Shapeways Sale – Cyber Monday

With the holiday season well underway Shapeways have announced their Cyber Monday sale. They’re offering 10% off everything from 12:01am EST all day on November 29th, 2021 through to December 1st, 2021 at 3:00am EST.

To enjoy the savings all you need to do is enter the code CYBER2021 at the checkout.

All of my 3D printed models, including the new HO RT624, are in the sale and can be found either by using the dropdown Shop menu above or going direct to my Shapeways site using the link below.

Happy shopping!

New Axles for a Second Generation Bachmann HO 4-8-4 Northern – Part 2

As promised in my last post I’ve now received the first test print for my new 3D printed axles for this locomotive, and in this post I’ll share with you how well they worked out.

This was the first test print for this design and although the design has been well thought out there’s always a chance that something’s not right, so I printed three sets.

Each set contains one drive gear and three axles; below you can see an original axle and gear for comparison.

With the new parts removed from the sprue, a closer comparison can be made. And for me, the first thing that stands out is the size of the square hole. It appears much smaller on the new part than the original, which in fact it is, but by design.

The reason for the smaller size is based on the actual axle size on the wheels. I need the replacement parts to be a tight fit but not so tight that the new parts split. Sadly they do. The reason for this is due to variances in the wheel axles. The wheels are not machined, they are cast. Then they’re plated which gives them their shiny finish and conductive coating. However, this leads to a large variance in the thickness of the axles. It’s not enough to be really visible, but it’s enough to make a difference in splitting an axle or not. So I’ill need to adjust my 3D model to allow for this.

In order to complete this test, I still wanted to see if all the other aspects of the gear and axles worked, so I filed the square hole with a square needle file to enlarge them slightly.

Now the main drive gear is fitted. Quartering the wheels, or making sure the wheels are at 90° to each other, was very easy with the square holes, and the two wheels pushed into the axle without splitting it. Although the axles have been designed to correctly space the wheels it’s good to check the distance between the back of the wheels, which should be 14.4mm for HO. I use a laser-cut ‘back-to-back’ checker as you can see below. This should be a snug fit between the wheels.

All the axles have now been fitted and spaced. At this point, I check to make sure all the wheel assemblies can move freely and none of the valve gear is misaligned.

The last part is refitting the base plate to hold everything in. For this locomotive, the base plate also holds the pilot and trailing truck and clips onto the chassis. There are two screws in the base to hold it on.

And then comes the test, does it work under power? At this stage, I’m looking for three things; does it run freely, does it run at slow speeds without binding, and most importantly, how does it perform under load? If you followed my previous design post about the first generation of this locomotive, the original gear was very thin and the first design for the replacement gear cracked or stripped its teeth under load. Luckily the second generation already has a much thicker gear. In the short video below you can see I tested all of these.

And I’m pleased to say it passed all three tests. Given that I had to enlarge the square hole in all the parts I’ve now updated my 3D model to reflect this and I’ve ordered a second test print. I also made a slight change to the angle of the teeth on the main gear. I don’t see a problem but it brings the angle more in line with the teeth on the contacting gear.

Hopefully, the new test sets will be here soon and I’ll replace the gears in this chassis to see how well they fit. If everything is okay, with no splitting, I’ll release the Bachmann HO 4-8-4 Gen 2 replacement axles and gears for sale.

New Axles for a Second Generation Bachmann HO 4-8-4 Northern

Back in 2018 I shared with you my design for replacement axles and gears for a HO Bachmann 4-8-4 Northern.  You can find the post here. That turned out to be quite the adventure, as simply creating replacement parts didn’t work out so well!  Due to the thinness of the original components I had to engineer a much thicker gear which could handle the force applied from the motor.  This turned out to be a success.  But this gear and axle set only worked for the first generation of the Bachmann HO 4-8-4.   As it turns out, although Bachmann redesigned and improved the second generation, it too has problems with split axles and gears, and I’ve regularly been asked if I could produce a set for this locomotive.  Well, I finally have and in this post I’ll share the design with you.

To start, I want to explain the difference between the three generations that are commonly available.  I’m not going to go into any of the body or cosmetic differences, just the drive train so you can tell which generation you have.

The first generation, as I’ve already covered in other posts, has a pancake motor which drives the rear axle.  Below is an exploded schematic drawing, courtesy of John on the Tyco Depot Train Collectors & Model Railroading Forum. You can just about see the gear on the rear axle.

Looking at the underside of the locomotive there’s a bump over the rear axle to make way for the gear. 

This is the main clue that it’s a first generation.  This locomotive also has round wheel stubs and holes in the axles.  That’s what makes quartering the valve gear tricky on this locomotive.  ‘Quartering’ means setting the piston rods and side rods on each side of the locomotive at 90° to each other; as the wheel stubs are round it’s easy to get it in the wrong place meaning the loco won’t run smoothly.

The second generation had a lot of improvements such as a can motor and thicker gears and axles.  But most importantly the axles and wheel stubs also have square stubs and holes, making quartering far easier to do. You can just about make out the cracks in the axle and gear.

Below is an exploded schematic drawing, also courtesy of John.

The motor this time drives the third axle and there’s no bump in the base plate; this along with the lack of wires running to the tender tells you it’s a second generation.

The third generation, which I believe is the version currently available, had a total redesign.  It still has a can motor which drives the third axle, but everything else has changed.  Looking at the exploded schematic drawing below, again courtesy of John, you can see the axles are a different shape. 

To my knowledge, these don’t fail.  These are normally marked as DCC ready and will have wires connecting the tender to the locomotive; the DCC socket and speakers for sound are located in the tender.

Looking inside the second generation you can see the axles and drive gear on the third axle. The second axle is clearly split and once I removed the others I discovered they had split too. As the wheel stubs are square they don’t need to be such a tight fit as the round ones on the first generation.

Interestingly the axles are almost identical to the axles used on the UK Bachmann (former Mainline) designed locomotives that I have 3D printed replacements, for as shown below.  These were for a GWR Hall class and can be found here.

However, upon measuring the US 4-8-4 axles and gears I found them slightly different, so a new design was needed. These have been designed to be 3D printed in Shapeways Smooth Fine Detail Plastic.

The kit I’ll supply will contain three axles and a main drive gear. The idler gear between the worm and axle gear to my knowledge never breaks so I haven’t supplied that; if yours has, please let me know and I will add it to the kit.

These have now been sent off for a test print and I’ll see how well they work.  As with the first generation, and the UK Bachmann locos, I’m restricted by the size of the axle box and the size of the wheel stub.  This means the axle itself nearest the wheel is still not as thick as I would like it to be, and it’s possible to crack the new axles if not cleaned properly before use.  Once I’ve test fitted a few, if it appears too easy to crack the new ones I will include a few spares in each kit.

So now I’m waiting for the 3D printed parts to arrive, and I’ll share them with you when they do.

Updating Your Digitrax Products

As with most equipment, manufacturers often make improvements to their products after you’ve purchased them.  The nice thing with electrical equipment is these improvements are often related to the way it works rather than a physical change, so this can be updated.  In this post I’ll show you how you can check to see if your Digitrax equipment is up-to-date and if not, how to change it.

Digitrax equipment is very reliable and robust, but most of their equipment has had a small improvement made at some point.  Just like a computer or mobile phone, electrical equipment has a program that runs on the circuit boards. This program is called firmware, unlike software that runs on a computer, firmware is the program that tells the components what to do.

Below is an example of some common Digitrax equipment.  From left to right we have a DT602D radio throttle, a DT500 throttle, a DCS 240 command station, a DCS 51 command station and a PR3 USB to PC interface.  All of this equipment has firmware and all of it has an update available.

Some of the equipment, such as the newer DT602, tells you what version the firmware is when it starts up. Below you can see this throttle has SW Version 0000.1 and is dated July 15, 2021.

Other equipment such as the command stations and older equipment don’t have a such a clear display. But there are ways to find out what the firmware version is.  To do this Digitrax have a piece of software called DigiIPL and this can be downloaded from their website  This software can be installed on a PC, laptop or Windows-based tablet, but don’t start it up yet.

To connect the Digitrax equipment to the DigiIPL program you will need a USB cable, which should have been supplied with the command station.  If not, the same type of cable often used with printers will work. The cable needs a USB Type A fitting on one end and a USB Type B fitting on the other as shown below

The newer command stations, such as the DCS 240 have a USB port on the front of the unit but the older models such as the DCS 51 do not. I’ll show you how to connect those later.

With the USB cable plugged into your computer and the DCS (DCS stands for Digital Command Station) connected to its own power supply, the PC will assign a COM port to it. This is the address of the connection, depending on what else you have plugged in this will be different for each user, we will find out what it is in a minute.

With the DCS connected you can now start the DigiIPL program and it will look like this.

You’ll notice at the top left a Loconet Port has not been selected, this is where the COM port is entered. Luckily you can only select from Com ports that are active, mine had been assigned to Com 4. If there’s more than one, try the first and if that doesn’t work try the next. It’s also important to note the ‘Bit Rate’ should be set to 16457 although by default it always is.

At this stage I should point out that if you have lots of Digitrax equipment, particularly lots of the same item, it is a good idea not to have it all plugged in to the command station at the same time when doing this. Theoretically it should work but it’s recommended to do this individually.

Once you’re ready you can push the ‘Find Devices’ button and it will open another window listing the equipment, and below you can see the DCS 240 listed and is at SW version 0.3.

If I plug in the DT602D from earlier and push the ‘Find Devices’ button again you can see it listed showing the SW Version 0.1 as we saw before.

So now we know the current SW (Firmware) version but how do we know if it’s the latest? Heading back to the Digitrax website on their downloads page they have all the available updates listed. Below you can see the DCS 240 is at version 0.4 and the DT602 is at version 0.1 so only the DCS 240 needs to be updated. (I did the DT602 the other week).

To update the DCS 240, or any Digitrax equipment, download the relevant firmware to your computer. Then using the ‘Select File’ button, select the downloaded firmware file.

Pressing the ‘Start’ button will now update the equipment.

Once done you can check to see if the update was successful by pressing the ‘Find Devices’ button again to check the version.

When it comes to the older equipment, such as the DCS 51 that don’t have a USB port, an interface is needed. This is where the PR3 shown in the first photo comes in. Below you can see the USB cable connected to the PR3 and the PR3 connected to the DCS 51 via a Loconet cable.

With the new equipment connected the DigiIPL has to be restarted. This time it has connected on Com 5. Using the ‘Find Devices’ I can see the PR3 and DCS 51, but only the DCS 51 needs an update.

And thats it, all up to date. It’s always a good idea to update any firmware, Digitrax or otherwise. The chances are you will not see a difference in how your device works but there’s a good chance it will fix a problem you didn’t even know was there.

New Gears For A Bachmann N Scale Street Car & Brill Trolley

This is a project that I started at the beginning of 2020 so it’s about time I shared it with you. The Bachmann PCC Interurban Streamlined Car has been around since 1983 and was released in a large variety of paint schemes and liveries. However, all the models released up until about 2000, when Bachmann upgraded the chassis, suffer from the same problem; the white plastic gears on the axles crack. In this post I’ll share with you my 3D printed replacements to fix this.

The PCC Interurban Streamlined Car, and similar Brill Trolley released the year before, share a similar chassis with the same trucks. The body is all plastic and clips over the metal chassis, which fills the body.

The underside is fairly basic and you can see all four axles are driven via gears. These are the gears that crack under the pressure of the metal axles press fitted into them.

With the body removed you can see the chassis, which is made of two halves and separated by Bachmann standard fastener and washer system. Should these brake I’ve made replacements available here.

With the two screws removed the chassis haves come apart and the trucks fall out, although the repair can be done without separating the chassis or removing the trucks if you wish.

The large drive gear in the centre of the truck doesn’t have any issues.

The wheels have a short axle which press fits into the gear, when fully inserted the two axles do not touch each other so the gear also forms the electrical isolation. The wheels should just pull out. If the gears are cracked they’ll come out very easily.

The original gears, as shown on the right of the photo below, are made from a material that’s prone to cracking and you can see the light change as it hits the crack in the gear. With the metal wheel inserted the crack opens up. This causes two issues; firstly the spacing between two of the teeth is larger than the rest and causes a bump as the gear turns or jams the other gear. The second issue is there is little friction between the gear and the axles so the gear may turn, but the wheel won’t.

3D printing a set of four to replace all the gears is the answer and given the small size of these gears, roughly 5mm (0.196″) diameter, the best material is Shapeways Smooth Fine Detail because of its accuracy and hard-wearing properties. All four have been printed on a sprue so they don’t get lost in the printer.

Unlike injection moulding the sprue doesn’t actually touch the gears, it just passes through the hole in the middle. This can easily be cut with side cutters and the gears are ready to use, although I would recommend cleaning out the hole in the axles of any 3D print residue before you use them.

Refitting the gears and wheels is fairly simple. Position the new axle gear inside the truck and lightly push the wheel axle through the hole in the truck and into the gear. With both wheels lightly fitted, press the wheels together to press fit them firmly into the gear, just don’t push them in too far. The inside distance between the back of the wheels, commonly known as the Back-To-Back dimension, should be 7.65mm (0.301″).

Even if only one of your gears is cracked I would recommend changing all four as it’s probable the others will crack once you start using it again.

And that’s it, the street car is ready to use. The set of four gear axles can be found here.

I have several new gears for different loco types and scales to share with you over the next few months, but if you have something that needs a gear, get in touch. Just like this project I started last year, I may have all ready done it!

Back To Work after the Summer Break

It’s been several weeks since I last posted but that’s not to say I’ve not been busy. Given the strange times we’ve all been experiencing over the last year and a half, including the necessary travel restrictions, I took the opportunity to do as much as I could away from the workshop this summer. And that’s included some model railway stuff which I hope to share with you when ready.

But for now I’m back in the workshop with my batteries re-charged ready get on with the existing projects which have been on hold, several locomotive repairs, new builds and new projects. And there are quite a few!

As each project gets worked on or finished I’ll be getting back into my regular weekly posts to share it all with you.

As for tonight I have just had a big clean up of my work benches and desk to make a start, let’s see what I can get done for next week!