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so i had a general question.. what is it that gives harleys their powerfully low vibrations.. and how can you tell if an enjine will sound that way..
i figured that the rpm at which the max tourque was would indicate what kind of general vibrations you got from the enjine. like engines with max tourque at 2500 or 3000 rpm mad that classic harley sound/vibration. and that ducatis with their 6000 rpm max torque had a higher, whine-ier sound/vibration.
but 2 things throw me off.. out of a ducati you never seem to get that low vibration even when the enjine is operating at 2500 rpm. and the VRSC harleys have a 7000 rpm max torque, but as far as i know they still have that classic harley sound/vibration.. so what exactly is it that give that trait to an engine? would i need to look at a whole torque chart in order to get a true feeling for the "sound" of an engine.
i do understand that the exhaust has some to do with the actual sound, but i am also considering the vibration transmitted thru the frame.

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The way the bike is built and the frame design play a big part of it. THe engine size and construction is just as big. But the exhaust has the most affect on sound




JWF

Harley's get their "trademark" sound from the angle of their cylinders and their single-crankpin design. From there the exhaust is tuned to the desired level of sound output, and a lot of Harley owners turn down their idle speed to get that loping sound, even though it usually results in dangerously low oil pressure.

ZooTech wrote:Harley's get their "trademark" sound from the angle of their cylinders and their single-crankpin design. From there the exhaust is tuned to the desired level of sound output, and a lot of Harley owners turn down their idle speed to get that loping sound, even though it usually results in dangerously low oil pressure.

Potato, potato, potato...That trademark?

rofls... Harley shouldn't go in the same sentance with power *
They ARE a very nice ride though. And a harley with a set of pipes is a beautiful thing.

*except the VRSC line and the screamin' eagle bikes. Or if you're one of those crazy guys that has their bike jacked up something fierce.

The potato potato sound of a harley comes from the angle of the cylinders and the single pin crank like Zoo had mentioned.

A harleys cylinders are only angled 45* apart. for comparison a Ducatis cylinders are 90* apart and run a double pin crank. Theses different characteristics create different harmonics in the exhaust creating a different sound.

A single pin crank has both connecting rods on the same journal which makes both pistons go up and down at nearly the same time (think 2 up 2 down).

A double pin crank has the connecting rods on different journals on opposite sides of the crank. This makes the pistons work opposite each other. Basically when 1 is going up the other is going down.

ah ha! ok, that makes sence then about the single pin crank.
yay im learning !!

Here's a good article on why Harleys sound like they do and about the power and torque curves of these engines.

http://motorcyclecruiser.com/tech/vtwinbasic/

How stuff works is awesome, here is the combination of all of these replys


http://auto.howstuffworks.com/question325.htm



JWF

if you ask me, 2 stroke automatic engines which have aftermarket parts are the most beautifull sounding engine ever.