RockRangerII the build up.

[IZwack]

I think a grade5 is good enough in this situation.. two 1/2" grade5 bolts should be able to withstand about 9k lbs of sheer on that one side.

I think we also have to keep in mind that in this situation, assuming the bolts are at proper torque specs, all of the stress is not placed directly onto the bolt - but rather, most of the stress is handled by the two mating surfaces which the bolt is "clamping" together. A good example of this are the "high steer" arms where the torque from the tie rods are not directed to the high-steer arm's studs, but rather the surface between the high steer arms and the flat-top steering knuckle. The studs, and its accompanying nuts, is merely there to provide the proper clamping force.

 

[Stic-o]

grade 8 may be stronger but grade 5 does not shear as easy....

Thank You

 

[redranger4.0]

grade 8 may be stronger but grade 5 does not shear as easy....

sorry but this is false. its a common misconception that a grade 5 is better in shear because it bends first. this is wrong. if you want to read why pick up a book on fasteners or just read the Billavista Article on pirate.

http://www.pirate4x4.com/tech/billavista/NutsandBolts/index.html

 

[Stic-o]

There is also real world experience. I have seen many times where a 5 will stretch and can be replaced vs. a 8 they just snaps and takes other parts with it. I'm not saying don't use grade 8's but just pick and chose what to use for what application. I use both 5 & 8's

 

[410Fortune]

geesh! Pirate was where I learned about grade 5 vs 8 a couple years back and now this? I wish the internet would make up its mind! hahaha

All my skid plates are held on with grade 5 hardware, likely jsut because thats what I had llaying around, no problems yet!

 

[redranger4.0]

There is also real world experience. I have seen many times where a 5 will stretch and can be replaced vs. a 8 they just snaps and takes other parts with it. I'm not saying don't use grade 8's but just pick and chose what to use for what application. I use both 5 & 8's

i just did a lab on this in my strengths class, we tested grade 8 vs grade 5. grade 5 bent and then sheared. grade 8 did not bend it just sheared, but at a much higher level

 

[410Fortune]

so 8 is stronger in all cases?
but not always needed....

cool!

 

[Stic-o]

i just did a lab on this in my strengths class, we tested grade 8 vs grade 5. grade 5 bent and then sheared. grade 8 did not bend it just sheared, but at a much higher level

That's my point! a 5 will bend then you know you have a problem, vs. a 8 you will just keep on abusing it till it snaps. Just out of curiocity do you know what the shear is on a 5 vs. a 8? Also What about 10 or 12's I can get these from tha Caterpillar dealler down the road a bit

 

[redranger4.0]

so 8 is stronger in all cases?
but not always needed....

cool!

yea if the bolt isnt going to see anything over 80000psi then there is no need for a grade 8 and a grade 5 will be just fine. i get a discount on fasteners so i tend to buy grade 8 for everything, no matter the strength requirment

 

[410Fortune]

well I would suspect the foces involved vary with size of the hardware, you think its a percentage?

 

[redranger4.0]

well I would suspect the foces involved vary with size of the hardware, you think its a percentage?

yes the diameter of the hardware is what makes the biggest difference. we test 1/2" vs 5/8" grade 5 against each other. the 1/2" shear while the metal we were pulling on broke before the 5/8" sheared and thats only .125 of an inch

kinda similar to tube strength. people think that wall strength is the major factor for tube strength, but in reality a 2.0 .25 wall tube is stronger then a 1.5 .375 not to mention lighter.

 

[redranger4.0]

That's my point! a 5 will bend then you know you have a problem, vs. a 8 you will just keep on abusing it till it snaps. Just out of curiocity do you know what the shear is on a 5 vs. a 8? Also What about 10 or 12's I can get these from tha Caterpillar dealler down the road a bit

the problem is if that bolt regularly sees forces great enough to bend it then it just becomes a pain in the ass to replace it when if you had a grade 8 it would withstand the forces alot longer. I dont know the shear strength off the top of my head but ill try and figure it out in my stengths book.

 

[Jefe]

Regardless, those bolts are never going to see enough force to shear. 90% of the forces on the skid plate will be pushing it towards the frame, transfering all of that force directly from the skid to the frame, no bolts involved, because the skid plate touches the frame.

I had my stock skid plate mounted with 2 1/4" grade 2 bolts per side and never had a problem.

 

[redranger4.0]

Regardless, those bolts are never going to see enough force to shear. 90% of the forces on the skid plate will be pushing it towards the frame, transfering all of that force directly from the skid to the frame, no bolts involved, because the skid plate touches the frame.

I had my stock skid plate mounted with 2 1/4" grade 2 bolts per side and never had a problem.

this is correct i didnt even think about it already touching the frame. i guess my mind was on the bolts since i jsut did that lab no a couple hours before posting originally

 

[IZwack]

woot we should start a thread on undercarriage skid plates.. just ppl posting pics of their designs

 

[Stic-o]

Sorry Matt we didn't mean to hijack your thread and talk about bolt strenghts, but it happens

Anyway good job on the sjid plate, I think I may build something like that

 

[RockRanger]

They are 3/8" grade 5 bolts. I had them so I used them. As Jefe said it sits against the frame the entire length of the frame. Im not to concerned on the strengh. I would like to add another bolt to each side however I would have to weld a tab to it so I could get it to drill into the frame. After seeing the stock skidplate I think cardboard would be an improvement.

 

[BKennedy]

After seeing the stock skidplate I think cardboard would be an improvement.

My skid plate is made from very thin material (1/8") framed with 1" tubing, but with the NP231 T-case, its way up between and nearly at the top of the frame rails.
I think the gas tank skid plate is made from some type of cardboard with a thin piece of sheet metal over it. I need to get under there and bend it back straight so I can get a full tank of gas. I am thinking about welding a thicker piece of sheet metal to the bottom of the stock skid plate, so it doesn't get so bent up.

 

[94 Crawler]

I was wondering how much lift you have in the rear,1/2 ton chevy springs and shackles, any other? How dose this set up flex compared to stock lenth?
My supercab is curently on explorer 4x4 leafs and 5.5" blocks I would love to get rid of the block or at least be able to run the factory 2" one. I was considering this option as I have read that the stock springs flex well. Oh by the way great build, as with quite a few I have read here.

 

[RockRanger]

Between the shackles and the chevy springs I got about 5" of lift. I am also running the stock block as well. The 63" chevies by themselves will match a rancho TTB lift kit perfectly. They flex well but are soft. As soon as you start adding weight to the bed they start to sag fast. An add a leaf would probably help. For the $50 or what ever I paid for them it is well worth it.