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Um, no. Just another example of how the cheapest solution is the way Guzzi is run now. If the pressed together crank is a better solution, why are they still using the forged crank on the V85?
I'm riding with Chuck on this one. I have been riding motorcycle continuously for the vast majority of my life, and I have yet to wear a single motor out.
Still confused. I can't see why a pressed crank is cheaper than a solid one. Also is the Guzzi crank forged or cast? I don't think my Corvette has a forged crank (the rods are powdered metal, forged and cracked)
I believe the forged and cracked conrods is the latest and greatest tech for strong rods
Wait, I always thought that pressed cranks were quite a bit more labor intensive and expensive to build. This is the first time I've ever read the opposite. I don't know why two piece rods could be revved at higher RPMs and more stress than one piece rods; if there is a difference, I'd think would be the other way around. OK, since I'm the least mechanically inclined person on the Board, someone please educate me.Thanks.
Does this Cycleworld comment raise an eyebrow with anyone?"An unexpected and fairly radical technical modification separating the V7/V9 V-twin engine from all previous editions, and from the V85 TT, is that the crankshaft here is of the press-fit type, with one-piece con-rods turning on plain bearings, rather than a forged one-piece unit. This follows the same engineering approach used on all Piaggio four-stroke scooter singles. Reducing production cost is the ultimate reason for the change. The more powerful, higher-revving V85 TT retains its solid forged crankshaft and cap-type rod."
John,The modern HD engine (45deg) has two separate rods,(not two piece). They are called a fork and blade set up so one rod (the blade) fits into the other rod(fork) and when the holes for the crank pin are lined up roller bearings are pressed in and then assembled onto the crank pin and then the whole thing is pressed together using terrific pressure.This is done so the cylinders are lined up on the crankcase in a straight fore and aft line, therefore no shaking moment. Your Guzzi cylinders are off set...shaking moment present.That's the why.With the 45 deg setup there is enough back and forth rocking that vibration is a problem so one thing the designers did was eliminate the shaking moment as much as possible.The RR merlin engine used in the P-51 is a V12 and in order to minimize vibration they used the same method, as in blade and fork rods.These rods are difficult to machine correctly thus labor intensive and $$$.As for being cheaper to press together???, by using the roller bearings and having a flywheel on each side, the HD method of pressing them together makes some sense rather than the tapered shaft with nuts torqued on both ends. Unknown.It works but I know folks that are designing and have been testing a forged single piece crank with a master and an articulated rod (plain bearings) and have been riding test machines for about a year.FWIW:-)
Whatever it has I am sure I wont be able to wear it out if I knuckle under to Anniversary edition V7 bike lust.
I love that they copied my photoshopping on the side covers!
Kev is officially on the blame line........
Thanks Mike, I knew HD had the "knife and fork" rods but I didn't know why. In fact keeping the cylinders directly in line would keep the rear one totally out of air flow. I never considered that vibration from the 45 degree V, might be the reason. I did think the Master Rod was the fork and the Articulated Rod was the blade. Odd cylinder radial engines a have master rod and the the articulated rods are "pushers followers".
No the primary reason for it in Harleys case was simply expedience and a minimal design change to effect a twin cylinder engine and then like Chevrolet when they had to design a new V8 engine they stuck to pushrods primarily because that's what they had experience with and were too conservative to go the way of the rest of the world to OHC.
I think Harley did it their way because it was 1908 at the time, and there wasnít a whole of prior experience one way or the other. That which did exist was with early aircraft engines.Re the V8 Chevrolet engine: the rest of the world (outside of the US industry) wasnít doing a whole lot with high volume production automotive V8s in 1955, or high volume OHC car engines in 1955 either. However Chevrolet was planning on making a whole lot of them, for example 100,000,000 small block V8s were eventually built, and I think they had fundamentally the right idea. It wasnít exactly the product of arbitrary decision, it was more like genius. The extremely low cost and completely effective valve gear and rocker arrangement was part of it.
If you read the history of the Gen111 engine the pushrod comfort factor/no OHC experience among its design team was a big component of the design decision to not go OHC. However in defence of Chevrolet the engine is very compact and used in everything from delivery trucks to Corvettes in various stages of tune. I've owned Gen111 engines in 2 cars and am actually a fan of them however Ford when faced with a similar decision did decide to go DOHC which I'd like to have in either a Cobra replica or GT40 replica one day. There's a long path from what the engineering team would like and what pops out the production line:)Ciao
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