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Ron

My latest project

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I have acquired this engine from Tasmania. It's the remains of an engine from a Royal Enfield Experimental lightweight that only four were known to have been produced.

 

In a nut shell the bike was built from the bottom end of a 250cc Model D engine with the slimmed down flywheels and the barrel and head from a 350cc Model C. Which was installed in a Model D frame with Model C forks and wheels.

 

As if I haven't got enough to do, I have decided to build a replica of the bike, and I am gathering parts and information. I am getting lots of help and encouragement from Jan who runs the RE register.

 

I'm desperately seeking a Model C or CO front wheel or just a bare hub, if anyone can help. Cheers Ron

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Well ok Starfire.

 

So far I have acquired a model D frame (ex WD as luck would have it) with engine for donor parts and a load of other model D stuff. Model C front forks and a C rear wheel which has had to have the hub narrowed by 1" to fit the frame. I've also picked up the correct ally brake plates and Jan had donated some nice correct fork parts. Unbelievably I found the correct centre stand in Austria. I'll use this thread to post future pictures as I proceed. Ron

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Cheers Ian. I think we did say a brief hello at Netley. But then you were gone! Sometimes life just gets a bit too hectic with friends....But I love it. Ron

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Ron, Yes we did say hello at Netley and I intended coming back to see you after lunch but I had purchased a few heavy bits (oil etc.) and I was parked in the far corner of the parking area and after dropping them off felt to lazy to come back but hopefully I will see you at a few of the events next year as I now have a trailer for the two bikes so I can now travel. I have taken the 3HW to a couple of local shows that I could ride to and enjoyed them. Ian C.

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Hi Ron......a brave undertaking !

 

Has Jan confirmed your engine number as being one of the experimental WD versions...? And do we know how it ended up in Tasmania ?!!!

 

Were the barrel and cylinder head originally cast in aluminium alloy for weight reduction ? Also, the flywheels lightened....Looking at the period images the head and barrel look to be aluminium.....?

 

I'm drawing comparisons here with the 250cc Matchless and 350cc Norton of the same era.............this is before economies began to bite affecting even prototype development...........:D

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Hi Steve. Hopefully Jan will respond also. According to his report, the Ally barrel/head was not all that successful and the iron parts were also used.. Also only two of the four bikes produced have had their numbers recorded. Of course there might have been some extra engines built. The flywheels are slimmed down Model C. I have been relaying all information to Jan as I find it. Ron

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What a wonderful project. Great engineering, no doubt the final result will make the inevitable frustrations worthwhile

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A lot of the enjoyment is researching and working out how they were built. I have three very good pictures and the information that Jan and I work out between us. I am currently working on how to make the valve lifter work. I'll post a picture when it's done. Ron

Edited by Ron

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Jan has used some trick photography and worked out that the rear carrier is made from thinner tube than a standard RE carrier. We noticed also that it only has two top rungs instead of the normal three.....All done in the interest in saving weight I guess.

 

Jan has also used his skills at producing this lovely replica carrier for me....... Thanks a million Jan.

..Ron

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Ron asked me to add some information on this motorcycle’s history. Here it is:

 

In July 1938 the International Six Days Trial was organized in Wales. The Nazis realised that motorcycles were going to play a small but significant role in modern warfare, so they encouraged the Fédération Internationale de Motocyclisme (or FIM, the organiser of the ISDT) to create a Trophy for the top military team. This Trophy was called the Hühnlein Trophy (after Adolf Hühnlein, the Korpsführer or Corps Leader of the National Socialist Motor Corps or NSKK). The British Army was also convinced that the ISDT was an excellent test of military motorcyclists’ combat readiness. So the Army entered a team with three soldiers from the Royal Tank Corps. And although they had done their best, the Army team was poorly prepared, and their performance proved that military riders, machine specifications and preparation had fallen far behind their civilian counterparts…

 

Due to the facts mentioned above, the “Mechanization Board commenced an investigation with the possibility of producing an improved type of W.D. motor cycle. Considerable benefit would accrue if the weights of the machines were drastically reduced. As a result of the investigation, it was decided to ask the following firms to submit specifications for solo motor cycles specifically designed for W.D. use:

- Ariel Motors Ltd.

- George Brough

- B.S.A. Cycles Ltd.

- Enfield Cycle Co. Ltd.

- Norton Motors Ltd.

- Triumph Engineering Co. Ltd.

 

It was deliberately decided not to influence manufacturers in any way by stipulating performance or other requirements with one important exception that an all-up weight of 250 lbs. should not be exceeded.

 

TYPES PRODUCED AND TESTED: Of the designs put forward, those of Enfield Cycle Co. Ltd., Norton Motors Ltd. and the Triumph Engineering Co. Ltd. were selected and prototype machines were ordered for trial at the W.V.E.E..” (Source: a Ministry of Supply (T.T.2) Report from January 4th 1944). The official testing procedure was quite serious:

 

- First, the machine was run in for 500 miles.

- Then there were some performance tests: average speed on and off road, timed hill climbs and a 100-mile petrol consumption test.

- These were followed by 5.000 test miles, of which 25% were off road.

- After this 5.000 miles test run, the performance tests were repeated, and the petrol and oil consumptions were compared with those recorded during the initial performance tests.

- This was followed by another 5.000 miles test run, again with 25% off road miles.

- The performance tests were carried out again, and the results were compared with the previous results.

- Then the machine was completely stripped and each component was measured and checked for wear.

 

The Royal Enfield prototype (frame number #101, engine number #101) was delivered on August 17th 1939 to the Mechanisation Experimental Establishment (M.E.E.). After the run-in period and a series of performance trials, the Enfield was tested for 2.971 road miles and 709 cross-country miles (or a total of 3.680 miles).

 

On December 7th 1939, the report concluded that “The lightweight 350 c.c. motor cycles are definitely easier to handle than the standard 500 c.c. W.D. Norton 16H machine, while their performance is as good. Of the three machines the Triumph, which is not only the lightest but also has a twin O.H.V. engine, has the best performance. The Royal Enfield and Norton machines have single cylinder side valve engines. … Road and cross-country mileage is proceeding.”

 

During this further testing, (when the milometer read 4.967 miles to be precise) Enfield replaced the standard cast iron cylinder by an aluminium cylinder with a steel liner. No doubt this action was taken in an effort to reduce the weight below the 250 lbs. target…

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In early 1940, Enfield and Triumph both delivered two extra experimental lightweights to the B.E.F. in France, for trial. Considering the delivery date, it would be reasonable to assume that the two Enfields were also equipped with an aluminium cylinder. The Royal Enfield contract number was C/6718, the demand date and the contract date were both 1/4/1940, and there was a footnote in the M.o.S. ledgers: “delivery already been arranged”. (Source: M.o.S. contracts ledgers, National Archives). The exact delivery date and the exact frame numbers and census numbers are unfortunately unknown.

 

I have found these pictures of an “experimental lightweight” in the Royal Enfield Owners Club (REOC) Archives, and I have reason to believe that this may have been one of the two contract C/6718 motorcycles, which were similar to the C/3585 bike.

 

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On May 12th 1940, Hitler invades France. By May 14th 1940, the German tanks had crossed the river Meuse and had opened up a fifty-mile gap in the Allied front. Six days later they reached the Channel. When he heard the news, Winston Churchill, who had just become prime minister, ordered the implementation of Operation Dynamo: a plan to evacuate the British Expeditionary Forces troops and their equipment, along with the remnants of the French army, from the French port of Dunkirk. Between 27th May and 4th June, a total of nearly 700 ships brought 338.226 people back to Britain. All heavy equipment was abandoned and left in France. Ellis's official history "The War in France & Flanders 1939 - 1940" gives the following statistics:

 

Vehicles shipped to France 68618

Lost 63879

Brought back 4739

 

Motorcycles 21081

Lost 20548

Brought back 533

 

Obviously the test results for the two contract C/6718 motorcycles that had been sent to the B.E.F. in France were never received…

 

But the May 23rd 1940 report on the C/3585 “pilot model” gives us the following information: “Having completed its life test of 10,000 miles, the Royal Enfield 346 c.c. motor cycle, W.D. No. C.3925599, was subjected to a repetition of certain performance trials. … The Royal Enfield 346 c.c. lightweight motor cycle has fallen off slightly in performance, but its original petrol consumption is practically maintained. … The machine is now being stripped for workshop inspection.”

 

The June 6th 1940 report gives us some more information on the result of the workshop inspection:

“The above named machine, having completed its test mileage, has been dismantled and examined in accordance with the instructions contained in Schedule No.B.7. of “M.B. Vehicle Test Instructions, 1937” … In comparison with other machines of the class, this machine has stripped in fairly good condition, apart from cylinder wear, which is considered excessive as this component has only completed 5,235 miles of the trial. … Conclusion: The employment of an iron cylinder liner does not appear to be very satisfactory in comparison with the standard cast cylinder. The defective oiling system to the big end bearing appears to have been overcome after running three bearings during the trial, and it would appear that if the cylinder wear can be improved this machine should be capable of withstanding the rough handling and hard work the machines have in the Service.”

It is interesting to see that the motorcycle press were invited during one of the test sessions. Arthur Bourne (“The MotorCycle”) and Graham Walker (“MotorCycling”) both published an article on this subject in their 25th July 1940 issues.

 

Arthur Bourne wrote:

 

“Taking in alphabetical order those machines under test on the day of my visit we have: a 350 c.c. overhead-valve B.S.A., weighing, with cast iron cylinder and head, 301 lbs. (this machine had just arrived and was being run-in); a 250 c.c. overhead-valve Matchless with a weight of 282 lbs., and a 350 c.c. vertical twin Triumph, weighing, with cast-iron cylinders and head, 263 lbs. There is also a 350 c.c. side-valve Royal Enfield of 276 lbs., which has been stripped for its all-embracing examination and measurement of wear, and which, like all the foregoing, has also been approved for production and therefore use by the Army. The weights, by the way, include petrol, oil and tools.

All these extremely interesting machines have been developed in response to requests for suitable Army motorcycles weighing 70 to 100 lbs. less than the existing standard W.D. models – machines which are therefore easier to handle and, when necessary, manhandle. The weight to which designers had to work was 250-256 lbs., according to size of machine. This was before the light alloy position became difficult. Now cast iron must replace the light alloy used for various parts, and an appropriate increase in weight has been allowed.”

 

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Both articles show pictures of the Royal Enfield “pilot model”. But on the day the press was there, it was completely dismantled, after it had finished its 10.000 miles test. Both pictures don’t show a lot of details, but it can clearly be seen that the saddle is no longer the rubber item made by Dunlop. In M.E.E. test report B.382 (Source: National Archives), I found this information:

 

“ An aluminium saddle for fitting to the W.D. Norton 16H Motor Cycle, was supplied by Norton Motor Cycles Ltd., for test and was found to be unsatisfactory. A steel saddle was then supplied with a vulcanised rubber top. This again was a most uncomfortable saddle to ride on, and Norton Motor Cycles Ltd. Submitted a further sample steel saddle with a vulcanised rubber top, but modified in shape. At the same time a similar type of saddle was supplied by the Enfield Cycle Co. Ltd. For fitting to the 350 c.c. Royal Enfield lightweight motor cycle.”

 

The weight of a standard saddle was 4 lbs. 14 oz., the Norton saddle was 5 lbs. 8 oz. while the Enfield saddle was “only” 4 lbs. 2 oz. Road miles and cross-country miles were covered between June 3rd and August 12th. The conclusion of the M.E.E. was quite clear:

 

“A metal saddle with vulcanised rubber top is considered most unsatisfactory for W.D. use, and apart from the possibility of it being more easily decontaminated than the standard saddle, shows no advantage over the standard saddle. It is most uncomfortable for the rider, 20 miles being about the limit of endurance over cross-country.

It has not been found that the standard saddle fails to stand up to cross-country work. While one or two standard saddles on test machines have not proved satisfactory, the large majority have been in good condition at the end of reliability mileage.

It is noted that the main trouble experienced with the standard saddle has been the failure of the saddle springs and these are the same as fitted to the metal saddle.

Provided that suitable measures can be taken to make it practicable to decontaminate the standard saddle, it is recommended that a metal saddle be no longer considered.”

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After the 10.000 miles of this “pilot” test, all tested models were “approved” by the M.E.E.. In June 1940, a second “production” test was planned with motorcycles that had a less “exotic” specification (read: less aluminium parts). Royal Enfield (C/7972), BSA (C/7975), Matchless (C/8019), Triumph (C/8020) and Norton (C/8031) had all been asked to make one (two for Triumph) extra prototype(s) for further evaluation. Again, all motorcycles were tested extensively, but this time, “only” 5.000 miles had to be covered, of which 50% were off road. And again, each motorcycle was completely dismantled after these 5.000 miles to check all components.

 

Let’s have a look at this contract C/7972 Royal Enfield experimental lightweight “production model”: The demand date for this contract was July 8th 1940, and the contract date was August 15th 1940. But the exact delivery date is unknown. Delivery may have taken place in late June, as the contract book has “delivery already been affected” written next to the demand date. The frame number of this motorcycle was #303, engine number DC303, and the military census number was C4328451. This motorcycle was very similar to #101, but all problems from the pilot test model should have been affected, and a cast steel item replaced the aluminium cylinder that had been used in the second half of the pilot test.

 

More detailed information about the “production test” comes from the M.E.E. test report B.492 (Source: National Archives):

 

By July 17th 1940, the running-in and the performance tests had been carried out. The test report states that “A production model Royal Enfield 346 c.c., S.V. lightweight motor cycle was received for test to compare its performance and reliability with that of the pilot model previously tested. … The production model Royal Enfield 346 c.c., S.V. lightweight motor cycle compares favourably in every respect with the pilot model. It is easy to handle for an average rider, and has plenty of power at low engine speeds. … The machine is now carrying out reliability mileage.”

 

The 5.000 miles had been covered by mid-August 1940, and on August 11th – 12th a repetition of the performance test was scheduled. The report of August 17th 1940 states that: “Having completed its reliability test of 5,000 miles, the Royal Enfield 346 c.c. S.V. Lightweight motor cycle was subjected to a repetition of certain performance trials in accordance with the terms of Schedule No.B.4 (b) of M.B. Vehicle Test Instructions, 1937. … Object of trials: To ascertain to what extent the machine under test has maintained its initial standard of performance. … Further action: The machine is now undergoing stripping and final examination.”

 

“Observations and recommendations of T.T.2: It is noted that the performance of the Royal Enfield lightweight motor cycle referred to in the above report, has improved on its initial performance, and that the only defects observed during the 5,000 miles running have been of a minor nature. This machine can be recommended as suitable for W.D. use, subject to satisfactory results being observed when the machine has been stripped.”

 

“Conclusions of M.E.E.: The Royal Enfield 346 c.c. S.V. Lightweight motor cycle has not only maintained its initial performance, but its performance has slightly improved. Its petrol consumption has been fairly well maintained, and its oil consumption is very good, and remained constant throughout the test.”

Things were still looking good then… But the September 1st 1940 report on the result of the stripping and final examination sounds less optimistic: “The above named machine having completed its test mileage has been completely dismantled and examined in accordance with instructions obtained in schedule B.7 of M.B. Vehicle Test Instructions, 1937.”

 

“Observations & recommendations of T.T.2: The condition of this machine at the conclusion of trials has been noted and it is considered that the machines can be recommended as suitable for W.D. use for emergency purchases only.

 

The attention of the manufacturers is being drawn to the following points:

1. The cylinder bore wear at .001” per thousand miles is considered to be excessive as is the piston ring wear.

2. The pitting of the layshaft constant mesh pinions.

3. The inadequate strength of the rear forks and front fork girders.

4. The unusual trouble of a bent rear wheel spindle.

5. The weakness of the welded petrol tank seams.

6. The poor alignment during assembly of the chain case causing the main driving chain to foul.”

 

“Conclusions of M.E.E.: When compared with the machine reported under M.E.E. Report No.B.493/2 (the Matchless lightweight, ed.), the Enfield bicycle can only be assessed as fair. It has needed far more workshop attention to maintain it in running order and appears insufficiently robust to withstand Service conditions.”

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Resumed: frame #101 / engine #101 was the “pilot” model that went through a 10.000 Miles test. Then we have two motorcycles (frame / engine numbers unknown) that were sent to the B.E.F. for testing, and frame #303 / engine #DC303 was the “production” model that went through a 5.000 Miles test. The number #101 is a “typical” number for a “first” motorcycle, but was DC303 a coincidence (a set of Model D crankcases with engine number D303 that Enfield had in stock), or was it deliberate, and did it mean that this was the third delivery of this model? If it was a coincidence then Ron’s DC277 could have been one of the two BEF bikes. But if #303 indicated a third delivery then it would be reasonable to assume that the B.E.F. bikes were #202 and #203…?

 

So if it was one of the B.E.F. bikes, how did the engine end up in Tasmania? If it was with the B.E.F. in France when Germany invaded the Low Countries, then it will have been left behind. Many BEF vehicles were set on fire to prevent that the Germans would still use them. But quite a lot of B.E.F. vehicles were “recycled” by the Germans, and very often ended up somewhere on the Eastern front…

 

Another theory could be this one: all contracts from this period for the British Army are well documented. There were also some contracts for the Australian Army (notably a Royal Enfield WD/C contract and a Royal Enfield WD/L contract), but there is hardly any information available on these Australian motorcycles / contracts. Could it be that Enfield also sent one or two of these lightweights to Australia for testing…? This theory could explain why we found this one in Tasmania…

 

I know that there is a book (“2nd AIF MT Census”) in the Australian War Memorial in Canberra, in which every motorcycle that the Australian Army received from England during that period was registered. I have seen pages from this book, and it contains impressed civilian motorcycles as well as official Army contract bikes, from different makes.

 

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Our hope is to find somebody in Australia who could copy (photograph) all pages of this book for us. It could include a vital link to the history of this unique engine!

 

Jan

Edited by rewdco

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Whew! That's chapter and verse folks! And that's just a fraction of Jan's report, which is an excellent reference especially if you own or are interested in WD Royal Enfield's. But still worth reading/owning for many more WW2 historical facts.

 

Thanks Jan.

 

Ron

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Today I finished putting the engine back together. The exhaust valve lifter and return spring that I had to invent seems to work well, and a friend is hewing me a tappet chest cover from a block of 8mm ally. The head needs some fins repaired, and I wont fit it till the engine is in the frame with the mag all timed up.

 

My mag chain cover was so badly corroded that I've simply sanded it, filled the large pock marks and sprayed it with high build primer, then ally paint and petrol proof lacquer. It will just have to do until I find a decent replacement. Ron

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EXP DC 059.jpg

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Ron, Jan

 

Regarding the Australian history. It may be worth contacting Mike Cecil, he was quite high up in the AWM and has been a huge help to me with the Scout and Matilda history. If he couldn't help directly I'm sure he could point you in the right direction.

 

I know now he's on MLU. I can help with an email address if you don't have it already.

 

Nice project.

 

Ben

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Yes thanks Ben. I know Jan will be on the case. I'll email you about those other items.

 

Cheers Ron

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I was very lucky to have found a front wheel on ebay. including bearings, spindle and speedo drive gear...All in near perfect condition.

 

Ron

EXP DC 143.jpg

EXP DC 143.jpg

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I now have my narrowed rear hub built back into its rim. That's just a dummy spindle in the picture, I've had to modify the original spindle also. I've purposely left the overall length the same until I work out and add the wheel adjusters. Which I can see in the pictures are modified from the model D type of pedal cycle type. Ron

EXP DC 145.jpg

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By lining up 3 - 1/4"X BSCycl thread nuts and welding them on the frame each side, I think the rear wheel adjusters fit the bill. Just need to get the correct looking adjuster bolts. Ron

EXP DC 152.jpg

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