Author Topic: Dragonfly prototypes  (Read 330 times)

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Offline AndyMorgan

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Dragonfly prototypes
« on: 18 Jan 2021 at 16:07 »
Since selling a pair of Pistons on eBay I have been corresponding with a dear old chap who has taken on my engine cases and crankshaft for an early Dragonfly  6/1007 to rebuild. This had Mk5 barrels and the crankshaft had plane white metal bearings (judging by their condition it is no wonder this wasn't adopted in production). Anyway, he is in the process of rebuilding a number of Dragonflies and is keen to get any information or parts from the prototype machines. Let me know and I will pass it along.   

Offline eddie

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Re: Dragonfly prototypes
« Reply #1 on: 19 Jan 2021 at 14:34 »
As I understand it, Douglas provided a donor Mk5 machine to Reynolds Engineering, and commissioned them to update the design - basically, this machine was a 'Dragonfly' with a standard Mark engine and gearbox, and wheels. Further development took place and a couple of photos exist of the bike still with a Mark engine, but fitted with coil ignition and an AC generator. (I have a bottom end for such an engine). By mid 1954, Douglas had produced 6 prototype machines (which at a quick glance looked like the Dragonfly) for display at that year's motorcycle show. At that time, they were badged as the 'Dart' - but Douglas were forced to rename them due to that name already being used by another manufacturer. These 6 machines, whilst looking like the Dragonflies we know, were different in many details from the production machines (frames, engines, gearboxes, exhausts, petrol tank, toolbox,  headlight nascelle all being different). Of those 6 machines (engine/frame numbers 1001 - 1006), I believe 3 still exist (one black and silver, and one stone and green) in the Bristol area. The third machine (colour unknown) is somewhere in mid Wales.
  After the show, and before production commenced, more development took place. Filling the engine with oil was awkward, so the filler plug was moved to make it more accessible. Likewise, the carb main jet was difficult to get at, so the carb was set at a slightly steeper angle - which also entailed a modification to the front of the toolbox. The bottom flange of the cylinder barrels had to be cut back to enable them to be removed and clear the frame tubes (without lifting the engine). Tube layout for the pillion footrests was altered, and the exhaust pipes shortened so that the silencers could be mounted more securely, directly to the footrest tubing. Early production machines still retained the 'Douglas' brakes whereas later machines were fitted with 'British Hub' brakes. There were also early and late type gearboxes. Early machines only had a taillight whereas later ones had the luxury of a stoplight.
   As already stated, Douglas exhibited at the 1954 show, but it was a rushed attempt to get a new model in the public eye. Production machines did not emerge until almost half way through 1955 (my early model being at the dealers late July 1955). It is rumoured that within about 18 months actual production had stopped, and machines were being built from the accumulated stock of spares held in the factory. As is now well known, Pride and Clarke bought the majority of the remaining stock when the factory was taken over by the Westinghouse Brake and Signal Company - hence the number of TYP, TYR, ULL and UJJ registrations on the surviving machines.
   Whilst the Dragonfly is not the swiftest thing on 2 wheels, it is one of the most comfortable. Several of us LDMCC members have had great fun competing on our Dragonflies in the ACU National Rally and getting Special Gold Awards for gaining maximum points - one year, gaining those points entailed riding 130 miles to the start, then covering 540 miles on the rally, then another 240+ miles to get back home - a total of about 900 miles from start to finish in 32 hours. It was great fun pitting our sluggish old 350's against the modern plastic rockets (and still beating them to the next checkpoint!). We were certainly a lot fresher than others riding the modern hardware.
  Had the Dragonfly been blessed with a longer development program, it could have been a much improved machine - us owners have had another 60 years to identify (and cure) most of the problems - sadly Douglas were never given that time!

  Eddie.

P.S.   From what I have already said, it looks as if your engine (1007/6) could be from the first production machine.  Also, I have heard of several engines being modified to plain bearings - the biggest problem is the low pressure output from the Douglas oilpump - only about 6 - 9 psi.
« Last Edit: 19 Jan 2021 at 14:44 by eddie »

Offline EW-Ron

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Re: Dragonfly prototypes
« Reply #2 on: 20 Jan 2021 at 06:06 »
Oil pressure is not entirely essential for plain bearing motors, as long as there is is some flow,
even a mere trickle can suffice.

A number of early plain bearing motors, inc the T Model Ford and early Hendersons
only had a splash lube type of oiling system - and did some big mileages.
Provision is made for the splash to get to EVERY place where some lube is required however..
A lot of early roller bearing motors in the veteran and vintage years ditto.

What is troublesome is if the oil splash is absent for any length of time.
As horsepower outputs rose however, pressure with flow was a useful improvement to reliability.

Are there pics anyplace of these prototypes ?
I didn't realise the Dragonfly was such a latecomer to production.

Offline AndyMorgan

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Re: Dragonfly prototypes
« Reply #3 on: 20 Jan 2021 at 12:53 »
Many Thanks for this I will pass it on