90 VS90 ENG version

di Giorgio Mulliri

90 VS90     ENG version

In Nakamoto san's recent interview to SOLOMOTO, he finally “admits” that the RCV213's engine is infact a 90° V4, just like Ducati's Desmo.


The same configuration as Ducati, so heavily criticised in these last years.
The Japanese engineer claims that this engineering decision was made to solve a problem encountered when creating the 1000cc engine from the 800cc one.
The problems encountered with the new design apparently derived from the constraint to maintain the same cylinder diameter, fixed by regulations to 81mm.
The only solution was to lengthen the stroke in order to add the necessary 200cc required by new regulations.


Problem: if the cylinders were to be lengthened it was evident that the existing dimensions, which had been carefully studied and obtained with effort in order to hone a perfectly competitive and winning bike over  years of designing, testing and racing, were going to be perturbed. Redesign was required, in order to make it work as well as the 800...


Simply adding 6mm to the stroke, would modify the bike's heavily researched equilibrium also with the frame and tyres, even though minor annoying chattering problems had manifested themselves, blamed on tyre characteristics and last minute ballast addition (but these effects had also been observed at the end of the 2011 season, without the ballast and new tyres).


Solution: open the V from 75° to 90°, thus encountering an increase in overall engine length. A few extra cm of space available infront of the radiator allowed this jewel of Japanese technology to be nestled within a well tried and tested frame, both in terms of dimension and flexibility characteristics in strategic locations.

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The original 72° V was not centred about the vertical but rotated forward.

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Subsequently the forward block was further inclined forward, making visible through the fairing cooling duct, part of the cylinder head and cover, whereas before (on the RCV212) only part of the exhaust header was visible.
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No photos currently exist which prove beyond doubt that the new Honda engine is a 90° V.
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Neil Spalding, engineer and journalist who authored the Solomoto article, supplies photos of details which highlight this change, with the added confirmation of Nakamoto, so no doubt remains.

This latest news brought me to think over what Spalding and Nakamoto affirm, that with the right alchemy of dimensions and flexibilities Honda managed to be successful using a 90° engine, unanimously (except for Preziosi) thought to be impossible...
I attempted, with all my powerful means... (internet, photos, correl, photoshop, a lot of time and patience), to superimpose the Ducati frame on the RCV213, trying to respect as much as possible fundamental reference dimensions in order to reliably evaluate dimensions and positions.


I superimposed the two bikes, as done in a previous article, referencing wheel centres and steering head.

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Given there isn't the absolute certainty the dimensions are exact, even a few cm difference on the rear wheel don't excessively change the strategic positioning of some elements, or at the very least it is evident that certain parts do not coincide as expected.


Firstly I would like to point out that, not having found specific photos in circulation of the material necessary to elaborate my data, I adapted an old 72° (V5) HRC engine, and a Ducati Desmosedici RR road bike engine, which derives from Capirossi's 2003 bike successively adapted to the road bike, quite similar to the current design.

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Let's start... a not so easy task...

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Bear in mind the blue line with positions indicated as swing arm pivot, top shock mouting point, rear engine block support, front engine frame support.
For the GP12 I extrapolated a  frame created with photoshop subsequently placed over the Honda one, and highlighted all the points of interest, then added the RR engine image in order to bear in mind its relative position and supports.

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Now, let's overlay the extrapolated Ducati frame on the Honda one, with the Ducati frame accurately reflecting what appears as the superimposition of the photos of the two bikes with the wheelbase and steering head aligned, as in photo 5.

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Already from this photo elaboration the differences of some significant points are evident, such as the position of the Ducati engine and rear shock mount, which are notably farther back.

Now let's complicte our lives somewhat...
In the following photo, the points discussed are highlighted, both for the Ducati engine and the Honda engine.

For clarity's sake, better to specify the points pictured in the elaboration.

N1 Shock mount
N2 Swingarm pivot
N3 Engine support (front block)
N4 Engine support (rear block)

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Take your time to study the photo...
Now follow the blue line (Honda) which works out beautifully in this layout.
Red line................. unfortunately does not work out as well as the blue one.
Summarising: the photos are quite precise in their positioning, and are on the same scale.

All the elaborations are solely intended to support the reasoning, and do not claim to be religion.

That the Honda engine is smaller than the Ducati engine was known or suspected.
The position of the Ducati engine within the frame, shows that that frame was made around a pre existing engine (Burgess rules), adapted for the position of the gearbox shafts with new sump fusions in order to incline it backwards.

I have been repeating that it is my firm belief that the real GP12, was meant to be born out of the experience of this bike, which I have always defined as a test bed, made to experiment possible solutions.

No criticism and no judgement, just the resignation that the real GP12 was probably aborted, and “forcefully” abandoned by its father. Or maybe....
The Ducatis seen in Jerez, do not allow us to see if something “significant” is happening.


In order to make it competitive they will have to cater for that very exuberant engine, in all respects.
Nakamoto finetuned to mm and balancing of engines. As far as component positioning and engine dimensions are concerned, the basis for a competitive bike were there and they succeeded in finding the right alchemy.
Other ways exist, besides the Honda one. Can positions so different as seen on the GP12 allow the bike from Bologna to become competitive? I really hope so.

It's raining in Malaga, in Jerez too....


Thanks Adam for translating

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