Home  Case Studies Motorsport Case Study. Camcover of Ilmor MotoGP 4 strokes engine: follow up
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After the dyno test, there are the first notes coming from Ilmor engineers about the innovative project. They explain whatever we need to understand, therefore we just report their exact words.
First let’s remind what we are speaking about.
The CAMSHAFT COVER is the structural part that supports the bearing of the camshaft (camshafts seats, the camshaft usually runs at more or less 9000 rpm), directly applied on the 4 stroke 800cc engine head. Inside there is also the lubricant oil.
Average working temperature: 130-140 °C.
Every material has a temperature limit over which it is recommended not to go. Mechanical properties decrease when the working temperature increases. The recommended limit for Windform XT is 130/140 °C but in some case 150-160 °C also can be reached. The limiting factor comes from the thermoplastic base that melts around 180 °C.
At a track like Bahrain or Dubai, even if the ambient temperature is significantly higher than the average at other circuits, the working parameters of the engine (i.e. water and oil temperature) must remain under the limits imposed by the manufacturer. There are usually specific radiators and special aero configurations to ensure a better cooling of the engine.
The improvements this project achieves are as follows:
- Lightness (of the engine head cover. Being on top of the engine, each saved gram means better rideability of the bike, allowing to lower the centre of mass) (- 31%)
- Reliability
- Fast modifications and production (the possibility to change during the season some features of the part)
- better cooling of the engine.
The result is a composite part where the different materials have a specific function or structural competence.
Around a main-frame in metal-ceramic matrix (aluminium MMC), a shell made by carbon fibre filled resin (Windform XT), was created. The shell is therefore, the result of powder sintering using high performing CRP developed material (Windform XT), directly from a mathematic model in a few hours. The main areas of the part(camshaft seats) are made by a series of simple cutting and welding processes, while the prototype shell has the complex shape. In fact, being made by selective laser sintering, any complex shape can be obtained without undercut problems (a typical limit of CNC machining process) or supports (a typical limit of other Rapid Prototyping technologies).
The existing SLS technology also allows to make engine components such as intake trumpets, water pump covers, oil pump covers, airbox and sump scrapers. It obviously varies from engine to engine.
Ian Watson (Ilmor Senior Designer) explains, about the dyno test:
“The engine ran with the cam cover. It only did something like the equivalent of 100km, but it was all full speed power run testing. There was absolutely no problem at all - no leaks, no performance difference and judged to be a complete success.
On disassembly all the internal head components appear to be in normal condition, there is no sign of any distress or any potential problems.
However, the bond between the aluminium bearing straps and the WindForm has failed. The straps are still in place but it is possible to move them by hand. I'm not sure why this has happened. There is no sign of any movement (no fretting visible), so I think that whilst it was clamped up it was perfectly okay. Perhaps the differential expansion is the culprit.
I am not too disappointed by the glue failure.
I think that the situation we have is that we have enough evidence to say that it would be possible to consider designing 'major constructional components' with both the material and the process.
However, this will only be completely successful if the component and surrounding components are designed from the outset with the process and material in mind.
I think you have done a fantastic job with the cam cover, however, I think that the difficulties with situations like the aluminium/WindForm bond are somewhat artificial in that in this case it became a necessity due to the overall design of the cylinder head with regard to the relative positioning of the cam bearing straps etc.
If I were to design the engine again and wanted to have a structural WindForm cam cover (rather than separate cam caps/ladder and a cover just to seal the oil), I would look at a different stud arrangement, the camshaft spacing and the camshaft bearing size to allow the cover to be one-piece with a plain bearing shell. Maybe we would still need to have some inserts to help with distributing the clamping load, but such things would be relatively easy to organise.
I think that the whole subject of making things by 'rapid' processes is very exciting and opens the door to loads of things that are not currently considered. But, in the same way that all through the design process of a cylinder head (for example) the designer currently is making decisions based on the knowledge that it is going to be produced as a sand casting, the process needs to be considered with an open and fresh mind to take the whole design forward to new ground. I think that this is a point which came across at the Loughborough conference but is something a lot of people seem to have difficulty with, perhaps because it threatens their current 'comfort zones'!?”
A promising consideration for next generation of engineers: it does seem that the only limit is the design process and therefore designers’ knowledge. For open-minded technicians a new path is ready to be pursed.
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