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

[gotSVT]

Given the loads, it will flex, period. Maybe if the cross section was 3/8" it wouldn't flex, but then your axle would break.

Exactly. You want to strengthen the frame then build a bump stop system that will dissipate the impact over a larger area/provide more dampening. Also I don't see where you take into account the dampening effect of the springs (yeah, even our neg arched stockers but that's another story) and shocks as well as how the load is dissipated through the spring to the spring perches. The bottom line is if you dampen and dissipate the energy over a larger area you'll be ok - up to a certain point. For a good example of this, take a look at a z71 frame (I have one in the parking lot) and you'll find a 6-8" bump stop pad. The difference between collapsing 6-8" of boxed frame on this truck vs 2" of C frame on the Raptor is huge. I've built numerous frames and frame mods to do just this with street rods and lowriders. They've taken years of abuse like hitting a 2" expansion joint with 1" of travel at 80mph.

At the end of the day it will be every man for himself. You'll have to decide what a fix is for you and your driving style. For me, I'm going to make it stronger, get more travel and shock and a better bump stop system. For those of you that are still planning on offroading, I'd really think hard about putting the frame back stock. If you bent it once, you'll likely bend it again.

 

[debate]

uhh...

What I was trying to quantify is the energy in the impulse when the axle bottoms out against the frame rails.

Make sense?

Honestly, no. The Raptors involved look like dumptrucks. Not likely caused by cruising over an enormous speedbump, unless the modular frame broke behind the cab.

 

[Bad company]

Honestly, no. The Raptors involved look like dumptrucks. Not likely caused by cruising over an enormous speedbump, unless the modular frame broke behind the cab.

Look at the pictures of the inside of the beds. They are bowed exactly where the axle hits the bumpstop. Makes perfect sense when you drive at high speed over an 18" tall bump with 6" of suspension left. The impact is HUGE.

Try to accelerate 3,000 pounds (roughly half of your truck) from 0 to 60 ft/s in .0166 seconds. That is an acceleration of 112 Gs. The force required? It is over 168 Tons (337,169 pounds)!

The enourmous speed bump is NASTY!

 

[Bad company]

Exactly. You want to strengthen the frame then build a bump stop system that will dissipate the impact over a larger area/provide more dampening. Also I don't see where you take into account the dampening effect of the springs (yeah, even our neg arched stockers but that's another story) and shocks as well as how the load is dissipated through the spring to the spring perches. The bottom line is if you dampen and dissipate the energy over a larger area you'll be ok - up to a certain point. For a good example of this, take a look at a z71 frame (I have one in the parking lot) and you'll find a 6-8" bump stop pad. The difference between collapsing 6-8" of boxed frame on this truck vs 2" of C frame on the Raptor is huge. I've built numerous frames and frame mods to do just this with street rods and lowriders. They've taken years of abuse like hitting a 2" expansion joint with 1" of travel at 80mph.

At the end of the day it will be every man for himself. You'll have to decide what a fix is for you and your driving style. For me, I'm going to make it stronger, get more travel and shock and a better bump stop system. For those of you that are still planning on offroading, I'd really think hard about putting the frame back stock. If you bent it once, you'll likely bend it again.

Remember I am talking about a very specific condition. A condition where the the bump is 3" taller than the tire flex and remaining suspension can absorb. I ignore the springs and dampers for this reason:

At 60MPH, for there not to be a catastrophic crash between the axle and frame, the frame MUST move up 3" over .0166 seconds. So you need the suspension to supply enough force to move the back of the truck UP 3" VERY QUICKLY. The minimum force required to sucesfully move 3,000 pounds 3" in .0166 seconds? About 170,000 pounds of force! [EDITED to correct unit conversion fail] No change to conclusions.

Building a frame or suspension to withstand bumps larger than available travel at HIGH SPEEDS is pointless due to the loads involved for that reason. NO resonable sized rubber bump stop will serve, nor will any frame reinforcement solve the problem. Just slow down.

The same bump at 20MPH? The average force required to move the truck up 3" is only 18,600 pounds. One ninth the force.

 

[debate]

modular frame fail

Look at the pictures of the inside of the beds. They are bowed exactly where the axle hits the bumpstop.

I looked at the bed of the orange truck. The interior bed condition and the cab-to-bed V are consistant with top frame failure at the middle-to-rear welded joint.

Most of the Raptor suspension is heavy duty, the frame is stock. All the fun parts are working to break the top of that modular frame, even at low speed.

 

[Bad company]

I looked at the bed of the orange truck. The interior bed condition and the cab-to-bed V are consistant with top frame failure at the middle-to-rear welded joint.

Most of the Raptor suspension is heavy duty, the frame is stock. All the fun parts are working to break the top of that modular frame, even at low speed.

Fair enough, I'm not very familiar with the frame construction.

What I can say is that the kickers discribed by the guy who said that a kicker caused his frame failure, and the conditions he described (60 MPH, 18" tall bump) more than capable of damaging any production truck's frame.

Moreover, I can say that the conditions described by the driver are close to an order of magnitude harsher on a frame than any jump I've seen of a Raptor on youtube (maybe that Chevy guy qualifies ).

Additionally, I can say that frame reinforcement, or modified bump stops will not prevent damage associated with the described conditions. If you want to hit an 18" ridge at 60MPH and not fix your truck or walk home, you need more loaded suspension travel. Period.

Finally, I am not concerned that my truck has a weak frame because it won't handle the stated conditions by the driver. No truck in production will. 170,000 pounds of force is going to break something.

 

[debate]

stock F150 frame

Fair enough, I'm not very familiar with the frame construction.

Someone scanned the manufacure's rear frame replacement instructions. Lots of grinding and welding...

From that post, it looks like an F150 frame has front, middle, and rear sections welded together. The Raptor's rear shocks and leaf springs conspire to seperate the rear section from the middle. That shelf on the spacer block, centerpunching the bump-stop, makes the problem worse.

 

[BlueSVT]

Keep in mind that 18" is a rough guess... based on flying by it at 60MPH, so the accuracy is also in question one way or another. Could have been a 12" hill... could have been more than 18"... just a guess. Putting a tape measurer up to the tire, I'm second guessing 18", and would estimate a little smaller than that.

 

[Bad company]

Keep in mind that 18" is a rough guess... based on flying by it at 60MPH, so the accuracy is also in question one way or another. Could have been a 12" hill... could have been more than 18"... just a guess. Putting a tape measurer up to the tire, I'm second guessing 18", and would estimate a little smaller than that.

I assumed that it was flattened to 12" high by the tire in all my calcs. There are a lot of variables at play here. One thing this exercise showed me is how brutal oversized speed bumps can be at speed!

If you approach them at an angle they are much less harsh! Straight on a ridge will be at its worst! Also your vehicle speed SQUARED will directly relate to the impact (60MPH is 4X as bad as 30 MPH).

 

[iceman302]

Did anyone damage a SCrew? I thought I read that the SCrew's have slightly stiffer rear leaf springs. I figure that would help absorb a major impact a little better.