Hello all I am hopig someone can direct me to a good supplier for
piston rings . When I stripped the engine I broke a few (350 flat
I have tried Thorntons of shrewsbury and fps, but alas they seem
unable to supply.
This is all I need to reassemble the engine (I had new gaskets made in
And one other question- any one have any spares for one?
julian (from Hull)
Ferraris Piston Service seem to be trade only these days, we used to frequent
their main depot in Cricklewood.
Douglas 350cc are listed as motorcycles with 2.3937" bore or 60.80mm. 2
compression rings 1/16" thick and one oil scraper 3/32" thick, 1/8" on the later
Hepolite MP.7755 are the compression rings
Hepolite MSS.7756 are the early scraper rings
Hepolite MDO.8314 are the later 1/8" rings.
There is no 350cc Industrial Engine listed in any of the three catalogues that I
Peter & Rita Forbes
Interesting. I wonder if the FT35 never made it into the after market
catalogues as it wasn't a commercial, ie civilian, product? I know we
have speculated before as to whether Douglas already had their next
generation motorcycle engine on the drawing board and pressed it into
service for the war effort, or if it was initially designed as a
stationary unit and then adapted for the post-war motorcycle range.
Hepolite list all types of engines, commercial/civilian and military (which were
commercial/civilian before they became 'military".
The other factor is whether Douglas took supplies from AE exclusively and didn't
let Hepolite in the door, and when did Douglas actually pack up manufacturing?
Peter & Rita Forbes
Been a while...
It seems the latter:
".....But the machine announced in the motor cycle press of September,
1945, was a very different matter indeed. The engine was a transverse
348 cc overhead-valve flat-twin, direct coupled to a four-speed gearbox
with final drive by chain. Full pivoted fork rear suspension was
incorporated, controlled by a longitudinal torsion-bar spring at each
side, enclosed within the frame cradle tubes......
"To the public, the Douglas appeared to be a totally new design, one
of the first such to appear on the post-war market. In fact, the engine
was basically one that had been designed in wartime, to power portable
generator plants. The designer was George Halliday (who, also, was the
patentee of the torsion-bar springing system)."
Great British Motor Cycles of the 50s - Bob Currie
Who, incidentally, was one of the first owners of the new model.
Wow who thought this ng was quite?
many thanks for the help
FPS are indeed a trade only outlet these days - mainly suplying to
But they dont seem to keep old catalogues - something I try to do (I
work for a factor in Hull)
And now I have some part no.s I can hopefully obtain the rings and re
assemble the engine.
One other question
The magneto seems to have no room for a condensor - I have been told
that it may be in the windings.
can anyone confirm this?
the mag is a BTH md2
thank you all again
The condenser is fitted internally behind the plate holding the points
and rotates with it. Strange looking beast - probably unobtainium.
Beware that the mag can be fitted 180 deg out, remove one of the
output terminal assemblies an check that the brass section of the rotor
is pointing to the cylinder that is at top of compression.
BTW, these engines have a bit of a reputation for difficult starting but
they will go if wound quickly.
I believe that the only bits that will swap directly from the T35 to the
motorcycle are the pistons, rings, conn rods & big end shells. Although it
looks alike, most of it is different & this explains why the WW2 Avro
Lancaster APU based on a Triumph twin (I really would like one of those if
anyone knows of one) has had such a poor survival rate & the T35's are -
well, not ten a penny perhaps, but certainly seven for sixpence.
The Triumph generator engine heads, barrels, pistons & all will swap
straight onto any eight stud Speed Twin crankcase & are still much sought
after for that very reason.
Useless fact: The T35 was part of a generating set which ran continuously
( didn't dare stop it no doubt!) on top of the Great Pyramid for months at a
time during the late war years.
Like the PU8, there are a surprising number about the place (I've got one)
but you never see them at rallies. Are they thirsty brutes like the PU8 - or
is it that they are as hard to start as legend has it?
Not quiet, just nothing much to say until the right button is pressed!
Thanks for that Tom, you have indeed answered a question which has
bothered me for some while. The sad thing is that I'm pretty sure that
very volume is lurking somewhere on either my or my father's book shelves!
Harking back to previous discussions on this matter, I still believe the
engine must have been drawn up with some thought to motorcycle use.
According to Pat Knight's A-Z, the FT35 was rated at 4-8hp depending on
speed. The 80 Plus and 90 Plus versions of the T35 motorcycle produced
around 25hp (legend has it that finished engines were dyno tested and
anything over 25hp got stamped up as a 90!). There aren't many purely
stationary/industrial units capable of a threefold increase in power
without a major redesign and it certainly wouldn't be the only time an
ostensibly military requirement was fulfilled with more than an eye to
future civilian use - who said Heathrow airport? Wash your mouth out!
kimsiddorn wrote (snip):
I know I've said this before but it can still be the 'same' engine
without necessarily sharing a single componant. Key thing is that when
it was on the drawing board, enough 'meat' was left in the basic design
to allow a substantial increase in power without altering certain key
dimensional relationships. For instance, I'm pretty sure any attempt
wring say 10hp out of a Norman T300 would be courting disaster!
I generally agree with Nick on this. The WW1 250cc ABC unit weighed 14lbs
bare of pipework carb & mag & 29lbs running. Normally generating at 1,200 &
3,600 rpm using the Marconi alternator then in common Army service, the
factory once ran one all night at 4,000 without a cooling fan and
reportedly briefly up to 12,000! If true, it speaks volumes for it breathing
"There aren't many purely stationary/industrial units capable of a
threefold increase in power without a major redesign"
The above statement got me thinking, so treat this purely as a
question, anyone know how much of a redesign the ohc Coventry Climax
fire pump engine needed before it was fitted in to the Hillman Imp? A
guy i once worked with raced an Imp and claimed it was relatively easy
to treble the power output of one . My Dad also drove am Imp for about
20 years and he loved it, would go anywhere and always got him home
from work in the snow, the only down side was you needed to keep a few
head gaskets in stock.
Sorry for going slightly off topic.
As a former Imp Sport and Clan Crusader owner I am well aware of the
strengths and weaknesses of the Imp engine and you are right; the Covvy
Climax FW engine is a stationary unit which proved amenable to some
pretty serious tuning without going bang - if not in the Imp then in the
original Lotus Elite and a variety of other sporting machines.
The Imp engine (derived ISTR from the FWMA) itself suffered somewhat
from the work Rootes did to adapt it for their mass production
ambitions. For instance they went to an open deck construction with
cast-in liners for the block which lead to the appetite for head
gaskets. If you intend getting serious power out of an Imp engine with
any degree of reliability, you are in for some pretty expensive
strengthening work such as wills rings up top and extra bracing with a
nice thick plate between the crankcase and sump down below.
If you find your copy of FMCOF take note that as released originally,
they were fraught and it took some major modifications before the bhp of
the 80 Plus & 90 etc were attained, some 5 years later.
As for stationary engine bhp as against automotive bhp, locally, there would
be 100+ 454 ci V8 engines driving wind machines for frost protection.
Their rating is 130 bhp @ 2800 rpm, whereas as automotively, the same
engine, with changed ancillaries etc, has had ratings of well over 400 bhp.
Even at 130 bhp, they are not renown for longevity, so the rating was a trifle
optimistic. Perhaps, 100 bhp would be a more ideal but then they wouldn't drive
the machines at optimum rpm.