Split Chassis Woes continue

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Dad-1
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Split Chassis Woes continue

Postby Dad-1 » Wed Feb 15, 2012 9:55 pm

I've never been too worried about split chassis although it can be a pain.
Tonight I decided to add a decoder to my Bachmann 43XX all was going well
to start with, drilled a couple of holes at the front of the tender floor wrapped
the tender weight with masking tape fed the wires through the holes to mate
up with wires from the loco. I split the chassis down carefully putting all parts
on white paper. Slightly filed to open the sprung motor contact housings. Used
spare decoder wires cut off the loom soldered on the motor tags then protected
by pushing on some fine plastic tube.
The chassis wires are to be held under the rear chassis fixing - And the usual
thing happened - the plastic fixing had the square head break off !! The other is
probably just as brittle, but not been tightened yet !

Image

Now I have a stripped down loco that will have to lay around for the best part of
a week while I try to find replacement parts.
Thought I had one from an earlier job where the same thing happened, but an
hour searching all sorts of dark corners has failed to reveal my spare that should
be in a bag with a few black axle muffs ........... Thinking Was it 3 years ago ?

Geoff T
Remember ... I know nothing about railways.
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Tiddles
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Re: The Usual Split Chassis Woes

Postby Tiddles » Thu Feb 16, 2012 12:37 am

Had a web search and nothing available from Bachmann US or UK.
Personally I find Bachmann US more helpful so maybe send them an email.

Of see if anyone has a Bachmann split chassis spares or repair.
The Baltimore and Ohio Railroad, “Linking 13 Great States With The Nation.”

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Bufferstop
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Re: The Usual Split Chassis Woes

Postby Bufferstop » Thu Feb 16, 2012 11:15 am

Hi Geoff
It might be better to look for an alternative way of clamping it, as any spares are likely to be of a similar age and condition. Is there any possibility of passing through a threaded rod in a thin sleeve, with plastic washers on the ends.
John W
aka Bufferstop.
Growing old, can't avoid it. Growing up, forget it!
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beeman
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Re: The Usual Split Chassis Woes

Postby beeman » Thu Feb 16, 2012 11:57 am

I have had this happen, and replaced with nylon nut/bolt. these usually come in cheesehead and available from a good model shop.Make sure the distance washer is fitted between the chassis plates. Small spring washer can be fitted under the nut if desired. Or if engineer capable a larger size nylon screw and tap [cut a thread] in one side plate. Try to keep a good/close fit as the two chassis halves use these fixings as location pegs. Good tip when working on these is to put two drill bits plane shank end into/across axle slots to align parallel, minus spacers, before clamping together. Beeman
You wo'nt find you 'CAN' unless you 'TRY'.

Dad-1
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Re : Split Chassis extended difficulties.

Postby Dad-1 » Sun Feb 19, 2012 8:27 pm

I have it running now
A very kind NRM member sent me a few replacement fixings.
Through this I have now found that Bachmann did 2 different sizes
and fully understanding Murphy's Law they were the larger size !!!

The one remaining fixing would appear to hold together tight enough
even squeezing between finger and thumb shows no sign of movement.
However the journey with this loco still has far to go as some rather unusual
problems have arisen.

Decoder in, wired up, loco given an address which the decoder has taken.
BUT it will only run well in reverse, in that direction it has a good range of speeds
and responds exactly as it should.
Forwards it will creep at the lowest of speeds, but increasing power seems to just
give an increase in noise, but no change in forward momentum. Add weight by
hand and actually move forward the motor turns faster, but using that outside
force at faster or slower than the power setting the motor stalls. Simply it just
dosen't seem to have any real power in that one direction.
I don't believe there are any wiring or decoder problems, or even controller (I've tried 2)
I reversed the running direction in the decoder, but this made no difference, still fine
in reverse, but no good forwards.
Turning the helical gear/flywheel by hand there was no apparent change of loading. My
thinking is drifting towards a motor fault, yet if the magnets had become very weak one
would expect problems in either direction.
Because I'm DCC only this was only given the shortest of tests on the DC running option,
So I can't say that it was running well before adding the decoder.

I'm open to any suggestions ....... although may try to get another can motor, but these
are usually very reliable ....... and it works fine in one direction !!!!!!!!

Geoff T.
Remember ... I know nothing about railways.
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beeman
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Re: The Usual Split Chassis Woes

Postby beeman » Sun Feb 19, 2012 8:48 pm

Have you removed the motor from the chassis, can you try a DC controller direct to the motor,or 9-12v battery, obviously without the decoder. You appear to have attempted to isolate it in stages. So my suggestion is about as far as you could go, 'load' the motor if it will run, with a finger on the shaft/gear to see what happens. the next step is to strip the motor if you are competent, although most of the can type are throw away when troublesome. Strange its fine one way only, commutation/brushes is normally the same so similar o/p either direction, and design preventing magnet shift. Think new motor from Bachman around £14.00. Could be a winding fault affected by direction. If I had to replace I would dismantle out of interest as to why. keep us informed please. Beeman.
just an afterthought, are the motor bearings badly worn ?. do you get any rapid heat increase when in slow direction.have you a meter which you could check the current to the motor when using DC/battery, Obviously should be same when testing motor on its own.
Last edited by beeman on Sun Feb 19, 2012 8:52 pm, edited 1 time in total.
You wo'nt find you 'CAN' unless you 'TRY'.

Ark Royal
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Re: The Usual Split Chassis Woes

Postby Ark Royal » Sun Feb 19, 2012 8:51 pm

EDIT

I have removed this post because it's correctness has been called into question

Sorry

Chris
Last edited by Ark Royal on Wed Feb 22, 2012 5:28 pm, edited 1 time in total.
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Chris
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beeman
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Re: The Usual Split Chassis Woes

Postby beeman » Sun Feb 19, 2012 8:57 pm

Capacitors are NON electrolytic if fitted for suppression, electrolytics must only be connected correct way round. otherwise they can explode, lovely bang when they do. The polarity supplied to a motor has to change to effect a rotation change. Sorry to negate your suggestion Ark Royal. Beeman
You wo'nt find you 'CAN' unless you 'TRY'.

Dad-1
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Re: The Usual Split Chassis Woes

Postby Dad-1 » Sun Feb 19, 2012 9:23 pm

There is nothing in the circuit except wires and a decoder.
Reversing direction of travel in the decoder should have used the decoders circuits for backwards and forwards
it's also taking other changes like address, aceleration and deceleration. The basic wiring must also be acceptable,
or again decoder changes wouldn't be working correctly.
Running in reverse against my finger it develops wheel slip through a full range of power settings
Running forwards against my finger nothing but a light hum, given help it will take more power and
as helped faster will turn O.K. - remove the push and it just stalls - and the power is closed down by me so as to
not burn out the decoder.
I can't understand as normally windings are either O.K or burnt out, magnets too weak should kill all movement.
I've packed it in for tonight as the decoder in the tender is hard wired through to the loco on 'tight' length wires.
Tomorrow I'll probably unsolder and re-connect for DC running then try on the clubs DC layout on Tuesday.
Logic points to the motor, but sometimes a bad soldered joint can cause unexpected odd behaviour.
I even wondered if pickup through the chasis/axles could be bad due to a build-up of grease following the rebuild,
but running for a while in reverse resulted in no change.

Geoff T.
Remember ... I know nothing about railways.
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Roger (RJ)
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Re: Split Chassis Woes continue

Postby Roger (RJ) » Sun Feb 19, 2012 9:41 pm

Try reversing the orange and grey decoder wires to the motor. If the poor running is now only in reverse, instead of forwards, it would suggest a decoder fault.

jcm@gwr
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Re: The Usual Split Chassis Woes

Postby jcm@gwr » Sun Feb 19, 2012 10:57 pm

My thoughts on this are as follows,

Firstly, as I have recently had one of these apart, I noticed that there is a little bit
of play in the motor mounts, ie you can slightly bias the motor one way or the other
when you tighten up the 4 screws that hold it.
This could mean a small variation on how tight it is against the gear train, add to
this as the motor changes direction it could be tighter/looser against those gears.

Secondly, are the intermediate gears free to rotate in both directions, the one that
I had apart had a bit a corrosion and eventually the pivot for the gears snapped off!
A careful bit of drilling and some 1.8mm brass sorted it. But while in the process of
snapping the difference between forward and reverse was noticeable [probably the
angle and therefore the pressure on the gears causing more {or less} binding].

Hopefully these thoughts might be helpful in sourcing your problem.

Good luck, Jeff

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Bufferstop
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Re: Split Chassis Woes continue

Postby Bufferstop » Sun Feb 19, 2012 11:43 pm

Geoff my strategy on a fault like this would be to swap round the decoder to motor wires. If the poor running is then in the opposite direction look to the decoder/wiring. If it's still in the same direction it's a problem with the motor.

Have you run it with the motor removed from the chassis. If there's no noticeable difference with the motor running free it could be mechanical. I've noticed that with many motors the armature shaft is free to move backwards and forwards, if there's too much resistance to turning, one way will press the shaft against the rear bearing, and have little effect, the other way will try to pull it out of the front and foul on the brush gear.

It's possible that you are seeing the effect of a motor which is drawing more current than it should, coupled to a decoder which can deliver more current one way than the other. Modern controllers DC or DCC are not good at warning you of higher than expected currents. They just do odd things then do nothing. My old H&M with an electro-magnetic cut out almost talked to you. A meter, on the 10A range, in the track feed might help.
John W
aka Bufferstop
Growing old, can't avoid it. Growing up, forget it!
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Bigmet
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Re: Split Chassis Woes continue

Postby Bigmet » Mon Feb 20, 2012 9:57 am

To add to the witches brew on running assymetry. The possible decoder cause needs to be checked out as already suggested.

But the most likely cause in my experience is a thrust bearing problem on the motor. Seen it many times on various motor designs but don't know enough about the motor used on this particular chassis to know what the vulnerability is. The end thrust from the worm action reverses with motor direction so only one of two bearings takes the load. If just one is worn in some way, there's the problem.

The possibility of the pinion assuming a high friction position in one direction - again as already suggested - would be next suspect.

Gonna have to strip the chassis down again Geoff. Got to say that these and many other problems are the reasons I stopped buying the Bach split chassis mech locos as the problems became very evident when I began operating them quite intensively. Good pick up concept, but poor constructional execution. After you sweat blood to get them right, they then need frequent servicing to clean the conducting bearing surfaces, and a stream of repairs to multiple components, and then they completely wear out. Over the same period a conventional wiper pick up chassis (having been carefully adjusted and tested on receipt) only requires regular lubrication of the crankpins and occasional drive line and axle lubrication checks; and my guess is that they will achieve ten times the service life, with fewer troubles on the way to boot.

Dad-1
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Re: Split Chassis Woes continue

Postby Dad-1 » Mon Feb 20, 2012 11:57 am

My initial work now points to a decoder problem.
I've been out this morning so only had a few minutes during which I unsoldered all the leads
then just joining chassis to motor wires, runs fine on '00' DC running (although I hate doing this)
So although I will solder the decoder back in trying the alternative wire test which I now fear will
give me forward motion without any reverse !!
Now although it was a new decoder, having cut the plug off and removed all but the 4 essential
motor connections there's no way I can 'return' as faulty !!
This has brought about the decision to incorporate a socket in the tender so a replacement decoder
will just be plugged in.
Again Murphy's Law ...... the only new decoder failure I've had happens to be the 42nd and a hard wired
one at that !! (Yes I did have one where I damaged the forward motion circuits by running a high
load motor at stall speeds and it melted the plasticard backing it was sitting on !!)

I refuse to be beaten, although Bigmet's correct, better to have the newer stock and had the 43XX
been in the current range I may well have one. This GWR version is just a little special in as much it
belonged to one of our club members who passed away last year.

Geoff T.
Remember ... I know nothing about railways.
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Dad-1
Posts: 6421
Joined: Sun Aug 24, 2008 8:05 pm
Location: Dorset - A mile from West Bay.

Re: Split Chassis Woes continue

Postby Dad-1 » Mon Feb 20, 2012 12:51 pm

I'm now comfortable that it's the decoder.
Put back into the loop I have forward motion and no reverse.
Worse than that where I had been able to change and set the basic direction of travel via the controller today It didn't
want to know, it did still accepted a change of address.

Now why ?? I've usually handled all my decoders through a nice clean fresh hanky (Don't tell the wife) to remove the slim chance
of body startic causing damage. I know I tend to build up static and will often cause problems with radio reception when I get
near the aerial of the kitchen radio. Makes me wonder if I could have damaged it handling directly as I trimmed off function wires.

I did wire with the shortest possible extensions so have now decided to add a socket and leave adding a decoder to the last. This
will allow me to draw excess wire into the tender without struggling to solder in a tight gap between loco & tender.

I do like a challenge ..

Geoff T.
Remember ... I know nothing about railways.
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