DIY Bumper HELP

[Sledder10]

Nearly finished making a steel high-clearance front bumper, but second-guessing my mounting setup. The 4 mounting plates are 1/4” steel and they sandwich my frame rails as u can see below. I’m wondering if maybe this design limits the amount of friction I can actually clamp onto the frame rails with.
so I’m Thinking maybe I just cut off the inner mounting plates and run the bolts from the outer mounting plates and thru the frame rails and use some big washers under the nuts. That way all the force from torquing those 5/8” bolts will be directly applied onto the frame rails proving maximum friction. But then I only have one 1/4” plate mounting on each side of the bumper, instead of 2. The bumper will have a 12k winch on it, so strength is important. In this option I’d reinforce the outer mounting plates as much as I can, but I just worry about the maximum single-shear stress on those bolts. They’re grade 8, 5/8” diameter.

any experts have some advice/recommendations?

thanks in advance

 

[grizzlypath]

Could you sleeve the bolts inside the box-frame? That would help strengthen the frame and allow you to get good compressive force going there. Alternatively, or in conjunction, capping the ends of your box-frame would probably strengthen it up too.

 

[ExpoMike]

Agree, sleeving the bolts will help prevent crushing of the frame when you tighten everything. I only wish there was a cross member you could also tie into on a horizontal plane. Straight pulls will be fine but if having to pull from an angle, I could see the potential of pulling the frame sideways. Capping the ends of the frame would help keep the frame rails from twisting some.

 

[Sledder10]

Yeah I forgot to mention I plan on capping off the front of the frame. Just waiting to see exactly where my skid plate will be located in case I have to trim it back more. But yes adding sleeves is a great idea! I suppose I could find some 5/8” ID sleeves, and bore out the holes in the frame to whatever the OD of the sleeves are. Then hold the sleeve in place and weld the faces of the sleeves to the frame holes. And adding a strengthening cross member between the frame rails is another excellent idea. I could even just make it bolt in with the bumper mount bolts. Or if I straight-up weld it into the frame rails I could make the bumper bolt into that as well. Some decently-sized angle-iron would be perfect for this, yeah?
But the question remains, do I cut off the 2 inner mounting plates and just do the outside ones and reinforce them more?
Thanks again yall

 

[ExpoMike]

If you sleeve it, you can keep the inner 2 plates, just torque them good. If it's a snug fit, it will camp down tight since the frame will not flex in with the sleeves. The extra support of the two plates is better than not having them. If the frame was a C channel, then likely a single plate would be find but would be thicker material.

 

[ExpoMike]

Oh and I would likely add gussets to the inner and out plates, tied into your bumper. This would help the side to side flex. Actually if I was making this, I would have used rectangle tubing, cutting a diagonal off the wide side but leaving it fully boxed where it welds to the bumper. This way you would have a single wall area where the bolt came through, have top and bottom gussets and have a full rectangle welding surface at the bumper.

 

[Sledder10]

Just picked up some pipe that perfectly sleeves the 5/8” bolts, so I will be using that to sleeve all the bolt holes. I’m also gonna try and figure out how to add a third mounting hole to each frame rail that will eliminate the bumpers last degree of freedom that it could move (slightly) in due to the bolt holes and sleeves being bigger than the bolts. Also got some 1 1/2” angle iron to make brace/crossmember to connect the frame rails up by the bumper to keep them straight and rigid under the heavy loads of winching and recovering.
also I’m 99% certain I’m gonna chop off the inside mounting plates and just significantly reinforce the outside ones. I Will keep this thread updated as I go. Any and all recommendations or points of advice are welcome! ?

 

[NatersXJ6]

Have you ever seen a rear JK bumper? The bumper goes down the outer side of the boxed frame and inside the frame are inserts that have captured nuts welded in. The bumper essentially clamps itself to the frame. It feels to me like you are over-thinking this and creating mental stress for yourself. Making that insert and including outside and bottom plate with bolts close to the winch mount points will be strong enough that you smoke or stall the winch long before bending or destroying the steel IMHO.

 

[Simons]

The four bolts included from your winch manufacturer that mount the winch to the plate are what? 3/8” maybe 7/16” grade five?


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[Sledder10]

here's the latest update. I've been working on it here and there after class and work, so its been a long time coming. but its finally nearly done.
I kept the frame mounts and they seem to sandwich the frame rails super nicely and when I remove the bolts it still pops off without a problem. I painted it with 2 cans of black steel-it, and I've got another 2 cans to cover another coat or two. Still got to cut out a rectangle in each wing and weld in some tabs to mount my 6" led spot bars. I've got a second pair of identical 6" spot bars I'm still debating on where to mount. Maybe on the underside or topside of the main grill guard tube? on top of the bumper, just inside of the main tube? open to all ideas. Then I gotta cut the bottom of my grill/front clip out, install the winch, and wire it up. The last step will be taking my sheet of 3/16" aluminum to make a skid plate that runs from the bottom of the current aluminum plate on the bottom of the bumper to the front cross-member. might be tricky without the ability to weld aluminum, but I'm hoping some smart bending will avoid the need to fuse any material. I'm extremely happy with how its turning out. Approach angle is fantastic.