Fitting new rear quarter chassis - advice

[MisterC]

OK, I've cut the old rear quarter off of my SWB S3.  Got the new replacement and was thinking/hoping that the ends of the new one would be stepped and slide into the old chassis rails.  However, the extended 'tongues' appear to be the same width /depth as the rest of the chassis rails.  This isn't helped by the gezillion previous patches on the offside chassis rail, making it even narrower internally and wider externally.  So, do you bend the tongues out and slide over the outside of the chassis or (preferably, as it will be less welding), grind the tongues a bit, bend a step into them and slide them into the old chassis rails?  Thanks in advance.  Paul

[S188]

Last weekend at eastnoor I was looking at an 80" chassis that had had new dumb irons welded to it prior to galvanising, the finish was perfect, almost invisible smooth welds (not hiden by galv).  I asked the guy about it and he said that was the finished weld with no post preping (grinding).  What he had done was tacked a plate inside the join conecting and locating the dumbiron the the mainrail with a 3mm gap between the two.  The gap was then welded properly filling it flush giving a strong unobveous butt weld - I was very impressed.  He was a profesional granted, but it was a very tidy method.  Couple of layers of paint and you wouldn't be able to tell I'm sure.  
Once complete the plate on the back adds some strength to the weld but the main strength is between the old and new parts and is better than an external blob joining 2 plates touching end on.  I'm going to try this myself one day!

[craftycarper]

i would have to agree with that. If the new section does not fit over the old section then you may have to work the ends of the new x member. This can be done by welding new plating extensions around the outside/inside of the new section ends which will then give it the clearance to enable it to slide over or into the existing chassis section, just means that more welding is needed which you probably didn't want to do...good luck

[Bob Ajob]

Tongues inwards as you suggest, someone did ours on the outside, and didn't weld the seams, which of course failed the MOT (the lack of welding, not the fact they were on the outside).

You can also drill holes through the old chassis (but not through the tongues on the inside), so that you can put some additional welds on to the tongues filling the holes, this will give additional strength in holding the bits together.

[MisterC]

Thanks for the replies.  After measuring the new rear quarter and the chassis rails, and then measuring again, and one more time for luck.  It's evident that the new rear quarter I have is designed to 'slip' over the ends of the existing chassis rails.  It's slightly (a lot) complicated on the offiside as this has two previous repairs on top of the original making it too wide to accept the new rear quarter.  Having postulated about it for hours, I eventually removed the outer layers of repair back far enough to allow the new one to slip on.  Thankfully, the chassis is intact underneath at this point.  It's now fixed on with the tub to rear crossmember bolts to hold it in line and I will be starting welding (for the first time) within the next couple of days.  I will weld up the seams as well of course.