SOA 93 Posted November 29, 2009 Share Posted November 29, 2009 About a week ago I had a front suspension idea flash to me at about 3am, 4am had me downstairs sketching it out and by 6.30am I had a torch under a RRC seeing if it would all fit, which it would. The point of this is to get a little more flex out of LR’s front radius arm set up, how much flex? Well enough flex to make use of Gwyn’s extended shock mounts and to go some way to balance the front to rear difference in articulation off road but retain the benefits of the stock system when on-road. However it will require being bolted up for road use. Benefits include no chassis modifications, no axle modifications, uses modified standard arms, during the modification process caster correction can be dialled in, little added weight, can use OE bushes or aftermarket and the bushes may even last longer. Disadvantages, well obviously its going to cost so it’s not free, maybe weakens the arm in an are of high stress which is where I hope some of you can supply some input. I’m certain it will work but this is just the idea. Trawling the web today, it seems the idea is not new, I’m just not that clever. Superflex Radius Arms are very, very similar but not identical to what I have in mind have a look here http://www.superiorengineering.com.au/ Some basics first, bush separation, the further apart the bushes, the less flex or axle rotation there will be , just like the bigger your tyres the more link separation you need. What you need on the road is the bushes further apart so that when you stand on your brakes at 70mph in your 2.5 tonne truck on your 35” tyres the axle does not rotate, I would imagine this type of loading is far in excess of what you see off road. So in theory Land Rover designed the front radius arms and bush separation to cope with a 2 to 3 tonne truck towing maybe a 2 tonne trailer. Obviously, on road this separation does not want to be made smaller, but off road maybe we could get the bushes a little closer together and trade some of that on road stiffness for some off road flex. So the superflex arms shown in the link are similar to what I have in mind, ‘googling’ should get some info on the items. Surely just fitting one of these arms brings us back to the pivoted arms that have been discussed on this forum at great length? Same as removing a bolt from one of the bushes, suspension behaves differently braking/power? My idea has the flex on both arms, basically you put a pivot between the bushes, the position of the pivot is up for discussion ie. Nearer to the front or rear bush. The radius arm is cut in two between the front and rear bushes (The chassis bush is not discussed). So now we weld plates both sides of the front bush half of the arm and extend these plates back and up. Two holes are drilled in though the plates and the rear half of the radius arm, one forms the pivot the other is for bolting through when on the road effectively returning the arm to standard albeit weakened. That's the basics anyway. Now the part that is similar to the Superflex arms, a tubular housing for a standard bush is welded to the top of the arm behind the rear bush up out of the way of the track bar, a bush is then installed. The plates that were welded to the front section extend up then a hole is drilled in the plates so a bolt can go through the third bush. So what does this do? Well with arm allowed to pivot this bring into play the new third bush, now the separation between rear bush and the new third bush is what controls the flex in the axle, not the front and rear bush as standard. So depending on how close the rear and new third bush are to each other will determine the amount of flex available. Variables? Lots, when the arms pivot the pivot gets nearer or further away from the axle housing, this means stops could be arranged to limit movement, these could then be used to bring the front bush back into play, for instance under heavy braking. Position of the pivot can also be used to tune the characteristics of the vehicle under braking or accelerating using the afore mentioned stops. I had no hope of explaining this until I came across the Superflex arms today, hopefully with the aid of the pictures of the Superflex arms and my description you can get a picture of my idea. So Whadya fink! Be gentle please. Quote Link to comment Share on other sites More sharing options...
Ex Member Posted November 29, 2009 Share Posted November 29, 2009 Adding a third pivot into the arm will free THAT arm from all bending restraint. This will free up articulation. BUT, the other arm now will take most of the braking torque reaction. This seriously loads up that side and make a very unbalanced system under braking. It has also been shown to be unbalanced off road as well leading to strange behaviour. The lockable pinned design is better as it allows it to be put to stock when on the road. People still found it unbalanced off road. Quote Link to comment Share on other sites More sharing options...
SOA 93 Posted November 29, 2009 Author Share Posted November 29, 2009 Yes you are right for the Superflex arms as I tried to explain. However, I think you need to re-read my post as I explained my idea is for both arms. I find it very hard to explain, I think it may take a few reads to understand, please persevere. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted November 29, 2009 Share Posted November 29, 2009 I think it may take a few reads to understand, please persevere. Well, I ave rwad it several times, but then again i iz fik Post up a bag-of-fag-packet drawing for us fikos innit, sorted, M8 Nige Quote Link to comment Share on other sites More sharing options...
SOA 93 Posted November 30, 2009 Author Share Posted November 30, 2009 (edited) Well I know your not Fik and a picture tells a.......... However you'll have to make do with with an A3 pad as I don't smoke. Try to remember its only to provide a little more flex than standard, think drilled bushes or removing a bolt spread between both arms. The locking hole is not shown for clarity reasons Edited November 30, 2009 by SOA 93 Quote Link to comment Share on other sites More sharing options...
nicks90 Posted November 30, 2009 Share Posted November 30, 2009 looks good, but scary . Basic restriction of articulation on the front end is from the compression of the bushes under flex - hence why some people drill/slot their bushes to allow them to compress easier. On side squeezes the bush up and the other side down. End up with 'bush bind' and thats the end of your flex. You can run a 3 link, or a pivot joint like superior, or like yours, but all apparantly cause handling problems. I dont understand why we havent seen any manufacturers offering front radius arms that dont have a standard bush, but instead use heim joints in place of the original 4 bushes? They offer 20degree of movement, which is substantially more than you will get in compressing a bush, yet offers zero movement fore and aft and keeps all mounting points the same for identical road handling. Wuldnt this go along way to solving the problem of bush bind in the front arms? Quote Link to comment Share on other sites More sharing options...
errol209 Posted November 30, 2009 Share Posted November 30, 2009 I dont understand why we havent seen any manufacturers offering front radius arms that dont have a standard bush, but instead use heim joints in place of the original 4 bushes? They offer 20degree of movement, which is substantially more than you will get in compressing a bush, yet offers zero movement fore and aft and keeps all mounting points the same for identical road handling. Wuldnt this go along way to solving the problem of bush bind in the front arms? If this is a monging idea from Mongville, shoot me down, but couldn't you use Heims or similar all round, four at the front and two at the "fixed" ends of the radius arms? Quote Link to comment Share on other sites More sharing options...
nicks90 Posted November 30, 2009 Share Posted November 30, 2009 If this is a monging idea from Mongville, shoot me down, but couldn't you use Heims or similar all round, four at the front and two at the "fixed" ends of the radius arms? you could, but you'd have to alter the chassis mounts to accept them - and i think the above idea could mean no mods to either chassis or axle. Also, having solid metal 'bushings' on both ends would probably be a bit harsh on the road. Can you imagine having heims at both ends and on your panhard rod? Granted, it would be super precise and crisp, but the first pothole would probably hurrrrrrrt Quote Link to comment Share on other sites More sharing options...
landroversforever Posted November 30, 2009 Share Posted November 30, 2009 Heim joints wouldnt have the flex/compression ability that a rubber bush has. I think heims would make the standard set up less flexy. Quote Link to comment Share on other sites More sharing options...
errol209 Posted November 30, 2009 Share Posted November 30, 2009 you could, but you'd have to alter the chassis mounts to accept them - and i think the above idea could mean no mods to either chassis or axle. Also, having solid metal 'bushings' on both ends would probably be a bit harsh on the road. Can you imagine having heims at both ends and on your panhard rod? Granted, it would be super precise and crisp, but the first pothole would probably hurrrrrrrt morrrrrrrrrrrrrrrre Fixed it for you! (good point, but how about resilient mounts for the Heims / Roses eh? eh?) Quote Link to comment Share on other sites More sharing options...
Daan Posted November 30, 2009 Share Posted November 30, 2009 I dont understand why we havent seen any manufacturers offering front radius arms that dont have a standard bush, but instead use heim joints in place of the original 4 bushes? They offer 20degree of movement, which is substantially more than you will get in compressing a bush, yet offers zero movement fore and aft and keeps all mounting points the same for identical road handling. Wuldnt this go along way to solving the problem of bush bind in the front arms? If you would put a heim instead of the rubber bush, you would end up with absolutely no flex at all. The problem is that if your left hand radius arm moves up, and the rh moves down, it tries to compress the bushes vertically, and the heim is solid in that direction. You could put a heim on the chassis end which helps a bit, but doesnt solve the main problem, which is at the axle end. Daan Quote Link to comment Share on other sites More sharing options...
errol209 Posted November 30, 2009 Share Posted November 30, 2009 If you would put a heim instead of the rubber bush, you would end up with absolutely no flex at all. The problem is that if your left hand radius arm moves up, and the rh moves down, it tries to compress the bushes vertically, and the heim is solid in that direction. You could put a heim on the chassis end which helps a bit, but doesnt solve the main problem, which is at the axle end. Daan Yep, having thought about it that is the fatal flaw - the front of the system isn't a pin jointed frame if it has four Heims in it - it would need the axle to twist to work. Quote Link to comment Share on other sites More sharing options...
nicks90 Posted November 30, 2009 Share Posted November 30, 2009 i thought the problem on the front bushes was the bolt going through them twisting and compressing the bushes - not up and down. like this.... in which case a heim would work perfectly. I;m strugglign to visualise ho the 4 points under articulation would cause the bolts to remain horizontal in relation to the bush and just push up and down............. Quote Link to comment Share on other sites More sharing options...
LR90 Posted November 30, 2009 Share Posted November 30, 2009 Rets your fists on the keybord and put your two forefingers out in front as if they where the radius arms with the axle connecting your finger tips. Now lets articluate that axle, raise one finger tip and lower the other. The radial axis of your fingers to the axle are now no longer the same and the only way that is achiveable on the real truck without twisting the axle is the rubber joints compressing up or down to take up the radial angle between the two arms. Heim joints would not permit this. We can get more movement (and less stress on the bushes) by bringing both arms closer together (bit scarey) or as I think the OP is sugesting locating the two bushes on each arm closer together. Not so scarey but challenging to get the right distance. Slotted bushes are a good way of loosening things up, maybe just larger softer bushes are another option but would not work with original arms. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted November 30, 2009 Share Posted November 30, 2009 the easiest way of thinking how the articulation works is i think to imagine the axle laying on the floor. Standing on one radius arm, lift the other one up. the flex in the bushes is up/down. to some extent there will be a little movement in the other angles. Quote Link to comment Share on other sites More sharing options...
SOA 93 Posted November 30, 2009 Author Share Posted November 30, 2009 We can get more movement (and less stress on the bushes) by bringing both arms closer together (bit scarey) or as I think the OP is sugesting locating the two bushes on each arm closer together. Not so scarey but challenging to get the right distance. Slotted bushes are a good way of loosening things up, maybe just larger softer bushes are another option but would not work with original arms. This is all correct of course but the trade off is either longevity of the bushes or effecting the on road handling. I think the important aspects of the idea are that it can be locked out for road use and the extra flex is balanced across both arms. As someone has noted, the trick is getting all the position of the pivots and bushes right, tyre diameter, vehicle weight will both have an effect on how much it flexes. My current thinking is to have the pivot near the rear bush, clearance the cut at the top but keep it close at the bottom, that way under braking the the two halves of the radius arm will touch effectively locking it up, but will still have relatively unhindered droop. Quote Link to comment Share on other sites More sharing options...
simonr Posted November 30, 2009 Share Posted November 30, 2009 I quite like this idea! It's simple, will deliver more freedom with the pins through the third bush but return normal handling by pinning the two halves of the original arm back together. There are a number of ways of achieving the movement of the pins that do not necessarily involve lying in the mud. The main reason (as I see it) that there have only been a couple of commercial 3 link replacements for the front is that the forces are huge making the engineering expensive- and at the same time, the potential liability is worrying. Si Quote Link to comment Share on other sites More sharing options...
muddy Posted December 2, 2009 Share Posted December 2, 2009 Why has no one cut the axle case in the middle and put a bearing in it so both halves can rotate independantly, yet keep the standard radius arms to stop each half twisting under braking Will Quote Link to comment Share on other sites More sharing options...
bobtail4x4 Posted December 2, 2009 Share Posted December 2, 2009 It cant make the axles leak any worse Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 2, 2009 Share Posted December 2, 2009 One I want to try/see tried out... Imagine cutting off the axle bracket for the front radius arm bolts. then fabricate an arm that has a replacement bracket on each end. this is then attached to the front of the axle in the middle on a pivot. This means it can articulate, but under breaking/accelerating as they are both moving together it makes no difference (much!) Quote Link to comment Share on other sites More sharing options...
Soren Frimodt Posted December 2, 2009 Share Posted December 2, 2009 One I want to try/see tried out... Imagine cutting off the axle bracket for the front radius arm bolts. then fabricate an arm that has a replacement bracket on each end. this is then attached to the front of the axle in the middle on a pivot. This means it can articulate, but under breaking/accelerating as they are both moving together it makes no difference (much!) You mean like this? http://www.pirate4x4.com/forum/showthread.php?t=760819&page=4 Quote Link to comment Share on other sites More sharing options...
calle-fas Posted December 2, 2009 Share Posted December 2, 2009 It's called a X-link and has been discussed previously on the forum. Can't remember exactly what the thread was named, but I read it the other day. Can dig it out tomorrow if noone does before me. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted December 2, 2009 Share Posted December 2, 2009 Soren, that was the thread I was remembering!! didn't realise it was an X-link... heard the name but didn't know what it was! With my unexperienced mind...I'm not sure I can see any disadvantages, other than finding a suitable pivot. Quote Link to comment Share on other sites More sharing options...
Soren Frimodt Posted December 3, 2009 Share Posted December 3, 2009 Soren, that was the thread I was remembering!! didn't realise it was an X-link... heard the name but didn't know what it was! With my unexperienced mind...I'm not sure I can see any disadvantages, other than finding a suitable pivot. Thought so No I don't see any disadvantages either, (except for one bushing/joint more to fail) and I really like the setup Quote Link to comment Share on other sites More sharing options...
Pete Attryde Posted December 3, 2009 Share Posted December 3, 2009 X-link discussion in this thread :-suspension thread I think from memory implementing X-Link on a rover axle is difficult due to the position of the panhard rod and the may have been concerns about the strength of the axle case at the centre pivot. Pete Quote Link to comment Share on other sites More sharing options...
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