OSSA

From New Ossa

From New Ossa

We present the OSSA TR 280i

 

OSSA has developed a trial bike, based on a new, highly innovative concept. We have basically worked on redistributing the various parts of the bike logically in terms of the weight distribution and other conditioning factors such as some of the parts’ running temperature. One of these aspects is locating the filter box in a very high, easily-accessible position.

 

Parts such as the fuel tank, air filter box and radiator have been positioned with the needs of a trial bike in mind. This has been done rationally, with common sense and a clear objective: to make the new OSSA TR 280i a benchmark for this speciality, just as the first MAR – Mike Andrews Replica – was in 1972.

 

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The fact that the new TR 280i has an electronic-injection system has enabled its engineers to redistribute various parts without being constrained by the position of the traditional carburettor. "Sometimes the injection system has been put in the same place as the carburettor would have gone, with the fuel tank at the top of the bike, without considering the option of finding a new position for it. OSSA Factory let me start from scratch and that was a determining factor in taking on this project," said Xiu.

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Engine

 

Our work in finding the ideal location and set-up for the various parts has resulted in a very small engine with a tilted back reversed cylinder. The intention is to allow the injection system and filter box to be located at the top of the TR 280i. We at OSSA think it is perfectly valid to take the same logical approach to trial bikes as other manufacturers do to specialities such as motocross and enduro.

 

The new two-stroke engine is very compact with a sigle piece crankcase. The gear change extends out of the right-hand side and the crankshaft is opposite it on the left. Since the housing acts as the chassis, as it is the toughest part of the lot, it has been possible to make a compact block. This simplifies the possibility of access to gear ratios.

 

Another important aspect is that it is cheaper to maintain since it is really straightforward to work on the engine. It can be considered a conventional engine in terms of geometry or thermodynamics, but we have managed to design a highly compact unit. It is one of the smallest engines around.

 

The 3-litre fuel tank has been positioned where the radiator has traditionally gone on trial bikes in order to improve the weight distribution. The OSSA Factory team thinks that the lighter a trial bike is the greater the need for the centre of gravity to be shifted forward.

 

Placing the radiator behind the fuel tank and filter box prevents the radiator from getting covered in mud, which happens so often in trials with the resulting problems with the engine not being able to run at the right temperature.

 

A stationary motorcycle needs to be able to dissipate the heat from the engine and have a fan fitted on it like on the TR 280i. So although a motorbike used in a different speciality would need fresh air channelling, a trial bike does not. Since the fuel tank protects the radiator, the new TR 280i can run at a constant temperature without being held back by a dirty radiator.

 

Also, by inverting the cylinder we have been able to fit the inlet practically vertically behind the fuel tank, so the air comes in through the filter at one of the highest points on the bike. This makes the filter better isolated and it is much simpler to get at the filter itself through a cap. Some parts of the injection system are fitted inside underneath the cap. There the parts are not affected by either the engine itself or humidity.

 

When we distributed the motorbike’s parts we paid close attention to the temperature at which they would each operate. Since the cylinder is tilted back and the exhaust points backwards, the exhaust can start from the rear monoshock, which has a larger volume than on a conventional bike.

 

    Chassis

 

Built of aluminium and chrome molybdenum steel, the fuel tank has been tailored to the engine design and fitted towards the front of the bike as a tough part of the unit.

 

Cast aluminium parts have been fitted to the areas where there is usually a lot of welding and therefore weight on a chrome molybdenum chassis.

 

The steering pipe, treated aluminium tank, footrests and articulated rod support are also made of cast aluminium. The rest is made of chrome molybdenum steel with a very simple TIG-welded structure.

 

The suspension has been developed in conjunction with Öhlins (rear) and Marzocchi (front). The rear suspension has an innovative system with an articulated linkage that is well protected and integrated, and is directly joined to the cast part of the chassis. The Öhlins TTX system has been adapted to trial bikes. This is a system in which the piston valves and hydraulic adjustments have been put on the outside. This technology has already been used in motocross and has many advantages for adjustments in terms of simplicity and accessibility.

 

The front suspension is an upside-down Marzocchi fork, a kind of suspension that has not been used on trial bikes for years. However, unlike other experiences of adapting motocross or enduro suspension, an upside-down fork with aluminium bars has been designed for the TR 280i in close collaboration with Marzocchi, which is exclusive to trial bikes.

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      Why use an upside-down fork?

The logic behind the upside-down fork is distributing the forces so as to optimise the weight to the max. "The greatest force is in the lower base section, so it is only logical for the point under greatest strain to have the largest diameter. In conventional forks this has been solved by increasing the section or thickness of the bar. So in terms of stresses an upside-down fork has an advantage. Some manufacturers such as Öhlins will not even consider any kind of suspension other than upside-down suspension", said Xiu, the project manager. But why have they not been traditionally used on trial bikes?

 

The upside-down suspensions previously used came from other specialities and were applied to trial bikes. As the OSSA Factory teams sees it, the problem was that up until now no-one had developed a fork specifically for trial bikes. Hence the agreement between OSSA Factory and Marzocchi to develop an upside-down fork. Marzocchi knows how to make light aluminium forks and OSSA Factory knows the requirements for this speciality.

 

Last year Marzocchi showed us an upside-down fork and at OSSA Factory the project was adapted to the needs of modern trial bikes. "We think that if we remove the disadvantages of an upside-down fork we can open the path to developing lighter upside-down forks than are currently available, since their logical configuration of forces should allow us to make the unit lighter," said Josep Serra "Xiu".

 

A priori, there are two main disadvantages to using an upside-down fork on a trial bike:

 

1) The turning angle is reduced by the wider diameter of the bar, which interferes with the chassis: the solution that OSSA Factory provides on its TR 280i consists of putting the entire offset on the suspension brackets instead of spreading it between the brackets and the base of the fork. "This has also allowed us to move the brake calliper to the rear of the fork and have it operate through compression rather than traction," said Xiu.

 

2) Rigidity-torsion: the solution is an over-sized upside-down fork with a 40 mm diameter made of aluminium to reduce the effect of torsion bending as much as possible.

 

Having solved these two problems, all that remains is for our test rider to put the finishing touches to the bike and allow it to captivate our potential customers. "We have to open our eyes to evolution. Evolving is an important part of what OSSA Factory is", according to the project manager. Meanwhile, Marc Colomer is evolving this system with highly promising results.

 

OSSA Factory is entering bike trials with its own technology and an experienced team with the same competitive spirit as enabled the shamrock brand to triumph.

 

The new engine parts will be ready in December and testing of the completed motorbike will start in January. Production is planned to start in July 2010.

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OSSA Factory TR 280i TECHNICAL SPECIFICATIONS

 

Engine

 

Capacity 272.2 cc

Type Two-stroke single cylinder with a reed intake directly into the crankcase.

Cooling system Liquid.

Bore x stroke 76x60 mm

Fuel supply EFI Kokusan Battery-less System.

Ignition CDI Kokusan digital magnetic flywheel.

Clutch Hydraulic control.

Gear box 6-speed.

Transmission Primary through gears, secondary by chain.

Engine lubrication 2.5% mix

Gear and clutch lubrication 700 cc of Gear Extreme 75W oil

 

 

Chassis

 

Type: CR-MO steel tube profile with pipe and bottom made of cast aluminium.

Front suspension Marzocchi upside-down adjustable fork, 40 mm diameter.

Optional conventional Marzocchi 40 mm aluminium.

Rear suspension Variable progression system with TTX OHlins monoshock.

Front brake 185 mm diameter disk with four-piston calliper.

Rear brake 150 mm diameter disk with two-piston calliper.

Front wheel 28 spokes with a 2.75x21 tyre.

Rear wheel 28 spokes with a 4.00x18 tubeless tyre.

Engine protector Made of AA7075.

Kick-start Cast aluminium.

Gear and brake pedal: Cast aluminium with retractable toe.

 

 

Weight and dimensions

 

Wheelbase 1,328 mm

Seat height 655 mm

Tank capacity 3 litres <>
Dry weight 67 kg

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