shaped the smokebox, this consists of 5 components, being 2 spacers, a front and rear profile plus the wrapper.

The front spacer has a hole for locating the smokebox door and both profiles have slots to locate the spacers. The spacers required some fettling to fit the slots and the profiles were then soldered to the spacers, this holding the items together while the wrapper was soldered on. Soldering the spacers first does restrict access for soldering the wrapper but this would seem to be the only way of getting  all square and avoiding (too many) burnt fingers!

Next, in order to assist with locating (and eventually soldering) the boiler to the smokebox, I marked the centre of one of the two "boiler former fronts" (items "O" on the annotated drawing in the instructions....and more about this in a moment) and drilled to clear a 10BA cheesehead screw and a "registration" mark ( a filed notch) was added to identify the bottom of the boiler. Next, the boiler front former was placed on the rear of the smokebox unit and (with the registration mark at the bottom and the former centred on the smokebox) the screw hole was marked and drilled. A 10BA screw was soldered onto the boiler front so that the boiler, when assembled, can be located accurately against the smokebox and held in place while soldering.

Now, more about those "boiler former fronts". There are two and no differentiation in the instructions (both identified as part "O") but one is approx. 1.5mm smaller in diameter than the other. The instructions don't say why there are two nor where/how they are to be fitted. The fact is that the larger of the two is a perfect fit for the boiler diameter, so what is the second (smaller) for?

Answers on a Postcard, please!!

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

The boiler / smoke box unit went together fairly easily ...after some head scratching caused by the lack of plausible instructions.

Attention has turned to the bunker, which on paper looks fairly simple : The instructions just tell you to choose an open or full cab and solder up the parts ...... a rather over simplistic assessment.

Ignoring the kit deficiencies (of which more in a moment) the fact is that these locos had five different patterns of full cab fitted.....the shape of the cabside apertures being the most noticeable difference but roof ventilation also varied. You will have to make your own mind up on what do, since you need to work from a photo of your chosen loco. (An illustrated Review of Midland Locomotives Vol. 3, Wild Swan, provides an extensive selection).

Returning to the kit, the running plate has slots to accommodate tabs on the bunker and coal plate etchings. BEWARE....the slot for the coal plate is in the wrong position!
Derby GA drawing (and numerous photos) confirm that it should sit 11mm to the rear of the slot provided, in fact more-or-less  in the position where there are two, unspecified, half-etch marks on the running plate. You will need to file the locating tab off the bottom of the coal plate. The coal plate has a fold line etched along the upper edge and , when folded, this needs to point rearwards, away from the cab (there are three etched slots along the fold and these will locate the bunker coal rails if building the open cab version). I found that the coal plate was slightly narrower than the bunker space and it needed a little packing (approx. 1mm) in each of the soldered joints where it meets the bunker sides. You may need to file a recess in the middle of the bottom of the coal plate to clear the chassis mounting screw, my coal plate just impinges on the edge of the bolt hole.

The backplate of the full cab has a fold line along the lower edge and the shelf formed by this is neither mentioned in the instructions nor illustrated (there are no diagrams nor any photos of the body assembly). From photos of the "real thing" it appears the shelf is not present  and, on the model is there just as a strengthener.
Before  fitting the cab, I need to sort out the cab entrance spacing. Working from the GA, it should be 22.5mm but (if assembled using the tabs on tank sides, etc.) then you end up with only 18mm (add the hand rails and the crew would have to take a very deep breath before squeezing into the cab). Another point is that the tank sides incorporate the side sheets for the open cab version but, if you build the closed cab, then you need to cut the side sheets off the tank sides.....no mention in the instructions...surprise, surprise!

More soon!

UPDATE : After taking further measurements from the GA drawing and checking dimensions of the kit parts, the cab back sheet needs to be 18.5mm inboard of the back of the bunker, which sets it 7mm behind the coal plate (when in its correct position).The bent "shelf" section of the cab back needs to be trimmed to 7mm, it will then sit on the "lip" of the coal plate (that lip facing rearwards).
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

1F .... the battle continues!

The Coal Plate (and cab back sheet on full cab version).

Whether you build the open cab version or the full/enclosed cab you will need the coal plate.
As supplied, the nickel silver etch has a coal hatch/hole as shown in the photo added to the previous message.

All the photos I have seen show a vertically sliding hatch cover. It has a handle halfway up and another protrusion (difficult to tell from photos whether it is a handle, an eye or a ledge) near the top, which latches onto a hook, to hold the hatch open. I added these items as shown below.

Next, if you are building a full cab, you need to cut the recess in the cab back plate to  accommodate the hand brake. The dimensions are shown below, the recess being protected from coal by a circular casing which protrudes into the bunker.

Photos below show cab interior with brake handle housing in place and the rear of the cab showing the same housing as it projects into the bunker.

If you are modelling a loco in late MR or LMS condition, then the rear spectacle glass was often protected (from mechanical coaling damage) by vertical bars, which could number 3,4 or 5 ..... refer to a photo of your selected loco. The above photos show the holes drilled but the bars have yet to be fitted.

More soon.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

They have the nerve to call this a kit!
It would have been easier to have started from scratch.

Having completed detailing of the cab back plate, I prepared the bunker and cab front for assembly into a single unit.
What I find is almost beyond belief.
The "fold-up" bunker is 2mm too wide, not difficult to rectify, just cut it up and solder together.
The cab back is 0.5mm too narrow... not in itself a disaster but all this shouldn't be happening.
Then, almost unbelievably, the cab front is 1.5mm narrower than the cab back! All this results in a gap of 2mm to be filled by packing out the cab front by 1mm each side.
I have assembled some b****y awful GRS excuses for kits over the years but this one "takes the biscuit"!

Whoever was responsible for this kit should be sentenced to 10 years in the salt mines.

No wonder there are no proper instructions or photos of the body assembly....they didn't have the nerve!

I'll stop here before my blood pressure goes off the scale.
GRS kits should carry an obligatory health warning.

Finally a couple of pictures of the completed cab back section with detailing added (sanding control , brake handle and window bars).

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

Now my blood pressure has subsided, I will get down to sorting out the mess which passes for a GRS kit.

Firstly, as mentioned in an earlier post, the cab entrance was far too narrow. Having taken measurements from the GA drawing, it transpires that the tank sides are 3.5mm too long and that amount needs to be trimmed from them. The bunker needs to sit so that the leading edges are 42mm from the rear of the running plate (in my case that involved opening out the slot in the running plate which takes the tab on the bunker rear).

Returning to the problems of cab width, in order to fill the gap between the cab front and tank sides, I took the "full cab" side sheet etches to calculate the total height of the required infill piece.
Firstly, I found the LH and RH cab etches differed in overall height by 0.5mm  but worse, that they both increased by 1.1.mm along their length, which would leave you with a cab having a forward slant! If your kit has the same problem, you need to reduce the BOTTOM edge of the REAR of the side sheets to restore parallelism (don't reduce the top edge or you will be left with a "wonky" cut-out). Next  reduce the top edge of the oversized part by 0.5mm, so both sides are same overall height.

Then I cut two pieces of 1mm thick brass, each 91mm in length and 3mm in width.
If you are building an open cab version, then you just need to solder these to the inside of the tank pieces, so they line up with the front of the cab side sheets.
If building the full/enclosed cab version, first score (on the INSIDE of the tank side) a vertical line to coincide with the leading edge of the cab side sheet. Then carefully cut away the cab side sheet from the tank top and smooth the edge. Solder the brass infill flush with the bottom of the tank, to align with the mark you scored on the inside of the tank, allowing it to project above the tank top. This takes care of the gap between tank sides and cab front and provides a useful attachment point for the full cab side sheets.
The 0.5mm deficiency in the full cab rear plate width can be taken care of with shims when the bunker is assembled.

Photos. are :-

1) Tank side (the front of which has been folded through 90 deg.) after removal of the open cab front sheet, reduction in length by 3.5mm and having the packing piece soldered on.

2) The bunker after being "cut and shut" to reduce width by 2mm.

The next job is to solder up the bunker and coal plate/rear cab section, followed by marking the tank front "wrap around" prior to filing to correct profile to provide clearance for the boiler.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

The Cab

At an early stage (when comparing photos of my chosen loco with the kit parts) I gained the impression that the enclosed cab side sheets were too long.
Now I have been able to position the re-sized tank sides and the rebuilt bunker in their correct positions on the running plate, my have suspicions been confirmed....the cab side sheets are 3.5mm too long!

So I have now made three adjustments to the side sheets (including two mentioned in previous post) :-
(1) "Level" them by reducing the rear sections only by 1.1mm in height.
(2) Reduce the overall height of the over-sized one by 0.5mm
(3) Reduce the lengths by 3.5mm

How to reduce the length?
I should explain that the kit has the cabside sheets marked out (with half etching) so that three of the five possible cab shape variants can be produced (see photo below).

My chosen loco (1670) has the shape of cut away provided by the parts as supplied.
After careful examination of photos of locos with the required type of cab, it became clear that the excess metal needed to be removed from the leading edge.
If modelling a loco with an alternative cab shape, you need to assess the situation and not follow the above step.

The cab roof length will have to be trimmed to match the reduction in the cab side sheets.

Real Progress at Last!

The boiler unit has been soldered to the cab front plate.

First things first : The cell pack has to fit in the boiler (there is really no where else it can go) so ensure the chosen pack can be inserted (and removed for eventual replacement) once the cab front has been attached. I am using a flat (7x2 cell 16.8V) pack which fits nicely.

There is a half-moon boiler former which (instead of soldering inside the boiler) I soldered to the front of the cab in order to locate the rear of the firebox (having very carefully determined and marked the correct location using gauges).

I assembled on plate glass and checked the boiler unit was dead level, the cab front was precisely perpendicular and "square" to the boiler unit. Only when completely satisfied was the cab front was soldered to the end of the firebox.

I feel the worst is probably now over but am aware of several issues which need attention when it comes to the running plate and buffer planks, etc.

Next job is to mark out the holes which require drilling in the boiler unit for the handrails, ejector pipes, etc. and I will then attach the chimney, dome and safety valves.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

The Tanks

A substantial amount of material needs to be removed from the front of the tanks so they fit around the boiler profile.
I scored a light line 5mm in from the edge along each side of the running plate, to mark the target position for the tanks.
With the boiler/cab front unit in the correct position, the tanks can be positioned by aligning the leading edge of the cab (open cab) or the vertically projecting packing piece(enclosed cab).

The "touch point" of the tank front with the boiler was marked and the deflection of the leading edge of tank side (by reference to the line previously scored on the running plate) was measured. The tank front can now be roughly marked to show the quite large section which requires removal.
The top of the tank front wraps around to meet the boiler but the lower section (below the "touch point") only very slightly curves around the boiler before dropping vertically to the running plate. The lower section of the tank front needs to be 22mm in width. I used a saw for the major trimming, followed by careful filing, until a perfect fit had been achieved.

Next the tank tops need to be trimmed in both dimensions, to fit between boiler, tank sides and cab front.  The surface of the tank top needs to be 2mm below the upper edge of the sides (score a line on inside) and you will need to measure the gap between tank side and boiler at that depth, to determine the amount to be removed from each top piece. To be taken only as a guide, I found it necessary to remove 3mm from each. Next trim to length so the top fits between tank front and cab front.  Before fitting the tank tops, drill a hole (to take the tank water valve control wheels ... not supplied in the kit but see my later notes) if required.

Clacks and Tank Tops

Firstly, the castings for the injectors/clack valves ..... look nice don't they?

Well, looks can be deceiving because the pipework is cast back-to-front : The pipe should crank outwards away from the boiler, in order to clear the splasher casing. Amusingly, the GRS display/publicity model has them fitted wrong way round! Options are to replace the pipe or to cut away the boiler fixing spigot and replace on opposite side (will decide later on that one).

While we are on the subject of castings, let me draw your attention to the tank tops. The tanks have stays connecting them to the boiler but they were of two types : The earlier type for the type "A" boiler (round top as in this kit) and  later type "G5" boiler (the Belpaire rebuilds). The parts supplied with the kit only apply to the G5 Belpaire boiler! The earlier type are very different and located in different positions.

You need to fill the slots in the tank top as shown above : I will describe the replacement stays in a later post.

When you buy a kit like this, by the time you have trimmed and reshaped most of the etched parts and replaced some of the castings you begin to wonder why you didn't just go out and buy a few sheets of brass, some wire and brass profiles

Now for some better news!
The etched plates for 1670 arrived from Guilplates and the "makers" plates are particularly nice, although I am not sure they should be red for this loco in LMS condition.

My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

Now,"We're cookin' with gas"... in both senses, literal and metaphorical!

Yesterday was a heavy metal day, devoted to fixing the brass castings to the boiler unit.
The chimney required the base to be reduced in diameter (to clear the smokebox rivets) and then thinned. The dome and valve cover each needed a bit of tidying to remove casting sprues  and then the tops drilling out.

The Salter spring castings were not quite right and (as I did with the 2F) I modified them by cutting the square "block" off the bottom ends, then soldered a 7.5mm length of 3/32 in. brass tube over the stub, followed by a short length of 60thou brass wire into that tube....see photos below.

Above left, as supplied and right, truncated prior to addition of tube and wire.

Above shown modified and in situ.

All the assembly was done using the butane micro-torch and it made very light work of the job and the Carr's solder cream left very little cleaning up (just some flux runs).

After several days spent trimming and re-shaping etched parts, it is nice to have some visible progress.

Next jobs : Drill holes for the handrails and pipework for vacuum ejector and clack valves/injectors and attach the the boiler strapping bands using the RSU.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

John Candy

Just when I thought it would be plain sailing from here on, this kit still had an Ace up its sleeve!

First, the easy bits.
The boiler bands have been added using the RSU. A bit of nice design (now there's a compliment) is that the locations are etched into the boiler and the straps/bands are half-etched with a locating "rib" along their length....and they fitted perfectly, making this a quick and easy job!

The splasher covers were fitted but, instead of wrapping over the front pieces, were fitted inside, so as to be flush with the tops of the fronts (otherwise the beading will appear too "fat").

Next the front frame extensions (which locate the cylinder front cover) were soldered to the smokebox saddle (the smokebox/boiler still being a separate unit from the running plate). The cylinder cover itself is a little too narrow, so instead of attempting to solder to the frame extensions, this was shaped and then soldered to the running plate by its front edge (while the top/rear supported against the loosely fitted smokebox). The small gaps either side of the cover will be filled after fixing the smokebox to the running plate.

Now the kit plays its Ace.

The bugger beams (no, not a typo) are just that!
I already knew from what Andy wrote at the outset of this topic (a couple of years ago) that the hanging bars (valances) were too deep and that the buffer beams likewise needed to be reduced. I had already cropped 2mm off the lower edge of the beams and used 6mm x 6mm  brass angle for the replacement hanging bars. The drop ends of the originals were cut from the etches and soldered at the ends of the angle (they need re-profiling to match the reduced depth of the straight sections).

A  very weak point with all the etched brass  GRS loco kits are the flimsy buffer beams and I was already in the process of beefing up the arrangement BUT I had not anticipated the buffer beams being too narrow! The etched parts are 2.5mm narrower than they should be, with the result that they only just touch the ends of the hanging bars , instead of overlapping by a noticeable margin. This stopped me in my tracks : Do I scrap the buffer beams and make new or bulk them out with thick brass? That's enough for today....... I will sleep on it!
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.


Quote from: John Candy on Sep 28 2017 21:37
A bit of nice design (now there's a compliment) is that the locations are etched into the boiler and the straps/bands are half-etched with a locating "rib" along their length....and they fitted perfectly, making this a quick and easy job!

That is really quite clever.  I have half etched a strip around the boiler the width of the band so that the full-thickness band "clicks" into the slot.  BUT the GRS method means even if the etching is a little heavy or light, meaning the locating slot is a little narrow or wide, the join will always be completely hidden.  Why didn't I think of that!  Well done Michael!