Bent or rolled?

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    Bent or rolled?

    So my Rangie has reached the limits of the rear trailing arm bushes, leading me to look into 'cranked' trailing arms. For those not familiar with the land rover set up it is fairly common to fit cranked arms to allow the chassis end bush to sit in its neutral position at a higher than standard ride height, allowing more droop.
    there are plenty of manufacturers that make some slight variation on these:
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    ​​​​​​So I was thinking to make my own, but it occurred to me that a gentle ark should be stronger than a single bend, shouldn't it? It's not unheard of for these to bend, I'm happy to make them beefy, but I don't want them unnecessarily heavy.

    #2
    Might be worth while to look into making it more like a trailing arm. Bend it like above then plate it similar to a trailing arm to brace it.

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    88 Ford F-turd50 IDI Crawler

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      #3
      If you're going to make your own control arms anyway, are you opposed to getting rid of the stupid bushings at the frame side, and do something more normal? Then you could keep straight (read: stronger) links.

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        #4
        Cheers for the replies. I should be clear that it's a fairly mild offroader on 32" tyres, not a rock bouncer or KOH racer, so I don't need to go too over the top, but I don't mind the idea of bracing the bend for strength.
        I wouldn't be opposed to changing the chassis end bush, but it is street registered and getting an engineers cert for chassis mods is a PITA in Victoria. Not that I'm super concerned about legalities, but I do like being able to bolt standard parts back on if the need arises.

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          #5
          Originally posted by A4L7E3X View Post

          ​​​​​​So I was thinking to make my own, but it occurred to me that a gentle ark should be stronger than a single bend, shouldn't it? It's not unheard of for these to bend, I'm happy to make them beefy, but I don't want them unnecessarily heavy.


          It really depends on the material diameter and wall thickness you are planning on using.

          Once you bend metal, it will be weaker at the bend, so you need to build them strong enough to handle your intended abuse.

          Back when I was running Wild West Off Road, we built and sold 100s of cranked arms for 80 & 100 series Land Cruisers, 4Runners and FJ Cruisers and never had any of them come back damaged. They just had a simple bend in them (and were built from 3/8" wall tubing).


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          The main advantage of having the bend in them is that you will not hit them on rocks and ledges as much as a straight arm, which is why they bend in the first place.


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          Last edited by Tech Tim; 06-05-2020, 06:09 PM.

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            #6
            Originally posted by A4L7E3X View Post
            getting an engineers cert for chassis mods is a PITA in Victoria. Not that I'm super concerned about legalities, but I do like being able to bolt standard parts back on if the need arises.
            In theory, a rolled bend should be stronger than a drawn "typical" bend, but the differences would be miniscule for the bend angles you're looking to do. Bang-for-the-buck is probably in just using heavier wall material or larger diameter material to get the strength you need.

            I'm curious, with the wait/trouble you guys have for an engineer's signoff, it would seem you're short on engineers. What's it take to become the "right type" of engineer for that, there?

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              #7
              Originally posted by ScottRS View Post

              In theory, a rolled bend should be stronger than a drawn "typical" bend, but the differences would be miniscule for the bend angles you're looking to do. Bang-for-the-buck is probably in just using heavier wall material or larger diameter material to get the strength you need.

              I'm curious, with the wait/trouble you guys have for an engineer's signoff, it would seem you're short on engineers. What's it take to become the "right type" of engineer for that, there?
              I looked into it years ago, it's not too bad - 4 years of school if you knuckle down hard and get it done.

              The problem is getting onto the list of approved signatories once you're qualified.
              The registering authority has a short list of engineers they'll allow to sign off in each region. In some places you're literally waiting for some old dude to die so you can be added to the list.

              The system works OK for the end user. If the work is good and within the allowable modification guidelines there's usually no drama. Most people you hear of having problems are trying to get something ticked off that's specifically outlawed, or they haven't involved the engineer from the start and just expect them to trust that everything that's welded shut and can't be inspected properly is what they say it is...

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                #8
                Originally posted by ScottRS View Post

                I'm curious, with the wait/trouble you guys have for an engineer's signoff, it would seem you're short on engineers. What's it take to become the "right type" of engineer for that, there?
                The other factor is some of the arbitrary rules that we have. For example the chassis end bush on a land rover is welded down the side and across the bottom of the frame rail, which is perfectly fine for an OEM to do, but any mods prohibit welding on the top or bottom of a frame rail.

                I agree that the system isn't too bad in that it does tend to keep most of the death traps off the roads, but the hassle is too much for simple changes so most guys tend to fly under the radar, either sticking to 'approved modifications' that don't require inspection, or just trying to make it look as low key as possible.

                The other problem I see is that, aside from some race events, we don't really have anywhere to drive unregistered vehicles off-road. From what I gather in the US you guys can trailer your unregistered Jeep out to a trail then have at it, but here if your on public land it has to be registered.

                That's why you don't tend to see much bigger than 35" tyres here, under the approved modifications you can only go 50mm larger than the largest tyre plated for that vehicle.

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                  #9
                  Originally posted by A4L7E3X View Post
                  I agree that the system isn't too bad in that it does tend to keep most of the death traps off the roads.
                  I call BS on that. I've seen MadMax.

                  Check out my project
                  https://irate4x4.com/general-4x4/2779-amphibious-hemtt

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                    #10
                    Originally posted by Tech Tim View Post

                    Back when I was running Wild West Off Road, we built and sold 100s of cranked arms for 80 & 100 series Land Cruisers, 4Runners and FJ Cruisers and never had any of them come back damaged. They just had a simple bend in them (and were built from 3/8" wall tubing).
                    Considering the kind of use the average lifted Toyota SUV sees you'd probably have to sell thousands before any of them will actually get wheeled.


                    Originally posted by A4L7E3X View Post
                    I agree that the system isn't too bad in that it does tend to keep most of the death traps off the roads, but the hassle is too much for simple changes so most guys tend to fly under the radar, either sticking to 'approved modifications' that don't require inspection, or just trying to make it look as low key as possible.
                    Oh fuck off. Nothing rusts in your desert shithole. Inspections aren't about keeping things safe, they're about keeping the poors off the road.

                    Also I don't think you realize how far most people travel to be able to drive off trail-only road rigs.

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                      #11
                      Originally posted by arse_sidewards View Post

                      Considering the kind of use the average lifted Toyota SUV sees you'd probably have to sell thousands before any of them will actually get wheeled.

                      .

                      Yep, no Toyota owners wheel very hard.... 'Cause Toyotas make it easy....

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