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When you dont trust the bumper "guards"


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But want to keep the stock bumper...

 

You build the KNEE CRUSHER :grin:

 

Is it safe to say I have the only chromoly push bumper?

 

All bolted to the factory bumper locations.

 

1-1/2 square tubing (body color matched) and a section of 2" SOLID chromoly round stock. :)

 

RUbumper01.jpg

 

Next is a set of 5" round pencil beam 100 watt lamps.

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Nice looking Bumper..

 

on a side note,what's the bar below the bumper for ? my brat has one too and it looks like something was welded to it on both ends,was that for factory brush guard or something ?

 

All the 4wd EA81's had those. It ties in under the bumper to the mounts for those "gaurds" he removed to make his new bar.

 

Protects the lower radiator core support. It's a pretty stout bar, attached to some plate that wraps under and bolts to the underside of the radiator core support. I wish they had equipped EA82 cars with something like that.

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they arnt that stout.I bumped into a stump at 5 MPH and bent mine.Then I made the mistake of thinking it was a recovery point and ripped it off when I got stuck once.

 

Dude that happened to me on my old wagon as well only i was going like 20 and it took out the oil gauge screw.

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btw what does your knee crusher mount to?

 

It slips right into the factory bumper mounts, and is bolted to the unibody using factory hardware.

 

RUbumper02.jpg

 

I'd be interested in one or both of your over riders. PM me if you're interested in getting rid of them

 

Sorry, they are spoken for, and will be going on a '84 Brat here in town.

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  • 2 weeks later...
  • 2 months later...

Are you honestly doubting the strength of 2" solid chromoly?? :lol:

 

On a 2500lb Subaru??? :popcorn:

 

 

 

It doesnt matter dude. I could run this car into a brick wall at 100mph and there wouldnt be a scratch, let alone a bend in that solid chromoly bar.

 

The rest of the car however, wouldnt have a straight body panel on it.

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Not doubting the strength of the chromoly, I work with metal for a living so i understand it. Just saying that a tube of the same material and size would be stronger.

 

Wait, will that car DO 100?

Edited by wentz912
Add smart arse remark.
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Just saying that a tube of the same material and size would be stronger.

 

You need to go back to school.

 

Shouldnt you have learned this in what, junior high?

 

Basic physics. A solid rod of diameter X will ALWAYS be stronger than a tube of diameter X, given both are constructed of the same material.

 

What you THINK you are talking about is a pipe of WEIGHT x will be stronger than a solid rod of WEIGHT x.

 

 

 

bottom line, if the materials and the diameter remain the same, a solid rod will ALWAYS be stronger in every way possible. Only downside is additional weight.

 

 

And no, this car cannot do 100mph. It has seen 85 though. :D

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You need to go back to school.

 

Shouldnt you have learned this in what, junior high?

 

Basic physics. A solid rod of diameter X will ALWAYS be stronger than a tube of diameter X, given both are constructed of the same material.

 

What you THINK you are talking about is a pipe of WEIGHT x will be stronger than a solid rod of WEIGHT x.

 

 

 

bottom line, if the materials and the diameter remain the same, a solid rod will ALWAYS be stronger in every way possible. Only downside is additional weight.

 

 

And no, this car cannot do 100mph. It has seen 85 though. :D

 

 

down vote

http://www.physicsforums.com/archive/index.php/t-37701.html says

"Most of the strength of a cylinder comes from the outer portions. I think the contribution goes like the cube of the radial position. So, if you took a solid rod and drilled out a half the volume from the center, you do not lose half the strength. Strength to weight ratio is better for a hollow pipe than a solid rod."

The definition for the second moment of inertia I c for a filled and hollow cylinder can be found on http://en.wikipedia.org/wiki/Second_moment_of_area:

I c = A y 2 dxdy= R 0 2π 0 r 2 dϕrdr=πr 4 4

 

The surface area of the filled cylinder is:

A=πr 2

 

Compare filled and hollow cylinder of equal mass:

s c =I c A =r 2 4

 

 

, cylinder with fractional internal radius r i =xr o and x<1 :

s h =I h A =r 4 (1x 4 ) 4r 2 (1x 2 ) =r 2 (1x 2 )(1+x 2 ) 4(1x 2 ) =r 2 (1+x 2 ) 4 >s c

 

 

.

This means a hollow cylinder is stronger than a rod of equal mass and the same material. A hollow cylinder with a bigger inside diameter is better. In the limit x1 the hollow cylinder is twice as strong. Note that this limit isn't physically viable as it would be an cylinder with infinite radius and infinitesimally thin wall. However it is useful to define the upper limit of the second moment of inertia. I didn't expect the increase in strength only a factor of two.

Edited by monstaru
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take any working drill and 2 new bits.

drill thru the hollow rod with one new bit and time it with stopwatch

drill thru the solid rod with new identical bit, time it with stopwatch

 

which is stronger :):drunk:

 

if you don't break bit 2 then you may say both are equal but i know which is better.

 

 

 

 

or take both rods, clamp in a shop vice

 

take sledge hammer, and whack at them. which one is better?

 

Or which tree will be stronger, one with a hollowed out rotted stump, or one that is solid.

 

Now, I do know something about baseball bats, and the reason MLB uses wood is cause wood doesnt dent, it breaks but not often, every hit on aluminum would dent the bat. this should go to off topic though.

Edited by bheinen74
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Thanks for all the gibberish monstaru.

 

All that really had has to be said, is what I said to begin with...

 

This means a hollow cylinder is stronger than a rod of equal mass and the same material.

 

 

Key word for the day? MASS

 

:popcorn:

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