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Chipping a Brawa Köf II

buffalo

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Something a little different from the mostly GWR content in this blog. If you have read any of my other (layouts) blog, you'll be aware that Camerton has been on hold for a while while I rethink and strengthen my scenic skills. In the meantime, I've been working on a wholly imaginary layout called Nowhere or Nessun Luogo or Nirgendwo according to language preferences. This is a fairly simple HO and HOe layout that will allow me to run whatever continental stock I like without too much concern for prototype credibility. I'd better post an update on it soon as it has come on some way since the last entry.

 

Along with the layout developments, I've been acquiring a very mixed collection of German, Austrian and Italian stock and slowly converting the locos to DCC. I was lucky to discover that a Fleischmann V100 purchased on ebay unexpectedly contained a Lenz silver chip, but everything else will need to be converted. So, I thought I might include some examples here of the more interesting DCC conversions.

 

That brings me to one of my most recent acquisitions, the delightful little Brawa Köf II.

 

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At first sight it may look like a tricky job to convert this little euro-kritter to DCC but the cab is easily large enough to hide a small modern decoder:

 

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Potentially more of a problem is the solid metal chassis which is live to the right hand rail. The single wire from the motor goes to the insulated pickup on the left side. The motor contact nearer the camera in the next photo simply contacts the chassis below the rear motor support. Somehow this will need to be insulated.

 

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On the positive side, this model was also made in an AC version with an additional wire to the central skid pickup, and separate wires to each of the motor terminals. These four wires were taken through to the cab where the reversing relay was located. The beneficial side-effect of this version is that there are already grooves in the chassis to take these wires. One of these is immediately to the left of the black wire in the above photo. The larger slot for the other three wires passes through the rear motor mount.

 

Next, the underside. The two screws secure the baseplate and the two holes, one threaded, near the centre of the plate are for fixing the pickup skid on the AC version. I'll return to these later.

 

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With the baseplate removed, the axles, idler gears and pickup can be extracted.

 

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The next photo is out of sequence, but shows how I dealt with the problem of the lower motor terminal contacting the chassis. The area under the terminal was milled out to provide about 1mm clearance below the terminal. This broke through into the slot for one of the idler shafts, but the shaft is still supported by a good thickness of metal at either end. Additionally, the rear motor mount was undercut to provide clearance around the rear end of the terminal.

 

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Now the decoder could be fitted. I used a TCS Z2, one of the smallest of current decoders. I'll also be using these fitted into the side tanks of Liliput U class HOe locos. The leads were measured and trimmed, and the lighting wires which won't be used, at least for now, were tied back. The black wire was passed through the hole used by the original pickup wire and soldered to the pickup.

 

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The axles and drive gear were replaced next and the red wire fed through the hole in the milled area below the lower motor terminal. This was then soldered to a small brass tag made from an old bit of scrap etch. The tag was secured to the tapped hole in the base plate with a short 2mm screw. This provides the input to the decoder from the live chassis.

 

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Next the orange lead was soldered to the lower motor terminal and the grey to the upper one. A small piece of insulating tape was added over the lower terminal. Really this was just belt and braces becauses the milling ensured there was adequate clearance. The motor was placed back into its supports and the wires pressed into the slots in the chassis casting.

 

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The body was then refitted and the decoder secured below window level with a small piece of sticky sponge pad. The body securing screw was replaced to hold the body down on to the chassis. This was necessary before testing because the worm is held in mesh by the body pressing down on the top of the motor.

 

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Everything worked first time when tested :D

 

Now, what about lighting? The back would be easy enough, but I think the smallest SMD LEDs that I could see would still be too big for those front lights.

 

Oh well, I still have the detailing bits to fit, and quite a few more locos to chip :rolleyes:



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Yes, I must admit that I first noticed it when I was taking these photos, but you can see it spinning through the grill at the front.

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We seem to have a similar taste in locos - although rather far from GWR elegance, the Köf is such a great little loco! If only we had flywheels fitted as standard in UK outline RTR locos.

 

Congratulations on making the chipping work first time. It does promise to become a very interesting and unusual layout.

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We seem to have a similar taste in locos - although rather far from GWR elegance, the Köf is such a great little loco! If only we had flywheels fitted as standard in UK outline RTR locos.

In many cases though a flywheel just messes up the back-emf of the chip and you're better removing them.

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We seem to have a similar taste in locos...

Yes, indeed, but at least I find it reassuring that my inability to stick with a single prototype for more than a few days is not a unique affliction :rolleyes:

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Yes, indeed, but at least I find it reassuring that my inability to stick with a single prototype for more than a few days is not a unique affliction :rolleyes:

No, quite widespread I believe. :) But if we can't give in to impulses in our hobby, then I don't know where...

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In many cases though a flywheel just messes up the back-emf of the chip and you're better removing them.

That's an interesting thought, Craig, not one that had occured to me before. However, I've always understood that the use of BEMF by a controller/decoder was simply a negative feedback mechanism that allowed the controller to take account of the actual electro-mechanical performance of the motor. Yes, the presence of the flywheel should affect the BEMF, but only in reflecting what is actually happening to the motor. Whether or not the decoder can accommodate the behaviour is, of course, a different question.

 

The flywheel on the Köf is so small that I wouldn't really expect it to do much more than smooth out the cogging of the three pole motor. Only time will tell, but I'll have to wait until it is run in and I have enough of a layout to thoroughly test it on.

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