04. Build #1... Rear end... Building the sissy bar...

Don't ever say you can't afford to build a chopper!!! This thread will prove you wrong
Post Reply
Prof
Founder, Choppers Australia
Posts: 5610
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
Contact:

04. Build #1... Rear end... Building the sissy bar...

Post by Prof » Sun Jun 15, 2008 11:22 pm

Building this sissy bar and attaching a tail light to it is a full day's work so our chopper jocky is going to be working flat out, because with the rear end now lowered he wants to get the neat 70's mufflers on before having to do his commuting thing for another week!

We have temporarilly attached the sissybar arms. Next step is to mount our decorative poker tops...

Image
Being threaded for a 3/8 Whitworth thread is very conveinient. Just get three 3/8 bolts, cut the heads off and arras the cut end...

Image
Drill out the sissy bar tops to fit the bolt ends. They will be plug welded. Ie a 5/16yh hole will be drilled in the tubing and welded, thus locking in the bolts. This will need to be done in the drill press. Because our intrepid chopper jock has limited time, this step will be left until final welding.

Squaring up the sissy bar...

Image
Squaring up a sissy bar is a bit of a pain. Best way I've found is to get the bike perfectly level...

Image
A couple of long blocks of wood under the frame finished with a a wedge on each side levels the bike. They can move, so level of bike needs to be periiodically checked... purchase a couple of small cheap levels at your second hand shop.

Image
Clamp a level accross the sissy bar uprights and use a square to measure everything up...

Image
Adjust the sissy bar arms side to side until you get the inward leading angle of each equal. Mark top of level where square meets it and measure back and forth until both sides are equal.

Attaching centre post... top bar

Image
We will need two cross pieces. The top one could be straight, but let's be a bit different and make it like a 'V'. We could go one step further and convert the 'v' into a smooth curve. In retrospect, I wish I had! But a 'v' it is and we'll use some 3mm by 30mm flat bar.

Image
Work out the total approximate length of bar you need and mark the half way point with a square. Then work out the angle of the 'v' using a second piece of bar. Mark the line with your knife or marker. A texta is too thick for accuracy

Image
Use a protractor to measure the angle...

Image
Halve the angle and use your knife again to mark where the bar needs to be cut, so it can be turned into a 'v'
Image
Here's the cut out. Notice we've left some metal, so we can bend it and not have to try and join two pieces.

Image
We've used a 1mm blade in a 5" angle grinder to put a slice in each side of the centre post and now we slide in the 'v' ready for welding...

Image
Whole thing is squared up in the vice on the welding bench using an adjustable square.

BTW When buying a square always check that they ARE square, as they can be out by a couple of degrees. The way to check is by marking a line on a piece of steel using the square one way, then turning it over and marking again. If the two lines are perfectly on top of each other, your square is accurate. If not you will have to check both ways each time you use it.

Image
Here we have marked the lenghts of the v bars's two arms and now just need to cut them and weld the 'v' into place...

Attaching centre post... lower bar

Tail light/number plate assembly is to be mounted on the sissy bar, so bottom post support will hold the taillight/number plate bracket which will be a flat 4mm aluminium plate...

We'll use a piece of light 20mm steel angle. Centre post will weld neatly onto top face and taillight bracket will be bolted to the rear pointing face.

Image
Here you can see, we've drilled a couple of evenly spaced 5/16" holes into the rear face and nuts have been welded on. To weld nuts, hold them in place with a couple of bolts (tightened) to ensure they are in line with the holes and also stay square. You can also see that the top face has been shaped to fit the round uprights neatly... The more accurate the fitting, the better the weld.

Image
We've double checked that the bike is still level and are now getting the bracket leveled ready for welding.

Mudguard support

Now we need to support the mudguard. Mudguard in turn supports the sissy bar. Here we will use a piece of 1" x 3/16" flat bar. This bracket eeds to be thicker than other bar wev'e used as it is a major support.

Image
First step is to curve it to match the mudguard curve. You can neatly curve even ½" x 2" steel bar this way. Open the vice a bit larger than the thickness of the bar and bend slightly as you move the bar in the vice by small increments.

As this is a ribbed guard we will have to use a couple of spacers to avoid complex bends in the bracket. We also need a place to lock the double seat and will use the two bolts and the gap between the guard and bracket to do this...

Image
This cut out to match the sissy bar side posts began with a v cut with the angle grinder followed by more v's until there is not a lot of metal to remove with a file...

Image
Support is now fitted and trued measuring from the middle bar before welding...

Image
Guard is held in place while hole positions are marked using a special little marker I've made from a cheap small screw driver... you know, the type that bend in your fingers!!!

Image
Here are a couple I keep for various situations...

Image
Shiny spot on the guard is a centre punch mark where the hole has to be drilled. Punching and drilling cruved guards can be tricky. Because the metal is thin they can easily be drilled in a drill press while held in your hand... just clamp a piece of wood in the vice and rest the point to be drilled right over the centre of the wood block...

Image
Well... here's the tack welded sissy bar. It is attached with some button head stainless allen bolts. Spacers are temporarily some rubber bushes. Our chopper jocky will be using a temporary seat for a while as he wants to get other more major changes done first.

You can also see the taillight/number plate bracket has been made and attached, but we'll look at that in the next thread... Our chopper jock is on schedule... and the sissy bar is lookin' cool!
Chopit'nrideit... Prof

Post Reply

Return to “1980 gs400 Bobber”