Author Topic: The "Plastic Bugger" .... aka GRS kit for GWR 8750 Pannier.  (Read 3433 times)

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Offline John Candy

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Re: The "Plastic Bugger" .... aka GRS kit for GWR 8750 Pannier.
« Reply #15 on: December 28, 2017, 08:10:42 PM »
Have continued working on the cab which has proven to be a bit of a "bugger", not least because of difficulty accessing the interior to measure and fix the detailing!

The exterior: Note the reshaping of the floor at the cab entrance, the addition of door handles and top edge beading to the doors. The doors were set crooked in the casting and were slit along  the offending edges and glued back parallel with the entrance apertures.

The interior : This took a lot of sorting out....largely the result of being supplied with a bag containing a large quantity of small castings which had no means of identification and no instructions on assembly.
A whole day was spent just trawling through books and the web to find close-up views of the cab interior and identifying the parts.
The best advice I can give is to ignore the photos which accompany the instructions (they appear to be taken using  a different, brass, kit ) and use photos from preserved 57XX locos.

A major trap (literal pitfall) awaiting you, is the location cast into the floor of the cab to locate the reverser.  DON'T do as I did and plant the reverser into it. Fortunately, I immediately went on to fit the rear axle springs and positioned the cab floor into the cab shell to check the height : It was immediately obvious that the lever was sitting far too low and was not far enough out from the centre line. Luckily, the superglue had not fully cured and I was able to remove the lever rachet from the "pit" without damage to either part. The "pit" was then filled with Isopon and the reverser re-positioned, a "casing" (visible in photos) also being added to the inboard side of the rachet. Note the position of the smaller lever adjacent to the rachet and springs....it is in a very different position to that shown in the instructions.

The Running Plate : WARNING
The hanging bars (a.k.a. valances) are steel angle (brass on the model) but note that the flange fixed to the running plate faces outwards  NOT inwards on 57XX locos.
The instructions tell you to locate "about 4mm" in from the edge of the running plate but that should refer to the outer edge of the fixing flange : The vertical bars should be a scale 6 inches (6.75mm) inset from the edge. If you fit as per instructions, then the drop end plates will be almost flush with the buffer plank ends, instead of being noticeably inset.

Decision time!
The fixing flange on the brass etch is far wider than scale, so fitting the "right way" round will not work. The running plate in the kit is steel which is over scale (of necessity.......you only need to look at the bent corners of running plates in old photos of these locos to see why) so adding to the visible thickness is probably not wise. The only sensible method is to have the flange facing inwards but the vertical bar inset by the correct distance....  6.75mm NOT "about 4mm"!

There will be ramifications when you come to fit the steps to the running plate and possibly with other fittings (e.g. the sand boxes) but they can be dealt with when that stage has been reached.

Photos illustrating some of the cab and boiler mods are attached and fuller explanations will follow.





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Offline John Candy

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Conversion : Backdating the 8750 Class kit to early 57XX Lots.
« Reply #16 on: December 31, 2017, 04:02:31 PM »
The second of my GRS 8750 class kits (being completed in parallel with 4667) is to be built as 5786 in "as built" condition.

The most obvious difference between the early and late Lots is the cab but there are several other differences (many of which were erased by later modification to match the newer locos.).

1) As built, none of the pre-1942 locos were fitted with the external top-feed casing.
2) There were no steps fitted to the sides of the bunker.
3) The handrail on the leading edge of the cab opening was not fitted to the side sheet but to the extended end of the cab cut-out beading.
4) Cab doors and sliding shutters were not fitted.
5) The injector arrangement differs from the locos with the top-feed casing.
6) The "contractor-built" locos were fitted with riveted tanks (the Swindon-built tanks were welded).
7) The lubricators for the middle axle bearings were plainly visible ahead of the splasher.
8 ) The tank fillers (including those on the early Lots of locos of the 8750 type) were the older circular pattern, not the more modern oval type as fitted to the kit.
9) The tank saddle braces (the bits of inverted T-section which lie across the boiler and firebox on the kit) were flat section and not "T" .
10) The whistles were not fitted with shields and were operated by direct cable linkage to the whistle and not by internal steam valves.
11) The brake hangers and blocks are of an earlier pattern, quite different to the later (forged steel)  pattern as supplied with the kit.
12) Position of the lamp irons which carry the spare lamps : Original Swindon drawing (and photos of early locos in original condition) show two lamp irons by front of the leading splasher on LHS. Photos of locos built in late 1930's and after, show two lamp irons on LHS between tool box and injector. In photos taken later, some locos (with either cab type) have three lamp irons in either of the positions previously mentioned!

That covers most (if not all) the visible differences between early 57XX locos and the later 8750 types but remember that there was a transition period during which 8750 locos (those with the Collett cab)  were built with other features carried over from the earlier design and , similarly, many, but not all, of the earlier locos were gradually "updated" with all or some of the "improved" design details. All eventually received the bunker side steps and cab doors but other updates were "patchy" in their application....you need a dated photo if you want to get it absolutely right!

Reverting to the major surgery, which is the cab replacement, the plan is as follows.
1) Cut (from brass) a new cab front spectacle  plate which stops just below where the tank top corners meet the cab side (dimensioned to fit between new brass cab sides).
2) Cut a cab rear spectacle plate which stops just below the bunker side sheets.
3) Cut two new cabside sheets which are full height at front and include the strip which carries the roof (the cab back is only as thick as the separate rear spectacle plate).
4) Cut a new roof from brass.
5) Cut away the roof, upper sections of cab (front and rear) and the entire forward section of the cab sides (reprofile the top forward corners of the bunker to match profile of new cab entrance).
6) "Slim down" the remaining (lower) section of resin cab front, which will attach to the boiler/tank unit, so the new brass cab sides sit at correct overall width.

Detailing :
Roof : Transverse sliding vent (brass sheet and angle) and rain strips (brass angle).
Cabsides: Rivets ;  beading around opening from brass strip (including extension to locate leading handrail).
Cab rear : Spectacle bars, rivets, coal doors and brake handle recess.
Cab front : Spectacle surround, rivets, holes for whistle controls.
Bunker (resin retained with new profile) : Substitute half-round beading for the flat beading.

Attached photo shows the butchered resin cab and the only parts retained for incorporation into the new cab for 5786.

Livery Note: If you are building a loco with top-feed casing, it would never have been lettered "Great Western" (except preserved examples now living in a theme park world!) since the "GWR" branding (superseding the "shirtbutton" art deco totem) was in use by 1942, when the first locos were fitted. The 8750 locos built from 1942 onwards, until end of the war, were turned out in plain black livery, not green.




« Last Edit: January 07, 2018, 10:25:40 AM by John Candy »
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.