Talk:V-twin

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Contents 1 Torque reaction due to longitudinal mounting 2 Transverse vs Longitudinal 3 Cooling 4 True V-twin vs V-2

[edit] Torque reaction due to longitudinal mounting

"...slight disadvantage of causing a torque reaction that tends to lean the motorcycle slightly to one side..."

Any reference for this? Any idea how big this torque is, or how much of a "disadvantage" it is?

This should also be an issue for boxers and big flat sixes like Goldwings and Valkyries, right? The new Triumph Rocket III at 2300cc should be the worst? Any reports of riders loosing countrol or complaining about this issue?

Didn't some cable show actually warn about the "dangers" of longitudinally mounted v-twins? Is this just hype from Harley buffs for why that configuration is superior? -AndrewDressel 01:29, 12 October 2006 (UTC)

- It appears to match almost word for word the claim made on http://www.hogsandparts.com/history/vtwinhistory.htm, a Harley specific site.

- It is also matches word for word http://experts.about.com/e/v/v/V-twin.htm and http://vtwin.quickseek.com/. Hmmm, who's copying whom?

After all, it is only the crankshaft and some fraction of the connecting arms that rotates, right? That accounts for only a fraction of the total weight of the bike and has a pretty small radius. - AndrewDressel 04:19, 12 October 2006 (UTC)

Personal riding experience bears out a torque reaction, especially under hard acceleration, when riding longitudinal or "flying" v-twins, as well as older BMW flat twins and some inline bikes where the cylinders are in line with the frame. (I don't know about newer BMWs.) It is quite noticeable at times but minor in that I can't imagine it would ever cause any but a very new rider to lose control. It can be a bit startling the first few times it is experienced, and makes the bike feel much less refined. If you were doing quarter mile runs, it might also get quite distracting and diminish your performance.

Many motorcycle reviews mention whether or not torque reaction is present in a given bike.

Goldwings and many other bikes have corrected for torque reaction by rotating the transmission gears and/or the balance and drive shafts opposite that of the crankshaft so that there is approximately equal mass turning clockwise and counterclockwise at any time, thereby physically canceling the effect.

An excerpt from a review of the Triumph Rocket: "The 120-degree crank spins one way, while the balance, transmission-input and final-drive shafts all spin the other, mostly counteracting vibration and torque reaction. In neutral, you can feel the bike try to roll slightly to the right with each throttle blip, but the effect is not nearly as strong as a BMW's."

Google "motorcycle torque reaction" if you'd like more information; there's a lot out there. If you want an extreme example, there are bikes powered by small block Chevy 350 V-8s (Boss Hoss Cycles) that have scads of torque reaction, and I've seen a video clip on the net that demonstrates it quite clearly. I've also seen one twist like that in person.

Hope this helps. Unfocused 03:19, 1 November 2006 (UTC)

Very much. In fact, I pasted your entire 3rd paragraph into the article. I hope you don't mind. I actually have a Guzzi, and while I can notice when stopped at a light, it hasn't been a factor for me while riding. Perhaps I'm too casual. -AndrewDressel 19:53, 1 November 2006 (UTC)

Its quite normal that the article matches word for word sites using GFDL Wikipedia content. For the other site well I don't know but I think a lot people have written something like "A molecule of water is made of two atoms of hydrogen and one atom of oxygen." or "Bob Dylan is a famous songwriter" without copying each other. Ericd 06:01, 1 November 2006 (UTC)

So long as it is not just propagating a myth. -AndrewDressel 19:53, 1 November 2006 (UTC)

[edit] Transverse vs Longitudinal

On 18 November 2006 at 14:58 User 151.205.153.207 swapped transverse for longitudinal and vica versa throughout the article. Specifically, Harley Davidson's orientation is now called longitudinal, and Moto Guzzi is now called transverse. These terms appear to be poorly defined.

On the one hand dictionary.com defines 'transverse' as "(of an automotive engine) mounted with the crankshaft oriented sideways".

On the other hand, BMW, on its web site, refers to its boxer as having "transversely mounted cylinders".

Perhaps the confusion comes from the terms transverse and longitudinal being used to describe either the crankshaft orientation or, contradictorily, the cylinder orientation (the latter only making sense in the case of v-twins and boxers, I guess).

So, a Harley's crankshaft is mounted transversely, and its cylinders are mounted longitudinally; and a Moto Guzzi's and a BMW boxer's crankshaft is mounted longitudinally, and its cylinders are mounted transversely.

Searching with google for any manufacturer and the words transverse or longitudinal returns thousands of hits. There does not appear to be a reliable convention for whether the terms transverse and longitudinal by themselves refer to the crankshaft or the cylinder orientation in motorcycles. Does anyone have a definitive source this article can reference?

In the meantime, I've added a clarification at the beginning of the section. -AndrewDressel 17:54, 20 November 2006 (UTC)

On 10:14, 24 December 2006, user 213.216.199.30 said "Orientations - Changed the description to use crankshaft orientation as now it is in line with orientation mentioned in Honda ST series wiki pages" and went on to change the article to read "The terms longitudinal and transverse are used to refer to the crankshaft orientation. A common mistake with V-2 engines is to refer to the cylinder orientation (as mentioned on BMW's web site). However referring to the crankshaft gives a correct method to engine orientations as it gives the same orientation for all V-engine types like V-2, V-4 (which would be difficult to describe with cylinder orientation) and V-8."

Sounds good, but are there any confirming references?-AndrewDressel 13:28, 24 December 2006 (UTC)

None that I know of. You had the definition from dictionary.com. I have seen no better definitions. 213.216.199.30 09:43, 31 December 2006 (UTC)

I know that this is a very common issue to fight about and make a mistake. Think about single cylinder engines. How do you tell if they are transverse or longitudinal. By crankshaft. Think about Dodge Tomahawk with V10, definetly longitudinal. Remove two cylinders. Boss Hoss V8, longitudinal. Remove two. Nonexisting V6, must be longitudinal. Remove two, Honda ST V4, this is a difficult one, but longitudinal accoring to wiki and longitudinal according to this reasoning written here. Then remove two cylinders. Moto Guzzi. Did we turn the engine while removing those cylinders? No, so this must be longitudinal as well. 213.216.199.30 09:43, 31 December 2006 (UTC)

[edit] Cooling

Thanks Jeff for the reference, but it actually confirms my suspicion. It is comparing flat twins to transverse mounted v-twins, not the longitudinal V-twin of which the flat twin is being described as the ""logical alternative". I would argue that most longitudinal V-twins run nearly as cool as their 180° opposed cousins. I'll look for a source. -AndrewDressel 04:49, 20 February 2007 (UTC)

Well, it looks like we've gotten that straightened out. -AndrewDressel 16:40, 20 February 2007 (UTC)

[edit] True V-twin vs V-2

The Complete Guide to Motorcycle Mechanics, a text book from the Motorcycle Mechanics Institute (1984, Prentice-Hall, Inc., ISBN 0-13-160549-6) does not make this distinction. See page 61. Also, parallel-twins don't share a crank pin, and yet they are not called "Parallel-2s." Unless someone can come up with a good citation for this distinction, I think it should be struck. -- Pi3832 04:54, 3 March 2007 (UTC)