Using Second Hand Capacitors

This week’s post will be a how-to for a question I get asked a lot.  Can I use second-hand Capacitors?

The reason I often get asked this is modelers often want to use second-hand capacitors to make StayAlive units for their DCC locomotives, and these can be very effective.  But where are they getting second-hand capacitors from?  Most electrical appliances have capacitors in them of one form or another.  A good example of this is an old stereo system I took apart for the motor.  Below you can see the main printed circuit board (PCB) and it has lots of black cylinders which are mostly all capacitors, and ideally sized to fit into small locomotives.

Even the smaller secondary PCBs have capacitors on them.

The main power input board below is a bridge rectifier, the smaller black cylinders are diodes, and it turns AC voltage into DC for the stereo to use, the nice big capacitor is there to smooth out the DC.

These capacitors are all soldered onto the PCB.  With a good soldering iron the capacitor can be removed without damage by heating the two soldered joints, once you have figured out which ones they are, and pulling the capacitor out. 

This capacitor has a working voltage of 24v and a capacity of 1000 microfarads.  The voltage is important because it needs to be higher than the voltage in the DCC locomotive decoder.  This normally does not exceed 16v, so a capacitor like this is ideal. 

But I find the more important question is not whether second had capacitors can be used, its do the work?  Luckily there is a simple test to check this without any expensive equipment.  Some high-end multimeters have the ability to test capacitance but most do not.  Mine does not, but what it can do is test voltage and resistance.

One thing to do before the test is to remove the charge from the capacitor, a full capacitor could damage the multimeter.  This can be done with a metal screwdriver by shorting across the two terminals.  Please note, this is okay for small capacitors in the Microfarad range used in modeling, I would not recommend doing this with large capacity capacitors with capacitance measured in farads!

The two settings I use are both on the left of my multimeter.  Below it is set to 200k ohms and is used for testing resistance.  I will also be rotating the dial clockwise by three positions to 2 which is a DC voltage measurement.

The way this works is first you discharge the capacitor.  Then, with the multimeter set to resistance, connect the probes to the capacitor.  Black negative to the capacitor negative and red positive to capacitor positive.  The capacitor negative is normally clearly marked.  As the multimeter has a battery inside when the probes are connected to the capacitor it will start to draw and store power.  As the stored power increases the resistance will increase so on the display you will see a steady increase in resistance from 0 to infinity.  If there are any big surges or erratic readings, then the capacitor is not working.

The second part of the test is to set the multimeter to volts DC and reconnect the probes.  This will measure the stored voltage and you will see it decease as the capacitor discharges through the multimeter.  Again this should be smooth.

As it happens the capacitor I took out of the stereo was faulty, probably one of the several reasons it didn’t work!

But to show you the principle, I created a short video of me testing a new capacitor.

So the answer to the question “Can I use second-hand Capacitors” is yes, but I would recommend testing them before spending any time wiring them into your locomotives.

If you have a similar question you would like to be answered or explained in more detail, please contact me and maybe I can help.

A New Drive Gear For an OO Airfix Class 14xx

This week I have another replacement part to share with you.  As with most of my replacement parts, this was a request from a customer who has one of these locomotives with a damaged part.

The Airfix class 14xx 0-4-2 model has been around since the 1970s, and was a mainstay on many UK model railways as they were the only maker of the model.  It’s had several upgrades over the years as the model moved to Dapol and then to Hornby but the original can still be seen running today.

However, constant use over time will always cause parts to wear out and with the 14xx it’s the main drive gear that starts to go.   The original chassis had a thicker gear which can be seen at the top in the image below.  The thinner gear is for one of the newer chassis introduced under the Dapol line.  Interestingly Daopol also moved the traction tire to the other wheelset.

The metal worm gear on the end of the drive shaft drives sits directly over the main axel drive gear and the metal eventually wears down the plastic gear, especially if the wheels get jammed up or start to bind, due to lack of lubrication.

The gear in the image below is still in good condition, but you can see the teeth are intentionally not square to the axle.  This makes the mesh between the two gears smoother and improves the running of the loco.

Using the original I was able to 3D model a replacement.  Because the gear is thick, 3.18mm, it should be strong and hard when printed in Shapeways Smooth Fine Detail material.

The test prints came out very well and were immediately ready to use.  The hole in the center has been printed slightly smaller than the axel size to ensure a good tight fit.  If it’s too loose the gear will spin on the axel. If it’s too tight the new gear may crack. To allow for any 3D print shrinkage or oversize on the axel, I’ve 3D printed two gears; one has an even smaller hole to allow for any differences mentioned above.  It’s always easier to remove material if it’s too tight than it is to add some!

To identify the two different gears I’ve marked the side of the gear with the smaller axel hole with a hole in the sidewall as you can see on the gear on the right.

The replacement pair of gears for the Airfix OO 14xx are available using the link here.

As long as I can find an original gear, even if it’s cracked or damaged, I can replicate it using 3D printing, so contact me if you’re in need of a new gear that you can’t get hold of.

Next week I hope to have some more to share with you on the HO DT6-6-2000 project, the brass etches are in production, and the different variants of body shells are being drawn.

A Personal Post

This week’s post is a little different, it’s not even about trains!  It’s about something my partner and I do each year to help a very good cause which is relevant to a lot of people in this hobby.

This coming Sunday we’ll be riding our motorcycles in one of the most important events in our yearly calendar – The Distinguished Gentleman’s Ride.

Those of you who’ve known me for a while know we like to try and combine overseas travel with our yearly fundraising ride, but this year we’ll be riding in the UK again given the travel issues.

Despite the situations created by the pandemic the world over, as motorcyclists around the globe we’ll still come together as a community to raise money and awareness for men’s health.  Instead of the usual organized group rides we’ll be riding solo to support the cause.

The Distinguished Gentleman’s Ride raises funds for research and awareness of prostate cancer, as well as providing programs for men suffering from mental health issues, creating resources to break down the barriers for men to talk and deal with their mental health issues, in the hope of reducing the number of suicides. We support the cause by dressing dapper for the ride and, usually in groups, we put on a fantastic show for the public in whatever city we chose to ride in. It really is a day of celebration and joy designed to bring to the forefront men’s health. This year folks will be riding and fundraising, just solo.

If this is a cause you feel is important to you I’m asking you to make a small donation to do something to help stop men dying from prostate cancer, or by losing their lives to mental health issues.

Understandably a lot of people are experiencing challenging times because of the pandemic, but if you are in a position to make a small donation, please do. The link is here – https://www.gentlemansride.com/rider/thedrawnstudio

If you are not in a position to make a donation you can still help – drop a message to a male friend you haven’t spoken to for a while, and just ask them how they’re doing.  Our hobby is largely a social one, and with so many modelers having to shield through these difficult times it’s easy to get cut off and isolated, so let’s just keep checking on each other. There’s some handy guides on the DGR link here – https://www.gentlemansride.com/about/mens-health, so have a read, and reach out to someone who may need a lifeline right now.

Thank you.

Next week I’ll have a train-related post for you, once I get back from the ride.

A Cover for an In-Track RFID Reader

Model railways have seen many great technological improvements through the years and Digital Command Control (DCC) is one of the biggest, but sometimes I get asked to work on something that’s totally new.  This week I have a small project to share with you for a customer who’s experimenting with RFID.

RFID stands for Radio Frequency Identification and is used in all sorts of things; there’s a good chance you have an RFID chip in your wallet.  Bank cards that have the contactless payment option have an RFID chip inside the card which reacts to the RFID reader when you hold your card up to pay.  This technology has been in use for a long time in all sorts of industries, from such environments as warehouse management to automatic bridge toll devices.  Now it’s making its way into model railways, at least on one model railway anyway.

To add another level of realism to the customer’s railway, all of his freight wagons have been fitted with an RFID chip.  There are readers either under the track or within it at multiple places around the railway.  This means, when a train enters a freight yard, the computer will know exactly which wagons make up that train.  It’ll then work out where each needs to go, such as a local industry or added to another train, and the operator then has the fun of shunting the train as instructed.

With a newly-constructed part of the layout, adding a readily available RFID reader under the track was fairly easy, but on the already existing section it’s a little bit more of a challenge without ripping up the track.  The answer came in the form of these custom made RFID readers by Eccel.

This are designed to fit between the rails allowing space for the wheel flange to pass.  A hole at one end needs to be driled between the sleepers to allow the cable to pass through. However, they don’t look very realistic for a model railway, so the customer has asked me to design a 3D printed cover to make them look like a timber uncoupling ramp.  The uncoupling ramp below, made by Peco, is designed to clip into the track, but also sits above the railhead so it will engage the UK-style couplings.

The customer uses American-style Kadee couplings so the uncoupling ramp will be purely cosmetic and needs to sit just below the railhead.

As always, I have 3D modeled the original part, and some track, to ensure everything is correct.

The ramp is designed to clip over the RFID board, with space inside to allow for the circuit components.  The RFID reader itself will be fixed using the two holes in the board.

To get the wood grain effect I’ve recessed the patten so it will, hopefully, print and be visible when painted.  I’ll spray these to ensure a thin coat of paint as brushing would probably fill the recessed wood pattern.

Although this a simple project it’s been very interesting to do and I’m eager to see them in use on the layout.  Once they’re all printed and installed I’ll take some video of the trains running, and the computer screen capturing the RFID data.  This may be several weeks away, but I’ll share it with you when I can.

If you have something different like this on your layout that needs a special part, get in touch, I may be able to help.

Replacement Bachmann N Scale Chassis Fasteners & Washers

In February of this year, I shared with you my design for a replacement set of Bachmann OO Chassis Fasteners & Washers; you can find the post here.  Since then I’ve had some requests to do the same thing for the N Scale Bachman US locos. So in this week’s post, I’ll share with you my design for a replacement set.

Unlike the OO set, Bachmann still has the N Scale version listed on their website as spare parts, but they’ve been out of stock for some time. The fasteners in question are used in the older locomotive designs from the 1980s.  A typical example of this is Bachmann’s GP50 as shown below.

The chassis is a split frame design also used in several other locomotives, such as their GP40 and U36B models.  It’s held together by the two chassis fasteners at the bottom corners of the chassis.

Viewed from the other side you can see the screw heads which pull the fasteners tight.

With the screws removed, the chassis separates and the trucks and motor will drop out.  You can see the fasteners and a washer still in the upper chassis section.

The fasteners will push out and the washer will drop off.

Both the fastener and washer are made of plastic to electrically isolate the two chassis halves.  The washer also acts as a spacer to correctly position the chassis halves.

As with the original OO versions, with time the type of plastic used hardens and becomes brittle, so when the screw is removed the cylinder part of the fastening breaks off of the rectangular sections as shown below.

Interestingly the OO and N Scale versions at first glance appear to be the same, but after doing some measuring I discovered the N Scale fastener is shorter and fatter.  This means the N Sale washer also has a larger hole.  Below you can see my OO fasteners and washers in white compared to an N Scale original one in black.

Using one from the GP50, it was easy to modify the existing OO version to create a new fastener for repairing N Scale Bachmann locomotives which have suffered from this part failure.

As with the OO set, the hole in the middle of the tube section will need to be cleaned out to remove the 3D print residue before the screw can be inserted.  For the N Scale fasteners, I use a 0.8mm drill bit in a pin vice.

The inside of the tube has not been threaded for the metal screw so it’ll work as a self-tapping screw, cutting its own thread the first time it’s inserted.  But if the tube is blocked, the excess material will create too much pressure and the tube may crack.

These replacement fasteners and washers can be used on a large variety of Bachmann N Scale locomotives and I’ve made them available in a set of 6 here and a set of 12 here.  I thought it best to make the smaller set start at 6 so you have a few spares just in case something goes wrong.

These little fixes are ideal for 3D printing components, so if you have an idea for a part you’d like to see 3D printed please drop me a message, I’m always interested to hear what fellow modelers are working on. You can get in touch through the contact page.

A Baldwin DT6-6-2000 in HO – Brass Additions Part 13

Over the last two weeks, I’ve been working on the brass Additions to accompany the 3D printed parts of the HO Baldwin DT6-6-2000 and I’ve just finished them, so this week I’ll share with you how they look on their etched fret and where they go on the model.

The fret will be etched from 0.5mm (0.0196″) brass with a lot of the finer details reduced to 0.25mm (0.0098″).  The 0.5mm was selected as it’ll make the handrails roughly 44mm wide at the scale of 1:1, which is ideal.

The main four handrails are in the top left of the fret.  The shell has 3D printed mounting holes and locating marks to ensure these are installed at the right level.  In the top right are the two end handrails which again fit into 3D printed holes in the shell.

Below the end handrails are the sun shades or visors which slide into sloping holes in the shell.  Not all the DT6-6-2000 locomotives had these so I’ll offer both a shell with mounting holes and one without. Further down the etch are all the grab irons and the tiny windscreen wipers.  Again, all of these parts fit into 3D printed holes in the shell.  Some of the grab irons have tiny half-etched marks on the rear, allowing them to be bent at 90° in the right place.

Another part which will only be used on Pennsylvania Railroad versions are the antenna for the Pennsy train phone.  Again, a different shell option will be offered with the slots in the roof for the antenna to drop into.

With all the parts listed so far, the shell will look like this with the exception of the grills, which I’ll come to later.

At the bottom of the etch fret are 16 parts that form the window boxes which were found on several locomotives, such as the Minneapolis, Northfield, and Southern Railway’s No 21, and later Elgin, Joliet, and Eastern Railway models.

The etched parts form the sill, roof, and sides and I’ve allowed space for glazing to be fitted, just like the other windows in the loco.  Because the brass parts slide together, I’ve designed them so the inner two windows can be opened, just like the real loco.

The fixing for the brass window box is different, and the original window is removed, so this will be a fourth option that I’ll make available.

The last etch part I’d been planning was the grill mesh on the front of the nose. To get such a tight mesh it would’ve needed to be etched on a thinner sheet of brass.

A 0.2mm (0.0078″) sheet with half etching would’ve given this effect shown below.

Up til now I thought I’d solved the problem of the mesh design. However, upon doing some more research I found this really high-quality image of MN&S No 21 taken by Mike Roth on Flicker.  You can see the original here.

Zooming in on the picture, which I haven’t been able to do this closely on all the old photos I have, I can now see it’s not a grill mesh at all but an actual radiator.

With my original N scale version, even though I thought it was a grill, I modeled it as a flat surface recessed into the shell.  Once painted, it looked great.  So I think the same thing will happen here and the etched mesh will be removed.  My test print has the hole for the mesh but that can easily be filled with plastic card.

These etched frets are much bigger than my previous ones, not just because they are HO, but there’s more on them so they’ll be more expensive. The tools are the expensive part, and can’t be changed, that’s why I put the parts for different versions on one fret as it would cost too much to make several different ones. The price will be £10 GBP and I’ll be looking for some pre-orders to help cover the cost of getting the etch tool made. If you’d like to be one of those pre-orders please drop me an email at jamestrainparts@yahoo.co.uk or get in touch via the contacts page.

Once I get the first set I can test fit all the parts, make any adjustments to the 3D model, and then make all the different versions available.  The brass etches for the Baldwin RT-624 will be different because the handrails and end rails are a different shape.  But I’ll come to that later when I convert the DT6-6-2000 3D model into the RT-624.