Strengthening a bumper?

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Jabba
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Strengthening a bumper?

Postby Jabba » Tue Sep 21, 2010 1:27 pm

Following my attempts to turn the front bumper on my 90 into a wraparound style, I'm looking at ways to make it a bit tougher.

I can't afford to replace it with a nice HD bumper, but I do have a scaff tube lying around that I was thinking of inserting into the full width of the std bumper and welding in place on the ground that this might make it harder to bend.

Any thoughts, comments etc???

Cheers, Dave

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davew
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Postby davew » Tue Sep 21, 2010 1:45 pm

The main downside with strengthening a bumper is that, if you do bend it, it takes a lot more to straighten it again !

I'm not sure how practical putting a tube behind it would be, assuming you run it full width. The chassis outriggers are very close to the front of the bumper IIRC and there are also some strengthening plates on most of the "standard" bumpers I've seen. You could cut the tube around the chassis but then that would leave the tube at it's weakest at the exact point you need the strength !

If you can get it into place, you need to be VERY careful when welding scaffolding tube. You need to remove all traces of galvanising from it before welding. I might have a suitable piece of blue band kicking around (a bit like scaffolding tube but without the galvanising and stronger). At best, welding galvanised metal without breathing apparatus will give you severe headaches and may effect your vision... it goes down hill from there !

For the work it would take fitting a bit of pipe behind the bumper it'd probably be quicker and easier to make your own bumper from scratch out of some box section. A length of 75mm x 50mm x 3mm box section won't cost a great deal, taper the ends, add some 3mm plate for the mounts and you're done.

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Jabba
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Postby Jabba » Tue Sep 21, 2010 1:55 pm

Thanks Dave.

I was thinking of opening up one of the ends and inserting the tube inside the box of the std bumper rather than trying to fit it behind. That way it would be a single run of tube.

Making my own was something I hadn't considered but sounds like it might not be too bad. Do you know where I can get the steel in the Harrogate area? I think I've seen a steel merchant in Knaresborough near KBR car repairs.

Cheers, Dave

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Postby davew » Tue Sep 21, 2010 4:20 pm

Tomrods is the easiest, down on Manse lane. You'll probably end up having to buy a 6 or 7 metre length though. They will normally cut it up into more manageable lengths with a gas axe for free if you ask them - makes it a lot easier to go and collect it yourself. 50x75 is an ideal size for rock sliders too so you'll easily get enough for a bumper and a couple of rock sliders out of a length.

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Jabba
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Postby Jabba » Tue Sep 21, 2010 7:07 pm

Looking at the std bumper, it's 100mm high x 75mm deep x 3mm thick. If its going to be stronger than std, would it need to be thicker steel? Or would doubling it up to get the right height also make it strong enough?

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Zedman
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I would forget Tomrods

Postby Zedman » Tue Sep 21, 2010 7:55 pm

I would forget Tomrods, they are a steel stock hodler and as such supply steel in bulk, generaly they dont want to know for small lengths, cheap if u want lots but for small fabrication not realy practical.

I would recomend the place in Starbeck, Marlin metal craft. When I needed some shackles they cut me 12 lengths of bar exactly to size and charged me £6.00 cash, ohh and they did it while I waited )

They specialise in small 1 off fabrications, take some good sketches with exact dimensions on all the parts for the assembly and I'm fairly confident they can cut and weld exactly what u need.

Let me know if they dont and I will see what I can do myself )
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davew
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Postby davew » Tue Sep 21, 2010 9:11 pm

Jabba wrote:Looking at the std bumper, it's 100mm high x 75mm deep x 3mm thick. If its going to be stronger than std, would it need to be thicker steel? Or would doubling it up to get the right height also make it strong enough?


A full box section will be a lot stronger than the standard C section bumper. If the original is 100mm high then maybe use 100mm x 50mm box section instead ? If you want to try some for size up against your motor I have some here, I think I have some 100x50 and 75x50 in the garage.

I was thinking of something like this...

Image

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Zedman
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I agree with dave

Postby Zedman » Tue Sep 21, 2010 9:37 pm

I agree with Dave, forget the C section go for the box easier to weld (does not distort as much and thicker walls) and cheap a chips (cheaper if dave has some spare) and far stronger.

Oh and I do like the look of those recovery points much easier to make and will offer more flexibility on the pull angle, ie less strain.
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If its not rattling its more than likely fallen off !

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Jabba
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Postby Jabba » Wed Sep 22, 2010 6:51 am

I think Nick Adams has something like this on his 90 (Devon 4x4 do one) and I was going to model anything I make on that. If Marlin can supply and bend the bar for the recovery points then that would be good.

Thanks guys for all the input.

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Jabba
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Postby Jabba » Wed Sep 22, 2010 8:30 am

Dave: any chance I could pop round and have a look at that box section? When would be OK?

Cheers, Dave

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davew
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Postby davew » Wed Sep 22, 2010 10:37 am

Sure, just give me a bell beforehand, I'm in most days.

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tecnick
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Postby tecnick » Wed Sep 22, 2010 8:20 pm

yes I have got one and so far its been great. D44 also do one that sit above the chassis but loads more money, I guess that would mean more fab. If you want to have a looksee I should be at the next club meet.
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