FCAF Garratt No 2

Shaun McMahon’s Modifications to FCAF Garratt No 2

Shaun McMahon provided the following information on past, current and planned modifications to FCAF locomotive No 2 now named Ing L.D. Porta.  Shaun was responsible for overseeing its rebuilding and “modernization”. (See bottom of page for questions and answers)


STAGE 1 – 2001/2002

  1. Replaced boiler.
  2. Modified position of boiler.
  3. Foam height meter.
  4. Installed fusible plug.
  5. Fitted second water gauge to backhead.
  6. Improved ergonomics.
  7. New live steam pipes – enlarged section, streamlined.
  8. New exhaust steam pipes – enlarged section, streamlined.
  9. New live steam branch pipes (Y piece).
  10. New exhaust steam branch pipes (Y piece).
  11. Lempor exhaust manifold.
  12. De laval blower.
  13. Lempor chimney.
  14. Modified cab structure.
  15. Replaced wheelsets.
  16. Replaced axles.
  17. Replaced axleboxes.
  18. Replaced axlebox roller bearings.
  19. Replaced rod end roller bearings.
  20. New design of drive crank – replaced.
  21. Replaced crank pins.
  22. New design of eccentric crank – replaced.
  23. Replaced eccentric crank pin.
  24. Modified eccentric rod ends to housed roller bearings.
  25. Fitted proportionally fed and extended mechanical lubrication system.
  26. Insulated cylinders and valve chests.
  27. Insulated live steam pipes.
  28. Insulated exhaust steam pipes.
  29. Insulated between the frames box section.
  30. Replaced piston rings.
  31. Replaced valve rings.
  32. New fuel tank.
  33. Modified front and rear water tanks – greater capacity.
  34. Electric lighting – headlamps, motion, cab, injector.
  35. Pedal operated, bi directional air-sanding gear.
  36. New burner.
  37. New panplate.
  38. Brick arch and refractory.
  39. Burner atomizing steam superheated.
  40. Steam sampling system.
  41. Improved climbing handles and steps.
  42. Modified smokebox door.
  43. Test instrumentation.
  44. Flange lubricator system.
  45. Rail cleaning jets.
  46. New injectors x 2.
  47. Balancing of reciprocating components.
  48. Modifications to air pump – insulation.
  49. Carried out sealing repairs to cylinders so as to cure leakage.


  1. New fixed pilots as per Camila design 2001.
  2. Extended drawbars to suit 1.
  3. New snowplough x 2.
  4. Fitting of Rio Turbio screw reverser.
  5. Modify RH cab side so as to accommodate 4.
  6. Final modifications to combustion system as required from testing period 2002/2003.
  7. Valve gear overhaul.
  8. Repaint in modified livery.
  9. Fitting of additional testgear.

The work carried out at stage 1 should allow us to obtain some 22,000 km from the current driving wheels before they begin to break up in the same way as the originals did. This allows us some 3 operating years in order to finalize all design work for the stage 2 modifications and even time to prepare the components for fitting with the engine remaining in traffic rather than manufacturing and fitting as has been the case up to date. Likewise it would be convenient to use the allocated time in order to design the new components for Camilla stage 2 work and the new locomotive LVM 803 so that manufacturing can also take place in parallel at designated factories and workshops so as to reduce costs.

STAGE 2 – 2005/2006.

  1. Modified boiler in order to increase efficiency by application of high degree superheating. Use existing barrel in order to reduce cost, replacing firebox with round corner Belpaire type, tubeplates and adding a superheater along with superheater booster and roughened smoke tubes.
  2. Additional firebox, barrel and smokebox lagging so as to further increase efficiency.
  3. Feed water heater – fit in front of chimney, extend smokebox so as to accommodate such.
  4. Feed water pump.
  5. New design of unit pivot based upon known designs in daily service (i.e. improved NGG 16 design).
  6. Modified suspension – compensated.
  7. New design of piston.
  8. New design of multi ring, lightweight, articulated piston valve.
  9. Cylinder rebore.
  10. New valve liners – modified.
  11. New cylinder and valve bodies to be fitted if material testing of originals reveals sub standard material was used during manufacture. Opportunity to be taken to redesign valve chest (larger volume).
  12. Fitting of new adjustable shoes and wedges to axleboxes.
  13. Modify and rebuild brake gear.
  14. Modify handbrake arrangement.
  15. Fit steam brake.
  16. Redesign and manufacture new driving wheelsets, these should allow for proper tyring standards and integral balancing.
  17. Redesign motion and valves so as to incorporate lightweight reciprocating parts of correct section and geometric accuracy.
  18. Check and revise as required the alignment of the power unit frames.
  19. Reinforce power unit frames as required.
  20. Structural modifications to engine cradle as required.
  21. Modifications to exhaust system as a result of altering the gas flow cross sectional area in 1.

S. McMahon
Technical & Technical Projects Manager
Tranex Turismo S.A.
2nd February 2003.



Photos below show FCAF No 2 before and after modification

The photo above shows FCAF No 2 (then called “NORA”) in its original as-built condition c.1999.  Standing beside the locomotive is Ing L.D. Porta after whom the locomotive was renamed following its rebuilding (below).  At around this time, Porta and McMahon undertook steam leakage tests on this locomotive and their revelationary conclusions are recorded in the final paper incorporated in Camden Miniature Steam’s book “Advanced Steam Locomotive Development – Three Technical Papers“.

The issue of steam leakage is reported elsewhere on this website – see “Steam Tightness” page in the “Principles of Modern Steam” section.

Shaun McMahon describes the above illustration as follows:The lower photo (above) shows FCAF ‘KM’ Class Garratt locomotive No.2 ‘Ing. L. D. Porta’ at the head of a service train about to depart from Estacion fin del Mundo on Sunday 12th January 2003.

Of interest in this view are the highly insulated live steam pipes and throttle valve, foam height meter situated in front of the dome (insulated), steam sampling condenser feed pipe leading down to from the dome to the front water tank, insulated injector feed line to the near side clack valve (side feed rather than top feed being considered an important aspect of modern boiler water treatment phenomena), high degree of insulation applied to cylinders and valve chests, air operated sanding gear and illuminated power unit motion (though not directly visible here the cab interior has been fitted with a new lighting system along with injector overflow illumination and headlights). Also visible are the new design of drive cranks, eccentric cranks and eccentric rod big end housed roller bearings. The new fixed tool and battery boxes are just visible on the footplate below the boiler barrel.

The Argentine national flag has been permanently fitted to the front water tank in testimony to Porta and the fact that this locomotive was originally designed and built by Tranex in Argentina during 1994 (Carupa workshops Buenos Aires). Subsequently it was rebuilt and modified during 2001 by the same company (End of the World workshops, FCAF, Ushuaia).

The shape of the Lempor chimney (diffuser) is clearly visible along with the air pump exhaust pipe routed to atmosphere outside the smokebox so as not to affect the carefully calculated drafting arrangements of the Lempor exhaust system.

By no means on a par with what could be produced in a fully developed country given sufficient resources, No.2 represents what can be achieved in the field of steam locomotive modification with a minimal investment by owners and operators alike.

Questions and Answers

The above list of work raised a few of questions in my mind which I addressed to Shaun.  His answers are much more interesting than I had expected, which is why I have included them here.

Q: Why boiler rebuild in 2005 when a new boiler was fitted in 2001? Weren’t there sufficient funds to do the full job first time round, or were there other reasons for doing it in stages?

A: The spare boiler was fitted in 2001 because the original boiler showed signs of a warped crownsheet. This was caused by former crews carrying to low a water level in the original boiler in days pre 1999. The crews here had not been trained properly and were not aware of the risks involved with boilers. It is amazing that no accident occurred during those years. Neither of the boilers were fitted with fusible plugs and only one means of determining the water level in the boiler. The original idea was only to raise the old boiler and modify the spare fully before fitting at a future date. Time and circumstances did not permit such. Therefore I am left with the original boiler at Ushuaia. I had the barrel tested and such is okay, this means that as time and money allows we can modify this boiler (lets call it No.1) to include a high degree of superheating, belpaire firebox, feed water heater (feed pump to be fitted), auxiliary manifold fitted outside of the cab and foam height meter. The smokebox will need extending so as to accommodate the new superheater header and feed water heater (something along the lines of Porta’s 1816 in Cuba) and this will mean an extension of the engine as a whole so some careful redesign work needs to be done here. Boiler pressure to be raised along with a redesign of the boiler stays. Some 75% of the new tubeplate area will be taken up by the superheater flues, the remaining smoke tubes will be fitted with an economizer (superheater booster). As you mention the stage work was a crucial part of the plan to improve the FCAF as a whole hence stage 1 modifications to Camila, Nora/Porta, issuing of train operating regulations, maintenance systems, plant & machinery, track, infrastructure etc. We are now in stage 2 of the development which means completing in a fully professional manner all that was begun during stage 1 (1999 to 2002). A realistic timescale (taking into account where we are and the singularity of Argentine businesses which I am sure you can appreciate from running your own company in China!) for carrying out all stage 2 work at FCAF would be 2003 to 2007.

Q: What modifications did you make to the drive crank and eccentric crank? You draw attention to them in the photo, but they don’t look anything special or unusual to the untrained eye;

A: If you look closely at old photos of No.2 (Hugh Odom has a good one on his website with Porta standing next to it taken December 2001) you will see that the drive cranks are now a slightly different shape. They were redesigned and manufactured new in Argentina during 2002. Due to time and financial restrictions during 2001 (we were trying to get the engine ready for the world conference which was to held at Ushuaia during October 2001 and we had begun the work to No.2 with next to no planning and budgeting due to its mechanical failure on 20/2/01 which meant the whole plan of work being brought forward by 1 year) we did not carry out investigative work with respect to the original design and manufacture of the drive cranks and we re fitted such to the new wheelsets as was. The originals were (as the boilers 1 & 2) not designed or manufactured to any given code of practice and had been sleeved so as to fit on the journal. The sleeving allowed minimum crank web thickness and the result was a very embarrassing failure in traffic on February 4th 2002. I redesigned the cranks to AAR standard practice during March of last year and they were complete for fitting in August. The eccentric cranks were of the same nature so at the same time I redesigned these and had them manufactured along with the new drive cranks and axleboxes so as to reduce production cost (don’t forget that all this was taking place at the height of our economic crisis in Argentina when we did not know what was happening day to day!). Again if you have a close look at the photos you will see a difference in shape and section.

Q: Why is insulation of the exhaust steam pipes necessary? I can guess a vague sort of answer to that, but would like to know the real reason.

A: The energy conserved in the exhaust steam is of the highest importance in order to maximize the draughting capacity of the exhaust ejector. The more energy that the steam has on striking the Kordina wall (which is a first stage ejector in itself) the better it will contract in the converging section of the Lempor nozzle and hence expand in the diverging section of such. The releasing through the diverging (top) section allows a greater velocity to be achieved (in excess of the speed of sound in the case of the Lempor ejector) thus higher draughting capacity (smokebox vacuum in simple terms of testing reference for the engine). In the case of No.2 the problems of energy conservation are made more difficult because we are dealing with a Garratt locomotive that has long exhaust steam pipes with an increased flow section in order to streamline the exhaust circuit, thus reducing back pressure. In simple terms the biggest problem associated with this type of engine (the problem increasing with the size of such) is the total pressure drop between the boiler to the steam chests and from the exhaust chambers to the blast nozzles. Apart from the length of the pipes concerned we are dealing with a saturated boiler as far as No.2 is concerned, NOT YET superheated (see boiler notes above). So, our problem of the exhaust steam having enough energy to perform draughting work at the ejector is compounded. This is also very noticeable at lower pressures (see steam charts). The live and exhaust steam pipes are therefore insulated so as to conserve as much energy as possible. In the Porta modern compounding system, re superheating takes place between HP and LP cylinders and when we get around to designing and building the LVM 803 for FCAF this will be the case.

Q: What’s the steam sampling system for and what does it do?

A: This amounts to nothing much more than a ‘Liebig Condenser’. A sample of the steam can be taken straight from the dome and the condensed steam then analyses for contamination etc. The most interesting part of this testing is that steam samples can be taken at varying outputs of the locomotive (i.e. different steaming rates).

Q: Is the flange lubrication system for going round tight curves? If so, how do you prevent loss of traction from lubricant getting on the rail head? (Or is that what the rail cleaning jets are for?)

A: The subject of rail adhesion is a very large one. Traction is lost due too contamination at the rail head and not rails being necessarily wet. The flange lubricators use condensed steam direct from the auxiliary manifold and when correctly used apply a steady trickle of water to the flange. Yes they help reduce tyre and rail wear on sharp curves without the requirements of grease flange lubricators which cause a great deal of slipping for all types of traction. The steam jets are really rail head decontaminaters (anti slipping device). They also de ice the rail heads in sub zero climatic conditions and can be used in reverse application as de sanders. The ‘water lubricators’ were pioneered in Peru. One of my many tasks st the moment is to write a detailed technical paper on this subject which gives practical applications of such.

Q: What happened to the original driving wheels that caused them to break up, and why do you expect the current wheels to follow suit?

A: Poor castings combined with un tyred wheelsets. The current wheels as fitted were manufactured at the same time (1994) to the same standards so these will follow suit. New wheels are to be designed and manufactured (fully balanced and tyred of course!).