7. Seat base...

A blow by blow photographic account of chopping from stock to chop... This projcet has been given its own forum due to the large number of photos it contains making uploading slow for those of you still on "dial up".
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Prof
Founder, Choppers Australia
Posts: 5791
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
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7. Seat base...

Post by Prof » Mon Nov 06, 2006 10:16 am

Building the seat base...
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Seat base is marked out on 3mm aluminium sheet... rigid but light... cost about $20.00. I copied dimensions off cardboard template... always working from the centre line. Piece of kitchen wrap allows me to trace curve and copy it exactly to other side. Shape is then cut out on bandsaw with a bimetal blade... goes through it like butter! You can use a jig saw with fine blade, but it is hard work. Angle grinder with 1mm blade will work but grabs badly in aluminium. I clean up edges with a linishing machine (Multitool that attaches to your grinder is a valuable addition to your workshop) but file works fine on aluminium... does need cleaning out with a wire brush regularly though.

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Bending is done on home made bender, Angle gauge gets angles correct, then check on bike and make any further corrections...

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Bent up base. High back is a separate piece because it needs to come below passenger base to be supported by mudguard. Two pieces will be bolted together with 3/16 countersunk bolts. I prefer them to rivets as they are stronger and can be pulled up tighter...

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Side pieces are drawn up and cut out. Tabs are bent with hammer, vice and angle iron. On longer bends you should use G clamps to keep bends uniform. When bending this way, don't try to hammer tab down flat but do at least 5 full length runs to graduallly pull aluminium down. This reduces distortion. With a hammer you do get bruising. This is the second to last run.

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Sides now finished and ready to attach. I use a vernier calipers extensively for measuring... it is especially useful when used as a marker... eg, when measuing a series of drill holes; set distance from edge and run it down length of sheet. Aluminium marks easily. When using steel, blacken area to be marked with a texta.

Back rest has been bolted on and front mount cut out. This slides over stock Sportster tab. See next picture. To cut this hole out, I drilled two holes diagonally opposite and used a jigsaw. Old style jigsaw where you hold the motor rather than a top mounted handle is easier to control with aluminium. This one was bought in 1969 the year Easy Rider came out and I built my first King/Queen seat!! You can use a keyhole saw or modified hacksaw blade if you have no jigsaw... but jigsaws are pretty cheap at Bunnings. Use a very fine blade to reduce chatter.

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Finished seat base. Fits perfectly with very little mucking about. Whole job including making patterns took 4 hours.

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Backrest fixing is a heavy duty brass wardrobe/drqwer lock. I've pulled it apart and modified it so it needs a different style of key... just to make it a bit tougher to get off! 3/16 couner sunk bolsts are pened over to prevent loosening through vibration.

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Tab yet to be built on sissy bar goes though slot and lock tongue holds it in place.
Chopit'nrideit... Prof

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