Front cross member/skid mount rebuild

[Humble Leader]

Thanks for your interest! Nothing major but better than what's been posted here lately.. i hit the original hard enough to almost break my nose and teeth out on the wheel. Yes, I have a recalled airbag that I don't care about fixing. So I'm confident this is plenty tough. Welding high pressure nuclear pipe has me used to every weld joint being x-rayed and no imperfections are tolerated. Or bye bye. So I know the quality of my welds are A1 from experience.

I will add final pics when I get to it. Waiting for paint to cure..

lol this right here is proof that the argument of "the front tow loops can't be used for recovery because the radiator support will rip or bend at the arms" . this is what a lot of the aftermarket recovery points use as a selling feature and in their design

you put the full force of your 4runner which is probably over 5,000lbs with that steel bumper etc into a stump at speed and only dented it without the whole support bending backwards at the arms

 

[Grug556]

Thanks for your interest! Nothing major but better than what's been posted here lately.. i hit the original hard enough to almost break my nose and teeth out on the wheel. Yes, I have a recalled airbag that I don't care about fixing. So I'm confident this is plenty tough. Welding high pressure nuclear pipe has me used to every weld joint being x-rayed and no imperfections are tolerated. Or bye bye. So I know the quality of my welds are A1 from experience.

I will add final pics when I get to it. Waiting for paint to cure..

Hell yeah!! I love it. Nice work and nice solution!!!!

 

[Grug556]

lol this right here is proof that the argument of "the front tow loops can't be used for recovery because the radiator support will rip or bend at the arms" . this is what a lot of the aftermarket recovery points use as a selling feature and in their design

you put the full force of your 4runner which is probably over 5,000lbs with that steel bumper etc into a stump at speed and only dented it without the whole support bending backwards at the arms

Some cursed engineer will come around shortly and critique my crude calculations:bump2:. Anyhow say you were driving 30mph and hit the stump you would with a 5000lb vehicle have roughly 150 000lbs of impacting force on the cross member. Sizeable impact force.

 

[Humble Leader]

Some cursed engineer will come around shortly and critique my crude calculations:bump2:. Anyhow say you were driving 30mph and hit the stump you would with a 5000lb vehicle have roughly 150 000lbs of impacting force on the cross member. Sizeable impact force.

it's been a while since I was in school. but we can use the equations for kinetic energy and work and solve for force. some rearranging implies:

horizontal impact force applied to the cross member is F = (1/2 * mass * velocity^2) / distance

mass = 5000lbs or about 2268 kg
velocity = 30 mph or about 13 metres per second
distance to stop = about 2 inches it looks like is indented on that cross member or about 0.0508 metres

F = 3.77 million Newtons. or about 850 thousand lb feet of force. now obviously angle, road terrain, any trim pieces that slowed impact etc etc . and if you actually broke through the stump as well significantly changes the results. but I believe the equations above are the right ones to use here. literally if you hit that stump going horizontally at 30mph, and it literally stopped your rig dead in its tracks and only dented the support a couple inches then that is A LOT of force transferred to the vehicle. I suspect you tore that stump right apart lessening the impact force on your truck, or that is one strong-ass stump man! or you were going slower than you thought!

 

[Jakeepoo3]

it's been a while since I was in school. but we can use the equations for kinetic energy and work and solve for force. some rearranging implies:

horizontal impact force applied to the cross member is F = (1/2 * mass * velocity^2) / distance

mass = 5000lbs or about 2268 kg
velocity = 30 mph or about 13 metres per second
distance to stop = about 2 inches it looks like is indented on that cross member or about 0.0508 metres

F = 3.77 million Newtons. or about 850 thousand lb feet of force. now obviously angle, road terrain, any trim pieces that slowed impact etc etc . and if you actually broke through the stump as well significantly changes the results. but I believe the equations above are the right ones to use here. literally if you hit that stump going horizontally at 30mph, and it literally stopped your rig dead in its tracks and only dented the support a couple inches then that is A LOT of force transferred to the vehicle. I suspect you tore that stump right apart lessening the impact force on your truck, or that is one strong-ass stump man! or you were going slower than you thought!

That is the correct formula to calculate impact force assuming the impacting mass was rigid, zero deflection. To get the correct impact force we need to know the total combined deflection of the impact mass (stump) and impact system(cross member). I'm sure the stump deformed enough to absorb a large amount of the force. And the cross member is designed to deflect, as it did, purposely to minimize impact. I don't think I was going that fast, closer to 15-20. Enough to knock me out for a moment and cloud my memory of it. My kind of entertainment!!

 

[Jakeepoo3]

lol this right here is proof that the argument of "the front tow loops can't be used for recovery because the radiator support will rip or bend at the arms" . this is what a lot of the aftermarket recovery points use as a selling feature and in their design

you put the full force of your 4runner which is probably over 5,000lbs with that steel bumper etc into a stump at speed and only dented it without the whole support bending backwards at the arms

The tin foil radiator support has nothing to do with that cross member.. what do you mean. No the legs of the cross member to the frame did not deform at all.

 

[Humble Leader]

That is the correct formula to calculate impact force assuming the impacting mass was rigid, zero deflection. To get the correct impact force we need to know the total combined deflection of the impact mass (stump) and impact system(cross member). I'm sure the stump deformed enough to absorb a large amount of the force. And the cross member is designed to deflect, as it did, purposely to minimize impact. I don't think I was going that fast, closer to 15-20. Enough to knock me out for a moment and cloud my memory of it. My kind of entertainment!!

that is one strong stump though lol

The tin foil radiator support has nothing to do with that cross member.. what do you mean. No the legs of the cross member to the frame did not deform at all.

I believe I meant to say cross member not radiator support

 

[Ezlife45]

I'm assuming this is sarcasm.. by the way I also have a Masters degree from the University of Arkansas in bioelectrical engineering.. my skills are backed with knowledge pro. Thanks for the relevant comment. Always a hater on these things I guess. Does the bottom of your 4runner even have a scratch on it cheif?

Dude,

Actually it was not sarcasm. I have MSME and was complimenting your pipefitting skills. I like to tinker with a welder too and it takes some practice to do what you did.

This is sarcasm "CHIEF not Cheif"

 

[Jakeepoo3]

Dude,

Actually it was not sarcasm. I have MSME and was complimenting your pipefitting skills. I like to tinker with a welder too and it takes some practice to do what you did.

This is sarcasm "CHIEF not Cheif"

Thanks sorry about that..