For years I have heard the old adage that losing 6 or 7 pounds is the same as gaining 1 hp.
I never thought the relationship should be a constant.
I finally put pen to paper and did some calculations (physicists do that sort of thing). The result I came up with after a couple different approaches turned out to be rather simple and after a couple minutes made sense.
Take the weigh of bike and rider (in full gear). Divide by the power of the bike.
That number is the amount of weight you would have to lose to free up one horsepower.
Bikes with lower weight to power ratios have to lose less weight to gain a horsepower. That is high power bikes have more to gain by losing weight than do lower power bikes (modern liter bikes do not weigh much more than say an SV).
Sweet, so my new bike is up about 5 hp over last years bike and I am about 10pounds lighter then last year so I can add about 2 extra HP to the 5HP for a 7 HP gain..... Bring on the Salads.......
Brian, you make my head hurt. So what's the fomula you came up with? Give 3 examples and show your work... ;)
Let's say that my bike weighs 380 pounds, I weigh 170 in gear..So you add the two together and get 550 pounds. Now divide the 550 by 119hp and you get 4.621848739. I am assuming that is how many pounds I would have to lose to gain 1hp...If that is the case and I am 10 pounds lighter then last year(saying that the bikes weigh the same then I would have a gain of 2.16 hp over my last years weight. Did I do something wring here Brian? Please correct me if I did...
Interesting....
That number you get by adding up the weight of the rider and bike divided by the horsepower is the amount of weight you and/or the bike would have to loose to gain 1 HP correct?
it doesn't necessarily have to be the rider loosing weight it can be your machine too?
QuoteInteresting....
it doesn't necessarily have to be the rider loosing weight it can be your machine too?
Yes.
WOW, now my head hurts. Come on guys and gals can't we just open the throttle all the way, hold on and ok put some skill in there and win some races... ::) As everyone says life begins at 150 and at 180 fear just can't catch up :-X
But what if you were to take, say, 12lbs off the wheels?
Lemme see if I got this right:
My SV weighs, what, about 350 lbs? I weigh 180, plus gear -- figure 200? That's 550lbs, and 70hp . . . 7.8 lb/hp.
Good grief -- so I need to lose about 40 pounds. Between now and Friday. This is going to be difficult.
QuoteBut what if you were to take, say, 12lbs off the wheels?
Yup, don't forget that equation. Rotational mass is a better place to reduce weight, but comes at probably the steepest price.
It seems to be that you can reduce weight either cheap, or easily, but not both.
Losing rider weight is very cheap, but not easy.
Buying carbon fiber rims is easy, but not cheap. :)
Pauly: I need a few more ponies. What are the odds of you getting a salad bar in the Polar-Optics trailer. (race weekend).......... Or how about just a bar. ;D
I have to disagree a bit here... let's see if I have what you're saying right.
For example... I've been a lazy fat a$$ during the off season and I weigh 180 pounds. Let's say that in addition to my R1 superbike I also have a RS125. You're saying that I will proportionally go faster on the R1 if I lost, say, 15 pounds? I know there are a lot of little people that race 125s that when they move up to a bigger bike don't do as well because they lose their advantage. It seems like you have more to gain by losing weight the smaller the bike you ride is. I mean, that's half the reason I bought a rocketship... so I wouldn't have to starve myself... are you telling me that I may have to start eating Broccoli again? ;D
of course it a sliding scale and you would need to re-equate the new mass plus HP to get a more accurate estimation... right??
I flunked college algebra 3 times I am in finance.... :-/
thank the lord for calculators ;D
WTB 225 HP SV650. :-[
QuoteI have to disagree a bit here... let's see if I have what you're saying right.
For example... I've been a lazy fat a$$ during the off season and I weigh 180 pounds. Let's say that in addition to my R1 superbike I also have a RS125. You're saying that I will proportionally go faster on the R1 if I lost, say, 15 pounds? I know there are a lot of little people that race 125s that when they move up to a bigger bike don't do as well because they lose their advantage. It seems like you have more to gain by losing weight the smaller the bike you ride is. I mean, that's half the reason I bought a rocketship... so I wouldn't have to starve myself... are you telling me that I may have to start eating Broccoli again? ;D
Yea.. b/c the power to weight ratio is smaller on the R1.
All makes sense....but, isn't torque more important than hp? Not saying you don't need hp, but torque is the ability to change velocity (accelerate) and hp maintains velocity (constant rear wheel speed) under dynamic load conditions.
And, if you do the flywheel calc's, its better to have more rotational mass in the rims (fly wheel effect) for torque and loose the weight in my a$$ (non-rotational mass; unless of course, I crash). So save the money on the light wheels and quit eating pasta...right??
You Got it D_Dog, one open Bar in the Polar-Optics trailer!
After the races of coarse 8)
Bring your own salads, I'll be the one grilling the steaks :)
Yea, but just as a basic statement of rotational mass... it's easier to turn and accelerate (2) 10 pound wheels vs. (2) 20 pound wheels.
Ok, so you're a very good rider. And you race a two bikes. One bike makes about 40% more power, which is the difference between a 600 and a 1000. But it only nets you .75 of a second, which is the difference between a 1000cc four vs a 600cc four at some smaller tracks.
You'll have to loose 175 pounds on the 600 package to make up the power to weight ratio...for less than a second.
Hmmmmmm
Right... and as well... weight has an effect on cornerspeed right?... so you lose weight and 'gain' power, but you'd also gain corner speed. All else being equal.
Then the question is...
Is everything equal?
If it were, then only the best power to weight ratio would win.
well yea, we're not talking about how to win, we're talking about how you can 'theoretically' increase HP by shedding weight. Now the arguement of spending $300 for a gym membership, or for a race school/track day is another thing. :)
I think money is better spent on improving your skill instead of trying to shed a couple lbs. just to give you an extra couple milliseconds or so per lap time... unless you're consistently riding near exact lap times and at the to of your class and you need to find an edge.
I've also heard this theory stated as:
"For every 1 lbs of weight you lose you gain X HP on ACCELERATION"
Meaning a 340lb 75hp Hawk is going to accelerate up to it's top speed faster than a 380lb 75hp one. Not a 340/75 Hawk going to have a faster top speed than a 380/75 one.
Sort of makes sense to me.. again just another way I've heard it explained.
Personally I'd rather gain that Mythological HP on acceleration over top speed anyday.
QuoteOk,You'll have to loose 175 pounds on the 600 package to make up the power to weight ratio...for less than a second.
Hmmmmmm
So I should have started my diet last year? ;D
Quote So I should have started my diet last year? ;D
No Garth. Just ride the 1000!
Dave, you took the words right out of my mouth...
I was originally going to reply saying "the weight loss won't make any of you suck any less than you already do", but I felt it would have been interpreted as a negative post.
Quote"the weight loss won't make any of you suck any less than you already do",
So much for my motivation, back to cheese burgers and Tommy's Tripple D's :o
QuoteLet's say that my bike weighs 380 pounds, I weigh 170 in gear..So you add the two together and get 550 pounds. Now divide the 550 by 119hp and you get 4.621848739. I am assuming that is how many pounds I would have to lose to gain 1hp...If that is the case and I am 10 pounds lighter then last year(saying that the bikes weigh the same then I would have a gain of 2.16 hp over my last years weight. Did I do something wring here Brian? Please correct me if I did...
Everything looks OK.
QuoteBut what if you were to take, say, 12lbs off the wheels?
You get more benefit from reducing rotating mass. There is no general relationship between losing rotating weight and gain in power because it is a function of the weight reduction and where the weight is lost. To calculate for a wheel you would need to know the moment of inertia of the wheel before and after the weight loss.
Since I don't know where on the wheel you are losing the weight, I cannot tell you how much of a difference it would make.
QuoteI have to disagree a bit here... let's see if I have what you're saying right.
For example... I've been a lazy fat a$$ during the off season and I weigh 180 pounds. Let's say that in addition to my R1 superbike I also have a RS125. You're saying that I will proportionally go faster on the R1 if I lost, say, 15 pounds? I know there are a lot of little people that race 125s that when they move up to a bigger bike don't do as well because they lose their advantage. It seems like you have more to gain by losing weight the smaller the bike you ride is. I mean, that's half the reason I bought a rocketship... so I wouldn't have to starve myself... are you telling me that I may have to start eating Broccoli again? ;D
I never said anything about going faster. Going faster is up to the rider.
Think of it this way. By losing weight you are trying to 'free up' horsepower.
If your bike has a ratio of 8lb/hp, you would have to lose 8 lbs to free up 1 hp.
Yes it seems counterintuitive. I often tell my students that physics common sense and common common sense are often not the same.
Quoteof course it a sliding scale and you would need to re-equate the new mass plus HP to get a more accurate estimation... right??
Yes, as the weight to power ratio changes, the amount of weight needed to gain 1 hp changes.
QuoteI flunked college algebra 3 times I am in finance.... :-/
thank the lord for calculators ;D
Calculators don't do any work for you. They are only as good as the operator. GIGO :)
QuoteAll makes sense....but, isn't torque more important than hp? Not saying you don't need hp, but torque is the ability to change velocity (accelerate) and hp maintains velocity (constant rear wheel speed) under dynamic load conditions.
Hmmm, how do I say this nicely......NO.
Power the rate at which work is done (P=W/t). Your change in kinetic energy (due to acceleration) is the work done, the t is time. Power is essentially how quickly you can gain kinetic energy and hence acceleration.
Torque and power are directly related, so your above statement really doesn't make any sense.
QuoteAnd, if you do the flywheel calc's, its better to have more rotational mass in the rims (fly wheel effect) for torque and loose the weight in my a$$ (non-rotational mass; unless of course, I crash). So save the money on the light wheels and quit eating pasta...right??
Actually losing rotating weight gives the most bang for the buck, but losing too much can make it difficult to harness the power (wheel spin, revs will rise more quickly).
Maybe I need to teach a motorcycle physics course in the evenings at the track.
QuoteOk, so you're a very good rider. And you race a two bikes. One bike makes about 40% more power, which is the difference between a 600 and a 1000. But it only nets you .75 of a second, which is the difference between a 1000cc four vs a 600cc four at some smaller tracks.
You'll have to loose 175 pounds on the 600 package to make up the power to weight ratio...for less than a second.
Hmmmmmm
Never said there was any direct correleation to lap times did I?
Like I have said before, comparing different classes of bikes is apples to oranges. It will give no indication of the lap times of a 600 with the same weight to power ratio as a 1000. They are different bikes with different dynamics. To try to get a correleation you would need to compare to bikes with identical engines, one heavier, one lighter. That is how science is done.
Less weight has other advantages, less tire wear, less crash damage, less brake wear, suspension action can improve (unsprung weight), etc.
I was just correcting a common misconception. One down many more to go (damping not dampening). A physicists work is never done.
QuoteI've also heard this theory stated as:
"For every 1 lbs of weight you lose you gain X HP on ACCELERATION"
Meaning a 340lb 75hp Hawk is going to accelerate up to it's top speed faster than a 380lb 75hp one. Not a 340/75 Hawk going to have a faster top speed than a 380/75 one.
Sort of makes sense to me.. again just another way I've heard it explained.
Personally I'd rather gain that Mythological HP on acceleration over top speed anyday.
Weight has nothing to do with top speed. Top speed is determined by drag vs. power. Assuming that the additional 40 lbs in your example do not affect the aerodynamics of the bike, the 2 Hawks would have the same top speed, the lighter one would reach top speed sooner.
I was calculating based upon acceleration. If you only lose weight and do not increase the power of your bike and do not change the drag, your bike will have the same top speed. If you want to increase top speed you need to increase power or reduce drag.
QuoteDave, you took the words right out of my mouth...
I was originally going to reply saying "the weight loss won't make any of you suck any less than you already do", but I felt it would have been interpreted as a negative post.
True, but the point of my post was not to help lap times but to correct a common misconception. Should have done it sooner, the calculation is done with high school physics and algebra.
I enjoy the technical side of motorcycling as much as I do riding. I enjoy building a bike almost as much as I do riding it. Part of building is reducing unwanted/needed weight and also relocating it (both to get a better front to back weight distribution and the center of mass at a proper height - there is a reason that Yamaha raised the CM of their bike after Rossi joined the team). Much of it is not horribly expensive, it does take time and the proper machines (which I have access to and know how to use - which is part of the fun - making stuff no one else has).
QuoteYes, as the weight to power ratio changes, the amount of weight needed to gain 1 hp changes.
Calculators don't do any work for you. They are only as good as the operator. GIGO :)
who you calling a gigo? ;D
QuoteWeight has nothing to do with top speed. Top speed is determined by drag vs. power. Assuming that the additional 40 lbs in your example do not affect the aerodynamics of the bike, the 2 Hawks would have the same top speed, the lighter one would reach top speed sooner.
I was calculating based upon acceleration. If you only lose weight and do not increase the power of your bike and do not change the drag, your bike will have the same top speed. If you want to increase top speed you need to increase power or reduce drag.
So the statement I made is true / clearer wording.
Thx Mr. Physics.
"For every 1 lbs of weight you lose you gain X HP on ACCELERATION"
QuoteSo the statement I made is true / clearer wording.
Thx Mr. Physics.
"For every 1 lbs of weight you lose you gain X HP on ACCELERATION"
The statement isn't correct.
By losing weight you are not gaining any power.
You are reducing your weight, which will increase acceleration for a given amount of power.
A better statement would be:
The acceleration gained by losing X lbs is the same acceleration as adding 1 hp with the original weight.
In science statements such as 'you know what I meant' don't work - even thought my students seem to think so. You must be precis in your wording (also why we use very specific definitions), there can't be any ambiguity, no guesssing at what is meant. To a non-scientist it may seem anal, the difference my seem very subtle, but the changing of a few words can drastically change the meaning of a statement.
QuoteWeight has nothing to do with top speed. Top speed is determined by drag vs. power. Assuming that the additional 40 lbs in your example do not affect the aerodynamics of the bike, the 2 Hawks would have the same top speed, the lighter one would reach top speed sooner.
I was calculating based upon acceleration. If you only lose weight and do not increase the power of your bike and do not change the drag, your bike will have the same top speed. If you want to increase top speed you need to increase power or reduce drag.
So the loss in body weight will give the rider a smaller frontal area - therefore reducing the wind resistance force (drag) at any speed. Since the frontal area is actually a squared factor in a resistance equation (area X area) the rider gains speed due to less drag - even though the engine HP stays the same.
So think of all that treadmill time as making you more aerodynamic.
;D
QuoteSo the loss in body weight will give the rider a smaller frontal area - therefore reducing the wind resistance force (drag) at any speed. Since the frontal area is actually a squared factor in a resistance equation (area X area) the rider gains speed due to less drag - even though the engine HP stays the same.
So think of all that treadmill time as making you more aerodynamic.
;D
Execpt for the guys buying new r6s etc, because the 10" x 12" number plates they will have to bolt on the front of their bike will offset the frontal area loss.
QuoteSweet, so my new bike is up about 5 hp over last years bike and I am about 10pounds lighter then last year so I can add about 2 extra HP to the 5HP for a 7 HP gain..... Bring on the Salads.......
now all you need is some *go-fast* stickers. Extra 15 hp forsure. ;D
I've got the 16hp stickers, but they cost more...and weigh less... ;D
QuoteTrue, but the point of my post was not to help lap times but to correct a common misconception.
Good point...
QuoteI've got the 16hp stickers, but they cost more...and weigh less... ;D
Hey Dave... email me with a price for those wouldya? And can I run more than one set? And am I still SS legal? i was really looking for an alternative to getting back in shape (apparently round isnt a shape???) and learning how to work this fandangled contraption better. That Thorson kid better watch it... I'm gonna have me a 140hp R6... now I just need the 10x12 number plate and I'm good to go!
tia
Timmay
QuoteHey Dave... email me with a price for those wouldya? And can I run more than one set? And am I still SS legal? i was really looking for an alternative to getting back in shape (apparently round isnt a shape???) and learning how to work this fandangled contraption better. That Thorson kid better watch it... I'm gonna have me a 140hp R6... now I just need the 10x12 number plate and I'm good to go!
tia
Timmay
Ed Key gets his go-fast from Spyder stickies. ;) ;D
If you see me at the track, I'll give you a couple for free!
QuoteEd Key gets his go-fast from Spyder stickies. ;) ;D
If you see me at the track, I'll give you a couple for free!
I got a spyder patch on my leathers... I dont see how that could add to horsepower on the bike though?? I DID however seem to REALLY accellerate when I hit the pavement the first time with your patch on... hmmmmmmmm ;D
I need some kinda edge this year... things seemed easier when I was yella... ;)
tim
btw I think you chatted with my Buddy Ty today about some leathers... I think he's going to Rob for the Taichi's! 8) he really appreciated your info, I'm hopin to get him to the races when he gets back from over sea's!
QuoteI got a spyder patch on my leathers... I dont see how that could add to horsepower on the bike though?? I DID however seem to REALLY accellerate when I hit the pavement the first time with your patch on... hmmmmmmmm ;D
I need some kinda edge this year... things seemed easier when I was yella... ;)
tim
btw I think you chatted with my Buddy Ty today about some leathers... I think he's going to Rob for the Taichi's! 8) he really appreciated your info, I'm hopin to get him to the races when he gets back from over sea's!
Additional acceleration due to added weight of a spyder patch is virtually impossible.
;) ;D
I'm glad he's ordering from Rob, the Taichis are a good choice for him. Thanks for sending him my way!
no problem at all!! ;)
Brian,
I'm asking this question for Timmay 'cause he's afraid to-
How about the inverse? What is the effect of mASS on deceleration? ;D
QuoteBrian,
I'm asking this question for Timmay 'cause he's afraid to-
How about the inverse? What is the effect of mASS on deceleration? ;D
shut-yo-mouf old man... you stay outta this!!! I'ma gonna decelerate my mass below my ankle in yer depends covered arse!!! ;D
you see randy, afraid to continue losing to the "bigger" man... had to go out and buy himself a ringer of a 750 (damn that thing is sweet). you already had HP AND weight on me last year... you must be skeered of my new shiny white plates! ;) NOW i got stickers comin... you dont stand a chance!!
timmay!!!!
I better be nice if I'm gonna hitch a ride up north in april... when you headin to Hallet again Ray Ray??
You got a lot of room on the lower backside of those Taichis for all the decals and patches you want...more room than a I-70 billboard! :D
Hallett on Sunday, and I'll be wearin my depends for sure, this thing scares me.
Hope you can make it to RA.
QuoteYou got a lot of room on the lower backside of those Taichis for all the decals and patches you want...more room than a I-70 billboard! :D
Hallett on Sunday, and I'll be wearin my depends for sure, this thing scares me.
Hope you can make it to RA.
you sonofabitch.... haha
so I got a lil junk in the trunk... chics dig a round ass! ;D
No dice for Hallett.. if it was in 2 weeks I might be able to make it fly, Road America I am 90% sure I am IN now!!! Just need to make sure I get the new bike put together, i was not in a big hurry to get everything done at first, so I'll have to see how it goes. If I have the shock and bodywork in that would be the minimum... things are looking pretty good after chattin with Rob last night!
timmay
oh and in conclusion... weight has an impact on the application of HP and torque... and noone really nows how or how much for sure but your best bet is stickers... sorry to jack the thread ;)
QuoteBrian,
I'm asking this question for Timmay 'cause he's afraid to-
How about the inverse? What is the effect of mASS on deceleration? ;D
Actually braking is also acceleration :D
I like this stuff!! Yes I am a geek.
So you've dispelled the myth that a given amount of weight loss on a low hp bike has a greater effect then on a higher hp bike. I ran a few examples, and found that a given amount of wieght loss results in the same amount of increased hp avialable for acceleration, on a percentage basis, for a high hp bike as a low hp bike.
Just pointing this out so that all the lightwiehgt guys don't start getting fat.
Well I need to go, off shopping for a new pocket protector!! :D
Brian I think I need an explaination of the horsepower determines acceleration theory. My understanding is that horsepower is a force X a distance over a time. This determines a terminal velocity (which by the way is more a function of drag than weight unless you are going uphill) As stated earlier the important factor in acceleration is torque.
First let's agree that horsepower cannot be changed by gearing. Feel free to correct me if I am wrong here.
Second let's agree that torque CAN be changed by gearing. Again correct me if I am mistaken.
Finally let's agree that ANY motorcycle accelerates better in 1st than it does in 5th.
In first gear the engines output, lets just grab a nice even number out of the air, 50 lbsft at 5000 RPM is converted by the transmission and sprocket ratio to 5000 lbsft at 50 rpm resulting in great acceleration but the engine exploding somewhere south of 50 mph (ok I guess by now you can tell I ride a twin, you modern inline guys substitute about 90 or so here). Now let's go to 5th gear and take that 50 lbsft at 5000 RPM and convert it to say 250 lbsft at 1000 RPM. Not nearly as much kick in the pants off the line but when your drag catches up with your ability to make horsepower (some amount of toque in some amount of time) you have a much better chance of being somewhere south of the point of engine explosion.
An interesting side note here is that peak horsepower is nearly always made at a higher RPM than peak torque. Reason being the relationship between speed and torque. As RPM increases the engine begins to have breathing problems and torque starts to fall off but since horspower is torque in time the higher RPM almost always overcompensates for falling torque for a little while.
I guess in conclusion there is no way to figure how many HP a pound is worth. However since getting them off the rider is more likely to reduce aerodynamic drag (read less girth through the air) that might be the most profitable in terms of top speed while getting them off the rotating mass makes the most sense for acceleration.
Im not sure about the actual hp to weight ratio, but as someone who has lost 45 lbs since I started racing, I can tell you from experience that losing weight will help you in all aspects of riding. You will be able to brake later (less mass to slow down), corner faster (less mass trying to go straight), accelerate faster (again less mass to get moving), and you will most likely have better technique and less fatigue.
Losing wieght off the rider will have a better effect on cornering and braking than loosing it off the bike will, because by loosing weight off of the rider, you are effectively lowering the center of gravity, and increasing mass centralisation.
Quoteran a few examples, and found that a given amount of wieght loss results in the same amount of increased hp avialable for acceleration, on a percentage basis, for a high hp bike as a low hp bike.
Please give examples. What I'm finding is conflicting with this statement, and I want to be sure I'm reading it correctly.
QuoteIm not sure about the actual hp to weight ratio, but as someone who has lost 45 lbs since I started racing..
Did you bother changing spring rates?
Once I lost the weight I got a new bike, and got the suspension done acording to my current weight.
QuoteBrian I think I need an explaination of the horsepower determines acceleration theory. My understanding is that horsepower is a force X a distance over a time. This determines a terminal velocity (which by the way is more a function of drag than weight unless you are going uphill) As stated earlier the important factor in acceleration is torque.
I agree until the last sentance. Power is work/time. In a linear (non rotating) system work is force * distance. In a rotational system work = torque * angle (in radians, not degrees). Power is a combination of torque, angle and time. The angle and time are just as important as the torque. Sometimes it is written power = torque * angular velocity. The angular velocity is just as important as the torque when it comes to acceleration.
QuoteFirst let's agree that horsepower cannot be changed by gearing. Feel free to correct me if I am wrong here.
Second let's agree that torque CAN be changed by gearing. Again correct me if I am mistaken.
Looks ok.
QuoteFinally let's agree that ANY motorcycle accelerates better in 1st than it does in 5th.
IF you are at the same rpms. If you are at different rpms the bike may accelerate better in 5th than 1st (new R6, 1st gear at idle, compared to 5th gear just below the power peak).
QuoteIn first gear the engines output, lets just grab a nice even number out of the air, 50 lbsft at 5000 RPM is converted by the transmission and sprocket ratio to 5000 lbsft at 50 rpm resulting in great acceleration but the engine exploding somewhere south of 50 mph (ok I guess by now you can tell I ride a twin, you modern inline guys substitute about 90 or so here). Now let's go to 5th gear and take that 50 lbsft at 5000 RPM and convert it to say 250 lbsft at 1000 RPM. Not nearly as much kick in the pants off the line but when your drag catches up with your ability to make horsepower (some amount of toque in some amount of time) you have a much better chance of being somewhere south of the point of engine explosion.
An interesting side note here is that peak horsepower is nearly always made at a higher RPM than peak torque. Reason being the relationship between speed and torque. As RPM increases the engine begins to have breathing problems and torque starts to fall off but since horspower is torque in time the higher RPM almost always overcompensates for falling torque for a little while.
As long as the torque falls at a rate slower than the rpms increase, then power will rise as torque falls.
P(hp) = [torque (ft-lbs) * rpm]/5252
The 5252 is the conversion factor from ft-lbs-rotation/minute to hp
QuoteI guess in conclusion there is no way to figure how many HP a pound is worth. However since getting them off the rider is more likely to reduce aerodynamic drag (read less girth through the air) that might be the most profitable in terms of top speed while getting them off the rotating mass makes the most sense for acceleration.
I don't follow your conclusion.
Here is how I did it. We will assume acceleration on a flat surface (no hills) to keep things simple. Here is the calculation. Sorry it does involve math, but math is the language of physics.
(https://www.ccsforum.com/proxy.php?request=http%3A%2F%2Fmy.execpc.com%2F%7Etzracer%2Fpwcalc1.JPG&hash=28815e6a2311646925d10feb2f23dbcf59db7c0a)
(https://www.ccsforum.com/proxy.php?request=http%3A%2F%2Fmy.execpc.com%2F%7Etzracer%2Fpwcalc2.JPG&hash=fc744fe5b9771a0325e1579a905a8615650c0135)
So if I add 1 hp to my bike, the amount of weight I need to add to have it accelerate at the same rate (same change in speed/ the same time) regardless of gear, would equal the original weight to power ratio. Therefore, the equivalent of 1 hp is your current weight to power ratio. Since you are not inceasing the power by losing weight, you will not gain any top speed, but your bike will increase acceleration.
Brian, I think we should put that on the back of your leathers. ;D
http://scienceworld.wolfram.com/physics/SchroedingerEquation.html
equation 1 would be more fun.
Brian,
Let's take a specific bike, say that R6 you mentioned.
Let's actually take 2 of them to the drag strip. One with 13:49 sprocket set and one with a 17:49 sprocket set (again, being a twin rider I apologise if my selection of gearing is a little off). Which bike has more horsepower on the dyno? and which will arrive at the end of the drag strip first?
The bike with the shorter gear of 13:49 will arrive at the finish line first as it will have better acceleration due to the extra torque multiplication of the final drive and since I don't believe the R6 is capable of terminal velocity in a standing 1/4 mile the engine redline should not limit either bike.
Now were we to take this roadshow to Bonneville the outcome would be a little different. While the bike with 13:49 gears would accelerate faster, and since both bikes have the same horsepower the terminal velocity would be the same, the bike with 17:49 gears would have a much higher probability of still having an engine in operable condition after a 5 mile run (might also add that there is a possibility that the 13:49 bike would run out of its power band before reaching its theoretical terminal velocity).
All of this would be moot except for the basis of this thread. Your calculations should be using the weight to torque ratio of the bike+rider. I am going to have to go online and find some specs for various bikes and run some numbers but I think a more constant/duplicatable/meaningful question might be how many pounds to gain one rear tooth.
The basis of the discussion was no changes except for weight.
Using torque muddies the issue because there is not one figure for torque (dynos give crank torque). As you pointed out the torque value (at the rear wheel) changes based upon gearing. So what value to use?
The original point was to find the weight needed to be lost that would be equivalent to gaining 1 hp.
Changes in acceleration due to gearing are easy to calculate, it is just the percent change in the gearing.
Aside : In your example, the R6 with the shorter gearing may not win the drag race. It could top out in 6th gear before the end of the strip, it may be ddifficult to launch due to such short gearing, you will have to shift more.
Quotehttp://scienceworld.wolfram.com/physics/SchroedingerEquation.html
equation 1 would be more fun.
Along with a cat. ;)
QuoteAlong with a cat. ;)
In a box.....maybe.....
QuoteIn a box.....maybe.....
don't forget the gieger counter. =^..^=
Uncle :P
I'm still having a problem with the whole acceleration vs torque vs horsepower thing.
What I have learned here is that horsepower is in fact related to acceleration although I still haven't quite got my head fully wrapped around the exact relationship.
QuoteThe original point was to find the weight needed to be lost that would be equivalent to gaining 1 hp.
Changes in acceleration due to gearing are easy to calculate, it is just the percent change in the gearing.
In looking at your proof I noticed something, while the weight difference on the more powerful bike is smaller (lose less weight to make 1 HP) the value of that 1 HP is less (600lbs rider+bike with 100 HP will go 1% faster with 1 HP increase, 600lbs rider+bike with 200 HP will go .5% faster with 1 HP increase). I think there is a specific number of pounds for a HP gain of 1% that would apply to all bikes.
Paul