So I gather if you use thick wall square tube to build a more rigid arm than a stock GM, then you need to use a rubber bushing that has a large OD to allow the bushing to flex and not affect the arm or etc, like a bushing from a Chevelle or large GM car triangulated four bar suspension (75 Caprice, etc). Been thinking about something like this for several years.
I agree with you that the ability to articulate needs to be designed in from the get-go. Your setup looks pretty good although I can't see the bushings. To the person whose suspensions permits 4" of articulation, how much of that is in the bushings and how much in the arms twisting? The setups pictured elsewhere on this thread with wide small diameter bushings and short arms - and for all we know, hard poly bushings - will not articulate enough on the street. Maybe fine for a drag car but not on the street. If it can't articulate, the force has to go somewhere. It will be twisting your arms or axle tubes or frame. I know that sometimes hot rods have suspensions that don't travel much anyway, and that that can mask some of the articulation issue. But we are talking baggers here. Long arms, mounted as closely to the centerline of the vehicle as possible, with narrow but large diameter bushings that are soft enough to flex, is more along the lines of what you need. The 4x4 boys also have some fancy rod ends that are very strong and articulate nicely, as on the trail you want all of the articulation you can get.
If you are using tubing for trailing arms the front bushings need a lot of movement, check this thread out, some good information here: http://www.chevytalk.org/fusionbb/showtopic.php?tid/277609/ Hotchkiss sells a "Swivel Max Bushing Upgrade" specifically for 63-72 C-10: http://www.hotchkis.net/6372-c10-swivel-max-bushing-upgrade.html Also thought I'd post this, might help somebody contemplating using or modifying a truck arm set-up. Click here >>> http://talk.classicparts.com/showthread.php?t=20708
Jimenez Bros Customs. We have been doing 2 links for a few years now. Its good to see more and more of the here on the Hamb. We build them and sell them. 951-784-4772
Some expensive cars like Cadillac Seville and Chrysler used leaf springs with rubber between the spring and rear axle, would something like that help with flex and isolation? You would have rubber at both ends of the arm.
Here's a 42 Chevy PU I'm doing for a friend. I used a 46 Olds X-member with OEM trailing arms similar to Chevy truck. I stepped up the rear chassis 6" or so and added a 9" with coil overs.
On these trailing arms you guys take out of trucks. Does it matter if they are short bed or long bed arms. Didn't know if they were different lengths.
The arms are the same length, the crossmember position is changed for SWB vs LWB. Same arm for 1/2 & 3/4 ton versions but for a very minor gusset.
this is exactly what im on the hunt for to switch to open drive line..were you able to bolt the x member in or did you weld?
Listen and read Clark's ideas , from what I have heard about him , he has forgotten more than most hotrodders know !
GM used a fabricated I-beam, which isn't real good at handling torsion. They did this intentionally. The trailing arms need to twist, by design. The stock trailing arms were made from (2) press brakes c-channels, placed back to back. The 3/4 ton, C20's, had plates riveted to the top and bottom of the trailing arms to keep them from separating.
Great thread and info. I'm collecting all the trailing arm parts to do my 50 fleetline someday. Question though, what is the best pan hard bar design to hold the axle from moving side to side? Would i only need 1 panhard bar similar to the OEM design? Should it be in front or behind the axle? If i remember correctly, the pan hard bar should be level at ride height? Thanks HAMB Posted from the international space station & powered by the Full Custom H.A.M.B. App!
The best panhard set up is actually a watts linkage setup, keeps a constant roll center and keeps the rear end stay put !
Yup. They sure did. I have already given up trying to explain the dynamics of this system. There are far too many people here selling incorrect designs shouting me down. Solid trailing arms are not the correct way to do this. If you are selling them, you don't understand this system, and are shortchanging your customers. Crossing your fingers and hoping that your welds and construction methods are strong enough to withstand and incorrect design is a business model that I would never participate in. Good luck.
I forgot to mention the OEM Olds trailing arm setup I use are top hat design without a bottom reinforcing plate to allow for torsional twist, I presume. Bushings at front OEM bracket are large rubbers. The diff is rubber mounted fore and aft to the trailing arms with large rubber bushings top and bottom. Truck trailing arms I believe are solid mounted to diff. I've yet to add the OEM sway bar to the 42 PU setup as well as panhard bar. GM spent $$$ on R&D so I'll take advantage of it for this driver. Rear chassis needs a slight notch to inner edge to clear arm when cornering
I've also got the arms that are rubber bushed at the axle. Debating whether to just weld the piece that fits to axle as it is just U bolted now and assume rubber won't yield too much or tear or should I add tubes from top of axle to front of arms to make a ladder bar setup? Anyone done the first option with the Olds closed driveline arms when mounting a late open rear?
Forgot this, OEM Olds mounting brackets on 9". Actually similar to large 4 bars bushing with crush tube. 2 x HT 1/2" diameter bolts and large diameter washers each side.
Looks like the brake line is running down the left arm, so the flex line is at the cross member and it's all hard line from there back. That seems cleaner to me than having a longer flex line between the frame and rear axle, but is there any downside to this? With that much hard line on an oscillating suspension component, is there a risk of vibrational damage to the line? Maybe I'm over thinking things again. The hard line on my current rear axle has held up fine for decades... Posted using the Full Custom H.A.M.B. App!
I do a fair quantity of 4x4 work. That's how I run brake lines on long-travel stuff, and often on bagged cars, too. Flex line, wherever it moves, of course. Posted using the Full Custom H.A.M.B. App!
Thanks Gimpy. I know you've raised some concerns in the past over some truck arm style kits on the market, specifically about the rigid tube arms and the type of pivot joints and bushings used. I tend to agree with those concerns, but I've noticed recently the kit makers seem to be changing the pivots to a Johnny Joint style rotating pivot (almost like an over sized heim joint). Does this resolve the articulation stress and binding problems if the old design, even with rigid tube arms? PM me if you'd rather talk off line. Thanks Posted using the Full Custom H.A.M.B. App!
Might actually be worse with Johnny Joints. In order for the truck arm design to work properly, the arms absolutely must be made such that, under normal suspension cycling, they can twist, torsionally. With a rigid arm, the only hope of replicating even a scant portion of this function is by having a large, soft, compliant bushing at the front of the arm. A Johnny Joint, or similar, has NO MOVEMENT, other than spherical, and the ever so slight compression of the urethane "races" around the ball. There is no working with, or around, a rigid arm.
I fabricated these from 3mm (1/8th) for a '34 Tudor I'm busy with. Then found a complete C10 rear set-up a few weeks later! The transverse spring hangers (out of shot) are integrated into the back of the arm. Front mounts are about 8" apart, right at the front U-joint. Of course a shot with the chassis in place would make more sense but I don't have them on this computer...
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