Checking Wheelset Back to Backs

As well as producing 3D printed parts I also help solve problems on layouts, and one problem which arises is locomotives and rollings stock not running smoothly through turnouts and crossings. This is often due to the distance between the wheels, or back to back, not being correct.  In this post, I’ll show you how I check and adjust this.

Railway wheels, irrelevant of size and design, all have the same basic parts.  An axel, tire, rim, and flange.  The tire rides on the rails, and is held in place by the rim.  The flange sits inside the tire and the axel holds both wheels together, forming a wheelset.

The tire is actually tapered which causes the wheelset to sit centrally between the rails.  As the wheelset rolls along it will naturally center itself due to gravity.

But as wheelsets round a curve a centrifugal force will try to push the wheelset off the rails towards the outside of the curve.  As the wheels go faster the centrifugal force gets larger and will eventually overcome gravity, but the flange prevents the wheel from going past the rail.

The distance between the rails is fixed, as is the distance between the flanges. This distance is called the back to back.  Wheelsets will run if this distance is wrong, providing the flanges fit between the rails, but the problem comes when the wheelsets need to pass through a turnout or crossing.  The distance between the parts of the turnout is specifically set, and if the back to back is not right the one wheel will run in the correct place and the other will bind, jam or ride up over the rails causing a derailment.

With model trains, unlike the real thing, wheelsets are either made entirely from plastic or metal where the wheels have to be electrically isolated from each other so as not to short.  The real railways like electricity to pass through the wheelsets as they use that for train detection. The plastic wheelsets, as shown below, are usually injection molded in one piece and very accurately.  So unless they’re damaged the back to back dimension should be correct.

Metal wheelsets, as shown below, either have one or both wheels isolated from the axel.  This wheelset has a plastic isolator between the far wheel and the axel.

The problem here is the wheel on the far side can sometimes move on the axel as the plastic isolator is only held in place by friction.  This changes the back to back dimension.  Also some manufacturers have better quality control than others and it’s not unheard of for a brand new item of rolling stock to be incorrect right out of the box.

So how can this be fixed?  As always in model railways, there are several ways of doing the same thing, but for me, I like to use a gauge.  The NMRA (National Model Railroad Association) supply gauges for all the major scale and these include back to back checks as well as many other things for checking turnouts etc.  The gauges are also the same size as the loading gauge for that particular scale so you can check tunnel heights and platform clearances etc.

Another tool I tend to use for N scale is the Micro-Trains coupler height gauge. I’ve written about this before in my post about fitting Micro-Trains body mount couplers to older N Scale freight cars, which you can find here.

As well as being a coupler height gauge, it also has a wheel back to back check and a rail spacing check.  In the image above the wheel back to back check is on the near side and the rail spacing check is on the far side.

To use the gauge, simply put the wheelset into the slots; if they fit they are correct.  The set below is clearly out of tolerance.

As the wheel at the bottom of the image is fixed to the axel it’s the one at the top with a plastic isolator which will slide, and using a pair small pliers I can easily slide the wheel up until it’s in the right place.

You don’t have to take the wheelset out of the truck to check it when using either the NMRA or Micro-Trains gauge, but if you need to adjust the wheel back to back I would recommend taking it out as the pressure could easily damage the plastic truck.

With all your wheelsets back to back correctly adjusted you should find your trains run nice and smoothly through your track work.

Alco C-855 N Scale ESU LokSound Install – Part 3 – Engine Speed Setup

Several weeks ago in July I shared with you my install of ESU Loksound sound decoders into a set of my Alco C-855 locomotives, you can find the post here.  Then in August, I showed you how I improved the running of the locomotives by adding some stay alive capacitors, you can find that post here.  In this week’s post, I’m going to share with you the final step which is setting up the sounds for multiple engines.

Most suppliers of ESU sound decoders give you a choice of sounds when you purchase the chip and they will load the sounds on for you.  But to add your own sounds or load on a downloaded sound scheme you need an ESU Lokprogramer and the accompanying software.  These, along with a computer, will allow you to change all of the settings of the decoder.

However, they can be fairly expensive so if you have your decoders with pre-loaded sound schemes you can use other devices to adjust the settings. For example, although I use a LokProgrammer I also use a Sprog II from sprog-dcc and the DecoderPro software from JMRI.  The Sprog II is relatively cheap and the DecoderPro software is free to download.  Together they will allow you to edit the setting of just about any DCC decoder but please note it will not allow the upload of sound files.

The sound file for the C-855 was downloaded from the ESU website and comes with all the normal functions such as horn, bell, coupling, etc.  The new versions also come with ESU’s Full Throttle settings. These include features such as Drive Hold, Independent Brake, Run 8 and Coast.

These functions can be fairly complex but in short, they work like this:

Drive Hold when pressed keep the model motor running at the same speed and as the throttle is increased or decreased the revs of the engine changes.  Ideal if you are pulling a slow heavy train uphill and you want it to sound like it’s working hard.

Independent Brake when activated slows the train to a stop without adjusting the setting on the throttle, when released it speeds up again to the throttle setting.

Run 8 when activated increases the sounds of the engines to maximum revs irrelevant to the speed of the train.  This is great when simulating a heavy train about to start moving and is my favorite Full Throttle function.

Coast reduces the revs of the engines to tick over irrelevant to the speed of the train.  This is great when running downhill or for light loco movements.

Out of the box, only the Drive Hold & Independent Brake are set up as you can see from the function list below:

F0 Directional Headlights
F1 Bell
F2 Playable Airhorn
F3 Coupler
F4 Dynamic Brake
F5 AUX3 (Rotary Beacon)
F6 AUX1 + AUX2 (Front Ditchlights)
F7 Switching Mode
F8 Sound (On/Off)
F9 Drive Hold
F10 Independent Brake
F11 Radiator (Fan) Sound
F12 Dimmer (Headlights)
F13 AUX4 (Rear Ditchlights)
F14 N/A
F15 Fast Spitter Valve
F16 Spitters on Shutdown
F17 Brake Set / Brake Release
F18 Sanding Valve
F19 Short Air Let-Off
F20 Compressor
F21 Slow Spitter Valve

As standard one of the first things I like to do for my trains is set the Run 8 function to the F5 key, as I don’t put rotary beacons on my models this key is free.  I will show how to do this first using the LokProgrammer and then with JMRI through the Sprog II.  One thing to note, it’s a good idea to save the setup before you alter it, that way if everything goes wrong you have a backup of the original settings.

In the LokProgrammer software, you can see what each function is assigned to in the function mapping tab.  As standard F5 is set to AUX3.

I change this as shown below.  I have also set F6 up as the coast function.

Sometimes, if you’re reading the settings form the locomotive rather than a downloaded file, the name of the sound does not appear, just the slot number.  By default Run 8 is normally sound slot 20 and Coast is sound slot 21.  The changes can then be written to the decoder.

With DecoderPro the process is similar but it takes a little longer as you need to read all the settings from the decoder before you adjust any, otherwise you could overwrite something you didn’t want to. (Please note the Decoder Pro Screenshots are from a different loco).

With the F5 & F6 corrections made the screen looks like this.

Normally that is enough setting up and here is a short video of a single C-855 staring up, then having the engines run with Drive Hold on and lastly the Run 8 function.  Because the C-855 had two diesel engines you here the first fire up then the second.  Also both engines run at slightly different speeds so they are not simply copies of each other, I will explain more about that later.

As the same sound file has been installed in all three locomotives, the two C-855s and the C-855B, all three locomotives are running on the same DCC address so they all respond at the same time, as you can hear below.

The volume is much louder as we now have three speakers pumping out the sound but the problem is although the two engines in each locomotive are running a different speeds, each locomotive sounds exactly the same.  And I don’t think Alco managed to achieve that!  So in order to improve the realism, I will set each of the six engine sounds so they all run at there own speeds.  The change doesn’t want to be much, but a little adjustment can make all the difference.  The great thing about the ESU decoders is you can make adjustments to individual sound files without affecting the overall sound.  After all, we want the bells and horns to be the same across all three locos.

With the LokProgrammer on the function mapping page F8, which turns the sound on and off, controls two sound slots called ‘Dual-ALCO-16cyl-251C-FT-PM#1’ and ‘Dual-ALCO-16cyl-251C-FT-PM#2’.

Clicking on the drop-down menu these are sound slot 1 and sound slot 23.

Switching to the ‘Sound Slot Settings’ tab the setting for all the sound slots can be adjusted.

As you can see below sound slot 1 has a maximum and minimum value of 126, which is 98.44% of the original speed.

But sound slot 23 is set to 130 which is 101.56% of the original speed.  And that’s how the two engines run at slightly different speeds.

So for the three locomotives, I will set the sound slots up as follows.

C-855 60 – Sound slot 1 = 126 (98.44%)
C-855 60 – Sound slot 23 = 130 (101.56%)
C-855B 60B – Sound slot 1 = 124 (96.88%)
C-855B 60B – Sound slot 23 = 128 (100.0%)
C-855 61 – Sound slot 1 = 132 (103.13%)
C-855 61 – Sound slot 23 = 136 (106.25%)

And they sound like this.

Of course, the difference between the locomotives could be increased to give an even more noticeable difference, the difference is a personal preference.

With Decoder Pro these settings are in the ‘Sound Levels’ tab.  Again you will need to read all the settings from the decoder first but you can save them so you don’t have to read all three locomotives.  As with the LokPrograammer software the ‘Function Map’ tab will tell you which sound slots are operated by function F8.

Sound files for the Mallet and articulated steam locomotives, such as the Big Boy, use the same system to archive slightly different chuff sounds for each set of cylinders.

There are lots of settings available with these decoders which allows you to customize your locomotive, or as in this case a set of three.

These C-855s are now finished and ready to rumble their way up the track.

Next week I’ll be looking at the next step in my OO NEM dummy knuckle couplers.

Alco C-855 N Scale ESU LokSound Install – Part 2 – Stay Alives

At the beginning of July I showed you how I install ESU LokSound decoders in my C-855 kits.  You can find the post here.  This week I’ll show you how I added a small stay alive system to improve the performance of the locomotives.

With just the ESU LokSound decoder and speaker installed in the C-855 chassis, as shown below, the loco ran reasonably well but it did hesitate a few times on some point work.

This hesitation was down to dirty contacts in the pickups.  As the power supply was briefly removed from the decoder the locomotive came to a stop and the sounds went off, then it went through its start up cycle again.  As the other two locos in the set are still trying to run, this can be fairly annoying.  As well as cleaning the contacts and wheels I decided to add some stay alive capacitance to each locomotive.  A stay alive system is just what it sounds like; it keeps the decoder alive when the power is briefly lost.  ESU do sell their own stay alive devices, which are very good, but they’re fairly expensive, so I prefer to make my own which also allows me to make them to fit whatever space I have.  The only components I use are capacitors, a resistor and a diode.

The capacitors are 220uF 16Vdc Tantalum capacitors, the resistor is a 100Ω 0.25w and the diode is a 1N4007.  These are all parts which are readily available from most electrical stores or online.

The capacitor is designed to be fitted to a circuit board and is very small, which is ideal for N Scale locomotives. 220uF means the unit has a capacitance of 220 micro farads. You can get similar size capacitors with more capacitance such as 330uF but the price goes up. The 16Vdc refers to the maximum amount of voltage the capacitor can handle; because N scale DCC systems run between 12v and 16v, and the decoder drops the voltage by around a 1.5v, the capacitor will be receiving between 10.5 and 14v, so I find these are fine.

Be careful when buying these Tantalum capacitors; there are a lot of cheap ones out there with a low quality control.  It may say 16Vdc but if they’re cheap that may be an approximation.  If you put too many volts onto a Tantalum capacitor it will blow up, very loudly and dramatically.  The best way I can describe it is like a Roman candle.  And you don’t want that happening inside your locomotive!  The SOO SD50 below just had that happen with some cheap capacitors and the flames went up in the air by about a foot and blew a hole in the shell before I had a chance to cut the power.  So I would recommend a quality supplier.

The Tantalum capacitors have two metal tabs on the rear to solder to and a strip on one side to indicate the positive connection.

For these locomotives I’ll be using a bank of three Tantalum capacitors connected in parallel, which will give 660uF.  That isn’t a lot and won’t keep the motor turning, but it will give a few seconds to the decoder to keep the sound running, which is all I need. With all three locomotives working together the momentum and power of two out of three will jog a stalled loco enough to get it moving again without the decoder losing power and restarting itself.  I’ve glued these three together with superglue.

I’m going to put the capacitors in front of the speaker.  There is room to put in more, and normally the more you have, the better, but I want the space for the other parts.

The resistor and diode perform two important tasks. They are both connected to the positive capacitor terminal and positive (blue wire) connection on the decoder.  The resistor is used when the system is charging.  Power flows from the positive connector on the decoder into the capacitor to charge it.  As it passes through the resistor the current is reduced, which causes the capacitor to charge slower than normal.  Otherwise the DCC command station would detect the inrush of current and think there’s a short circuit when you first put the loco on the track.   The diode is there to bypass the resistor when the stay alive system is in use.  If the track power is lost the power flows from the capacitor back into the positive connector, but we don’t want any resistance.  As the diode wire is thicker than the resistor’s I wrap the smaller wire around the larger, as shown below.

I then solder the connections.

And lastly trim off the excess.

The new ESU Loksound V5 Micro decoders have a Next 18 plug, as described in the earlier post, as well as six solder pads.

The two we’re interested in are shown below.  I have tinned the solder pads with solder.  The one on the right is the positive connection, which is the same as the blue wire.  The left pad is the DC negative or common ground for the decoder.

To join all the parts together I start with the capacitors.  Using the off-cuts from the resistor I join the capacitors together by soldering the wire to each pad.

I then solder the diode and resistor to the positive side ensuring the band on the diode is on the far side from the capacitors.  This is because DC power only flows one way through a diode, towards the band, and we want it to flow out of the capacitors to bypass the resistor when in use.

I then solder a wire to the diode and resistor and another to the negative side.

The assembly is then wrapped in Kapton tape, ensuring there is no connection between the negative and positive terminals, and fix it into the loco.

At the other end I solder the wires to the corresponding solder pads on the decoder, ensuring there is enough wire to allow the decoder to be plugged back into the socket.

The decoder can then be plugged back in and the chassis is ready to go.

All three chassis have now been fitted with stay alive units and the bodies have been fitted, but you’ll need to wait until next week to hear what they sound like when I’ll also show you how to program the decoders so that each of the six Alco 251C prime movers sound slightly different.

Plugging it all Together With Anderson Powerpoles

In July of 2016 I shared with you how we join our modular layout, ‘Solent Summit’, together electrically using ‘Chock Blocks’.  You can find the post here.  Since then we’ve improved on this system by using Anderson Powerpole plugs.

The ‘Chock Blocks’ worked well for several years but the more we used the layout, and the larger it gets, we started to notice more and more that wires would get pulled out, the pins in the male sections would need spreading to ensure a good contact, and we were chasing electrical problems.

So we looked around for another solution.  There are several out there and they vary in design and price, but in the end we settled on Anderson Powerpole.  These are not the cheapest but the quality and reliability, so far, has been outstanding.  These have also been the standard connector for the NTRAK Modular Railroading Society since 2005.

There were three things that stood out to us, other than the quality of the product.  Firstly, the plugs are universal, which means there is no Male or Female sections, just one plug which connects to any other Powerpole.  Secondly, the plugs can be assembled in any order to make a connector to suit your needs; if you connect a wire to the wrong location you can simply move the Powerpole.  Thirdly, the Powerpole casings are the same size for the three different wire size fittings so you can easily combine different wire sizes.

The only disadvantage to the system, apart from the cost, is you need a special crimp tool, but that’s it.

The basic system looks like this; a crimp tool, plastic connectors and wire crimps.

The connectors come in a variety of colours.

The crimp tool is fairly large but very easy to use, as you’ll see later on.

The crimp connectors come in three sizes; 15 amp, 30 amp & 45 amp.  As we’re working with model railways 15 amp is more than sufficient, but we also have some of the 30 amp crimps simply because they are designed for larger wire.  Below are the 15 and 30 amp crimps.  The circular part is for the wire and the shaped section fits into the plastic connector.

For my new Tehachapi Loop modules I’ll be using the 15 amp crimps.  This orange wire needs to be linked across the two modules.

I strip the wire back by about the same length as the circular section on the crimp using a regular set of wire strippers and twist the ends together.  Twisting the ends ensures there are no stray strands.

The crimp tool has three positions, one for each crimp size.  The tool is ratcheted so it won’t spring open, allowing you to place the crimp in the jaws without it falling out.  The wire can then be placed into the crimp and the tool squeezed.  Once the tool reaches the right amount of compression on the crimp the ratchet releases and the tool opens up.  As I said before, it’s very easy to use.

The end of the wire is now crimped and is very securely fixed.

The plastic housing has a metal plate inside which the shaped section of the crimp pushes over.  Once it’s in it won’t pull back out; the cutaway image below (from Wikipedia) shows how it fits.

The plug can then be added to a plug block which can be assembled in any configuration.  Each plug has grooves on two sides and a raised section which fit into the grooves on the the other two sides.  And as I said before should you get one in the wrong place, one of the greens for example, it’s easy to slide them apart and correct the positioning.

To make unpacking and packing the modules quicker, as well as protecting the wires in transport, we’ve glued a singe Powerpole plug to the underside of the modules so the connector group can be secured.

The Powerpoles push together easily and hold well, but when you want to pull them apart it can be done without a lot of force.

As you can see they’re ideal for modular layouts.  In the main connector I have several small wires and the larger main bus wires, which use the 30amp crimps.

The Anderson Powerpoles are available from lots of places including Amazon and Ebay as is the crimp tool.  We have now converted all of our modules to this system and so far it has proved to be well worth it.

Alco C-855 N Scale ESU LokSound Install – Part 1

As well as being an iconic-looking locomotive the huge Alco C-855 also had an individual sound being powered by two Alco 16cyl 251C prime movers.  Together they developed 5,500 horse power and would’ve really rumbled as they passed by.  ESU have captured the right sounds and made them available for their V4.0 and new V5 LokSound decoders so in this post I’ll show you how I install sound into these locomotives.

Although the chassis has a step down section at the rear of the locomotive I wanted to add a good size speaker to ensure the sound has some bass to it.  The easiest solution is to cut a section out of the top chassis as you can see below.

Cutting the chassis just behind the inner screws leaves enough room for the speaker and provides a plastic shelf for it to sit on above the worm gear. The worm gear is below the top of the plastic so it won’t catch the speaker.  The chassis has already had parts cut out of the chassis making it lighter.  But given the sheer size of the locomotive, the fact that it pulls like a tractor anyway, and it will be running in a set of three, a little more removed will not be a problem.

The new Lokssound V5 micro sound decoder is a neat package and comes with a good 4 ohm speaker already attached and parts to assemble a speaker enclosure.  This chip came with an 8 pin plug, but as it will be hardwired in, the plug will be cut off.

Unlike the V4.0 Micro decoders which had different plugs soldered to the decoder all the V5 decoders are actually the same.  Below you can see copper pads on top of the chip.  This is actually a removable part with a Next18 socket underneath.  Next18 means it has 18 wire connections.

The chip looks like this.  The six copper solder pads next to the plug are for auxillary functions 5, 6 & 7 as well as stay alive connections.

The underside of the socket has no connections.

The flexible cable can be cut off leaving the socket section and copper solder pads.  The pads include track power positive & negative, motor positive & negative, speaker positive & negative, front & rear headlights, auxillary 1 & 2 and the common positive.

I will be mounting the decoder at the front of the locomotive behind the cab.  There are two ideal power fixing points to connect to.  Bridge wires will also need to be run to the corresponding screws at the rear of the chassis because the glue used to extend the chassis isolates the parts.  See the previous post about fitting a decoder to read more about this, which can be found here.

The original chassis came with a light bulb for the headlight which was attached to the screws via a contact plate.  But as this will need four connections, and I’ve lost the original plates, it’s easy to make some more.  For this I tend to use the excess solid core wire from a resistor, as shown below.

I wrap the wire around the screw.

Solder the ends together.

Cut off the rest of the wire and it’s ready to go.

The one screw which is sunken into the chassis, behind the one with the new contact, can’t be modified in the same way.  For this one I simply strip off enough insulation from the wire and wrap it around the screw twice.  Then as the screw is tightened down it grips the wire.  Make sure you wrap the wire clockwise so as the screw is tightened it doesn’t undo the wire.

With all the connections soldered to the pads the socket can be seated into the area behind the front screw.  But as the chassis is metal it will short out on all the solder pads, so cover the area with Kapton tape first.

The socket can then be put in place and the wires taped down.  Remember to set the wires in the middle of the chassis otherwise the shell will not seat properly.

One thing to note is the decoder will be sat directly above the screws which are delivering track power so the decoder should also be wrapped in Kapton tape, except for the Next18 plug.

The ESU speaker enclosure comes in four parts.  A base, two thin sections and one thick allowing different heights to be made.  Even with the chassis cut down one of the thin sections will need to be left out.  I use superglue to fix the enclosure together and to the speaker frame, ensuring not to get any on the actual speaker.

The assembled speaker can then be placed at the rear of the chassis with the wire connections at the top facing forwards.

The top of the speaker is just about in line with the top of the decoder which sits just under the roof line of the shell.

You may have also noticed the brown wires from the decoder socket were not quite long enough.  I could’ve replaced them but it was just as easy to extend them, covering the joint with heat shrink. If you’ve never worked with heat shrink before I did a ‘how-to’ on it which can be found here.

With the decoder plugged in the chassis is now ready for its trucks and then testing.  This particular chassis is for a C-855 B unit so I haven’t added any headlights, but both the C-855 A units will have lights, so I added wires from the socket and included a resistor which is tucked under the front of the decoder.  Below you can see all three chassis ready to be fitted to their respective shells.

The chassis have been tested and sound very good but installing the shells will add an extra level of resonance, increasing the volume. Once they are totally finished and fitted I’ll share a video with you so you can hear all six Alco 251C prime movers running.

Choosing The Right Speaker For Your Sound Decoder

This week I have a ‘how to’ post to share with you about speakers and the importance of choosing the right one.

Sometimes I get locomotives in for repair which have been fitted with a DCC sound decoder and the sound simply doesn’t work.  There are several reasons for this and hopefully it’s something simple like a broken wire.  But sometimes the wrong speaker has been used and it’s damaged the decoder beyond repair.

Most manufactures supply speakers with their decoders, but as they often don’t know what you intend to fit it in, the speaker is a generic size, and in N scale this is never going to fit.  There are all sorts of sizes available as well as shapes as you can see below from this selection I had in my bits box.

Two of these speakers are supplied with ESU V4.0 decoders, the smaller speaker comes with the V4.0 Micro.  However, both are fairly large and it can be struggle to find room for them in many locomotives.  So they are often swapped for smaller speakers.  These then become available to be used with other decoders, after all they’re good speakers, but now there’s a potential problem which could damage the decoder, because they may not be compatible.

Speakers are measured in wattage, this is how much power they can handle, and impedance, which is the property of a speaker that restricts the flow of electrical current through it.  This is measured in Ohms.  If you put too many watts through a speaker, you normally just blow the speaker.  But if the impedance of the speaker is too low then more power is used in the amplifier than sent to the speaker and the amplifier over heats and blows.  The amplifiers on DCC sound decoders are ‘solid state’ which means they are made from electrical components only, no form of valves or vacuum tubes as you used to get in guitar and stereo amplifiers, but given how small the sound decoders are that is not surprising.  But this means there really is no tolerance for getting the impedance wrong.

Some speakers, such as the ones used by ESU with their V4.0 decoders have both values written on the back; 1.5w and 4Ohms.

If this speaker was used with a standard Digitrx, Zimo or Hornby TTS sound decoder it would blow the amplifier right away as these decoders are normally only rated at 8 Ohms.  The lower the Ohm value the more power runs through the amplifier.

All sound decoder manufactures should list, either in the decoder manual or on their website, what the max Ohm value is for their product.  But what if you have a speaker and you don’t know what the Ohm value is?  This can easily be measured with a multi meter which can read Ohms.  Below you can see I have the multi meter set to read up to 200 Ohms and when connected to the ESU speaker it is reading 4.3 Ohms.

So now you can select the right speaker to go with your sound decoder.  But going with the smallest isn’t always the best idea.  Normally the smaller the speaker the quieter it gets and it will have less bass.  One of the best ways to increase the volume and bass, without electric amplification, is to add a chamber to the speaker for the sound to reverberate in.  Putting a speaker inside a locomotive shell will do this naturally as the shell forms a box.  But the shell will not be airtight and as a speaker makes noise by pushing air the increase in sound will be small as the air escapes.  Adding a chamber directly to the speaker is the best way and the ESU speaker I measured earlier has just this.  The speaker clips into the box.  But due to the screw holes in the speaker plate and the wire holes it still isn’t airtight.

Digitrax supply their N Scale speakers with a pull-off strip which leaves a sticky surface around the speaker.  It can then be stuck to the chassis or inside of the shell.  But this doesn’t leave a lot of air for the speaker to push against.

I like to use cell phone speakers for my N scale locomotives as cell phones can be very loud!  Below is a Zimo sound decoder with a 8 Ohm speaker.  When soldering the wires onto your speaker remember that a speaker has a large magnet in it so as the soldering iron gets close make sure to hold the speaker down so it doesn’t jump up and attached itself to the iron.  They tend to get very hold and melt very quickly; don’t ask me how I know this!

In cell phones the speaker normally sits over a cavity and is stuck on to form an airtight box.  This is why some phones sound very loud and appear to have good bass.  I 3D print boxes to go with the speakers in different depths depending on how much room I have to work with.

This particular sound decoder is going into an old Rivarossi Challenger and that has lots of room in the tender so I’ll be using the larger box.

I use superglue to fix the speaker but it’s important not to get any on the actual speaker.  So, using the speaker bag, I put some superglue down and rub the box in it ensuring I get some glue on all sides.

Then I place the box onto the speaker and hold it till the glue sets.  Being superglue this doesn’t take long.

The speaker is now ready to fit into the tender and it will be considerably louder than any of the speakers in the first picture.

The thing to remember is to check the impedance.  Most new decoders now support 8 Ohm speakers, ESU going up to 4 Ohm. But a lot of older decoders, even ESU, may be 32 or even 100 Ohm only.

If anybody is interested in 3D printed speaker enclosures or cell phone speakers please get in touch via the contact page.