Bachmann mountain - longish post


Aidrian Bridgeman-Sutton <a.bs@...>
 

| Date: Mon, 27 Sep 1999 08:49:43 -0700
| From: Thomas Beutel <Thomas.Beutel@efi.com>
|Subject: RE: Bachmann mountain
|
|Nelson and Jack,
|
|Another thought to add is that in some cases, you only have one shot
at
|getting a particular loco if it is a limited production run (Proto
2000
|E-6's come to mind - the City of San Francisco models were sold out
in a few
|days). Of course, this certainly was not the case for the Bachmann
model.
|
|As a post script, I did fix the intermittent stall problem without
opening
|up the engine. It turns out that I had not pushed the connector from
the
|tender in all the way... The growling does not make me comfortable,
but it
|is not any worse that any number of brass steam locos that I have.
For me
|the 4-8-2's performance is very good, and I would rank it excellent
if it
|were not for the growling in the reverse direction.
|
|Thomas Beutel
|San Francisco


If anyone caught the comments on the driver size problem with this
model on R.M.S, well it is eminently fixable. I used Alan Gibsons
wheels to rebuild the chassis, though I think Sharman may have wheels
that are an even better match.

Hope this is of interest, the model is now finished in the pre 1934
Southern livery with gold striping and lettering. There are a good few
kitbash possibilities for this model as well, including Southern Ts,
Seabord Ms and possibly CofGa mountains.


|PARTS
|
|I sourced these from Alan Gibson, I haven't found a US distributor
for
|them yet, but at about $US25 +shipping they are easy enough to order
|direct.
|
|Alan Gibson (Workshop) Ltd
|The Bungalow
|Church Rd
|Lingwood
|Norwich
|Norfolk NR13 4TR
|England
|
|Ph/Fax +44 1603 715 862 � between 8am and 6pm UK time only, since it�
s
|his private line as well.
|
|He has a really excellent mail order service � UK delivery is usually
|next day.
|
|Wheels and Crankpins
|
|The wheels are sold as 5�0� types for OO scale, but work out at 68.5�
|in HO. They have a steel rim, so you�ll want to keep them oiled or
|apply gun blue to blacken them. The centres are plastic, which won�t
|be a problem since pick up on the Bachmann chassis is by means of
|wipers bearing on the back. Axles are supplied in two lengths. For HO
|use the shorter axles � the longer ones are for EM gauge. Make sure
|you order the OO/EM wheels otherwise you�ll get P4 wheels, which may
|not run so well on standard HO track, but look real nice. he has a
|range of proto87 components as well.
|
|There are two choices from his range, neither of which is perfect but
|neither is noticeably wrong unless you are a serious rivet counter.
|You�ll need four sets of wheels and one set of crankpins.
|
|Part number G4860E
|
|This is a 16 spoke wheel instead of the 15 spokes which the USRA
|engines had. I used this since the bevelled rim on the 15 spoke
design
|would have been very noticeable with green wheels.
|
|Part number G4860
|
|A 15 spoke design with a bevelled rim. The rim could be filed back if
|you were very keen, but that�s up to you. It probably will not show
|under a coat of weathered black paint anyway.
|
|(Greenway offer 69� drivers in the US. I have not used these, so I
can
|�t comment on their suitability, but they would need to be fitted in
a
|similar way to the Gibson wheels. I understand that they come ready
|quartered and on 3mm axles - they have a website ---
|http://www.greenwayproducts.com/).
|
|Part number G4M42
|
|Crankpin set. Again these are steel, and will need careful handling,
|as some of the parts are very fine. There are spares in the pa
|
|1/8� internal diameter washers will also be required from your local
|supplier.
|
|1/16� and 3/32� o/d brass tube � K&S or similar.
|
|HOW TO DO IT
|
|Stage one involves stripping the engine down to shell and chassis �
|the Bachmann exploded drawing should help here. Undo the screws
|securing the side rods and main rods and the keeper plate that
secures
|the drivers in the frame. They should now drop free.
|
|Strip the chassis as far as it will go to leave the bare die-cast
|frame and the circuit board attached to it.
|
|Wheels and Axles
|
|The Gibson wheels might result in the flanges fouling each other,
|since they are slightly large over the flanges. I found the quickest
|way to deal with this was to mount a wheel in a Dremel tool and touch
|the flange against a sheet of wet and dry - don't get heavy handed or
|the tyre will separate from the centre if you generate too much
|heat.The interference is only in the order of a few thou at most so
it
|won't take long.
|
|There are no balance weights so they are best cut from styrene and
|attached with epoxy, and the space behind them filled with suitable
|filler. The drawings in the Kalmbach Cyclopedia will show what you
|need, watch out for the different size weights on the main drivers.
|
|The worm gear needs to be removed from the Bachmann axles � the
wheels
|twist and pull off and the axle can then be tapped out of the gear
|with a hammer and punch. The centre hole will need to be opened up
|with a reamer to accept the Gibson axles. I used a taper reamer and
|worked from both sides, and was careful to leave the hole a fraction
|under size to provide a secure fit. The gear was secured to one axle
|with a little LocTite, and the wheels were fitted with their
crankpins
|and lightly pressed on � they�ll need to be moved later. Make sure
|that you provide washers behind the leading and driven wheels before
|you press the wheels. This is to take up any sideplay between the
|wheels and the frame � it�s best to do this after you have completed
|the next stage so that the spacers, wheels and frame all match.
|
|Frame.
|
|The Bachmann wheels have 3/32� dia. axles as opposed to the 1/8�
axles
|that Gibson supplies, so the axle slots in the frame need to be
opened
|up. It�s probably easier to get the ultimate level of precision if
you
|have access to a milling machine, but I was able to open them up with
|a round needle file. If this concerns you and you have access to a
|lathe it would be possible to bush the Gibson wheels and retain the
|3/32 axles.
|
|It takes a bit of care to make sure that you remove the same amount
of
|material from the front and rear faces so that the centres remain in
|the same place. You�ll need to check the mesh of the worm and gear
and
|slowly and carefully deepen the axle slot for the driven axle with a
|file in order to get the meshing right. The depths of the other slots
|are less critical, but it needs a little care to get all the wheels
|touching without the frame leaning left or right or perhaps trimming
|up or down by the stern. Placing the model on a sheet of plate glass
|really helps to get this right.
|
|The moulded brake gear needs a little trimming with a file to get
|clearance on the new wheels.
|
|Side Rods and Main Rods.
|
|The Gibson crankpins are smaller than those that Bachmann uses, so
the
|side rods and main rods need bushing with a little brass tube. This
is
|best done using 3/32� tube and the bushes soldered into the rods.
|This kills the blackening unfortunately, but it�s easy enough to
redo,
|or paint them as I did. If you are doing an L&N engine, then this
will
|need I section side rods, and these are available from Gibson as
|�Universal Coupling Rods� , part number G4M92 - you�ll need two sets
|and they�ll need cutting to length.
|
|Quartering.
|
|This alarms some, but it�s pretty easy assuming the axle centres and
|side rods are still at the same spacing.
|
|Set up the axle with the worm gear by eye by twisting the drivers, it
|doesn�t matter whether its 90 degrees or somewhere between 87 or 93 ,
|since you can�t see both sides of the engine at the same time. Take
|the rear drivers, line them up by eye, fit them to the frame, and fit
|the side rods to just these wheels. It is pretty easy to gently tweak
|the wheels backwards and forwards until there is no binding. The
|engine will then run nicely as an 0-4-0. Once it runs as a 0-4-0, fit
|another set of divers and add the side rods to these. Since the
engine
|ran as an 0-4-0, any binding will be in the set that you last fitted.
|When it runs as an 0-6-0, add the last set and repeat the exercise.
|That�s it. If you do get any fractional misalignment it is possible
to
|tweak the holes in the side rods slightly oval to take up a bit of
the
|slack, but it should only be used as a last resort.
|
|Test run the set up extensively before fitting the valve gear. I
find
|it best to add adrop of nail polish to the crankpin nuts to stop them
|unwinding while I�m running it.
|
|When you are happy fully press the wheels home and check the back to
|back.
|
|Valve gear.
|
|Not much to worry about here unless you want to update it to
|Walschaert�s as many lines did. I didn�t, but yet again Gibson has
|some useful components which may prove adaptable.
|
|The real hassle is refitting the eccentric on the new crankpins. I
|made up a new keyed bush for the eccentric from 1/16� and 3/32� brass
|tube, which was tapped 1.0mm/14BA to fit the crankpin.
|
|And that�s about it � any questions let me know.
|
|Aidrian