Eagle Ducati

EAGLE DUCATI 1

Giancarlo Rossi was the uncle of the late Marco Simoncelli and is a passionate collector of racing motorcycles with a story. Mostly Ducatis. Including my Eagle-Ducati 1. I never thought that it would resurface with so much emotional strength and now I am sitting here recalling an adventure that, looking back at the whole thing with a few extra wisdom teeth in place, appears definitely wild, with a few touches of epic.

My Eagle-Ducati in its original, road going form, very compact and light

For some reason, I only have these two pictures of the bike the way I built it and rode it, and these are cheap prints
from an automatic machine that cut half of the front wheel off.

This is the story of my Eagle-Ducatis, 1 and 2. Back from College in South Carolina in 1970, first I was hired by Alfa Romeo Aerospace Div., which would be my real business, but since there was no real R&D Dept. there, I started playing with motorcycles and writing technical features on the only motorcycle magazine then on the local media market: Motociclismo. In addition I paid regular visits to Dr. Vincenzo Surace, the real brain behind the AlfA 33.3, that paraded at the 24 Hours of Daytona, and the 3.0 liter Alfa-Brabham F1 boxer 12 and V12. Supported by his positive comments, in 1971 I developed a rather innovative scheme of SOHC three valve distribution that met the interest of the Piaggio technical staff, then busy at resurrecting the Gilera brand. While visiting Dr. Fabio Taglioni at Ducati, I had a glimpse at his drawings of the “bevel gear” 750cc Vee Twin and then started a great friendship that would last till he departed from this world. Not that our friendship was all cheers and smiles. Dr. T and myself were from the same slice of Northern Italy where motorcycles are so much part of the local passions that they are called just “motor”, after the most dominant part of the whole. 

Arturo Venanzi at the Misano 1000 Km rode superbly, his lap record stood for three years, in the face of much more powerful bikes

Our first, flaming fight came when, pondering what the enthusiasts would expect from the new 750-900 V Twin in terms of performance AND reliability, I suggested that we should dump once and for all the old style pressed together crank assemblies (and related needle cages) and enter the age of solid cranks and plain bearings. He almost fired me. Next came my criticisms about the chassis of the new and very hot Ducati 750/900 SS. At that time, Ducati had no real frame designer in the R&D department, or even a good specialist among the testers. No one was a frame specialist at Ducati, because the creed there was “engine!engine!engine!”. The frame was an optional that was there only to keep the wheels in line. Same as at Ferrari at that time. Dr. Taglioni made very accurate calculations about the structure (the 750/900 SS frame had excellent torsional rigidity), but steering geometry and weight distribution bias were left to his “visual” intuition. 

The Eagle-Ducati on the grid a Misano, on the right is chief mechanic Sergio Baroncini

Being a strong follower of the great tradition of British frames specialists, I dared defining inappropriate that combination of excessive steering geometry and grossly rearward biased weight distribution that made the old Ducati 750/900 a slow steerer, and with a front end that developed a heavy tendency to plow when pushed hard into slow to medium corners. In general, to me the bike appeared to be needlessly tall and plain huge, though it was built around an engine that indeed was rather long, but also slim and not particularly tall. Dr. T. listened to my criticisms and finally froze me with his: ”OK dePrato, let’s see how good you are when it comes to motorcycle frames”. The glove was thrown, and it was Dr. Taglioni’s own glove and you better believe that I took the whole thing very seriously. It was like I had been asked to pass yet another test in mechanical-structural engineering, but with Dr. Taglioni that was common practice and it was ok to me. 

The bike as it is now, beautifully kept by Giancarlo Rossi

It took me about one week to put everything together. I had designed a very compact, very sturdy backbone style frame inspired to those that Swiss master craftsman Fritz Egli had designed to harness the mighty Vincent 1000cc Vee Twin. The huge, 100mm gauge 1.5mm, backbone tube granted super torsional rigidity. To obtain a structure perfectly rigid also on all flectional axes, I integrated the engine (conceived to this purpose by Dr. Taglioni) into the frame more thoroughly than it was on the Ducati 750-900 SS chassis, and on all Egli frames of the time. To this purpose I designed four triangulated tubular elements to connect the backbone tube to the two front and to the four rear mounting bosses of the engine. The triangulated structures were immensely stiffer than the customary downtubes used on Ducati and Egli chassis. And so was the whole chassis. But the structural differences were almost marginal compared to the geometrical ones, because Dr. Taglioni certainly knew structural calculation. 

 

Three views of the bare frame, to show its very strong and neat structure

The Ducati 750-900 chassis spanned an enormous 61.5 in. wheelbase and its front end geometry used a lot of rake, 30 degrees, that produced 5.5 in. trail in combination with 1.0 in. offset triclamps. I went for 27 degrees and 4.0 in. trail, but, most important, I pulled the front wheel all the way back, while keeping the same rear swingarm center-to-center measurement, in order to radically readjust the weight distribution bias and shorten the wheelbase. In the process I also lowered the seat height by about 1.0 in. In all, my chassis spanned a 58.3 in. wheelbase, thus 2.5 in. shorter than the original Ducati one, and all that was chopped off the front end. Fritz Egli was extremely enthusiastic about the whole project, both because he fully approved my technical approach and because it was opening new perspectives to his business, since at the time he was running out of Vincent 1000cc Vee Twins. 

These were the original Marzocchi shock absorbers adopted for the race

It was Springtime 1973 when he welded the test unit and sent it to me to check the correctness of all fittings, which was perfect. Then I got my copy of the production item, duly nickel plated, as he used to finish his frames. My budget was very lean, so Dr. Taglioni helped me out with a 750 SS engine that had been sitting for a while in the race department. Nothing special, just a good mule engine left alone for a while since development was totally focused on the new 900cc unit. I went to Ceriani for one of their fabled racing forks, those featuring “Coke bottle style” sliders. They had no provision for disc brake calipers mount, since at the time the same Giacomo Agostini still preferred drum brakes for his MV Agusta racers. I hated drum brakes, but I loved those Ceriani forks and I had a hi-tech trick up my sleeve: the Campagnolo Hydroconic brake. Mr. Tullio Campagnolo, of cycling gearing fame, was an old, visionary gentleman capable of incredible technical inventiveness. A few years before he started developing a new concept of brake, inspired to aircraft type brakes, that finally evolved into the Hydroconic design. 

The front end with the Marzocchi fork and the tiny 280mm Brembo disc brakes

The Campagnolo Hydroconic brake system was extensively used by Walter Villa on his 250-350cc World Title winning Harley Davidson and when Mr. Tullio Campagnolo asked me to test it for road use, I checked with Walter about his experience and I confirmed my availability for the tests after Walter assured me that the thing worked fine. After all I loved its clean design, drum brake style that allowed me to use those gorgeous Ceriani GP forks. I modeled the tank and the seat after those of the legendary Harley XR 750 RR. An old craftsman hammered aluminum sheets of appropriate gauge to perfectly match the wooden molds and he did a great job. Body parts were painted black, with gold pin-striping, while a friend produced a good supply of stickers reproducing the Screaming Eagle of the 101st Airborne Div. shoulder patch, surmounted by the EAGLE logo (obviously in place of AIRBORNE). Only the profile of the shield did not match the real thing, but that was a very good effort anyway. And got the message out right.

The bike is lean also in its front view

In Bologna there was only one shop for special Ducatis: NCR, and there a brought all my bits and pieces to be duly assembled. Owners Giorgio Nepoti and Rino Caracchi were good friends, they assembled my Eagle-Ducati, but they did not like it much, because it was not a real, whole Ducati. They did a good job, except for the rear light and related plate support, just awful. But the rest was impeccable, and my Eagle looked so much smaller and more compact than a Ducati 750/900 SS. And very essential too, tipping the scale at a mere 345 pounds (kick starter only). In 1975 Cook Neilson rode the Phil Schilling prepared Ducati 750 SS to his first victory at Daytona and he was invited by Ducati for well deserved honors and celebrations. I was part of the welcome party and I cowardly abused of my position to force him to take a detour to briefly look at my Eagle-Ducati. I guess he liked it. 

The seat is perfectly reproduced and still shows that is was inspired to that of the Harley-Davidson XR 750 RR

I rode my bike on a regular basis, using a cloned dealer plate for the purpose, since it would never pass any homologation test. It was fun, it was adequately fast, but above all it was great on twisty backroads. At the time I had quit Ducati to become technical editor of the pair of Italian weekly motor magazine: Autosprint and Motosprint. In 1978 a young man full of enthusiasm for the sport came to me and asked me if the bike was on sale. I do not know how he heard of my Eagle-Ducati, I never publicized it, but I must say that I welcome his offer because constantly staying on the lookout when riding in order to dodge the attentions of the Highway Patrol was getting heavy on my nerves, but I kept this to myself so I had a very good deal. The sponsor wanted me in the team as technical manager and we started working to turn my Eagle into a real racer. First we bought one of the 900 SR engines that Ducati produced in limited number to respond to the demand of endurance teams. I always loved endurance races, they were the only ones I covered in addition to my technical editor job. Those were good, reliable engines, featuring sand-cast crankcases and very accurately machined by Ducati Tooling Dept., same as the Factory/NCR Team stuff. Power, for the time, was acceptable, about 80 real Hp. To get more horses some friendly attention from Franco Farnè, Ducati Chief Race Mechanic, was needed. But he was also the third of the NCR partners and, same as Giorgio and Rino, he was totally devoted to support, tune and hone to perfection only what came out of Ducati. And in fact the semi-official NCR-Ducati bikes had engines bored to 950cc, special heads and (above all) cams and absolutely exclusive 41mm Dell’Orto PHM carbs, for a real 100+Hp. We had to be content with the engine in its standard state of tuning as it came from the Factory. But my mechanic was a very good one, Sergio Baroncini, who had acquired a great level of experience racing Ducati 250-350-450 singles in the Italian FMI championship, so, at least, we could count on some very reliable 80Hps. 

My baby still looks very elegant and compact for a 900cc bike

Out went that lovely Ceriani fork and the Campagnolo Hydroconic braking system, front and rear. In went a much stronger 38mm Marzocchi front fork and a whole Brembo braking system. In return to my trust in his Hydroconic brake, Mr. Tullio Campagnolo granted me a supply of his impeccable 18 in. magnesium wheels in the right rim sizes, to be shod with the best rubber of the time for the purpose: Dunlop K81. A full fairing was added and the Eagle was re-painted in the sponsor’s light blue color. Time was tight to the Misano 1000 Kilometer race, the first of the Endurance World Championship season. The young, enthusiastic man, by the name Giorgio Boselli, proved totally inadequate to the job: on our first test together he lapped Misano at a slower time than me on a Honda CN400, let alone when I was on my well massaged Eagle, so much more muscular than it was when I rode it to work and back. I was fast at Misano, but I never thought of racing, I had no time, so I never had an FIM license. The race was only a week away and I called Arturo Venanzi, a very good friend and a good rider, having won the Italian 350cc GP title the year before. He was very enthusiastic about the new racing opportunity and made himself available for the first practice session. And very fast he was. We needed a second rider to team up with him and Arturo suggested that Graziano Rossi (Valentino’s father) had no bike for the race, and called him immediately. Graziano rushed to Misano, but the NCR team protested his entry for being registered too late. They had heard of the pretty fast lap times set by Arturo Venanzi and Graziano might be even faster. 

A ¾ rear view

They also protested the exhaust system that Ducati supplied with the engine, so we had to choke it up a little, throwing away a couple of ponies. But the real problem was the lack of a second rider. Luckily Sergio found a young rider with a valid registration, but whose bike had been withdrawn, Francesco Natalini. He was rather green and inexperienced, but he appeared determined to do his very best, and in fact the two set lap times that put my Eagle Ducati on the fifth spot of the grid. Arturo took the start and set himself in the leading pack, led by Marco Lucchinelli on a very fast Ducati NCR. Then, to my delight, I saw my light blue Eagle gain positions, lap by lap, till it zapped Lucchinelli’s NCR Ducati and was out in the lead! That was too much! The cheers lasted only a few laps. Suddenly Arturo started losing positions due to a misfiring engine due to a dying battery, caused by a bridging connection that was missing in the electric regulator supplied with the engine. We kept changing and recharging batteries at every stop, but our race had gone down the drain anyway. Arturo saved the day by setting the lap record for the class in 1 min. 28 sec. 6/10, 2/10 quicker than Lucchinelli who, to keep pace with my Eagle, had broken the rocker arms of the desmo valve train of his NCR Ducati engine, due to the rather brutal acceleration of their ultra-hot desmo cams grinding. Franco Farnè and the NCR gang affirmed that the time keepers were wrong. But the one and only Dr. Taglioni walked over to me to shake hands and congratulate me for my chassis project; and he added “I am not a frame specialist”. Wow, that was like an additional graduation diploma. With this, the final balance turned out to be very positive, also from the point of view of the sponsor, who gave me instructions to prepare the bike for the Bol d’Or. Ducati Racing Department offered a complete check and overhaul job for the race. A real bonus for a small team, so Sergio took the engine to the factory. For the “Bol” Arturo Venanzi “hired” Graziano Rossi and the two made a great team, with the right spirit to handle the 24 hour feat and the ability to bring the bike home and in good final position. 

Same as the seat, the tank was inspired to the XR750 RR unit. Giancarlo Rossi tried to imitate the original crest, I gave him a good supply of the real thing.

We all knew that we did not have the power to win, especially on a very fast track like Paul Ricard, so we all agreed about a rather conservative strategy. First test proved that we had to be ultra-conservative. After a few laps Arturo came in reporting “This is not our Misano engine, this is a sheep of an engine”, and Graziano joked “Down that long “Mistral” straight they pass me with so much speed differential that I might feel like being standing”. The engine was so mild that it would not pull the due revs with any of the sprockets I had provided. But at least it would last 48, not just 24 hours. Nevertheless, Arturo and Graziano were able to qualify the Eagle around the middle of a 54 bikes pack. After three hours things appeared a little rosier that we expected: the Eagle was steadily racing around the 13th-15th position, and we all knew that by midnight the ultra-hot shots, like the Yamaha TZ700, would pack-up. If everything was running smoothly as it did for the first 3 hours we might finish within the first 10, at least. In the meantime the Factory Ducati was battling for front spots against those same ultra-hot Yamaha TZ700 and I must say that keeping pace with a TZ700 was a show of superb performance by that Ducati-NCR. By the fourth hour my hopes collapsed. A Kawasaki 900 bored to an illegal 1200cc exploded lubricating a large section of the track. Before the slippery situation was duly flagged, eight bikes crashed, including my Eagle. That was the end of the whole adventure.

Giancarlo Rossi and me and the bare Eagle-Ducati

We picked up the pieces and headed for home. But that was not the real end. A few days later, while working to refurbish the Eagle, our technician Sergio Baroncini called and said “these are not our racing cams, these are street cams”. Ah, not bad at all! That explained why my calculations about the final gearing numbers were wrong. They were real sports at Ducati and NCR! The sponsor quit in disgust, he put the Eagle in his dean for a while, then sold it. The Eagle-Ducati 1 changed hands a number of times, finally ending in Germany. Then Giancarlo Rossi bought it. The bike is not in its original shape, and could never be after all these years. The seat is right, and the tank too, but it’s made of fiberglass, though correctly molded after the original aluminum tank. The color is the sponsor’s light blue. But “she” still looks right to me. My baby.

 

EAGLE DUCATI 2

Despite of all odds, I gave a second try to the old challenge, on the basis of the Eagle 1 experience. Eagle 2 was a good effort in advanced motorcycle chassis engineering, but the whole adventure was a lot less gratifying and a lot less epic. Times had changed. Fritz Egli had focused his great technical abilities on the tuning of very hot Corvettes and at the time it was hard finding good craftsmen ready to cooperate with that extra dose of enthusiasm that I had to count on to make sure that things would proceed in the right direction, and at the right cost. It was not easy and completing the bike took so much time that the bike was no longer eligible to race under the new FIM rules. 

My Eagle-Ducati 2 only raced at Mugello in a minor event, proving fast and surefooted

Still I love my Eagle 2 for the concepts I incorporated in the project. First, the frame structure. I started with a huge backbone, same as with the Eagle 1, but shorter, to make the head of the vertical cylinder easily accessible for servicing. The triangulated element connecting the backbone tube to the engine mounts intersected to obtain a three-dimensional, pyramidal structure, super stiff. The engine was set a little higher than on the Eagle 1, where on turn it was set higher than in the Ducati frame, while the seat height was same as on the Eagle 1.

The Eagle-Ducati 2 being tested at Mugello, the removed lower half of the fairing exposes the fuel tank under the engine

The increased ground clearance allowed me to locate the gas tank under the engine. It was fabricated from aluminum sheet and was shaped to fit inside the lower half of the fairing. To make it stronger and safer, the aluminum shell was wrapped in fiberglass for extra sturdiness. It was slim to stay out of the way in case of crash, protected by the fiberglass of the fairing, by the tires, and by the pyramid structure of the frame, yet it held a healthy 5.5 gallons.

Front and rear view of the Eagle- Ducati 2

An immersed fuel pump would feed a small, 1 gallon tank located in a standard tank position, complete with cap. Refueling would happen thru there, while a properly located hose of adequate diameter would flow fuel to the main tank, while leaving up there all the fuel needed to fill the bowls of the Dell’Orto carburetors, by gravity. The front end geometry was a minor evolution of the previous one, with 26 degrees rake, 4.3 in. trail with 1.0 in. offset triclamps and 18 in. front wheel. The rear suspension was my special trick: parallelogram type, with arms hinged directly to the massive rear engine mounts. Wheelbase was slightly increased to 59.0 in. for an even more correctly balanced weight distribution bias.

The new frame was immensely stiffer and much more functional than the first one and the rear parallelogram suspension worked perfectly

I enlarged the engine to the limit 950cc and to stay away from all Ducati/NCR tricks and back stabbings, I discarded the whole desmo valve train and went to a regular “spring” valve train, developing an advanced polidyne cam profile that proved ultra-performing, and in total safety. I never rode the bike on the road. I conceived it for racing, but unfortunately it never raced. I rode it for testing at the racetrack and it proved very surefooted, nimble, totally predictable in its dynamic reactions and with great traction even at extreme lean angles.

The longer swingarm granted  a perfect weight distribution bias in a bike that sported a wheelbase much more compact than the original Ducati 900SS unit 
and the parallelogram unit hinged directly to the engine delivered super traction with no rear wheel spin

The collector who bought it raced it with success in club races till it was worn out. Then sold it, but kept that magic non-desmo 950cc “bevel gear” Ducati Twin for himself. It would turn to 9,500RPM, easily and make very, very good power. The great Doctor T would not approve, but once he checked the power curve he would come over and shake hands. He was like that and no one at Ducati ever was (and is today) like him.

Bruno dePrato          

courtesy of webmatter.de