Bachmann A2 Cab Sloop Fix
Entry posted by G-BOAF
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Bachmann A2 – correcting the downward slope of the rear running plate/cab
With my analysis winging its way to Bachmann, I am posting it here!
****NOTE – this advice is offered in good faith – I will not promise that it will work in all cases and modelling skills, and take no responsibility for loss or damage (to person, limb, model or model value!) that may result. Some measurements (including thickness of plasticard, and amount of material removed) may require amendment for your particular model, and trial and error may be involved.****
*** NOTE 2 – read ALL these instructions through before starting, DO NOT START work unless you are happy you can complete it, including some awkward reassembly. ***
NOTE 3 – some of the screws joining parts of the body can be VERY tight. Be careful not to strip the screw heads (I nearly did!)
Good Luck!
G-BOAF
What you will need:
Screwdrivers, knife, small metal file, 0.25mm plasticard (or similar for packing) screwdriver (Philips No.0 seems to work well for backhead screws, and a number 1 (I think, for other screws)
Step 1.
Take off body. Drawbar will drop out. Then, undo all 6 boiler/cab screws (two under backhead, two under firebox, one under boiler barrel (the rearward one of the two in this location), and the one under the smokebox. Keep note of what goes where, they are all different sizes!
Step 2.
Remove backhead by gently pushing it backwards from inside the firebox. Fall plate will drop out.
Step 3.
Gently remove boiler from running plate. It may require ‘rocking’ gently side to side off the running plate. Smokebox steam pipes may well drop off at this point. Keep them safe.
Step 4.
Gently break off cab from boiler, Cab will be glued to boiler. Holding the cab roof with finger and thumb inside and outside. towards the front, gently lever thee cab upwards to break it off.
Step 5.
Scrape off all the remaining glue on cab front, and on the rear of the firebox/lip. The area will be hidden on reassembly, but take your time, do not rush or risk damage to paint in and around this area (esp at the top of the cab front)..
Step 6.
On the running plate casting, file off about 0.5mm of material from the V-front of the raised section of casting to which cab/backhead are secured. The outer-bottom part of this area may be difficult to do without damaging the running plate/rivet detail, but go as far as you can.... And then work on the inside bottom of the Cab V-front to scrape off a corresponding amount of material to compensate for any metal that could not be removed. Also extend forward the depth of the ‘slots’ in the cab moulding which the backhead screws pass through – if left they will restrict movement. The aim is that when the cab it put back, it has about 0.5mm fore/aft play to absorb any irrigularities without bending the running plate. You
Step 7
Backhead – file down the tops of the gauges/valve mounts that sit atop the backhead. The valve handles themselves should be left, but be careful not to damage them, and beware, they can fall out without warning, so watch out! When you hold the backhead, be careful of the injector valve handles – do not put pressure on them!
Step 8
File down a fair amount (at least 0.5mm, but I didn’t actually measure it – could be a bit more) of material off the FRONT EDGE (i.e. the edge that contacts the front of the cab) This ensures that the backhead won’t push outwards when everything is screwed up again! Depending on how ‘thick’ the cab front is, will depend on how much material to remove. Ensure that the front of the backhead NO LONGER makes contact with the front of the cab.
Step 8a
file the front corners of the backhead casting, again to prevent any contact with cab corners.
Step 9
Replace boiler ONLY and loosely do up screws such that the boiler is still loose on the running plate.
Step 9A
Getting the outside steam pipes to relocate in the smokebox/running plate is DIFFICULT, not least because they are partly behind the smoke deflectors! I found that, with the boiler loosely in position, but not rammed home, holding the steam pipes with blu-tak, locating them in the holes in the running plate, line the tip pip up with the hole in the smokebox, then push the boiler/smokebox home. Time and persistence required – it took me 15 mins at least (once I knew what I was doing! You might want to wait until you are satisfied the job is correct, then re-strip everything (or at least loosen everything up) and re-insert the steam pipes.
Alternatively, glue them to the smokebox, but possibly do this BEFORE you do any dismantling, since getting their position correct without them being secured at both ends may be difficult. I haven’t tried this, so can’t advise.
Step 10.
Before doing up firebox screws fully, squeeze the running plate section under the firebox against the firebox botttom, to minimise this gap, don’t go mad, and make sure you are pushing the running plate by the material under the rear of the firebox, NOT the plate under the cab, since this may bend other areas of the casting. Once done, tighten boiler screws.
Step 11.
Cut two small 0.25 mm plasticard ‘washers’, and place over rear chassis/body screw holes. There should already be 0.5mm of clear plastic packing glued on the lugs on the running plate casting.
Step 12.
Place body (still minus the cab and backhead) onto chassis, complete with the additional rear washers. If the rear running plate is not straight, ‘Squeeze’ the firebox and chassis together pushing down on the firebox top, effectively gently bending the rear running plate upwards slightly. You may want to put some 0.5mm plasticard packing between the cartazzi (towards its front) and running plate to prevent going too far the other way! Be gentle. Metal is slightly springing. Repeat with varying pressure until sloop goes. Check with ruler on flat surface that running plate is now level. Also check that the main running plate is level, excluding any irregularities it may have (either use a ruler, or callipers if you desire +/- 0/01mm accuracy!!!
Step 13
With loco on surface, the height of cab running plate should be identical to the top of the front buffer beam running plate. This SHOULD roughly match the height of the tender running plate
Step 13a Ensure the tender body is level– there may be some moulding pin protrusions under the rear of the tender body which may push that up! – thanks to 34theletterbetweenB&D for that on the A1 thread!.
Step 14
There will now be a slight gap between the Cartazzi and the cab running plate. This should only be noticable from very low angels, and can be filled with plasticard or other appropriate material at a later date if desired.
Step 15
Replace cab, and before fitting the backhead, check that it has a little bit of fore/aft play when it sites squarely on the running plate, if it doesn’t, repeat steps 5 and 6 until this is achieved.
Step 16
Replace backhead – it should slip into cab without too much force – if noticeable resistance is encountered, repeat step 7.
Step 17.
Screw up backhead – gently tighten screws, but don’t go mad. If gap between running plate and firebox reappears, repeat Steps 8 and 8a and bend back the running plate (steps 10 and 12). If OK, loosen backhead screws, slot in fall plate and re-tighten (also put in steam pipes if you didn’t do this earlier)
Step 18.
Replace body on chassis, slot in draw bar, and do up three body screws, starting with the front one. The left hand rear screw (on the right when loco upside down).might be advised to only be finger tight. I say this since it appears the cartazzi section of the chassis casting is slightly lower on the left hand side than the right (very strange, but the ruler says so, and running plate corner got pulled down when tightened fully!). More packing might do this, but I haven’t been able to work out how much – any helpers???.
Step 19.
Check everything is level to your satisfaction.
There is probably a bit of trial and error involved in the whole thing, I have repeated Step 7 a few times (there was a slight irregularity in my filing the first and second times, resulting in a slight sloop remaining)! There will be a slight gap between the V-front of the cab, and the firebox, this is due to the excess thickness at the top of the cab!.
All in all, a couple of hours work (once you know what you are doing – it took me at least double that!), with a further hour tweaking (depending on how many decimal places of a millimeter you are worried about!).
I also cleaned out some flash on chassis block under cylinder moulding and the motion bracket, as well as on the chassis block between the cylinder and gear train. The body was leaning slightly due to this flash.
Note – pics below taken at interim phase, before work on cab and backhead, but show level running plate (I think I was experimenting with 0.5mm spacers at this point – too high!)
I have never had an RTR loco where so much work has been required on a loco straight out of the box to get it to what I would imagine were the original design specifications (i.e. level and straight – I can’t imagine sloop on the CAD drawing!). Much more work than the 8750 pannier (step-by-step to come on straightening out the running plate on ALL (or nearly all?) examples (8750 only not 57XX)!
Following photo taken at interim stage, with 0.5mm packing (rather than 0.25mm), and no backhead. The finished result is correctly alligned with the tender.
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