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  • #16
    Re: Roadster Front Suspension.

    You may be right, I got the info off the JHL site for the front coil-over kit and the info on the Axle Tie bar kit from some digging around I did a couple of years ago.

    Adrian

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    • #17
      Re: Roadster Front Suspension.

      Originally posted by Robert in Cumbria View Post
      A Watts linkage and anti tramp bar at the o/s or both sides would get the job done. Welding brackets to the axle on spreader plates would be the way to do it.

      A couple of pix of a Rally Marina anti tramp bars. Not rocket science but for normal road use I question the need with an 1800 engine.

      [ATTACH]3047[/ATTACH]

      [ATTACH]3048[/ATTACH]
      Very nice easy set up and one to bear in mind, I'm more concerned about sideways location really.

      Brian.

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      • #18
        Re: Roadster Front Suspension.

        Hello Steve,
        Sorry but I've been unable to open your message. You can e-mail me though at [email protected] Thanks for all the useful stuff you've posted , much appreciated. My torsion bars are the heavier 20.6 mm which may be part of the problem.

        Brian.

        Comment


        • #19
          Re: Roadster Front Suspension.

          There was a discussion recently about a claim that the Mk 2 Marlins were pre-fitted with a mounting for a Panhard rod. Eventually it was decided they never were all fitted with the mounting. I don't think the single locating rod is a good idea because it has to cause stresses in the suspension as the axle moves up and down, it is forced sideways a bit too, which is OK with coil springs but not good with leaf springs, that is why I feel a Watt's linkage is better and not a lot harder to make. It allows the axle to rise and fall with zero sideways movement.

          A site dedicated to animation of mechanisms, pneumatic, hydraulic and electronic components


          This diagram shows the sideways ark movement with a Panhard Rod.

          images.jpeg

          With a light car like the Marlin and relatively stiff sideways location provided by the leaf springs I doubt the chassis will move more than a millimetre or two sideways relative to the axle under the hardest cornering. A set of polly bush bushes will make more improvement and will cost (and weigh) significantly less.

          Think about it this way... I am told there are about, roughly 1500 Roadsters out there, very few have Panhard Rods fitted despite them being announces as a standard available mount. If they were essential or even desirable, everybody would have had one.
          Last edited by Robert in Cumbria; 23-01-13, 10:55 PM.

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          • #20
            Re: Roadster Front Suspension.

            Hi Robert I have had a car that I put panard rod on and have had lots of roadster without. Do not underestimate the difference one makes until you have tried it. The difference is like night and day

            Comment


            • #21
              Roadster Rear Suspension!

              A member 'mlincsmit' did fit a modified Frontline Midget Rear Traction Control Link http://www.frontlinedevelopments.com...dget/rtl.shtml and documented it on this forum at





              Frontline rear link.jpg

              The linkage is quite clever as it allows for vertical movement of the axle but any lateral force on one side is counterbalaced on the other.

              It looks as though he has not contributed on this forum for nearly a year so he may no longer be a member or respond to PM or contacts through the MOC.
              Attached Files
              MOC member since 05/97
              1984 Marlin Roadster SWB.
              1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
              Three core radiator, Renault Clio vented front discs.
              The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

              Loads of Marlin Reference can be found documents here or there.

              Comment


              • #22
                Re: Roadster Front Suspension.

                Originally posted by CosworthCabrioLee View Post
                Hi Robert I have had a car that I put panard rod on and have had lots of roadster without. Do not underestimate the difference one makes until you have tried it. The difference is like night and day
                That's interesting Lee, I would have thought the broad leaf springs would have provided plenty of sideways support. There is no substitute for trying these things out. I still think a Watts linkage would be better such as Steve has drawn attention to above. That is very clever and neat.

                However, I keep coming back to the fact that the standard Marlin seems to work well enough, especially if it's well maintained. Methinks if ultimate performance were the goal I would be starting some place else. I am here for the robust platform and to resurrect an old friend.
                Last edited by Robert in Cumbria; 24-01-13, 10:19 PM. Reason: missing word!

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                • #23
                  Re: Roadster Front Suspension.

                  Having been prompted by Mr G I'll pick up on the question of torsion bars...

                  If you analyze the suspension frequency of the larger diameter bars vs. standard saloon rear springs you get a sub-optimal setup. Normally theory says the front/rear frequency should be c5-10hz different with the bias towards the rear. With heavy duty bars in the Roadster you get precisely the opposite...the result, at least insofar as I observed, was quite choppy handling. The front was like a roller-skate, but performance through the B-road twisty bits left a lot to be desired. I found swapping to standard saloon bars made a difference, though IMHO its still not perfect...if time/budget ever permit I'll go coilover front & rear & be able to get spring rates optimised.

                  As regards a Panhard, having driven the car with & without a Panhard I'd definitely recommend the "with" option...as Lee says you can feel the difference. The amount of sideways movement is quite significant, even with poly bushes, and a Panhard reins it in nicely. It may not be the "best" option but its the easiest to fit...just keep the axle mount low (below the casing and as close to the spring as possible so keeping the roll centre low) and the rod as close to parallel with the axle as possible (not easy given the shocker & handbrake position).
                  Marlin Roadster, LWB...1860 B Series + Ford Type 9
                  Renault Espace 54mm front calipers, vented discs, cycle wings and adjustable tie-bars.

                  Comment


                  • #24
                    Re: Roadster Front Suspension.

                    Just as a matter of interest, and I may be missing the point, but - what is wrong with the Marina front suspension? As it is, the car is fun to drive and can be thrown around predictably; unless you’re trying to shave tenths off around a track in competition why bother with the expense & downtime? What more can you want?

                    Now, better brakes and Steve’s Clio conversion are a different matter and probably worth investing time and money in…

                    Comment


                    • #25
                      Re: Roadster Front Suspension.

                      I don't think you are missing the point but not all Marlins are sorted to the same degree. Brian, the OP (original poster) was concerned about the overly stiff suspension, vague handling and wayward back end.


                      It seems the car was fitted with the (stiffer) van torsion bars in the original build, which won't help, who knows what back springs and dampers? So the OP did have a problem with the handling because the original builder didn't foresee or address these points during the build, he used what he had from the donor vehicle, a van. So it has poor handling as a result. That may not be the case with every Marlin but many will have been built by people who thought the donor parts would all be OK. That isn't always the case.

                      The previous owner of my Marlin complained to me and warned me about it's wayward back end and it's only a 1275. That was built from a van too.



                      This has prompted the OP to consider many options, including perhaps 'better' suspension. As has been pointed out a well sorted standard Marina suspension it fine for normal road use and standard power output.


                      To me the Marlin chassis is a basic and robust platform which allows a wide variety of suspension, engine, transmission and customisation mods. It can be whatever you desire. I don't think there is anything wrong in exploring the options or even carrying out mods if that's what floats your boat, provided the snags and possible downsides are considered carefully first, no point in making it worse!

                      My tupence worth.

                      Comment


                      • #26
                        Re: Roadster Front Suspension.

                        I hope this retains it's formatting.

                        Since reference has been made to rear spring rates below is a list of all the Leaf springs that I am aware of that will fit a Marina.
                        These will have been the original as manufactured rates, after 40 years in service, their rates could be very different.
                        Draw your own conclusions.

                        part no rate free camber leaves Notes
                        21H 6039 130 5.94" (151.0%) 3
                        21H 6269 130 5.93" (150.6%) 4
                        21H 6434 113 4.7" (119.3%) 2 Austin Marina Canada Only
                        21H 6436 165 5.81" (147.6%) 4
                        21H 6438 225 5.43" (138.2%) 4
                        21H 6440 130 3 Police and Estate
                        21H 6442 130 4.37" (111.1%) 4 1.5 diesel
                        21H 6707 100 2 1300cc Except when Heavy Duty Pack is fitted
                        21H 6714 113 2 1800cc Except Estate
                        C-AHT 459 140 3.11" (78.9%) 5
                        C-AHT 499 163 4.45" (113.4%) 6
                        C-AHT 573 140 2.75" (69.8%) 2
                        Also I have a MK2 parts book with spring info......
                        FAM 1126 225 10 cwt van and pick up
                        FAM 1507 165 7 cwt van
                        FAM 2044 130 4 1800, Estate and 1.5 Diesel. Heavy duty pack

                        Edit: formatting lost, I hope you can make sense of it


                        Just typed it out as a table to make it more readable.

                        Part No Rate
                        lbs/ins
                        Free Camber No of Leaves Notes
                        21H 6039 130 5.93" 151.0% 3
                        21H 6269 130 5.92" 150.6% 4
                        21H 6434 113 4.69" 119.3% 2 Austin Marina Canada Only
                        21H 6436 165 5.81" 147.6% 4
                        21H 6438 225 5.43" 138.2% 4
                        21H 6440 130 3 Police and Estate
                        21H 6442 130 4.37" 111.1% 4 1.5 diesel
                        21H 6707 100 2 1300cc Except when Heavy Duty Pack is fitted
                        21H 6714 113 2 1800cc Except Estate
                        C-AHT 459 140 3.11" 78.9% 5
                        C-AHT 499 163 4.45" 113.4% 6
                        C-AHT 573 140 2.75" 69.8% 2
                        FAM 1126 225 10 cwt van and pick up
                        FAM 1507 165 7 cwt van
                        FAM 2044 130 4 1800, Estate and 1.5 Diesel. Heavy duty pack
                        Last edited by stevejgreen; 27-01-13, 04:27 PM. Reason: vBulletin does not copy from MS Word correctly
                        MOC member since 05/97
                        1984 Marlin Roadster SWB.
                        1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
                        Three core radiator, Renault Clio vented front discs.
                        The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

                        Loads of Marlin Reference can be found documents here or there.

                        Comment


                        • #27
                          Re: Roadster Front Suspension.

                          Pity about the formatting but it's readable. A technique I tend to use to retain formatting is to take a screenshot of the formatted table then insert as an image... The trouble is PHP tends to strip all spaces and anything which isn't text. :-(

                          Any further info on the last three? I have 3 Van springs, which may be 10 cwt, the free camber may not be correct but the number of leaves will be. The thickness of the leaves varies too. I will take some measurements later, when the snow clears a bit.

                          How (where) is the free camber measured in this case?

                          My instinct would be to place a straight edge on the centres of the spring eyes, and measure to the top of the top leaf by the centre bolt, is that correct?

                          Comment


                          • #28
                            Re: Roadster Front Suspension.

                            Annoying, it looked fine when I composed the post.
                            It's a common problem with Forum software perhaps I will prepare it as a PDF.
                            The vast majority of Roadsters will be 2 leaf springs, either 21H 6707 from 1300cc and 21H 6714 from 1800cc donors. I guess they would be almost impossible to tell apart after 40 years of use.

                            Sadly I can offer no better explanation of the test methods.

                            Any further information describing leaf thickness etc. would be useful.
                            MOC member since 05/97
                            1984 Marlin Roadster SWB.
                            1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
                            Three core radiator, Renault Clio vented front discs.
                            The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

                            Loads of Marlin Reference can be found documents here or there.

                            Comment


                            • #29
                              Re: Roadster Front Suspension.

                              Thanks every body for some very interesting posts.

                              "Lil Red Road Roadster" comes up with some good figures that support my own empirical observation and I wondered if anyone had tried recording the front and rear weights to get a ratio, my guess is about 55% front and 45% rear which would be about ideal. If anyone had done corner weights that would be interesting too.

                              "Stevegreen " came up with some very useful stuff on sring rates and the lovely Watts linkage that Frontline have, I had been looking at their nice Panhard rod kit for the MGB which has the spring mount ready made for the Marlin as the bolt pattern is identical. My experience is that they do work even though the geometry isn't ideal.

                              I'm not looking for "Seven " type track day handling as I deliberately chose a Marlin for it's rather more classic chassis and probably handling. However it doesn't do what it should as it stands because it has a mismatch of parts and was built in my case with low expectations for other than straight line performance, and even that was a bit worrying

                              I think "Lil Red Rooster's"r conclusion is right that coil springs on the front with a proper load distribution to the chassis and a properly located cart spring rear is the answer.

                              Regards, Brian.

                              Comment


                              • #30
                                Re: Roadster Front Suspension.

                                Hi Guys,
                                It's great how these threads evolve. It's what makes the forum such a good and valuable place to view. Unfortunately I have tried to reply to Brian's original post several times without success so if it fails again I will give up! I too was not entirely happy with my Roadster's front end as I thought it was rather stiff so I went down the route of removing the torsion bars and replacing them with coil-over dampers. In fact the two photo's on this thread are of my Roadster's front end. In my opinion the car handles so much better than with the torsion bar set-up.
                                It was suggested a little while ago that the Eye Bolt in the second of the two pictures looked distorted and perhaps was a result of removing the torsion bars. However, I think it is purely the fact that the Eye Bolt bushes are worn (probably 35+ years old having never been replaced from the donor vehicle). Anyway, I now have some new Superflex bushes to fit once the snow has all gone!
                                The conversion itself was very easy and from memory the only mod required apart from sawing through the torsion bars was to lightly file the wing upright next to the top mount for the existing damper. This was to allow the new coil-over to sit correctly.
                                I used Avo coil-overs and purchased a pair of rose-jointed tie bars supplied by Steve Holder. These are much beefier than the standard tie-bars and add more strength to the front end.
                                The car has been through several MOT's since the mod was carried out with absolutely no issues regarding the integrity of the front end.
                                Perhaps I should find the time to send an article for inclusion in Pitstop for anyone interested?
                                Chris

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