An Alco C-855 for N Scale

In this weeks post I will share with you the first N Scale 3D printed Alco C-855 and all the accompanied parts.  If you want to read more about the history of this project click here and it will open a new page listing all my posts about it.

This model has been in the pipeline for a few years, so as you can imagine, I was very excited when last week the first test print arrived from Shapeways, and I must say I am very pleased with it.  Below you can see all the parts as Shapeways delivered them.

Alco C-855 First Print 1

At the back is the main shell; all in one piece.  The eight parts in front and to the left are the sand boxes, which fix onto the sides.  Each sand box has a locating peg which fixes into a hole on the side of the shell.  Next to the sand boxes are the crew and control consoles for the cab interior.  Below the two crew is a square plug which acts as a screw mount for holding the fuel tank on.  Next to the crew are the horns, these again have a simple peg which fixes into a hole in the shell.  The fuel tank is next to the horns and the two round parts are the drive shaft extenders.  The final two parts at the bottom are the 3D printed stainless steel chassis extenders.  The plastic parts have been printed in Shapeways’ Frosted Ultra Detail.  Although the Frosted Extreme Detail has a smaller layer thickness than FUD giving an even better finish, this was a test print and I wanted to see how it would come out before going to the best quality.  But even in FUD the details are clear and smooth and I will be very happy with this as an actual model.  Here are some close-ups of some of the detail

Alco C-855 First Print 2 Alco C-855 First Print 3

As normal with parts printed in FUD or FXD they need to be cleaned to remove the waxy residue, so after a rinse of in warm soapy water they spent 24 hours submerged in Goo Gone.

While the parts where getting cleaned I prepared another chassis.  I already had one extended chassis but as I have made some improvements to the chassis extenders I wanted to make up another.  As I have already covered this procedure in a previous post, which can be found here, I will only show the differences today.  I will be making a downloadable PDF available with full instructions soon.

As before I started with a standard Con-Cor U50/Turbine chassis.

Alco C-855 First Print 4

The new  chassis extenders have been tweaked in several places but the most obvious is the introduction of a forward arrow on both parts, this should help with orientation in the chassis.

Alco C-855 First Print 5 Alco C-855 First Print 6

The top section should be done first.  And this simply means removed the section highlighted below.  I used a cutting disc in a Dremel type tool.

Alco C-855 First Print 7The three parts where then glued together.  The key is to make sure the dog leg part of the chassis extender is flush with the underside of the remaining parts.  There should be a small gap at the location where you made the cut.  That way the chassis will be the correct length and it will be easer to keep it square.

Alco C-855 First Print 8

Unlike last time, I also need to make some cuts at the front because the body of the locomotive is narrow below of the cab.  The two wings need to be cut off as shown below.

Alco C-855 First Print 9

Also two notches need to be made.  I will give the sizes of these in the downloadable PDF.  The top notch ended up a bit larger than I had hoped because of the screw hole.  You could simply cut it all off but I want to keep as much weight as possible.

Alco C-855 First Print 10

As I pointed out earlier there is a plastic square plug used to screw in the fuel tank.

Alco C-855 First Print 11

This simply fits into the square hole in the bottom chassis extender.

Alco C-855 First Print 12

It will be held in by the motor and when you screw on the fuel tank, using the same screw from the U50/Turbine fuel tank, it will pull tight.

Alco C-855 First Print 13

With the bottom chassis section it is important to cut it as close to the parts that hang down as possible.  Other wise you may end up with a gap in the chassis frame. Indicated below is the section to be removed.

Alco C-855 First Print 14

Once fully assembled it should look like this.

Alco C-855 First Print 15

My C-855s will be DCC so I have installed a decoder in the space at the rear of the locomotive.

Alco C-855 First Print 16

The next step was to test fit the shell.  In the photo above you can see a square hole at the front of the fuel tank.  Inside the shell is a tapered peg so as the shell slides onto the chassis the shell will spread untill the peg pops into the hole holding it tight.

Alco C-855 First Print 17

The shell is nice fit and once the pegs locate into the fuel tank you can comfortably pick it up by the shell and it wont fall apart.

One of the identifying details on the C-855 is the large sand boxes on the side and because of the locating pegs these can easily be clipped into place.  I have made them a separate part to make it easer to paint the model.  In the photo below they are not glued in place but simple press fitted.

Alco C-855 First Print 18

But as great as the loco now looks there are still lots of parts missing.  And today I took delivery of the first batch of etched brass Additions for this loco.

Alco C-855 First Print 19

As I am going to paint the loco a lot of the parts are not ready to go on yet, plus I only got them today, but to give you and idea of what the finished loco will look like here are some picture with some of the brass Additions loosely fitted.

Alco C-855 First Print 20

Because just about all the brass Additions have mounting holes or slots they should be very easy to install.  The handrails drop into the top of the sand boxes which makes them easy to align.  There are a lot more parts to be added and some, like the ladders, can’t be shown yet as the handrails need to be fixed properly first but as you can see from the image below even the windscreen wipers have mounting holes.  It has swung to its natural hanging position but once glued in, it will line up with the left of the window frame.

Alco C-855 First Print 21

I want to do a few checks to make sure everything is where it should be for all the brass Additions and then the shell will be made available on Shapeways. I think that will happen in the next few days.  The chassis extenders are available now and can be ordered in sets of one, two or three by clicking on the links below.

Set of one C-855 chassis extenders.

Set of two C-855 chassis extenders.

Set of three C-855 chassis extenders.

There is an option to print the chassis extenders in WS&F and FUD which are both cheaper than the stainless steel but you will lose a lot of weight and please note: I have not tested them in these materials.

Although I normally post on a Monday I will do an extra post this week to let you know when the C-855 body and parts are ready as I know several of you are keen to get them.  If you order the chassis extenders now you can add the shell to your order at Shapeways without paying for shipping twice, as long as you do it in good time.  I also have brass Additions in stock, these are £6 GBP each.  Please contact me though contact page or email me if you would like to order some.

The next step, apart from painting and finishing the C-855, is to finish drawing the C-855B.  The chassis will be exactly the same so the extenders will be need for that too.  I will also be drawing a dummy chassis for both locos and will be sharing that with you soon.

A List of How Tos

This week’s post will be nice and short as I have just returned from the wonderful Brighton Modelworld show. We took our whole modular layout ‘Solent Summit’ and after three days of manning our exhibit I must say I’m a bit worn out.

One thing I did bring back from the show was the need to add another page to my website.  A lot of people wanted to know how we created our rock faces, or how we got locomotives to work in certain ways.  As I have already written about some of these topics I have decided to add a ‘How Tos’ page to the gallery which will list all the topics I have covered so far.  The posts under this heading will only be the ones where the focus of the post is how to do something, so any posts where I am simply sharing with you the results will not be included.  As I write more ‘How Tos’ they will be added to this page.

You can find the page here or by selecting the gallery page in the drop down menu above.

The Brighton Modelworld event was a fantastic show but as I was so busy running the layout for three days I didn’t get any pictures of it.  However I did manage to capture three videos of my trains running on the layout.

First we have the Southern Pacific Overnight express powered by four black widow F7s.  These are the ones I wrote about in my ‘How Tos’ post ‘Converting An N Scale Bachmann F7 to DCC’.  The train is crossing the river Warsash on the Warsah Wye trestle.

Secondly we have the Southern Pacific Sunset Limited also crossing the Warshah Wye trestle.  The three Alco PA’s have the assistance of a 4-6-4 steamer as the train battles the grade.

And thirdly we have a pair of Santa Fe DT6-6-2000 transfer locomotives working a train of perishable box cars through New Mills on their way to the SF East End yard.

In next week’s post I will be getting back to 3D printed products and sharing with you the first 3D printed N Scale Alco C-855.

Replacing Con-Cor U50, Turbine & JTP C-855 Wheelsets

This week’s post is a little bit different in that it’s a guest post.  Fellow N Scale modeller Mike Musick has written an article about improving Con-Cors N Scale U50s, Turbines, and my imminent C-855 by replacing the wheel sets.

So without further ado, I hand you over to Mike.

(Also applies to Con-Cor Veranda Turbines)

The Con-Cor U50’s ungainly aesthetics are not helped by its oversize wheels. In all production runs the wheels measure to a scale 48″, versus the prototype’s 40″. While the 0.025″ increase in model height alone doesn’t alter the proportions perceptibly, the too-large diameter plus the oversized flanges of the 1970s design result in the wheels being visible above the truck frame, giving the model a toy-like appearance.

Oddly, the Con-Cor/Kato model of the PA produced prior to the U50 had nearly-correct wheel diameters. Replacing the U50 driven wheels (eight of the sixteen) with PA wheelsets is a straight-across swap since the gear and axle sizes are the same. However, it does require the sacrifice of an out-of-production PA model, and carries forward the large flanges of the era. It also doesn’t solve the issue of the undriven idler axles on the inner U50 trucks, which have cone-point bearings.

Fortunately, there are wheels and point-axle wheelsets available from Northwest Short Line ( for retrofit. The separate wheels work well and look good, but will require fabrication of half-axles to work with the Con-Cor gearing. We are specifying 42″ wheels as opposed to 40″ to stay out of trouble with truck frame clearance issues on less-than-perfect track.

NWSL Wheels

Powered axles use NWSL #96000110, “N scale WHEEL ONLY, 42″/64 NS, 3/32″ bore”. You will need eight (8) wheels per locomotive.

Unpowered axles use a custom wheelset, specified as “N 42″/64 wheels on Pointed 1.5mm x .560″ axle (4/pkg)”. A single package of four (4) wheels covers each locomotive. Specify bright NS finish to match the powered wheels.


Removing wheelsets is a simple operation. Remove the two screws in the driven trucks, and the outer frame will lift off, with the idler truck probably lifting off at the same time. The driven wheelsets will be easy to remove. On some production runs there is a brass shim on one side of the center frame, be sure to note the orientation before removing the second axle.

With each idler truck separated from the driven truck, unscrew the single frame screw from the weight to access the wheelsets. Snap out the wheelsets and replace with the NWSL point-axle versions. Reassemble frame and set aside for later assembly with the driven trucks.

Carefully remove the half-axles from the gears by firmly pulling. Be careful to not use any bending forces against the plastic gear shaft since it is easily bent, resulting in a wobbly finished axle.

For the new half-axles, use 3/32″ K&S brass tubing in the standard hobby-store wall thickness. Cut eight pieces of this tubing to a moderately precise 0.193″, as this determines wheel gauge. Dress each cut end with a needle file, then insert each piece of tubing into a wheel so the end of the tubing is flush with the outer hub. Don’t rely on measuring the old half-axles to determine axle length. They are 0.200″. The 0.007″ difference corresponds to the narrower tread of the NWSL “/64″ wheel size.

DO NOT try to press the new half-axles onto a gear shaft! At least not yet. The tubing must first be reamed to fit the gear shaft; attempts to press-fit without reaming will likely result in a broken gear shaft. First dress the inner edge of the tubing with a micro needle file or jeweler’s cone reamer, then follow with a #52 (0.0635”) drill bit (Be advised that a 1.65mm bit might be too large and 1.6mm too small. Try the larger bit first with a scrap of tubing for snug fit. Forcing a too-tight, smaller reaming size risks breaking the axle), reaming the entire length of tubing. This will make for a firm but not-too-firm press fit on the Con-Cor gear shaft. With both half-axles on the gear shaft, check gauge and adjust if necessary.

Repeat the process for the other three driven axles, then reassemble. Don’t forget the brass shims in the proper locations if your model had them. Be sure to observe the orientation of the idler truck since it is very easy to install upside down. Check run the loco and you are all done.

Mike also provided a few photos to show the difference in an original and converted U50 model; the original wheelsets are in the loco on the left.

Con -Cor U50-Turbine Wheelsets 4 (Mike Musick)

Close up the gap between the truck and rail head is notably different as well as the lack of flange protruding above the truck.

Con -Cor U50-Turbine Wheelsets 6 (Mike Musick)

In this shot you can clearly see the difference in flange width.

Con -Cor U50-Turbine Wheelsets 7 (Mike Musick)

Below is a close up of the NWSL wheels in place.

Con -Cor U50-Turbine Wheelsets 3 (Mike Musick)

And a shot of them before they were attached to the drive axle.

Con -Cor U50-Turbine Wheelsets 2 (Mike Musick)

I leave you this week by saying thanks to Mike for his post and to let you know that I will be at Brighton Model World this weekend with all of our N Scale module layout, ‘Solent Summit’.  So if you are in the area and are coming to the show please come and say hello.

Drawing an Alco C-855 for N Scale Part 5

If you have been following my blog for a while you will know that I have been working on an N Scale Alco C-855.  You can read the first part here.  In this week”s post I will share with you what I have done to finish the A unit and get it ready to order a test print.

In my last post about the C-855 I showed you the first print of the metal chassis extenders and how I fitted them into the Con-Cor Turbine/U50 chassis.

C-855 Chassis Build 15

This chassis runs well, and pulls even more than in its original counterpart; probably due to the increased weight.  However there were a few issues with the print so I have improved the 3D model to rectify them.  In the image below you can see both parts from the top and bottom.

Alco C-855 Chassis Extenders mk2 (render)

The space for the motor has been widened by a fraction as the motor was a tight fit in the first print.  The wire channel has also been increased in size so the motor wire is a better fit.  I have also made some changes to the bottom of the lower section.  The arrows point forward on both parts to help with orientation when assembling the chassis.  There is now a rectangular nub that sticks out to locate the fuel tank on the bottom of the locomotive.  Also a square hole has been added which has been designed to take a 3D printed screw fixing which is used to hold on the fuel tank.  The exploded view below shows how these fit together.

Alco C-855 Fuel Tank Fitting 1 (render)

I have designed this assembly so the original Con-Cor turbine/U50 screw can be used athough any similar size screw will work.

Alco C-855 Fuel Tank Fitting 2 (render)

This section of the fuel tank is only the bottom as the sides are part of the main body.  Looking at the image above you can see a square hole in the side of the fuel tank, this is designed to receive a nub sticking out from the shell. You can see the nub in the image below which shows half of the shell.  As the bottom of the fuel tank is fixed with the screw it becomes a solid fixing for the shell.

Alco C-855 In Side Shell (Render)

As with a lot of ready-to-run locomotives, to remove the shell it can simply be spread in the middle and lifted off.

To make painting and adding decals to this model easier the four large sand boxes on the sides have been made as separate parts.  The rear six are the same but the front pair are longer as they have to step over parts of the chassis.  The shell has slotted fixings in the side of the running board to receive the sand boxes so they can be securely fitted.  The holes on the tops are handrail fixings.

Alco C-855 Sandboxes (render)

As with my DT6-6-2000 and RT-624 locomotives my C-855 will come with crew for the cab, Bert and Ernie.  The controls on the console are very basic but this is N scale so once they are inside the cab it will be hard to see anyway.

Alco C-855 Crew (Render)

Because of the shape of the chassis, there is a large chunk of metal sticking up into the cab, the crew had to be pushed to the sides.  There are locator pockets in the shell walls to receive the crew once they have been painted.  As the C-855s ran in an A-B-A configuration you may not want crew in the rear A unit so they can simply be left out.

Below you can see the crew in their place with half the shell removed.

Alco C-855 Inside cab (Render)

This view also shows you the headlight fitting in the roof of the cab.  The shell has been shaped to receive a standard 3v 2mm LED.  A nice warm white LED can be fitted directly into the roof of the cab and a pair of headlights will shine from the front.  This area will need to be painted black on the inside to prevent the light from shining through the shell.

Even the horn is a separate 3D printed part; this is both to make it easer to paint and to protect it from being knocked off in shipping.  Below you can see all the 3D printed plastic parts for one C-855.  The large gears are the drive shaft extenders which are needed when the chassis is extended.

Alco C-855 3D printed parts (render)

In the cab you can see lots of holes; this is because all the grab irons and handrails plus many other details are brass parts that will be supplied in a brass Additions set. The set will also include some of the metal walkways, windscreen wipers, side ladders, MU hoses and sun visors for the cab.

So putting this all together, this is how the N Scale C-855 will look.  Please note the trucks under the 3D model are not yet correct.

The end will have brass grab irons up the center and walkways over the air intakes.

Alco C-855 end (render)

The cab with all of its brass parts will be well detailed

Alco C-855 666.Front (render)

Overall this monster of a locomotive has an imposing presence.

Alco C-855 (Render)

The next step is to finish the drawings for the B unit and design a dummy chassis so an A-B-A set can be made without powering all the units, if required.

The new 3D printed metal parts as well as the 3D printed plastic parts for the C-855 have new been sent for test printing so I should have the first N Scale C-855 within the next few weeks.  Once it arrives and I have cleaned up all the parts I will share some images with you.

Improving Peco Points for DCC Operation

In this week’s post I will show you how I modify Peco points or turnouts to use with DCC, and explain why I make the changes.

Peco make a variety of points in all the common scales and I have used them for many years.  Personally, having used them for American and British trains in both N and OO scales, I think they are the best ready-to-run points available.  However I always make modifications to them rather than use them directly out of the packet.  You can use them directly from the packet and they will work just fine, but I find for lasting reliability a few improvements are needed.  For my example I am using some brand new OO/HO large radius points as shown bellow.

Peco Points DCC Conversion 1

This point, as it states on the packet, is an Electrofrog.  This means that the area where the rails cross, commonly called the frog, is metal, allowing the maximum amount of electrical connection with the pickup wheels of your trains.  Peco’s other points are called Insulfrog and these have a plastic frog. Insulfrogs are the easiest to install because the plastic frog isolates all the rails so you don’t have to make any electrical brakes in the track or do any special electrics. But the downside is the large electrically ‘dead’ section over the plastic frog which can cause stalls with slow-moving or small trains.  So I always use Electrofrog points.

To use the point shown below all you need to do is connect the two inner rails using a plastic rail joiner.

Peco Points DCC Conversion 2

Below is an extract from the back of the Peco packet showing how to wire this up for DC or DCC power.  With DC power if you don’t include the isolating rail joiner the point will also switch the power on and off in the two sidings.  It does this by making the polarity of the rail connected to the frog the same as the stock rail (outside rail) for the route that is not selected.

Peco Points DCC Conversion 2-1

As I said before, using this point directly out of the packet and connecting it as shown above should work just fine but the drawback is how the power is delivered to the frog.

As supplied, the frog relies on electricity travelling from the stock rail into the point blade via the contact of the two surfaces.  Then it travels up the blade rail to the frog.  When the point is changed the other point blade makes contact with the other stock rail and the power is fed from that side, also reversing the polarity of the frog.  The point throw bar has a built-in spring which keeps pressure on the point blade, holding it against the stock rail.  When the track is new and shiny this is fine, but over time dust and grime will get inbetween the two and the electrical connection will become weaker.  And if you weather and ballast your track this connection will probably stop working altogether.  It can be cleaned by using a piece of fine sand paper or a file but this is not an ideal solution or a permanent fix.  Plus the point blade can easily be bent and it’s next to impossible to get it back to straight again.

There is also another problem that can occur.  Electricity will always follow the path of least resistance.  For example if you had a bit of track with two power connections and one was badly soldered, although you can’t tell, the electricity would flow through the good connection.

So imagine you had a point connected as described above with dirt or dust inbetween the point blade and the stock rail; it’s just about working and the locos will travel over it.  But the train you are pulling has a coach with a light in it powered from the track and there are pick-ups on all wheels of the coach.  As the coach spans the point blade, i.e with one truck or bogie on the stock rails and one on the frog the electricity will elect to travel through the coach and not through the points.  If the lighting circuit in the coach is only a 1.3v LED with a tiny current draw it will not be designed for a lot of power and there is a chance that it will blow.  This could happen as the full voltage being pulled by the loco is now passing thought the coach circuit.  With a DCC powered layout it may also have the current from several locos running through the coach and I have seen a coach that was parked across such a point that got so hot that the truck actually melted.

So now you know why I modify the points, but what do I actually do?

The first step is to decide how else you can power the frog because it needs to be fed from one stock rail or the other, depending on the direction it’s set in.  This can be done in a variety of ways.  Peco make an accessory switch that can be fitted to their point motors to power the frog.  Seep point motors and Tortoise slow motion point motors both have a built-in switche that can be connect directly to the frog.  Peco also make an electronic switch called a smart frog, this will only work with DCC.  The smart frog is connected to the power bus and the frog. As a train wheel makes contact with the frog, if the polarity is wrong, it will detect a short faster than the DCC control system and reverse the polarity, allowing the train to continue as if nothing was wrong. Other companies like Tam Valley make the Frog Juicer which works in a similar way to the Peco smart frog.

Simply feeding the frog will greatly improve the performance of the point because the power will run up into the frog and back down the point blades but there’s still an issue.  The point blade that’s not touching a stock rail will be a different polarity, as both point blades and the frog are all the same, and there’s the possibility with wide flanged rolling stock that a short could happen as a train passes by.  To overcome this Peco have given access to the connecting wires on the underside of the point.  In the picture below you can see two small slots in the plastic, each with a connecting wire in.  These wires join the frog to the point blades. I remove these wires; as they have been spot welded in the factory you can simply put a small flat ended screwdriver into the slot next to the wire joint and twist.  The spot weld will break, repeat for the other end and the wire will fall out.

Peco Points DCC Conversion 3 The problem now is the point blades are again reliant on the contact with the stock rail, however Peco have made this easy to fix.  As you can see in the image below, next to the slots where we removed the connecting wire, they have omitted some of the plastic allowing access to the underside of the stock rails and the top of the point blades.  On older points this access is not there but can easily be made with a sharp knife.

Peco Points DCC Conversion 5

Using a soldering iron I tinned the underside of the rails with solder.

Peco Points DCC Conversion 6

I then stripped the insulation off some solid core wire and cut it into strips, the same length as the distance between the stock rail and nearest point blade.

Peco Points DCC Conversion 7

Then I placed the wire over the gaps and used the soldering iron to attach each end to the tinned area.

Peco Points DCC Conversion 8

Repeating this on both sides means that the point blades are permanently connected to the stock rails.

Peco Points DCC Conversion 9

And there you go; the point is ready to be installed on the layout.  There’s no danger of a bad connection to the point blades, or a short between the free point blade and the stock rail and the frog is powered via a switch.  This point will be electrically reliable even when weathered and ballasted .

Peco Points DCC Conversion 10

So although Peco points work straight from the packet, in my experience making these improvements up front will make your layout more reliable and keep your trains running well for years.