Here is a description of how I replaced the nearside sills on Spooky
We knew we were going to need to replace the whole lot on the nearside after doing the offside, especially as when the sliding door was rolled fully back on the track the bottom roller 'dropped' through a hole in the track.
First I removed the sliding door, this had already been fully rebuilt by me and was in superb condition!!!
The basic idea for me was to replace the following:
Ok, the outer sill is nothing more than a piece of trim really and as far as I know has no structural part to play so this was carefully cut off to expose the very rotten middle and inner sills.
As the B and C pillars were also virtually non-existent I cut these back to give me some room.
Now, the most difficult and most important bit. The new middle sill does NOT come with the upper track, so you have to cut off the original one, weld it to the new middle sill prior to fitting it back on the bus.
It is therefore most important that the upper track goes back in exactly the same place as it came off so when you are in a position to start to remove the middle sill the first thing to do is locate the upper track. What I did was to drill about six small holes through the cabin floor and through the upper track and put some 4mm bolts through. This then ensures that whatever you do the track must go back in the same place as long as the bolts are fitted.
Now I know where the upper track is I can start to cut away the remains of the sill. I cut horizontally at the same level or lower than the outer lip of the upper track.
What you should now have is the upper track still fixed to the floor of the bus and the remains of the inner sill still attached.
You should now see where the inner sill is spot welded to the ends of the jacking points and floor top-hat sections, grind through the inner sill so that it comes away from these end flanges without damaging them. See below.
In order to give me the maximum access to the middle sill I drilled out the spot welds for the inner sill from above, this is a bit fiddly as the welds are not obvious. I used a small pilot drill to indicate the centre of the spot welds and then went through with a big drill (about 8mm). Hopefully the inner sill will now fall off....
Now comes the removal of the upper track that is still firmly attached to the floor.
You will see that this is not fixed at either end and once the spot welds are drilled through this should come off. It is well worth taking some time over this part of the process as this track MUST go back on afterwards.
Again I used a small pilot drill to locate the centre of the spot welds then used the big drill to PARTIALLY drill through the floor. You must NOT drill right through the upper track as you are going to need to plug weld it back on through the holes drilled in the floor. What I did was to drill through so far and then wack the upper track through the hole with a punch to break the remaining weld.
Once the upper track is off you can clean up the whole area. I repaired the front and rear jacking point top-hat sections as the outer ends of them were rusted away. I was also going to replace the jacking points and outriggers so that I had a clear area to start fitting the new sills.
Here you can see the amount of metal that was removed prior to starting the welding process. You can also see a couple of chassis leg repairs that were carried out.
Fitting the new sills
The first thing to be done is to weld the inner sill to the ends of the top-hat sections.
Here you can see the new jacking point, outrigger and top-hat section with the inner sill welded to it. It is relatively easy to get the sill lined up fore and aft by lining it up with the front jacking point and at the rear you will see that it lines up nicely with the profile of the rear wheel arch inner skin.
Obviously you cannot fit the sill after fitting the jacking point so to line everything up whilst welding the inner sill in place I clamped all the components of the jacking point in place so that everything lined up nicely.
It is at this point that the inner sill can be welded into place. I plug welded along the floor making sure that the sill was nice and tight against it and also plug welded the sill to the flanges on the ends of all the top-hat sections and floor beams.
You can see from the picture above that it was taken after I had welded the jacking points in place
Here you can see the belly pan fitted aswell, I have welded nutplates all around the belly pan landing so that they can be removed in the future. They effectively become a removeable panel and I used a fitting technique commonly used in aircraft manufacture (hence the gripper pins). If you have no wish for these to be removable in the future they can be fitted very last.
Also in this picture you can see the holes in the floor that were drilled to remove the middle sill.
You can see now from the above picture that I have painted the outer face of the inner sill, this is because it is inaccessible after the middle sill is welded on so two coats of rust preventative undercoat and two coats of Re-Paint will look after that. Remember also that the inner face of the middle sill will also need painting as it too is inaccessible. One thing I did do was to drill some strategically placed holes so that a WaxOyl tube could be fed in and a severe dose of the waxy stuff pumped in there when it is all finished.
Ok, it's time to prep the middle sill. Again it is worth taking your time as if you get it wrong either the sliding door won't open or it will fall off!! and we don't want that do we??
Basically, the technique I used was the following:
Repeat the above process until you are absolutely sure you understand how it all fits, this may mean trimming bits off the new sill and trimming up the track. Now, one thing you will obviously notice is that the new sill is a different shape to the original in that it is not curved but bent in two places, this means that the upper track will not fit exactly along it length, never mind, as long as the track is welded back to the floor in it's original place then no problem.
Once you are absolutely sure you are happy that all parts are correct, it's time for a test. Now this is time consuming, a pain in the proverbial but I think, vital. What I did was to fit the upper track with it's locating bolts and clamp the middle sill in position and then do a couple of strategic tack welds so that the track was tacked to the floor, the track was tacked to the middle sill, the middle sill was tacked to the inner sill. Once I was happy that this was done, I removed the locating bolts and fitted the sliding door. From this I could tell whether all was in the right place or not. I slid the door shut, open, shut, open, shut.....until I was absolutely happy that all was in the right place.
I then made some larger tack welds between the track and the middle sill so that I could remove it for finishing. I also drilled through the lower flange so that the inner and middle sills could be bolted together with a couple of locating bolts, this made sure that when I was finally ready to weld the middle sill in it would be loated laterally through the floor and vertically through the lower flange.
Ok, so the door opens and shuts perfectly, I removed the door (boy is that thing heavy!!) and then drilled or ground off the tack welds so that the middle sill/track assembly could be removed to the bench. Incidentally I went through this process three times before I was happy that it was in the right place.
The picture below shows how the two parts differ and where I welded the two together.
And here it is in real life.
You can see here the track welded to the middle sill, I did weld a couple of stiffening pieces in the area where the two profiles differ to prevent the sill flexing. I also put some extra welds along the lower track as I wasn't too confident with the few spot welds that were there.
Another view of the sill assembly
Ok, all happy, right lets get that sucker welded on. Once the middle sill assy was painted and ready to fit I went through another checking process. I fitted the assembly to the bus with the locating bolts and put a few tack welds into place. I then removed the locating bolts, this means that the sill assy should be in it's final position, to check I fitted the door and ran it back and forth to make sure all was ok.
Here you can see the sill assy tack welded into place, the door fitted and a couple of clamps to make sure it's all stable.
Point of no return....I started welding
Here you can see the (large) plug welds through the floor into the top of the upper track.
Finally here's a view of the finished track with it's first coat of rust preventative paint and seam sealer on all joins. You can also see the new C pillar I have made up to finish off, this has some very large reinforcing plates inside so that the jacking point is connected to the rear frame. This will also be repeated with the front jacking point and can be seen in the O/S sill replacement pictures and the wheelarch replacement pictures.
The outer sill has just been tacked on. This is not a structural part of the bus and so only needs to be tacked in place.
Here you can see the finished rear wheel arch as well.
Here is a shot of the sliding door seal slot where the vertical slot meets the outer sill slot.
I have just put the first bit of filler over the plug welds along the bottom flange and painted and seam sealed the join between the middle sill and the outer sill.