Plasser And Theurer KMX95 CM Tamper

From Festipedia, hosted by the FR Heritage Group
KMX at Cwm Bychan


In March 2005 Welsh Highland Railway Construction Ltd announced the purchase of this machine for use in construction of Phase 4 from Rhyd-Ddu to Porthmadog, and the maintenance and upgrading of the existing railway. Built in Austria in 1995, it was metre gauge and had been supplied by Plasser & Theurer's French subsidiary FRAMAFER for use in an underground coal mine in France. Its last such use is believed to have been at the Mines de la Houve at Creutzwald in the Lorraine coalfield; this was France's last deep coal mine, closed in Spring 2004.


It was delivered to Minffordd Yard on the FR on 29 March 2005 and taken to Boston Lodge for regauging and overhaul. In the course of the overhaul the unit was also fitted with roof sections for above ground use. Also, various systems were modified or removed; those dispensed with included facilities for aligning turnouts, and a pantograph which had been used to check that the overhead power supply was energised while the tamper was in operation. Although this seems contrary to safe working, it is how the mine safety systems worked, the 400V overhead system had to be live for the tamper to operate.

KMX at Harbour Station after a day working on the Welsh Highland Railway - 27 March 2023


The machine was trialled on the Cob in early May 2006 and was delivered to Dinas on the WHR on 16 May. Following further commissioning work it was driven up to its initial work base at Rhyd-Ddu on the evening of 29 June. It underwent successful commissioning trials in September 2006, although the computer systems were not yet fully operational.

KMX in action, Cwm Bychan


It is reported that Plasser and Theurer have asked for the tamper not to be known as one of their products, as the gauge conversion and other modifications have been carried out independently of them. It does not now carry any P&T branding, or that of their French sales arm FRAMAFER, with which it arrived.

When in service the machine is very effective, but like all tampers it needs a considerable amount of maintenance. This has been helped by the acquisition of many spare parts from ex BR machines, and Plasser have helped resolve other problems associated with its French heritage.

After many years of hard work, the KMX was returned to Plasser in Autumn 2011 for a thorough overhaul at a cost of over £70,000. When it returned in January 2012, Infrastructure staff commented that it was a much improved machine.

Technical description of regauging the KMX 95 CM tamper from metre to two foot gauge[edit]

The following commentary was written by Chris Hoskin, Design Engineer for the project. He has since been noted to mutter that he must have had a screw loose!


The Festiniog Railway Company wanted a modern tamper for the construction of the new Welsh Highland Railway. The daddy of all narrow gauge tampers is the KMX12 as seen in Australia. However, they cost an absolute fortune, something the Ffestiniog lacks. Instead, they bought a second hand tamper (10 years old) from France.

The basic workings of the tamper[edit]

The KMX 95 CM tamper is a one off unique tamper although with some common features. The tamper was designed and built by the French arm of Plasser and Theurer, known as Framafer. Plasser themselves admit that Framafer keep themselves to themselves and are not really compatible with the rest of the global business.

The KMX 95 CM is based on the standard narrow gauge tamper, the KMX 12. However at this point all basic similarities end.

Framafer used basic Plasser components and then built a custom Tamper around them. The Tamper was built to work down a coalmine and as such has some very interesting features.

The machine was designed to be split into two halves that could then be lowered down the shaft of the coalmine, and then reassembled on the working floor. From this, we know the mine shaft was more than 10m in diameter but less than 20m! The ability to split the tamper can still be seen in the massive 16-bolt fishplated joints on the top main chassis member on each side of the vehicle. However the vehicle can no longer be split as the chassis has been modified lower down.

The tamper was built with an exhaust scrubber to clean the exhaust, not something that is necessary on an over ground machine and so this was removed from behind the No.1 cab. The space acquired was then used for the main batteries, as the original battery box was designed for an individual (presumably French) type of battery that could not be obtained. The exhaust scrubber was made of 1 inch thick plate welded together into a box approximately 1 foot x 2 foot x 1 foot, and so the weight of the machine would have been lessened slightly by this process. The exhaust is now directed through a standard road vehicle silencer before exiting through the roof. As originally designed, the tamper had no roof (except for the driving cabs) as there was no inclement weather to keep off the machinery.

The tamper was fitted with a pantograph, and, as some doubts still exist as to its use, this shall be described. The process of tamping obviously produces some sparks when the tines are driven into the ballast and in some cases may strike the railhead or the sleepers. In a coalmine there is always a danger of built up sulphur gas which can potentially explode. Although the main railway propulsion system in the coalmine was 400V DC overhead contact wire, the tamper itself was (and still is) diesel hydraulic. In the areas where there was a danger of sulphur gas being present, the overhead contact wire would be isolated. To prevent the tamper also from working in those areas, the main electric circuitry for the tamper was powered through the overhead wires through a pantograph on the roof. This meant that the overhead wires had to be live to allow the tamper to run the diesel engine.

The tamper is also unique in all controls being hydraulic. Generally tampers are provided with hydraulic propulsion and tamping controls and then pneumatic systems for the control circuitry and brakes. The KMX 95 CM however has everything hydraulic (including brakes) except for the measurement trolleys and the locks to prevent the tamphead and lift & align gear moving when the tamper is in travel mode.

A summary of the regauging process is included below. When the Ffestiniog Railway took ownership of the tamper, it had obviously not run for sometime. In fact, it became apparent very quickly that it had been split into its two component halves, hoisted out of the mine, joined back together again and placed ready for transport. This meant it had never run since it had been split into the two halves. It had survived outside in France without any vandalism, but had a broken cab window within a week of arriving at Minffordd. This being the case, two volunteers took it upon themselves to sheet it over to prevent further damage.

As an indication of the size of the vehicle, once the pantograph had been removed, it fitted within the loading gauge (lower half of the line only, i.e. not through Garnedd tunnel) while it was still loaded onto the MoD bogie bolster wagons.

All documentation for the tamper was available and although this was of great assistance later on in the process, as it was all in French, this was a problem for quite some time. However, by the time the tamper was complete, all of the people involved on the project were fluent in technical tamper French!

Tamp head[edit]

The tamp head, although very similar to those on “normal” Plasser tampers, was not quite the same. It was of the same design but had been specifically built for metre gauge. As originally built, it included the ability to swing the tamper tines into the horizontal position to allow it to complete the delicate work of tamping switches and crossings. Included in this extra feature was a pair of extendable hooks that were attached to the Lift & Align gear that allowed the tamper to pick up an entire switch assembly in one piece. It was decided at an early stage that this would be difficult to regauge and so all the mechanism associated with this feature was removed.

Early thoughts for regauging the tamp head (potentially the most difficult part) included changing it for a standard gauge head. This may sound odd but a standard gauge tamper actually has two heads, one for each rail, and a standard head, by chance, is almost the correct size to be a two foot head. By borrowing a tamp head arm from Balfour Beatty’s in Derby, a design was developed to use these arms on the existing head and then manufacture an adaptor head to position the tines in the correct place. It was brought to our attention that many “07” tampers on the main line were being scrapped and replaced with “08” or “09” tampers, and there maybe the opportunity to purchase a scrap tamp head. The team were eternally grateful when Jarvis in Crewe donated a complete tamp head to the project on the condition that we collected it from the yard where it had been dumped. The metre gauge tamp head and the arms from the standard tamp head were sent away to a specialist firm in Barnsley for a complete overhaul.

On return, the tamp head was eased back into position and the new adaptor blocks made to fit. The adaptor blocks themselves work in two planes, moving the tines inboard of the tamper, and closer to the centreline of the tamphead.

Lift and Align gear[edit]

The Lift & Align gear was modelled on CAD to be able to understand how it had worked. This was then transposed into a two foot version until a design was developed. As mentioned previously the hooks for the S&C tamping had been removed, which made the process simpler. The Lift and Align gear consists of a set of flanged wheels that run on the track, and a second set (located in the horizontal plane when in working position) that swing in and clamp the rail between the two sets of wheels. When working correctly therefore, the tamper can keep grip of the rail while moving itself along. It is critical to set the flanged wheels at the correct distance apart to grip the track correctly, so the gear had to be redesigned to allow it to grip the correct profile track

The Lift and Align gear has the ability to move:

a) longitudinally to the tamper, so as to avoid having to clamp onto fishplates,; and b) vertically to set the track at the correct height and cant, and laterally to set the alignment of the track.

The new fabrication was built to keep all these controls in the same place as they had been on the metre gauge version so that the cab controls and measurement gear could be recalibrated more simply (more of that later).


The chassis, as mentioned previously was designed and built by Framafer and was not structurally sound. In fact, the original design allowed the tamper to flex considerably about the tamp head region, which would destroy any accurate measurements. The chassis had in fact been allowed to flex so much that the vertical chassis members holding one of the tamp head guide poles had cracked at the welds. Also the lower main chassis member (which included the third chassis fishplate joint) was foul of the new two foot Lift & Align gear. The chassis was therefore welded back where the welds had failed, and new lower chassis members were fabricated and welded in the Lift & Align gear region. Once this was completed, the original lower chassis member was cut out. To prevent the flexing problem reoccurring, support bars were fabricated, to stretch between the lower chassis members each side of the tamp head, to stiffen the structure.


The bogies on the machine are a very simple single piece construction, with no suspension, a simple ball joint on the bolster. All wheelsets are braked using hydraulic actuators working on discs on the ends of the axles on one. The bogie under the No 1 cab is powered by hydraulic motors, 1 motor per axle by way of sprocket and chain on the axle ends on the other side from the brakes. The tamper is therefore effectively of AA-2 classification. It was fortunate that the bogies were originally of inside frame construction, and were so basic that they consisted of plumber block style bearings bolted to the frame. The original wheelsets were splined onto the axles. It became apparent, that if the wheels could be moved inside the bogie frames, the tamper would be regauged quite simply. However, as is always the case, there were problems. The wheels, in the regauged position would foul the chassis members under the cab when negotiating curves. A solution was found where the wheels were changed from 18” diameter wheels to 15” diameter. The new wheels were pressed onto the original axles (to preserve the current drive and brake mechanism) by Alan Keef Ltd. The wheelsets came from Keef’s and are the same wheelsets as under WW1 Simplex “turtles” such as Mary Ann. To maintain the height of the tamper (and therefore removing the need to recalibrate the measurements) the bearings were lowered on the bogie frame by 1.5 inches. Obviously this has reduced the overall speed of the machine, but in travel mode it is still capable of approximately 18mph.

400V System[edit]

The 400V overhead system as described above was removed completely. The volunteer electrics team that usually rewire carriages for the railway were persuaded to volunteer for the job and stripped back the system to remove the 400V interlock system. 24V batteries were installed (using the space vacated by the exhaust scrubber) and an alternator fitted to the diesel engine. Previously the alternator was driven from a motor powered from the 400V overhead system.

The pantograph, having been already removed from the tamper had taken up residence on the roof of Harold. I can’t remember where the idea came from, but it seemed a great idea at the time. It was worth it just to see the faces of the boys from the Fairbourne Railway as they tried to work out whether it was an original feature or not! If I hadn't been so busy, I might have found time to sign write “PB&SSR” on it, but at least it got warning flashes.


Originally the tamper had no roof as there isn’t much rain and snow down a mine in France. The roof was designed to be easily removed in segments and used the mountings for the mesh that had originally been fitted. It is designed to be functional rather than stylish, although it is based on a simplified Class 66 roof. Other fittings added included windscreen wipers. Inside the roof space at each end are the new headlights and horns. The new horns are the low tone horns from a Class 86 that was going for scrap and were requisitioned by a volunteer in the railway industry. This may explain why an over zealous horn button pushing CME received complaints from the local residents when the tamper took its first trip up the line. The horns were designed to give people sufficient time to get out of the way of a train approaching them at 110mph, not 18mph, so they are quite loud!


The hydraulics had a complete overhaul in the process of rebuilding the tamper, and included the use of biodegradable oil since the tamper will spend most of its time working in the National Park. Much of the pipework was moved to safer runs over the top of the tamp head rather than under it, to prevent damage, so although the tamper may not look so pretty anymore, it is less likely to spray oil everywhere.

The tamper is also fitted with an automatic fire extinguishing system with heat sensors over the engine and hydraulic pumps (of which there are three). This had to be completely rebuilt as it was fitted with unique French fire extinguishers which were not of any known international standard.


The tamper is worked by two people. The supervisor sits in the No 1 cab and feeds track measurements into the tamper using the controls in the cab. The second man sits in the tamp cab, cab No 2 (where the tamp head is) and he actually drives the tamper, as he can see the track so can line the tamper up with each sleeper in turn. He merely tamps the track as the tamper itself is driving the Lift & Align gear to set the track at the correct level, cant, and alignment. The controls required recalibration to set the correct cant and level as the measurement trolleys are all still measuring as if on metre gauge track. This was simpler than trying to regauge the measurement controls.

When first working on the WHR, the tamper was coupled to a runner wagon carrying tools. This wagon was attached to the No. 1 end. Usually, the measurements to be fed into a tamper, if not being fed from a computer(all operators know that the machine feeds the incorrect information through the computer unless the track is already spot on),its why that by law on the initial pass the measurements are dialed in by the Supervisor(who calculates precisely what the track requires) reading the measurements that are chalked on the sleepers by the operator. By attaching the runner wagon in front of the No. 1 cab this is not impossible as an experienced operator/supervisor simply writes down the required equation on the side of the sleeper (where the coupling does not obscure. Recent pictures of the tamper now show it running by itself.

It seems the tamper is now running on maintenance tamp because the track was put in the correct position by the supervisor/operator(Phillip Carl Roberts) on the first pass. Maintenance tamp should only be used on a track that has no dips in it. The thing is with maintenance tamp is that the tamper starts lifting as soon as the front end goes into a dip and because the lifting clamps are not right at the front, the machine lifts the initial high spot of the dip. Also, as the machine exits the dip it will lift less and leave a small dangerous dip.(it transfers 1/3 of the dip) where as a supervisor/operator can dial in the correct required measurements. The problem with maintenance tamp is that if there is an imperfection in the track it will be made worse although it will level the rails relative to each other. In short, maintenance tamp levels the track but can make non dangerous dips dangerous.


As mentioned, all the manuals and drawings were written in French. This posed a challenge as the people working on the tamper dug back to their O level (or GCSE) French to try and decipher the information required. Help came in the form of Dr Barbara Saunderson, a retired French lecturer at Bangor University, who is an FRS life member and also a fan of the WHR. At one point this great lady asked to come and see the tamper to understand it better so she could translate better. Having wandered round and showed her everything she wanted I asked how it was that she knew so much railway specific technical French, at which point she admitted she read French Railway magazines! She was invaluable at translating the information required and pointed out that it was harder than usual as the manuals had obviously been written by a German translating into French. As such, when he had found a German word that he couldn’t translate into French, he used the next nearest equivalent. The most common that was found (and this helped with deciphering the drawings too) was the word “gavage”. This literally translates as force feeding of geese for Foie gras but was being used by the German in this case to mean “hydraulic pressure”!


Tamper trials were carried out first in the yard and then on the cob, but only when it was raining, it appeared (!) and once the functionality had been checked the machine was sent to the WHR. The machine showed its ability and proved that it has sufficient speed to run in timetable slots, as envisaged. As the tamper has no space for tools, a match wagon was built for it and as such is the only unfitted vehicle allowed to run on the WHR (the chopper couplings fitted to the tamper are to allow it to be towed when failed, not so it can become the next standby locomotive!). The effectiveness of the tamper was ably demonstrated in that it tamped at such a speed that it was able, in its more idle moments, to retamp the parts of the WHR that had been opened to traffic already.

It is hoped in the future to modify the controls to turn the tamper into a fully computerised machine. This would enable the tamper to measure the track on one sweep (as it does at present), but then the desired track could be entered into a laptop computer, which would then upload the information to the tamper, which would then tamp the track to suit. With the added help of GPS systems, in the future the track database could keep a record of how the track should look and then the tamper could tap into that to retamp the track to suit.


I had gained permission to name the tamper “Osprey” since the birds in question have been nesting at Pont Croesor near Porthmadog for the last few years and the new WHR will run past the nest site. However, as I left the project before the naming, this was never carried out, but I’d still like to see it done at some point.


It is only right to highlight the work carried out by Phil Tucker as he basically single handedly rebuilt the tamper, with the assistance of others when available. He ably led the project on the shop floor while I drank coffee in the warmth of the office and occasionally ventured out when it was warm enough to put overalls on.

EAG5 WHR 5001 Tender to KMX[edit]

5001 at Dinas

An ex-RNAD wagon has been converted, by members of the East Anglian Group of the WHRS, to act as a tender wagon to the the KMX. It will be used to carry tools and whatever other items may be required, as the tamper itself has no significant stowage, and it is important to keep the operating cabs free of clutter. The wagon will be semi-permanently coupled to the tamper by side chains, in addition to the conventional chopper coupling, and will then be the only unfitted vehicle allowed to run on the operational WHR(C). The wagon was delivered from Cambridgeshire to Dinas on October 14th 2006.

See also[edit]