winders

Seriously? You are going to go with that?? You are worse than I thought.

In physics, there really is only acceleration. Acceleration is the rate at which the velocity of an object changes over time. If there is no velocity change, there is no acceleration.

In car terms, if you accelerate to 60 MPH and stay there, there is no more acceleration and no deceleration ever occurred.

Going from "accelerating" to a constant velocity does not involve "deceleration".

mark kibort

the removal of the force is deceleration relative to the acceleration rate. (rate of velocity change).
weigh yourself in an elevator. (a real fast one that starts out at freefall and then stabilizes at no acceleration) push the down button.
you're weight less. stomach is in your throat.
then, the elevator hits constant speed. your weight on the scale is now your actual weight. as your weight went up, you were decelerating.
even if the elevator would be accelerating at a low rate, the change of acceleration is a deceleration, relative to the initial acceleration. weight transfers all apply to the equations you quote.


your first statement is half true. And, so is your second is true.
But, you had better think about the first statement.
acceleration 1. 30f/s/s
acceletion 2. 10f/s/s
your rate of acceleration has changed 20f/s/s. over what ever time it took to do this, that is your deceleration rate. weight transfer would have transferred based on that difference and the rate that difference occurred.

think of doing a wheelie. you are accelerating just enough to keep the wheel 6" above the ground. because constant acceleration means proportionally greater power, the acceleration starts to go down proportional to speed. relative to the wheelie acceleration , you have decelerated and the front wheel drops (to a force proportional to the associated acceleration weight transfer)

so, brought into this discussion point. your saying that we are accelerating to a corner, and the front brakes are applied WOT LFB, and the nose drops because we are accelerating less, but still accelerating. It drops to a level that is still above steady state (no acceleration, or relative acceleration)

so, I guess we could be both right. the nose could drop relative to the WOT state of acceleration by reducing the relative acceleration rate, but still be accelerating, but the nose would still be higher than 0 acceleration or constant velocity.

winders

Give it up, Mark. You are just plain wrong.

mark kibort

if you are accelerating at 60ft/second/second. your car has some weight transfer to the rear. now, you put on the brakes or remove the acceleration force, just enough to hit constant velocity (no acceleration) (either way). what happens to the weight in the car? it shifts to the front. yes, you didn't decelerate, but the rate of acceleration was changed to 0. this negative forces shifts the weight and change in acceleration (I called it deceleration which isn't really technically correct.)

it all goes back to the statement I made earlier, and I should have been more clear. you cant drop the nose below what is (constant speed), when you are still accelerating as was mentioned in Patrick's post. Yes, you can change that rate of acceleration , and make that acceleration less by a WOT brake tap (LFB) and that will shift the nose down proportional to the rate of acceleration removed. Sorry, I shouldn't have called removal of acceleration , deceleration. my mistake! SORRY!!

how's that.... sound better?

KaiB

Two posts ago, a change in the rate of acceleration was "deceleration"...

One post ago, it isn't.

A page ago, one could not drop the nose of the car with the left foot on the brake if the right was steady state on the throttle.

Now he can.

I'm so confused.

I deleted all of my data and cancelled the last check I wrote to my coach because you told me to Mark.

Now what to do.

Please don't call me a Troll like you did Daniel. He's a good guy and only meant well.

mark kibort

don't post trolling posts and I wont call you out on it.
The entire point of this small part of the discussion was in response to Patrick saying his nose was diving while still accelerating. im sure his nose was diving because he was decelerating. meaning, a negative rate of change of speed. I was incorrect calling change of acceleration, to the negative, deceleration. I was focused on effects of true deceleration. when I am wrong, I will admit it. I miss spoke.
yes, the change of acceleration will shift weight down in the front, even if you are still accelerating, BUT it wont go down further than if you were at a constant speed. That's the point I was trying to defend and had a brain malfunction. again, ill admit when im wrong.

you said, LFB is "always" better. I gave you several examples of why that is not true..... care to recant?

now as far as cancelling your checks.... did you see sundays data?? did you see the areas I was drawing attention to??? clearly there were so many other things to look at vs just the temp of the day.... yet, they dismissed it and could only come back with.. "you haven't driven the track"
really??? that's what the data is for. comparison. you don't need to drive the track to see the obvious... the track didn't change between the two laps, right? anyway you get what you pay for....... woops, I guess you don't..... let the buyer beware!

winders

You are still confused. When you reduce or stop acceleration and you do not reduce velocity, there are no "negative forces".

The statement you "made earlier" was just plain wrong and your new modified statement is nothing like your first statement. In other words, you were wrong and now are trying to save face by "clarifying" your statement. What a joke.

333pg333

I was highlighting two different cases Mark.

In my racecar I might come up to a tight turn and possibly as it goes from positive to negative camber the car tends to want to push wide under constant or increasing accel. So by using LFB it tends to initially tuck or pull the nose down which allows a tighter line and then we can start squeezing the throttle again on late apex / corner exit. I'd have to check the data to see the accel curve but there's no way we can accel as hard or early without the LFB. It may be that while under maintenance throttle and LFB'ing the nose does dip and then will start to rise as accel increases and of course we come off the brake. The LFB in this case isn't for a long duration of course and while braking is braking (ie retardation) this process isn't looked at in the same way as a traditional braking moment.

The second case I was referring to was in my daily driver on the street. I LFB a lot more than RFB, plus I accelerate while LFB'ing quite a lot when turning. I'm sort of steering the car on the brakes if that makes sense. It's just an instinctive thing I've been doing for years. I'm sure it's not good for the pads but this jalopy is not a valued item and this method allows me to sort of pilot it through gaps with more surety than not doing it. It sort of sucks the softly sprung sedan down a little. I haven't given any thought to what is actually happening when I do this, but I do know that it works and allows me to manoeuvre the 4 door p.o.s. through traffic with more accuracy while maintaining some speed. In these instances I can be doing this for a significantly longer period than I would with the racecar on the track.

winders

Huh??

Reducing the rate of acceleration is not a negative. As long as velocity is increasing, you have acceleration. If velocity is reduced at some rate, then you have what you are calling deceleration or could be called negative acceleration.

Think, Mark, think......

KaiB

you said, LFB is "always" better. I gave you several examples of why that is not true..... care to recant?

I made that statement because you begged one of us to do so.

That I would heed your advice on anything jumps the proverbial shark.

Why on earth would I recant a statement merely because you suggested that it may not be true with an odd example using wheelies as a basis?

mark kibort

not odd example. with a high HP car, LFB might be disastrous, but if you are not at the edge, knock yourself out. I can think of many . you don't have a high HP car so don't worry about it. again, you are not reading. the wheelie example is not applicable here. the brake stand analogy is.
so, why would you recant????? because its wrong and incorrect and dangerous to make that statement without thinking about it!!!!! that's why? but you are never wrong, right???

I was saying, relative to the initial rate of acceleration , it was negative. you know where I was going with that. it wasn't a save, I was trying to explain something based on Patrick's observation. and semantics... negative acceleration is deceleration.

again, I agree. stopping acceleration doesn't reduce velocity or give a negative velocity change.

I was thinking of weight transfer, and writing deceleration based on responding to patricks , and Kia's post. yes, ill say it again. less acceleration is not deceleration.... again, I misspoke. I was defending that you cant have a nose drop below normal, while at the same time, accelerating though a corner. yes, a change in acceleration from high to moderate, will drop the nose relative from where it was at the high rate. But , that's not what I believe was said, or experienced. and I responded to it by saying. "deceleration" for the reduction of acceleration. sorry, again, wrong. not a coverup, just wasn't thinking. geezzz!

mark kibort

so, you saw this. still think a coach that looks at this and says, "due to temp" is the reason for a 3mph short fall 3 hours later?
any beginner coach can do the same things doctors do in seeing if you are hurt. compare the other limb. compare the other lap.... see the differences. What I saw is just basic common sense. you don't need to drive the track and by showing you the physics as well, its virtually impossible for 3hp to change the top speed here as much as was seen. that's the beauty of physics..... it can at least, point you in the right direction.
(remember I did the total KE calculation for this run, vs time and saw that the HP required to make this change of speed was about double what could have been seen by the increased temp)
now, are all paid coaches bad??? certainly not. but some don't see the total picture and a lot of them either forgot or never knew some basic physics, or believe wive tales.

mark kibort

if you are NOT a troll, read this and see why someone might see you as one.

http://www.slate.com/articles/health...ychopathy.html

JustinL

I'm glad you admitted that you were wrong because this sentence broke my brain.

KaiB

I'm afraid, my friend, that the thought of opening Slate's "Climate Desk" leaves me a bit ill. Thankfully, cocktails are out in 40 minutes.

"To live is to war with Trolls"....