G oog le BadWeB | Login/out | Topics | Search | Custodians | Register | Edit Profile

Buell Forum » XBoard » Buell XBoard Archives » Archive through October 21, 2004 » XB vs. 2005 Speed3 « Previous Next »

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

Kbbeckius
Posted on Saturday, October 09, 2004 - 05:31 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I still haven't decided which bike I'm going to buy. I've been leaning toward the Triumph, but we'll see when I can actually ride it (March/April). Anyway, I thought I'd try to analyze the dimensional differences, since everyone says the Buell is so small. I discovered something rather interesting, which I confirmed by looking at their specs, they have the same steering geometry. If the Buell actually had a fuel tank where the airbox is I think things might look very similar.





Thx Brad
Top of pagePrevious messageNext messageBottom of page Link to this message

Anonymous
Posted on Saturday, October 09, 2004 - 05:44 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

If the Triumph actually has the same steering geometry as the Buell, watch out! They don't have the other necessary stuff to go with it for stability.

From a choice standpoint, the Triumph will have more horsepower, but the Buell will trounce it in chassis performance. Make your choice and have fun!
Top of pagePrevious messageNext messageBottom of page Link to this message

Kbbeckius
Posted on Saturday, October 09, 2004 - 06:15 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Ok, here's the bike's specs. The steering geometry isn't identical but very close.

--------------Buell-------Triumph
--------------XB12S-----Speed 3
Rake--------21deg------23.5deg
Trail--------83mm-------84mm
Wheelbase---52"-------56.2"
Dry weight-395lbs-----416lbs
HP---------103@6800---128@9100
TQ---------84@6000----71@5100

They both run the same size tires
120/70/17 front 180/55/17 rear

http://www.buell.com/en_us/bikes_gear/lightning/xb12s/specs/12s_specs.asp
http://www.triumph.co.uk/uk/788.aspx

Thx Brad

(Message edited by kbbeckius on October 09, 2004)
Top of pagePrevious messageNext messageBottom of page Link to this message

Xb9er
Posted on Sunday, October 10, 2004 - 12:46 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

You just got advice from, shall we say, a highly placed Buell representative. Take it seriously before you make a choice.
Mike.
Top of pagePrevious messageNext messageBottom of page Link to this message

Gschuette
Posted on Sunday, October 10, 2004 - 03:08 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Ok who the is anony? I keep hearing he's a big wig but who. I must know.
Top of pagePrevious messageNext messageBottom of page Link to this message

Ingemar
Posted on Sunday, October 10, 2004 - 04:10 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Someone made me believe it *could be* Mr. Buell himself. I guess most of us will never know for sure 'cos we have no way to check (board admins and custodians can though).

I won't think a speed3 will outrun an xb12. It has higher hp on the crank, minus 15% makes 109hp at the rw. The 12 has like 95 rwhp. Taken the higher revs and the lower torque, heavier weight, (and I think slightly higher gearing) .... ah well. Point made.
Top of pagePrevious messageNext messageBottom of page Link to this message

Trenchtractor
Posted on Sunday, October 10, 2004 - 07:07 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

My 12 in stock trim made 86.2RWHP and 71.5 ft-lbs on a Dynojet dyno. It's an Aussie bike though, and our fuel is 5h1te.

Those overlays really put things into perspective, eh? But that last pic you did is just plain WRONG!!!

Mr Annon is right about the geometry/set-up thing, too... The Buell has lots of issues that stem from the engine being sportster based that hinder turn in but aid stability, so aggressive geometry is required... But the Speed Tripple engine won't have the same characteristics... So if it were to have a short wheel base and streering like the XB, it would be one hell of a ride (while it lasted)...

That extra rake, trail and wheelbase should slow things down a tad, though. I'd be interested to hear your opinions on a back to back test ride...

I rode a Zed Thou after purchasing my 12 and was not impressed at all. I really don't miss having to rev the absolute crap out of a jap bike any more...

I AM TRUELY V-TWIN LAZY!!!
Top of pagePrevious messageNext messageBottom of page Link to this message

Johncr250
Posted on Sunday, October 10, 2004 - 10:21 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

"I won't think a speed3 will outrun an xb12."

I almost fell outa my chair when i heard that!

I speed triple will run away and hide from an XB12 in a staight line.

Thanks for the laugh!
Top of pagePrevious messageNext messageBottom of page Link to this message

Nick
Posted on Sunday, October 10, 2004 - 10:33 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I have to agree with John. I have had two Cheese Nipples (884 and 955i) and I would say the 955i would have left it on the straight. When my XB eventually arrives (Buell sent wrong model to UK) I will let you know on the handling front.
Top of pagePrevious messageNext messageBottom of page Link to this message

Ingemar
Posted on Sunday, October 10, 2004 - 11:00 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Thanks for the laugh!

My pleasure!

I speed triple will run away and hide from an XB12 in a staight line.

And he better hide before some turns show up! ; )

Seriously now. The numbers for both bikes:

Speed Triple ('02)
quarter mile: 11.04 sec @ 123.8 mph
60-80 mph: 3.77 sec
80-100 mph: 4.49 sec

XB12R Firebolt ('03)
Quarter mile: 11.43 sec @ 117.5 mph
60-80 mph: 3.98
80-100 mph: 4.45

I don't know if the speed tripple for 2004/2005 delivers more power than the 2002 model.

Nick, the 955i is not a tripple. Big difference. ~30hp if I'm not mistaken.

John, looking at the performance numbers I posted from sportrider.com, it definitely doesn't outrun an xb12, so why exactly are you laughing again?

I'm sure the triumph is a really fun bike to ride though.
Top of pagePrevious messageNext messageBottom of page Link to this message

Johncr250
Posted on Sunday, October 10, 2004 - 11:30 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Ingemar,

Its obvious that you`ve never ridden a speed triple. Thay don`t handle as well as the XB, but motor wise its no comparison. Not sure where you got your number`s from.

Take one for a ride and see.

I`m going to go ride my Buell.
Top of pagePrevious messageNext messageBottom of page Link to this message

Ingemar
Posted on Sunday, October 10, 2004 - 11:35 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Its obvious that you`ve never ridden a speed triple.

That's right. Never even sat on one.

Thay don`t handle as well as the XB, but motor wise its no comparison. Not sure where you got your number`s from.

Like I said, from sportrider.com. Those numbers don't lie. Because of the revvier engine, I'd suppose the *feel* a lot quicker.

Take one for a ride and see.
No thanks.

I`m going to go ride my Buell.
I just came back from my days' ride! Enjoy en ride safe man!
Top of pagePrevious messageNext messageBottom of page Link to this message

Shotgun
Posted on Sunday, October 10, 2004 - 12:22 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

2005 Speed Triple has a new engine, 1050cc, new gearbox and clutch and a completely new chassis. Torque is up to 78 ft #s. The ride position is far different from the XB's, less aggressive.
Many exBuellers in our area are now riding Triumph Triples for their comfort, reliability, chain drive and cost competitive with Buell.
I love my M2. I had an XB but could not ride it in comfort. The Speed Triple feels like my M2 when I sit on it. The 2005 style is hot. I have my deposit down on this one, due to arrive March 2005:
Top of pagePrevious messageNext messageBottom of page Link to this message

Bubabuell
Posted on Sunday, October 10, 2004 - 01:40 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I own both - 2003 XB12S and 1999 speed triple. The triple is much faster.
Top of pagePrevious messageNext messageBottom of page Link to this message

Kbbeckius
Posted on Sunday, October 10, 2004 - 02:55 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I was hoping for a little more positive comments, but if you want to see the other side look here
http://www.triumphrat.net/modules.php?op=modload&name=Forum&file=viewtopic&topic =11824&forum=19
really want to see something disturbing?
http://www.ducatierie.com/triumphrace.htm
Don't know if it's true or what, but an interesting story, would be different if it wasn't a straight line, a R1 would kill em all in a straight line.

I have demo ridden both an '04 S3 and an '04 XB12S, and until I saw the '05 I was going with the Buell. They "feel" about the same as far as quickness goes, sure the S3 has more top end, but I don't plan on riding at 130+ mph anyway. The "feel" has to do with torque, which both bikes have an equal amount of, I have also demo'd a FZ1 and I thought it "felt" slow, but look down at the speedo and you're hauling a**!! It goes back to the argument that you can feel torque but not horsepower.

I like torque

Thx Brad
Top of pagePrevious messageNext messageBottom of page Link to this message

Ingemar
Posted on Sunday, October 10, 2004 - 03:10 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

It wasn't my intension to give a negative impression of the tripples. I've always really liked the looks of triumphs, I have just never ridden one so I can't really comment on handling etc. Al that I have said is based on what I have read. The numbers would suggest they are equally fast to me, but if guys who own both say that's not the case then I eat my words (AGAIN?!?!) and if those same guys say a buell handles better, then who are we to argue with them ?
Top of pagePrevious messageNext messageBottom of page Link to this message

Nick
Posted on Monday, October 11, 2004 - 08:35 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Ingemar,

The 955i refers to a motor Triumph built. I think you're getting confused with the Daytona. Triumph built a Daytona 955i and then a Speed Triple 955i. Thus I was clearly defining the difference between the 884(i) and 955i version of the speed triple. But on this occasion I'll let you off as you seem to be getting some stick!
Top of pagePrevious messageNext messageBottom of page Link to this message

Thunderbolt
Posted on Monday, October 11, 2004 - 09:09 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

ingemar, first off, all triumph 955i's are 3 cylinder bikes ('triples'). you seemed to be confused about that (as well as a bunch of other stuff).

and, yes, the '05 speed 3 from triumph has more power than the '02~'04. it has more peak power as well as a broader power band. they increased stroke to bump displacement to 1050cc (from 955cc) and changed the cylinder material to maintain the same redline (higher piston speed now similar to the daytona). on a dyno or on a strip, it would destroy any stock buell. that's fact, as far as handling goes, well that's just way too subjective to argue about. suffice it to say that many would disagree that a buell has any advatage over an '04 speed 3, let alone the new (and never ridden by the public) '05 with improved suspension. and as far as the new speed 3's steering geometry being the 'same'...well that is completely ridiculous there are HUGE diffences in those geometry numbers.

now, at the risk of opening up a can of worms, NO, Brad, you can not 'feel' engine torque. what you 'feel' is acceleration and we all know that f=ma. well the engine provides the f there, and f is directly proportional to (POWER)/(GROUND SPEED) at any given time. NOT ENGINE TORQUE! when a bike has 'a lot' of torque, it almost always means that it has 'a lot' of low end power, or that it puts out more power AT LOWER GROUND SPEEDS. so, yes, they can produce a lot of f and hence a, which is what you feel. BUT, remember that it is the engines POWER at any one GROUND SPEED that determines f and hence a (taking into acct a constant m), neglecting driveline losses of course. realize also that gearing comes into play because gearing determines rpm vs ground speed and power depends on rpm. BOTTOM LINE: if you want to know how much a you are going to 'feel', you need to know your m, your speed, and your rear wheel power at that speed in the gear you are in. not engine torque!
Top of pagePrevious messageNext messageBottom of page Link to this message

Americanrice
Posted on Monday, October 11, 2004 - 09:14 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

All the forum opinions in the world don't mean anything, if you don't test ride them both before you buy one you are just robbing yourself!
Top of pagePrevious messageNext messageBottom of page Link to this message

Tbs_stunta
Posted on Monday, October 11, 2004 - 11:37 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Kbbeckius, see what I mean. Go to a Triumph site and the S3 is king, go to a Buell site and Buells are king. In the end both will provide a similar thrill although both bikes will have very different personalities. I still think the Buell will corner better, the question is whether you are a good enough rider to exploit the differences. Triumph doens't make crap handling bikes so if they tightened up the 05's geometry the bike will still feel nice and composed.

Luckily both are available for test rides so you can draw your own conclusions. You can't go wrong on either, but one will definitely speak to you.
Top of pagePrevious messageNext messageBottom of page Link to this message

Ingemar
Posted on Monday, October 11, 2004 - 11:46 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

But on this occasion I'll let you off as you seem to be getting some stick!

What does that mean? I'm serious, english is not my native language and I'm just not familiar with that phrase. Did I say something wrong?

And thanx for clearing up the difference between the daytona 955i and the tripple. That was my confusion indeed.

.. and we all know that f=ma.

Really?
Top of pagePrevious messageNext messageBottom of page Link to this message

Glitch
Posted on Monday, October 11, 2004 - 11:48 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Don't worry about it Ingemar.
I might give you a hard time (stick) if this was a speed triple owners site; )
Top of pagePrevious messageNext messageBottom of page Link to this message

Fullpower
Posted on Monday, October 11, 2004 - 02:53 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

both fine motorcycles. you need one of each, the REAL question is which one to buy FIRST. I would go alphabetically.
Top of pagePrevious messageNext messageBottom of page Link to this message

Kbbeckius
Posted on Monday, October 11, 2004 - 07:27 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Thunderbolt
I didn't really plan on getting technical with this but here goes...The "butt dyno" isn't an accurate judge of speed, ride an XB then an FZ1. Which "feels" faster? Look down at the speedo, which is faster? Given the appropriate RPM, I could(in theory) have an engine making 1,000,000 HP with 10ft/lbs of torque. Torque is real, horsepower is a mathematical construct, a function of torque and RPM. Dynos don't measure horsepower do they!

I somewhat disagree with your opinion, while your body is not a very good accelerometer, it is good however, at detecting changes in the rate of acceleration, i.e. slamming on the brakes or hammering the throttle. Why? It has to do with the way your inner ear detects motion and the way your internal organs move within your body cavity. Basically, how G forces effect the body. Gradual acceleration also provides these effects but, your body doesn't detect this as easily.

I like vehicles that "feel" fast (I don't really see the point of going 200+ MPH, not that I wouldn't do it.. ; )), this includes two-strokes, nitrous oxide, and turbocharged vehicles, Why? Non-linear power delivery, something that gives the sensation of speed. These vehicles generate a big torque spike, causing the rate of acceleration to change quickly, and usually they go fast too..

This is further explained the best here..
http://www.vettenet.org/torquehp.html
The Case For Torque
Now, what does all this mean in carland?

First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

In contrast to a torque curve (and the matching push back into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.

You don't believe all this?

Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :-)

and also here...
http://www.westechperformance.com/pages/Tech_Library/Understanding/hpvstq.html#A nchor-Octane-686
http://www.herberts.org/wayne/valk/valktorque.htm
http://www.corral.net/projects/subzero/gtech.html
http://phors.locost7.info/phors03.htm
http://phors.locost7.info/phors06.htm


Thx Brad

: ) yes, you stand corrected

Buells aren't "slow" (by superbike standards) because they don't make enough torque, it's because they don't make the RPM(HP)

(Message edited by kbbeckius on October 11, 2004)
Top of pagePrevious messageNext messageBottom of page Link to this message

Kbbeckius
Posted on Tuesday, October 12, 2004 - 07:49 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Basically...
Torque=Acceleration
Horsepower=Speed
I think this page I just found actually explains it best
http://motorcycleinfo.calsci.com/Horsepower.html

Thx Brad
Top of pagePrevious messageNext messageBottom of page Link to this message

Jeremyh
Posted on Tuesday, October 12, 2004 - 10:52 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

i like the belt tensioner pulley on that chain drive XBspeed3
Top of pagePrevious messageNext messageBottom of page Link to this message

Thunderbolt
Posted on Tuesday, October 12, 2004 - 11:06 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

well, i guess i knew i was opening up a can of worms...

Brad, i wish i had the time and energy to explain this whole thing in full detail, but i don't.

you are very confused. and incorrect.

take your analysis of the human body not being an accelerometer but rather how it reacts to G forces. ummm, newflash: G forces are a measure of ACCELERATION. Things that meter G forces are by definition ACCELEROMETERS.

i have seen that 'vettenet' article before (it's been around for years). i would describe it as misleading at best. take the statement:

"300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm."

While technically this is true, it is misleading. notice that this is EXACTLY what i said in my post above. it's POWER/(GROUND SPEED) that determines acceleration. the key is 'in the same gear'. if your rpm is doubled in the same gear then so is your ground speed (assuming no tire or clutch slippage). this example would be much better if he changed gearing so that in car2 you are putting out 4,000rpm power at the same ground speed car1 is putting out 2,000 rpm power. the two cars would have the same engine torque at the same ground speed, but car2 would have twice the acceleration because it would have twice the power. think about that. think of how the change of gearing would effect acceleration and why (hint: think mechanical advantage).

the last link you refer to (motorcycleinfo) looks much more accurate (though i have to admit i only gave it a passing look, as i find reading about things i already understand boring). i think you need to re-read that page and realize that the author makes a very important change in terms about half way through. he goes from talking about ENGINE torque to talking about REAR WHEEL torque. i think you're confusing the two. rear wheel torque is proportional to (guess what) ground speed and engine POWER (assuming constant size rear-wheel). if you know your rear wheel diameter, engine power and ground speed you can calculate your rear wheel torque. if you know only your rear wheel diameter, ground speed and engine torque, you can not calculate your rear wheel torque. because engine torque w/out engine rpm is USELESS.

you brought up an interesting example of a 'fantasy' motor that produces 1,000,000 hp with very low levels of torque. i love this example and your intuition to think that understanding this hp/torque debate at it's extreme is important. you have to understand this:

if you were to put this motor in one buell (called bike1) and leave the standard 100hp (for this debate) engine in another buell (called bike2) and gear bike1 so that it is putting out 1,000,000hp at the same ground speed as when bike2 is putting out 100hp, guess how much faster bike1 will be accelerating than bike2? we are going to need more of your stipulation juice to keep bike1's front tire from becoming the world's largest fastest mouse trap and from keeping the belt and rear tire etc from vaporizing, but it would accelerate exactly (1,000,000/100) times as fast (that's 10,000 times as fast!). how much torque each engine is putting out is completely irrevalent. that is the crux of the whole thing.

re-read the motorcycleinfo site, and keep tossing around in your mind the 1,000,000hp example above and i bet you'll be able to realize that engine torque is irrevalent! you have an opportuntity to really learn a neat new thing--good luck!
Top of pagePrevious messageNext messageBottom of page Link to this message

Thunderbolt
Posted on Tuesday, October 12, 2004 - 11:53 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

important foot note to my bike1/bike2 example above: both bike's engines have the same mass.
Top of pagePrevious messageNext messageBottom of page Link to this message

Kbbeckius
Posted on Tuesday, October 12, 2004 - 11:54 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Can you tell the difference between .6G and .8G? Probably not. But you can tell if a vehicles rate of acceleration changed by .2G quickly. That was my point. It's easy to tell by the "butt dyno" that a vehicle's rate of acceleration has changed. Using calculus, it would be the derivative of acceleration with respect to time, it could be expressed as (ft/sec^2)/sec or ft/sec^3.

As far as gearing, it is basically a way of converting torque and horsepower at the rear wheel. As a quick example, take a 4x4 truck with a very low "granny" 1st gear, through gearing there is now much more torque available at the drive wheels, but how fast can you go in that gear? not very fast... But in an overdrive gear the vehicle can go very fast, but dependant on available engine torque will probably not be able to accelerate quickly.

Your last example is rather questionable, at what RPM? my point was that the RPM at which that would occur with 10ft/lbs of torque would be like 5 billion some RPM, not very practical

Torque is higher than HP below 5252, and lower above that. Instead of saying "I like torque" I'll just say "I like low RPM horsepower", will that satisfy you?

Thx Brad

PS-thx for hijacking the thread


(Message edited by kbbeckius on October 13, 2004)
Top of pagePrevious messageNext messageBottom of page Link to this message

Thunderbolt
Posted on Wednesday, October 13, 2004 - 12:27 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

"PS-thx for hijacking the thread "

sorry dude, what's weird is i was only trying to give you a little education, and i thought for a second you were actually going to get it. back to the regularly scheduled bs.
Top of pagePrevious messageNext messageBottom of page Link to this message

Kbbeckius
Posted on Friday, October 15, 2004 - 07:48 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Sorry, I've been out of town with work.

I do get it, we simply have different ways of looking at it.

I have been speaking in general terms so that the masses might get the gist of it all.

let's get in to some specifics then....

we have 2 bikes both have a mass of 300kg with rider, and a rear tire with a diameter of 610mm (about 24" )
torque bike1 100NM@3000RPM
torque bike2 100NM@4000RPM
(100NM is about 74ft/lbs)

in "B" gear the bikes have a total gear reduction ratio of 4.76:1
in "A" gear both bikes have a total gear reduction ratio of 3.3:1
(total gear reduction ratio is primary ratio*transmission ratio*final drive ratio)

We ignore losses due to friction, loss of traction, drivetrain slippage, wind resistance, etc...

now for some other formulae
MPH=(RPM*tire radius(in inches))/(total gear reduction*168)

F=ma or a=F/m

Rear wheel torque=engine torque*total gear reduction

Vehicle Thrust=rear wheel torque/rear wheel radius
(vehicle thrust is the force applied at the tire contact patch to the ground)

a N(Newton, unit of force)=1(kg m)/s^2

I use the Metric system because I don't like dealing with slugs, no not those slimy snail things, but the English unit of mass. Pounds are a force like the Newton, not mass like the gram.


Ok, both bikes are in gear "A"
at the torque peak bike1 will be traveling at about 60mph ((3000*12)/(3.3*168))=64.93MPH
while bike2 would be traveling at about 87MPH at it's torque peak
((4000*12)/(3.3*168)=86.58

now the rate of acceleration is equal to force/mass
so since both bikes are making 100NM, rear wheel torque is about 330NM (100NM*3.3) and vehicle thrust is 1082N (330Nm/.305m=1081.96N) therefore the bikes are both accelerating at the rate of 3.6m/s^2 (1082N/300kg=3.6m/s^2)

Ok, now lets equalize both bikes speed
bike1 is still in gear "A" while we shift bike2 into gear "B"
for bike1 at torque peak 100nm@3000RPM is 60mph and it is accelerating at 3.6m/s^2
now for bike2 at torque peak is now at 60MPH
((4000*12)/(4.76*168))=60.02MPH
but through the magic of gearing
rear wheel torque is now 476NM (100NM*4.76)and thrust is now 1561N (476Nm/.305m=1560.65N) so acceleration for bike2 at 60MPh is 5.2m/s^2 (1561Nm/300Kg=5.2m/s^2)
so though the magic of gearing bike2 is now accelerating faster than bike1 at the same speed.

In this example bike2 has more horsepower than bike1, because HP=((torque*RPM)/5252) and through the use of gearing bike2 can accelerate faster than bike1.

But because bike1 hits it's torque peak sooner it will start accelerating sooner. From a roll on bike2 will be quicker, from a stop bike1 will be initially quicker. As some of you may have noticed a Buell should be able to stay ahead of some higher horsepower bikes from a stop for a short time, until the other bike can take advantage of their increased horsepower. Gearing divides RPM and multiplies torque. Let's say one engine made 100ft/lbs@3000 and another 50ft/lbs@6000 both these engines make the same Horsepower, and through the mechanical advantage of gearing you can equalize vehicle thrust. The problem is that gearing reduces the effective RPM (and corresponding vehicle speed)that the drive wheel is capable of. Example, bikeX and bikeZ are the same except engine output, bikeZ makes 90% of it's peak torque through the RPM range of 3000 to 6000 RPM, so for a span of 3000RPM it's making 90% of peak torque, this bike has a 1:1 total gear reduction ratio. Now bikeX makes only half the torque of bikeZ, 50% of the corresponding amount generated by bikeX. However to make the same amount of torque available at the rear wheel(to accelerate the bike at the same rate) bikeX has to have a total gear of 2:1. Now the dilemma, we multiplied the torque to match bikeZ but we also divide the RPM, so bikeX has to produce that amount of torque, from 6000 to 12000 RPM a span of 6000RPM. Because, we doubled the amount of torque at the rear wheel, we also had to double the engine's RPM. If bikeX only produced torque over a 3000RPM span, at the rear wheel it would only be 1500RPM, for every 2 revolutions of the engine the tire only rotates once.

Ok, now one specifically for you Thunderbolt
Riddle me this....

We swap out the motor in bike1 with one made from unobtainium.

same bike/rider weight, same tire size, same gear "A"

But now the motor makes 100Nm of torque from 1000RPM to infinity.

Since horsepower is directly tied to RPM assuming a constant torque, as RPM rises so will horsepower. makes sense, since HP is work per time, the faster we can do the same amount of work the higher the horsepower.

Now you seem to think this bike could accelerate at an infinite rate. I disagree.

I believe the bike would accelerate at a constant rate defined thusly,
Rear wheel torque=engine torque*total gear reduction
so rear wheel torque=330Nm (100Nm*3.3)
and vehicle thrust=1082N (330Nm/.305m=1081.96N)
therefore a=F/m=3.6m/s^2 (1082N/300kg=3.6m/s^2)

But this bike is capable of accelerating at a rate of 3.6m/s^2 to an infinite RPM and therefore an infinite speed. Speed is related to Horsepower, both increase in relationship to RPM. Why do you think those top speed formulas rely on horsepower?

Thx Brad

PS: I've tried to make this as coherant as possible, and reread it several times, but I've bee awake for over 24hrs now...
Top of pagePrevious messageNext messageBottom of page Link to this message

Sshbsn
Posted on Friday, October 15, 2004 - 08:55 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Kbbeckius.........1
Thunderbolt....0

« Previous Next »

Add Your Message Here
Post:
Bold text Italics Underline Create a hyperlink Insert a clipart image

Username: Posting Information:
This is a public posting area. Enter your username and password if you have an account. Otherwise, enter your full name as your username and leave the password blank. Your e-mail address is optional.
Password:
E-mail:
Options: Post as "Anonymous" (Valid reason required. Abusers will be exposed. If unsure, ask.)
Enable HTML code in message
Automatically activate URLs in message
Action:

Topics | Last Day | Tree View | Search | User List | Help/Instructions | Rules | Program Credits Administration