Re: A couple of Q\'s
It's interesting for sure.
Remember a few years back, maybe 15 years, when IFS was "discovered" by the magazines? There were lots of articles and kits, and shops specializing in converting from that old fashioned heavy, cumbersome, uncooperative straight axle.
The arm chair racers had a ball telling everyone about it - it was a big thing for awhile. Kinda like Hula Hoops and Nikes. I was in a parking lot when a kid asked me when I was going to convert my Willies Wagon.
Then after the industry got "boring again" and there wasn't much new to yak about, some great mind thought of the word "Articulation." Off they went again. Somewhat like watching anyone talking about stocks, bonds, investments, or anything to do with money, they have to get that phrase "going forward" in every sentance.
That word became a little over used, then someone - I hope he made a fortune on the idea - came up with a "Ramp test," which really has very little to do with the real world, but it's good. The armchair guys can walk down to a supermarket parking lot and see them playing. You don't end up with a dirty scratched up vehicle while you impress the local teeny-boppers. I'd bet the idea was spawned from watching the skate boarders with their plywood ramps. (What ever happened to break dancing at malls? Love to see a lifted 4 wheeler moon walking.)
Then it got boring again. Now the latest news flash === Take off that terrible Independant Suspension and equip it with the latest, trickest invention - solid axles! Seems like someone said history repeats itself. (I still have some narrow ties, fortunately I did save the old wide ones from many years ago, I was able to wear them a second time around. I wonder when the Beetles are coming back? I still have the original Beetle 60's hair length, just not so much of it anymore, but I'm waiting - I am ahead of the times.)
IFS with coils was adapted for soccer Moms, a marketing thing. (Bet the idea came from late 1940's 2wd cars when they moved away from solif front axles for ride quality.) The ride quality is better, as the coil or torsion bar spring rate is linear, a straight line. Leaf springs have a progressive or variable rate, the curve is asymptotic.
Stock travel, like the S-10 only has about 3 inches of travel, that's why it said it doesn't have downward force. Lift a wheel slightly and it gets air under it. That's because the control arm hits the stops. But - if it doesn't have downward force, what keeps it off the ground in the first place? (Isn't that akin to falling on your chin?)
The limit here is the front diff is wide, 14-18 inches wide. That doesn't leave much length for the axles. The short axle reaches the magic 30 degrees soon with not much travel. You could move the diff down so the arc starts at 60 degrees up, then through 90 to 120 for a 60 degree travel end to end, but the grond clearance goes away.
The narrower the diff box, the longer the axle, thus the more possible travel. But still, even using store bought conventional diff boxes axles can be longer than they are with stock toilets. The A arm pivots could be placed more center and different Joints used, but there's an engine in the way.
A formula car uses IFS and IRS to keep unsprung weight down, and to provide control over the wheel to keep it in contact with the ground at all times regardless of what the other wheels are doing. That's why it's called "Independant." The low unsprung weight helps it react faster, keeping contact more of the time - after all if the wheel isn't in contact, all it is is wind resistance and a centrifugal detriment. Can you imagine doing close to 200 at the top of a turn when your left wheel bounces slightly, rocking the solid axle enough to break traction on the right one too? THAT WALL IS HARD!
A rock crawler needs low unsprung weight too. When a wheel drops into a hole or down between rocks it needs to get back up again. Heavy weight just makes it that much more difficult (ok, you try lifting even a small tire out with all four of your hands.)
Hurc posted a picture of something that will really impress the teeny boppers - at first glance it looked like it didn't have a rear wheel, it had (excuse me) "articulated" ("going forward" too) so far it was underneath somewhere. I'd bet it would only fare well in reverse on a ramp, forward it would probably turn turtle.
Yes, a wheel needs to be able to move down to look for traction, but when it's a cravasse it has to have enough sense to forget it and ---- "go forward." (Sorry)
I've never liked the brick-a-brack CV joints, never have even considered them for this.
Now, let me start a new something to consider. Conventional thinking IFS diffs are mounted solid to the frame. Who says they can't move up and down a bit as needed too? Or rock a little? That would reduce the axle angles in some situations. What if the wheels moved independant of the diff, but the diff could move some with it as required?
The diff wouldn't be sprung or unspring weight, sort of in the middle. But quick reaction time is not needed crawling over an obstacle so it doesn't matter. It won't drop into a cravasse either.
I know, it's opening a whole 'nuther bag of worms.
A few weeks ago I was watching a scorpion crawling around rocks from 1/2 to twice his size - he was about an 8 to 10 incher. He was able to twist and turn as needed (articulation), but always stayed somewhat rigid. Never once did he put a leg down between the rocks (droop). He effortlessly flitted from rock to rock without jumping. OK, I gotta say it - and he kept "going forward." The ultimate rock crawler.
Seems like someone watched a bird one time ----.
But, I could be going in the wrong direction too. After all, I threw a bottle with a message in it in the ocean last year. I still haven't heard from whoever found it. Maybe it did fall off the edge of the earth.
98% is Understanding it
Just throwing parts at it doesn't solve anything.
