Bachmann Class 108 - Lost Drive

[HLT 0109]

My six-year old class 108 DMU has lost drive from the motor to the power bogie following a derailment at a point set against it.  The train is sound fitted (Loksound v4 with SWD sound) and all soounds work but the train does not move.  If the sound is switched off, the motor can be heard responding to the throttle.

 

I removed the body hoping to see what the problem was but stopped short when all I could see was the motor cover and I have no instructions for dismantling.  the decoder seems to be taped to the side of the motor cover and the speaker slotted in at the end of the cover - between the cover and the loco body.  Does anyone know what will have happened and how I could fix it? 

 

Thanks,

Harold.

 

 

[Phil Bullock]

Evening Harold

 

Bachmann usually have service sheets which would give a clue. The usual cause of the symptoms you describe on Bachmann models is that the cardan shaft between the motor and axles has become displaced - but without the service sheet I don't know whether the 108 has that drive system or not....

 

If it does its easily fixed once you get in there

 

Phil

[HLT 0109]

Thanks Phil,

 

I did print off the service sheet - just after a made the post!   I attach a copy - but I see it is a Graham Farish document and therefore probably correct for a 2mm version and perhaps not for a 4mm.  There does not appear to be a Branchline version.  Although i can identify from it, the shaft you refer to (Part no 4), I don't find the document clear as to how to access it.  It looks as if I have to remove the PCB (part no 3) but on mine everything is enclosed in a black box - possibly the unnumbered box drawn to the right of the PCB - and I would be concerned about which screws to remove (the drawing does not show them).  The presence of the sound decoder and speaker wires will no doubt complicate things.

 

I would like to think I could do this myself but perhaps leaving it to the professional would be best.

 

Harold. 

GF_cl_108_v2.pdf

Edited May 27, 2018 by HLT 0109

[Phil Bullock]

Thanks Harold

 

That confirms the cardan is there but as you say its a 2mm diagram!

 

I don't have a 108 - wrong for Abbotswood - so cant get in there to see whats what but dismantling and re-assembly of Bachmann models is not beyond the capability of anyone with a selection of small screwdrivers

 

If you wanted to post a photo of the area in question am sure we could advise...

 

Phil

[HLT 0109]

Thanks Phil - let's see how I get on.

 

Harold.

[HLT 0109]

Phil,

 

Having removed the body, I am faced with the business end shown in the attached photos - one rather shaky image.

 

Harold.

Edited May 27, 2018 by HLT 0109

[John Tomlinson]

If you remove the four screws at the bottom of the semicircular vertical channels on the side of the casing, IIRC that should release the casing and allow you to see inside.

 

The motor is at the inner end of the casing, so that closest to the centre of the coach, and the drive shaft comes out of the motor into the housing at the top of the bogie.

 

You may find it overflowing with grease when you open it up, I'd recommend you remove what you can with a cocktail stick, there'll still be plenty left, it's just Bachmann's deeply annoying practise of over-lubricating everything!

 

John.

[Darius43]

You don’t need to remove the motor housing metal box.

 

Is the motor running ok but the wheels don’t go round?

 

If so it’s most likely a carden shaft (dogbone) issue - the Bachmann 108 uses this form of transmission. Atop the motor housing is a Philips head screw located above the centre of the bogie. If you undo this screw the bogie will drop free, hopefully with the carden shaft attached. If it isn’t attached check to see if it is attached to the motor - it’s a push fit to both.

 

Check that the shaft is properly attached to the bogie gearbox and then re insert the bogie with the shaft sticking out, aligning the free end of the shaft so that the tabs click into the slots in the motor flywheel. You can then carefully locate the pivot screw attachment point atop the bogie into the hole in the metal box that the bogie fits into and re-attach using the screw.

 

Cheers

 

Darius

Edited May 27, 2018 by Darius43

[John Tomlinson]

You don’t need to remove the motor housing metal box.

 

Is the motor running ok but the wheels don’t go round?

 

If so it’s most likely a carden shaft (dogbone) issue - the Bachmann 108 uses this form of transmission. Atop the motor housing is a Philips head screw located above the centre of the bogie. If you undo this screw the bogie will drop free, hopefully with the carden shaft attached. If it isn’t attached check to see if it is attached to the motor - it’s a push fit to both.

 

Check that the shaft is properly attached to the bogie gearbox and then re insert the bogie with the shaft sticking out, aligning the free end of the shaft so that the tabs click into the slots in the motor flywheel. You can then carefully locate the pivot screw attachment point atop the bogie into the hole in the metal box that the bogie fits into and re-attach using the screw.

 

Cheers

 

Darius

 

This is absolutely right, and the screw holding the bogie can be seen just on the edge of the black tape in your picture. If you then want a look inside follow #7.

 

John.

[34theletterbetweenB&D]

It should be immediately apparent if the drive shaft has disengaged, in which case as already described. Much less likely cause, the plastic drive cup which is a push fit  insert into the flywheel may have come loose. Secure with a spot of superglue.

 

And if you want a diagram for the power unit element, then any of the MU's sharing this drive will do, it is a design common to many of the BR pilot scheme and near contemporary classes. So Derby lightweight and classes 101, 105, 108, 205, 411, 416. Does the downgraded new Bachmann site provide access to the diagrams as the previous site did? (Must admit to having lost all patience with it and now cannot be bothered to even go there! Can you imagine a shopkeeper smashing up or leaving perfectly satisfactory premises and expecting customers to negotiate an unsignposted swamp to look at the stock?)

[HLT 0109]

Many thanks Gentlemen.

 

A bit late to try now - a job for the morning I think.

 

34C - I will have a look on the Bachmann site for the other MUs you mention - the only one for the 108 appear to be the 2mm version attached to my post #3

 

Harold.

[Phil Bullock]

Thanks to those who have a model to hand for engaging - will leave you to provide any more help Harold might need

 

Phil

[HLT 0109]

'Morning All.

 

Job done (subject to testing)!  I had a look on the Bachmann website and found a link to both Branchline and GF service sheets - but both produced the sheet for GF version.  It is possible they are identical in design but it would have been good to see a statement to that effect.

 

I had a bit of a moment - having removed the bogie, there was no cardan shaft!  Fortunately, I had seen a little earlier on my desk, what looked like a bit of spru from a Kadee coupler pack, that I had decided not to throw away . . .

 

It looks to me that, in reassembly, the trick is to tighten the fixing screw for the bogie sufficiently to restrict the fore-and-aft pivot of the bogie, whilst not stiffening its lateral turn,  I am thinking that, in coming to an abrupt stop, the bogie pivoted backwards, taking the housing for the drive shaft forwards sufficiently to release the shaft.  If I have got it right, perhaps the problem will not recurr.  Testing to be done with body removed.

 

Thanks to everyone.

Harold.

[John Tomlinson]

'Morning All.

 

Job done (subject to testing)!  I had a look on the Bachmann website and found a link to both Branchline and GF service sheets - but both produced the sheet for GF version.  It is possible they are identical in design but it would have been good to see a statement to that effect.

 

I had a bit of a moment - having removed the bogie, there was no cardan shaft!  Fortunately, I had seen a little earlier on my desk, what looked like a bit of spru from a Kadee coupler pack, that I had decided not to throw away . . .

 

It looks to me that, in reassembly, the trick is to tighten the fixing screw for the bogie sufficiently to restrict the fore-and-aft pivot of the bogie, whilst not stiffening its lateral turn,  I am thinking that, in coming to an abrupt stop, the bogie pivoted backwards, taking the housing for the drive shaft forwards sufficiently to release the shaft.  If I have got it right, perhaps the problem will not recurr.  Testing to be done with body removed.

 

Thanks to everyone.

Harold.

 

That sounds about right Harold, the bogie needs to be able to turn for curves obviously, and then be able to move but only a little, forward and back, and from side to side.

 

Sounds like you also invoked my rule one of modelling (well of life actually), never, ever throw anything away!

 

John.

[HLT 0109]

That's pretty much it John.

 

However, I had to redo the job.  Whilst testing and experimenting with how tight to make the bogie fixing screw (with the body off), there was a buzzing/resonance which seemed to be affected by the tightness but could have been the (now loose) speaker vibrating.  There was also a droning sound.  Having put the body back on, the buzzing/resonance disappeared but the droning intensified to the extent that the sound chip couldn't be heard.  I had noticed that the drive shaft has different ends, one a square cross-piece and the other round - so which way to position it?  As the square end clicked into the bogie tower I assumed that was correct and it helped hold the shaft in place while the round end was positioned into the motor shaft.  Since that was the only unknown in the job, I reversed the position and, to my relief, the droning has disappeared.  Problem now is, the internal lights in the driving unit seem not to be working but the directional lights are.  As it happens, the bogie fixing screw is almost up tight without any problem negotiateing set-track crossovers and undulations.

 

For anyone else with loss of drive in this model please note the correct orientation of the drive shaft.

 

Harold.

[SRman]

The internal lights are powered by vertical metal bars (copper or brass?) through the seating units, contacting the PCB in the roof. The vertical contacts are very easy to bend or dislodge (or both!), thus misaligning the contacts with the PCB. They also contact the bottom PCB attached to the chassis under the seats, and if dislodged slightly can miss there as well. That would be my starting point in investigating the lack of interior lights, for what it's worth. 

[John Tomlinson]

I'm glad you've fixed the drive problem.

 

Jeff (SRman) is right about the contacts being somewhat vulnerable to bending. Another problem, as I discovered with an ebay purchase a few weeks back, is that tarnish on the contacts can scupper current flow if they've been disturbed. A quick rub with fine emery or similar, a fibreglass stick did the trick for me.

 

John.

[HLT 0109]

Thank you John and Jeff.

 

I did have difficulty getting the body to click back into place so I suspect the vertical bars are misaligned.  I will investigate.

 

Harold.

[HLT 0109]

At last - all back to normal.

 

The two vertical bars had a lean towards the back and I was able with tweezers to encourage them forward without completely removing the body, thus simplifying putting it back.  I must say, I am rather glad i bought the set of tweezers that was the subject of a bargain buy recommendation some months ago!  They also helpded with reattaching the battery box that I knocked off too!

 

Thanks to all,

Harold.

[34theletterbetweenB&D]

...For anyone else with loss of drive in this model please note the correct orientation of the drive shaft...

 The drive shaft design with the couplers on the ends being different is generic throughout the range of these MUs and the centre motor twin bogie drives, and is discernably drawn on at least some of the diagrams as squared off end into the flywheel coupler. However, some models have as purchased been found with one or both shafts the other way around, in my experience of taking the mechanisms apart to look inside and make improvements such as ride height reduction on twin bogie diesel types.

[Phil Bullock]

Glad you got sorted Harold

 

Phil