Help required.......

[Timmy511]

Im currently doing my final year on a part time engineering degree and my final year project is: re designing the front suspension of my 90. im aprentice trained engineer, and have been working toward my degree for 7 years, hopefully once the project is finished ill build it at home.

if anyone has built a home made front suspension kit (like plastic badgers disco) and they dont mind me using it as an example in my research please could you post up a few pictures and a very brief write up as to how much you think it has improved you vehicles abilities.

my design im hoping will be very different to most pople build and will be something like this: (brief scketch, Cad modle, FE analysis and mechansim analysis to follow as the project progresses)

thanks in advance, Tim.

[dangerous doug]

would you like set ups like that or gut alternative LR set ups people have made?

PM sent

[will_warne]

Tim, am I right in thinking 2 of what you've drawn would replace the hockey sticks? The only way that would give any more articulartion is if you removed one of the lower links. This sort of missing link system will give simerlar performance to a hinged radius arm - it's been done to death if you do a search. Basically, it'll look good on a twist off ramp but doesn't work so well as it's not balanced from side to side and the side with the missing link has poor control over axle wrap.

Basically the other main options out there are:

1) 3-link - loads of examples both off the shelf and home made. Most have a single lower link but a single upper link is a better design (single link is in tension).

2) 4-link - less popular as its not so easy to bolt on. A few truck are appearing with this setup. The best I've seen is the one of Filtyboy's buggy.

For both of these there's a great calculator on pirate4x4 which makes all the maths easy.

3) 1-link - A few people on here have done this with good results. Saley was the first IIRC.

4) Cross link - The idea came from Dobbin Engineering and no one's done this on a LR axle to the best of my knowlege.

[FridgeFreezer]

Chances are I'm missing something here but if the lower link in your picture is bolted to the axle at one end and to the top link at the other, it may just as well be welded together as a ladder bar. By putting joints in all you're doing is giving the potential for play in the bushes which would lead to wrap/tramp.

[Timmy511]

Chances are I'm missing something here but if the lower link in your picture is bolted to the axle at one end and to the top link at the other, it may just as well be welded together as a ladder bar. By putting joints in all you're doing is giving the potential for play in the bushes which would lead to wrap/tramp.

the joint would be johnny joint preferably,

but having read this maybe my brain cant compute how it all moves, the idea was to allow the bottom link to move and run out of line with the top link, and then allow the axle to move more.

once ive got the mechanisms software sorted ill have a play with it.

either im not understanding how the suspension works or im not explaining my idea properly.

i know what some one has said with a three link type of thing with a link thats similar, ive seen one and it was totally gash!

[doublej]

you basically have an upside down radius arm set up. same as RE long arm kit for jeeps.

i think they just use it on the front and a true 4link with panhard bar in the rear

[Timmy511]

you basically have an upside down radius arm set up. same as RE long arm kit for jeeps.

i think they just use it on the front and a true 4link with panhard bar in the rear

and as they say round here, thats the badger, and the jobs a carrot as it obviously works.

is there any more pics from that build youve shown?

cheers, Tim.

[Guest noggy]

just search for a long arm set ups, go to Pirate4x4.com theres LOADs on it.

[tiddler]

Search the Jeep forums especially jk-forum for info on the RE front links, and you will find they actually don't work.

There is even a video clip around of the guy from RE explaining that the system is designed to LIMIT axle travel so that it protects other drive-line components!

I know two people who use it and they regularly shear mounting bolts because the radius arms cannot cope with the amount of drop their shocks will allow.(and that isn't much by LR standards!)

It's a pretty poor design and you would be better looking elsewhere IMHO.

Giles

[dollythelw]

how about looking at ways to optimise the stock setup?

analysis of causes of bind, methods of improving articulation and knock on effects to road holding, roll centres changes etc?

that'll keep you busy and you may end up with a marketable product at the end of it

[david1701]

I'm quite intruiged by this as a first year engineering student, though i am doing electronics (but my first year is common across electronics civil and mechanical)

why are you using cad not solidworks, as what use of it i have it seems to be very astute at multipart drawings

[gsr341]

im no engineering student/graduate

but that arm looks as if its going to turn out quite large (jonney joints are quite chunkey) and the addition of a joint Under the original mounts just looks as if its either going to rub on the front tyre on lock or get stuck and mashed up by the ground when off roading

[Timmy511]

I'm quite intruiged by this as a first year engineering student, though i am doing electronics (but my first year is common across electronics civil and mechanical)

why are you using cad not solidworks, as what use of it i have it seems to be very astute at multipart drawings

david that was drawn in solidworks, using the sketch tool on the first plane i selected. ill draw the 3d model on solidworks, then export it or redraw it for to use in mechanica for full FE analysis, and then use something similar to algor design check to see where any stress concentrations are in the design by applying different forces from different angles etc.

[Timmy511]

how about looking at ways to optimise the stock setup?

analysis of causes of bind, methods of improving articulation and knock on effects to road holding, roll centres changes etc?

that'll keep you busy and you may end up with a marketable product at the end of it

id like to mod the existing radius arm but my idea for that was somewhat unimaginative, this is a little more involved.

[Timmy511]

This is the design im playing with, its nearly finished bar from drawing a 2" johnny joint and some nuts and bolts and some crush tubes.

now then its time to test, modify(re-draw) and produce detailed drawing! joy!

[FridgeFreezer]

Can I ask how that differs functionally from the standard hockey sticks? The layout is slightly different but the effect is the same, the addition of joints where it meets the axle is a bit confusing too, surely that would just allow the thing to move about rather than holding everything straight & true as it should?

[custom-conversions]

You might be onto something, its difficult to see without moving it througth its full range of travel though.

It might take a while finding the optimum posisions for the links. Maybe angle the lower links towards the centre,.

Its still going to need a panhard rod to keep the axle positioned latterally by the looks of it, the radius arm bushes flex & the axle would move side to side.

It'll be interesting to see the outcome.

[simonr]

I hate to pour cold water on what has obviously involved a lot of effort - but what you have drawn will have less articulation than standard hockey sticks.

As the assembly articulates, it is in effect trying to twist the axle. It is obviously reluctant to twist so in your case as with hockey sticks, it is only the bushes squashing which allows the articulation. Johnny joints have less elastomer than standard hockey stick bushes so there is less to squash and hence less movement off axis.

I would try building a simple model out of coathanger wire before you embark on a build.

Si

[smo]

Why dont you use the motion simulation part of Solidworks to analyse the motion and limitations of the new setup, also you could use cosmos for the FEA - either way you dont need to remodel it to run the FEA.

[Timmy511]

Why dont you use the motion simulation part of Solidworks to analyse the motion and limitations of the new setup, also you could use cosmos for the FEA - either way you dont need to remodel it to run the FEA.

that is the plan.

[Timmy511]

I hate to pour cold water on what has obviously involved a lot of effort - but what you have drawn will have less articulation than standard hockey sticks.

As the assembly articulates, it is in effect trying to twist the axle. It is obviously reluctant to twist so in your case as with hockey sticks, it is only the bushes squashing which allows the articulation. Johnny joints have less elastomer than standard hockey stick bushes so there is less to squash and hence less movement off axis.

I would try building a simple model out of coathanger wire before you embark on a build.

Si

i appricate what your saying, this will be a problem, only analysis and a model will prove it, but even so a failure is not a bad thing, itll make for a good discussion about is nd possible way to overcome it as part of my project. the twist back and forth souldnt be as great as the anglular displacemnt of the axle imo (ihavnt worked it all out but i think id best do pretty quick! lol!).

as has been said above, the positions of the link may be critical, only time will tell.

[Timmy511]

Can I ask how that differs functionally from the standard hockey sticks? The layout is slightly different but the effect is the same, the addition of joints where it meets the axle is a bit confusing too, surely that would just allow the thing to move about rather than holding everything straight & true as it should?

Jez, if you were to look at any vehicle cross axled, the the hockey sticks (radius arms) are having to twist in the chassis bushes to match the angle of the axle, the axle at the dropping wheel will move backward and the rising wheel will move forwards, hence those massive rubber bushes in the end of the arms to allow for that movement.

that creates alot of binding force and also instead of the spring pushing the wheel into the ground the energy compressed in the bush is trying to push the wheel back up.

The idea of my linkage is the top link can twist more inline with the chassis bush as is raised about 2 inched from the standard mounting position (like a cranked trailing arm), and then the bottom link can swing sideways as the axle becomes more cross axled, the johnny joints allow for the same movement as the standard rubber bush but allow it all to move with alot less binding effect.

yes the pan hard rod will still be there but thats something to be mentioned for 'future developments'.

really this is just an idea which is being engineered to suit a current problem, 'doing a uni project that doesnt involve work work'!

but all comments and ideas are very much welcome as other people see things in different ways and highlight problems.

[smo]

really this is just an idea which is being engineered to suit a current problem, 'doing a uni project that doesnt involve work work'!

I'm sorry if i got this wrong but you are trying to engineer a project that involves as little work as possible, and ask on a forum to gather our knowledge and experience and ideas just to avoid doing anything yourself?

[simonr]

Jez, if you were to look at any vehicle cross axled, the the hockey sticks (radius arms) are having to twist in the chassis bushes to match the angle of the axle, the axle at the dropping wheel will move backward and the rising wheel will move forwards, hence those massive rubber bushes in the end of the arms to allow for that movement.

that creates alot of binding force and also instead of the spring pushing the wheel into the ground the energy compressed in the bush is trying to push the wheel back up.

I'm afraid this is a classic mistake - and does not seem to be obvious to most people. The chassis end bushes on the radius arms are not the main restriction to articulation. If you replaced them bot with ball joints, the axle would be able to rise and droop more easily but the ease of articulation will hardly be affected.

I think you are missing the fact that as the axle articulates, both hockey sticks and your setup are both trying to twist the axle. What you have drawn is just a more complicated version of a hockey stick with different mounting points on the axle.

I worry that if whoever marks your project has a decent understanding of mechanics, they may not be as impressed with your efforts as they could be?

Si

[filthy boy]

It also looks to add in a lot of new failure points and additional stresses and loads from the elevated mounting of the upper part of the arm.

Now if you could work out how to get upper links on a 4 link past the oil pump on a Td5 that would be cool!

Tim