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Help w/ bumper design

Discussion in 'The Garage' started by greatwhitenorth, May 23, 2002.

  1. greatwhitenorth

    greatwhitenorth 1/2 ton status

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    Well, I got access to the shop at work now so I figured I'd have a little fun and build my self a new rear bumper..

    http://tellico.off-road.com/wwwthreads_uploads/782643-BEATER%20BUMPER.jpg

    ****Note: Dimensions are to be confirmed*******

    The plan would be trim the rear fenders horizontally to clear the wrap-around C-channel, and mitre the ends of the C-channel to follow the curve of the wheel well down (will also trim back fenders in the process).

    Then bolt the C4x5.4 channel to the existing bumper mounting holes and drill 4 holes thru the frame and the plates to mount the transverse braces to the frame...

    I will be making a jig to represent the frame while welding this to keep it from bending and distorting...

    Any suggestions??? Should I make it almost flush with the tailgate, or extended out with a piece of plate on top like a normal bumper????

    Should I extend the C4x5.4 channel out so I can bolt the transverse braces thru that too????

    Is 138lbs too much?? Any idea how much a stock bumper weighs? 60lbs??

    Sorry for all the questions, any constructive criticism will be much appreciated
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Stock bumper is only about 30 lbs or so. I'd extend the 4" Channel a little farther in and tie in the side braces.

    Channel is probably my least favorite material though. I'd use HSS instead, but that's just me. Some 3x6 in .125" wall or heavier would be good.

    My two cents...

    Rene
     
  3. greatwhitenorth

    greatwhitenorth 1/2 ton status

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    Rene, I have considered using HSS instead of the C-channel, but decided against it for weight reasons... The springs I had made are pretty soft, and don't offer that much lift so I'm trying to keep the bumper as light as possible....

    I think the gusseting will make up for some of the downfalls of the c-channel (less bending resistance/moment of inertia/blah blah blah)...

    I'm think I'm gonna build it like this for now and see how it works, if it gets tweaked than I'll build a new one or box the channel in..

    Thanks for the input, us canucks gotta stick together... maybe see you on the trails in the lower mainland when I return in september..
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    C-channel is heavy in comparison to HSS, plus it isn't as strong. It's quite suceptible to torsional weakness, which is why you always see factory step bumpers all twisted. With HSS you could use a thinner wall and still have a stronger bumper. I used .125" wall 2x8.5 (oddball custom size I got for cheap) for my front and rear. They weigh about half what your planning on building.

    Last Easter I got rear-ended by a 77 F-100 longbox pick-up that hit me at 55 mph. I was stopped at a red light...My rear bumper has a slight bend on one side, but never hit the body. The tailgate did get wiped out though when the spare tire was pushed almost all the way through it.

    Drop me a line when you come back to the coast!

    rene
     
  5. 85m1009

    85m1009 1/2 ton status

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    Very similar to the new bumper on my K5. I used 3 x 6 .25 wall across the back but sliced and tapered it to 2 inches tall at the ends, from the frame out. I used 2 x 2 .25 wall forward and back to the frame under the quarters. I also built a 2 x 2 crossmember to connect the front pieces. The end result is no bumper flex even with the entire weight of the truck on them. I also ran my exhaust out through 4 inch sleeves in the center of the bumper. <a target="_blank" href=http://www.mo-offroad.com/Halfdoors2.jpg>www.mo-offroad.com/Halfdoors2.jpg</a>
     
  6. greatwhitenorth

    greatwhitenorth 1/2 ton status

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    Point taken Rene, I'm gonna move my gussets up onto the flanges of the c-channel, so I think that'll will help a bit...

    I'll make a new drawing when I get some firm dimensions..
     
  7. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    One thing I will warn you about wrapping that under the fenders is that there is a LOT of frame movement. If you come down on the end it will hit the body. Heck you don'e even need to come down on iut just get it flexed up real good and it's going to hit. You might concider put some sort of brace off the floor with a bushing to the bumper to keep the bumper from really slamming into the body.
    While my bumper doesn't wrap around it's a tight fit to the body. I bottomed it out on the corner real hard and the bumper hit the body so hard that it caused the bed section to twist and I cracked the hard top. Under stand my bumper did not bend. The frame twisted (normal for these trucks since the frame is so narrow as compaired to the width of the body). It's made out of 4x4 3/16 wall box with 3/4 inch thick uprights bolted to the frame. /forums/images/icons/smile.gif
    Pictures of my truck in the links in my sig.
     
  8. 85m1009

    85m1009 1/2 ton status

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    The crossmember across the front section eliminates any body contact on my application. I only have about 1/2" between the body and the bumper.
     
  9. Twiz

    Twiz 1/2 ton status

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    What is HSS? High Strength Steel?


    I've seen tRusty's bumpers, and they are well-built, to-say-the least. I bet a guy could push a tank with it.

    How much do they weigh, Rene?
     
  10. Twiz

    Twiz 1/2 ton status

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    The frames twist like mad on our rides, keep that in-mind.

    I'm in the same-boat here too, I've been building bumpers for my Jimmy. I'am going for the wrap-around tube type, and will just keep trimming sheet metal 'till it clears (when flaxed).
     
  11. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    HSS stands for Hollow Structural Steel...mostly in reference to box tubing. HSS is much quicker to type though/forums/images/icons/wink.gif

    My front bumper weighs just under 60 lbs. The rear wieghs probably about 80 lbs without the spare tire on it...
    <blockquote><font class="small">In reply to:</font><hr>

    I bet a guy could push a tank with it.

    <hr></blockquote>
    They are as strong as I need them to be. They are stronger than the frame at any rate...

    Rene
     
  12. chris672

    chris672 1/2 ton status

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    are you going to be selling rear bumpers like the one in the pic?
     
  13. 85m1009

    85m1009 1/2 ton status

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    I can build them but in order to do the wrap around to the frame you would have to weld the pieces that return to the frame once you got them.
     
  14. greatwhitenorth

    greatwhitenorth 1/2 ton status

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    Well here's the updated drawing.. still not final but getting there.

    http://tellico.off-road.com/wwwthreads_uploads/785657-beater%20bumper%20rev2.jpg

    I think the gussets on the inside of the frame mounts might be overkill, but it should be strong enough to withstand the bashing thru tight trails the old beater does..

    Oh yeah, the main part is now 5x2x3/16", frame mounts are 4x2x3/16", cross mounts are 2x2x1/4", all gussets and pads are 1/4" plate except for the frame side re-pads which are 1/2" plate..

    Looks like the steel will cost me about 115 bucks, and it should weigh about 130lbs.

    Gonna have to notch a piece of the pickup box to let the 4x2 enter the frame rails, and remove the rear-most bed bolts to get everything in. Gonna be lots of work with a sawzall and drill to get this thing in but it will be fun...

    Thanks for the help guys.
     

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