Check my 3 link

[EndlessMtnFab]

Put the links where they fit best and aren't rock magnets, get your upper link flat so your pinion angle and caster change stay reasonable, and go wheeling.

Probably the smartest statement in this thread. :laugh:



I'm not saying you guys are wrong at all. I'm just working things a bit differently. That is what's great about a discussion like this ... the chance to intelligently (cough cough) discuss a topic like this. :thumbup:

 

[Justpunchit]

Thanks guys for all the input and I've learned a lot reading through this and even got some entertainment out of it! haha I think what my plan will be is to give myself a few different mounting options with the upper link, and the lowers will stay right in the original spots tucked up in the belly pan, and possibly move the track bar around a bit, now with hydro steer is trac bar placement as important as a conventional steering rig? I mean I wont have to worry about bump steer so as long as it doesn't hit my ram or anything else it's good to go correct? And like Chris said, I'll build it like this and load it to the hilt with a full tank and wheel it, then go from there. Thanks again guys for the help!

 

[vetteboy]

I'm not saying you guys are wrong at all. I'm just working things a bit differently. That is what's great about a discussion like this ... the chance to intelligently (cough cough) discuss a topic like this. :thumbup:

Not saying you're wrong either - I'm as big a fan of the numbers and theory as anyone. Hell, I re-wrote the latest version of the 4-link calculator to include the 'travel' window because that's a much more 'useful' analysis than just looking at your rig stationary on level ground. (it also lets you see how quickly your roll axis increases once the links get some angle to 'em )

All the info in Milliken / Race Car Vehicle Dynamics is great to know but the fact is, a lot of it gets lost in translation when applied to the amount of travel we're working with AND the fact that our links are a lot longer to make up for it (keeping wheel recession reasonable etc). Sure we can raise the roll center and add a ton of anti-roll devices to band-aid the simple fact that we're trying to hustle a lifted brick down the highway...but if highway performance were my ultimate goal, I wouldn't be trying to build a rockcrawler. There are compromises everywhere and it's inevitable that the ones needed to yield good performance in the rocks tend to detract from the highway dynamics.

possibly move the track bar around a bit, now with hydro steer is trac bar placement as important as a conventional steering rig?

It's in your best interest to have the bar as long & flat as you can reasonably make it, to minimize the amount of lateral shift of the axle. Also as Richard said, it's pretty much impossible to get the roll center "too high" under the front of an XJ, so get the bar up as high as you can reasonably make it as well. I would also plan for a cross-brace on the frame mount - it's not going to be as big a deal without a steering box, but it's good insurance on these rigs and will certainly help to stiffen the front.

 

[Justpunchit]

It's in your best interest to have the bar as long & flat as you can reasonably make it, to minimize the amount of lateral shift of the axle. Also as Richard said, it's pretty much impossible to get the roll center "too high" under the front of an XJ, so get the bar up as high as you can reasonably make it as well. I would also plan for a cross-brace on the frame mount - it's not going to be as big a deal without a steering box, but it's good insurance on these rigs and will certainly help to stiffen the front.

a cross brace in the works as well as I'm thinking of doing an engine cage to really make the front feel as solid as possible.

 

[kastein]

Wonder how many are still with us, or even care.

Not really with you, trying to catch up, but I do care... even though I'm almost certainly never going to build something that would allow me to use this information, as an engineer/hacker I like to understand everything I possibly can on at least a basic level.

:read:

 

[jeeperjohn]

Not really with you, trying to catch up, but I do care... even though I'm almost certainly never going to build something that would allow me to use this information, as an engineer/hacker I like to understand everything I possibly can on at least a basic level.

:read:

Me too, this is all good info but in the grand scheme of things we don't need to get that deep into engineering the perfect system because the vast majority of us are not making a living racing our vehicles and therefore we can tolerate more compromises in the design of our suspensions. I would love to some day build the best possible suspension for my rig but until I hit that lotto............

 

[Goatman]

The link calculators usually generate plenty of discussion on the boards, but in real life are marginally useful. Most people are dependant on others on the internet to tell them what values are good values.......so what standard is that?

A couple of the best builders I know don't use the calculators....

Like has been said now a couple times, the lengths of our links and the travel of our suspensions makes anything other than very genreal references to suspension/chassis books irrelevant. The smartest car builder I know of when asked about link geometry and calculators replied "bah, the links don't know those numbers. Build it with clearance and make the links flat." (Jon Nelson, btw, quoted to a good friend of mine)

And, on the front, it is all even more irrelevant. But, fun to talk about.