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PostPosted: Tue Dec 11, 2012 2:26 pm 
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Joined: Tue Dec 04, 2012 7:19 pm
Posts: 27
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Location: South Africa
I had fabricated a set (4x) of these adjustable gas shocks coilovers for 3.5 times cheaper than cheapest set of oil filled Gaz coilovers 8-)

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Due to the fact that I was building my seven clone on a tight budget, a lot of thinking and effort went into doing most things on the car myself right down to body molds.
However, when I got to the coilovers shocks which are very expensive in my country, I simply had to find a way to build my own and which I can be proud of. Luckily I have a well equipped garage with a good collection of tools and machines gathered over 38 years an artisan which made it easier for me fabricating them.
The biggest problem was that the shocks commercially available (read affordable such as Gabriel and Armstrong) are not suitable to cut a groove for a circlip/snap-ring to keep the threaded tube and spring in place, because one need to cut at least 0.25 - 0.35mm into shock casing for the snap-ring to fit properly and after cutting open a few old Gabriel and Armstrong shocks, to find that is only made from 0.9mm steel tubing and at best not completely round when checked in lathe, leaving no room to cut grooves :shock:
I had to figure out another way and here is how I went about it.

But first, here is what you need;

1. Four suitable shocks - either oil or gas, but I used gas
2. Aluminum billet stock to cut the parts from - I used 50mm diameter x 600mm long for threaded tubes and 80mm diameter x 250mm for other bits.
3. or alternatively, use suitable stock outer threaded steel tube instead of aluminum.
4. Four coil springs of correct rating and length for car - I used 180lbs/inch rears and 245lbs/inch for front and car sits perfect height without adjusting.
5. Lathe with screw cutting funtion, but this is not critical, because machining can be outsourced to machine shop, or perhaps a friend can help out.
6. Lots of patience.

Here is my little lathe I used to fabricate the coilover parts with.
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Step 1.
Determine shock length needed - fully extended, collapsed and importantly ride height length from eye to eye. My car has my own designed suspension and when the car was set on preferred ride height, the front and rear shocks needed to be 310mm from eye to eye, in full droop 390mm. The shock I found suitable with my criteria was the old original VW Beetle ones from the 70's. It measured from eye to eye; collapsed 250mm and fully extended 390mm with stroke movement of 140mm available. Installed in car to normal ride height still leaves me with 80mm bump and 70mm droop that can handles any road.
However, old Mini shocks should be fine for most coilover conversions.

Step 2.

Cut the dust covers off the shocks like shown in picture below and remove burr.

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Step 3.

Determine where you want the bottom of the threaded tube to be to clear suspension brackets etc. Because the shocks I used is longer than normal I stopped the thread tube quite a bit up from the bottom of the shock to kept the springs short and compact and save weight by doing so, but its a personal preference.
To form a depressed ring into the shock casing (shocks innards clears casing by approx 6mm all round) I welded a piece of 8mm stainless steel round bar to a length of 10mm square bar like in picture below and when turning the shock in the lathe, form the ring by friction forming,IOW, just press the round bar tool hard and fast against the shock casing with some lubricant until desired depth is reached. I went in 4mm max.

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Grooves rolled - in this pic I used a flat end tool and scrapped these shocks as spares and made new rounded grooves on new set.
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Step 4.

Cut the following parts for coil overs from aluminum billet.

1. 4 Tubes of suitable length to slip smoothly over shock casing with outer thread - I used 2mm metric thread.
2. Cut/shape 4 nuts to screw over threaded tube with shoulder that pushes about 8mm inside of spring to centralize it. This must be within 1mm tolerance. I used round holes to adjust the nut instead off shaping it like some commercial ones because I have no access to a milling machine and preferred to keep it simple.
3. Cut 4 top spring retainers from ally with shoulder that pushes into spring to align it, with recess for shock cap to fit in and slot for shock shaft to pass through.
4. The "Lock halves". Turn rings on lathe like and L shape when cut through and view in profile to seat into rolled grooves and overlapping the casing as in pictures Cut this ring in half so it become two half shells.
5. Cut "Ring Lock" from ally that will fit tightly over the the "Lock halves" before the lock half is split as mentioned above. Recess 3mm into top of "Ring Lock" for the threaded tube to fit into and aligning it perfectly - see pictures for detail.
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Step 5.

Assemble the coilovers.

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Shock with parts to complete
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Parts placed in position on shock - note the way the ring lock half shells fit
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Ring lock shell/casing going over the ring lock half shells. This is a tight fit and has to be lightly tapped over with piece of wood and hammer.
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and here is a pair over coilovers assembled and await anodizing and springs.

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Parts anodized
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And here is the completed adjustable coilover fully assembled with coil spring fitted
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Finally, remember to fit a grub-screw to the adjuster nut! I drilled and tapped mine in one of the adjuster peg holes to be out of sight.
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Within a few days I will post another episode with a step by step pictures and description (with formulas etc) method on how to anodize your coilovers when made of aluminum in any colour or natural and can also be used for other ally bits and pieces on the car. Very simple and easy to do - will also show different of ways getting it done without funny equipment, hillbilly style.
Later I will add another episode showing how to do copper, tin and nickle plating without expensive equipment (will include formulas as well) for those who made their coilovers from steel or wanna plate some bits on suspension etc.


Attachments:
Lathe.jpg
Lathe.jpg [ 41.47 KiB | Viewed 1958 times ]
lathe2.jpg
lathe2.jpg [ 38.81 KiB | Viewed 1958 times ]
CutGabrielshocks.jpg
CutGabrielshocks.jpg [ 35.46 KiB | Viewed 1958 times ]
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