[binarypie]

The kinetic force of your jeep dropping even one inch directly onto the skid measures in many tons of pressure.

I ******* love math and it has been a long time since middle school physics class but here we go.

Pressure = Force / Area
Force = Mass * Acceleration

For the sake of this calculation lets just say my jeep hit terminal velocity because that is fun

Mass = 5400lbs or roughly 2449.4kg
Acceleration = 9.8ms2
Force = 2449.4 * 9.8 = 24004.12N

The skidplate is about 13" by 8" but lets say the area supporting the weight was much smaller. Say 3" by 3". or 0.0625ft2 or roughly metric world 0.006m2.

Area = 0.006m2

Pressure = 24004.12N / 0.006m2

Pressure = 4000686.667 pascals

Pascals to Tons: 407.957 ton/sqm

Now to put that into square inches

0.263197538 ton / sqin

So not quite a ton

For perspective here is the conversion in pounds

526.395076 pound / sqin

 

[gnarlyswine]

There may be an omission there in that the calculation isnt taking into account your kinetic energy from being already in motion rather than accelerating from rest. But then you may well have been at rest making that irrelevant.

 

[binarypie]

There may be an omission there in that the calculation isnt taking into account your kinetic energy from being already in motion rather than accelerating from rest. But then you may well have been at rest making that irrelevant.

I was on a rock and fell onto it. So i wasn't really moving forward. It was more of a sidways slide off of the rock. So I doubt my acceleration was even close to 9.8m/s2

 

[gnarlyswine]

Yes. Even in motion say 2mph would only be about 1400 newtons so its not a big factor really.

I liked physics at school as well. So much that its what I chose to study at university. 30 hours physics lectures a week, 7 hours maths. 3 hours in a lab (was about the only fun part at that level)After one year i was going nuts but thought id stick it out. After two I said eff it and studied music and audio technology instead.
Sample classes that I recall still.
N dimensional vector spaces(dear god why)
Thermodynamics and magnet field theory(make him stop)

Bleh , although I did some welding as an elective that was a nice change.

 

[AvnxScout]

I ******* love math and it has been a long time since middle school physics class but here we go.

Pressure = Force / Area
Force = Mass * Acceleration

For the sake of this calculation lets just say my jeep hit terminal velocity because that is fun

Mass = 5400lbs or roughly 2449.4kg
Acceleration = 9.8ms2
Force = 2449.4 * 9.8 = 24004.12N

The skidplate is about 13" by 8" but lets say the area supporting the weight was much smaller. Say 3" by 3". or 0.0625ft2 or roughly metric world 0.006m2.

Area = 0.006m2

Pressure = 24004.12N / 0.006m2

Pressure = 4000686.667 pascals

Pascals to Tons: 407.957 ton/sqm

Now to put that into square inches

0.263197538 ton / sqin

So not quite a ton

For perspective here is the conversion in pounds

526.395076 pound / sqin

:what:

sent from Skynet

 

[JeepUpKeep37s]

Put in a new alternator, as original died. I have been using a used alternator so now that is my backup. Will carry that on any trip.

My 130w kc driving lights wiring has had some issues in the past. I tried to solder the pig tails to the wiring but there was so much burned sticky residue that I can only account to the wires getting over heated. Looked like 18g. Also noticed the right light not as bright as the left and the bullet connectors were hotter R vs. L. So I redid all the wiring with 14g and put in 2 flood lights mounted at the A pillar.

Happy to report the driving lights appear to be the same brightness, all four lights are turned on with a couple of rocker switches as well these only can come on with high beam as the trigger for the relays. Wiring is all nice, tidy, and bordering on a factory look IMO. 4 x 130w plus 2x100w = 720w, throws some good light but I am sure LED lights could do a better job. Not ready to go for that yet. Once these lights are tired I will upgrade all lights.



Wired a rocker for my OBA as well while I was at it. Can't wait to get started on that project again.

 

[marinespence]

Either I'm drunk or Charles is a ******* rocket scientist...

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[cjcraig7]

I ******* love math and it has been a long time since middle school physics class but here we go.

Pressure = Force / Area
Force = Mass * Acceleration

For the sake of this calculation lets just say my jeep hit terminal velocity because that is fun

Mass = 5400lbs or roughly 2449.4kg
Acceleration = 9.8ms2
Force = 2449.4 * 9.8 = 24004.12N

The skidplate is about 13" by 8" but lets say the area supporting the weight was much smaller. Say 3" by 3". or 0.0625ft2 or roughly metric world 0.006m2.

Area = 0.006m2

Pressure = 24004.12N / 0.006m2

Pressure = 4000686.667 pascals

Pascals to Tons: 407.957 ton/sqm

Now to put that into square inches

0.263197538 ton / sqin

So not quite a ton

For perspective here is the conversion in pounds

526.395076 pound / sqin

Charles, please relate your equation to Mass measured in lbs. so the stupid kids (me) can catch up.

 

[cjcraig7]

Either I'm drunk or Charles is a ******* rocket scientist...

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Or both.

 

[rhljk]

I ******* love math and it has been a long time since middle school physics class but here we go.

Pressure = Force / Area
Force = Mass * Acceleration

For the sake of this calculation lets just say my jeep hit terminal velocity because that is fun

Mass = 5400lbs or roughly 2449.4kg
Acceleration = 9.8ms2
Force = 2449.4 * 9.8 = 24004.12N

The skidplate is about 13" by 8" but lets say the area supporting the weight was much smaller. Say 3" by 3". or 0.0625ft2 or roughly metric world 0.006m2.

Area = 0.006m2

Pressure = 24004.12N / 0.006m2

Pressure = 4000686.667 pascals

Pascals to Tons: 407.957 ton/sqm

Now to put that into square inches

0.263197538 ton / sqin

So not quite a ton

For perspective here is the conversion in pounds

526.395076 pound / sqin

Think the equations that matter:

skid_plate + rock = a_drive_home
no_skid_plate + rock = big_mess_&_flat_bed_trip_home

Sort of hard to imagine that the stock oil pan would have held up to the same hit, even if the skid plate was defective in a major way. Whatever the hassle and cost of replacing the skid plate, it looks like you came out a head in this case.

 

[binarypie]

Think the equations that matter:

skid_plate + rock = a_drive_home
no_skid_plate + rock = big_mess_&_flat_bed_trip_home

Sort of hard to imagine that the stock oil pan would have held up to the same hit, even if the skid plate was defective in a major way. Whatever the hassle and cost of replacing the skid plate, it looks like you came out a head in this case.

Yup I won regardless but I'm that is no excuse for the way I was treated on the phone.

 

[cjcraig7]

When I was in middle school, I was usually busy trying not to get kicked out (after I was caught trying harder to get kicked out). If I recall, my math teacher was an old hag, but my English teacher was hot! So, as you may imagine, my mind was mostly trained on an illusion that someday that teacher and I would be caught doing the naughty thing, behind the dumpster in back of the cafeteria. Though my fantasies didn’t bring me fame and fortune via my writing or interpretative skills, they did keep me focused on the important things (hold that thought until the end). As such, though my intellect with respect to physics stops at the terminal velocity of 38s dropping out of a freshly unhinged bra and onto my forehead, with a special visual to include Newton’s Third Law, I will bring my real world, and at least partly, twisted logic into this discussion.

I read through the above information and attempted to understand the theories, data points, and formulae, but frankly, it appears that some, if not all of the post, for a lack of a better phrase, “is all ****** up”. It appears that either there is a failure to understand what is happening on the trail, or an intentional talking down to the trailer trash. I will assume the former, and offer the following data points to support my theories, data points, and findings.

The theorist stated “entire” weight of the vehicle when, in fact, he should have used only the sprung weight of the front axle, less the factor of a controlled suspension unload. Nowhere near the entire weight of the vehicle was resting on, or played into the impact damage from that rock. (“weight”)

Further he used 3” x 3” or 9 square inches as the impact area on the skid, when in fact, that could only be represented if two perfectly flat areas happened to exist on imperfect and uneven surfaces, which would be almost impossible with the inclusion of a rock. I theorize that a more logical and suitable surface would not exceed 1 square inch and likely much smaller than that. (“impact area”)

And important factor, the drop distance of the weight was excluded in the theory (possibly because it may have buried within terminal velocity, dunno); I find it most important. For the drop distance, I used aired down 37”s or a 17 inch radius plus 4 inch from axle center line to the pan. So the drop distance if you had a tire on a rock and slipped off and dropped to typical pan height or approximately 21”. (“drop distance”)

Another important factor, the time it took to get the in-motion weight to stop was not represented in the equation. This is an important factor as it directly equates to Impulse Force (some would refer to Shock) transferred to the skid, and thusly, must be considered in the causation of the broken weld. I will use 1/10th of a second for the purposes of this discussion. In determining if the weld failure was a manufacturing defect, EVO would want to understand this force. (“time to stop”)

So this is where I come down, with what we know (I may be wrong because my mind is partly focused on ***** right now – Jerry Springer is about to come on):


Real World Data Points (actual numbers may vary greatly):

“weight” = 2700 lbs
“impact area” = 1 sq in
“drop distance” = 21 in
“time to stop” = .1 sec

Static pressure on impact area (after drop):
2700 lbs / sq in

Impulse pressure on impact area (during deceleration from drop to fully stopped):
1 Newton (N) = .2248 lb
Weight N = Force (F) = Mass (m) x Acceleration (a)
a = 9.8m/sec sq
Mass (m) = 1225.6kg

Impulse Force = change in momentum (delta-p) / change in time (delta-t)
delta-p = (m x Final Velocity (v1) ) - (m x Initial Velocity (v0) )
v1 = 0, so delta-p = -(m x v0)

v0 squared = (2 x a x Displacement (S) )
S = 21 in, which is .5334 m
v0 = 3.233 m/s

delta-p = - (1225.6kg x 3.233m/s) = -3962.4kg m/s (negative because it was stopping as opposed to starting)

Impulse Force (F) = delta-p / delta-t = (-3962.4kg m/s) / .1s = -39624 N
F = -39624N or 8907 lbs

area = 1 sq in, so impulse pressure (or shock transferred to the weld) = 8907 lbs / sq in


Because we don't really know how long it took to come to rest on the rock, we can change that number and get different results. For instance, if the time to stop were changed from 1/10 second to 1/100 second the impulse pressure (shock) would increase from 8907 lbs / sq in to 89070 lbs / sq in. Imagine a tailbone drop on a mattress (yeah! In my Couples Therapy – yoga guy voice)) compared to a park picnic table or kitchen countertop.

This discussion truly represents the real reason why, according to our friend Extreme Gary, geeks should get laid more often, and in fact, more proof that everything, and I mean everything, revolves around the female body.

In summation, adjusting for weight, drop and other variables, I believe that Alex was more right than wrong; in fact, his guess may be close to exact.

 

[binarypie]

When I was in middle school, I was usually busy trying not to get kicked out (after I was caught trying harder to get kicked out). If I recall, my math teacher was an old hag, but my English teacher was hot! So, as you may imagine, my mind was mostly trained on an illusion that someday that teacher and I would be caught doing the naughty thing, behind the dumpster in back of the cafeteria. Though my fantasies didn’t bring me fame and fortune via my writing or interpretative skills, they did keep me focused on the important things (hold that thought until the end). As such, though my intellect with respect to physics stops at the terminal velocity of 38s dropping out of a freshly unhinged bra and onto my forehead, with a special visual to include Newton’s Third Law, I will bring my real world, and at least partly, twisted logic into this discussion.

I read through the above information and attempted to understand the theories, data points, and formulae, but frankly, it appears that some, if not all of the post, for a lack of a better phrase, “is all ****** up”. It appears that either there is a failure to understand what is happening on the trail, or an intentional talking down to the trailer trash. I will assume the former, and offer the following data points to support my theories, data points, and findings.

The theorist stated “entire” weight of the vehicle when, in fact, he should have used only the sprung weight of the front axle, less the factor of a controlled suspension unload. Nowhere near the entire weight of the vehicle was resting on, or played into the impact damage from that rock. (“weight”)

Further he used 3” x 3” or 9 square inches as the impact area on the skid, when in fact, that could only be represented if two perfectly flat areas happened to exist on imperfect and uneven surfaces, which would be almost impossible with the inclusion of a rock. I theorize that a more logical and suitable surface would not exceed 1 square inch and likely much smaller than that. (“impact area”)

And important factor, the drop distance of the weight was excluded in the theory (possibly because it may have buried within terminal velocity, dunno); I find it most important. For the drop distance, I used aired down 37”s or a 17 inch radius plus 4 inch from axle center line to the pan. So the drop distance if you had a tire on a rock and slipped off and dropped to typical pan height or approximately 21”. (“drop distance”)

Another important factor, the time it took to get the in-motion weight to stop was not represented in the equation. This is an important factor as it directly equates to Impulse Force (some would refer to Shock) transferred to the skid, and thusly, must be considered in the causation of the broken weld. I will use 1/10th of a second for the purposes of this discussion. In determining if the weld failure was a manufacturing defect, EVO would want to understand this force. (“time to stop”)

So this is where I come down, with what we know (I may be wrong because my mind is partly focused on ***** right now – Jerry Springer is about to come on):


Real World Data Points (actual numbers may vary greatly):

“weight” = 2700 lbs
“impact area” = 1 sq in
“drop distance” = 21 in
“time to stop” = .1 sec

Static pressure on impact area (after drop):
2700 lbs / sq in

Impulse pressure on impact area (during deceleration from drop to fully stopped):
1 Newton (N) = .2248 lb
Weight N = Force (F) = Mass (m) x Acceleration (a)
a = 9.8m/sec sq
Mass (m) = 1225.6kg

Impulse Force = change in momentum (delta-p) / change in time (delta-t)
delta-p = (m x Final Velocity (v1) ) - (m x Initial Velocity (v0) )
v1 = 0, so delta-p = -(m x v0)

v0 squared = (2 x a x Displacement (S) )
S = 21 in, which is .5334 m
v0 = 3.233 m/s

delta-p = - (1225.6kg x 3.233m/s) = -3962.4kg m/s (negative because it was stopping as opposed to starting)

Impulse Force (F) = delta-p / delta-t = (-3962.4kg m/s) / .1s = -39624 N
F = -39624N or 8907 lbs

area = 1 sq in, so impulse pressure (or shock transferred to the weld) = 8907 lbs / sq in


Because we don't really know how long it took to come to rest on the rock, we can change that number and get different results. For instance, if the time to stop were changed from 1/10 second to 1/100 second the impulse pressure (shock) would increase from 8907 lbs / sq in to 89070 lbs / sq in. Imagine a tailbone drop on a mattress (yeah! In my Couples Therapy – yoga guy voice)) compared to a park picnic table or kitchen countertop.

This discussion truly represents the real reason why, according to our friend Extreme Gary, geeks should get laid more often, and in fact, more proof that everything, and I mean everything, revolves around the female body.

In summation, adjusting for weight, drop and other variables, I believe that Alex was more right than wrong; in fact, his guess may be close to exact.

We should also take into account that the fall did not occur in a vacuum and the jeep was never in free-fall which means we need to coefficient of both drag from the particles in the air and friction of a 35" tire against some sort of rock which is not granite.

When I get the oil pan off I'll take more photos and measurements so we can do a forensic analysis of the impact and attempt to get a closer assumption of what actually happened.

I am however glad that my over-simplification of the events caused you to spend half a day researching the mathematics and physics behind such an event. I look forward to future discussions such as these.

I've been toying with the idea of doing the math behind JMac's suspension as a fun way to spend a saturday afternoon. It might also show some room for improvement beyond changing your front bumper.

 

[DiscoBayJoe]

So this graph shows that paper beats rock:

But it looks like the old game needs a new modification showing Rock beats Welds.

 

[cjcraig7]

We should also take into account that the fall did not occur in a vacuum and the jeep was never in free-fall which means we need to coefficient of both drag from the particles in the air and friction of a 35" tire against some sort of rock which is not granite.

Research? Um no.... both drag, and the friction of the tire were taken into account, then discounted as irrelevant. That is clear in my theory.

And, just so you are clear, I employ a staff of Engineers who just had a good chuckle, as they know that I am not nearly smart enough to debate with you. Of course, they don't spend much time on the trail either.,

Hit the books, the trail, and go get laid, grasshopper.

 

[BlackToad]

C-gussets, front axle sleeves, control arm skids, new front driveshaft (to replace broke down original one), tow hook mount point, awesome custom sway bar skid and equally awesome front turn signals embedded in bumper.

 

[ThwopKing]

I didn't do a damn thing but put gas it in....now the gas cap pops off at will and the c.e.l. is on.
Sent with Autoguide while watching chicks get naked.

 

[KevinJBurt]

C-gussets, front axle sleeves, control arm skids, new front driveshaft (to replace broke down original one), tow hook mount point, awesome custom sway bar skid and equally awesome front turn signals embedded in bumper.

You know the saying pics or it didn't happen!

View attachment 78146
I didn't do a damn thing but put gas it in....now the gas cap pops off at will and the c.e.l. is on.
Sent with Autoguide while watching chicks get naked.

Buy a new gas cap...


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[ThwopKing]

I'm not buying crap. ... it's still under warranty lol

Sent with Autoguide while watching chicks get naked.

 

[gnarlyswine]

Installed my oil pan freefall rapid impulse transfer prevention device.