Yamaha "invent" "new" triple

The trick thing to do would be making 3 very narrow singles with spllined crank ends and couplers so phasing could be change as conditions warrant.
 
The author claerly doesn't know much about Laverdas.

"The Jota had 180 degree crank throws, simply because its engine was a twin with an extra cylinder grafted on and Laverda only had the tooling to do it this way."

Doesn't know much about manufacturing processes either.  ::)

Cheers,
Cam
 
Makes me wonder what else he wrote is BS too.
One eyed man in the kingdom of the blind?
 
Makes me wonder what else he wrote is BS too.
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I remember him slating the K1200S at launch because of 'unacceptable' vibration on steady throttle.  Well, yes, the engine management system does lean off the mixture under cruise conditions...one reason why it delivers 40mpg and 167 bhp!  I don't agree that it makes the bike unacceptable and BMW didn't let him anywhere near their test fleet for quite some time after that.  I read his road tests in my newspaper every Saturday and wonder how he manages to get paid for 'em!  ???
 
Cam said:
The author claerly doesn't know much about Laverdas.
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Almost certainly true - though I'm in discussion with him since I've known him since we started at secondary school together when we were 11 years old. Were at each others' weddings and such like. I'll report back later!

[quote author=Cam]
"The Jota had 180 degree crank throws, simply because its engine was a twin with an extra cylinder grafted on and Laverda only had the tooling to do it this way."[/quote]

This got me thinking: what actually was the reason behind the 180 crank phasing? J-Lo suggests it was "to avoid excessive side pressure onto the crank bearings" which may not have translated too well from the French but sounds a bit suspect to me... While it clearly wasn't because they couldn't - what was it then?

[quote author=Cam]
Doesn't know much about manufacturing processes either.  ::)
[/quote]

Almost certainly true. He read mech eng at Imperial College London - but was so bike nuts that never quite managed to complete his degree. On the other hand, he does know a lot of very serious people at places like Cosworth and Riccardo - and checks his stuff there so is usually technically right!

If you look at the forum on that site, http://www.ashonbikes.com/forum/yamaha-3-cylinder-cross-plane-crank you will see some really serious and well informed debate about the possibilities. Includes a university professor!

He writes serious stuff about bikes - even though we might disagree with his conclusions (he has always liked big torquey bikes though!)

--
Dick
 
I heard that they tried the 120 initially but the rubber technology wasn't right to contain the different vibes. The 120 vibes buggered up the carbs quick time apparently.
They went to 180 phasing to overcome the carb/vibe issue.
Might be bollocks but I did read it somewhere back in the day.

I guess it's no surprise then that the 120s have rubber engine mnounts and rubber mounted carbs.
 
Grant said:
I heard that they tried the 120 initially but the rubber technology wasn't right to contain the different vibes. The 120 vibes buggered up the carbs quick time apparently.
They went to 180 phasing to overcome the carb/vibe issue.
Might be bollocks but I did read it somewhere back in the day.

I guess it's no surprise then that the 120s have rubber engine mnounts and rubber mounted carbs.
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I'm sure the early prototype 3c was a 120....and the vibes were a problem. They went 180. It was not just another cylinder grafted on to a twin crankshaft, pretty silly remark. Laverda should have marketed the 180 as a "cross plane engine" with the graphics and power pulse digital video..opps..no computers around in those days.
 
Laverda probably had the technology to make the 180 a crossplane crank but the flat plane crank they used was cheaper to produce.
Neale
 
Rusty Spokes said:
I'm sure the early prototype 3c was a 120....and the vibes were a problem. They went 180. It was not just another cylinder grafted on to a twin crankshaft, pretty silly remark. Laverda should have marketed the 180 as a "cross plane engine" with the graphics and power pulse digital video..opps..no computers around in those days.
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If you look at pictures of the very first triple prototype and/or read J-Lo's "Legendary Laverda" book, you will see/read that this was in effect a twin with an extra cylinder...

Laverda_4.jpg


In the meantime, in the forum, Kev has now corrected his remark in the article with:

[Quote author="Kevin Ash at [url=http://www.ashonbikes.com/forum/yamaha-3-cylinder-cross-plane-crank?page=3]http://www.ashonbikes.com/forum/yamaha-3-cylinder-cross-plane-crank?page=3[/url]"]
Wrongly explained, sorry! I was told that by a guy in the Laverda factory at Zane in the 1990s (which Laverda buffs don't even think of as the proper factory, that was at Breganze), who was their PR man, and the last person in the building! But I've been corrected by an old Laverda-riding friend (old Laverda, old friend...), and what I said doesn't fit anyway as the Lav triples had built-up cranks, not single-piece cast ones, so there'd be no issues with tooling.

It seems more likely, according to those in the know, that there were some issues with the prototypes' 120 degree cranks breaking, possibly due to the rocking couple inherent in the layout, and the 180 degree version was brought in to solve that problem. Presumably they were still busy trying to sort the issue while the 180 was on sale as they did eventually go to 120 for its better balance (its lower inertial torque wasn't in the fray in those days...) and there weren't, as far as I know, any problems with the cranks then.
[/quote]

--
Dick
 
1000/3C_Stefan said:
Looking at the altered design of the crank mains on a 120 I would guess they had some issues with them too during their early trials
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The altered main bearings of the 120? triples are more a concession to ever-increasing noise regulations than anything else.  Nothing wrong with the original design.  In fact, using main bearings with different specs such as wider rollers, plastic cage and a roller or 2 more can quieten the crank considerably! 

Much the same applies to the different primary cover and clutch design of the MkII as opposed to the early MkI version.  Laverda went to great lengths reducing mechanical engine noise as well as intake and exhaust emission noise in order to get their models legalised around the world, and most of us go out and fit the loudest pipes we can get our hands on! :D ::)

piet
 
120 triples have pretty light primary vibrations, but very messy secondary....which was a problem in the early 70's with a lack of technologies (balance shafts, small rubber engine mounts etc.). These high frequency secondaries can cause problems with fracturing of engine mounts etc. (not such a problem on 120 two strokes, due to the more frequent firing).

The 180 triple has pretty noticeable primary vibrations (as all 180 owners know  ::) ), but has a much more benign secondary vibration. Might make your fingers buzz, but it is a low frequency vibe, so less damaging.

It was a simple and clever solution to what was a difficult problem, at the time.

The eventual solution to the 120 vibes (very small rubber mounts - like a tiny version of car engine mounts), was a great solution, with one proviso - the engine could no longer help keep the frame a bit more rigid. This meant the need for a new frame that was designed for rubber engine mounts. That's why the RGS handles better than a Jota 120. The RGS frame is much more rigid. The Jota 120 was a bit of a hybrid and doesn't handle that well compared to an RGS or a series 2 180, for that matter. Not a problem poodling around the streets, but take one on a track day and  :o

P
 
nealebms said:
Laverda probably had the technology to make the 180 a crossplane crank but the flat plane crank they used was cheaper to produce.
Neale
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A crank that's built up by pressing the components together can be assembled with any phase difference between crank pins. There are no splines or keys in the centre pressed-togehter joints, so it's no more difficult or expensive to build a flat plane (180), a 120, or a cross-plane crank. The Laverda factory was quite capable of assembling the crank in any phase configuration they wanted to. Kudos to Kevin Ash for retracting his earlier incorrect statement that it was due to tooling limitations.

As Grant mentioned earlier, the 180 crank was initially chosen to eliminate the vibration due the rocking couple that's inherent in the 120 phasing.

It would be interesting to know exactly how the Yamaha triple crank is phased. If it's a true cross-plane, I'd guess that the middle crank pin is at 90 deg, but are the outer ones 180 or 360 deg apart?

Cheers,
Cam
 
so it's no more difficult or expensive to build a flat plane (180), a 120, or a cross-plane crank
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True, but don't forget you need to change the phasing of the cams, Cam (well, someone had to say it  :-*).

OK....exit stage right now  (bolt)

Pete
p.s. I bent my brain trying to figure a 3 cylinder cross plane crank phase. I think Laverda knew what they were doing, as the 180 flat plane has the least uneven firing gaps....
P
 
poffer said:
... as the 180 flat plane has the least uneven firing gaps....
P
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I think you're a wee bit incorrect there Pete, unless you're referring to a 4 cylinder engine - in which case you're totally non-incorrect  :D.
With a 3-cylinder engine, the 120 crank has the least uneven firing gaps. In fact, it's as even as it can get. All firing impulses are 240 deg apart.

A full cycle on a 4-stroke engine is 2 revs, or 720 degrees.

A 3-cylinder 180 phased crank firing impulses are: 0, 180, 360, (misses 540 because it's not 4 cylinders), then back to the start at 720. The gaps between firing impulses are therefore 180, 180 and 360. It's the same as a 4-cylinder engine that's misfiring on cylinder #3.

A 3-cylinder 120 phased crank firing impulses are: 0, 240, 480, then back to the beginning at 720. The gaps between firing impulses are therefore 240, 240 and 240 (same as a 3-cylinder radial engine).

Cheers,
Cam
 
An RGS frame may be stronger than a 180 or 120 Jota frame but that doesn't necessarily mean the bike handles better.
Steering geometry is different, as is wheelbase, swingarm length, engine position and so on.

Having owned and ridden 180s, 120 Jota and Corsas I can't say the RGS is a better handler.
Took me a while to gel with the 120 Jota handling, but the biggest realisation was the lesser engine braking from a 120 motor. Once I sussed that it handled every bit as good as my 180s ever did. Which was better than my first Corsa ever did.

Horses for courses, riding style, expectations and so on I guess.
YMMV.
 
I think you're a wee bit incorrect there Pete, unless you're referring to a 4 cylinder engine - in which case you're totally non-incorrect  .
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Hi Cam - I guess I wasn't too clear - I meant least uneven of cross plane or flat plane triple.

Pete
 
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