Tsunami 2 install into N scale MP vanderbilt tender

As the first step in customizing my Bachmann N scale 2-8-0 (the 2017 Soundvalue release) to more closely resemble UP/OSL #618, which is currently in a boiler rebuild/restoration at the Heber Valley Rwy in nearby Heber City, UT, I installed a Soundtraxx Tsunami 2 Steam 2 decoder and 12 x 15mm sugarcube speaker into a Model Power Vanderbilt tender I acquired thru eBay. This was my second Tsunami 2 install (the first being into a Bachmann N scale Spectrum USRA short tender which I coupled to my Bachmann 4-6-0... maybe I'll post a thread on it at some point). I really like the motor and sound control possible with the Tsunami 2 decoders...

Here is the exploded view of the tender (I am showing the coal bunker, but I used the oil bunker that also was provided):


Here's the bottom view.


From the factory, the MP tender has four wheel electrical pickup with axle wipers. I wanted to convert it to 8 wheel pickup with needle bearing contacts. So, I purchased a pair of Bachmann tender trucks, shortened the contact ears, and soldered some 32g flexible wire leads:


In order to mount the Bachmann trucks to the MP tender, I had to modify the tender, constructing kingpin posts on which the trucks swivel. I also had to smooth out the bases where the trucks would ride and to clear the drawbar. I wanted to make as few mods to the loco as possible, so decided to use a Bachmann drawbar to mate the tender to the loco. So you will see the forward pin is a little longer (the recess is a little deeper), for attaching a Bachmann drawbar between the truck and tender body:

In this image of the inside of the tender with the weight removed, you can see the holes drilled for the wires from the trucks:


I also had to open up the front of the tender frame for the wires between the tender and loco:


and trim a notch in the forward frame/subfloor to provide some space for the wires to pivot as the loco & tender rounded curves:


There's LOTs of track power wires to connect. I initially planned to use the Bachmann drawbar to carry current from loco to tender, so for each each polarity, there were to be four wires: one from each truck, one from the drawbar, and one coming from the loco frame. To each side, I would then have to connect the track power leads to the decoder.

In this image, you can also see how much of the of the original weight I was able to include.

To make all these connections, I decided to use power busses made from 40 year old PC board tie material I had laying around from past track laying projects. I filed recesses on either side of the weight, and used liquid electrical tape to "glue" the PC board power busses to the weight (the weight itself was first liberally coated w/ liquid electrical tape):

I planned to install an 11mm x 15mm sugar cube speaker in the oil bunker. After considerable test fitting, I finally decided to forego the use of the provided speaker enclosure, and use the oil bunker itself as the enclosure. I built a frame for the speaker, and glued it into the bunker, sealing all possible gaps with liquid electrical tape:


Then, I sealed the speaker into the frame with liquid electrical tape. The speaker leads have a micro connector, allowing me to remove the oil bunker from the tender w/o unsoldering anything:


Now, it's time to install the decoder, a Tsunami 2 Steam 2 from Soundtraxx, and disconnect the old tender with its Economi decoder:


In this image, you can see the decoder in the new tender. resistors for the headlight and backup light are taped to the decoder. The backup light leads have a micro connector, allowing the tender shell (w/ the light) to be removed w/o unsoldering anything (I haven't yet installed the backup light... it is the smallest warm white SMD LED). I was able to test the sound in the new tender, before cutting loose the old. Also, before clipping the 6 wire leads to the loco, I labeled each with an identifying tag.

For reference, here is a pic of the factory Economi decoder, with the 6 connections labeled (bottom to top: red orange, blue, white, grey, black). I think the solder pads marked with an asterisk are for a backup light which was NOT part of the factory install (I did not confirm this):


Putting it all back together! First, I found the Bachmann drawbar I planned to use was too short. I found another that was a little longer, but the drawbar no longer carries electricity from the loco. That's OK, since the drawbar connections were redundant... current from the loco is also carried by wires.

In this view, you can also see I was able to fit the capacitor supplied by Soundtraxx in front of the decoder, under the speaker. In this pic, the backup light has been installed in the tender shell; you can see its leads with micro connector. There is also a slab of tungsten putty under the after portion of the decoder, and some lead strips glued into the oil bunker alongside the speaker. (the red arrow points to the screw that connects the left side frame to the wire lead that carries (left side) track power to the tender. It was loose from the factory, causing intermittent power pickup until I found the issue and tightened the screw)

Here's the final result of Phase I:


Here's a link to a (longish, not so great) video.



I released the brakes and applied the brakes, and blew the whistle/rang the bell after the loco had stopped... All sounds from start up to stop, and modulation of the exhaust and rod clank, were automatically triggered by the decoder (by BEMF) as the engine drifted down grade or labored up grade.

I think it turned out pretty well. Phase 2 (in progress) will be re-detailing a spare loco shell to better resemble UP/OLS 2-8-0 #618 (requires moving domes, bell, running boards, adding more cab windows, installing a new, brighter SMD LED in a new headlight, and more!). Phase 3 will be redetailing the tender to a more UP-like configuration (I think it is modeled after an SP Vandy?).

 

Mods: I forgot to indicate in the title that this was a N SCALE install. Could someone change the title (or tell me how) to:

"Tsunami 2 install into N scale MP vanderbilt tender..."

Thanks! Dave

 

What my first post doesn't really tell is all the things that didn't work out...

The trouble spots that provoked the most head scratching were:

Getting the Bachmann trucks mounted to the MP underframe... totally different mounting methods. Bachmann fits a large hole in the truck over a kingpin post, with a screw as the retainer. The post is the pivot bearing. MP just put a screw thru a (smaller) hole in the truck into the frame bolster, with the screw as the pivot. I spent several days trying to adapt the Bachmann trucks to the MP frame, by filling in the hole with epoxy and drilling a new hole, etc... and it just never worked. I tried making posts of brass tubing, but couldn't get them securely glued to the plastic tender underframe. In my current scheme, I chucked some styrene tubing into my dremel and "turned" it down with sandpaper until the truck would slide over it. That extends thru a styrene disk that makes the surface the truck rests on. All "welded" with liquid plastic cement to the bottom of the tender. The screw has another piece of plastic tube over much of its shaft, making a shoulder so it can't be overtightened. I am a little concerned about how robust the styrene pieces and joints will be... but so far, so good...

Fitting the Bachmann drawbar to the tender was another part of adapting the trucks. This required considering both the mechanical connection to the tender (fitting over the kingpin of the front truck, and clearing space so the drawbar would pivot freely) and the electrical connections. I originally modified a Bachmann drawbar, shortening the stiff conductor wires on the tender end, and soldering flexible wire leads that would then be routed into the front of the tender (sorry, I never took photos of the drawbar isolated from the tender, but you can see the electrical leads from the drawbar in pics 8 and 9)... But that drawbar ended up being too short (I wanted closer coupling, but it was so close that there was no flex between the loco and tender; compare the drawbars in the two tenders in pic 12). I abandoned that drawbar, and just used a somewhat longer Bachmann drawbar from which I completely removed the contact wires. Maybe someday I'll go back and install the drawbar contacts, but it runs great now.

Mounting the speaker also caused a bit of angst... I really wanted to use the 11 x 15 mm speaker (I had an 8 x 12 as a backup). Having a thing for symmetry, I kept trying to have the speaker mounted either horizontally or vertically in the coal bunker. I trimmed corners on the speaker enclosure, considered making a whole new custom enclosure, but just couldn't get it to fit. Finally, I realized I could just mount the speaker to follow the slope of the bunker itself, and use the whole bunker as the enclosure. Then, it was just a matter of making a frame to adapt the speaker to the inside dimensions of the coal bunker. Tried first cutting the frame from sheet styrene, but the styrene kept breaking. It took a few failures before I realized it would be easier to glue the frame together from lengths of strip styrene...

The last major question was "would the electrolytic capacitor fit in front of the decoder and underneath the speaker (would I be able to put it all together?" Fortunately, the answer was "Yes!" But, I had an SMD tantalum capacitor (with much smaller footprint) as a backup plan, just in case.

After that, it was just a matter of fitting in as much weight as I could to help tracking and electrical pickup. I put a decent slab of tungsten putty under the rear of the decoder, making up some of the loss from cutting down the factory weight. I also added a couple of strips of lead ribbon (old fishing weight) into the coal bunker. The tender tracks well, and I haven't had pickup issues since finding a loose connection in the loco.