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The dumbest of irons!


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My dumbirons need attention,  but I know at some point I will need a new chassis, so don't want to go to the length of replacing them. Some of this is down to cost (I will put the dish in my new chassis fund) but also having to strip the rad out and it's not long had new coolant. 

So I decided to do a patch up job but wanted it to last for a while, and it needs some attention! I had a look at the various bits of steel I had lying around and found a piece of 3" square box section.  This is the same width as the chassis and I could use this to rebuild the rusted section. 

I measured the chassis and marked it so that the box section would give the correct depth when I include the top section.  I cut along the weld on the lower section of the dumb iron then chiselled the old section out. I notched the box section to suit what I had removed from the chassis rail. I drilled the box to mimic the original bumper fixing holes, then butchered some 30x30 box gor strengthening. 

It's not a perfect solution by any means, but it has put strenght back. I am considering if I rebuild the lower sections or just remove thefront part- I will decide tomorrow!

The weld isn't the prettiest,  but it's strong enough for this patch-up.

 

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10 minutes ago, Maverik said:

It's evolved it's own crumple zones to keep up with latest legislation...

Not an easy place to repair, lots of additional structure in those areas. Good effort.

Ha ha, it certainly was lacking its original strength.  Just patching the rot wouldn't have put the strength back in the lower section of the chassis rail. Using box section has put some of this strength back but obviously it is not welded internally, so that will be the weak spot here. 

It is a difficult place to repair and I have managed to do this whilst only removing the bumper, grill and panel. I used the grinder on the horizontal cuts but had to use the plasma on the vertical cuts etc. 

The lower part of the chassis rail is the hardest part to get out. It is welded to the dumb iron lower section so it's important to cut the weld off as much as possible.  You then have to chisel the lower section out (hence cutting all the weld off!) and I managed to then batter the lower section out due to the amount of corrosion. I  cut the lower section of the box section insert to suit what I managed to remove. You don't have to remove the top part of the box section as this sits about 10mm lower than the upper section of the chassis. This adds extra strength to the upper section too - and the box section has a 3mm wall so a good base to weld to.

It's not perfect but far stronger than just welding plates in, and also should be good enough to last until I decide to change the chassis. Also, all the repairs I have seen to dumb irons seem to have the rad and wings off - which I didn't want to do!

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Well I managed to get the other dumb iron done today, including the lower section.  It's fabed up from 80x40x3mm hollow section and a piece of tube to stiffen the jacking point. This is sandwiched between the sides of the original section and welded in. Unfortunately rain stopped play so I still have the lower section to do on the other side.

I managed to keep the chassis number which I was keen not to lose. 

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