Triumphrat

worldspeaker · 06-06-2007

Just a quick question. What is the seat of the pants difference between a Vertical twin and a v twin. Does a v twin have a lower center of gravity? Can you compare the two?

Also what are the advantages of a chain drive. I hear all the advantages of the other drive systems but have not heard any for the chain drive.

Thanks for your insight.

Dave

sponger · 06-06-2007

I'm no mechanic and not a gearhead, so I don't know the answer for the vtwin and vertical twin thing. Seems the vertical twin is usually capable of producing more power than a comparable sized vtwin though.

Chains seem to be advantageous for big, powerful, engines. Seems all the highly modified big hp bikes I see have chain drives. Maybe they are cheaper to manufacture as well, particularly to shaft drives? Personally I prefer the low maintenance, quietness and smoothness of a belt or shaft drive (seems a little clunky sometimes), but I don't ride big hp machines. Love the belt drive Harleys.

Diego · 06-06-2007

Just from a physics standpoint, there is no difference in the power that could be delivered from the two engine types if the displacements were the same, fuel and exhaust systems (including valves, porting, etc.) were comparable, etc.

In theory, a V-twin could have a lower center of gravity, but that's not a guarantee that a finished design would, necessarily; and it doesn't relate to power.

Now, from a practical standpoint, I once read that it's easier to design a vertical parallel twin to handle sustained power from a cooling standpoint than it is for a v-twin, because the back cylinder of the vee won't receive as good air flow and must therefore be babied a bit...but I don't really know if the fellow knew what he was talking about, and in the coming era of all-liquid-cooled engines, it won't be a factor anyway.

As for drive methods, I agree with Sponger that Harleys' belt drive is very nice, and that one of the big reasons chains are still around is that they are cheaper than the other two methods.

Chains are also a lot less massive than shafts for a given power handling capability, and are less subject to certain kinds of physical damage than belts. Plus, modern construction techniques make chains sturdier and lower maintenance than they were in the "olden days."

trotskyite · 06-07-2007

Well, if you set it up like Ducati does, then you can actually get a much more progressive torque curve. Thats why Ducatis were spanking the 4 cylinder Japanese competition for so long, they could power out of a turn much, much earlier without upsetting the bike. They certainly weren't putting out more power, but they delivered it in a smarter way.

trotskyite · 06-07-2007

Chains are cheap, simple to work on, and strong. Shaft drives weigh more. When you are talking about building a truly fast bike, weight is your number one issue. When you are talking about a manufacturer building a bike for under $10k a $20 chain that works wonderfully, its a no brainer. At the end of the day Triumph has its share of bean counters happy to shave a little here or there in the pursuit of profit margins.

CommandoRdster · 06-07-2007

It was once pointed out to me (by Kevin Cameron) that a vertical twin is,in effect,only a very narrow angle V twin, and a boxer twin(ala BMW)is nothing but a very wide angle V twin. Ducati-90 degree,Harley-45deg, Triumph- 0deg, BMW-180deg. Power production is a factor of bore and stroke,breathing,and cam timing,not really angle of the cylinders.

However,power delivery is affected by the offset firing order of the Harley engine, which has a 270 degree firing order(as does the America,Speedmaster,and Scrambler,along with some of the Japanese V twins,and the Dreer Norton). This means that you get two close together power strokes,then a relatively long time between two more close power strokes. This is a big boon in low traction situations, and is the official reason that Harley has dominated dirt track racing for so many years.(The AMA rule book is the real reason,but that is for another post)

I am a Harley owner,and it might interest some of you to know that the rear cylinder actually runs a few degrees hotter than the front!

It's my opinion that the only reason that Harley developed a belt drive for their big cruisers,back in the late 70s, is that the parent company,AMF, would not fund what would have necessitated a complete re-design of their power-plant to accommodate a shaft drive.They came up with so many reasons(excuses) that a belt was better than a shaft,that now that they can afford a shaft,they are not about to eat their words,and build one. Now, of course, if you have a big cruiser,and you don't have a belt,you're just not cool. For a big cruiser,or touring bike,a shaft is better in every way. For almost every thing else,a chain is the way to go. It will stand up to dirt,rocks,and mis-alignment(read:ham fisted owner abuse)much better than a belt.
For a pampered bike, a belt is a lot less maintenance than a chain.
:chug:
Cheers!
Bruce

1962gypsy · 06-07-2007

Some good replies here. I believe the V design lends itself to really good low end "grunt", but not necessarily high hp numbers. The torque curve is where we live in the real world anyway. A good illustration I once heard was that in using boxing as an illustration, hp would be how fast you can hit and torque would be how hard you can hit. I don't believe a big twin Harley has much if any hp advantage over my 790 cc's but it produces quite a bit more torque. The R3 has both in spades.

JhuFrank · 06-07-2007

Quote:

On 2007-06-07 06:58, 1962gypsy wrote:
Some good replies here. I believe the V design lends itself to really good low end "grunt", but not necessarily high hp numbers. The torque curve is where we live in the real world anyway. A good illustration I once heard was that in using boxing as an illustration, hp would be how fast you can hit and torque would be how hard you can hit. I don't believe a big twin Harley has much if any hp advantage over my 790 cc's but it produces quite a bit more torque. The R3 has both in spades.

Oh, that's because the R3 has the bestest, mostest and fastest engine design, the beautiful TRIPLE!!! Sorry, I will scuttle back to our forum... :razz: :wink:

sweatmachine · 06-07-2007

Quote:

On 2007-06-07 03:09, CommandoRdster wrote:

However,power delivery is affected by the offset firing order of the Harley engine, which has a 270 degree firing Cheers!
Bruce

You're wrong, Harley uses a 45 degree V twin, which would be 315 degrees, not 270.

360-45 = 315.

Normandy · 06-07-2007

The rear cyl on my 76 shovelhead was hot enough to run a heat range cooler spark plug . I also turned the horn into the wind to scoop air to the back barrel.