wrillo Posted July 30, 2009 Report Share Posted July 30, 2009 Because I'm bored and haven't used my math skillz in quite some time... I'll give it a shot, but I"m sure I'm rusty and will miss variables.1) Motorcycle (Assume R6)Mass = 180 kg (wet)CG = 850mm (+z), and 635mm (-x) - assuming CG is slightly below seat height and slightly forward of the midpoint of the wheelbase.2) SunfireMass = 1202 kgCG-z; 1389mm total height - 145mm ground clearance * 43% + 145mm = 680mm (+z)Assuming +z CG is approximately 43% above the ground clearance of the vehicleCG-x; Because it's T-boned, CG is approximately 50% of the vehicle track, but we'll shift it slightly left to account for the weight of the driver (160lbs woman? would have a 6% effect on the weight of a 2650lbs vehicle... so lets only shift the weight 3.5% from the center to account for counterbalancing factors.) = 1709mm * 46.5% = 795mm in the +x direction.0,0,0 is located at the point of impact.The initial moment arm (rotational torque) is the delta on the z-axis = 200mmShort of doing a full dynamics calc... the force required to begin a rotation of the vehicle off the ground should be somewhere around ((1202/2)*9.8, only have to get two wheels off the ground to begin rotation) 5890N, so assuming the collision happened over 0.25 seconds - because the car and bike will both absorb some impact, the motorcycle would've had to be traveling somewhere in the vicinity of (180*.2*x=5890*.25 which yields) 40.9 m/s of an equivalent velocity force to overcome half the weight of the car due to gravity. So, the biker would've had to be traveling greater than that... which converted to english is 91.5 mph.Someone check my math (and assumptions). I guess I didn't need CG-x unless I was going to do a full dynamics calc. Ohh well, they're there w/ my assumptions if anyone wants to do it.so x = (5890N * .25sec) / (180kg * .2m) = 40.9x = kg*m/s² * sec / (kg*m)doesn't that leave x in s^(-1) ?Also you're assuming that the motorcycle stops after impact and releases all of its energy into the car. You're also assuming this to be a completely elastic collision, but we know its a plastic impact Quote Link to comment Share on other sites More sharing options...
Disclaimer Posted July 30, 2009 Report Share Posted July 30, 2009 (edited) I made it a Force = Force.F = ma (where F is the cars force due to gravity)F = mv/ deltaT (where mv is momentum of the bike and deltaT is the time of collision)... along with the .2 multiplier for the torque arm.Yes, there are A LOT of assumptions... it's all 'back of an envelope' calcs just to get in a reasonable ballpark. No one wants the REAL answer anyway... they really just want ballpark. You want a real answer, run a computer simulation. Edited July 30, 2009 by JRMMiii Quote Link to comment Share on other sites More sharing options...
ChickOn2 Posted July 30, 2009 Report Share Posted July 30, 2009 I made it a Force = Force.F = ma (where F is the cars force due to gravity)F = mv/ deltaT (where mv is momentum of the bike and deltaT is the time of collision)... along with the .2 multiplier for the torque arm.Yes, there are A LOT of assumptions... it's all 'back of an envelope' calcs just to get in a reasonable ballpark. No one wants the REAL answer anyway... they really just want ballpark. You want a real answer, run a computer simulation.So... it is mathematically plausible to think the boy was truckin' at 85-90 mile an hour..? Quote Link to comment Share on other sites More sharing options...
magley64 Posted July 30, 2009 Report Share Posted July 30, 2009 So... it is mathematically plausible to think the boy was truckin' at 85-90 mile an hour..?mathematically plausible that 95 was the minimum speed of the bike... Quote Link to comment Share on other sites More sharing options...
Disclaimer Posted July 30, 2009 Report Share Posted July 30, 2009 Per all my assumptions, yes.. the guy would've had to been going 91.5mph or more to get the car up on 2 wheels. But, there are a lot of assumptions I made to make the math easier and there are other factors that may've caused it to roll? Did it leave the road? Was there an embankment? TONS of other factors I didn't account for or know of... Quote Link to comment Share on other sites More sharing options...
wrillo Posted July 30, 2009 Report Share Posted July 30, 2009 I made it a Force = Force.F = ma (where F is the cars force due to gravity)F = mv/ deltaT (where mv is momentum of the bike and deltaT is the time of collision)... along with the .2 multiplier for the torque arm. Yes, there are A LOT of assumptions... it's all 'back of an envelope' calcs just to get in a reasonable ballpark. No one wants the REAL answer anyway... they really just want ballpark. You want a real answer, run a computer simulation.torque is a vector, you'd need the component that is acting vertically based around the center of mass of the car.Another thing I was thinking of was the impact and loading of the suspension. This is some old crappy suspension on a sunfire so there is probably a lot of play. So the tire of the motorcycle hits the car and loads the suspension on the other side (collision one). Now we don't have half the cars mass to lift to roll the car when the rest of the bike hits. (collision two)I'm just saying I wouldn't go to court and tell them he was going 90+ until I did a more thorough calc Quote Link to comment Share on other sites More sharing options...
magley64 Posted July 30, 2009 Report Share Posted July 30, 2009 why is 90 in a 65 hard to swallow?i know "someone" who does that on a regular basis, though "he" is with nick, that you cool it at intersections...then wind it back up Quote Link to comment Share on other sites More sharing options...
max power Posted July 30, 2009 Report Share Posted July 30, 2009 I just have to say that the difference between one year of driving experience and three years of driving experience in general would make the difference. Granted, probably a new rider doing something stupid but lets hope a more experienced driver would have possibly paid more attention...all of this shit is based on, well nothing but my own thoughts from the info we have.Honestly, the difference between 1 year and 4 years of driving experience is shit. Quote Link to comment Share on other sites More sharing options...
ChickOn2 Posted July 30, 2009 Report Share Posted July 30, 2009 Per all my assumptions, yes.. the guy would've had to been going 91.5mph or more to get the car up on 2 wheels. But, there are a lot of assumptions I made to make the math easier and there are other factors that may've caused it to roll? Did it leave the road? Was there an embankment? TONS of other factors I didn't account for or know of...Is there any possible way the boy could have been doing the limit? Shitty pontiac suspension, slightly heavier bike? Alien ship flying overhead kicking up extra wind...? I'm trying to help the kid out here... Quote Link to comment Share on other sites More sharing options...
Disclaimer Posted July 30, 2009 Report Share Posted July 30, 2009 Ok, we can work backwards... how fast do you want the kid to be going? Whatever number you give me, I'll just turn that back around and tell you all the assumptions you'd have to make to have THAT be a plausible case... Quote Link to comment Share on other sites More sharing options...
ChickOn2 Posted July 30, 2009 Report Share Posted July 30, 2009 Ok, we can work backwards... how fast do you want the kid to be going? Whatever number you give me, I'll just turn that back around and tell you all the assumptions you'd have to make to have THAT be a plausible case...It would have been nice if he was going, say... 71 mph in a 65. Still a peppy speed, but probably not fast enough to get pulled over. Quote Link to comment Share on other sites More sharing options...
Whitey1 Posted July 30, 2009 Report Share Posted July 30, 2009 is it possible that the car and bike slid into a ditch and that caused tha car to flip? I am not far from there so I may take a ride to see what the actual area looks like. Either way, I am saddened as 2 individuals have been directly fucked by this few moments in time. Quote Link to comment Share on other sites More sharing options...
magley64 Posted July 30, 2009 Report Share Posted July 30, 2009 It would have been nice if he was going, say... 71 mph in a 65. Still a peppy speed, but probably not fast enough to get pulled over.you should be a cop...http://www.ohio-riders.net/showthread.php?t=31728"it would be nice if she were drunk, and say...swerved into my path" Quote Link to comment Share on other sites More sharing options...
Whitey1 Posted July 30, 2009 Report Share Posted July 30, 2009 you should be a cop...http://www.ohio-riders.net/showthread.php?t=31728"it would be nice if she were drunk, and say...swerved into my path"Ok, so some guys that happened to be cops did bad things. However it wasn't every cop in the world. Jeez I hate hearing that shit. Cops can be looked at just like bikers.....there are a few bad ones that make the rest look bad. However as bikers we stand up and proudly say that we aren't all bad.......Give the LEO's the same benefit of the doubt. Quote Link to comment Share on other sites More sharing options...
ChickOn2 Posted July 30, 2009 Report Share Posted July 30, 2009 you should be a cop...http://www.ohio-riders.net/showthread.php?t=31728"it would be nice if she were drunk, and say...swerved into my path"LOL! sometimes, you have to bend it a little! (that's what HE said!) Quote Link to comment Share on other sites More sharing options...
magley64 Posted July 30, 2009 Report Share Posted July 30, 2009 Ok, so some guys that happened to be cops did bad things. However it wasn't every cop in the world. Jeez I hate hearing that shit. Cops can be looked at just like bikers.....there are a few bad ones that make the rest look bad. However as bikers we stand up and proudly say that we aren't all bad.......Give the LEO's the same benefit of the doubt.just a joke dude...chill... Quote Link to comment Share on other sites More sharing options...
Disclaimer Posted July 30, 2009 Report Share Posted July 30, 2009 71mph ~ 32 m/sSo, you'd have to increase the mass of the motorcycle, or difference in CGs. Or, you would have to decrease the amount of force it takes to cause the sunfire to roll, or the impact time.A 2008 R6 (dry) is 366lbs which is 166kg (Per Bikez.com)... I added more weight on (14kg) to account for gas and fluids. You can assume it was a larger bike, like an R1, which is 177kg (dry), or it was a FZ bike... in 2008 Yamaha didn't make cruisers... that's all under their Star brand. I suppose you could maybe make a case for an FJ, but honestly - what do you think a 20-yr old was rolling around on? Statistically, I bet it was an 'R' bike.Difference in CG heights... I suppose we could set the CG of the sunfire lower and the CG of the bike higher. Every mm difference accounts for 0.2m/s (.44mph) - so all else equal, the CG difference between the two would have to be an additional 55mm from my assumptions (255mm difference).Force on the car due to gravity.. I'm pretty confident that's fixed. The only fudge factor I used is what % of the total gravitational force would be enough to get the car up on two wheels. I used a 50% factor... is that right? I dunno. It's a guess.Impact time - another factor I fudged, but I did a smidgeon of 'net research that the 0.25 sec I used was semi-plausible, given all the other variables mentioned (time for plastic deformation, give in the suspensions, etc). In order to get to your 71mph number, the deltaT crash time would have to be around 0.1975, so the crash would have to happen quicker. Given the physics and material properties of the vehicles - I doubt it would be quicker. I thought my 250ms was a generous number (err on the conservative [quick] side).So, can you paint a believable story with that information? Go right ahead, you just have to convince a jury of your peers... Quote Link to comment Share on other sites More sharing options...
RSVDon Posted July 30, 2009 Report Share Posted July 30, 2009 Honestly, the difference between 1 year and 4 years of driving experience is shit.I call bullshit. I can guarantee that between day 1 and year 4 I had changed a lot as a driver, and for the better. (racing classes with the personal car may have helped the matter though) Quote Link to comment Share on other sites More sharing options...
Whitey1 Posted July 30, 2009 Report Share Posted July 30, 2009 just a joke dude...chill...I'm sorry for jumpin your shit like that, it isn't you making a slight joke that gets me. I read this crap all over and see it on tv and I just snapped. Quote Link to comment Share on other sites More sharing options...
magley64 Posted July 30, 2009 Report Share Posted July 30, 2009 I'm sorry for jumpin your shit like that, it isn't you making a slight joke that gets me. I read this crap all over and see it on tv and I just snapped.it's cool:popcorn: Quote Link to comment Share on other sites More sharing options...
ChickOn2 Posted July 30, 2009 Report Share Posted July 30, 2009 Ok, so some guys that happened to be cops did bad things. However it wasn't every cop in the world.Give the LEO's the same benefit of the doubt.I agree that not EVERY cop is an ignorant asshat, but THOSE cops were ignorant asshats.And I'm sorry... but they are on my tax dollar, and they carry firearms. They MUST be held to a higher standard than the average person. They're not accountants or mechanics, they are charged with protecting public safety and have to be trustworthy. No tolerance for asshattishness, period. Off with their heads. Quote Link to comment Share on other sites More sharing options...
John Posted July 30, 2009 Report Share Posted July 30, 2009 Until I see any different evidence I'm placing the fault on the rider. He was going way too fast for the conditions.it doesnt matter if the other guy is going 20 or 200. if you fail to yield to them, you are at fault period.otherwise every jerkoff who runs a stop sign or tries to make a quick left and gets tagged would just say "zomg but they were speeding!!!!1". still its your responsibility to make sure its clear before you proceed. stop. look. and then look again. Quote Link to comment Share on other sites More sharing options...
ReconRat Posted July 30, 2009 Report Share Posted July 30, 2009 keep it simple. If the bike went down and under, and then flipped up when wedged, it would tip the car like a lever. Besides, I remember a Pontiac that would flip on its side if you yanked the steering wheel too fast... Quote Link to comment Share on other sites More sharing options...
max power Posted July 30, 2009 Report Share Posted July 30, 2009 I call bullshit. I can guarantee that between day 1 and year 4 I had changed a lot as a driver, and for the better. (racing classes with the personal car may have helped the matter though)Maybe, but the mental maturity level of a typical 16 yr. old and a typical 20 yr. old arent much different. Now I know you younger peeps are gonna jump my shit about that, but dont. You will be wasting your time. Notice I said typical. There are some (very few) exceptions. Quote Link to comment Share on other sites More sharing options...
aracnid007 Posted July 30, 2009 Report Share Posted July 30, 2009 You guys can do all the math you want, but it's real hard for me to believe that anyone going 90+ mile an hour ends up in fair condition after broadsiding a car. As far as the flipping goes, there has to be other variables involved. Fact is, girl pulls out in front of motorcycle from stop sign, that's all I need to know. Quote Link to comment Share on other sites More sharing options...
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