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.

An N Gauge Dapol Britannia Driveshaft

This week I have a new product to share with you.  The N Gauge Dapol 4-6-2 Britannia is a great model.  But in a similar way to the N Scale Roundhouse, now Athearn’s, 2-6-0 and 2-8-0 steam engines, and the Atlas N Scale 4-4-0, this particular model also needed a new driveshaft and yoke.

The motor, and DCC decoder, is packed into the tender and a drive shaft runs through the cab to power the main driving wheels.  The motor axle has a yoke fitted to the end, as does the spindle in the cab.  A driveshaft connects the two yokes and allows the tender and locomotive to twist without breaking the transmission of power, just like a drive shaft does on a car without being affected by the car’s suspension or steering.

I modeled the three parts after taking measurements from the originals.  I made the driveshaft slightly longer as I’ve often had originals come apart when handling the locomotive. The set on the left are loose, but in order to avoid an individual part print charge, I’ve combined them into the set on the right.  None of the parts actually touch the sprew which can simply be cut away.

The parts were printed in Shapeways Smooth Fine Detail Plastic, as it’s the most accurate for small parts, and they came out very well.

On the model, it was the yoke on the motor axle which was missing.  This is normally due to the original splitting.  If the valve gear on the locomotive jams and the motor carries on trying to spin, the force can cause this to happen.

The new yoke, with a little bit of pressure, fitted onto the axle.  I’ve designed the hole in the yoke to be very slightly smaller than the axle so the pressure fit will prevent it from spinning on the axle.  Whenever fitting anything like this it’s important to make sure the inside of the yoke is clean and free from any 3D print residue, as this may cause an even tighter fit and could lead to the new yoke cracking as well.

As the old yoke on the locomotive spindle was intact I didn’t change it, but as you can see the new driveshaft fits well.

With the locomotive reassembled I also tried it with the original driveshaft; you can just make out the black spokes in the new tender yoke.

But I did find, as with the original setup, the driveshaft came out too easily.  The new 3D printed one is almost 0.8mm longer than the original and this helped keep it in place as you can see below.  Another alternative would be to slide the tender yoke slightly closer to the locomotive.

The last step was to test the new driveshaft and as you can see below I’ve lifted the locomotive driving wheels off the track for the first test.  I wanted to run the loco at speed for a while, and as the rear set of drivers have traction tires which are susceptible to coming off, I didn’t want to give them the chance.

The next test was to do several successful trips around the layout with twelve coaches behind, which it did with ease.

The Dapol N Britannia Driveshaft Repair Kit is available here.

This coming weekend is the NMRA(BR) Benson winter meet and I’ll be there with my fellow club members and parts of our ‘Solent Summit’ layout.  As this is only a one-day event we won’t be putting on a 5 Mile show like we did at Warley!

The event is at the Benson Village Hall, Sunnyside, Benson, Oxfordshire OX10 6LZ from 10am till 4pm. I hope to see you there if you can make it, if not I hope to get some photos to share with you next week.

A Dummy Knuckle Coupler for OO Gauge – Part 3

Back in July, I shared with the second part in my design of a dummy knuckle coupler for OO gauge rolling stock.  You can find the post here.  Since then the first prints have been through several tests and they performed very well.  In this post I’ll show you the small changes I made to the design and share with you how to get some.

The original design, as shown below, was printed in both Shapeways clear Fine Detail Plastic and the Black Versatile Plastic.  The Black Versatile Plastic turned out to be so good I’ve carried on with only this material.  Not only is it strong, but as it’s already the right color, they’re ready to use.

The original design was for a dummy knuckle coupling which would work with Kadee couplings as well as each other.

The first issue I had with them, albeit a small one, was with the knuckle section.  As the actual knuckle, unlike the Kadee, doesn’t swing, and it tended to grip on tight curves.  I opened the jaws slightly to allow a bit more movement.  This solved the issue.

The second issue was due to height.  As I’ve said in other posts about couplings, despite there being the NEM standard regarding couplings and height, different manufacturers have positioned their coupling pockets at different heights. Some seem to be high and some low, which leads to the situation of an uncoupling, especially on gradients as the rolling stock crosses the transition from flat to inclined.  My first answer was to offer three different types, as shown below; high, standard and low.

However given there may be a few different lengths, this makes for a large number of different couplings to manage.

A much simpler idea was to make the knuckle 2mm bigger.   By moving the top up by 1mm and the bottom down by 1mm all versions are covered.  The wings either side of the knuckle were also removed as they performed no real purpose.

This new design was 3D printed on sprew in the Black Versatile Plastic.  The sprew helps reduce the cost of the parts.

The Bachmann OO Class 66 has, what I consider, to be a correctly positioned NEM socket, that is, it’s in the middle of all the rolling stock I’ve tested.  The new coupling fits perfectly and doesn’t look too out of place.

Compared to a standard Kadee in another Class 66, the new coupling looks okay, even if it’s a bit deeper.

The two coupled perfectly and as you can see the new coupling sticks up and down by 1mm, ideal if the coupled item of rolling stock has its NEM socket out of place.

This coupling length is based on a Kadee No. 19. which works well for most items, although I found Hornby coaches ended up with a larger gap between them than I liked, so a shorter version will be designed soon.

For now, these are available in packs of 10, 25, 50, and 150 and you can find them using the links below.

OO NEM Dummy Knuckle Coupling (Large) x10

OO NEM Dummy Knuckle Coupling (Large) x25

OO NEM Dummy Knuckle Coupling (Large) x50

OO NEM Dummy Knuckle Coupling (Large) x150

Once the length of a shorter coupling has been finalized, to reduce the gap between Hornby coaches etc, I will share this with you too.  But now it’s back to the drawing board as I have several projects to wrap up which I’ll also share with you in due course.

Alco C-855 N Scale Replacement Lifters

Sometimes trains get damaged, I’m sure it’s happened to most of us at some time.  And there’s always that one point on a model which is more prone to getting damaged than the rest.  On my C-855 shells it’s the lifters at the rear of the model.

The C-855 has four lifting points to allow the whole body to be lifted off the trucks.  There are two in the nose and two at the rear. The nose lifters can be seen below; there’s a recess behind the hole to allow a lifting shackle to be attached.

The rear lifters are raised up on posts.  This is to keep all four lifting points at the same height.  On the real locomotive the posts would have been thick heavy metal but in N Scale acrylic they’re a little thin.  And it’s these that are likely to break if the shell is dropped.

If you can find the broken part it’ll fix right back on with a drop of superglue as this material usually breaks with a clean edge.  Injection moulded parts tend to distort when they break so fixing them back on can be harder.

But if you can’t find the part a replacement is needed so I’ve created a set of four lifting posts as the C-855B has four posts because it has no nose.

The set has two left and two right hand posts and they are all 3D printed on a ring which makes them a single part and therefore cheaper to print.  I’ve made them longer than normal so they can be shortened to the right length depending on where the break is.  As the material is hard these will not cut like injection model plastic but can easily be filed or sanded to get them to the right length.

The replacement C-855 lifters can be found here.

EMD DD35 with Body Mount Couplers – Part 3

Back in January of 2019 I shared with you my test print for an EMD DD35 with body mounted couplers in N Scale.  You can find the post here.  This week I thought you’d like to see what it looks like with a bit of colour.

The shell, as pictured below, is stark white having been 3D printed in Shapeways’ Fine Detail Plastic, also know as FUD (Frosted Ultra Detail).

With the pilots 3D printed as part of the body, the only two parts are the main shell and the fuel tank.  This locomotive will be Southern Pacific 9900.

But, as with most SP locomotives this one won’t stay this clean for long as it’s going to be weathered.

Weathering can be done in many different ways, and to many different levels.  This locomotive will be weathered with enamel paints using an airbrush, and typical for the SP it will bit fairly grubby.

The locomotive will now need a good wheel clean to remove any paint, as it always gets on them, and then it’ll be ready to run.

The DD35 kit with body mounted couplers is available here.

Bachmann N Scale 4-8-4 Replacement Gears – Part 2

In February of this year I shared with you my set of replacement 3D printed gears for the Bachmann N Scale 4-8-4, 3rd Generation.  You can find the post here.

At the end of the post I needed to make some modifications to the gears as the axels were still a little too loose on the wheels and the twin transfer gear was way too loose.  These changes were made and another set was 3D printed.

This time all the gears fitted well into the chassis, but I think I still have a problem with the twin gear as the motor struggles to drive all the gears.  Either the larger set are oversize, causing resistance between the gear and the worm, or the smaller set don’t have a deep enough trough between the teeth, which means the axel gears push the twin gear up into the worm.

With the original twin gear fitted, and all the other 3D printed gears fitted, the assembly runs smoothly.   Below you can see the axels fitted onto the wheels with the chassis plate installed.

With the entire chassis assembled I started testing the gearing and discovered that there was a bind at the same point in every rotation.  After a little adjustment I was able to get it to run much smother.  However, on reflection the next time I do this when fitting the gears to the first set of wheels, as shown above, I’ll attempt to get the gears positioned at the exact same point on each wheel, as I think it was this that caused the issue.  If, as with diesel locomotives, there are no side rods, the position of the gears is not so critical as they will find their place.  Or if there are no internal gears, simply side rods as with the HO 4-8-4, then it’s just the quartering which needs to be correct.  But as this loco has both internal gears and side rods, the quartering needs to be correct as does the gear positions relative to each other.

Below is a quick video of the chassis running with power supplied direct to the motor.

I’ll make the adjustments to the twin gears and do another test print, but in the meantime if you’re keen to get your N scale 4-8-4 back on the road and are happy to use all the other gears then a set is available here. In most cases, these 3rd generation 4-8-4 locos only need the axel gears to make a full repair as it’s the axels that split.

Once the new set arrives I’ll update you with the progress in a later post.