Gravity, Inertia, G's, Torque, Fjr,

[BlueHammer]

I was riding along today and my mind drifted AGAIN.

How many G's can the accelerating FJR pull?

How many can the FJR 'push'? at max braking before lock-up?

How many Lateral G's on a skidpad?

How can I measure this? an accelerometer? Dyno?

What are the comparisons btwn the FJR's results and other bikes?

Does torque have a direct relation to G's?

I stunk up the classroom during the science lesson when I was a kid, but now I have more questions than answers. sorry Mr peitrizak, Thanks for passing me anyhow!

 

[twowheelnut]

Er, who cares?

 

[BlueHammer]

Oh, it's SOOO GOOD to see you posting again TWN!! You make Mister Limpet proud to be your avatar!! :clown2:

 

[ionbeam]

It's disgusting I know some answers to the troll, err, trolling questions. :dribble:

How many G's can the accelerating FJR pull?

Typically 1.4 to 1.5 Gs at the drag strip. Determined at a point between wheelie and tire spin.

How many can the FJR 'push'? at max braking before lock-up?

ABS engaged, 1.6 Gs, very traction and tire temp/condition related. Acceleration is all about one tire, braking is about 2 tires but even more about weight transfer removing most of the traction from the rear wheel.

How many Lateral G's on a skidpad?

I ain't touchin' this one. Round and round till you spin out. The instant before low/high siding is peak lateral Gs. :wacko:

How can I measure this? an accelerometer? Dyno?

On a pocket dynamometer that is a multi-axis accelerometer. In my case it is a G-Tech (here after known as a GT) The GT uses aviation grade suspended mass accelerometers, precision timers, advanced high speed A/D converters and a **** load of software. With a little care it produces high accuracy and best of all repeatable results. There are better units than the GT but not at the same price. Fortunately it locks the results for review/download later so you don't have to focus on the GT while riding/driving 10/10ths.

What are the comparisons btwn the FJR's results and other bikes?

At this point you are approaching 'bench racing'. Catch up with a friend that has a different machine, before the beer, and go to a track. If real life worked like 'numbers by the book' bumblebees wouldn't fly.

Does torque have a direct relation to G's?

In which axis? In straight line, yes. Traction, tire condition, size of rider's balls, proximity to police and pretty women will all have an effect on results.

Ask a few frivolous joking questions and some social misfit goes and takes you seriously. The better answers will be along shortly. If trinibob gets his own smilie I need a dork/geek in glasses :haha:

Alan

 

[gasman]

**** ionbeam, I think that's pretty cool that you can answer those questions. Having an IQ in the minus range as I do, things like that really impress me. JB :wacko:

 

[BlueHammer]

they were whimsical, yet serious questions.

I was thinking about the GT for some time, but didn't know if I really needed one for my toys. Thanks for the lessons!!

here is your smilie: :graduate:

 

[outrace]

I think those numbers are a bit high. As a general rule, the average roadrace bike can only pull 1.3 in either accel or decel due to wheelies and stoppies. Laterally, a full on roadrace bike in AMA, WSB, or MotoGP trim can only manage 1.1 to 1.3 G.

No, I haven't hooked up a force meter, nor done the acceleration math. It's info I got from a physics nerd who did the calcs for a GP program.

 

[twowheelnut]

Oh, it's SOOO GOOD to see you posting again TWN!!  You make Mister Limpet proud to be your avatar!!  :clown2:

I'll have you know, sir, that is NOT Mr. Limpet. It is Barney Fife dressed in his Sunday best for his date with Thelma Lou.

And, I got yer 'G' righcheer, pal!

 

[ionbeam]

I bought the GT to help me beat the **** out of my car but I have also put it on a couple of bikes. It is way harder to get good results on the bike. GT does note that their older device may not work well on a motorcycle because it 'only' reads up to 1.7 Gs. Due to the low mass and high HP of bikes the GT sees extremely sharp G loading and may register slightly skewed readings. When I autocross my car the GT will read very high lateral Gs and my lap times will be slow. As I adjust to the course and my driving gets smoother Gs go way down and times get much better. Even though my car is rated someplace around .88 Gs on a skid pan I can see 1.4 Gs by jerking the wheel (and still not actually spin out).

At New England Dragway my GT does tell me that changes I make in suspension and tire pressures are either making thing better or worse leaving the starting line. When I make my first run with my car and everything is left at street settings I usually see .78 Gs and have 60' times around 2.2x seconds. After several runs and a little fiddling I can see ~1.0 Gs and my 60' times will be 1.9x. That is major! At .78 Gs you know you have left quick, at 1.x Gs it is like getting whacked in the back.

Alan

 

[BlueHammer]

The great and venerable Mr. Knots will always be the incredible Mr. Limpet to me.

Barney who? :rolf:

 

[twowheelnut]

Ah, a lover of fish lips, eh? Which reminds me...

"Fish heads, fish heads

Oohy goohy fish heads

Fish heads, fish heads

Eat 'em up, yum."

 

[Bounce]

they were whimsical, yet serious questions.
I was thinking about the GT for some time, but didn't know if I really needed one for my toys. Thanks for the lessons!!

here is your smilie: :graduate:

I gots me one of dem. Not the fancy newer ones, but this one is pretty fun. Quite a difference when using it in the WRX and in the 96GMC Sierra. :lol:

Been meaning to mount it to the windshield of the FJR and do some runs. Finding a good place where I can go back and do it again is the hard part. I'd prefer do 3 out of 5 and drop the high and low runs. Then you do it for each test (0-60, 0-100, 0-60-0, roll on, hp, etc.). Takes a bit of time to do it all.

 

[Penforhire]

Yeah, that braking is way too high for any ABS model. Almost all ABS is programmed for something like 1 G deceleration max (120-odd feet), maybe a little higher on the Ducati ST4s.

 

[Thug]

I beleive the answer is once again 42. <_<

 

[ionbeam]

Almost all ABS is programmed for something like 1 G deceleration max

So, if you are on sand and can't achieve 1 G deceleration why does ABS engage? Note that my G-Tech was set to lock and hold only the very peak G force. When measuring braking G force there is peak force and average force, you have to chart G force over time to see true brake performance.

In automotive ABS applications the trigger point for ABS is typically defined as when wheel slip angle becomes greater than 87% This is the critical point between a rolling wheel and a skidding wheel. [translator] When vehicle speed and wheel speed vary by more than 13% (impending lockup) ABS will engage until vehicle and wheel speed come closer to balancing. With a slip angle of 86% the wheel is already beginning to skid. [/translator]

The peak G force number is determined by traction and how quickly and forcefully the wheel is asked to decelerate. Traction will vary with road surface, tire type, tire condition, temperature and weight transfer. In theory friction is independent of surface area but because there are a number of forces acting together, a larger contact patch will generally produce shorter braking distances. A problem that can arise is tire dust -- generated during extreme braking can sometimes get under the tire reducing braking force.

Wheel speed is measured by the ABS sensors counting the teeth in the wheel hub as they pass by.

Alan

 

[ionbeam]

Thug sez

I beleive the answer is once again 42.

The correct answer is 6, 12, 24, and keg

The bonus answer is shot, pint, fifth and gallon

:lol:

 

[Just Plain Dave]

"Questions for those with smarts."

I don't belong on this thread. :stupid:

 

[RickL]

Oh, gimme a break - you guys are just making this stuff up! Next you'll tell us that the captoblyptus engages the framistan to ungulate the doowadiddy, thus making the G forces equal the imprint of the tire on the pavement (commonly known as the G spot).

 

[Woodstock]

I think it's the flux capacitor.