OO Gauge Fixed Link Wagon Couplings Revisit – Part 1

In March of 2017 I first introduced my OO gauge fixed link couplings for UK wagons, you can find the post here, and they developed into a range of couplings to suit both 3 Link and Instanter couplings.  They’ve been doing well but there have been a few issues so a revisit to the design is required.  In this post I’ll be showing you the first steps.

The couplings, as shown below, are designed to fit into NEM standard pockets and form a permanent link between two wagons whilst retaining the look of a 3 Link and Instanter coupling.

And I think they do this very well.

At the time, an important design feature was the ability to add some flexibility onto the coupling to allow it to navigate corners.  I considered the main part of the coupling too stiff and was worried it would pull trucks off the rails on corners.  A solution was achieved through a flexible section; this was covered in the second post which can be found here.  But it’s this flexible section which has caused the issues.  The material used for the couplings is Shapeways’ Smooth Fine Detail but, as you may have read in other posts, it is brittle and the couplings tend to break at the flexible section, especially when handling several wagons joined together off the rails.  They tend to break here as it’s the part of the coupling with the least material.  One thing I also noticed is that the direction of the print also had an effect on the strength.  The original couplings were printed loose and often standing up on end.  This meant each layer of 3D printed material had a small surface area to bond with the last.  Printing the couplings laid down significantly increased this area and therefore the strength.  Since I made the alteration to print the couplings as a group, see the third post here, they’ve all been printed laid down, but they could still benefit from more strength.

As it turns out the couplings do have some flexibility and the required amount of movement is not great so I’m going to try some 3D printed couplings without the flexible section to see how they do.  Below you can see the revised couplings on the right.

The taller couplings had a much larger flexible section and coincidently it was much stronger; it was the flat coupling which broke more than any others.  But I’m going to try them all.

I’m also going to do some experiments with some of the other materials.  Once I have samples in hand I’ll share the results with you.

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.

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.

Bachmann HO US 4-8-4 Replacement Axle Shafts & Gear – Update

This week I have an update for the HO US 4-8-4 Replacement Axle Shafts & Gear set.

It appears I made a mistake with the hole diameter in the main drive gear, my apologies to anybody who has purchased one. The hole was larger than the hole in the axles meaning the rear wheels would not stay in the gear.

The good news is this has now been rectified and the current model on Shapeways is correct.  The parts are also available separately and they can all be found in my Shapeways Shop or via the links below.

Axles & Gears

Axles Only

Gear Only

However that doesn’t help anybody who has already purchased the gear set with an oversized hole. For those who did I will replace the drive gear for free. Please get in touch through the contacts page or email me directly at jamestrainparts@yahoo.co.uk and include the date which you purchased the kit.

Replacement gears seem to be in great demand at the moment and next week I should have some more to share with you for some UK OO locomotives.

EMD DD35 With Body Mount Couplers – Part 2

In last week’s post I shared with you my design and 3D print of an N Scale EMD DD35 with body mounted couplings.  You can find the post here.  In this week’s post I’m going show how well it worked.

The new EMD DD35 shell, as shown below, is sat on a modified Bachmann DDA40X chassis which has been shortened and had its pilots cut off.

The 3D printed pilots have pockets to receive a Micro-Trains body mount coupling.  This can either be a Type 1015 (Short shank) or a 1016 (Medium shank) and there’s a 3D printed hole in the pilot to receive the mounting screw.

I’ve used the 1016 as the extra length will help with the curves.  Because the coupling rotates slightly off of the screw, the longer arm will mean the coupling can swivel closer to the center of the tracks, which is the ideal location.  The further away the coupling gets from the center the greater the risk of it pulling the train off the tracks.

On our layout ‘Solent Summit’ the tightest radius is in the yards at 16″.  Below you can see the new DD35 coupled up to two originals with the truck mounted couplings.  The three run around the 180° bend with ease and there’s still slack in the couplings.

The middle DD35 has the standard McHenry couplings as supplied by Bachmann.

The McHenry sits a little high compared to the micro trains but the connection is good under tension.  Because the couplings naturally spring straight they will not couple up on the bend, they are way too far out of line, but they don’t seem to be affected once coupled.

In order to test the couplings properly I assembled a train powered by a GP35, GP20, GP7, the new DD35, a dummy DD35, a original powered DD35 and another GP20.  All followed by 42 cars and a caboose.

Apart from being lots of fun, the idea behind all the motive power, some 23,000 horsepower with the new DD35 in the middle, was to see how the couplings worked with pulling and pushing forces. The train, comprised of a lot of older rolling stock, had a lot of drag which added to the draw bar pull.  The big train made its way around the layout, through s bends and the 16″ radius yard curves, several times with no problems at all.

But as the other DD35s had truck mounted couplings, the GP locos being short and the box cars in the train also being short, all their couplings were close to the center of the track.  To make this a decent test the new DD35 needed to be connected to other long locomotives and freight cars with body mounted couplings.  And luckily there was one on the layout.  The train in the video below, built by my fellow modeller Chris, has two Kato SD80MAC locomotives pulling a long line of Atlas 85′ trash cars.

Both the SD80MACs and the trash cars have body mounted couplings so they will swing out further on the bends.

The trash car has Atlas Acumate couplings which as you can see work well with the Micro Train couplings.  There’s some swing on the Atlas coupling but it’s rotating about the end of the car, not the truck center point.

The Kato coupling seemed a little low, or the DD35 body may have lifted and I didn’t notice untill I got home and looked at the photos but it didn’t cause an issue.  The Kato coupling rotates about the end of the loco.

Leaving the East yard the train runs through an s bend, around at tight corner and out onto the layout and the DD35 with its body mounted couplings did this with ease.

It’s possible the shorter 1015 coupling will also work and if the tightest curve is 18″ or 20″ radius then it certainly will.  But I think 16″ is about the smallest radius for the new DD35.

I have a few other things to check and then I’ll make the new DD35 shell kit with pilots and body mounted couplings available to buy.

EMD DD35 With Body Mount Couplers – Part 1

This week I have a modified shell to share with you for my N Scale EMD DD35 project.  The new shell option incorporates body mounted couplers rather than truck mounted.

My DD35 3D printed shell is designed to fit onto a modified Bachmann DDA40X chassis which has truck mounted couplings.  Only the shell and fuel tanks are 3D printed, the trucks and pilots come with the chassis.  You can find the kit here.

The real DD35, and the DDA40X, has body mounted couplings, or rather chassis mounted, which allow the trucks to rotate freely under the chassis.  I originally decided to leave the truck mounted couplings on the model, simply because of the length of the locomotive.  As it’s so long, body mounted couplers will cause a problem with tight curves.  As the locomotive navigates the tight curve the coupling moves too far away from the center of the tracks and can pull the connected rolling stock off the rails or derail the locomotive. That’s also why Bachmann built the DDA40X model the way they did.

But some layouts have larger radius curves than others and I was asked if I could produce an extra part to allow body mounted couplers to be fitted.  So I did and they looked like this.

These came in the form of a pilot section with a cutout for a body mount coupling which, with a bit of modification, could be fixed to the underside of the shell.  You can read my post about them here and they can be found here.

But the ideal situation is to have the pilots 3D printed as part of the shell and that’s what I’ve done as you can see in the renderings below.

The new pilot section has the pocket and screw hole for Micro-Trains body mounted coupling.  The problem comes with fitting the new one piece 3D printed body section onto the chassis which is now too long.  As the pilot sections tuck under the chassis this makes it impossible to simply drop the body down onto it.

The original modified chassis, as shown below, has the pilots attached to the trucks and the chassis stops roughly where the pilots start.

To make the new shell fit, the first thing to do is remove the existing pilots.  These are held on with two screws which release the coupling and pilot.

The pilot mount is plastic and projects from the truck frame.

This needs to be cut off and that can be done with pair of side snips.

The chassis also had to be shortened by filing the ends.  From point to point the chassis needs to be 150mm (5.906″) long in order to fit inbetween the new pilots on the 3D printed shell.

With the chassis reassembled it now looks like this.  I also filed a chamfer on the four corners to ensure the shell was a good fit.

One other modification I made was to file off the four locating bumps on the sides of the chassis.  These normally located the DDA40X shell which has matching holes on the shell.  As the DD35 shell doesn’t have these holes and is held in place by the length of the chassis they are not required.  They will also cause the shell to spread if left in place.

The new shell, which is 3D printed in Shapeways Fine Detail Plastic, fitted onto the chassis and clipped into place, as did the fuel tank.

Once the shell has been painted I will fit the body mount couplers and get some videos of the DD35 traversing curves with its body mounted couplings. I’ll share that with you in another post.