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In 2002 Honda introduced the RC211V motorcycle to MotoGP, the highest level of motorcycle racing in the world. The bike was a response to the chaning rules of Moto GP and replaced Honda's previous contender, the iconic two stroke NSR500.
Now the big deal about the new bike is that it's engine was something that no one had ever seen before, a V5. I mean over the decades we have been conditioned into thinking that a V engine must have an even number of cylinders, V2, V4, V6, V8, V10, V12. And Logically it makas sense....we have two banks of cylinders and both banks have the same number of cylinders which means that neither bank is generating more force than the other bank leading to a well balanced engine.
The general public was so puzzled by the V5 engine, which has 3 cylinders in one bank and 2 cylinders in the other that soon rumors spread claiming that the bank with two cylinders had larger bores and larger pistons to restore balance. This of course wasn't the case, all pistons and bores are of the same size. But even to this day, many people believe that a V5 engine is impossible and would self-destruct in operation. However Honda proved this wasn't the case, not only did the engine NOT self-destruct, it revved continuously and reliably to 14.000 rpm, and it did it it's job so well that it helped Honda win three rider and four constructor world championships. In fact the bike won 48 out of 82 races, it won more than half of all the races it entered, which is an extremely impressive statistic for MotoGP and even more impressive for an engine that should self-destruct according to layman logic.
How do you make a V5 work? Well the answer is pretty simple....you make it work by building an unbalanced V4 and then using the extra piston to balance things out.
So how do you unbalance a V4? Well that's easy, you loose the 90 degree angle between the banks that allows the counterweights to keep things balanced. This why Honda gave their V5 an angle of 75.5 degrees between the two banks. The added bonus of this is that it makes the engine even more compact and allows the wheelbase of the motorcycle to be shorter which improves handling response.
But why exactly 75.5 degrees? Why not 80 or 70 or whatever else. Well the answer to that is that 75.5 is the point at which the piston of an internal combustion engine is at or near it's maximum velocity.
And why is this important? Well to understand that we have to observe the V5 engine in action. As you can see Honda's V5 is essentially a V4 with zero degrees offset between the two common crank pins, and an unpaired piston on a single crank pin between the two piston pairs. As we know the angle between the two banks is 75.5 degrees and the crank pin of the unpaired piston is offset by 104.5 degrees from the center-line of bank 1 when the engine is in this position. These angles result in the forces created by the engine canceling each other out. See video for actual detailed explanation with graphics.
One more final side-point just in case someone is wondering. No, the engine called V5 by Volkswagen does not work like the one we just discussed. As far as I know the V5 in Honda's RC211V is the only one of it's kind and it was never mass produced, it was made only to compete in Moto GP. What Volkswagen calls V5 isn't really a V5, a much more appropriate name for it would be VR5, in the same fashion as their VR6 engine. Honda's V5 is a true V engine with two cylinder heads and two sets of camshafts, cam gears, etc. Volkswagen V5 is just like a VR6 but with one cylinder less, meaning that we have only I believe only 15 degrees between the banks, one cylinder head, one set of cams etc. And just like the VR6 has balance very similar to an inline 6, so too does VW's „V5“ have very similar balance to an inline 5
A special thank you to my patrons:
Daniel
Daniel Morgan
Pepe
Brian Alvarez
Jack H
Dave Westwood
Joe C
Zwoa Meda Beda
Toma Marini
Nelson
00:00 MotoGP champion
02:43 The role of the counterweight
04:37 The magic of a 90 degree V
07:00 Velocity and acceleration
10:42 Balancing using imbalances
15:20 Volkswagen "V5"
#d4a #v5 #enginebalance
