32. Fork Brace...

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: 5749
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
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32. Fork Brace...

Post by Prof » Tue May 22, 2007 11:03 pm

Fork Brace...
I am combining a fork brace with the upper mudguard mount, so the forks could be kept nice and slim and tidy.

Got local engineering shop to bore the two holes for the lower fork legs. Challenge was also to have a tidy way of holding the fork boots (dust covers) on. After many hours of thinking and looking, I finally came up with setting the boots 8mm down into the brace with a spring wire inside them to push them out against the brace.

In the next pic, one boot is set into the brace. On the left you can see the wider section into which the boot sits. It is slightly under cut...

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Brace as I got it from engineer. Made from 1" thick aluminium. Aluminium cost $15 and he charged me $120 for the machining, although it should have been another hundred...

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Here the shape is marked out (Texta lines are for your benefit and get rubbed off once the photo is taken). As you've heard me say many times before first task in marking out is to set up a centre line and work from that.

Aluminium is easy to mark with a sharp instrument. As I've also said many times, I use a verniers as a marking tool for such things as the circles around the holes. The odd circular shape at the top is my guide for the central curve. I have collected a pile of circular shapes of varying sizes for just this purpose.

Markings at bottom are where the clamping bolts and slots will go....

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Angle ginder can be used to cut these out side curves, but blade does not like such thick aluminium and it tends to grab, tear and twist...

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Bandsaw does a much better job, but still suffers and over the whole job loses quite a lot of its "set" resulting in the blade tending to jam as well as get very hot. You can do same job with a hacksaw (The seventies way!), but it is slow. Another way is to drill a series of ¼" holes almost touching and then use hacksaw to join them up. Needs a lot of cleanup, but I've done it plenty of times in the past...

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Don't like the shape and change it. Will look much better...

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Use a centre line again to work out where bolt holes for clamping will go...

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Dotted black line shows hole angle. A set square is then used to line up brace for drilling. Firstly, I used a centring bit to ensure hole went where it was supposed to and didn't slide off line because of the angle. The 27/64's drill bit is used so a 3/8" UNC thread can be tapped.

Then to relieve an area for the socket bolt head... I don't have a milling machine or the right size cutter, so with care use a reamer (Oh sacrilege!) at slow speed. Even router bits will work in aluminium!

A bench drill and an xy table is an absolute must if you are planning to do your own work. More important than a welder.

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Next job is to cut the slots... two blade thicknesses. This is followed by tapping the threads. Because the holes don't go through to the other side and I want as much thread as possible for strength, I finish thread with a "bottoming" tap. It has no taper and so goes to within two threads of the bottom of the hole. Always tap coarse threads in aluminium... at least three times the bolt thickness if you can...

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45 minutes polishing and the job is done... I cheated and used coarse and then fine belts on the linisher to smooth out the cut surfaces. In the tight inner curves I used 180 wet and dry paper in an orbital sander. I also removed some deeper scratches from the flat surfaces with it. Just because you buy a tool for woodwork doesn't mean it can't be used in some cases on metal!

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Whole job took me 10 minutes under four hours including marking out.

Looks almost like a bought item... but it's one of a kind and that's part of what chopping your own bike is about. Tomorrow, after getting my knee x rayed to see why its being such a pain, I'll make up a couple of little stainless steel covers for the front wheel hub and then put fork brace and front wheel on.

Then I can make the front guard mounts...
Chopit'nrideit... Prof

Stoand
Posts: 316
Joined: Sun Apr 23, 2006 5:25 pm
Location: Adelaide

Post by Stoand » Wed May 23, 2007 10:07 pm

looks the business Andrew!...bit worried about the bandaid on the finger near the saw blade though :D

Biggaz
Posts: 172
Joined: Tue Nov 29, 2005 10:21 pm
Location: CoffsHarbour

Post by Biggaz » Thu May 24, 2007 7:20 pm

Mate your good you have definatly found you calling
Choppers Are Real Rides

Prof
Founder, Choppers Australia
Posts: 5749
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
Contact:

Go for it...

Post by Prof » Thu May 24, 2007 8:35 pm

Thnks Biggaz, but I'm showing this stuff so all you chopper enthusiasts out there will have a go. It's just having some equipment, ideas, knowing some basic principles and that most things you want to do can be done...
Chopit'nrideit... Prof

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