Offroad Trailblazers and Envoys

Trailblazer Rear Bumper Design/Build

Any special projects involving a decent amount of fab work (bumpers, sliders, roof racks, etc)

by Trail X » Mon Jul 26, 2010 9:03 am

I've been working on a little secret project for a while now. It's still in somewhat of a planning phase, but it's also in the beginning build phase. I was originally going to keep this a secret, but then I thought... what's the fun in that?!

This was the original concept for a rear bumper that I made for Teebes about two years ago.

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After much deliberation and sketching, I decided to make an 8"x4" tube the main structure component instead of building it out of sheet steel. One of my goals was to make the bumper a simple but extremely strong and robust bumper.

The upper 'wings' will fill in the section below the tail lights. The pic below doesn't have them trimmed to the proper length.

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Here's a cell phone pic when I got the first bumper bracket on. 3/8" It's not going anywhere.

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I worked on some FEA stress analysis since I knew that putting an air tank in the rear bumper could be potentially dangerous. Originally I didn't have internal ribbing, but it was added after the first round of FEA to keep the tube from expanding at the center.

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Here we are working on the center tube... Eric, my fabricator and friend, is cutting the hole for the 2" hitch.

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Aligning the center section.

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Center section tacked in place.

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The end caps are very important here, as they will each be holding back thousands of pounds of pressure of compressed air, plus they will be supporting any trailer and winching loads.

Eric did a great job of getting 100% penetration welds all around the end caps. They will easily withstand the stresses being applied.

Below, hitch is sitting beside the bumper, ready to be welded in place.

After we weld in the air tank bungs, we'll do a pressure test to 150 psi. The tank should be good to about 200 psi before yeild, but my operating pressure will only be 100 psi.

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For the swing-out, I have a sketch of what will be done. I also already purchased a heavy duty hinge from EMS off road:

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That's it for now, it will be a few weeks until we can do a test fitment with the bumper wings. Then a few more weeks after that until we can complete the swing-out. I'll keep this updated as I make my slow progress.
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by HARDTRAILZ » Mon Jul 26, 2010 9:11 am

Nice addition for you.
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by bartonmd » Mon Jul 26, 2010 9:12 am

Lookin good!

If there's room, you guys may want to fillet weld the bend reliefs on the frame brackets. Perfect place for a tear to start, as you know.

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by Trail X » Mon Jul 26, 2010 9:16 am

bartonmd wrote:Lookin good!

If there's room, you guys may want to fillet weld the bend reliefs on the frame brackets. Perfect place for a tear to start, as you know.

Mike


Once we weld the wing tubes on, the reliefs will get welded closed. Good eyes.
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by bartonmd » Mon Jul 26, 2010 9:26 am

JamesDowning wrote:
bartonmd wrote:Lookin good!

If there's room, you guys may want to fillet weld the bend reliefs on the frame brackets. Perfect place for a tear to start, as you know.

Mike


Once we weld the wing tubes on, the reliefs will get welded closed. Good eyes.


It's cool... I figured you would, but didn't want it to get forgotten, then me say "yeah, I saw that in the first part of the built, but didn't say anything"

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by Zero » Mon Jul 26, 2010 9:33 am

Damn Barton, your on top of this stuff like a fat kid on a cupcake!!!

And James, great looking bumper! That has to be the first one Ive seen that will also hold air. Good space saving idea.
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by janesy86 » Mon Jul 26, 2010 10:56 am

JD, thats pretty sweet! Can't wait to see some more updates!
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by djthumper » Mon Jul 26, 2010 2:01 pm

That looks pretty sweet. I can't wait to see more as it is completed.
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by Zero » Mon Jul 26, 2010 4:19 pm

A few things I hope make it onto your bumper from the first drawing are...

Side steps
Hole for exhaust
2x Jerry can holder
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by Trail X » Mon Jul 26, 2010 4:28 pm

Haha, I don't think any of those things are going to make it.

Steps are pretty useless there due to the slope of the roof. Provide no benefit over using the tire.

I may put a hole for the exhaust, but the bumper will be mounted so high, I'd have to cut the body to run the exhaust that high.

2 Jerry cans will be too much weight on the far side of the arm. Going with a single instead. My thought behind that is that a single is all that's needed 90% of the time. 5 gallons of gasoline gives you +90 miles on road, or +40 miles off road... plenty for most circumstances. I'll still have the option of mounting some on the roof as needed.

Sorry to disappoint. :raspberry:
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by Philberto » Mon Jul 26, 2010 5:00 pm

Solution for weight issue of 2 cans: dual swingouts. That's my plan anyways.
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by KE7WOX » Mon Jul 26, 2010 5:05 pm

It seems that the pictures have vanished.
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by johnburgelin » Mon Jul 26, 2010 5:19 pm

KE7WOX wrote:It seems that the pictures have vanished.


I see em, and it looks great! Reminds me of how badly I want a welder :(
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by Trail X » Mon Jul 26, 2010 6:05 pm

Philberto wrote:Solution for weight issue of 2 cans: dual swingouts. That's my plan anyways.


I considered that, but it adds cost and makes the rear a little more difficult to access (2 actions vs. 1 simple motion). The main reason was that I think it'd really confine the space when camping. As it is, the plan is to basically build the campsite off the driver's side with the swingout hinge on the pass.side, so it doesn't get in the way. Or, at least that's my thoughts.
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by aaronrules » Mon Jul 26, 2010 7:02 pm

Can I call dibs on your spare tire carrier you have now? Seriously!? When you get this done, I will totally take it off your hands! Let me know how much!
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by glfredrick » Mon Jul 26, 2010 7:45 pm

Nice work. Even better design work! Some high-zoot software. I have Bend-Tech Pro, which works great for cages and tube work.

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One caveat, it is possible to build too heavy. All that weight has to be carried around and boosted up on every sort of surface imaginable.

I've actually built a number of box tube bumpers for various projects. In many cases, I hollow out the back for a considerable weight reduction. In your case, the air tank negates that, but you can make the end caps lighter.

Here's one I built for the rear of my 'Sploder. The bumper had to ride in that spot due to the frame rails, so I made the tubing to compensate and add interest and light-weight sliders to protect the rear windows (which I lost on more than one occaision before the bumper).

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by Trail X » Mon Jul 26, 2010 8:05 pm

Hey Guy! Very cool bumper. I appreciate the input too. I actually have been considering getting rid of the back panel of the wings. My hesitation comes from it just becoming a place for mud to gunk up since it's right behind the wheels. Plus, the pass. wing will be supporting the hinge... so I'm not sure if I want to open it up too much.

My fabricator has bendtech - I use the software at work to do the analysis and design.

Aaron, the old tire carrier may already be spoken for. We'll see how it pans out. If it does go on the market, I think I'd like to get $200 for it. They go for $350 new.
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by aaronrules » Mon Jul 26, 2010 8:12 pm

JamesDowning wrote:Hey Guy! Very cool bumper. I appreciate the input too. I actually have been considering getting rid of the back panel of the wings. My hesitation comes from it just becoming a place for mud to gunk up since it's right behind the wheels. Plus, the pass. wing will be supporting the hinge... so I'm not sure if I want to open it up too much.

My fabricator has bendtech - I use the software at work to do the analysis and design.

Aaron, the old tire carrier may already be spoken for. We'll see how it pans out. If it does go on the market, I think I'd like to get $200 for it. They go for $350 new.


You tell me when and where to send the money, and I will literally send the second you tell me man! If it's not already spoken for...since your TB is everything I wish mine can be...what better way than to get THE original JAMES DOWNING tire carrier! :drool3:
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by tbangert » Mon Jul 26, 2010 8:35 pm

I am really liking the idea of an air tank incorporated in the bumper. I've been trying to figure out a location for an air tank, so I may have to ponder this idea.
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by Zero » Tue Jul 27, 2010 10:32 am

Just wondering if having an airtank in the bumper would cause a vehicle to fail a safety check?????????

Also, what would happen if you got rear ended with the tank filled to 100 - 150psi? Would the air just hiss out slowly? Would it cause an explosive effect sending metal or other material towards the person driving behind you?
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