No.100 Bachmann GWR 4-4-0s and gradients

I was asked this weekend how both my Bachmann Dukedog (9017) and my City performed on gradients. Straight out of the box, the answer is 'With difficulty'.


Bachmann Dukedog (9017) on local train

9017 is a recent addition to the layout and after marvelling at the detailing and the super smooth performance I was prepared to overlook the fact that my model seemed incapable of hauling any load uphill. 9017 was relegated to shuttling between two stations on my branch line - on the level.
I would investigate further.

The front bogie detail

Standing the locomotive on a flat surface highlights the likely problem. I haven’t counted the rivets but I am guessing that Bachmann have made a very good attempt at modelling the outside frame to the front bogie with the result that the clearance between the bogie and mainframe is really rather tight.

Underside of 9017 showing the mounting for the front bogie

Removing the bogie reveals the mounting boss on the underside of the chassis.

9017 bogie with Bachmann fixing bolt, spring and washer

The bogie is held in place by a threaded bolt which also carries a spring and washer. In use the spring and washer are compressed between the top of the bogie and the mounting boss. With my locomotive standing on a flat surface I was unable to press the front of the engine down on to the bogie suggesting in my mind that front of the chassis was in effect resting on the bogie and that in all probability the front driving wheels were being lifted from the track. To test the theory I reattached the bogie minus the spring and washer. Yes the locomotive would now press down onto the bogie. However the engine appears to be rather front heavy and without any support over the bogie the engine has a tendency to tip forwards lifting the rear driving wheels.

Plan B – shortened spring on the right

I think the bogie still needs some springing and after a little trial and error I came up with a shortened spring cut from a ball point pen. I also removed the washer – I don’t think there is space for it.
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Success, 9017 would now haul two old Mainline B Set coaches all the way up my nominally 1 in 40 grade branch line.


 

For the record, the B Set is made up from Mainline coaches fitted with metal wheels and close coupled with Bachmann Mini (long) couplings using the existing fixings.
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I had wanted a model of City of Truro for some time. Back in the 1980s I had started to add wire handrails to an Airfix kit. I had also purchased a spare Tri-ang bogie from Lord of the Isles for the project. 
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Back in 2010 when City of Truro became available from the National Railway Museum it was just a question of timing and how to break the news to my wife.

City of Truro – kit of parts

I think City of Truro is a superb model and it glided around smoothly on the level. It did not like my ‘up and down’ layout. However when not ‘posing’ in the shed yard it substituted for my 2251 on the branch line hauling a couple of coaches.

Underside of the City showing the mounting for the front bogie

Bachmann have used the same construction pattern for both the City and the Dukedog.

City bogie with Bachmann fixing bolt, spring and washer

To improve haulage capacity I would reduce the spring load from the bogie. There appears to be more space between the underside of the City chassis and the top of the bogie, compared to the 9017 and I have retained a washer.

City - shortened spring on the right

I am pleased. City of Truro will now handle four coaches, both Bachmann Mk1s or Colletts, taking in the 1 in 60 gradient on the mainline and the 1 in 55 gradient on the reversing loop with only a small increase in power required from the controller to get up the slopes.


To answer a specific question the load was increased to five Bachmann Mk1s. With lots of wheel slip it was ‘just’ possible to restart this increased length of train at the top of the 1 in 60 grade. However four coaches looks in keeping with the engine and that will be its limit on my layout.

Minus the keeper plate

For those of you who have not looked inside the City (or the Dukedog) the wheels are all geared like on a motor bogie. 9017 even includes brass bearings. I am guessing that this arrangement will stop rough running due to faulty quartering.

Wheel collectors

I have included a view of the copper collectors. The 4-4-0 wheel arrangement, particularly with large driving wheels like on the City seems to me to be rather sensitive to how the chassis is ‘set up’. If the copper collectors are not all equally sprung there might be a temptation for the body of the engine not to be perfectly aligned with the track. My City had a tendency to swing from side to side at the front, which was accentuated when the spring load was reduced. I carefully rotated the front wheels, 45 degrees at a time noting the crank position and measuring the distance across the flanges. The measurements varied between 14.85 and 15.05mm. Gentle pressure squeezing the wheels together at the widest point seems to have been effective at reducing the problem.

City of Truro on the mainline

Again for the record the Bachmann Collett coaches are running on metal wheels and are close coupled by repositioning the original couplings slightly inboard. The corridor connectors are fabricated from black cartridge paper as described elsewhere on my Blog.

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