Battery powered Bachmann K27

[DGE-Railroad]

Following in the footsteps of my previous conversions, this is the one I've been worrying about the most.

Ive ummed and ahhed about it because it can already use drop in adapter boards and has battery connections provided. I'm also aware I'm probably devaluing it by embarking on it.

But... I love this loco. I want it the way I'd like it and I felt ready to tackle it!

This will follow the approach taken with my previous conversions;
18.5v battery and Revo DCC receiver in the tender, driving an ESU XL and dual smoke unit.

This time however, I'm hoping to add a working rear coupler and animating the Johnson bar. Both of these mean more fabricating and the addition of servos, which is why I'm nervous!

Getting into the loco hasn't been too bad. The loco and tender have been electronically gutted. The forward weights in the loco have gone to make room for the smoke unit, and an existing hole enlarged to make a route for the cylinder smoke.

The tender weights have also gone to make more room

 

[DGE-Railroad]

Tender layout Trialled. All of the unnecessary amounts have been removed to free up space and the speaker will need to be moved forward.


The main power switch and receiver bind button are under the water hatch


Trialling a mounting framework for the decoder and dual smoke unit. The vertically mounted board is the smoke unit interface


It all fits quite nicely

 

[DGE-Railroad]

Not so much progress today. I've been getting my head around the Bachmann schematics to understand the loom.

I'd like to re-use the optical chuff triggers but from what I've read the outputs are floating and pulled high rather than low for the chuff. That will need inverting with an NPN transistor if I'm to try and use it. Another little headache, so maybe I won't bother with it.

Anyway, I took a break to fit one of Bill Davis' beautiful little brass smoke arrestors (the Bachmann one was squished).
The original Bachmann collar was retained and tapped through to mount the brass one

 

[The Tinker]

What do you use to connect Dewalt battery? I am looking at using dewalt battery in my grandsons loco I am doing for his birthday.

 

[DGE-Railroad]

What do you use to connect Dewalt battery? I am looking at using dewalt battery in my grandsons loco I am doing for his birthday.

Hi, so in the Mikado I converted, I used one of these to mount an 18v 2Ah DeWalt battery
Dewalt connector
In this instance that may not fit though, if so, a red or blue crimp on Male spade connector would work

 

[DGE-Railroad]

The tender decoupler is finished! Thank goodness.

Servo decoupler

It's running off a servo tester at the moment to check the operation. This also allows me to note the endpoint values which I will need to put into the decoder.

I'm going to try a linear servo for the Johnson bar once it arrives

 

[Greg Elmassian]

You should try the chuff, for all the effort you are going to, a perfectly timed chuff is a nice feature.

It's only one transistor to invert the signal, remember to power the board for the opto electronics.

Greg

 

[DGE-Railroad]

You should try the chuff, for all the effort you are going to, a perfectly timed chuff is a nice feature.

It's only one transistor to invert the signal, remember to power the board for the opto electronics.

Greg

Thanks Greg, yes after a good night's sleep, I'm reinvigorated enough to pursue it
Thank you for all of the information you have collated on your pages by the way, they've been a huge source of inspiration and knowledge for all of my conversions so far.

I had gutted the Bachmann loom but after spending a fair bit of time going through it all with a multimeter and referencing the schematics, I've realised I would be wise to keep the main distribution board below the cab as it contains the chuff, firebox flash, regulators and led resistors.

It also makes sense to keep the selector switches behind the smoke box door that allows switching the cab light and the identification/firebox lights between DC (permanently on via the main power bus) or DCC (those grounds to decoder output pins)

Both optical chuff signals normally go back to the tender where they are combined at JP1 and go to a decoder pin. I had hoped that JP1 stood for 'jumper' - it seemed logical. It turned out to be a small blob of solder between the two PCB tracks which seemed a bit strange - why not just print the tracks joined? I carefully examined it with the soldering iron and a solder sucker. Sure enough that's all it is, so by keeping the loco board, I can take the two tender feeds, combine them and invert them.

Writing this has made me wonder though, how the chuff signal is normally interpreted at this decoder pin given its inversion: the drop in board is supposed to allow decoder to work in the loco without any additional electronics? I've order a 2N2222 to do the inversion but I'm going to investigate how plugging a third party decoder in via the drop-in board would normally handle this...

 

[PhilP]

I'm going to investigate how plugging a third party decoder in via the drop-in board would normally handle this...

From experience.. Badly!

 

[DGE-Railroad]

From experience.. Badly!

Thanks Phil. Given that you know your way around the amps and volts, I'm glad I opted to ditch it

 

[DGE-Railroad]

Well that's strange...
According to this
Bachmann article
Regarding exactly this decoder I'm using, interfaced via the tender plugin board, no additional circuitry would be required in order to use the combined chuff signal...

 

[PhilP]

Ah! You have a few 'luxuries' I did not..

1. I was dealing with an older 'much-loved' model.
2. I did not have a DC board!
2. And, was not fitting an ESU decoder.

I must dig some info. out, on the ESU offering.. A make of decoder I am not familiar with.

 

[DGE-Railroad]

Ah! You have a few 'luxuries' I did not..

1. I was dealing with an older 'much-loved' model.
2. I did not have a DC board!
2. And, was not fitting an ESU decoder.

I must dig some info. out, on the ESU offering.. A make of decoder I am not familiar with.

Ahh! Phew
Well its going well so far - fingers crossed. I think I understand where I'm going with it so am feeling positive. I tend ti be overly cautious by nature when it comes to electronics

I'd highly recommend looking into the decoder. I'm nothing other than a satisfied customer but the only downside I've found so far is the online support forum tends to be a bit slow. There's a helpful Facebook group though.

I'd strongly recommend to anyone that's interested, just downloading their lokprogrammer software from the website, along with one of their factory files and having a poke around. It's great for 'taking a look' at the product capabilities since you dont need any hardware unless you actually want to read/write a decoder.

Its hugely flexible. Dauntingly so, I thought before I got to grips with it, but it's quite logical and I think it's just that there's a lot of functionality to try and expose in one GUI. It could perhaps benefit with a basic/advanced view switch, or some kind of wizard to help guide. I've only really scratched the surface myself.

 

[Greg Elmassian]

The esu can apparently take a positive true as well as a negative true chuff input.

Most can only take a negative true.

So you should be home free!

Greg

 

[DGE-Railroad]

The esu can apparently take a positive true as well as a negative true chuff input.

Most can only take a negative true.

So you should be home free!

Greg

Ahhh! That explains it.

Clever stuff. Thanks Greg
I'm splicing the loom together tonight. Hopefully there'll be lights, movement and some sound before too long!

 

[Greg Elmassian]

Also, the chuff system is adjustable, the blade that interrupts the ir beam can be slid to adjust your chuff timing exactly.

Greg

 

[DGE-Railroad]

Also, the chuff system is adjustable, the blade that interrupts the ir beam can be slid to adjust your chuff timing exactly.

Greg

Oo, that's a nice feature. Thanks for the heads-up!

 

[DGE-Railroad]

Overnight I dusted off my old 3D printer and had a go at printing a tool battery connector to hold some blade terminals. It's not awesome but it works


I've also had a go at improving the hideous plastic coal load. Canopy glue over the lot, followed by cat litter (because my daughter had some to hand), sprayed over with 3M spraymount, then airbrushed black.



Last but not least I managed to get a few minutes break in the childcare today, to run a quick test of the electronics.

K27 electronics test

I ran off a bench supply for simplicity (plus I can monitor the current draw) and didn't bother connecting up the smoke for this first run. The servos aren't connected either at the moment.

It all went pretty well for a first run. The motor calibration clearly needs doing as that's off. Also, the chuff is very strange. I'm not sure why. Somethings not right there but I'm pretty sure I've done nothing different to what would occur for a plug-in board installation...

 

[DGE-Railroad]

Second test, post motor-calibration
That's sorted the motor control.

I also put the decoder back on the programmer and realised that after setting the chuff trigger to manual, I'd somehow managed to leave the chuff sensor at 21 triggers per chuff

The chuff now seems better but still a little off-beat so may need to look at the optical adjustment angle.

I also took the opportunity to hook up a pair of servos. I've assigned a coupler clank to the Johnson bar channel in order to distinguish them. I haven't heard one in operation before but think the coupler noise made a passable impression of a Johnson bar. I may need to find a different coupler sound for the coupler itself.

K27 power up attempt 2

 

[DGE-Railroad]

Final coupler test. Endpoints finalised, DCC-operated servo via the decoder, with a coupler sound chosen from the ESU library pack

Coupler finished

Just waiting on the linear servo now. In the meantime, the loco and tender are getting a matt clear coat, to dull them down.
I've yet to get to grips with weathering but just shooting the loco with a clear matt coat makes a big difference