02. Build #1... Rear end... Struts

Don't ever say you can't afford to build a chopper!!! This thread will prove you wrong
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Founder, Choppers Australia
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Location: Willunga, South Australia

02. Build #1... Rear end... Struts

Post by Prof » Fri Jun 13, 2008 12:37 am

AS we said in our introduction, this series is show that anyone with a few basic tools and a small amount of cash can build a chopper that will turn heads.

It doesn't take a lot of money to produce an 'outasight scooter'... just being able to think out side the square and do some planning....

The tools needed to do the entire chopper are a drill (preferably a bench drill, but it is not essential, an angle grinder or hacksaw an arc welder and spanners, pliers etc.

The Rear end...
Easiest away to lower a rear end is with struts, so let's have a look at the steps required for good looking safe struts...

Firstly find some suitable material...

Here are some possibilities... 5/8"round bar, hex bar, square bar. 1½"x½" flat bar. These could also be in stainless. Next is 3/4" round or square tube. Tube needs to have a wall thickness of 1.6mm-2mm and will need crush tubes...

One style of crush tube. Tube can also be welded to top of strut (see Chops 'n Bobbers article mentioned below).

Next are a couple of more novel ones... Chain is not a good idea unless you know a very competant welder. This next is the one I've chosen. It is simple to make and it's a head turner... the internal thread from a Hills Hoist... worn out hoists cost a pittance.

NOTE: 60's and 70's choppers were mostly made to look different with tricky little stuff like this rather than fancy frames and wheels and expensive paint jobs. This is a budget job that ANYONE can build so well keep it 60ish and simple...

This one also has possibilities... it's an auger bit off a chain saw style auger. It would need a competant welder to put suitable ends on it. But that costs money and money we ain't got, so we'll give it a miss but keep it in our mind for the future.

If your struts give way on a heavy bump with a pillion at speed you are in dire straights. You will be barrelling out of control with a locked rear wheel and could end up anywhere!!! The sizes I've quoted will be strong enough for any chopper/bobber. See more information in April-July 08 'Chops'n Bobbers"...

Remove the shockers and drop the bike down until it is 4" off the ground. This is the minimum height required by ADR's. If you are putting a 16x5 wheel in note that it is 1" less in radius than an 18x4 and so will drop your bike another 1".

Make sure rear wheel will clear everything by ½" when dropped this low and that you can still fit a guard. Check also that the chain will not foul swing arm pivot as on a modern bikeit is probably an inch or more lower than if the rear shockers were fully compressed.

Move your wheel to the forward and rearward limit of its adjusment to make sure it clears the guard at each end.

Note also that side stand may now be too tall making the bike tip over or stand too upright to be safe. Easiest answer here is to cut it shorter and weld a piece of flat plate on the bottom to stop it sinking into the ground. Later, when you extend the forks, find another stand or cut it again and weld another piece on the right size.

In our case, bike just stands up, but falls pretty easily. However before it is ridden much I will have a 21" front wheel on and that will keep it upright.

When using a tape measure begin at 100mm mark to be accurate. The tab on the '0' end moves. Always measure from bolt centres

Holes need to be in the centre of the strut, but how do you measure something so uneven? Easy! Put it in the vice and you now have a guideline each side. A verniers is a very valuable toolfor measuring and marking. A dividers will do the same job. Another way to find half way points is a piece of paper. Rub your finger along it on each side of the vice and fold it in half, then centre punch it.

Buy a 3mm centre bit if you want to get accurate holes. You need to run it down far enough to start opeing up the initial hole so your drill bit doesn't wander. A 3/8 bit will wander 2mm before you can say boo! so be very careful.

Other problem is to get your two holes parallel on any material that is not square. Best way is drill first hole and then put the drill bit or a piece of tight fitting rod into it to line up when you drill the second hole. If you don't get these square, you'll never fit ithe strut on the shocker mounts.

Once the holes have been drilled, the struts can be cut to length. Leave a minimum of ½" above the holes and tidy up with a file. I cheated and used a modified 'Multitool"... a great birthday present from the missus.

Well that is about as far as our intrepid biker would get on the first week end unless he was a quick worker and had everything pre planned. So he would now wack the shockers back on the bike ready for Monday... though he'd probably rip off the indicators and anything else he could do without for a week.

Next weekend is now here... and Friday night he gets stuck into it ready for a big couple of days so he can still have a road worthy bike next Monday!

The big cut...
He is now committed to permanently changing his bike as it begns it road to unsurpassed beauty under his creative direction...
Chuck out the old guard and seat and put on the struts. Use your angle grinder or hacksaw to remove rear protrusions and un-needed brackets on the rear end.

Here are some bits and pieces... seat mounts, air intake stuff etc

This old piece of guard will be wide enough for the 4" rear tyre and is a classic so it is rested on some 15mm x3" wooden blocks to give tyre clearance. Then the uneeded frame side bars are cut off. A sissy bar could be bolted onto the top of these or in this case will be slid up the open ends of the cut frame...

Here's our rear end so far. A big drop in height and a clean light rear end.

Here's some of the rear end stuff we've junked. Mufflers are for effect as the bike had none with it. Originals were larger...

Saturday morning early it will be all systems go as we mount the guard and make a very cheap and eyecatching sissy bar... though the lady of the house will not be impressed, cos I nick something she uses all winter...!
Chopit'nrideit... Prof

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