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Front Coilover Suspension in Progress

I am in the early stages of building a link type front suspension for my 76 Chevy Truck. For springs, I've considered Coilovers, Coils, and Quarter Elliptic. For link arrangement, I've considered || || with a Panhard, |/\| (3link), or wristed/non-wristed radius arms.

Spring Option #1: Coilovers
Pro - Ultimate Control an Tune' ability. simple mounting and small diameter - easier to fit, no big perches and such, and more room for linkages around them.
Con's - Cost of springs and shocks and getting them tuned.
Approximate Cost of springs and shocks = $1200

Spring Option #2: Ford Bronco Coils
Pro's - Easy to come by, easy to adjust ride height, good ride, and light weight.
Con's - Everyone is doing it, and I have done it too, (rear suspension on my rig has XJ coils and |\ /| (4 link))
Approximate Cost of springs and shocks = $700

Spring Option #3: Quarter Elliptic
Pro's - I've never seen a rig with quarter elliptic front suspension, so that would be cool IMO. The springs would be free.
Con's - I'm not a real big fan of the quarter elliptic Idea, and the weight is much greater than a bronco coil. My rig is already front heavy as it is.

Link Option #1:   || ||   with a Panhard Bar.
Pro's - This type of suspension can handle greater side loads than a conventional |/ \| suspension. Easy to design and fabricate.
Con's - Old school design, and has more inherent bind than triangulated suspensions.  One more link to deal with, therefore 2 more heims to buy and more tubing. more mounts to fabricate.

Link Option #2:   |V|   (3 link)
Pro's - Proven design, that offers good axle control and articulation.
Con's - I better have a good mount for the front of the V, and I will have oil pan/exhaust, and Driveshaft clearance problems. Also with Full Hydro Steering, I don't think this design will be strong enough using conventional methods.

Link Option #3:   Y |   (Radius arm, and single straight lower with a Panhard Bar / Track Bar )  
Pro's - Easy to design and fabricate. Very Flexible
Con's - Somewhat unproven in large vehicle applications

Here is the first trial rendition of what suspension geometry I was going to use. Like the broomsticks? From the mocked up links I came up with the above CAD drawing and started doing figuring out how long the lower link would be in order to get adequate pinion movement to prevent driveline bind at full droop. I wanted to use a 3 link with a Track Bar, but while trying to figure the geometry out, I figured I might as well just do a radius arm instead. My final decision is to run something similar to what many people are running on XJ and ZJ long arm suspensions.

I've not wanted to do this style of link system because it doesn't have more than 2 attachment points at the frame (other than the Panhard) But after thinking about it for a while, I realized that my current front suspension (Leaves) doesn't really either.  I'm a bit worried about breaking a mount or a bolt, and having the axle bottom out the Driveshaft and break the t-cases loose from the tranny, but all the mounts will be double shear so It shouldn't be a problem.

I will be making my brackets and links somewhat modular, so that I can remove either upper control arm (UCA) to see how the suspension will react on the trail. I will also make the brackets at the frame bolt on so that I can bolt on brackets for a regular 3 or 4 link.
 

Here you can see the coilover shocks I decided to run. They are 14" travel, 2.5" Diameter Body, Remote Reservoir, with 350/500 springs. This combo will provide me with a 205 in/lb spring rate until they hit the "Kick out" or the upper coil binds, then the rate will be 500 in/lbs. I'm considering designing and machining some new Coil Hats to retain the coils. Sean Stapley and I have been talking out this, and I think that adding some resistance to Droop would make a coilover truly the ultimate shock.

I made these brackets from a piece of 1/4" mild steel plate, they are probably overkill and should have used 3/16" to save some weight. I will plate the front and back to provide more rigidity, and might tie them into the steering cylinder mount. These brackets position my links with the lower at the axle centerline, and the upper 9" above that, Center to Center. I wanted to have as much vertical separation as possible to prevent axle wrap and to get better suspension geometry. 

I mocked these pics up to show the final relationship of the arms to the frame and body. I need to design a new cab mount that can tie into the rocker panels and exo cage that are in the works.

1.5" B7 hardened threaded rod

The leaf springs were held on by one solid mounted 9/16" bolt on the front of the leaf, and one moveable shackle and 9/16 bolt at the rear. BUT the rear moveable shackle only supports the weight of the vehicle. the front bolt does all the fore to aft locating of the axle. All the weight will now be supported by the coilover, so in my mind, the 9/16" bolt will be seeing no more load than it did with the leaf springs. Less actually, because there will be no twisting forces, and no side loads. My rear suspension is located completely by four bolts at the frame, this one (the front) will be located completely by 3, and none of the 3 will be sharing combined loads like the rear.

   
First Design

This suspension will have 6" of up travel before the shock bottoms out. Since I cant afford to ruin a 500 dollar shock by bottoming it out, the last 2" of travel will be into the bump stops. The last 3/8" will hit steel before the shock hits.

After much deliberation, I decided to sacrifice some ground clearance to get more tire to control arm clearance. I moved the frame mount for the control arms to underneath the frame, and changed the mount location for the upper arm. (shortened it by 10.75") So now the upper arm mounts at the center of the lower arm. I didn't want to do that cause it might cause the lower arm to bend down there. But the advantage is that it will also act like a support to prevent the lower arm being bent up by rocks, and stumps. It also gives me greater frame clearance.

The axle brackets are still configured the same as before, with 9" of vertical separation. If they interfere with the frame at max articulation I can cut the frame off at the vertical yellow line, and fabricate a custom frame from there forward. I would definitely not have room to do this if I was going to use the factory sag steering box. Since I'm using a full hydro steering system, I can mount the orbitrol valve anywhere I need.

   
Second Design

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