Recovery off rear bumper bracket

[StuckInTheMudd]

I need to replace my rear bumper to add recovery points and to add some protection. I currently have the standard tissue paper installed.



I'm thinking about building my own bumper. Will my current brackets be strong enough to perform recovery off?
They look something like this...


Full Size

[Dowe Koos]

For myself, I rather have a 8mm thick plate than these on your photo.

[StuckInTheMudd]

yea i'm kinda doubtful as to their strength. where could I get something better in the Northern Suburbs?

[niclemaitre]

Get 8 or 10mm plate laser cut rather

Untitled.jpg (30.67 KiB) Viewed 3374 times

[StuckInTheMudd]

that's not a bad idea. how much does that cost?

[niclemaitre]

I had something similar made up for my front bumper and both identical brackets came to around R350 total. You can then weld spacers around the recovery hole in the bracket to make it more resistant to being torqued.

Third pic down is the bracket I had made: viewtopic.php?f=41&t=39900&p=472088#p472088" onclick="window.open(this.href);return false;

If you can make the diagram yourself in SketchUp or some kind of CAD it will be cheaper than if you give them the existing bracket and they have to do the drawings themselves.

[StuckInTheMudd]

that looks pretty decent. i'm concerned about matching the existing holes in the chassis to the drawing though. or should I rather drill the holes myself?

[Jurgen10]

For myself, I rather have a 8mm thick plate than these on your photo.

+1 thousand , million, seventy five hundred and two

Please do not use the standard tissue paper bumper fittings , they are almost as thin as the bumper and will fail when you don't want them to.

I used the standard fittings as a template to drill the holes on the 50 x 50 x 5 angle iron I used for brackets when bulding my rear bumper, and I don not intend using the 5mm brackets as recovery points... their job is just to hold the bumper up :)

viewtopic.php?f=41&t=40806&p=480536#p480536" onclick="window.open(this.href);return false;

[StuckInTheMudd]

Who knew that when one buys a 4x4 it becomes a big boy's Mekano set

I intend on using something of substantial girth. Also want to double-up, put a bracket on both sides of each chassis beam.

[niclemaitre]

that looks pretty decent. i'm concerned about matching the existing holes in the chassis to the drawing though. or should I rather drill the holes myself?

Measure carefully with a vernier. They will most likely be some whole number in mm apart. The centers will be the distance between the holes plus one hole diameter apart.

It's more the shape that you should worry about since it is shaped like that to avoid various fittings etc.

[niclemaitre]

SketchUp is damn easy to use if you spend a little time figuring it out. There is a plugin for the free version that exports to .dxf files that the laser cutters use. All the time I've invested in learning how to use it properly has been repaid many times.

[Mud Dog]

Use 8mm plate, minimum. Reinforce the recovery holes - this can be done by welding a short (about 12mm) piece of thick wall pipe into an oversized hole. You should also weld a reinforcing gusset (with appropriate holes) over the rear chassis rail legs - all good and well to beef up the bumper mounting brackets but then the weak point becomes the chassis rails - they're only about 2½mm gauge on those extensions and I've seen those holes tear / elongate first hand. Also use suitably rated bolts.

[StuckInTheMudd]

ah yes. good advice.

perhaps a stupid question, are steel square bars strong enough for recovery purposes?

and would filling it with sand be a good idea? I want to destroy anybody riding into me :)

[Mud Dog]

Don't recover off the bumper itself - use the brackets for that. The 'danger' in beefing up the bumper rails is that there will be little or no 'give' on impact and the damage will transfer into the chassis. It's also unnecessary weight on the rear overhang. Use something like 2mm - 2.5mm gauge but brace the section between the mounting brackets from behind if you're going to tow with it.

[StuckInTheMudd]

Don't recover off the bumper itself - use the brackets for that.

oh right! Is there any need for those rated recovery hooks/points then?

The 'danger' in beefing up the bumper rails is that there will be little or no 'give' on impact and the damage will transfer into the chassis.

You've got a point there. That got me thinking. There are shock absorbers for bumpers. Worthwhile? Or am I getting to complex now?

[ChrisF]

Friend owns a panelbeater workshop.

He has built MANY custom rigs over the years.

Bracket from the chassis rail - THICK steel, attach your recovery points at this point. Firstly it is the strongest point, secondly it is directly in line with the chassis rail, thus no bending and twisting

from there his bumpers are a "measily" 2mm steel. Way thick enough for light bumps, but it is still the soft part that absorbs a mild impact - thus protecting your vehicle !

Remember in a mild to heavy accident something WILL bend. If your bumper is too strong it will be the vehicle doing the bending ....

[Changes]

Just fit a Bundu Gear bumper from Neil at 4x4 Direct and all issues and problems solved.... :-)

[Mud Dog]

oh right! Is there any need for those rated recovery hooks/points then?

Definitely! Every single link / point / component must be rated. Ideally the single weakest point in the set-up should be in the recovery strap itself so that there is no chance of any metal bits being flung about in the event of a failure. The kinetic forces released during a failure can catapult a recovery hook / shackle right through a wind-shield and a seat inside the vehicle - imagine it hitting a bystander or vehicle occupant.

You've got a point there. That got me thinking. There are shock absorbers for bumpers. Worthwhile? Or am I getting to complex now?

Yep, that's going too far - all well and good for the front but not for the rear if you're going to tow and certainly no good if it is placed so as to form part of the recovery components.

[StuckInTheMudd]

Just fit a Bundu Gear bumper from Neil at 4x4 Direct and all issues and problems solved.... :-)

That would certainly be the easiest option, but whole point of this exercise to is not spend 7-10k

Friend owns a panelbeater workshop.

He has built MANY custom rigs over the years.

Bracket from the chassis rail - THICK steel, attach your recovery points at this point. Firstly it is the strongest point, secondly it is directly in line with the chassis rail, thus no bending and twisting

from there his bumpers are a "measily" 2mm steel. Way thick enough for light bumps, but it is still the soft part that absorbs a mild impact - thus protecting your vehicle !

Remember in a mild to heavy accident something WILL bend. If your bumper is too strong it will be the vehicle doing the bending ....

Some more good advice :) should I perhaps use my existing tissue paper then? Just reinforce the mountings and put a square bar inside it...

[ChrisF]

NOPE ! :)

The "bracket" must be the STRONG part - remember this is where your recovery points are.

It is the "face" of the bumper that has to be softer to do the bending, before the vehicle bends ...

[StuckInTheMudd]

NOPE ! :)

The "bracket" must be the STRONG part - remember this is where your recovery points are.

It is the "face" of the bumper that has to be softer to do the bending, before the vehicle bends ...

That's what I meant, perhaps I didn't explain properly.

I meant weld strong brackets onto the chassis (with recovery points), then a square bar onto that and my existing soft bumper over that.

[Dowe Koos]

Rather a thick wall square tube than square bar.

[StuckInTheMudd]

could you send me a photo of what you're referring to please? I'm not familiar with these things. We may even be referring to the same thing.

[Stef]

This is what I did in 2010 for the AAWDC fun day

viewtopic.php?f=35&t=12595&p=227555&hil ... ts#p227555

[Mud Dog]

could you send me a photo of what you're referring to please? I'm not familiar with these things. We may even be referring to the same thing.

Square bar is solid material - square tube is hollow tubing.

[StuckInTheMudd]

could you send me a photo of what you're referring to please? I'm not familiar with these things. We may even be referring to the same thing.

Square bar is solid material - square tube is hollow tubing.

Aaaah. Then I meant square tube.

[ChrisF]

NOPE ! :)

The "bracket" must be the STRONG part - remember this is where your recovery points are.

It is the "face" of the bumper that has to be softer to do the bending, before the vehicle bends ...

That's what I meant, perhaps I didn't explain properly.

I meant weld strong brackets onto the chassis (with recovery points), then a square bar onto that and my existing soft bumper over that.

ooops. my bad.