RETRO BIKE HAULER

Mike Kane (the cliff diver! See my earlier post), who is no stranger to building up iconoclastic retro motorcycles, turned his attention to building long-distance transport for his beloved Indians.
Here's his explanation:
"This truck is something that has been in my brain since I was a teenager. The chassis is a 1988 1 ton Chevy, 350ci, autobox, power steering, air conditioning, dually rear end. The cab is a 1948 Diamond T Peterbilt sleeper which has been chopped 3 1/2" and narrowed 6".

The bed and rear fenders are custom made; the bed is 6 ft wide on the inside and 8 1/2 ft long. I left the inside dual wheels off for bed space. I have Peterbilt air bags (air suspension) on the rear. When I dump the air, the bed drops to 22" off the ground. The tail gate is made from a moving van ramp and when removed it works as a ramp. I built this to take bikes to swap meets and shows. It is almost done, a few bugs to work out before the interior goes in. I'm glad its almost done, I haven't got much bike work done"
I can imagine - looks like a lot of work, but nobody will miss Mike when he shows up!

RETRO BIKE HAULER

Mike Kane (the cliff diver! See my earlier post), who is no stranger to building up iconoclastic retro motorcycles, turned his attention to building long-distance transport for his beloved Indians.
Here's his explanation:
"This truck is something that has been in my brain since I was a teenager. The chassis is a 1988 1 ton Chevy, 350ci, autobox, power steering, air conditioning, dually rear end. The cab is a 1948 Diamond T Peterbilt sleeper which has been chopped 3 1/2" and narrowed 6".

The bed and rear fenders are custom made; the bed is 6 ft wide on the inside and 8 1/2 ft long. I left the inside dual wheels off for bed space. I have Peterbilt air bags (air suspension) on the rear. When I dump the air, the bed drops to 22" off the ground. The tail gate is made from a moving van ramp and when removed it works as a ramp. I built this to take bikes to swap meets and shows. It is almost done, a few bugs to work out before the interior goes in. I'm glad its almost done, I haven't got much bike work done"
I can imagine - looks like a lot of work, but nobody will miss Mike when he shows up!

'BEADED EDGE' TIRES AND SAFETY

The word 'tire', or 'tyre' to the English-speakers, originated with the steel bands holding wooden wagon wheels together, which were forged by wheelwrights. These bands not only made for a hard-wearing surface for the wheel perimeter, but served to 'tie' the wheel and spokes together - they were literally the 'tie-r' of the wheel. The English like to think they spell things correctly but in fact the spelling 'tire' is older than 'tyre', which appeared in the 15th century. Subsequently, the word 'tire' became generic for any wearing surface on a wheel, whether a cart, bicycle, car, or a steam train, and whether the material was steel, rubber, or wooden balls bound by wire (a few of the more desperate examples can be seen in the photo below, from Munich's Technische Museum).

I'll skip ahead a few centuries to the birth of our subject, the Pneumatic tire, which supplanted the solid rubber item popular on early bicycles, cars, and motorcycles. The 'aha' moment came for John Boyd Dunlop (below) in 1887, while watching his son bump uncomfortably along a cobbled street on his tricycle.

Dunlop laid thin sheets of rubber, glued together, over the solid tires on the trike, adding an inflator valve from a football, and voila, the pneumatic tire was born. He patented the idea in 1888, and by 1889 had opened tire manufacturing plants in Dublin and Birmingham - clearly not a man to dawdle over a good idea! Another type of pneumatic tire was invented in 1845 by Robert William Thompson, but his system was too expensive for commercial production, and Dunlop gets the credit for the first practical pneumatic tire, and the first to be commercially produced. Mind you, his patent was for bicycle tires, which of course dovetails very nicely into our subject; motorcycle history (see the wonderful photo of J.B.D. enjoying the fruits of his labor, below).

Motorcycle tires of the Dunlop pattern used a very simple system to ensure positive location on the steel wheel rims of the day. High air pressure, at 40-60lbs/square inch, kept the rubber sidewalls firm against the wheel flange, which was a curved lip 0f folded steel, mated to a corresponding rubber 'bead' cast into the tire base itself (see illustration).

This method of attachment works quite well to keep the the wheel stable, at the expense of a rock-hard ride from the highly inflated tire. It has always been, since the earliest days of tire on rim, a temptation to lower the pressure within such tires, to increase the 'give' of the rubber and provide some form of cushioning against road shocks. This is fully understandable given the terrible road surfaces of the day - packed dirt or gravel were about the best one could hope for in the years 1890-1928, as the Macadam system of asphaltum-glued gravel laid in smooth beds and compressed flat were quite rare except in urban areas, which had the tax base capable of the high expenditure necessary for such infrastructure investment.

The terrific downside of under-inflation with these 'clincher' or 'beaded-edge' type tires is the possibility of rapid deflation as a consequence of a sharp blow. Of course, a 'blowout' or quick loss of air from a puncture or tear is a possibility on any inflated tire, but this early method of fastening tire to rim has the distinct charm of immediately tearing the tire from the rim if pressure is lost, as only air pressure holds the two firmly together. The consequence, Every Single Time, is a spill, as the tire magically transforms into a rubber snake hell-bent on tying itself in knots between the wheel proper and any frame or fork tubes nearby, thus locking up the wheel, which has already become an ultra-low-friction steel ski on the road surface.

Tire manufacturers developed a new type of wheel rim/tire combination around 1924 which became the standard for all automobile and motorcycle tires from then until the present day. The new system, called 'well-rim' or 'wired-edge' wheels, uses a much stiffer tire which, although far more difficult to install, does not rely on air pressure to maintain its place on the wheel rim. Thus, if deflation occurs, the tire simply goes 'flat', but stays on the rim, and the wheels continue to rotate on rubber, albeit in a wobbly/frightening manner. Still, this was a tremendous improvement in safety, and the number of crashes from deflation plummeted. Tires were made gradually thicker, heavier, and more substantial over the ensuing decades, and additions of nylon, then steel cording under the tread, and ultimately fully 'radial' tires (invented in 1946, by Michelin) for cars and, later, motorcycles were developed. New motorcycle tires are 'tubeless', yet rely on those basic principles developed in the 1920's to stay on the rim.

Falling off a motorcycle at speed really hurts, at best. I've been thrown from my motorcycle at 50 mph from a mechanical front wheel lockup, and suffered the effects for quite a while from the resultant 'high-side'; it was motorcycle jiu-jitsu, and I lost. I bring all this up after my friend James experienced a blow-out on his '24 Sunbeam, which used 'clinchers', as does my '25 Sunbeam. As fans of 'period correctness', we were quite happy that our machines retained their original equipment, and had no intention of changing over to more 'modern' well-type rims and tires, as the vast majority of 1920's machines have done. We had recently discussed proper inflation with our 'clinchers', and James stated that he was using 25lbs/sq" pressure front and rear on his Sunbeam, as the ride was almost unbearable at the 40lbs recommended pressure for the Dunlop 'Cord' tires he had installed, at great expense (they cost ~$300 each).
After James' fatal accident, a query from a distant acquantance led to a bit of mutual research into 'clincher' tire safety.

The result of this research was very sobering, and I'm posting it here in the fervent hope of obviating any additional risk when using these 80-years-obsolete tires. Using them at all is a risk per se, with their known defect of sudden detachment from the rim after deflation. But, with proper care, a greater measure of safety is possible.

According to Radco's book 'The Vintage Motorcyclists' Workshop' (Haynes, 1986), a 2.5" wide clincher tire of 24" diameter (the size of my and James' Sunbeam) at 24lbs inflation, has a load capacity per tire of 150lbs. Assuming a 250lb motorcycle, plus 175lb rider, give or take, that's 425lbs, or 212.5lbs load per tire. Thus, at 24lbs/sq" pressure, the tires are 62.5lbs OVERLOADED, just standing still.

Radco further states (see chart, above) that inflation of 36lbs equals a 320lb permissible load per tire, which gives over 100lbs of 'leeway' on the tire loading; ie, less likelihood that the tire will blow out under rapid compression, as from a large rock or sharp crease in the road. A little further investigation; in 'Dyke's Automobile and Gasoline Engine Encyclopedia' of 1927, a 'high pressure pneumatic tire' (ie clincher) should be inflated to 45lbs or more. Further still; a Society of Automotive Engineers (S.A.E.) chart of the same era lists 3" Cord-type tires (exactly the size and type of my Sunbeam) as requiring a minimum of 40lbs pressure. Vintage Tyre Supply is a primary source of the Dunlop Cord clinchers available today, as used on my Sunbeam (and James' too), but they don't list any tire pressure recommdations for these tires on their website, only for their automotive and 'well-rim' motorcycle tires. Another source of modern 'clinchers', Universal Tyre Co. lists pressures for all their tires on their website, and they recommend 60-65lbs pressure for such motorcycle tires. Longstone Classic Tires recommends a minimum of 60lbs pressure for their tires as well. This should be food for thought for anyone riding on clinchers, as I do. It is imperative that they are properly inflated, to at least 35-40lbs/sq". Under-inflation is dangerous, and could prove fatal; as risk-takers, we owe it to ourselves to be safe when it's within our power.

If you have a perverse interest in tire history, you can download a copy of the B.F Goodrich book from 1918, 'Best in the Long Run', which was used to train their sales representatives. It give a comprehensive history of tires from the earliest days through 1918. Googlebooks has made it possible to read/download the book, for free, here.

'BEADED EDGE' TIRES AND SAFETY

The word 'tire', or 'tyre' to the English-speakers, originated with the steel bands holding wooden wagon wheels together, which were forged by wheelwrights. These bands not only made for a hard-wearing surface for the wheel perimeter, but served to 'tie' the wheel and spokes together - they were literally the 'tie-r' of the wheel. The English like to think they spell things correctly but in fact the spelling 'tire' is older than 'tyre', which appeared in the 15th century. Subsequently, the word 'tire' became generic for any wearing surface on a wheel, whether a cart, bicycle, car, or a steam train, and whether the material was steel, rubber, or wooden balls bound by wire (a few of the more desperate examples can be seen in the photo below, from Munich's Technische Museum).

I'll skip ahead a few centuries to the birth of our subject, the Pneumatic tire, which supplanted the solid rubber item popular on early bicycles, cars, and motorcycles. The 'aha' moment came for John Boyd Dunlop (below) in 1887, while watching his son bump uncomfortably along a cobbled street on his tricycle.

Dunlop laid thin sheets of rubber, glued together, over the solid tires on the trike, adding an inflator valve from a football, and voila, the pneumatic tire was born. He patented the idea in 1888, and by 1889 had opened tire manufacturing plants in Dublin and Birmingham - clearly not a man to dawdle over a good idea! Another type of pneumatic tire was invented in 1845 by Robert William Thompson, but his system was too expensive for commercial production, and Dunlop gets the credit for the first practical pneumatic tire, and the first to be commercially produced. Mind you, his patent was for bicycle tires, which of course dovetails very nicely into our subject; motorcycle history (see the wonderful photo of J.B.D. enjoying the fruits of his labor, below).

Motorcycle tires of the Dunlop pattern used a very simple system to ensure positive location on the steel wheel rims of the day. High air pressure, at 40-60lbs/square inch, kept the rubber sidewalls firm against the wheel flange, which was a curved lip 0f folded steel, mated to a corresponding rubber 'bead' cast into the tire base itself (see illustration).

This method of attachment works quite well to keep the the wheel stable, at the expense of a rock-hard ride from the highly inflated tire. It has always been, since the earliest days of tire on rim, a temptation to lower the pressure within such tires, to increase the 'give' of the rubber and provide some form of cushioning against road shocks. This is fully understandable given the terrible road surfaces of the day - packed dirt or gravel were about the best one could hope for in the years 1890-1928, as the Macadam system of asphaltum-glued gravel laid in smooth beds and compressed flat were quite rare except in urban areas, which had the tax base capable of the high expenditure necessary for such infrastructure investment.

The terrific downside of under-inflation with these 'clincher' or 'beaded-edge' type tires is the possibility of rapid deflation as a consequence of a sharp blow. Of course, a 'blowout' or quick loss of air from a puncture or tear is a possibility on any inflated tire, but this early method of fastening tire to rim has the distinct charm of immediately tearing the tire from the rim if pressure is lost, as only air pressure holds the two firmly together. The consequence, Every Single Time, is a spill, as the tire magically transforms into a rubber snake hell-bent on tying itself in knots between the wheel proper and any frame or fork tubes nearby, thus locking up the wheel, which has already become an ultra-low-friction steel ski on the road surface.

Tire manufacturers developed a new type of wheel rim/tire combination around 1924 which became the standard for all automobile and motorcycle tires from then until the present day. The new system, called 'well-rim' or 'wired-edge' wheels, uses a much stiffer tire which, although far more difficult to install, does not rely on air pressure to maintain its place on the wheel rim. Thus, if deflation occurs, the tire simply goes 'flat', but stays on the rim, and the wheels continue to rotate on rubber, albeit in a wobbly/frightening manner. Still, this was a tremendous improvement in safety, and the number of crashes from deflation plummeted. Tires were made gradually thicker, heavier, and more substantial over the ensuing decades, and additions of nylon, then steel cording under the tread, and ultimately fully 'radial' tires (invented in 1946, by Michelin) for cars and, later, motorcycles were developed. New motorcycle tires are 'tubeless', yet rely on those basic principles developed in the 1920's to stay on the rim.

Falling off a motorcycle at speed really hurts, at best. I've been thrown from my motorcycle at 50 mph from a mechanical front wheel lockup, and suffered the effects for quite a while from the resultant 'high-side'; it was motorcycle jiu-jitsu, and I lost. I bring all this up after my friend James experienced a blow-out on his '24 Sunbeam, which used 'clinchers', as does my '25 Sunbeam. As fans of 'period correctness', we were quite happy that our machines retained their original equipment, and had no intention of changing over to more 'modern' well-type rims and tires, as the vast majority of 1920's machines have done. We had recently discussed proper inflation with our 'clinchers', and James stated that he was using 25lbs/sq" pressure front and rear on his Sunbeam, as the ride was almost unbearable at the 40lbs recommended pressure for the Dunlop 'Cord' tires he had installed, at great expense (they cost ~$300 each).
After James' fatal accident, a query from a distant acquantance led to a bit of mutual research into 'clincher' tire safety.

The result of this research was very sobering, and I'm posting it here in the fervent hope of obviating any additional risk when using these 80-years-obsolete tires. Using them at all is a risk per se, with their known defect of sudden detachment from the rim after deflation. But, with proper care, a greater measure of safety is possible.

According to Radco's book 'The Vintage Motorcyclists' Workshop' (Haynes, 1986), a 2.5" wide clincher tire of 24" diameter (the size of my and James' Sunbeam) at 24lbs inflation, has a load capacity per tire of 150lbs. Assuming a 250lb motorcycle, plus 175lb rider, give or take, that's 425lbs, or 212.5lbs load per tire. Thus, at 24lbs/sq" pressure, the tires are 62.5lbs OVERLOADED, just standing still.

Radco further states (see chart, above) that inflation of 36lbs equals a 320lb permissible load per tire, which gives over 100lbs of 'leeway' on the tire loading; ie, less likelihood that the tire will blow out under rapid compression, as from a large rock or sharp crease in the road. A little further investigation; in 'Dyke's Automobile and Gasoline Engine Encyclopedia' of 1927, a 'high pressure pneumatic tire' (ie clincher) should be inflated to 45lbs or more. Further still; a Society of Automotive Engineers (S.A.E.) chart of the same era lists 3" Cord-type tires (exactly the size and type of my Sunbeam) as requiring a minimum of 40lbs pressure. Vintage Tyre Supply is a primary source of the Dunlop Cord clinchers available today, as used on my Sunbeam (and James' too), but they don't list any tire pressure recommdations for these tires on their website, only for their automotive and 'well-rim' motorcycle tires. Another source of modern 'clinchers', Universal Tyre Co. lists pressures for all their tires on their website, and they recommend 60-65lbs pressure for such motorcycle tires. Longstone Classic Tires recommends a minimum of 60lbs pressure for their tires as well. This should be food for thought for anyone riding on clinchers, as I do. It is imperative that they are properly inflated, to at least 35-40lbs/sq". Under-inflation is dangerous, and could prove fatal; as risk-takers, we owe it to ourselves to be safe when it's within our power.

If you have a perverse interest in tire history, you can download a copy of the B.F Goodrich book from 1918, 'Best in the Long Run', which was used to train their sales representatives. It give a comprehensive history of tires from the earliest days through 1918. Googlebooks has made it possible to read/download the book, for free, here.

HISTORY OF ALLOY RIMS - THE BEGINNING

In the US, we're 'Geeks', in the UK, we're 'Anoraks', but people who have a keen interest in minutiae can really bolster research when details are needed. Dennis Quinlan and I have had a running discussion over the last 15 years about the origins of alloy wheel rims on racing motorcycles. We had both seen a variety of very old racing wheels, on machines and off, and had come to the conclusion that Borrani were the first producers of flanged aluminum rims. The question became, 'when'?

As we're English speakers with a common interest in Velocettes, we had noted that in the '36 Isle of Man TT, both Norton and Velocette Works racers had used black-painted Borrani alloy rims; presumably the black paint was meant to 'hide' the rims from the competition; but of course the competition had them as well! There have been many stories of riders 'smuggling' Borrani rims into England in 1935, trying to avoid import duty on these expensive new items; one such story has Stanley Woods arguing with a customs officer in England, claiming that he shouldn't be charged duty as the new development of wheel technology was in the 'national interest'. He won the argument.

These rims lowered the overall weight of the whole machine, and helped with the road-holding of sprung front and (by '36) rear wheels, reducing the bouncing mass which the springs and friction shock absorbers had to cope with. Lighter weight allowed the forks to respond more quickly and accurately to road surface changes, keeping the wheels in contact with the road longer over bumps, which means more traction, and the ability to use more power without fear of a skid.

On April 22, 1922, Carlo Borrani took out a license from the Rudge Whitworth Company of Coventry, England, to manufacture car, motorcycle, and bicycle wheel components (yes, the same Rudge which built motorcycles). Thus, 'Rudge Whitworth Milano' was established, with capital of 1.2m lire, and the factory was located at Via Ugo Bassi 9.

Rudge, with their 'Red Hand of Ulster' logo (see right), had patented a new method of mounting wheels, using a splined hub and one central locking nut. This system enabled much faster wheel removal, arousing interest from racing car constructors. Just 12 months after Sr. Borrani opened shop, Alfa Romeo, Auto Union, Bianchi, and Lancia began to equip their racing and deluxe sports toureres with Borrani wheels. Later in the 1930's, the company changed its name to 'Carlo Borrani SpA' (still in business!), and Carlo started to experiment with light, rigid aluminum rims as a replacement for heavier steel items.

These first rims were butt-welded together, with a small plate welded on the rim flange to strengthen the joint. As aluminum welding was still quite an art and certainly an exception, these plates were used for extra security; wheel rims collapsing in a race would certainly be bad for business! The photo above shows the plate clearly in the upper left corner; the bike is Stanley Woods' 1938 Junior TT-winning Works Velocette.

Borrani used a variety of identification stamps on their rims over the years, and it's interesting to note how the changes from the 30's thru 70's; someday a true Anorak will document the evolution of these stamps, and we'll all sleep more easily. The photograph above is from a rim ca. 1936 - Borrani used Italian language stamps until the 1960's. Some claim the earliest rims had the 'red hand' stamp, but I've yet to see one.

It would appear from photographic evidence that the first use of these Borrani rims on a racing motorcycle was in late 1934, and Moto Guzzi was the most enthusiastic early adopter, with Gilera following suit shortly afterwards. The photo below shows legendary racer Omobono Tenni riding the Guzzi ohc v-twin 'Bicylindrica' at the Circuito di Treviso, in late 1934.

By 1935, nearly all the Italian Works racers used alloy rims, and a few English machines (Norton mostly, plus at least one Rudge) sported them as well. The photo below shows a Moto Guzzi Bicylindrica which has been equipped for road use - complete with horn, muffler, speedometer, and license plate - for the Milano-Napoli long-distance road race. Talk about a roadburner!



Another 1935 shot; this time the motorcycle is the Gilera 'Rondine' 4 cylinder dohc water-cooled racer, in March 1935, at the Tripoli GP. Pierro Taruffi rode this machine to victory, using what I believe is among the very first 'dolphin' fairings, of hand-beaten aluminum alloy. His mechanic Orlando Ciceroni sits on the bike, wearing the ubiquitous beret and coveralls of Italian motorcycle mechanics.


In June 1935, the first Borrani rims appear at the Isle of Man; below is Jimmie Guthrie on his Works Norton in the Senior TT, with black-painted alloy rims (and a fully enclosed rocker box - something which didn't 'stick'). Alloy rims also appeared on the Rudge - naturally - of Tyrell-Smith. How Norton came to trump the competition in this regard needs some investigation, as Velocette didn't use them at the TT until the following year.


By 1936 alloy rims can be seen on most of the victorious Works racers from Norton and Velocette (as above on Stanley Woods' 495cc ohc Works Velocette), although they seldom appear on privateer machines until 1938/9. Interestingly, the Italians didn't seem keen to share this racing advantage with German factories, and apparently the Germans developed their own, non-flanged aluminum rims which were rivetted together. I'll post more information about these early German rims as I find photographs and documentation.

The truth is, BMW didn't need the weight savings, as their supercharged ohc Works racers were a good 50lbs lighter than the nearest Norton or Velocette! By contrast, the NSU dohc blown racers could have used any lightening they could find, as their all up weight was over 450lbs - almost 100lbs more than the nearest Norton. DKW 'lightweights' were a misnomer as well, being considerably heavier than their 250cc competition, but they produced (like their BMW/NSU brethren) so much more horsepower than their English rivals, that perhaps the designers felt the weight was a non-issue, which proved true only on the fastest and least 'bendy' circuits.

Many thanks to Dennis Quinlan for his information! Also, images are taken from Mario Colombo's excellent Gilera Quattro and Moto Guzzi books, and Mick Woolett's Norton.

HISTORY OF ALLOY RIMS - THE BEGINNING

In the US, we're 'Geeks', in the UK, we're 'Anoraks', but people who have a keen interest in minutiae can really bolster research when details are needed. Dennis Quinlan and I have had a running discussion over the last 15 years about the origins of alloy wheel rims on racing motorcycles. We had both seen a variety of very old racing wheels, on machines and off, and had come to the conclusion that Borrani were the first producers of flanged aluminum rims. The question became, 'when'?

As we're English speakers with a common interest in Velocettes, we had noted that in the '36 Isle of Man TT, both Norton and Velocette Works racers had used black-painted Borrani alloy rims; presumably the black paint was meant to 'hide' the rims from the competition; but of course the competition had them as well! There have been many stories of riders 'smuggling' Borrani rims into England in 1935, trying to avoid import duty on these expensive new items; one such story has Stanley Woods arguing with a customs officer in England, claiming that he shouldn't be charged duty as the new development of wheel technology was in the 'national interest'. He won the argument.

These rims lowered the overall weight of the whole machine, and helped with the road-holding of sprung front and (by '36) rear wheels, reducing the bouncing mass which the springs and friction shock absorbers had to cope with. Lighter weight allowed the forks to respond more quickly and accurately to road surface changes, keeping the wheels in contact with the road longer over bumps, which means more traction, and the ability to use more power without fear of a skid.

On April 22, 1922, Carlo Borrani took out a license from the Rudge Whitworth Company of Coventry, England, to manufacture car, motorcycle, and bicycle wheel components (yes, the same Rudge which built motorcycles). Thus, 'Rudge Whitworth Milano' was established, with capital of 1.2m lire, and the factory was located at Via Ugo Bassi 9.

Rudge, with their 'Red Hand of Ulster' logo (see right), had patented a new method of mounting wheels, using a splined hub and one central locking nut. This system enabled much faster wheel removal, arousing interest from racing car constructors. Just 12 months after Sr. Borrani opened shop, Alfa Romeo, Auto Union, Bianchi, and Lancia began to equip their racing and deluxe sports toureres with Borrani wheels. Later in the 1930's, the company changed its name to 'Carlo Borrani SpA' (still in business!), and Carlo started to experiment with light, rigid aluminum rims as a replacement for heavier steel items.

These first rims were butt-welded together, with a small plate welded on the rim flange to strengthen the joint. As aluminum welding was still quite an art and certainly an exception, these plates were used for extra security; wheel rims collapsing in a race would certainly be bad for business! The photo above shows the plate clearly in the upper left corner; the bike is Stanley Woods' 1938 Junior TT-winning Works Velocette.

Borrani used a variety of identification stamps on their rims over the years, and it's interesting to note how the changes from the 30's thru 70's; someday a true Anorak will document the evolution of these stamps, and we'll all sleep more easily. The photograph above is from a rim ca. 1936 - Borrani used Italian language stamps until the 1960's. Some claim the earliest rims had the 'red hand' stamp, but I've yet to see one.

It would appear from photographic evidence that the first use of these Borrani rims on a racing motorcycle was in late 1934, and Moto Guzzi was the most enthusiastic early adopter, with Gilera following suit shortly afterwards. The photo below shows legendary racer Omobono Tenni riding the Guzzi ohc v-twin 'Bicylindrica' at the Circuito di Treviso, in late 1934.

By 1935, nearly all the Italian Works racers used alloy rims, and a few English machines (Norton mostly, plus at least one Rudge) sported them as well. The photo below shows a Moto Guzzi Bicylindrica which has been equipped for road use - complete with horn, muffler, speedometer, and license plate - for the Milano-Napoli long-distance road race. Talk about a roadburner!



Another 1935 shot; this time the motorcycle is the Gilera 'Rondine' 4 cylinder dohc water-cooled racer, in March 1935, at the Tripoli GP. Pierro Taruffi rode this machine to victory, using what I believe is among the very first 'dolphin' fairings, of hand-beaten aluminum alloy. His mechanic Orlando Ciceroni sits on the bike, wearing the ubiquitous beret and coveralls of Italian motorcycle mechanics.


In June 1935, the first Borrani rims appear at the Isle of Man; below is Jimmie Guthrie on his Works Norton in the Senior TT, with black-painted alloy rims (and a fully enclosed rocker box - something which didn't 'stick'). Alloy rims also appeared on the Rudge - naturally - of Tyrell-Smith. How Norton came to trump the competition in this regard needs some investigation, as Velocette didn't use them at the TT until the following year.


By 1936 alloy rims can be seen on most of the victorious Works racers from Norton and Velocette (as above on Stanley Woods' 495cc ohc Works Velocette), although they seldom appear on privateer machines until 1938/9. Interestingly, the Italians didn't seem keen to share this racing advantage with German factories, and apparently the Germans developed their own, non-flanged aluminum rims which were rivetted together. I'll post more information about these early German rims as I find photographs and documentation.

The truth is, BMW didn't need the weight savings, as their supercharged ohc Works racers were a good 50lbs lighter than the nearest Norton or Velocette! By contrast, the NSU dohc blown racers could have used any lightening they could find, as their all up weight was over 450lbs - almost 100lbs more than the nearest Norton. DKW 'lightweights' were a misnomer as well, being considerably heavier than their 250cc competition, but they produced (like their BMW/NSU brethren) so much more horsepower than their English rivals, that perhaps the designers felt the weight was a non-issue, which proved true only on the fastest and least 'bendy' circuits.

Many thanks to Dennis Quinlan for his information! Also, images are taken from Mario Colombo's excellent Gilera Quattro and Moto Guzzi books, and Mick Woolett's Norton.

BINKS 'RAT-TRAP' CARBURETOR

Here's an interesting response to the O'Donovan post; 'Old Miracle' used a Binks 'Rat Trap' carburetor, which is strictly a flat-out track carb, with no idle circuit and no slow-speed cutaway. Howard sent these pix from Australia, showing one of these very rare instruments. Looking at the top photo; the carb is bolted onto the intake manifold tube on the left side (the square bolt head for clamping the carb can be seen past the tickle button). The air intake is on the right, and you can see the connection between the float chamber on the left and the main jet which is in the middle of the brass apparatus towards the bellmouth. The wing nut controls a needle on the main jet with effectively varies the size of the aperture, although as this carb is meant for alcohol, not much finesse is involved. The air intake is controlled by a butterfly valve at the bellmout, although instead of rotating around a fixed shaft in the middle of the bore, the valve acts more like a trap door, being hinged at the bottom. The cable is connected to a small extension on the 'door' - very direct!
The design creates something of a 'ram air' effect, being such a long tube, and is suprisingly similar to a Wal Phillips Fuel Injector. Very simple, but apparently for full-bore track work, it was the hot ticket in the 'teens and early '20's.