West Riding Automobile
1966
Daimler Roadliner
Plaxton B50F
I always thought the single deck version of the ‘Fleetline’ was called a ‘Freeline’ but it appears I
was wrong, it was called a ‘Roadliner’. It as come to light whilst researching this bus that the
‘Roadliner’ was not the most reliable chassis in fact it was quite the opposite. That I find strange as
the ‘Fleetline’ the double deck chassis was very reliable if you know what the problem was please leave
a comment? Another interesting thing about this bus is that the body was built by Plaxton who were
better known at that time for coach bodies rather than bus bodies although having looked at there
website today they do four very impressive bus bodies at the moment.
The Roadliner was a different beast to the Fleetline, it was a 36 foot long,
and for it’s time, a low floor chassis, incorporating air or metalistic toggle link suspension.
In the days before one man operation of double deckers was permissible, the
high seating capacity Roadliner like it’s contemporaries the AEC Swift, Leyland Panther, and Bristol
RE, was after a piece of the action.
The Bristol RE proved to be the only reliable model of the bunch, enjoying
large orders and long service lives. The Roadliner sadly proved to be just about the worst, due
largely to it’s weird and unreliable Cummins V6-200 engine.
Later models were instead equipped with the Perkins V8 engine, but it seems
the damage had already been done, with braking and suspension problems meantime manifesting
themselves.
West Riding really didn’t need these problems, with their hands already full
of the woes presented by their large fleet of Guy Wulfrunians.
PMT Ltd (Potteries Motor Traction Ltd) however got their hands burnt the worst
as the biggest operator of Roadliners, with 62 buses and 6 coaches (?). Despite strenuous efforts to
keep their Roadliners on the road, by 1970 PMT’s problems were such that they finally threw in the
towel, and withdrawals started soon after. Their last left the fleet in 1976.
Keith Jackson
You’re right about PMT’s 6 Roadliner coaches. They were fleet nos. C1097-C1099
(KVT 197-199E) and C1100-C1102 (PVT 100-102F). The first three had Plaxton bodies and the last three
Duple.
All the early PMT Roadliners had Cummins engines. The Perkins alternative was
trialled in the rebuilt PMT prototype S1000 (6000 EH) and then the last 10 examples (built in 1968;
130-139 (WEH 130-139G)) also had the Perkins unit.
I remember going round the PMT depots on my bike in about 1975 and seeing huge
quantities of Roadliners dumped around the back of Cheadle depot prior to disposal. There weren’t
any Roadliners at any other depot so I suppose this was either the last depot to operate them or it
was a convenient place to collect them.
As you say, long before then the writing had been on the wall for the
Roadliner and PMT tried several different alternatives; a batch of 21 Fleetline single decks in 1970
with unusual Alexander ‘W’ type bodies was followed by several batches of Bristol REs. Even
these didn’t survive long, however, as the Leyland National revolution gathered pace.
Mel Harwood
The plus points with the 9.6 litre Cummins VIM V6 200 engine were its
compactness and potential to deliver a hitherto un-heard of 192 bhp (hence the 200). Tragically, the
engine failed to live up to its promise, maybe because it was fundamentally a marine unit designed
for totally different working cycles. Result? Mechanical mayhem.
By the time the slightly
less-powerful V8 unit from Perkins was offered, the Roadliner’s reputation was irretrievably
damaged. Sad, really, because in other respects, it wasn’t a bad vehicle.
Chris Hebbron
Thank you for your comment on the Roadliner I did not know that the Cummins
engine was based on a marine engine no wonder it was a disaster. When you think about it a marine
engine is set at a steady rev rate and stays there for hours which couldn’t be more opposite to a
bus engine.
Peter
Early diesel locos in the UK were powered by modified versions of marine
engines and seemed to do surprisingly well in general. However, there was a stage well into the
lives of the High Speed Trains, when they suffered overheating problems one hot summer. The engines
in a couple of power cars were strapped up with sensors and the results were a revelation to the
engineers. One was that that these engines never spent much more that 10 seconds on one power
setting! Your point precisely! They had to redesign the cylinder heads and radiators which cured the
problem and made them more reliable and efficient. Some might argue that this survey was
well-overdue! Most have been re-engined with ML (German) engines which are probably far superior to
the old Ruston ones.
We know that Cummins nowadays produces some superb diesel engines, renowned
for their high-revving abilities. However, I do recall that about 10 years ago, a class of diesel
train here in the UK was fitted with one type of their engines and was a disaster after about three
years! After mutterings about legal action, they changed all of the offending engines at great cost
them themselves, better than at a cost to their reputation, I suppose!
Chris Hebbron
Let’s not be too unkind about marine engines: after all, the Gardner 5LW & 6LW
were essentially marine engines, and they had a strong claim to be the most economical, reliable and
altogether unbreakable engines ever installed in a bus.
Ironic really that as the Bristol Ks
and Lodekkas went to the scrapyards in the 60s & 70s, a huge proportion of their engines were
shipped to the Far East to be fitted in junks, where they are probably still puttering about at that
legendary 1700 rpm governed speed!
David Jones
Just to correct the details of the PMT Roadliners: There were 64 in total, 58
buses and 6 coaches. The prototype SN1000 never had a Perkins V8 engine fitted. The first Perkins V8
was trialled in fleet number S1078 in 1968 - just before I joined the Company as Technical
Assistant. Later (about 1970) Fleet number S1065 was also fitted with a Perkins V8 but that was a
far as the conversions went. We had horrendous problems with the Marshall bodied buses (S1069-S1091)
with the bodies literally breaking their backs requiring major rebuilds as early as 1970. Some were
exported to Australia in 1972 by a Cranes and Commercials (Dealer), Southampton.
Ian Wild
Interesting to hear the problem with the Roadliner breaking it’s back because
the 36′ Fleetline with the panoramic windowed Alexander W body did the same, no doubt the
effect of sticking a ton and a half of engine and gearbox across the end of a long rear overhang.
One of the Scottish operators of the type (Dundee?) rebuilt some of theirs with a traditional
Fleetline bustle and rear bulkhead - not sure whether it was a success in engineering terms - it was
certainly an oddball in looks!. The 33′ version of the Fleetline single decker escaped these
problems.
The Freeline was a mid underfloor engine.
While we are on the subject of
Marine diesels - what about the Deltic, that engine came from a marine ancestry.
Andrew
I am out of my depth here, but was always told that the Deltic appeared so
that English Electric could find a use for its Napier marine diesels which were intended to run more
consistently. Some say it was prone to the same problems, but I think it was diesel electric and so
was driving electric motors, possibly a more consistent task.
Joe
I once heard that there was another issue with marine diesel engines in
railway locos (I believe that all the relevant ones, by the way, were diesel-electrics). In addition
to the constant engine speed issue, there was a big difference between the natural "secondary
resilient mounting" provided by the sea water under the hull of a ship, and the fairly rigid
track bed on which a loco rode. The relevant engines preferred the former, and tended to protest at
the latter.
Stephen Ford
As Stephen says, the locos were diesel-electrics and their "marine"
engines were supplying a constant output rather than a variable. My family event last weekend
including a trip on the canal from Sheffield Victoria Quays towards Rotherham. I was surprised to
learn of the existence of the Gardner 2LW - very popular on narrow boats. Once the beast was
underway, no need for anything bigger, no need for acceleration! John Deere, of tractor fame, are
also involved in marine engine supply these days - using another "trade" name (Lugger I
believe). Diesels have many applications but there are definitely horses for courses. Dare I suggest
that, in their day, Gardners were so good that the design could cope with marine, road and
generation applications whereas others didn’t quite get their act together!
David Oldfield
According to Alan Townsin, one of the problems with the Cummins V6 was that,
for production reasons, Cummins used the same "V" angle as on their V8s. As a result the
engine was inherently unbalanced and prone to vibration problems. This may have contributed to its
well-known tendency to run hot, tighten-up so that it wouldn’t re-start, and smoke badly as well.
Shame about the Roadliner, as the overall design concept was brilliant and well ahead of its time.
The body problems were not unique to the Roadliner: many rear-engined buses tended to have
problems with chassis flexing, and many coachbuilders struggled to cope with it. Even AN68s can
exhibit symptoms: just look for all the popping rivets above the rear axle on a well-worn Roe
example!
David Jones
27/01/15 - 13:52
I’ve just seen David Oldfields comment about Gardner LW-series engines in
narrow boats (two comments above). As he says, acceleration is not important in that context;
however, deceleration most certainly is. The propeller is shaped specifically to push the boat
forwards. It is much less efficient when running in reverse, and that’s where Gardner torque comes
into its own. Stopping power is everything on canals and rivers, and Gardner engines are even more
revered there than they are on the road.
Peter Williamson
28/01/15 - 06:33
You have reminded me of a vehicle much closer to home with Cummins problems in
miniature. The Hillman Imp was an excellent car, the first hatch- well, notch- back with luggage
space at each end and a wonderfully smoothly revving aluminium engine and precise steering and gear
change. Does distance lend enchantment to the view? I did have three, not all at once. The engine,
it is said, all 875cc of it, came from a Coventry Climax fire pump (is this true?) and, yes was not
used to revving, especially like that. So, apart from the water pump, you could go through cylinder
head gaskets, especially with the twin choke Sunbeam version which had an oil cooler. The benefits
of this became apparent when the "boiling" light came on: go faster, force more air
through and the light would gently fade. Are we a bit off-thread? Memories…
Joe
02/02/15 - 07:01
Part of the legacy of Gardner’s early Diesel engines, designed originally for
marine and stationary use, was the continued use of its own design of all-speed governor on the fuel
injection pump. Many other Diesel engines have utilised injection pumps fitted with 2-speed
governors (eg: CAV N and NN types, Simms BPE type, and the Friedmann & Maier pumps fitted to Leyland
National 2s and Tiger TRs). Such governors regulated only idling speed and maximum rpm as determined
by the engine manufacturer. Without any load on the engine (for example when running the engine with
the gearbox in neutral), if the accelerator was set to any given position, the engine would either
steadily climb to maximum rpm, or rise slightly and then steadily fall back to idling speed. On the
road, variables such as vehicle load, gradient, gear selected etc all influenced engine speed
between idling and maximum rpm, keeping things much more predictable for the driver.
With
Gardner engines having an all-speed governor, this meant that when the engine was running without
load, the accelerator could be set to any given position, and the rpm would stay at a constant speed
for that position (hope this is all making sense!). All-speed governors were particularly popular in
marine and generator set applications, as when loads on the engine could vary, the engine speed
would remain fairly constant. This could be heard on fairground generator sets (many of which tended
to be Gardner-powered), when the load on the generator reduced, yet the engine speed remained more
or less the same, albeit quietening as the load decreased. Conversely as generator demand increased,
the engine could be heard to work harder, but the rpm would hardly change.
In road vehicles,
as with the two-speed governor, vehicle load, gradient, gear selected etc still came into play, and
drivers would probably be unaware of such differences in governor types, as the accelerator position
would be constantly changing when driving. However, I have heard drivers say that with
Gardner-engined vehicles the further the accelerator was pressed the more resistance could be felt,
as more tension was placed on the governor spring via the various mechanical linkages. This
‘heavy throttle’ feel, as far as I’m aware, was peculiar to Gardner-powered vehicles due to
the design of governor. Gardner’s injection pumps were very large, heavy affairs with a large strong
governor spring, and the cambox, camshaft, governor assembly and casings were all of Gardner design
and manufacture. The fuel injection equipment mounted on top of the cambox was manufactured by CAV
(Charles A Vandervell), and the original design was by Bosch, with CAV having an agreement to build
the equipment under licence at their works in Acton, London.
Brendan Smith
02/02/15 - 11:41
I agree entirely with your comprehensive comments about the Gardner all speed
governor, Brendan, and I have remarked on this feature myself elsewhere on this site. When pressing
the accelerator pedal, one felt a very strong initial resistance against the spring that then
softened until the engine speeded up to the new governor setting. As the rpm built up, so one felt
the resistance building up again under the pedal. When changing gear with a conventional gearbox,
the best technique, having selected the required gear, was to blip the engine slightly before
re-engaging the clutch, which reduced the resistance on the throttle pedal. This obviated the snatch
in the transmission that resulted if the accelerator had to be pushed down against the governor
resistance, which would give way suddenly. Gardner abandoned the all speed governor in favour of
max/min CAV fuel pumps in late 6LX and all 6/8LXB production. I suspect the LW20 range also had CAV
pumps. The Gardner/CAV pump could not provide the higher injection pressures required for the
increased output of the later engines.
Roger Cox
03/02/15 - 09:17
I often wonder what contribution Edward Turner might have made to the
Roadliner. Edward’s main strength was in engine design, most famously for taking his Ariel Square
Four motor bike engine and splitting it down the middle to give us the Triumph 500 cc parallel twin
- hence the Tiger 100, Bonnie etc.
When Jack Sangster brought Edward into the BSA owned
Daimler fold in the mid fifties, Edward went on to design various ‘V’ formed petrol engines
for Daimler cars. I am sure that, if anyone could, he would have designed the ‘V’ diesel to
power their Roadliner. We would then have had ‘proper’ low floor buses decades before we
actually got round to them.
One can only speculate why this was not done. Was it Daimler’s
reluctance to invest in a new Daimler engine? Or did politics dictate that the US owned Cummins
factory should be given work in the deprived north east of England? Or did Edward Turner simply
retire?
Alan Johnson
06/02/15 - 06:39
The late 1960s can’t have been an easy time for WRAC’s engineers: on top of
the Wulfrunians the Roadliners can’t have been exactly good news . . . and then there were some
Panthers on top. Following on from Alan’s comment, it was my understanding that the Cummins V6 was
imported from America, so Cummins’s Darlington factory didn’t benefit in any event. A quick Google
has confirmed the latter, but suggests part of "the grand plan" was for the Cummins engine
to be built in a joint-venture in the old Henry Meadows factory (which was adjacent to JDGs Guy
factory). The same article also suggests that a batch of 12-metre Roadliners was ordered but later
cancelled (by whom?), that the Panther Cub was produced for Manchester after it threatened to order
10-metre Roadliners, and that a Rolls-Royce-engined option was considered. Looking at the original
picture, I’m surprised to see a Cyclops fog-light fitted as late as 1966: Cyclops fog-lights were
surely a fad of the 1950s . . . perhaps it was felt a more conventional near-side fitting might have
added to the "inherent imbalance" of the Cummins engine.
Philip Rushworth
07/02/15 - 06:09
Thank you for that fascinating information regarding smooth gearchanges Roger.
The first Gardner Diesel engine to have a non-Gardner injection pump was the 6LXDT introduced in
1984, which as you mention had the CAV ‘Majormec’ pump, rather than the usual CAV ‘tops’
on a Gardner cambox and governor assembly. The fitting of CAV injectors, rather than Gardner’s own
(Gardner referred to theirs as ‘sprayers’) was another change on the 6LXDT. Gardner was trying
to keep up with operator demand for more powerful engines (especially in the heavy goods vehicle
sector), and it was said that the CAV pump and injectors could operate at higher injection pressures
and at a faster injection rate than Gardner’s system could manage at higher bhp ratings. The
‘LW20’ (20bhp per cylinder) range was discontinued in 1974 Roger, and all LWs had the usual
‘Gardner bottoms with CAV tops’ injection pumps mated to Gardner ‘sprayers’.
Referring to Alan’s speculation about a Daimler V8 Diesel engine in the ‘Roadliner’,
what a wonderful sound that might have made, if the 2.5 litre Daimler V8 petrol engines were
anything to go by. Such ‘lazy-sounding’ low-revving V8s sounded wonderful as they burbled
past, but whether the Daimler V8 Diesel was an opportunity missed or a lucky escape, we’ll never
know. However, one opportunity elsewhere fortunately WAS missed, as in 1967 Bristol was looking at
the feasibility of fitting a Cummins V6 engine into the RE (whaaaat!). Duncan Roberts’ excellent
book ‘Bristol RE - 40 years of service’ even has two photographs of the attempt. The chassis
was a standard Series 2 RESL6G due for delivery to Crosville (ERG3: OFM 3E), and the photos show the
V6 supported on wooden blocks at the height and position envisaged for fitting. A Gardner oil bath
air filter housing can clearly be seen, as can the ‘JAGUAR - CUMMINS’ lettering on one of the
engine rocker covers, which is intriguing. The unit was very compact, but also quite tall and would
have protruded well above the chassis toprail. The RE chassis was already quite high at this point,
and fitting the V6 would have required the floorline to be even higher and the project was dropped
(sigh of relief all round). The RESL went on to enter Crosville service as nature intended fitted
with a Gardner 6HLW engine. (There wouldn’t have been a welcome in the hillside with that V6 fitted
that’s for sure). In the book, Duncan Roberts states "The time and money spent on this exercise
suggests that there was an influential customer in the wings, but no clue has been found to his
identity. The RE was therefore spared the odium that would have flowed from the unreliability for
which this engine (the V6) became known".
Brendan Smith
09/02/15 - 07:10
The Cummins plant at Darlington certainly carried out warranty work on the V6
whether or not they were actually built there. Because of the V6 problems, PMT were issued with
three float V6 engines to enable units (usually by that time failed ones) to be returned to
Darlington for rebuilding/upgrading. I drove the PMT Thames box van up there on one occasion to
exchange three defective engines for three rebuilt ones. It would have been impractical to have
returned them to the States for attention.
Ian Wild
03/12/15 - 10:56
As the author of the Wikipedia article on the Roadliner I can tell the poster
who asked that it was a South African customer who ordered and later cancelled the 12m Roadliners.
It may have been Pretoria, who also ended up with the last ones bodied (AEC AV810 powered) but I’ll
have to dig out my copy of Buses Extra 39 first.
Stephen Allcroft
30/12/15 - 06:24
It was Johannesburg who ordered the 12m versions, before cancellation the
designation was altered from SRC6-40 to SRA8-40. Chassis numbers are given in Tony’s article.
Sephen Allcroft
20/01/16 - 05:46
I think Ian’s recollections about returning the V6 Vim engines to the
Darlington Plant are now a little hazy with time. Cummins Darlington plant built the smaller V6/V8
Val/Vale engine families, for Ford and Dodge. We did have a local Distributor, C D S & S, who would
have rebuilt the engines on an exchange basis, on our behalf. Both Cummins plants in Darlington were
for new manufacture only. All the engines supplied to Guy and Daimler were manufactured in Germany
by Krupp. As an aside someone earlier suggested that the V6’s, as supplied to Guy/Daimler, were
originally designed for Marine use, not so, the automotive sector was always the driving force
behind new engine designs (volume), other applications came later.
Peter Hobson
21/01/16 - 06:34
Peter - PMT categorically did return V6 VIM engines to the Cummins plant at
Darlington - I drove the PMT Ford lorry up there one Friday with three defective engines, returning
with three rebuilt ones. This was a regular job for the lorry driver at that time. This was a
campaign change instigated by either Daimler or Cummins, our contact at Cummins was Doug Strachan.
Unfortunately the campaign changed engines were little better than the originals. What a surprise to
see your name on the site - hope you are keeping well.
Ian Wild
21/01/16 - 15:28
Whatever the truth about the original purpose - marine or automotive - of the
Cummins V6/V8 ranges, I consider the Cummins PT injection system to have been totally unsuitable for
automotive applications. The response to accelerator movement was exceedingly coarse, giving the
effect of the engine being either "on" or "off". I mercifully never drove a
Roadliner, but I had plenty of experience with the L10 in Olympians, and it was a horrible engine
for smooth progress in a bus. Some manufacturers, notably Dennis, tried out the bigger M11 for bus
work, and abandoned the idea. The Dennis R series coach didn’t do very well either.
Roger Cox
21/01/16 - 17:12
Ian- I have a look on this site ever now and again just to see who’s posting.
The odd name from the past that comes up rattles my box, like Peter Wyke-Smith, which reminds me of
the time we jointly got Leyland over a barrel to fit the HLXB/HLXCY into the National.
On the
subject of the Cummins V6 Vim engines, I have to defer to your laser like recollection (Note the
tone of the grovelling!) Doug Strachan ran the Pilot Centre at Darlington, fitting various Cummins
engines into new applications. George Ochs who was responsible for all Customer Service throughout
the UK was also responsible for orchestrating any company campaigns, usually through the distributor
network, ( via Cummins Diesel Sales and Service a subsidiary of Blackwood Hodge in Northampton). I
assume that George took a cheaper/faster option, to keep costs down, by having Doug’s people cover
the refurbishment ‘in house’. At the time we were in the middle of the V6/V8 Val/Vale problems
with Dodge and Ford which kept everyone in our department out of mischief I can tell you. Talking of
Doug Srachan, I went for an interview with him for the job of Pilot Centre Technician, at the back
end of 1966. Halfway through our conversation, mainly relating to my time with Gardner, he said I
might be interested in a different job. I then jumped ship and joined service department with a
higher salary, company car and exes, working under George Ochs. I never did buy Doug that pint I
owed him for his selfless attitude!
Peter Hobson
22/01/16 - 06:09
Peter - that’s very interesting. I’m glad my memory hadn’t failed me over the
reworks at Darlington - I didn’t know the reason why until you filled in the background to Doug
Strachan. Also interesting to note that Dodge and Ford had problems with the VAL/VALE engines. Were
the problems similar to the VIM/VIME in bus application? What was the difference between the two
groups of engines? You couldn’t forget PH Wyke-Smith!!! I can imagine he told Leyland EXACTLY what
he thought about Leyland Nationals, 680/L11 engines and Leyland themselves!!
Ian Wild
24/01/16 - 07:09
The VAL/VALE were a similar design with a lower displacement, ISTR the VALE at
about 7.6 litres. RPM was even higher and only one was fitted to a PSV: https://www.flickr.com/photos/1 — https://www.flickr.com/photos/2
Stephen Allcroft
Monday 25th
Ian - The problems with the early Val/Vales in the Dodges were mainly down to
excessive black smoke. We had an ‘injector train’ campaign due to excessive wear on the mating
surfaces of the tappet, push rods and rocker levers. The ensuing wear severely reduced the pre load
torque applied to the injector, allowing excess fuel to be injected. If I remember correctly the
ball end surface finishes had to be improved on all the mating items, from the camshaft to the
injector. The Ford engines were a later spec and I think they all had the later mods included from
day one. The V6’s ran at 3300rpm the V8’s at 3000rpm. Getting drivers to use the full engine rev
range was quite a problem and I think both OEM’s fitted rev counters marked with a green band to
encourage them to make full use of the available power. Drivers using the " give it 3000 revs
and drop the clutch" style of driving tended to generate less engine problems than those with a
lighter touch. The V6 Vim engines in the Guy’s were a lot less hassle than the Daimlers.
My
personal opinion being that the engine cycling requirement for the PSV spec, i.e. lots of idling,
were not helpful given the type of fuel system employed at the time. (Keeping on top of the injector
preload setting, on a regular basis, was required too frequently for most customers, to keep a clean
exhaust.)
As John Ashmore mentioned in a prior forum, some of the engines suffered from
dropped valves, due to crossheads ‘floating’ and pushing valve spring collars down thus
releasing the valve collets. These failures indicated an overspeed condition and/or excessive valve
clearances.
Peter Hobson
26/01/16 - 06:44
I am not an engineer, but a working life of 43 years in many roles in the bus
industry brought me into close contact with most facets of its operation. The engineers on the OBP
forum are welcome to shoot at my following opinions on Cummins engines.
Legend has it that the
PT (Pressure Time) fuel injection system was created because Cummins would not pay the royalties to
Robert Bosch for the use of the traditional injection fuel pump. Cummins made much of the feature
that ‘eliminated the need for high pressure fuel lines from the pump to each injector’. This
was never a particular problem for other engine makers, and appears particularly eccentric nowadays
in a world of high pressure common rail injection systems. The Cummins fuel system employed another
camshaft at the cylinder head, this camshaft necessarily being much larger than that in the cambox
of a normal fuel pump, to operate the PT injectors, these themselves being complicated units that
did not give the accuracy or service life of ordinary injectors. PT was less fuel efficient than the
Bosch system, required greater maintenance, and yielded very coarse engine speed responses to
movements of the accelerator pedal in automotive applications. Significantly, the later B series
engine (originally a Case Corporation design) which has spawned the present Cummins diesel ranges,
abandoned the PT system. PT fuel injection made the highly stressed VAL/VALE/VIM/VINE V form engines
more complicated than they needed to have been, and this, plus the poor throttle response endemic to
the design, must have contributed to the mediocre reliability standard. Sadly, the promising Tilling
Stevens TS4 diesel development programme was cancelled by Chrysler because of its joint venture with
Cummins in the then new Darlington plant for the supply of V form engines. It is one of the wonders
of the engineering world that the reputation of the Cummins company survived the fiasco of its
dreadful V form engines. By contrast, the present day Cummins engine ranges are widely
respected.
Roger Cox
Vehicle reminder shot for this posting
27/01/16 - 16:08
I can vaguely recall, having no direct contact with Cummins engined
Roadliners, that Black & White of Cheltenham re-engined some of their Roadliners with Perkins V
engines. Did they fare any better?
Geoff Pullin
29/01/16 - 07:06
Geoff - PMT had two Roadliners re-engine with Perkins V8-510 units plus the
final batch of 10 delivered with the Perkins engines. The Perkins unit was a much smoother running
engine probably the eight cylinders helped. Time dulls the memory, I don’t think the Perkins buses
lasted any longer than the Cummins ones. I do recall quite severe cylinder bore wear with the
Perkins engines, maybe as much to do with the air induction system (and maintenance thereof) as
shortcomings with the engine itself. There were other problems with the Roadliner, not least the
metalastik toggle link suspension although Midland Red seemed to manage with it. Thanks to Peter H
for the detail of VAL/VALE engine problems.
Ian Wild
29/01/16 - 07:06
Although slightly off-piste, I recall some years ago that British Rail had
problems in some their Cummins- engined diesel trains and Cummins had to replace all of them at
considerable cost.
Chris Hebbron
29/01/16 - 12:56
I think you are thinking of the Class 142,143 and 144 pacers that had their
TL11/Hydracyclic drivelines swapped for Cummins LTA10H /Voith after severe early unreliability.
Volvo as successor to Leyland Bus took the hit for the Cummins Engines and Cummins as successor to
Self-Changing Gears paid for the Voith transmissions and Gemidner(sp?) final drives.
https://en.wikipedia.org/wiki/British_Rail_Class_142
https://en.wikipedia.org/wiki/British_Rail_Class_143
https://en.wikipedia.org/wiki/British_Rail_Class_144
the
141s retained their TL11H and Hydracyclic driveline but only ran for 14 years in the UK although
eight were exported to Iran which could be seen as a hostile act…
Stephen Allcroft
29/01/16 - 17:29
Thx, Stephen A, for filling in the detail. I wouldn’t think any of them are
still running. I also recall Rootes Group selling thousands of Hillman Minxes CKD to Iran years ago
- another hostile act!
Chris Hebbron
29/01/16 - 17:30
Does anyone know what the problems were with the rubber suspension on the
Roadliner, and was it one or both axles? With one exception, the toggle link suspension was only
used on the rear of BMMOs. It was highly successful and on single deckers extremely simple. The
exception (the S19) was in principle if not in detail, more like the Roadliner. However, the S19 is
thought to have retained this arrangement for its whole working life.
Any details would be
much appreciated.
Allan White
30/01/16 - 06:07
Allan - the PMT Roadliners had metalastik suspension on both axles. Problems
as I remember were panhard rod bush/bracket wear/failure and failure of the metalastik bonding in
the suspension units themselves. also, I’d forgotten that the 24 Marshall bodied vehicles broke
their backs after about three years service. I remember one was rebuilt but at massive cost
particularly labour. The Plaxton bodies being timber framed were rather more forgiving.
Incidentally, Plaxton was not a mainstream bus body supplier to the BET group at that time, wonder
why they got the initial Roadliner body contract?
Ian Wild
30/01/16 - 06:08
Roger - I may be able to enlighten you on some salient Cunmmins details.
Clessie Cummins introduced the PT system in 1924, a major update took place in 1954 to improve fuel
efficiency, due to increasing competition in the US. None of the Cummins historical info makes
mention of any contact with Bosch.
The mechanical injector is actuated, by a third rocker
lever, from a standard engine camshaft comprising an additional cam located between the inlet and
exhaust cam lobes.
The fuel pump is a very compact unit, you can hold it in one hand. It
supplies a fuel pressure up to approx. 250psi max to the injectors. Injection pressures up to
18000psi can be achieved within the nozzle part of the injector. In the 1960’s the same size pump,
with different internal settings, could be use on a small Val V6 up to a 28 litre V12 - 700 HP
engine. The fuel pump for Automotive use was a Max/Min governor type, an ‘all road speed’
governor, used mainly for use on Gen Sets or Loco’s was available at extra cost.
In retrospect
the Val/Vale, Vim/Vine engines were of very ‘Oversquare’ design. Subsequent designs increased
the stroke of the engines and were more acceptable. I hope the foregoing helps.
Peter Hobson
30/01/16 - 18:37
Thanks for that clarification, Peter. I saw a number of L10 engines being
worked on, and, had I looked at them properly, I should have seen that the injector of each cylinder
was operated by an extra cam lobe rather than a separate shaft. (To quote Sherlock Holmes, "You
see, Watson, but you do not observe".) The trouble with the PT system was its coarse response
to accelerator pressure, and I am interested to learn that an "all speed" governor was an
option. This, I am sure, would have remedied that problem in automotive applications. The
"on/off" characteristics of the PT system would not have been significant in haulage use -
unlike passengers, sacks of spuds or whatever do not complain about rough rides - but for bus work
it was terrible. The PT system seems to have been best suited to constant load applications such as
rail or marine. It is noteworthy that the 14 litre Cummins engine that still powers many of the
railway DMUs, and was once offered in UK lorries as an alternative to the Gardner range, did
extremely well in a comparative survey of maintenance costs - a reflection of reliability - compiled
by the "Transport Engineer" journal in 1979. Unsurprisingly, Gardner came top, but the
Cummins 250bhp 14 litre came a close second, with the AEC 760 next. The Rolls Royce Eagle was way
down the list at No.11. Coming in second from the bottom at no.15, the Leyland 510 of Leyland
National notoriety cost six times as much to maintain as a 6LXB. Getting back to the V form engines,
I recall that, in 1969, Cummins and General Motors became embroiled in a lawsuit in which Cummins
claimed patent rights on the principle of the "oversquare" stroke to bore ratio. Quite
rightly, the claim was thrown out by the Maryland court. There were many oversquare engines before
Cummins.
Roger Cox
02/02/16 - 06:58
PMT service 19 (I think) ran to Sandbach with some journeys extended to Over.
The destination display showed ‘Over (Square)’ - quite appropriate for the Roadliners used on
this service!
Ian Wild
