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Blog- Sixties Snapshots - 00 scale - Lowering the ride height of the Bachmann Deltic


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My last Post https://www.rmweb.co.uk/community/index.php?/blog/880/entry-21774-a-deltic-dalliance/ reviewed past ready-to-run Deltic models. The message was that the prototype was large, lengthy (and noisy) and that a scale model was not compatible with train set curves. In an attempt to solve the issue Bachmann appeared to have adopted a ‘Belt and Braces’ approach. The Bachmann model has a narrower profile for the leading bogie wheels while at the same time thinning the bodywork with ‘cutouts’ in the vicinity of the front and rear bogie wheels. Then in addition, Bachmann controversially raised the running height of the model by almost 2mm (6inches). The perceived wisdom on the ‘web’ is that it is relatively easy to lower the Bachmann model to give the correct ride height. I would take up the challenge.

 

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Bachmann D9004 Queen's Own Highlander, lowered and coupled to a Bachmann Mk1

 

As with a lot of things in life there is generally more than one route to the desired goal.

 

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MkII Bogie Tower 'as bought'

 

Probably the shortest route to follow involves cutting away the plastic wings on the top of the bogie towers. If this doesn’t provide the necessary ‘drop’ in height then the bogie support ribs within the Bachmann chassis block can be ground down.

 

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Carrying rib for bogie tower

 

It follows that it is also necessary to reduce the overall height of the tower lowering the shoulders of the top spigot so that it can poke further through the chassis block.

 

I have not attempted this route as I was seriously unhappy at the thought that I was ‘damaging’ both the chassis block and the bogie towers and that in the event that the results were not as expected the process would not be reversible. I also had a residual concern as to whether the free rotation of the bogie towers might be compromised, particularly where there were changes of both horizontal and vertical track profile at the same time.

 

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Bachmann Bogie Tower Mk III

 

Bachmann have changed the design of their bogies and the latest (I shall call their MkIII bogie) has thicker ‘wings’. It occurs to me that the required drop in height might now be achievable without the need to grind any of the chassis away. I wonder if anyone has gone down this road?

 

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Bachmann Bogie Tower Mk II

 

I decided to avoid any grinding and to concentrate on the bogie towers. (Mk1 with four wheel drive and MkII with six wheel drive are identical in this respect.) If I was to be unsuccessful spare towers are available off eBay or from Bachmann. First I shortened the two support pillars that feature either side of the drive shaft. Ideally these should be reduced in height by 2mm but in retrospect it would be better to aim for 1.5mm. I think they are formed from Nylon. They are certainly very tough and do not readily cut with a craft knife. Too much pressure with a knife blade and there is a danger that they will snap off the main body of the bogie. I used part of ball point pen to make a circular collar to slip over the column supports and to act as a height guide whilst I carefully pared away the top of the column. Getting both pillars the same height is paramount.

 

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Bogie Tower caps, 'as bought' left, 'ground out' right

 

The caps that are screwed to the tops of the tower also need some attention. I used a grinding tool attached to my Proxon drill (similar to a Dremel). The tab at the ‘back’ of the cap that presses down on the worm drive needs to be reduced in height to match the change in height of the columns. Depending on whether the column height was reduced by the full 2mm or by a slightly lesser amount it might also be necessary to grind some of the plastic away from the underside of the cap to make more space to accommodate the drive shaft coupling to the worm. I have to admit to the process being rather one of trial and error.

 

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Bogie Towers, before left, after lowering right

 

I should also point out that the columns have a blind hole in them for accommodating the cap fixing screws. I drilled these deeper with a 1mm diameter bit.

 

After reassembly and reattachment to the metal chassis block my model sounded like the proverbial ‘bag of nails’. I spent a couple of evenings trying to figure out what was catching only to eventually realise that the bottom of the tower to chassis fixing screw was rubbing on the drive shaft coupling beneath the cap. I used a file to remove about 1mm in length..

 

There are three views below of finished bogies.

 

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Bachmann Deltic Bogie Tower - Lowered

 

There are a couple of guides on either side of the worm. These seemed to be surplus to requirements and at one point I thought they might be catching the underside of the chassis block. I cut the tops off them.

 

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Bachmann Deltic Bogie Tower - Lowered

 

The space between the towers which accommodates the drive shaft coupling is very tight and I pared some plastic off the inner faces of the tower.

 

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Bachmann Deltic Bogie Tower - Lowered

 

I have now converted two sets of bogies and there are some views below of the reassembled models.

 

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Bachmann models D9002 and D9004 with lowered body shells

 

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Bachmann D9004 Queen's Own Highlander with lowered body shell

 

How does it work? Surprisingly well, there is a YouTube video showing one of the lowered models running round the layout.

 

 

 

I have included a scene showing the model successfully negotiating two pairs of Mr Peco’s old fashioned Medium Radius Streamline points from the 1990s.

 

What could possibly go wrong?

 

Everything appeared fine until I started to carry out some un-prototypical movements – running the wrong way through sets of points. I had particular problems with a Peco Streamline curved point. Coming from the curved branch the front wheels of the bogie would leave the track whilst exiting the point at the end with the blades. Whilst the Peco curved points have ‘form’ when it comes to causing derailments, there is another cardinal rule on any model railway to the effect that if all the other rolling stock runs faultlessly – then the fault is with the engine or wagon and not the track.
On closer inspection it was apparent that my model had a slight ‘lean’ to one side. The Bachmann towers are surprisingly precise and despite the apparent sloppiness of the tower fixings to the chassis it is essential that the caps at the top of the towers are perfectly level across the width of the chassis. (A slight fore and aft tilt doesn’t seem to matter so much.)

 

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Is everything square?

 

I placed a steel rule across the chassis and measured the height on either side. I kept the bogies a ’loose fit’ and stood the model on a glass chopping ‘board’. It was then relatively easy to adjust the tops of the columns to bring the caps at the tops of the tower level. How easy? Well it is easy enough to pare plastic away but I also had to add a couple of shims (homemade plastic washers) to the tops of a couple of the columns where I had been too enthusiastic. After squaring everything up the model runs perfectly.

 

A reminder

 

It makes life a lot simpler refitting the bogies into the chassis if the drive shafts are fitted the correct way round. The shafts are ‘handed’ and the spherical end needs to ‘pop’ into the bogie coupling whilst the rectangular ‘fins’ need to be able to slide within the motor coupling. I suspect that having the shafts fitted correctly makes the running quieter.

 

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Drive shaft spherical connection to bogie

 

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Drive shaft rectangular connection to motor

 

Conclusion

 

Is it worth the effort? I am not sure but I enjoyed the challenge.

 

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Bachmann Deltics with lowered body shells



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