New Windows For a M.C.W. Orion Double Decker Bus

Not all of the parts I make are for trains.  This week’s post is about an English double decker bus, although they do tend to be used on model railway layouts a lot.

The M.C.W Orion Bus is an iconic English vehicle.  It came in all sorts of colors and was used all over the country for many years, so naturally it’s popular with a lot of modelers.  The model I’m making the parts for is a OO/HO scale bus.

OO Orion Bus Window 1

OO Orion Bus Window 2

One detail from this model which modelers often want to change is the sliding window vents which are normally on every other window.  In the pictures above and below you can see the thin line formed in the window plastic used to represent this detail.

OO Orion Bus Window 3

In the photo in this link of a real bus you can see these sliding window vents are very prominent, so you can see why modelers want to make them stand out on their models.

In order to recreate this look there are two common options available.  The first, as pictured below, is a white metal casting.

OO Orion Bus Window 4

The second option is an etched brass part.

OO Orion Bus Window 11

The trouble with the white metal parts is they are not uniform in size and often need to be filed down to fit, as you can see by the left hand window below.  Also, they do seem to be a bit too thick causing detail to be lost or simply appear overscale.

OO Orion Bus Window 6

The etched metal parts are very accurate but tend to be a bit too thin.  This causes them to disappear into the window the same way the original plastic molded line does.

OO Orion Bus Window 7

So ideally we need something with the thickness of the white metal but the accuracy of the etched metal.  It seemed like another perfect opportunity for 3D printing and that’s exactly what I did!  The parts below have been printed in Shapeways’ Frosted Ultra Detail material.  They are all the perfect shape and exactly the same.

OO Orion Bus Window 8

In a comparison close up you can see all three together.

OO Orion Bus Window 9

And the final test is with them placed in the actual model.  They all fitted perfectly and, once painted, will look fantastic on the bus.

OO Orion Bus Window 10

These parts are available here in packs of 15.

Next week I’ll share with you some real steam locomotives as I’ll be visiting one of England’s steam preservation societies, the Dean Forest Railway.

The Best Way to Weather My Stock

In last weeks post I promised to share with you some of my newly-weathered stock so that is exactly what I’m going to do.

I have a range of rolling stock from different manufacturers and a lot of the freight cars,  although they are very nice, some do seem a bit brightly coloured.  To be fair a lot of them would have been this way when they rolled out of the factory for the fist time.  But after spending some time of the rails everything gets dirty,  and even rusty as they get older.

I think they should look more like this.

Weathered Stock 11

Here are some closeups shots.

Weathered Stock 6

Weathered Stock 5

The next three where identical before weathering.

Weathered Stock 4

Weathered Stock 3

Weathered Stock 1Weathered Stock 7

Weathered Stock 2 As a comparison; below is a factory weathered freight car, on the left, alongside my weathered freight cars.

Weathered Stock 8

One of the things I didn’t like about the factory weathered freight car was the trucks, they look too shiny and new compared to the rest.

Weathered Stock 9

Below is a short video showing a train passing with regular stock followed by a train with the new weathered stock.

So how did I do this?  Well given that time is precious, as those waiting for projects to be draw will appreciate, I’ve found the best solution.  Get somebody else to do it!

These were all airbrushed by Model Railway Solutions. MRS provide all sorts of modeling solutions from flat pack baseboard construction, all the way up to complete model railways built to exhibition standards.

The weathering service is very reasonable and they are happy to work with large batch projects which can reduce the shipping costs when sending models from overseas.

Here are some of the other models that were on the work bench when I collected this batch.

This is an N gauge southern region Merchant Navy class locomotive.

Weathered Stock 14 Weathered Stock 15 Weathered Stock 16

This is a OO Gauge 9F made by Hornby.

Weathered Stock 17

Although the main body is dull and dirty the running gear looks wet and oily, these photos don’t do the locomotive justice.

Weathered Stock 18

Here is a BR Standard Class 4MT made by bachmann.

Weathered Stock 19 Weathered Stock 20

I liked the rusted areas around the tender water filling area.

Weathered Stock 21

The real coal in the tender was also added by MRS.

Weathered Stock 22

Coaches also get dirty and below is a OO Gauge collett coach made by Hornby which has also had the air brush treatment.

Weathered Stock 27

And to pull a train of these coaches, what could be better than a GWR Castle class. Again this OO gauge model was made by Hornby and is now in a typical representation of what it would have looked like when these engines where nearing the end of their life. Weathered Stock 29

Of course freight engines where not looked after anywhere near as well as the passenger locos.  Below is an image of a brand new OO Gauge Hornby 2-8-0.

Hornby 2-8-0

MRS spent some time on it and now it look like this.

Weathered Stock 23 Weathered Stock 24

It still runs as smooth as silk but in this condition you can just imagine it has seen many years of use.

Weathered Stock 25

MRS are happy to be contacted by phone or email and both can be found on there website.  Alternatively you can always drop me a message through my contact page and will be happy to talk to them for you.

Electric Motors and Measuring Stall Currents

Often when I am writing about fitting DCC decoders into locomotives I recommend checking the stall current of the motor.  This should be done to make sure the DCC decoder is up to the job.  However I don’t think I have ever fully explained what this means or how to do it so this week’s post will be about exactly that.

Although DCC system supply a form of alternating current, AC, to the track, the electric motor still runs on direct current, DC.  The DCC decoder will convert the AC into DC using a bridge rectifier and supply the correct amount of voltage to make the motor run at the desired speed.  The higher the voltage, the faster the motor runs.  But what about power?  Simply adding more volts alone will not make the locomotive pull a heavier train.  The answer is current. Every electrical device will draw a current which is measured in amps.

Without going too deep into the mathematics behind all of this, current can be explained in a simple equation: the current ‘I’ in amps (A) is equal to the voltage ‘V’ in volts (V) divided by the resistance ‘R’ in ohms (Ω):

Ohm's Law

So, for example, a train running at slow speed, light engine, will have little resistance and may pull 0.2 amp at 6 volts.  Add a heavy train and the motor now has a lot of resistance so it might pull 0.5 amp but still at 6 volts.  As the resistance is increased, adding more freight cars for example, the current draw will also increase until one of two things will happen.  Firstly, and most commonly with N Scale, the locomotive will start to wheel spin as the resistance, in this case friction, between the wheels and the track is weaker than the motor.  The current draw will drop off but the train won’t be going anywhere.  Secondly, the motor will stall.  This means that the motor will draw as much current as it can but simply cannot spin anymore because the train is too heavy and the friction between the wheels and rail is too great.  This might happen if you have good traction tires on your wheels or something gets stuck in the gears.  When a motor stalls like this the current draw will peak sometimes up to and over 1 amp and it’s this that can damage a decoder.

The electrical components in a DCC decoder are only designed to take a certain amount of amps through all the tiny wires and connections.  This is because high amperage draws cause a variety of issues, one is heat. This is normally dealt with by using bigger wires and components.

All DCC decoder manufacturers state what their decoders are capable of handling.  For example, below is the instruction manual for a Digitrax SDN136PS sound decoder; I put these into my C-855 locomotives.

DC Stall Test 1

The manual says the chip has a 1.0 Amp /2.0 Amp peak capacity.  This means that the normal operating current draw that this chip can sustain is 1.0 amp and for short periods it can sustain a peak of 2.0 amps. Anything over this will damage the decoder or cause it to shut down.

So how do you measure the stall current to see if your chosen decoder will work with your motor? Well, you’ll need some wire, a DC controller and one of these…

DC Stall Test 2

It’s a multi-meter.  It doesn’t have to be an expensive one; it simply has to have the ability to measure current up to at least 2 amps.  This particular one will measure up to 10 amps, so it will do nicely.  The red wire is plunged into the hole marked 10A and the black into the common.  The dial is rotated to the red 10A marker and you can see below it’s reading 0.00 amps.  It’s now ready to use.

DC Stall Test 3

I should point out – DO NOT do this with a locomotive that has a DCC decoder already installed as you may do damage to the decoder.

Using a section of spare track which is not connected to anything else, connect one wire from your DC controller to one rail.  Connect the other DC controller wire to the black multi-meter wire.  Lastly, connect the red multi-meter wire to the other rail.  Now when you put a locomotive on the track and run it up and down, the multi-meter will display the current the motor is drawing.  Normally with DC locomotives this will also include any current draw from lights as well.  Remember the max current draw of the decoder will be for everything, not just the motor.

The main reason for doing all this was to measure the stall current of the motor and to do that you will need to find a way to stop it spinning when it’s under full power, i.e. full throttle on your DC controller.  With N Scale this can often simply be done by removing the locomotive shell and stopping the motor with your fingers, although I would not recommend doing this with larger HO and O scale engines as they have some big motors!

With the motor ‘frozen’ between your fingers and the power on, the multi-meter should be reading the max current draw from the motor.  If this value is higher than the manufacturer recommends for the decoder then it will not be safe to use it.

Normally with N Scale locos the stall current is about 0.6 to 0.7 amps and with a few LEDs it may go up to 0.9.  Add sound and it could be up to 1.5 amps but as long as that is below the manufacturers specification than it’s still safe.

This has been useful when I’ve wanted to run two motors from one decoder. For example, my Bachmann F7s, which you can read about here.  They have two decoders for four locos.

Bacmann F7 DCC Install 36

Next week I’m going to share with you some of my newly-weathered stock, I just hope my photos do them justice!

A Difference in Gears

This week’s post is about a replacement gear set for my C-855 model.  In particular it’s for the very early Con-Cor U50 chassis and the difference it has with later models.

The Con-Cor U50 and Turbine chassis has a centered motor powering two drive shafts.  Each drive shaft has a cup gear on the end which looks like this.

Con Cor 4500-U50 Chassis Render 2

The motor has a small gear which fits inside the cup.

In the rendered image below you can see the two drive shafts either side of the motor.

Con Cor 4500-U50 Chassis Render 4

My C-855 locomotives required this chassis to be extended and therefore the drive shafts as well.  In the image below you can see the white drive shaft extenders inside the extended chassis.

Alco C-855 Chasses 2

Up close you can see the drive shaft extender is simply a cup gear that plugs into the existing gear.  The tooth set out is the same with twenty teeth in total

Alco C-855 Chasses 8

So far in all the U50 and Turbine chassis I have seen the cup gears have all been the same.  But last month I had an email from a fellow modeller who had a U50 chassis with different cup gears.  His had 26 teeth per gear.  So I searched through all the U50 chassis I had to hand and eventually found one as well.  It looks like the very first U50 batch were made by Sekisui on behalf of Kato and it is these models that have the different gears.  Both the Kato made and Con-Cor “Rail Baron” version have the same motor gear and cup gear.

So not wanting to let anybody down I have drawn a replacement cup gear extender.

Alco C-855 Extra Gear

The new cup gear is on the left and you can see the teeth are finer, and there are more of them.

Before I release this gear I want to do a test print and check that it really does fit the 26 tooth cup gear in the Sekisui chassis.  Then it will be available through the shop should you wish to convert your Sekisui U50 into a C-855.

Also while searching through all the chassis I noticed the gears in the trucks and worm gear are different between the Kato made chassis and Con-Cor “Rail Baron” versions so I would not recommend mixing up the trucks, I tried it and the loco run very lumpily indeed!