New Bachmann Class 158 - P4 conversion

[Triode]

A while ago I converted two of Bachmann's retooled Class 158s to P4, but am only now getting round to doing a bit of a write-up, which I hope others will find useful. I haven’t attempted springing or anything fancy, just replacing the wheels so it can run on 18.83 track.

Each car of the 2 car set has both a powered bogie and an unpowered bogie. I'll tackle these separately as the approach for each was very different.

Unpowered Bogies

From the factory, the unpowered bogies consist of split axles running in pinpoint bearings. Each half axle is 2mm in diameter and is live to the wheel, with isolation between wheels coming from the plastic centre section of the axle into which the half axles slot. The pinpoint bearings double as current collectors, and the bearings on each side of the bogie are connected together as a single metallic component; this component also includes a vertical conductive tag which makes sliding contact with the PCB to transfer current without pickup wires. Here is how it looks when dismantled:

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I liked the factory-fitted system, especially the lack of pickup wires between the bogie and the body. Making disassembly simple. Unfortunately, the thickness of the bearing/pickup assembly does not leave enough clearance for P4 wheelsets. As a solution I fitted waisted brass bearings into the plastic bogie mouldings, so that the rear faces sit flush; this provides enough clearance to fit P4 wheelsets, but of course removes the ability of the bearings to double as electrical pickups.

Here are the new bearings...

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And here are the P4 wheelsets...

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My solution to the pickup problem was to cut away the bearing parts of the original current collectors and retain only the centre section with the fixing holes and the vertical tag. To this I soldered classic phosphor bronze wiper pickups to brush against the backs of the wheels.

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I'll post the process for converting the powered bogies soon.

[hollybeau]

Can I ask where you got that horseshoe-shaped wheel press/puller? Looks a useful piece of kit and one I have not seen before. Enjoying the blow by blow description - keep them coming.

Bryan

[David Thorpe]

Very interesting thus far - I look forward to reading more.

David

[Triode]

Can I ask where you got that horseshoe-shaped wheel press/puller? Looks a useful piece of kit and one I have not seen before. Enjoying the blow by blow description - keep them coming.

Bryan

I got the wheel puller from a supplier in Germany: https://www.fohrmann.com/en/search?sSearch=wheel+puller

They have a lot of other useful stuff too. I also have the version with the sliding hooks that move side-to-side, but I managed to break one of the hooks trying to remove a gear from a printer stepper motor, which is probably a much heavier application than what it's intended for. I see they sell replacement hooks separately though so hoepfully I can fix it!

I'll post the rest of the Class 158 conversion soon.

Cheers

Liam

[Simon_S]

I widened the bogies of my Bachmann 4TCs so I could still use the original bearings/pickups:
P4 Conversion of Bachmann Split-axle Bogies

[Triode]

Thanks for that Simon. A very neat solution. I'm a big fan of bearing pickups which avoid the hassle of wipers.

The next one on my list to tackle is the Realtrack Class 156. This also uses bearing pickups and they do have enough space between them for P4 wheelsets. The difficulty though is that the live stub axles the wheels fit onto are a non-standard diameter. From memory I think they were 1mm or 1.5mm diameter, whereas all the 10.5mm wheels I have are for 2mm axles.

I thought about drilling out the plastic centre portions or the axles to take 2mm stubs as an interference fit, but am reluctant to attempt this in case they are damaged as spares are likely to be unobtainable. The only other approach I can think of is to make some custom stub axles that are the correct (small) diameter but with a thicker section part way along to take the wheels. I imagine though that turning these on a lathe would be the only way to achieve the needed accuracy, which isn't something I have access to at present.

If anyone has any ideas on this one, or better yet has tackled the Class 156 before, I'd be very keen to hear your thoughts!

[shipbadger]

I had the same problem with two 'flying banana' railcars I converted, one to P4 and one to EM. I found some brass tube of 2mm diameter and a nominal 1.5 mm inside diameter. No problems fitting the Steam Era wheels onto the tube but the new 1.5mm axles were a sliding fit. Used the old technique of the edge of a file to create knurled ends on the axles (after fitting the gear to the centre) and added a drop of Loctite locking compound for good measure. Both railcars are trundling around still.

Tony Comber

[jim s-w]

And here are the P4 wheelsets...

DSC_4485.JPG

I'm a bit confused by this. As you fitted wiper pickups why not just use the wheel sets as they came on the original axles?

[Triode]

I'm a bit confused by this. As you fitted wiper pickups why not just use the wheel sets as they came on the original axles?

Hi Jim,

It was because there was insufficient space between the newly fitted brass pinpoint bearings to take a standard 26mm long pinpoint axle, which is what the Black Beetle wheels I used came on. So I transferred the wheels to the original stub axles which allowed me to adjust the length over pinpoints until it was a good fit into the bearings.

I could have bored out the holes in the plastic side frames to let the bearings sit deeper and take standard length axles, but having done this before on wagons it seemed like more hassle than the above.

[jim s-w]

Ah makes sense now