Edgar Franks - Norton Engineer

I was in a conversation with an old racer the other day about the development of Manx Nortons and the name Edgar Franks cropped up. I am sure many would have heard of Joe Craig who developed Norton’s Works racing machines, but the name Edgar Franks would be known by very few.

Edgar was a mechanical engineer at Norton who worked on many machines over the years. It was Edgar Franks who assisted Arthur Carroll and Joe Craig in the re-design of the Norton over-head-cam engine after Walter Moore left for NSU. Edgar also redesigned the Norton range for 1931. Changes he made included making new lower frames which made the rider adopt the knees fully bent riding position due to a saddle height of only 26.5”. Other changes included Norton making their own hubs, brakes and Webb-type forks, instead of buying in components.

In 1933 Franks designed the Norton model 50 350cc OHV motorcycle. It was also Edgar Franks that designed the Norton oil-bath primary chain case which was introduced in 1934 and used until the 1960’s. The first telescopic forks for a production Norton machine were designed by Edgar Franks for the 1940 Manx model. 

In January 1950 it was Edgar Franks who took Rex McCandless, the Featherbed frame and Rex’s jigs to Reynolds Tube Company. Reynolds went on to manufacture the Featherbed frames for the Manx Norton racing machines.

One of Edgar Franks’ biggest contributions was in the development of the Manx Norton production racing machines. For over two decades Franks continuously improved Manx to keep it competitive. It is a common mistake that Joe Craig developed the Manx machine – instead Joe Craig was in charge of the Works racers. So without Edgar Franks hundreds of racers would not have had such an effective racing weapon as the Manx Norton.

Charlie Bruce and the 250cc DOHC Velocette

This post is a brief introduction to the final Velocette racing motorcycle built by Charlie Bruce.

Charlie Bruce from Motherwell was a stalwart of the Scottish 250cc racing class. It was Charlie Bruce who go round the paddocks ensuring there was a good entry for the 250cc class throughout the 1950’s. Without Charlie’s passion for motorcycle racing, the 250cc racing class in Scotland would have probably ended.

Charlie Bruce at Beveridge Park

Charlie worked for the council in Motherwell, but had had tough times in WW2. He was at the ‘Death Railway’ (Burma Railway) and was a Prisoner of War. Charlie had some terrible treatment and it was only his dream of racing motorcycles that helped him survive his ordeal. During his time as a POW Charlie even produced the drawing of his racing machine using charcoal.

Charlie Bruce

Charlie Bruce was a very good rider winning the Scottish 250cc Championship in 1950 on his homebuilt bikes. Charlie was a Velocette enthusiast and until 1958 he rode an ex-WD pushrod Velo. There were various incarnations of this machine – I might go into these in another post at a later date.

Charlie was good friends of Joe Potts and much of the preparation work on his machines was done in Joe’s Bellshill workshop. Charlie became heavily involved with Joe’s own racing team, helping riders such as Bob McIntyre, Alastair King and Jimmy Buchan. Charlie was very well liked in paddocks across the UK and was well known by all the trade barons. It was because of this that Charlie became a bit like team manager for the Potts setup.

For 1958 the Potts team had been doing much work (see posts on the Desmo etc) developing new bikes. Joe made sure Charlie was not forgotten and talked with Bob McIntyre about getting Charlie a bike to replace his old pushrod Velocette. Bob organised the purchase of an ex-Works 250cc NSU Rennmax twin engine from Reg Armstrong for Charlie. Charlie kindly refused the NSU engine, saying he would rather finish second on a British bike than win on a German one! (he was an ex POW from WW2). It was back to the drawing board to find something for Charlie. Bob then located a 250cc DOHC Velocette engine that had been built by Doug Beasley. Bob paid Doug £257 for this engine.

This DOHC Velo engine was to be the basis of Charlie’s new machine. The engine had a bore and stroke of 68mm x 68.25 mm respectively. The crankcases, cylinder barrel and timing gears were all Mk8 Velocette KTT items. A special flywheel assembly was machined in order to reduce the engine stroke and the barrel was sleeved from the standard 74mm bore. An old Velocette factory racing cylinder head casting was machined and fitted with KTT valves which were reduced in size. The cambox was of Beasley’s own design and was clamped to the cylinder head by 16 ¼ inch BSF studs and nuts to faces machined on cylinder head. Standard Mk8 bevel gears took the drive from the crank to the cambox, but the flanged bronze bush which normally support the vertical bevel shaft were replaced by taper roller bearings. A 1¼ inch Amal GP carburettor was used with the engine. The engine produced 26.5 BHP at 8,500 RPM.  A should add here that this was the specification of the engine as first used in 1958. Over the coming years the engine had the Bellshill treatment and was modified heavily for extra performance.   

To house the engine a Razorblade frame (like the ones Bob was using for the 1958 season) was built by Alec Crummie. A Velocette 4 speed KTT gearbox and clutch was used. Shortened Manx Norton forks were fitted. A Manx 2LS front brake and Ariel/BSA type rear brake were laced into 19” rims. A Lyta aluminium petrol tank housed both the petrol and the engine oil in a section at the back of it.

I will add a follow post sometime giving some ideas what happened to the bike.

EMC Split Single engine

This post is detailing an engine which is a bit of a curio from the early 1950’s. The split single engine is a version of a two-stroke engine which uses two cylinders, but share only one combustion chamber.  The EMC split single engine here is based on some Puch components.

Joseph Ehrlich EMC 125cc split single development engine

In the split single intake charge enters the crankcase below the skirt of the front piston. The charge receives primary compression before passing through transport ports into the rear of the two cylinders. The charge travels up the rear cylinder and then transfer to the front cylinder via the bathtub shaped combustion chamber. The exhaust gases then leave the exhaust ports in the front cylinder. The front piston controls both the intake and exhaust ports, whilst the rear piston controls the transfer of charge from the crankcase to the rear cylinder.



Twin exhaust ports



Twin intake ports on side of engine

Asymmetrical port timing is achieved by pivoting the intake ‘slave’ connecting rod on the back of the main exhaust connecting rod. This allows the exhaust port to open before the transfer of fresh charge into the rear cylinder and also allow the transfer port to stay open whilst the exhaust port has closed.

A 'single cylinder' with two cylinders!

 

Combustion chamber

The benefit of the split single cycle comes with the separation of the intake and exhaust process. This allows much improved low speed and low load engine performance as well as reduced hydrocarbon emissions. Two-stroke technology in the early 1950’s was limited, as rotary valves and expansion chamber exhaust design was yet to be used widely. Instead conventional two-stroke technology often consisted of deflector type pistons to prevent intake charge leaving the exhaust port immediately.

It is clear that the split single has many issues which prevented it becoming widely used. The engine is larger and heavier due to the multiple pistons. High engine speeds are limited by the design and engine friction is higher than with a conventional two-stroke engine. The intake charge also has a tortuous path and combining this with a very large combustion area leads to poor efficiency.

The Anatomy of a 1954 Works Norton Featherbed frame

I thought I would make this post to give an idea of the difference between a Works Norton racing machine and its Manx production racing cousin.

We are only looking at the frame here for a 1954 500cc Works Norton. Striking differences can be seen immediately between it and a Manx Featherbed frame. The radius of the curve in the main tube as it goes from the top tube to the gusset plates on the works frame is smaller than on a Manx Featherbed.

Modifications to the rear mudguard loop carried out at the 1954 TT

500 stamped on drive-side gusset

It can be seen that the rear mudguard loop has been chopped off the frame pictured here. This was done in a hurry at the TT in 1954. An extra bracing tube was added between the top tubes at the same time. This frame is for a 500cc Works machine, as indicated by the stamping to the gusset on the drive side.

Pannier tank mounts and bowed drive side main tube can be seen

The drive side bottom tube is bowed out on the Works frame in order to clear the outside flywheel that was used on the 1954 machines. The timing side gusset and bottom tube are also relieved slightly in order to allow the fitment of a 5 speed Burman gearbox.

Oil cooler mount

The frame incorporates many Works specific features. On the top tubes there are mountings which hold the pannier tanks on either side of the machine. The timing side front down tube has a bracket added which supports the oil cooler which was used on the Works machines.



Front fairing mount



Weight saving inside the steering head

Front fairing mountings are also different from that of a standard Manx. The 1954 Works bikes sometimes utilised the rather unusual looking Proboscis fairing. The steering head on the Works frame is also undercut inside in order to save weight.



Rear chain oiler



The Works frame is made so that it holds lubrication oil for both the primary and final drive chain. The 1954 Works machine used a floating rear brake, with the brake-plate being unusually on the timing side of the machine. In order to facilitate this, the frame had to have a mounting for the brake torque arm on the timing side.

Rear brake mounting and modifications to clear the Burman 5 speed gearbox

As well as incorporating all the special Works extras not seen on a conventional Manx, the frame is of course much lighter than that on the production racing machine.

Ted Mellors Rotary Valve New Imperial

Ted Mellors was born In Chesterfield in 1907 and went on to become an extremely successful motorcycle racer – becoming 350cc European Champion in 1938.

This quick post concentrates on an unusual engine that was developed by Mellors in the early 1940’s. The base for the engine is a New Imperial single cylinder, but Mellors manufactured and patented his own rotary valve system for it. There was much interest in rotary valves engines prior to WW2, due to the potential benefits of higher compression ratios and mechanical simplicity over conventional poppet valve systems. Frank Aspin was probably the most well known exponent of rotary valves in the motorcycle field during the 1930’s.  

The Mellors rotary valve system utilised two conical rotary valves in the cylinder head; one for intake and one for exhaust. Unusually these rotary valves did not move continuously in sync with the crank, but instead moved in 90° steps. In order to achieve this more complex valve movement, a Maltese Cross mechanism was used. When the valves were in their stationary position a helical spring pressed them onto their housing so they were cooled. Just before the 90° movement of each valve, a face cam lifted each valve of its seat by a few thou. This allowed the valve to be rotated freely without excessive lubrication. The Maltese-Crosses themselves were driven by pins on the ‘cam’.

The Maltese-Cross system of valve operation would have been subjective to very high accelerations. Reliability at high speed and mechanical noise would surely have been major issues.

150cc Bruce Special New Imperial

The Bruce special was built by Charlie and his brother John of Motherwell. It was based around a 150cc New Imperial unit engine, to be eligible for the Scottish 150cc racing class. The full duplex swinging arm frame was a one-off built by Charlie Bruce with help from Joe Potts. Due to the lack of proprietary motorcycle rear suspension units, Charlie converted bomb door jacks that Joe had been manufactured in his engineering firm as part of the war effort and were also used on his 250cc  Velocette MAF.

The ‘Bruce Special’ was raced by John Bruce at various Scottish circuits during the early 1950’s, including Beveridge Park and Crail, as well as sand racing events. In 1952 the ‘Bruce Special’ carried the number 1 plate at the Beveridge Park road races. As the 150cc class was dropped in favour of a new 200cc Scottish class, the bike was converted to a 125cc and run in that event.

The ‘Bruce Special’ was sold by Charlie Bruce to William McBirnie, one of his friends in the Avon Valley motorcycle club. The bike was road registered in 1952, but William continued to enter races at Errol. The bike was then sold to another Avon Valley member, John Miller who used it on the road until 1958, the last time that it ran. In recent years this bike was located and purchased by Ian Whitehead & George Corner.

AJS Porcupine losing its spikes.

The 1951 AJS Porcupine.

During the winter of 1950, the AJS factory at Plumstead had been busy developing their 500cc Porcupine machine for the 1951 season.

The aim of the modifications was to produce “increased power, greater engine flexibility and an overall reduction in weight”.

The Porcupine without the spikes on the cylinder head.

Going to the engine, the most notable change to the Porcupine for 1951 is the losing of its spikes. For ease of development reasons, separate cylinder heads with horizontal transverse fins replaced the former cooling spines. This enabled detachable cam boxes and spring chambers to be incorporated, whilst the 14mm spark plugs are centrally located. The only other change to the engine is the enclosing of the main oil pump into the bottom of the crankcase to which is bolted a long boat-shaped light alloy sump holding over a gallon of lubricant.



New central floatchamber supports dual mixing chambers fitted with horizontal jets



An important modification was the use of a central float chamber. This enabled the carburettors to be mounted lower, giving a better sweep to the intake port. It was hoped that this modification would overcome the misfiring and uncertain running at low engine speeds.

The wheelbase was shortened by 1” for 1951 and weight was also shaved from the frame. Extra weight savings were made due to the absence if an oil tank and associated pipe work. The front forks were also shortened by 1” and a new alloy top yoke and two-piece sheet steel bottom yoke were used. Smaller wheels were fitted - 19 by 3.00 ins at the front, and 19 by 3.25 ins at the rear. The 10” front brake which was first used at the 1950 Belgian GP was refined slightly, but used for 1951. The rear brake remained unaltered.

New F.I.M. regulations meant than a new triangulated support for the longer rear mudguard was necessary. The seat was shorter than the 1950 design, and a zipped pocket was incorporated into it in order to hold two spare spark plugs.

The 1951 AJS Porcupine

A Real Yorkshire Ferret.

The Jim Lee 350cc Yamaha:

Reynolds 531

I am looking forward to the arrival of my first Reynolds 531 framed bicycle any day now. It is with this in mind that encouraged me to write a little bit about this venerable steel tubing, which has been used on many fine racing motorcycles and cars.

The history of the Reynolds Tube Company dates back to 1841 when John Reynolds started a nail making business. In the late 19^th Century Reynolds was looking at expanding the business and went into the field of making lightweight tubing. In 1897 Alfred M. Reynolds and J.T. Hewitt, an employee of the company, took out a patent on their "butted" tubes. These tubes were developed. It was in 1923 that the company was renamed the Reynolds Tube Company.

It was in 1935 that Reynolds 531 was first introduced. 531 came about unintentionally. It was Chief Inspector and Metallurgist Max Bigford who spotted an aircraft tubing which he thought held the potential for making an excellent cycle tubeset and reworked the specifications along with Director Austyn Reynolds. The approximate alloying composition of 531 tubing is 1.5% Mn, 0.25% Mo, 0.35% C, and is similar to the old British BS970 En 16/18 steel. It has a UTS of 700-900 MPa.

During WW2 Reynolds made over 10,000 miles of steel tubing for the war effort. 531 steel was utilised (amongst other things) on the frames that held Rolls Royce Merlin engines. After the war, 531 continued to be used in bicycle frames and also in motorcycle racing frames. The Manx Norton Featherbed frame is probably the most famous frame to be made of Reynolds 531. 531 was also used on cars, for example sub-frames on the Jaguar E type were made using it.

Reynolds 531 was so successful that it was not until 1976 that Reynolds was able to improve on it as a material for bicycle frames, with the introduction of Reynolds 753. Such was the success of Reynolds tubing in bicycle manufacturing, 27 winners of the Tour de France have won riding with Reynolds tubing.

Alan Coultas 4 Valve Velocette

This was a significant machine owned and developed by Alan Coultas of Hull, and with which he achieved considerable success at National level over many years. Alan was one of the “Yokshire Velocette Mafia”, who truly built this machine in the back of a garage at his house. He was also handicapped by the fact that he did not ride himself and relied on feedback from a string of riders of differing abilities.

Alan Coultas mark 1 Velocette 4 Valve cylinder head

The first version 4 valve Velocette engine made by Alan was fabricated from a stock venom head and used a clever ‘hinge’ arrangement to operate the pairs of valves via the standard rockers and cover. The second version was altogether more sophisticated and used a purpose made casting, the patterns being produced and pouring taking place once again in Alan’s garage. The design incorporated many clever features such as a cast-in skull and separate exhaust port for each valve. It proved reliable and immediately gave a useful increase in power throughout the rev range.

The Alan Coultas mark 2 4 valve Velocette cylinder head

Its Achilles’ heel however was the rockers and after several unsuccessful attempts to cure the problem, the project was sadly mothballed in favour of a much modified 2 valve Velocette part. This engine he further developed over time and in its final form used a fully squished twin plug head with piston to suit. It was a very fast machine indeed and in the capable hands of Tony Myers, almost lapped the entire field at Cadwell Park to win the E.A.Lavington Trophy. He was not invited back!

The Alan Coultas 4 Valve Velocette

Bianchi team and the Bellshill brigade at the 1961 TT

Both Bob McIntyre and Alastair King were entered for the Junior TT on works 350cc Bianchi twin cylinder machines. Bianchi were to send over three bikes for Bob and two for Alastair which they could pick their preferred bike for the race. The Bianchi’s were late arriving, which meant that several practice sessions were missed. I will reproduce a great anecdote relating to an incident between Bob Mac and the Bianchi team during practice that was given to me by Archie Plenderleith who was at the TT in 1961 and who spent a lot of time with the Potts team:

      

There was another misunderstanding involving Bob Mac and the Italian Bianchi mechanics one morning during TT practice. Bob Mac had got himself stranded out on the circuit one evening during practice when the Bianchi stopped. His Italian mechanic went to rescue him in Bob Mac’s van. They arrived back at the Bianchi garage quite late and proceeded to investigate the Bianchi and ready another for the next morning practice. By the time they were finished all the petrol stations were shut and Bob Mac’s van was extremely low on petrol. Bob Mac asked the Italian mechanic if there was any petrol and he pointed to some jerrycans. Bob Mac threw one in the back of his van and set off for his digs on the Loch Promenade. Next morning Bob Mac filled up the van from the jerrycan and set off for the Grandstand with Pim Fleming. I left for the Grandstand some time after them (our digs were only 50 yards apart) and I found their van outside the Villa Marina with all the doors wide open and the engine cowling lying in the roadway along with a toolbox. Pim saw me coming and waved me down. “Could you give us a tow, the van stopped halfway up the hill and now it won’t start” – he said! Bob Mac was in about the engine! “Should go” he said, “it has got a spark and it has got petrol”. We collected all the tools and gave it a tow but it would not run properly, it was spluttering, misfiring and would not rev up and whenever the clutch was engaged it stopped. We towed it again – and again – and again!! No joy! We towed it back to his digs and left Pim to sort out the problem. I gave Bob Mac a lift to the Grandstand where the Bianchi Boss man was waiting!! He didn’t look too pleased.

Chapter 1

Boss Man (annoyed) – “Ahh ha! Meester Bob, where you been, we here at 5 o’clock waiting you, but now you come at 6.15 and the Bianchi she is back in the garage so you no go out! What is the matter, you like a big sore head, you been to a party huh?

Bob Mac (now very deliberate) – “I DON’T HAVE A SORE HEAD         and I HAVE NOT BEEN TO ANY PARTY but I wish I had! I DID NOT MEAN TO BE LATE, my van stopped on the way here and there is no need for argument!”

It was obvious that he was not in a good mood!

Boss Man (very sarcastic) – “Ooohhh, I be sorry to hear that, very sorry, then the van must have been to the party huh?”

Bob Mac (getting madder by the minute) – “THERE HASN’T BEEN ANY BLOUDY PARTY but there soon will be to your acute embarrassment”

Boss Man and the Italian Mechanic confab in Italian!

Boss Man – “I be really sorry for you Meester Bob, very sorry, true, Ruffo here (Italian Mechanic) vill soon feex your van.”

Bob Mac (becoming suspicious) – “WHY HIM? What does he know about my van?”

Boss Man (more friendly) – “Ruffo, good man to feex your van, he knows moteyrs. And, he wants his VINO back. You took his VINO last night, see!”

The penny drops all round! The jerrycan contained VINO. Van problem solved.

Boss Man – “Beeg mistake, very beeg mistake Meester Bob, very sorry, very sorry, verry sorry your van does not like the VINO. But funny ha ha, verrry funy, ha ha ha, yes?”

Bob Mac (still mad, does not think funny) – “If you lot went on fire I would dial 998. Silly buggers! Come on, let’s go back to Pim”

Pim Fleming in front of Alastair King's van

Chapter 2

I drove Bob Mac back to his van where we met up with a very irate Pim. When Pim was “up tight” he spoke very loudly in the true Scots Vernacular and that morning was no exception.

Bob Mac – “I know what is wrong with the van!”

Pim – “Ye dinny need tae tell mi, ah ken whits wrang wi it, its foo o bloody water an sose that @=&+%*£+$ jerrycan ye goat frae thae Eyetye mikaniks! Nae wunder yer beeanchy disny go, its gie likely foo o water an aw!”

A translation of Pim’s reaction – “You don’t need to tell me, I know what is wrong with it, it’s full of water and so is the jerrycan you got from these stupid Italian mechanics. No wonder your Bianchi does not go, very likely it is full of water too!”

A flattrack Velocette engine by Ernie Pico

I thought the newest post should be about an unusual Velocette engine. The engine started off as a 500cc Velocette MSS scrambler engine which was sent to America. The engine is a special which has been modified by Ernie Pico.

Ernie Pico was a big feature in the Los Angeles motorcycle scene for 50 years. After returning from Europe after WW2 he started a motorcycle shop called Big City Sales. Ernie was very successful for many years and during those years his passion was racing bikes. Mainly Flattrack and Speedway but also Daytona, on the real beach, and the Catalina GP( an island off off LA ). He built the bikes and had all kinds of Throttle Jockeys riding his bikes. Ascot Park, a dirt 1/2 mile oblong was the pinnacle of Motorbike racing in the 60's and Ernie was a contender with his machines and riders. He favoured Norton twins first and then got into Velos. Velos always had a good following in Southern California and he got bitten by the Velo Bug, big time. After many years of experimenting he had the fastest Velo ever. Every one of them had 100s of hours in them, and were an evolution of the prior one.

Ernie's Velos where very completive with the Triumphs , BSAs and Nortons and he got a huge kick out of bothering and sometimes beating the factory Harley Davidsons in the late 60s. Ernie lived not too far from Ascot and would ride his main bike from Home to the track on race night (Friday) to make sure it was running perfect. He had some great Flattrack riders such as, Tex Luce, Don Hawley, Shorty Seabourne, Terry Donaher, Art Barda and Lynn Halloway. The Tracks where they ran were, Ascot dirt 1/2 mile, San Jose one mile dirt track, Sacramento one mile dirt track, Tulary 1/2 mile dirt (perfect circle), Portland Meadows one mile dirt.

Ascot Park in Gardena, a southern suburb of Los Angeles, was the epicentre of dirt track racing in America during this period. It was a one half mile oval of sticky clay that held races every Friday night during a three month period in the summer. There was a national championship that was held at tracks around the country but all the good riders and factory teams ran at Ascot for the prestige and big money. Ernie's Velos where definitely underdogs but held their own and on occasion beat the factory H.D.s ,Triumphs and BSAs.  Velos had very loyal followers here on the west coast but remained a weird contraption to the masses. Ernie had raced other bikes with success but he loved Velos and was bound and determined to compete and win with his underdog.

Terry Donaher on the Ernie Pico Velocette at Ascot Park

The photo above is of a 19 year old  Terry Donaher who at the races where this photo was taken, put the bike in the main and beat the Harley Davidson factory KRs. Ernie delighted in telling the story how the HD manager, O'Brian tried to get the Velo disqualified but to no avail.

The rules at one stage insisted on stock frames and engine combo but in 70 they changed and allowed custom frames (Trackmaster, Sonic ,Champion etc). Ernie swore by the low centre of gravity Velo hard tail frame and always preached about its advantages. At this time the rules changed engine sizes also to 750 OHV which made all the 500 Goldies and the Velo obsolete. Ernie put a Norton Atlas in a Velo frame and with rider Shorty Seabourne had a very competitive machine.

Ernie’s wife Wanda, had a big successful business making racing leathers. The AMA let it be known that they were going to ban Black leathers because of the negative stigma. Wanda immediately started in the coloured leathers business and dominated in that field. 

Well let’s go on to the technical details of this Ernie Pico Velocette engine. Starting with the flywheels, they have been reduced in diameter to allow the fitment of a very short BSA Goldstar connecting rod. The piston used is a special forged item. The crankcases have been built-up around the mouth, in order to allow the barrel skirt to fit into them lower. The barrel, pushrods and engine studs have also been shortened. All the blots and nuts within the engine are aircraft specification - friction grips and very interestingly the bolts that hold the rocker to the head (Velo's weak point) have been increased in diameter to 3/8ths high tensile.

Both main bearings are double row –parallel rollers not the STD tapers rollers. Double speed oil pump worm and beautifully lightened timing gears throughout and purpose machined thrust washers. Both top and bottom rockers have been extensively lightened, polished and then nickel plated to stop cracking.  

Going to the cylinder head, there are double coil springs/alloy retainers, with a 1.75" diameter exhaust port & steeply angled down-draft 1.5" diameter inlet port with a 2" inlet valve - don't forget this is a modified MSS scrambler head not later Thruxton type. The inlet valve used comes from a Lycoming aircraft engine. The engine has a much higher compression ratio and would have run on methanol.

Update. Please follow this link for a set of wonderful photos from the archive of Ernie Pico:

Ernie Pico photos

Potts Desmo as it is now