Front A frame, no panhard bar.

[o_teunico]

After Reading the thread about 4 Link suspensión my brain has been, again, thinking about a flexier front suspensión.

There are various options. In the past we have been talking about 1Link, 3Link, x-link...

I still think that replacing the panhard bar with an "A" frame, as used at rear axle, and using only one pin at the radious arms will be the easiest/cheapest way.

Has anyone seen this beeing done for real before? The only two vehicles I know that have used this system are the french Auverland A3 and the galician URO VAM-TL (this one was the opting, alog with Wolf and Santana Aníbal-PS10, for beeing the new light 4x4 for the spanish army).

[landroversforever]

On the front you'll run into problems clearing the sump with the A frame. Also bump steer would be problem unless steering is fully hydraulic.

[bill van snorkle]

Generally, an A frame used in place of a panhard rod will give bump and roll steer due to the difference in roll geometry between it and the steering draglink. It is more suited to systems with full hydraulic steering with no mechanical connection to the steering box.

A watts linkage gives a similar effect to an upper A frame, but may be easier fit around all the other mechanical components. But you would still require a longditudal upper link.

[o_teunico]

Clearance with sump will not be a problem if the A frame is located in front of the axle, as seen in the Auverland. Bump and roll steering shouldent be worser than the Auverland or URO.

Clearance with steering rod may be an issue.

Will investigate the possibilities of adding an upper 3rd link, while maintaining the original position of the radious arms (obviously with just one pin at the axle end).

[bill van snorkle]

[quote name="o_teunico" post="735774"

Will investigate the possibilities of adding an upper 3rd link, while maintaining the original position of the radious arms (obviously with just one pin at the axle end).

To give proper axle location, adequate vertical separation between the single upper and lower links is very important. To avoid having to make an excessively high pedestal mounting on the axle for the upper link, and having it clear the engine etc, you would need to make 'dropper' brackets to lower the single pin lower control arms to below the axle centreline and fit more rigid bushings if you were intending to use Radius arms with the end bushings cut off. To counter the effect of 'propshaft 'Torque Roll' the upper link should angle upwards from axle to chassis if mounted offset to right of centre, or angle down from axle to chassis if mounted to left of centre. The 'correct' angle is dependant on how far off centre the upper link needs to be to clear everything under the engine bay.

[o_teunico]

After measuring bro´s Disco, it´s clear that there is not enough space for a rear facing 3rd upper link/ A frame. Rear axle A frame is about 60 cm long. A new crossmember, flish with chassis´ front legs will be in the correct position.

As you said, clearance of the pedestal, when suspensión is compressed, with engine mount/block will be something to solve.

What do you thinkabout this design?

[landroversforever]

Surely by locating the axle from in front and behind, you will stop it articulating up and down? The axle can't travel in the two radii at once.

[Bowie69]

Surely by locating the axle from in front and behind, you will stop it articulating up and down? The axle can't travel in the two radii at once.

It will rotate the axle, but ultimately it will limit it, yes.

[bill van snorkle]

I had a visitor, so had to finish my first post before stating that 'Bang for Buck' and for easy fabrication , packaging and low maintenance, a properly made One Link wishbone is probably the way to go.

When the weather warms a little, I'll be converting WildFings 3 link + panhard over to an offset to the left One Link + Panhard as mentioned in a recent post on Dan's (Dirty Diesel) Jeep Wrangler thread. Dan has had past success using a quality adjustable A frame ball joint for the Wishbone joint, so I'll probably start with one of those to suck it and see.

I think the unboltable crossmember on the Disco, to which the ball joint would be fixed would need to be moved back or notched back so that the effective length of the wishbone was similar to the standard radius arms to maintain standardish antidive/squat geometry.

[o_teunico]

Will like to see the progress in that 1Link...

Hopefully in a few months I will have my own Disco for experimenting.

[o_teunico]

This is how I could make some test:

-Weld an A frame bracket to centre of front axle

-Fabricate and bolt a front crossmember.

-Join axle and crossmember with an A frame

-Fit Si´s x-ball.

-Test standard vs "half" A frame + panhard (that is, a three link) vs no panhard and full A frame. Front radious rear pin unbolted on both cases. Front pis is located quite more less in the same place as rear axle´s trailing arm´s bolt.

There is a karting circuit near home that I could hire for a pair of hours for propper and safe road/speed handling test.

Best of all of this design is that it is absolutely reversible.

[Bowie69]

Do you think you'll need to cut off the front ear from the radius arm to stop it from hitting the axle tube, or not?

Most importantly, are you going to do it?

[o_teunico]

Front ear will be used. Only a real life test will show if rear one needs removal or not. Just take a look at URO´s axle. That´sthe setup I want to replicate.

In a few months, once I have the real Discovery in my hands, I will like to make some tests using parts, at zero cost, taken from my bros Disco.

[De Ranged]

To me that kart track isn't the best test track, it'll be too smooth, my test track is a loop of road on the edge of town that has next to no traffic, full speed straights with bumps and wopdedos, corners with bumps on both sides, basicly really bad road (probably why its got next to no traffic lol) and the best part it has big grass verges with no drains so I have run out room if I end up off the road, I know I shouldn't use public road but I want a road test that is as close to worst case as I can and its very good at showing up handling issues

With the centred axle from this system you will have bump steer due to the x-over steering, start off on a straight with a bump on one side, if your happy you will want to test it with bumps in corners, you'll have body roll plus suspension movement

Also you'll want to test out caster change, because the front mounted a arm under suspension movement rotates the axle, the wopdedo's (straight road with an up and down roll) will travel the suspension both ways and can be very scary with some trucks....

Good luck

[o_teunico]

There are some unpaved tracks with bumps and corners, with one or two farm tractors per day beeing all the trafic.

Good luck

Thanks!

Main question for building a bump steer free 3Link with Land Rover parts is: will half an A frame be strong enough for the job?

[De Ranged]

I would say no. I'd have to cad up the side movement of the axle due to suspension bush compression, remember it isn't just the compression of the bush on the "A" arm its also the compression of the other suspension arms also at around 30degrees of rotation you are close to the top part of the rotational circle so sideways movement will be greater it wouldn't surprise me to find your looking at 15mm+ of movement to either side.... on the jap trucks I build that is around 3/4 of a steering wheel rotation! now add to this the twist of the axle on the suspension bushing being that this has only a single point of contact the axle can rotate on it, the big mounts on the radius arms have 10mm of rubber around the pin then there is the movement on the chassis bushes so lets assume 20mm of twist steering.... would only be a few degree's but would make for a vague feel to the steering

I would recommend both halves of the "A" arm

[bill van snorkle]

Best of all of this design is that it is absolutely reversible.

Nice track with lots of potential. Bring an excavator in to construct some hills and holes in the grass areas. Add some big rocks and logs, dead cars etc for a true dual use cart circuit and cross country vehicle playground.

You should run that idea past the King,at the same time you visit him to borrow the 6x4 Mercedes we want to dissect, test and evaluate the rear suspension of.

[Simon Smith]

With the lower links to the rear of the axle, and the "A" frame on the front, the castor angle will be changing constantly, and with no panhard rod it will be bump steering constantly too. In my opinion it will be positively dangerous to even attempt to drive it on the road. For good steering behaviour you want the geometry to change as little as possible as the axle moves, you are thinking of doing the exact opposite. I fitted a home made 3 link and panhard rod to my special back in the 80's, it worked perfectly in class 1 modified trials and was copied by many, it also handled fairly well when I did a bit of high speed off road testing at Peters Pit. But of course any increase in front axle articulation will dramatically increase body roll at speed.

[o_teunico]

You should run that idea past the King

He could even help the Project with part of the 8 million Eur. he recives per year, taken from our taxes.

I have been viewing some YouTube videos about bump steer...quite scary. A frame idea abandoned.

Simon, any pictures of that homemade 3Link?

What about a farm tractor 3rd link?

Main advantage: castor will be adjustable.

[o_teunico]

Have found this at a brazilian fórum. Is this the correct geometry for a 3Link?

[De Ranged]

I wouldn't use tractor links they flog out the balljoints then you'll end up with slop that rattles and bang's..... don't know your road going rules but we (NZ) have to have teflon or fiber reinforced plastic lined balljoints for suspension mount or crush tubed rubber

Yes that is a three link as for the geometry that is personal choice (how much Anti dive/Anti squat, Understeer/Oversteer, Roll center height) Go onto Pirate4x4 and search "3link calculator" it is an open source spreedsheet for calculating the suspension, where it says Anti squat on a front axle that is brake antidive

[bill van snorkle]

I would mount the lower links below the axle centreline, like they are on RRC's Disco Ones and Defenders. That way the links are immediately in compression or tension when resisting torque reaction. Mounting them at centreline as in diagram or above centreline IMO requires much greater vertical separation.

3 links don't require soft compliant bushings, so once you make dropper brackets off the radius arm axle mountings, then get hold of another 3 rear trailing arms for the links and sleeve them for strength if you wish.

I cut the original chassis end pins from the trailing arms and welded on the thicker stronger end pins from the old radius arms, because those pins are what ultimately transfer antidive/squat forces from axle to chassis.

Of course, it would be wise to maintain the standard 12 degree 'at rest' pinion angle, rather than as shown on the diagram

[o_teunico]

Will check Pirate4x4.

then get hold of another 3 rear trailing arms

Are they strong enough? I have allways Heard that, when working in compression, they tend to bend.

[bill van snorkle]

Will check Pirate4x4.

Are they strong enough? I have allways Heard that, when working in compression, they tend to bend.

No, they are not really strong enough.That is why I suggested sleeving them and welding the stronger radius arm pins on,which you would need to do anyway to use the radius arm chassis bushings.

[o_teunico]

Today I have measured Disco´s stock setup. It has been measured with just a tape. It was night, so don´t expect too much accuracy. Forgot to measure distance between radious arms and trailing arms´ mounts on chassis, but should be about 100cm (40") if the wheelbase has to be 100".

As you see, front ear of the radious arm and rear trailing arms´mounts at rear axleare at the same height. Rear A frame is not straight, but chassis and axle mounts are pararell to ground. Panhard bar is nearly flat (chassis side just 20mm higher). Panhard bar lenght is 820mm. Panhard mount at front axle is in line with raious and trailing arms´ mounts at chassis.