Fixing a Mainline OO Gauge J72

The Mainline J72 0-6-0 has been around for many years; it first appeared in the Mainline catalogue in 1976, and it was also my very first electric model train.  However this locomotive suffers from the same problem as most of the other Mainline locos; split gears! So in this post I’ll show you my solution for fixing this problem.

The J72 has a motor, which fills the cab and drives the rear axle.  The two forward axles are driven from the side rods so only the rear axle has a gear.

The wheels and side rods are handed, that is to say they are not the same on each side but mirrored.  If you look closely you can see a small section of metal above each pin where the side rod connects to the wheel.  This is to represent the oiling point for the bearing which the real locomotive would have had.  It also helps us to work out which side the wheel sets go.  The side rods are also in two pieces and the two parts connect at the centre wheel.  The rear side rod fits over the front.  It’s important to get this the right way around as the axle spacing is different with the front two being closer together.

The original rear axle with the gear and two regular axles are made from a black injection modelled plastic and looking closely you can see they have all split.  This causes the wheels to spin freely in the axle and consequently jamming the side rods.

To solve the problem I have designed a 3D printed gear and axle set to be a direct replacement.  These have been 3D printed in Shapeways Fine Detail Plastic because of the material’s accuracy and toughness.

They are all 3D printed on a solid bar to keep them all together but the axles are loose. When the bar is cut they will fall off.

The original main gear I designed was a direct copy of the Mainline part, but because of the recess to reduce the amount of material used, this caused a week spot in the 3D printed gear.  Although the Fine Detail Plastic is tough, it’s also brittle at thin areas.  When the wheel was pushed into the gear it broke. So the gear was redesigned to be a bit thicker and the recess was omitted.

When fitting the new axles it’s vital to get the quartering correct.  A description of what this means can be found in my post about ‘Bachmann (Mainline & Replica Railways) Split Chassis Axle Repairs‘.

It’s also important to get all the wheels aligned, as shown below.

The new axles will press-fit onto the wheels and should be pushed all the way on.  I get the axle started then double check it’s at the right position before pushing it all the way.  It’s possible that the axles may have some 3D print residue left inside.  This can easily be removed by reaming the hole with a 1.9mm drill.  If you use a larger one you’ll open the hole up too much and the axle won’t grip the wheel.  It’s also worth double checking you have the geared axle on the right wheel set and the right way around as it’s not symmetrical.  In the image below you can also see the thicker gear from the new design.

Assuming the quartering is correct the repaired wheel sets should drop into the chassis returning it to a working locomotive.  If, once all reassembled, the locomotive lurches or makes a thumping sound at the same point in every wheel revolution then the quartering is out on one of the wheels.  This should be visible be examining the wheels; one will be at a slightly different rotation to the others.  It’s possible to adjust this without taking the locomotive apart.  Hold the correct wheel tight with your fingers and carefully rotate the wheel on the other side,  It should slip in the axle.  Only make small adjustments and retest each time.

The new set of axles & drive gear for the Mainline J72 is available here.

In next week’s post I’ll have part two of the post for the replacement gears for the Bachmann N Scale 4-8-4.

An Upcoming Show

In this week’s post I had hoped to bring you some news on the new 3D printed parts I’ve been working on.  But due to a mixture of design issues and time delays they’re not ready yet so I’m going to make this week’s post nice and short by simply letting you know about the next exhibition I will be at.

This coming weekend I and the rest of the team from ‘Solent Summit’ will be at the Crawley Model Railway Exhibition in West Sussex with part of our large modular layout.  The show is on Saturday and Sunday at Tanbridge House School, Guildford Road, Horsham, West Sussex, RH12 1SR.  You can read more about the show here.

With a little luck I’ll have some of the new 3D printed projects ready to share with you next week.

Going Uphill – Part 2

In last week’s post I shared with you plans for my new module for our layout ‘Solent Summit’ based on the Tehachapi Loop.  In this week’s post, as promised, I have some photos of the completed track work and the first trains to run through the loop.

The track bed is laser cut to ensure the loop ends in the right place and to help keep the gradient correct.

The track bed is supported on timber posts which have a bevel cut on top.  This was to ensure the track bed didn’t level out at each support.  To add a complication there are three locations where the twin tracks cross board joints.

The actual incline starts just after the line passes under itself and stops just before it passes over itself.  The real railroad continues to climb as it makes its way up Tehachapi Pass but as our line also has to come back down I needed to level it out as it runs out of the back of the module.

I still need to add a few more supports under the track bed and to do a little more work to smooth the gradient out but for testing purposes the loop is ready.

For those of you who are familiar with our layout you’ll know we like to run long trains so what better place to start than with a long coal train?  Approaching from the left is a pair of Kato SD70MAC’s with a train of Kato bethgon coalporters and a banking SD70MAC behind.

As I described in last week’s post, the loop is also a passing place.  To make the loop modular so it can be transported, the passing place has been made shorter than the real one, but it still allows for a 13′ (in N Scale) train to wait while another train passes.

The first pass we had was an SD40-2 with double stack train being passed by an auto-rack train.

The other reason I wanted to do tests with these trains was for height.  The double stack and auto-rack cars are some of the tallest on the modern railroad and I wanted to see how they looked in proportion to the loop.  The real loop climbs some 77′ before it passes itself due to the considerably larger radius.

The loop on the new module only climbs 33′ but as you can see below there’s still lots of clearance between the upper and lower lines and I think it looks good.

Throughout the day we tested many trains through the loop with trains heading down on the inside and trains heading up on the outside.  This is because the larger radius on the outer track makes for a slightly reduced gradient.  Coincidently, we also operate right road running for passing so this fits in with the rest of the layout.  Below two SD60s take a sulphur train down the line.

The Tehachapi Loop was built by the Southern Pacific Railroad so of course we had to try the iconic SP cab forwards with a Pacific Fruit Express (PFE) train.

I was amazed how long trains, such as the Santa El Capitan, which as you can see below normally stretch out on the layout, seem to disappear in the length of the loop.

Of course several of our trains did have an issue with the gradient; combined with the drag factor of the curve some of the heavy freight cars in short trains with just one locomotive ended up wheel spinning and stalling.  The answer is to add some more power and below is a video of how the Southern Pacific moved loaded coal trains over the loop.  I think 15 locomotives will do it!

The next stages are for me to start looking at the scenery, turnout control and signalling for the module, a lot of work still ahead.

This coming week I’m taking some time to work on my stock of trains and give them some much needed attention to several of the running issues I’ve had at shows lately. This is downtime for me, getting back to my hobby so I won’t be posting, instead I’ll just be enjoying working on my trains!  So in a fortnight’s time I hope to bring you some news on some more 3D printed parts.

Going Uphill – Part 1

This week I’d planned on bringing you some more 3D printed gears but the delivery’s been delayed so I haven’t received them yet.  So instead I thought I’d share with you my latest creation for our group’s N Scale layout, ‘Solent Summit’.

‘Solent Summit’, which has appeared on my website many times over the years, is a modular layout built by members of the Gosport American Model Railroad Group.  Back in 2015 I built the Warsash ‘Y’ module which incorporated a large scratch-built timber trestle.

Here’s the ‘Portland Rose’ running over the trestle at the Andover show in 2016.

Not wanting to do anything less spectacular I set my sights on the famous US railroad landmark, the Tehachapi Loop.

The Tehachapi Loop is in Kern County, Southern California.  It’s on Mojave Subdivision, the line which connects Bakersfield to Mojave, and runs through the Tehachapi Pass over the Tehachapi Mountains.  The line is currently owned by the Union Pacific Railroad but was constructed by the Southern Pacific between 1874 and 1876.

The route up the Tehachapi’s was challenging and the railroad wanted to limit the gradient as best they could.  At one location, between Woodford and Marcel, which was christened ‘Waylong’ after W.A. Long, who was the Southern Pacific District Roadmaster, the route simply became too steep.

To overcome this a loop or helix was constructed at a steady gradient of 2.2%, which lifted the line by 77′ before it carried on up to the pass. The actual loop is 0.7 miles long, In the screen shot below from Google Maps you can clearly see the loop.

There are other loops like this in the US; on the former Western Pacific route through the Feather River Canyon is the Williams Loop, but what makes the Tehachapi Loop interesting for me is that it’s also a passing point.  Just after the line passes under itself, climbing up the hill it splits in two, and then rejoins itself further up the line creating a passing place.  Shorter trains can be waiting in the loop, crossing above the line below, while upcoming trains pass under the waiting train and, if they’re long trains, actually cross over themselves while passing the first.

The Tehachapi Loop has been modelled many times and at the Golden State Model Railroad Museum there’s a great example of it in N Scale.

However the GSMRM is a fixed layout with space, Solent Summit is not.  But I like a challenge and plans were drawn up, with a bit of modeller’s license, to create a 5′ by 4′ module which would incorporate the loop at a sensible radius and give a decent height increase without making it too steep.

The idea is to create a corner module with the train entering from the left and exiting from the top.  This should give optimum viewing for the loop.  The result, as shown below, gives a rise of 2.5″ at a gradient 2.2%, on the inside track, which has a radius of 20″.  The outer track, which has a bigger radius, has a gradient of 2.1%.  This plan also creates a passing point which can hold a 13.5′ long train.

Although the gradient matches the real loop, the elevation gain is only equivalent to 33′ as opposed to the 77′.  But what goes up must come down and for us 2.5″ is enough.  The other issue is the radius.  At 20″ it looks sensible but when you factor in the weight of a 25′ train navigating a 450° curve the risk of it pulling in on itself is high.  But the only way to find out is to try it.

The baseboard, being bigger than our normal 12″ wide construction, needed a little thought as it has to be easy to move, but strong as well to protect the layout in transit.  All of our modules are in pairs so when put together they form a solid box with the layout inside.  The Tehachapi Loop module would be the same consisting of two 2′ by 5′ modules. The back scene on the short side would need to be removed for transport.

The back scene also forms the sides to the box, so the front section needs the extra pieces shown in red to be bolted on to form the box.

The lowest level, where the line enters the module would be flat solid timber. The track bed carrying the tracks up will be laser cut and supported on timber posts. This track bed is made from 6 sections, as shown below, allowing it to be cut from one piece of wood.

The actual laser cutting was done by Model Railway Solutions.

With baseboards constructed and the track bed cut out it was time to start thinking about setting out the parts.  Below you can get a rough idea of the size with a UK Mk1 coach sat on the loop.

Next week I’ll show you what the loop looks like with all the track work complete and I’ll have some pictures from the first test run to share with you as well.  The 3D printed gears should have been delivered by then so I’ll get back to them the week after.

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.

N Trak Date Correction

To start with this week, I need to make a correction to last week’s post.

The N Trak convention in Bournemouth was not last weekend, it’s this coming weekend; 8th to 10th March 2019.  However it is still at the Trouville Hotel.  My apologies to anyone who went down last weekend.  You can read a bit more about the 2017 convention here and the 2014 convention here.  I’ll be there over the weekend if you’re in the area and want to come by and say hello.

As for a post this week I’m going to have to skip to next week as I’m rather behind and I need to concentrate on the projects on the bench.  But I’ll be back next week with some highlights from the N Trak convention.