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.

Bachmann HO US 4-8-4 Replacment Axle Shafts & Gear

My apologies for not posting last Monday, unfortunately a loved one was involved in an accident and we didn’t leave the emergency room untill 9pm. All’s well and they’re on the mend so let’s get back to normal.

Last year, coincidently about this time, I shared with you my designs for replacement axles for the HO Bachmann 4-8-4.  You can find the post here.  This week I’ve updated the 3D printed model to include the main drive gear.

The gear is less likely to split than the axles, but sometimes it does, so a set with everything in makes sense.

All the parts are joined on a 3D printed continuous bar so they’re all one part; this makes them cheaper to print, but the bar doesn’t actually touch the parts so there’s nothing to be cut off or trimmed as with injection molded parts.  This is one of the many things which makes 3D printing great.

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

This coming weekend, 1st to 3rd March 2019, is the N Trak convention in Bournemouth, England and again it’s at The Trouville Hotel.  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.

Bachmann N Sacle 4-8-4 Replacement Gears – Part 1

Following on from last week’s post, this week is also about 3D printed replacement gears.  Although this week it’s for an N Scale Bachmann 4-8-4 Northern.

The Bachmann 4-8-4 Northern has been around since 1972 and there have been several versions over the years.  The first two, with the second released in 1975, are in my opinion rather lumpy runners but it’s the third version, released in 1982, that I’m working on and it wasn’t too bad.  However this release suffers from the same problem as the locos in my last two posts; split gears.  The loco in the image below is one of these (image from Spookshow.net) and you can see the rear driver is at a different rotation to the rest.

It’s possible that the wheel on the other side of the locomotive is in the correct position but it’s more than probable that it too is misaligned.

The chassis, as shown below, is in one piece with the motor above.  The gears sit off-center within the chassis. Each axle is powered by gears so the side rods are cosmetic but if they get out of quarter, as with the loco above, everything jams up.  The most common axles to split are the rear two as these are the first to be driven by the motor and therefore under the most stress but it’s not uncommon for all of them to split.

The original axles are asymmetric, that is to say the gear is not in the center of the axle. You can see below the splits on the axles.  This releases the friction grip on the wheels, which are simply pressed into the axles, and allows them to spin in the axles.

To start with I 3D printed a set of axles in Shapeways Fine Detail Plastic, formally known as FUD.

Compared to the original they are the same, but the inside diameter of the axle was too big, so there was no grip on the wheels at all.

So I 3D printed another set with a smaller inside diameter. I also 3D printed the other gears as it makes sense to supply a full set of replacement gears.  This includes the two idler gears and the twin transfer gear that fits under the motor worm.

All the original gears look like this.

Below are the new gears compared with the old.

Test fitting the second set of gears on the axles I found they did fit with a push and I thought that the friction would be enough to prevent them from spinning on the wheels.

To fit the axles properly the chassis plate needs to be fitted between the axles and the wheels.  The chassis plate positions the wheels and transfers electric from the metal wheel to the motor; there’s one on each side.

This is the tricky part.  When the chassis plate, axles and wheels are fitted to the chassis the wheels must all be at the same position.  The position of the axle on the wheel can also affect this as the teeth on the gear need to mesh with the idler gear teeth; if it’s off it will force the wheel to rotate slightly as the teeth mesh.  I reckon they had a jig for doing this in the factory.

The wheel sets on the other side must also be fixed so all four are at the same rotation but quartered compared to the other side.  To find out what quartering means and why it’s done see the post from two week’s ago here.

On test running, the motor drove all the gears and everything rotated etc but it was lumpy.  On inspection one of the wheels was not as well aligned as it should have been and as I attempted to rotated it the wheel spun in the axle. The new axle has not split but it means the diameter of the hole in the axles is still too big and needs to be smaller giving a tighter grip on the wheels.  I was reluctant to draw the hole too small to start with because if it’s too small and the wheel is forced in it will probably split the new axle.

Next I’ll make the necessary adjustments to reduce the size of the hole in the computer model and test print another set.  Although it fitted okay I’m also going to make a small adjustment to the twin transfer gear as it was also a little too loose.  When they arrive I’ll share the outcome with you.

Replacment Gears For A USA Trains G Scale 0-4-0

In a similar post to last week I have another replacement gear to share with you.  This time it’s much larger and for a G Scale 0-4-0 Pennsylvania 20-Ton Diesel Locomotive; made by USA Trains.

Despite being a small locomotive it’s a big model, G scale has a model ration of 1:22.5, and is heavy.  This also means that the motor has lots of power and the transmission needs to be able to withstand the forces applied.

Both of the axles are powered from a worm gear on each end of the central motor. The worm gears drive plastic gears which also form the axles and isolates the two metal wheels from each other.  As you can see in the image below the plastic axle has split.  This means the motor drives the gear which turns but the gear doesn’t turn the wheels.

As replacement parts for this locomotive were not available I drew one exactly the same size as the original and 3D printed it in Shapeways Fine Detail Plastic, formally known as FUD.  As I’ve said in previous posts this material is ideal for gears as it’s hard-wearing.

The original gear was also a bit mangled as the softer plastic tends to get damaged by the metal worm gear when under heavy loads such as starting and stopping suddenly.  The new gear with the harder plastic can withstand this without being damaged.

The axles have grooved ends to enable them to grip the inside of the plastic axle.  With some evenly applied pressure they can be pushed into the new axle.  In the image below they need to be pushed in a bit further but you can see the grooves in the metal.

The locomotive motor is in the box between the axles and when the lid or base is screwed on the new gears are pressed up to the metal worm gears.  The motor box is not connected to the body but clamps to the axles which sit in sprung axle boxes.  This allows the locomotive to navigate bumpy track and gradient changes without losing traction.

Once the motor base is replaced the locomotive is ready to go back out onto the railroad.

The replacement drive gear can be found here.

They are also available in a pair here.

Next week I’ll have even more 3D printed gears to share with you but this time it will be for  N Scale.