Finally all the stars have aligned and I can get the rest of this build up...
Removing stock tank mounts by drilling out the spot welds. Can be tricky because one or two may not show up until you try to lever the mount off. Stepped drill works quite well, but don't run it too fast...
Terry is retaining the suspension, but konging the seat rails (red arrow) It is usually beneficial to lengthen the swing arm as well to allow enough seat space. This bike being a TX has a slightly longer swing arm and Terry wanted to keep it at that...
Seat rails cut with angle grinder and cuts finished with this 'ol skool tool. It's called a hacksaw you young fellas and was all we had back in the day...
Seat rails removed and a couple of blocks of wood used to simulate new seat height...
Yep! Sweet!
Cleaning up the backbone with grinding disc and then flap disc. Rear wheel is held up by a strut on the other side of the chopper that is drilled to imitate where the wheel will be on full compression. This will allow us to set the guard up so it has 1/2" clearance when Terry hits that massive pothol the the local councils so skillfully put in our riding pathway...
Seat rails are bent a little extra and the ends shaped to fit the new angles. The are tack welded at top front and then straightened using a pipe wrench... only lightly tacked so wrench will not mark the tube...
A flat plate is laid on the rails to allow us to get them sitting evenly and nice and flat...
Rear of rails are set out to line up with the lower part of the rear frame tubes before it swings in. The left side has a noticable kink whereas the right side is simply sloped. On the left side an extra piece of shaped tube will fill the gap and act as a bit more reinforcing at the same time. Seat rail on this side will also need extending...
Next job on the seat rails is a forward gusset. The front of the seat will also be retained here with a tab that slides under the gusset. A piece of heavy walled square tube provides the retainer for the seat tab. It is welded to the underside of the gusset and will prevent the seat front sliding side to side...
To keep things tidy the gusset is cut to sit level with the top of the seat rails. Here a ruler is used to keep it flush as we tack weld
We are going to make rear frame rails that follow the curve of the guard, so we need to set up the rear guard. Terry has chosen a current after market flat guard. However their radius is too wide, so a wedging job is in order. Step one is to mark guard at 75mm intervals...
Then square them up with this handy little tool...
Mark on a piece of paper. Note the mark at the end of the guard so we can line the cuts up on the other side...
Transfering the marks...
Cut with a 1mm blade...
Pulled together and works out just right. You need to check each side has the same curve and the guard does not end up twisted. Then weld, making sure the weld penetrates through to the inside of the guard...
Now that we have the guard correctly curved we can roll the tubing. I use heavier wall tube than the stock bike used as these two curved pieces will support passenger and luggage as well as the guard and taillight assembly. You can do this with heat, but it is time consuming...
We need to mount the guard. At this point we fabricate the front lower guard mount and mark and drill the guard to match (Remember wheel is already set up to full compression with a couple of small 12mm timber spacers to allow some clearance). I forgot to take a pic, but you can see the finished job a couple of photos down.
With the guard mounted at the bottom we'll add in a gusset to contain the upward forces created by the suspension working up against the shocker mount. An engineering principle is that no gusset is required if the force (shocker mount) is within 1.5 diameters of the tube. In this case the tubing is 30mm OD so no gusset would be required if the centre of the shocker was within 45mm of the top of the seat rail. Our gusset will be curved to match the top of the guard to provide support for the seat...
Here Terry has rolled the rear frame tube to the same curve as the top of the guard...
Blue arrow shows initial bottom mount (25x12 tube), red arrow is the second mount (25x6 bar) we can now fabricate and weld into place
To make attaching the guard convenient we make up a set of threaded plates out of 25mm x 8mm flat bar. There is nothing worse than having to pull out your wheel to tighten a loose nut especially if you are out on the road, so I do all possible fastenings with captive female or male threads. I learnt a long time ago to also keep bolts accessible for that dark night when something decides to come loose. Using captive threads though longer to fabricate, actually do save time just in the construction and painting process... a double benefit...
Terry sets up guard and a sissy bar he plans to use. Stepping back to get a pic I note the nice lineup of classic choppers in various stages of development; KZ1100, CB750, KZ750 twin, XS650 and S&S Pan... nice way to make a living playing with all these choppers...
The guard has now been secured by the cross bar opposite the shocker mounts. Long bar and heat are now used to get the final alignment of the rear frame rails...
Parallel rulers come in handy to keep things square. You can just see the second cross piece with centre lines of guard and cross piece visible...
For most of the work I do chopper is set up on level and a spirit level (and plumbobs) get used constantly to keep everything hunkydory. Here being used to ensure the final guard bracket is level..
Tape was used to get the final guard bracket square and is again used from centre point to mark ends of seat rails so they can be cut evenly...
Shocker mount and original frame tube on each side are trimmed ready to be capped. A piece of tube is cut in a rather fantastic shape to extend the wider section of the left frame rail to match the seat rail. A variety of hammers are used to get final matching shapes so the whole area is a smooth transition for each tube and the shocker plate. Open end of shocker mount and original rear frame tube is ready to be welded over with a piece of 3mm flat bar...
Red arrows show welded in tube. Blue arrow shows final weld yet to be done. White arrow shows outer seat rail gusset and purple arrow shows the top piece of 3mm flat bar welded in to close off the two side pieces of the gusset. You can also see that the open end of the shocker mount has also been welded. Once everything is fabricated the parts will be removed so we can finish welding the frame etc.
Chopit'nrideit... Prof
