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.

Alco C-855 R-T-R Build – All Together

Happy New Year!

2019 is here and what better way to start than to see a project completed.  My C-855 Ready-To-Run set of N Scale A-B-A Alco C-855 locomotives have been a challenging build but fun to do and I think the outcome is very good. This set are now on their way to their new owner.

The complete How-To series for the build of this A-B-A set can be found here.

Looking forward I have some more projects which need to be wrapped up and the next big one is the Union Pacific Rotary Snow Plow 900081.

I also have some updates for the DD35 as well as several replacement parts to share with you once we get stuck into the year.

So for now it’s back to the digital drawing board and on with 2019.


Alco C-855 R-T-R Build – Part 13 – Handrails

This week I’m covering the next part of my step-by-step build of a set of N Scale A-B-A ready-to-run Alco C-855 locomotives.  You can find part one of the build here.  This step is all about adding the etched brass handrails and ladders.

The handrails on these locomotive run between the sand boxes which are fixed to the outside of the bodies. To make painting the sides of the shells easier the sand boxes are separate parts.  Each locomotive has eight sand boxes; four on each side.  The A units have two cranked sand boxes which fit behind the cab.  The other six are rectangular.  The B unit has eight identical rectangular sand boxes.

The red stripe was created with a decal and will be finished with paint.

Because both the shell and the sand box have been painted it may be a very tight fit, so you’ll certainly want to do a test fit before you attempt to glue them on.  On the rear of the sand box is a lug which fits into the slot on the side of the shell: if the sand box doesn’t fit it could be because of the paint around the lug and gentle scraping with a craft knife will remove this.

To fit the sand boxes I use a toothpick or similar to add a drop of superglue to the slot then press the sand box into place.

The sand boxes on the other side of the A unit are a mirror image.  (And yes the shell above is a different locomotive, number 61, to the one below, number 60).

The brass etch fret has six handrail sections to install as well as four ladders.

The center handrails, and the longest, have four posts which fit into the top of the sand boxes.  Both handrails are the same.

The sand boxes have square holes 3D printed in the tops to accept the handrails which not only makes it easier to get them in the right place but also makes them a lot stronger, as with the sun visor installation described in my previous post about detail parts.

However as the sand boxes have been painted it’s possible the square holes are blocked with paint.  If that’s the case they can be opened up with a 0.4mm drill in a pin vice as shown below.  No 3D printed material needs to be removed and a few twists should cut through any paint blocking the hole.

The handrail can then be test fitted.

As both ends of the handrail are fixed by the sand boxes you may find that the handrail bows which it has done in the image below.  This could be due to several reasons such as the sand boxes being slightly too close together or the 3D printed shell may have shrunk slightly which can happen if removed from the printer too quickly.  But it’s hardly noticeable except in the handrail. In this situation I remove the handrail, dab some superglue onto the four posts and fix them into the sand boxes.  Once the glue has set I use a pair of tweezers to increase the crank next to the sandbox which will stretch out the handrail and remove the bow.

The crank in the image above is rotated clockwise and the crank in the image below is rotated anticlockwise by the same amount.

Each of the eight posts in the center of the handrail can now be glued to the shell.  I do this by dabbing a small amount of superglue under the post with the toothpick and holding in place until set.  I tend to use a small flat blade watchmaker’s screwdriver to hold them down.  The posts or handrails for the ladders are not stuck down yet to allow correct positioning of the ladders.

The next sections to be fitted are the handrails behind the cabs; the B unit doesn’t have these.  There are two in the fret and they are both the same.

As with the center handrail this part has two posts which fit into the top of the front sandbox.  There is also a square notch in the side of the cab, level with the sun visor, which the end of the handrail fits into.  With the exception of the ladder handrail section this part is glued in place, again with small amounts of superglue dabbed on with a toothpick.

The last two section are for the rear of the locomotive.  Although both parts are the same shape they are different.  Below is the left-hand side handrail as viewed from the outside.

From the inside you can see two reduced sections which are bending points.  The first is just before the first crank on the left and the second is just before the second post from the left.

This section of railing fits into the top of the last sand box and the other three posts have square notches in the 3D printed shell to fit into.

The very end of the handrail fits inside the lifting lug and lines up with the short section of handrail that was fitted in my last post.

The front of the B unit has the similar handrails to the rear, the difference being they are slightly longer.  So if you test fit them and the posts don’t line up vertically with the notches you have the wrong end.

Now all of the handrails are installed I fit the shell to the chassis, remembering to locate the headlight and secure with some Black Tack as described in part 11 of this build.

I fit the shell to the chassis now because the next parts to be added are the ladders and these are probably the most delicate part of the model and will be protected, to some degree, by the chassis.

The ladders are all the same but on the rear are two reduced sections.  These are not bending points but rather locating points for the handrails.  In the image below the ladder on the right is showing the rear side.

To fit the ladders I dip the top in a spot of superglue and place onto the side of the shell.  There are two locating lugs 3D printed on the shell and the ladder sits on either side of them.

The handrails are then glued to the reduced section behind the ladder, but they can also be glued to the shell if you like.

There are a few other parts on the fret which were added to it not knowing if they were needed.  These are some Multiple Unit or MU hoses which could possibly be used on the pilots and two tiny pipes, L shaped, which were designed to go from the cylinder on the fuel tank to the pipe 3D printed on the shell.  But as the existing pilots have MU hose molded onto the original Con-Cor parts I’ve decided not to use them.  As for the tiny pipes; these would prevent the shell from being removed if installed and from experience they get knocked off so easily I’ve also decided to leave them off.  However they are there to be used if you wish.

As for the assembly of the A-B-A set, that’s now it.  I still need to do a little paint touch up.  I also want to add some blackening on the vents and grills and also the number boards need to be sorted out.  Next week I’ll have some proper photos and hopefully some video of the finished set but for now here are a few shots taken whilst their still on the work bench.

As I said, in next week’s post I’ll have some shots of the finished set to share with you.

Alco C-855 R-T-R Build – Part 12 – Detail Parts

This week I’m covering the next part of my step-by-step build of a set of N Scale A-B-A ready-to-run Alco C-855 locomotives, which are almost finished.  You can find part one of the build here.  This step is all about adding the last detail parts and putting it all together.

I will start with the fuel tank.  This screws to the underside of the chassis with the same screw which held the original Con-Cor fuel tank for the U50/Gas Turbine.

The new 3D printed chassis section is designed to accept the fuel tank in one direction only; there is a lug at the front and a hole at the back which lines up with the screw hole in the tank.

However it won’t fit without a little modification to the trucks.  The inner trucks have a bar and hook which the original fuel tank sat over.  This stopped the trucks from swinging out too far when you picked up the locomotive.  It had no effect on the running or tracking of the trucks.

But because the C-855 fuel tank is a different shape these hooks need to be cut off to allow it to fit properly.  In the image below you can see I’ve only cut off the vertical part of the hook as the horizontal section can still run into the C-855 fuel tank.  This will still help hold the truck place.  However, the truck can now swing out.  If you plan to leave the locomotive on a layout and not handle it much then this won’t be an issue but if you plan to regularly move the locomotive, for exhibiting at shows etc, the one option is to extend the horizontal section and I’ll show you this a bit later on.

The fuel tank simply fits on the metal motor chassis with the screw hole aligning with the hole in the plastic insert.  The insert was the piece which was fitted in part 4 of the build about the chassis assembly.

The insert is not threaded.  It could be threaded by using a thread cutting tool but as it’s plastic or rather acrylic and the screw is metal it will cut in with a little effort to get it started.

The fuel tank has two holes in the side which, when fitted, will align with two clips on the shell.  This holds the shell onto the chassis. ( I used a spare shell for the test fit as the painted one had just had its decals added).  To remove the shell simply spread the shell at the fuel tank and pull apart.

Earlier I spoke about lengthening the pegs on the trucks to stop them swinging out.  This can be done with anything you have eg. a strip of plastic or metal.  I used an off -cut from the etched fret border.  The left or front truck didn’t need to be extended but the rear did.  I simply superglued the brass to the existing peg.

With the fuel tank refitted the rear truck can no longer swing out.

Next we come to the crew.  These are modeled sat at the controls and include a platform with a grab handle on the underside for easy installation.

The two crew parts are designed with the engineer being offset to the middle of the locomotive.  The grab handle will be closest to the side of the shell.

Although I always spray my shells with a primer first, with these tiny details I simply paint them directly with paints using a small brush.  These areas are so small I don’t feel the primer will make much of a difference.  I tend to use Humbrol enamel paints as they are normally finer than acrylics and better for small details.  I know there can be an issue with using these paints on the 3D printed surfaces as they have been known to stay sticky for weeks but again for such small areas it appears to be okay.

I prefer the blue as a uniform color for my crew, it looks like denim and gives a traditional feel to the locomotive.

Inside the cab on either side are two shelves.  The crew parts will sit on top of these shelves.  The rear one has a step on top and this is the locating point to ensure the crew are put in the right place.

Using a pair of tweezers and holding the crew part upside down I test fit them first.  Sometimes if there’s some print residue on the shelf they can be a tight fit and the end of the crew platform part may need to be cut down ever so slightly.  I do this with the modeling knife.

Once I’m happy they’ll fit I dab the two ends of the crew platform with superglue and stick them in place.

The crew will now be visible through the windows.

The next details are from the etched metal fret.  To the right of the fret are two small grills.  These are walkways used at the rear of the locomotive.

I cut them out using a sharp knife.  In the close up below you can see two burrs on the left of the top walkway which will need to be trimmed so it’ll fit into the shell.  The walkways are handed, ie. they’re mirrored versions of each other, and the cranked face goes against the locomotive shell.

As always I do a test fit.  There are two notches for the walkway to drop into so the top is flush with the checker plate printed into the shell. After I’ve confirmed it fits I dab a spot of superglue on each end and place it back into the model.

It’s these small details like this that make the model come to life, but if I’d designed these to be a 3D printed part of the shell they would’ve been very chunky, if not solid.

The next detail from the fret is the long walkway which goes onto the roof over the center of the shell.  Again I cut it out with a knife and tidied up any burrs.

This walkway has a reduced section on each end which is designed to fit into a slot in the roof detail just past the large roof grill.  As the shell has been painted it is probable that this slot has some paint in it, as it does in the photo below, and will need to be carefully opened up with the knife. Take care that no shell material itself is cut away.

Test each end to see if the walkway slides in.  Once it does I spot, using a toothpick, a little superglue onto the areas where the walkway is supported, mainly the four raised strips, and a little on each of the reduced sections on the ends.  Then I fit the walkway.  Once one end is in it’ll need to be slightly bent, or curved, to get the other end in.  The walkway can be pushed down and it should stick to the four raised sections preventing the walkway from bowing back up where it was curved..

To the far right of the fret are two sunscreens for the cab.  These have tabs attached which fit into holes 3D printed in the cab sides.

The holes, above the windows, are already sloping up at the right angle so all you need to do, after a test fit, is dab some superglue onto the tabs and push them into place.

Again this is another detail which greatly improves the model.

The sun shades are not handed so either will fit on any side.

When I first started making etched sunscreens for my models, such as the DT6-6-2000, they were details which simply stuck to the sides and this made them weak.  Having the tabs running into the shell gives them lots of strength and helps prevent them being knocked off.

One of the smaller details is the rear hand railing.  The C-855B has one at the front as well.  This is a cranked section located in the middle of the fret.

It fits between the two lifting lugs at the rear (And at the front on the C-855B)

Believe it or not this is one of the most fiddly details to add!  (I blame the designer). There is a tiny shelf on the inside of each lifting post to receive the handrail and it can be really tricky to get it in.  Of course that might just be me!

The last detail is the horns.  This is 3D printed and can be a bit delicate.  I brush painted it with UP Harbor Mist Gray.

Located on the top of the shell is a hole to receive the peg in the underside of the horns.  When designing these locomotives, reference photos of the roof were very hard to find and I was unsure if the C-855B had horns or not.  So I’ve made allowances for them on the C-855B and leave it up to you to decide.

The last parts to add are the sand boxes and handrails which I’ve left till last as these are the most likely parts to be damaged when handling the model. I’ll cover installing all of those in next week’s post which should complete this build.

Alco C-855 R-T-R Build – Part 11 – Lights

This week I’m covering the next part of my step-by-step build of a set of N Scale A-B-A ready-to-run Alco C-855 locomotives, which are almost finished.  You can find part one of the build here.  This step is all about adding the headlights.

These models are going to be DCC, but the same installation will work with DC as well.  The C-855 has a pair of headlights above the cab windows centered in the roof as you can see in the image below.   These lights are very small and although you can get surface mount LED of a similar size its hard to get them to look as rounded as this, or rather as the real thing.

To achieve this effect I have designed the two lamp holes to be printed into the 3D shell but the holes only go halfway into the roof.  For the other half I have designed a larger hole which can only be seen from inside the cab.  In the image below of the upside down shell you can see the larger hole above, or rather below, the windows.  This image was taken before I fitted the windows.

The hole is designed to accept a ‘2mm Lighthouse Warm White LED’ as shown below.  I use these for several reasons. They’re fairly cheep, the spindle part or lighthouse section is small but the rest of the LED is not too small to easily work with.  The warm white light is much closer to the original than the stark white of standard LEDs and the lighthouse design can be used to make a beam of light rather than just an all round glow.

It is important to note that LEDs unlike bulbs only work when the positive and negative wires are connected in the right way.  LED stands for Light Emitting Diode.  A diode, light emitting or not, only allows DC power to pass through it in one direction.  So if the wires are connected the wrong way around, it simply won’t light up.

There are three ways to tell which is the positive terminal on a lighthouse LED.  Firstly, you can see above that one metal leg is longer than the other.  This is the positive leg.  Secondly, looking inside the LED as shown in close up below you can see the split between the two internal parts.  The smaller of the two, shown at the top, is the positive side.

And thirdly, if you have your power source handy such as a 9V battery or 12v DC controller you can touch the LED contacts to the wires and it will light up when connected the right way round.  NOTE: a resistor must be used when doing this otherwise the LED will most likely burn out. This is because the LED will only be able to handle a low amount of amperage and with out a resistor to limit the current the LED, will draw all the amperage the power source has available.  The resistor can be on either the positive or negative side, as long as the power passes through it.  I will show you how I place mine shortly.

Because the LED omits light from all sides it’s important to ensure we only get light where we want it.  If you have one of the older Con Cor Gas Turbines, which chassis we are using for this build, you may remember that when the headlight is on, the whole cab illuminates.  What doesn’t help is the FUD or rather ‘Fine Detail Plastic’ material Shapeways use is porous to light.  However these shells have been primed and painted which gives a good block to the light showing through but just to make sure I always paint the inside of the cabs with a matt black.

I doesn’t have to be a pretty job, but I like it to be thick.  I also make sure I get some in the hole where the LED fits, this bit doesn’t want to be too thick otherwise the LED won’t fit.  I used to paint the LED with the exception of the top of the lighthouse to prevent unwanted light but I now have a better method  I will share with you in a minute.

The legs on the LED need to be cut down so the LED fits into the cab roof area.  Make sure you leave enough to solder wires to.  At this point the first way of identifying the positive side of the LED is no longer possible, unless you cut one longer than the other.

The LED wont go all the way into the hole because half way in the big hole becomes the two smaller headlight holes.

To stop the light filling the cab I now wrap the LED in heat shrink.  I use a tube which is roughly the same size as the box part of the LED and cut it so it will cover everything except the tip of the LED that goes into the hole.  If this part has heat shrink on it will not fit into the hole.

The box is actual bigger than it looks and the heat shrink tube is a tight fit but with some effort can be forced over the LED.

Then using my soldering iron I can shrink the tube around the LED.

The only part of the LED which can’t be covered like this is the rear of the box between the wires.  So I simply paint that with black matt paint.  A pair of tweezers are an easy way to hold the LED while painting as they naturally clamp it.

Once the paint is dry, 15 minutes with the acrylic paint I use, the LED can be test fitted.  Ideally the heat shrink should go all the way to the edge of the hole to prevent any light showing through.

For the resistor I have used a  small 1k ohm.  Being only a 4mm long it will be easy to fit into the space in the top of the chassis.  I cover the electrical connections to prevent them from touching the chassis with another piece of heat shrink.

I have soldered the white wire from the decoder to the resistor, the white wire is the front light negative.  The blue is the common positive.

The heat shrink is then pushed over the resistor, shrunk on with the soldering iron and it’s all tucked into the space in front of the decoder.

The wires can then be soldered to the LED.  Don’t forget to check which is the positive connection first.  I also used two small pieces of heat shrink to cover the joints.

With all the connections made and covered, I did quick test on the power to make sure everything worked.

Because the shell may need to be removed for maintenance at a latter date I don’t glue the LED into the cab roof.  I use a bit of black tack to hold it in place.  This should hold it firm but it can be peeled off at any point.  Black Tack is a high strength adhesive putty designed for photographers. I find it fantastic at holding decoders and other bits in place.

The head lights are now ready for the proper test and as you can see they look really good.

If your running on DC then you still need to use the resistor.  The wires coming from the LED, via the resistor, simply need to be connected to the chassis power points.  One to the left hand side and one to the right.  In the image below, taken from part 5 about fitting DCC decoders, you can see the two contact point which will also be used to connect the motor to.

Because the LED will only light up when power is applied in the correct direction the LED should only light up when the chassis is running forwards, on DC power.  If it lights up when running backwards the wires need to be reversed.

These models have not been designed with a rear headlight, mainly because I intended mine to run as an A-B-A set.  Therefore the C-855B has no lighting.

As this post turned out to be a bit longer than anticipated, I will leave the detail parts such as the fuel tank and etched details, for next week’s post.

Alco C-855 R-T-R Build – Part 10 – Window Glazing & Wipers

This week I’m covering the next part of my step-by-step build of a set of N Scale A-B-A ready-to-run Alco C-855 locomotives.  You can find part one of the build here.  This step is window glazing and fitting window wipers.

Now that the decals have all been applied, with the exception of the number boards, I can sort out the window glazing.

This wasn’t done sooner as some of the paint needed to be finished by hand, such as the red lining over the front wwindows. I do this by hand as there are four holes for the windscreen wipers and it’s easier to paint the stripe than cover the holes with a decal and try to find them again.

If the glazing was fitted first there would be a risk of getting paint on it.

The glazing, only required for the C-855 A units, consists of 5 parts; a center section which covers the four forward windows, two side sections for the pairs of side windows and two door sections for the doors at the rear of the cab.  I cut my window glass from clear acrylic sheet.

The main section is 18mm long and 5mm deep.  The cut out at the bottom is 10.5mm long by 1mm deep; this is to avoid the chassis.  The side window sections are 6.5mm wide by 5.5mm deep. They are shown in the wrong orientation in the photo and fit into the cab turned by 90°.  The door sections are 3mm wide by 4.5mm deep.  These sizes are rough but allow the window hole to be totally covered giving enough space all around to fix the glazing in.  So if your slightly off it’s okay.

I tend to start with the main window section. As with anything like this I always do a test fit first.  With the shell resting so the nose is at the bottom I’m able to drop the window in using a pair of tweezers.  If it’s a good fit I take it out, but if it’s not a good fit I trim it down where needed and try again.

To fix the glazing I use a very small amount of superglue.  The reason I only want to use a tiny amount is because of the reaction superglue fumes have on fingerprints.  As much as I try not to I still get fingerprints all over the glazing, then, if a lot of superglue is used, the fumes stick to the prints and they show up on the glazing, turning it hazy.  So to prevent this I put a drop of glue onto a piece of card; something glossy is great so the superglue won’t soak in.

Then using a pin I put a dot of superglue in each corner of the windows, and as this is a set of four windows I also put one above and below the middle.  Then using the tweezers I place the glazing back in.  As the glazing and shell are made from acrylic and so is superglue they all bond quickly together with no fumes when the glazing drops into place.  In the picture below you can see the front glazing stuck in place.

This is then repeated for the side windows and rear doors.  As long as the glazing isn’t any bigger than the given dimensions it will not interfere with the fitting of the cabs and crew.  Once fitted the glazing gives a much better look to the cabs.

Now I can fit the windscreen wipers.  They are located in the etched brass fret on the right hand side, one for each of the front windows.

In the picture below I have cut out the right hand pair.  (Right hand as you are looking at the loco, not from the driver’s perspective).

About 1mm in from the left hand side of the arm is a half etch section on the rear of the etch; this is where the wiper arm needs to be bent in order to attach it to the shell.  I use a flat pair of tweezers to hold the wiper and push the arm over with my finger.  Because of the half etch the arm will bend in the right place.

Now I do a test fit.  The holes on the cab for the wipers are the right size and they should fit well but it is possible that the holes have filled with paint. If that’s the case a 0.5mm drill can be used to reopen the hole.

I use a pin vice for small drills like this.

With the holes open the arms can be test fitted; you can see the first arm test fitted below.

Once you are happy then it can be fixed in.  Again I use superglue for this but not applied directly to the model.  I put a fresh drop on to my piece of card and using the tweezers lightly dip the bent arm into the superglue then put it back into the hole.  You have a few seconds to position the arm where you want it before it sticks.  The main windows the engineers look out from are the deeper outer windows.

The C-855 shells are almost finished.  They still need the sand boxes adding, as well as the handrails, crew and a few other details such as the lights which I know a few readers are waiting to see how to do. This will all be covered in next week’s post.