Replacement Bachmann OO Chassis Fasteners & Washers

This week I have another new replacement part to share with you. A locomotive was brought in to get DCC sound fitted and I know from experience there’s a good chance certain parts will break when the locomotive is taken apart, and in this instance I was not mistaken.  The Locomotive in question is a Gresly V2  made by Bachmann under their Branch Line range.

These locomotives are very good, although now an older model, and are normally very reliable.  The primary problem these, and other locos in the range, suffer from is split axels and I’ve already 3D printed parts to repair them, which you can read about here.

However, the axels on this locomotive are fine; the issue is with the split chassis fasteners.  A lot, if not all, of the Bachmann locomotives of this generation, have a split chassis.  This means the chassis is in two halves with each side conducting power from the wheels to the motor, eliminating the need for wires.  For DC operation this is perfect.  But for DCC I need to separate the chassis halves to electrically isolate the motor.  The chassis halves need to be screwed together but electrically separated.  This is achieved by using a plastic chassis fastener, plastic washer and metal screw.  The fastener has a square head that fits into a square recess in the left chassis half to stop it rotating.  The washer fits between the chassis halves, over the fastener to separate them, and the screw pulls the parts together as it bites into the fastener.

The problem comes, as with this V2, when the locomotive has never been taken apart and the plastic fastener has either deteriorated or maybe shrunk.  I’m not sure what actually happens.  But the screws are very tight and the force needed to get it to move is often more than the fastener can take and the tube section twists off the square head; as you can see below.

Or the tube section simply breaks at the end of the screw, which also happened on this locomotive.

It is possible, if you’re both careful and lucky, to glue the parts back together, but more times than not it doesn’t work and I often come across these locos with several missing fasteners.

So my solution, as is my way, is to 3D print replacement parts.  I designed the fastener to be a direct replacement and included a washer as sometimes the originals can get lost.  They are 3D printed in Shapeways Fine Detail Plastic as it’s the most accurate.

Before these can be used it’s very important to clean out the tube section.  This is because it will be full of 3D print residue which, if left inside, will add pressure to the tube wall as the screw is driven in, cracking the tube.  To clean out the tube I use a 1.26mm (0.049″) drill in a pin vice.  This won’t actually remove any of the tube material, just ream out the hole, as you can see below.

There’s usually a lot of residue in the hole because it’s small and Shapeways post-cleaning processes can’t get in there.

With the fasteners ready the chassis can be reassembled.  The V2 uses five, as you can see below by the holes in the right side chassis half.

With both sides fitted you can see the square heads in the left side chassis half.  It was only when I put this photo up I realized I had the front one in the wrong way round.  Fortunately with that one it works from either side.

The square recess in the left chassis half has a bit of tolerance so the head will rotate a little.

These replacement fasteners and washers can be used on a large variety of Bachmann split chassis locomotives and I’ve made them available in a set of 6 here and a set of 12 here.

This particular V2 is now back up and running and has an ESU sound DCC decoder, working lamps, and a realistic firebox flicker whenever the fireman opens the firebox door, which reflects nicely around the cab.

If you have another part, such as this fastener, which has broken and you can’t find a replacement I’d be happy to see if I can draw it up for 3D printing.  You can get in touch via the contact page.

Replacement Bell Cranks for an MRC/Rowa N Scale 2-8-4 and 2-8-8-2

Back in May of 2015 I needed a replacement eccentric rod for an N Scale Rowa/MRC 2-8-4 Berkshire to replace a missing one on a second-hand locomotive, and designed and 3D printed the part.  The post can be found here.

Since then I’ve had a request to provide a replacement bell crank for the Rowa/MRC 2-8-8-2 Y6B.  This mighty steam locomotive was one of the original N scale greats dating back to 1969 when MRC first released it.

It went through a few changes and was re-released in 1977 by Con-Cor/Rivarossi.

One of the main differences in the two versions is the side rods and valve gear.  The original MRC, and later Rowa version had plastic parts, whereas the later Concor/Rivarossi ones had metal.  The part I’m replacing is on the earlier MRC/Rowa version, which coincidently is exactly the same on their 2-8-4 Berkshire.

The original Berkshire bell crank and eccentric rod are shown below.  They simply clip together and the bell crank rotates about the round lug, which is at the other end from the C section.

The new 3D printed bell cranks are printed on a sprue, simply because they’re so small.

Up close you can see the new 3D printed part is slightly chunkier than the original injection molded part to give some extra strength to it.  Once fitted it’s very hard to see the difference.

On the Berkshire, with the bell crank removed, you can see the circular hole at the back of the bell housing to receive the round lug.

The new part clipped right in and rocked back and forward with ease.  The part will ideally be painted silver before the final install.

The original eccentric rod clips into the new bell crank and the main drive wheel, fixing with ease, and that’s it.  This particular Berkshire has no motor in it so I can’t show it running, but it ran freely along the track by hand with no issues from the new bell crank.

The Y6B, as I said before, has the exact same bell cranks, just more of them.

The only difference is the eccentric rod is shorter, which is caused by the altered geometry of smaller driving wheels compared to the Berkshire.

A pack of 6 bell cranks for MRC/Rowa 2-8-4s and 2-8-8-2s are available here.

I’ve had some time to get around to finishing some other long overdue 3D printing projects and over the next few weeks, I look forward to sharing these with you and making them available to buy.

New Gears For A Bachmann N Scale Doodlebug

The first post of this year showed you the problems with split axels on a Bachmann N Scale Doodlebug, which can be found here. In this post, I’ll show you the result of the 3D print.

The four 3D parts, as pictured below in the top of the image, are the two drive gear axels and two free axels.  The Doodlebug does have other gears between the motor and the wheels but it’s only these parts that break as they have metal axles forced into them, causing them to crack over time.

The two parts in the middle are an original cracked gear and axel, and at the bottom are an original gear and axel with the wheels fitted.

Before I fit the wheels to the new parts I pass a 1.5mm (0.058″) drill through each part. The drill is ever-so-slightly smaller than the hole in the part, so no actual material is removed, but it cleans out the 3D print residue and ensures a good fit.  If there’s residue the fit can be too tight and cause the new part to crack.

One thing to note; two of the wheels have traction tires and both fit onto one of the axels.  If, like me, you accidentally fit a regular wheel to this axel it can be very difficult to remove and there’s a good chance you’ll break a tooth on the new gear, which is what I did.  That’s why in the new set below I still have one original gear that wasn’t cracked.

The drive gear set clips into the truck tower, with the new gears meshing with the originals.

The plain axels for the trailing truck simply rest in the cutouts.  Both trucks have a plastic clip that holds everything in place.

With the trucks refitted, power pickups replaced, and truck sides attached, the chassis is ready for a test.

And it ran very well, smooth and free, so I refitted the shell.

At some point, I’ll fit a DCC decoder to the Doodlebug, but first I want to tone down the paint job.  Although it’s in the UP colors or Armour Yellow and Harbour Mist Gray, I do find it a bit bright.  But with some weathering, I think it’ll look just fine.

The 3D printed replacement axles for the Doodlebug are now available through my Shapeways shop and can be found here.

I’m slowly working my way through the older Bachmann locomotives which I’ve found tend to have split gears.  I’ve got the first two versions of the N Scale DD40AX and the N Scale PCC Interurban Streamlined Car next on the workbench and will be drawing designs for those for replacement 3D printed gears too.