Houston we have a problem! (the bent frame thread)

[Bar]

"There is a slight bulge there already from the get go.....it protrudes out to the sides just a bit." :********:

Just to change the mood a little...I had to pull the ********.

Thanks. I saw that from an earlier pick on the bulge, but some of the damaged pics do show a twist to it. I'll have to make a trip to my local dealership.

 

[Bad company]

It's easy to say that, after your calculations... However, this was never seen in mass numbers before and people do MUCH harder things with these vehicles that we did.

That, and your calculations are theoretical based on "estimated" numbers... Which you're now preaching as fact.

Of course a bent frame is mechanical damage, I'm illustrating that NOTHING else was affected in any way aside from the frame... I would expect to see other stuff fail long before a frame would, in my experience with many other off road vehicles.

This doesn't need to be a debate, I have my opinion on how we drove the trucks, you have yours... Let's leave it at that and stop polluting these informative threads.

If others drove their vehicles MUCH harder as you stated above, why did yours break?

This is the extent of my calculations: 6" of available suspension versus an 18" tall kicker AS POSTED at 60MPH. Nothing complicated here. At those speeds, you are going to crash your suspension. This isn't guess work. Ask anyone who understands spring rates, damping, and momentum. The impact is obviously between the axle and the bumpstops, and transfers the force to GASP! the part of the frame that buckled.

No more guess work required. No pollution either. I USED FACTS POSTED AS TO HOW THE VEHICLES WERE DRIVEN.

 

[bstoner59]

If you drive a car built for track use and you are driving on a track you are driving it as it's intended. If you over-drive that car and go too fast into a corner, go off the track into a sandpit or into the wall it doesn't mean there is a design flaw...You have to use your head when driving off-road and know what the truck can and can't handle. If there is a kicker coming up you can't just slam the throttle down and hope for the best...just common sense. You can only drive as fast as you can stop.

 

[Bad company]

Yes, Ollie, I certainly do own a Raptor. It's a fine set of street wheels. I'll trade it when SVT produces the F250 Raptor. That's the frame platform needed to achieve the expected performance without trashing Ford's reputation.

I'll look for the pics of your Raptor, it's the pink one, yes?

Enjoy your F250 Raptor, just be aware that it will be possible to break that one too. The Raptor is such a nice vehicle, that I can't imagine a current owner being so down on it. Guess I was wrong. Then calling it a "great street vehicle", lmao; between it and the Power Wagon, and maybe Wrangler, it is the finest off-road mass production vehicle currently.

I dunno who Ollie is, but it would be the first pink Raptor I've seen.

Good response to a thourough analysis given the stated conditions, existing suspension geometry, accounting for momentum, acceleration, velocity, mass, and surface profile.

 

[BlueSVT]

If others drove their vehicles MUCH harder as you stated above, why did yours break?

That's my point.

Go on youtube, and watch the idiots do 10ft high jumps, stuff their front ends, bottom the entire trucks out... guess what? No bent frame afterwards! In most cases, the OPPOSITE happens, and the bed bends upward making contact with the corner of the cab. Now THAT is abuse, in MY personal opinion. The truck was NOT marketed as a truck capable of doing 10 foot high jumps at 80 MPH... (although Ford's website has no less than 5 photos of the Raptor with all 4 wheels off the ground).

A question for you: Do you own a Raptor, and if not, have you ever been in one off-road?

 

[GRT4DRT]

Good response to a thourough analysis given the stated conditions, existing suspension geometry, accounting for momentum, acceleration, velocity, mass, and surface profile.

As Gilligan would say:

"Good stuff Professor. Now when are you gonna build a frickin radio and get us of this GD island!!!"

 

[Bad company]

That's my point.

Go on youtube, and watch the idiots do 10ft high jumps, stuff their front ends, bottom the entire trucks out... guess what? No bent frame afterwards! In most cases, the OPPOSITE happens, and the bed bends upward making contact with the corner of the cab. Now THAT is abuse, in MY personal opinion. The truck was NOT marketed as a truck capable of doing 10 foot high jumps at 80 MPH... (although Ford's website has no less than 5 photos of the Raptor with all 4 wheels off the ground).

A question for you: Do you own a Raptor, and if not, have you ever been in one off-road?

I do own a Raptor, and have had it airborne, sideways, and otherwise engaged in off road hoonage. Before I had the Raptor I've owned two Wranglers (with their fragile sway bar links). That's why i'm so passionate about understanding the failures.

A 10' jump is MUCH less stressful on the suspension than those kickers at 60 MPH. I agree that the marketing hasn't stated everything that the truck is designed to do, and you guys learned the hard way how nasty the kickers are. It is not intuitive. I would also have learned the same lesson that you did, I'm sure.

Initial velocity on a 10' jump is 25.4 ft/s compression and it slows as the shocks work (and you get FULL range on the suspension because it's extended).

Initial velocity on the kicker is about 60 ft/s and is really doesn't slow as the shocks work because there is no time, AND it starts with the suspension already loaded (the REAL KILLER).

The two cases are completetly different. The other problem is that suspension only works until it bottoms out, then the forces climb extremely quickly. The bump stop is designed as a last ditch effort to increase suspension stiffness to avoid a collision. When the impact has enough energy to overcome the bump stops, than you will cause damage.

I would argue that those getting 10' of air are probably exceeding what Ford's intended use is as well. Apparently the truck is still tough enough for that.

 

[linexsa]

I do own a Raptor, and have had it airborne, sideways, and otherwise engaged in off road hoonage. Before I had the Raptor I've owned two Wranglers (with their fragile sway bar links). That's why i'm so passionate about understanding the failures.

A 10' jump is MUCH less stressful on the suspension than those kickers at 60 MPH. I agree that the marketing hasn't stated everything that the truck is designed to do, and you guys learned the hard way how nasty the kickers are. It is not intuitive. I would also have learned the same lesson that you did, I'm sure.

Initial velocity on a 10' jump is 25.4 ft/s compression and it slows as the shocks work (and you get FULL range on the suspension because it's extended).

Initial velocity on the kicker is about 60 ft/s and is really doesn't slow as the shocks work because there is no time, AND it starts with the suspension already loaded (the REAL KILLER).

The two cases are completetly different. The other problem is that suspension only works until it bottoms out, then the forces climb extremely quickly. The bump stop is designed as a last ditch effort to increase suspension stiffness to avoid a collision. When the impact has enough energy to overcome the bump stops, than you will cause damage.

I would argue that those getting 10' of air are probably exceeding what Ford's intended use is as well. Apparently the truck is still tough enough for that.

quick question, i read all of your math and it all seems very logical. ive been following this thread for a couple of days, and agree with all of your reasoning. my only question is, when you hit a bump, the suspension compresses and rebounds, sending the rear of the truck into the air once the bumpstop bottoms out, when you drop it off a 56' drop, the truck has no where to go, wouldnt this change the math a little? am i explaining my question right?

 

[Bad company]

As Gilligan would say:

"Good stuff Professor. Now when are you gonna build a frickin radio and get us of this GD island!!!"

The way off this island:
1. Slow down for big bumps.
2. Make sure suspension travel is > than bumps and go fast.
3. Hit big bumps at a sharp angle or make sure they are gradual rises.

 

[Bad company]

quick question, i read all of your math and it all seems very logical. ive been following this thread for a couple of days, and agree with all of your reasoning. my only question is, when you hit a bump, the suspension compresses and rebounds, sending the rear of the truck into the air once the bumpstop bottoms out, when you drop it off a 56' drop, the truck has no where to go, wouldnt this change the math a little? am i explaining my question right?

Great question. I struggled with explaining it clearly.

The comparison is equal if you only allow the drop to compress the suspension 12". (and then somehow stop the fall/truck)

The main issue here is the time the suspension has to work on the truck to "move it up". Lets look at it this way, (which is another way to analyze it):

Basically in .0166 seconds the bottom of the tire moves up 12" (forced to by the ground). This is 1/60th of a second. If you assume that the tire squashes 3", the suspension takes up 6" (the amount it has when loaded), that means to avoid a nasty crash between the steel axle and steel frame, you need the suspension to move the truck up by 3".

Ok but how reasonable is that? Can't the suspension move the truck up 3" in that timeframe? It can't, and here is why:

The mass of the truck on the rear suspension is roughly 3,000 pounds. Lets assume that the force supplied by the suspension to the truck is constant (we know it isn't, but this will give us the SMALLEST force required).

x = .25' (3")

a = constant because force is constant

t = .0166

so knowing that v_initial is zero:

x = 1/2 * at^2

leaves a = 1814.5 ft/s^2

Great now what? Well this acceleration is equal to 56 "g"s. So the suspension must exert 56 times the weight of the truck on the rear axle to move it up 3" in that amount of time OR about 170,000 pounds of force MINIMUM.

There is no way this suspension is exerting more force than the weight of an M1A1 main battle tank on your truck. Ergo, you have a big, nasty impact between the rear axle and the frame rail, which kinks the frame (and ANY frame would kink), and makes you a Raptor with the dump truck look.

Better explanation?