Author Topic: Data sheet 350cc Douglas Bhp  (Read 694 times)

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Offline douglas1947

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Data sheet 350cc Douglas Bhp
« on: 09 Apr 2020 at 15:48 »
To get my 1930 Douglas 350cc road legal in Germany I will need some data, specially Bhp and weight and speed.
Can anyone please help with it?
I think the engine is still of same power output as on EW model?

Michael

Offline EW-Ron

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Re: Data sheet 350cc Douglas Bhp
« Reply #1 on: 09 Apr 2020 at 23:19 »
I don't think I've ever seen those officially listed anywhere, so hopefully someone will know.

However, the EW350 was built just below the 200 lb weight limit (except for the deluxe model),
and was sometimes mentioned as being capable of a nippy 60 mph on a good day,
and it takes about 10 BHP for a light motorcycle to do 60 mph, so that can't be far wrong.

I'd think the later model would be over that 200 lb mark, so don't underquote it ?
The Sport model with alloy pistons might better that 10 BHP also ?

Offline douglas1947

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Re: Data sheet 350cc Douglas Bhp
« Reply #2 on: 10 Apr 2020 at 15:33 »
Ron,

thanks for your posting. I think  too the power is around 8 to 10 bhp.
I know there was a Douglas advertisment  (from a German dealer) in the early 1930ies, including technical data.
Unfortunately I have only a copy for 600cc model S6;
so I still hope for help.

Michael

Offline tck

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Re: Data sheet 350cc Douglas Bhp
« Reply #3 on: 10 Apr 2020 at 18:54 »
The best place is in one of the two motorcycle papers the Motor Cycle or Motorcycling for the 1929 UK Motorcycle show (normally in the Autumn for next years models)
The Vintage Motorcycle club will have copies however I think the Library js closed because of the pandemic sometimes copies come up on ebay

Offline hoejmark

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Re: Data sheet 350cc Douglas Bhp
« Reply #4 on: 11 Apr 2020 at 11:18 »
Hi Michael
I just had a look in "The Book of the Douglas" by E. W. Knott (The Motor-cycle Library) 3' edition, 1930.
Page 17:  For the L3 model: Engine revs. at 60 mph approx. 4850.
Page 23:  For the H3 model: Max. speed approximately 55 - 60 m.p.h. solo
               Weight with acetylene lighting 240 lb.
               Weight with electric lighting 254 lb.
Page 5/6: "An engine capacity of 500 c.c. which, of course, means 5 h.p. according to A.C.U rating"
               According to this rating, a 350  c.c. engine should be rated to 3,5 h.p. I believe.

If you need, I shall scan these sides for you.

Hope this information will help you to bring your 350 cc on road.
S๘ren

Offline EW-Ron

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Re: Data sheet 350cc Douglas Bhp
« Reply #5 on: 11 Apr 2020 at 20:47 »
Its worth noting that the rated HP and developed HP are 2 quite different things.
Its interesting to wonder which the authorities would require ?

Even that ACU rating varied over the years.
By WW2, the 500cc models were 3.5 HP (like the Norton 16H and BSA M20)
and the 350cc models were 2.75 HP. 
A 600cc like the Norton Big4 or BSA M21 were rated as 4 HP.
(hence even the Big4 name).

Apparently these ratings were something to do with steam engines,
and in the beginning were solely based on bore sizes.
So it mattered not one jot whether it was a long or short stroke...

Offline douglas1947

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Re: Data sheet 350cc Douglas Bhp
« Reply #6 on: 14 Apr 2020 at 12:42 »
Hi S๖ren,

thanks for your offer to scan and send me the informations  you got in your "Book of the Douglas" (1930 Ed.). I do not own this book.

Unfortunately the HP info will not help. So I still hope to get something about the Bhp.
It is right, what Ron tells.
There was also a HP classification in the early times of motoring in Germany (until ca. 1930?).
I think it was used for the different taxes of the small and bigger engines.
May be it is the power of the engine at ca. 1000rpm?

Michael

Offline Eric S

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Re: Data sheet 350cc Douglas Bhp
« Reply #7 on: 14 Apr 2020 at 15:27 »
Michael
How accurate do you need to be? In any case I doubt they can check your claim. Why don't you just go to a close figure?
I don't think taxes will be affected by your claim.

Offline hoejmark

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Re: Data sheet 350cc Douglas Bhp
« Reply #8 on: 14 Apr 2020 at 17:52 »
Michael
I scanned the relevant pages and emailed to you.

I also agree that ACU ratings are not equal to bhp, but if authorities need bhp, why not then just claim 10 bhp.
S๘ren

Offline yosemite

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Re: Data sheet 350cc Douglas Bhp
« Reply #9 on: 14 Apr 2020 at 22:04 »

This page on wikipedia, dont know how accurate or relevant  it is,  gives the formula used in various places to calculate tax horsepower for cars, cant find any information about motorcycles, but I think the early calculations may have been similair for motorcycles
       <<https://en.wikipedia.org/wiki/Tax_horsepower>>

Paul

Offline cardan

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Re: Data sheet 350cc Douglas Bhp
« Reply #10 on: 14 Apr 2020 at 22:48 »
gives the formula used in various places to calculate tax horsepower for cars

The various car formulae were never applied to motorcycles. Instead, once things settled down around 1910, power was just linked to capacity. The main categories were:

250cc = 2 1/4 h.p., 350cc = 2 3/4 h.p., 500cc= 3 1/2 h.p., 750cc = 6 h.p., 1000cc = 8 h.p.

This scheme was used until the mid 1920s when there was a shift to a new scheme - I think of it as a penny per cc:

249cc = 2.49 h.p., 348cc = 3.48 h.p., 494cc = 4.94 h.p. and so on.

In the early scheme the h.p. ratings were always expressed as fractions; in the later scheme as decimals. This avoided (some) confusion.

It was extremely rare for a manufacturer to use anything other than these figures (like the actual h.p.) to describe a machine, in advertisements, factory literature, road tests etc. An exception was for racing machines.

For Douglas the change was made between the 1924 catalogue (when the 348cc TS and CW were listed as 2 3/4 h.p.) and the 1925 catalogue (when they became 3.48 h.p.). The RA went from 3 1/2 h.p. to 4.94 h.p., and the OB from "Six Hundred" (4 h.p.) to 5.96 h.p. The only "actual power" listed in either catalogue was 25 b.h.p. for the RA25.

In 1928 Douglas tried to buck the trend of two-decimal-place power ratings by calling the 596cc models 5.9 h.p. and the 348cc models 3.5 h.p., but I doubt this lasted. The EW and its variants are best described as 3.48 h.p.

Cheers

Leon

Offline EW-Ron

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Re: Data sheet 350cc Douglas Bhp
« Reply #11 on: 15 Apr 2020 at 06:12 »
JAP stuck with 8 HP for twins for quite a long time, that was still 1000cc post WW2  ?
The mighty 8-80 comes to mind, 1000cc and 80 hp (for racing)

So did only some makers adopt a new system ?
Or some makers not discard the old system ?

Offline cardan

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Re: Data sheet 350cc Douglas Bhp
« Reply #12 on: 15 Apr 2020 at 10:53 »
Neither. JAP held on to the "8" in the name of various engines because it was famous in racing history. So the 1929 JAP 8/45 racing engine, which had a capacity of 981cc, was described in JAP advertising as 9.81 hp.

Another example that comes to mind is Norton, who hung on to "Big Four" for its 600-ish cc bikes into the 1950s.

Leon

Edit: Of course all this HP nonsense went away in the 1930s when bikes were mostly referred to by their capacity.
« Last Edit: 15 Apr 2020 at 11:00 by cardan »

Offline douglas1947

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Re: Data sheet 350cc Douglas Bhp
« Reply #13 on: 15 Apr 2020 at 16:41 »
S๖ren,

thanks for sending the scanned pages.

I think also, it is realistic  10 Bhp for the 350cc engine, but  you know most authorities want a piece of official paper and not what I say or believe!

Michael

Offline Hutch

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Re: Data sheet 350cc Douglas Bhp
« Reply #14 on: 16 Apr 2020 at 03:31 »
Hi Michael,

I found this advertisement for the EW for 1927 and states that the power is "well over"10 BHP, given the possible over enthusiasm of the advertising people at Douglas, I would round that figure down to 10 BHP?

I have found nothing so far that states the actual BHP of the later 350cc side valve engines but will keep looking.

cheers

Ian
« Last Edit: 16 Apr 2020 at 04:31 by Hutch »

Offline cardan

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Re: Data sheet 350cc Douglas Bhp
« Reply #15 on: 16 Apr 2020 at 04:32 »
The 1926 full catalogue has the same guff about "well over 10 b.h.p." in the specifications, but on page 21 it simplifies things and just says "10 b.h.p."

Interesting alloy pistons for the EW in 1926, but cast iron in 1927.

Leon

Offline douglas1947

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Re: Data sheet 350cc Douglas Bhp
« Reply #16 on: 16 Apr 2020 at 15:41 »
Hi Ian and Leon,

thanks for the informations about the 10bhp.
I think I can use it.
I believe the engine do not really had a change in power output; most of the important engine parts from EW to H3 look the same. My engine (ER812) has still cast iron pistons!

Michael

 

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