Lima HST in EM Gauge

This page attempts to document the full length Cross-Country Lima HST set seen on South Junction at the recent Open Day.  The bodies and running gear are entirely Lima, although the TS standard class interiors are modified Jouef and replacement can motors have been fitted in the Lima power bogies.  The carriages (but not the power cars) have received considerable additional ballast using offcuts of code 4 lead sheet.

Can Motor Upgrade

HST motor
Whizzy Replacement Motor

 

The replacement can motors are excellent and are a direct replacement for the Lima items.  The power cars have similar performance, and it can be observed that in normal running half of the cars are being pushed and half pulled.  The motors are very free running, and the Lima HST bogies being of a pancake design will freewheel once moving which is an advantage on a long train with both ends driven.  Whilst the top speed scales to a lively 180 MPH, the slow speed performance is very acceptable no doubt aided by all that weight.

This is the web page for the Lima replacement can motors that were used:

http://diesel-trains.co.uk/Lima_replacement_motor_kits.html

Wheels and EM conversion

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EM wheel conversion

As a long term member of the EM Gauge Society (EMGS) the re-gauging method for the power cars was lifted from the EMGS manual sheets for the Lima model of the GWR Railcar.  This ‘old skool’ EM gauge conversion used the 2.5mm/2mm shouldered axles from the EMGS with 12mm steel wagon wheels (3 hole disc) as these were to hand.   A shorting wire was used so that the efficient Lima current collection via the axles could be retained.  A plastic disc and spacing washers were required to keep the gears nicely meshed.   The excellent and inexpensive Colin Craig etched brake discs were then applied.   With the tyres polished up these wheels look good and work well.   The power bogie is the standard HST bogie with two stage reduction given a good clean and light lubrication.

For 00 layouts replacement steel wheels would still be a good idea, but it would be necessary to improvise a 00 gauge version of the shouldered axle perhaps using a 2.5mm brass sleeve of the correct length on 2mm axles.

Drop in replacement wheelsets are of course available from Ultrascale.

The carriages used Black Beetle style N/S wheelsets available from Branchlines with the non-standard Lima 25mm axle length.  The flanges on these wheels are very fine, but they are exceptionally true running and the performance of the coaches is faultless.

LED head and tail lights

There are lots of good things about the LIMA body, and one of them is that it has holes/light tubes for all the relevant lights.  The 2mm red LEDs fit in slightly enlarged holes in the LIMA body with the white/yellow LEDs mounted just behind them shining into the clear plastic plugs of the LIMA headlight moulding.  (The light tubes for the tail lights have been shortened to enable this).

South Junction is an analogue (DC) layout, and it is much easier of course to arrange all this for DCC in which case the Model Rail article (October 2006 edition) on HST lighting is worth a look and most of the below can be ignored – lucky you!

The DC LED lighting uses the LM334Z current control integrated circuit (IC) as detailed here: Constant brightness lighting using the LM334Z

These super little ICs light the LEDs at low voltages whilst limiting brightness at higher voltages.  Yellow LEDs have been used for the marker lights and a white LED for the headlight.  To get them ALL to light it has been found necessary to provide three separate circuits for the headlights, marker lights and tail lights.   White LEDs light at a higher voltage than yellow LEDs so do not sit well on the same circuit when wired in parallel.

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Overview of wiring

Three lots of PCB strip have been used:

The first (two tracks) gathers together the pickups and motor connections and is used to mount an interference suppression capacitor from the redundant Lima motors.  This capacitor also reduces flickering of the reverse directional lights through what is suspected to be back EMF following tiny interruptions in the pickup voltage.  Two wires connect this to:

The second board (nine tracks) mounts the three LM334Z ICs together with the resistors that control the current.  Five wires (common return on head and marker lights) connect this to:

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LED arrangement

The third board (four tracks).  This is located in the nose using the tail light LEDs.  Forget any idea of common return for tail and head lights – experience says that it cannot be done with these ICs.

Light spill is a major issue with this type of LED and also with the yellow plastic body.  Lots of black paint is required on the LEDs, inside the nose and even round the transparent light tubes in the nose to reduce it to an acceptable level.

Couplings

The Lima couplings have been removed from the bogies and replaced with Kadee no. 5 with the boxes fastened to the floor of the carriages which has been slotted for fine tuning of coupling length for clearance on curves.  South Junction has a minimum radius of 3’6″ and for tighter curves one of the proprietory close coupling systems would need to be used.  Because the HST is a fixed formation the couplings have been mounted at buffer beam height with the operating tails well above the rail head.

Cab Detailing

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Cab interior

With a lot of chopping about and with scratchbuilt full size seats the latest Hornby cab units (Peters Spares) were fitted with Bachmann driver and secondman at one end.  Sadly the current LED lighting solution has forced these to be omitted at least for the moment.  To return the cab detailing it would be necessary to change to surface mount LEDs as these will fit more easily into what is a fairly confined space in the nose.  Only white and red surface mount LEDs seem to be available, but it should be possible to dim the marker lights with some dabs of yellow paint on the LEDs.  It is understood that surface mount LEDs excite at a lower voltage/current so that a different resistor may be required for the current control chips, but as the head and marker lights would now be of the same type only two ICs would be needed at each end.

Summary and Notes

This is an excellent option for those wanting a full length finescale HST as there is much that is good about the Lima model.  Lima production appears to have been very consistent and it is possible to put together a full length train from a variety of secondhand sources with a very consistent look and finish.  Perhaps not surprisingly it is the humble TS that is hardest to source since four or five of these are needed for each full length set.  An issue with the Lima TS is that it has first class (2+1) seating hence the use of adapted Jouef 2+2 seating units.  Luckily there appears to be no shortage of donor Jouef TS coaches!

The restaurant car in a cross country set should of course be a TRSB with four full size windows/seating bays.  For consistency of appearance this will be addressed by modifying a Lima restaurant car to suit.

The Lima glazing has a satisfactory and consistent tint and therefore appearance, but there is no doubt that the flush glazing system available from Shawplan is a worthwhile upgrade that really captures the look of the real thing.

Detailed set formations from the early days through to 1982 can be found in Modern Railways Pictorial Profile:1 published by Ian Allen.

The author has no connection with any of the suppliers mentioned other than as a satisfied customer.

 

 

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