Ifs 101

[patooyee]

To answer the 9" center section. I wonder if something like this would be dumb in a buggy? It's half the price of the F9, and it seems like it would be fine as long as it's well protected from rocks, but it sure would suck to spend $1200 and have it fail ​​​​​​

https://dutchmanaxles.com/irs-housing-alloy-axle-package-cv-style.html

My hunch is that it would be fine. I've been eyeballing it myself. An IFS dif should be well protected no matter what it's made out of.

 

[YotaAtieToo]

My hunch is that it would be fine. I've been eyeballing it myself. An IFS dif should be well protected no matter what it's made out of.

That's kinda what I figured. It's also within 1/4" in width of the F9 worst case scenario.

I also looked at the spider Trax stuff out of curiosity I know they make nice shit, but I'm wondering what they do to the Stubs to ask the $2600 for just the axles their ultra narrow diff is pretty badass though.

I will say, in my one ifs adventure, I learned to not ever hard mount the diff. I was breaking parts constantly, nothing remotely bling or impressive, but there were lots of guys with bigger tires and heavier rigs not having the same problem with the same parts. I think the rubber mounts absorb a lot of the shock load.

 

[YotaAtieToo]

Whether it's a swing set, rack or DE cylinder doesn't matter. What matters is the line of motion that the rod ends move through. Once you know what you want your options for making that happen and the tradeoffs become clear.

You people need to stop thinking in terms of rack vs box vs hydro.

Geometry wise it may not matter, steering feel and packaging wise, there is a huge difference between them.

 

[arse_sidewards]

Geometry wise it may not matter, steering feel and packaging wise, there is a huge difference between them.

I think it's primarily a packaging decision. Hydro, box and rack can all feel good. The choice comes down to the geometry you need (which is driven by your arms and knuckles) and what your options for achieving that are.

If you look at those guys who are running 10"-14" horizontal separation between the inboard LCA pivots there's just no way for them to fit a rack without asinine tradeoffs elsewhere hence they use a box (maybe with ram assist). You could package a hydraulic ram bit it would be more tricky.

I don't think think this is very interesting. How to connect the steering column to the knuckles all well known stuff. I think the real questions are what does the geometry of a "good" steering system look like. Once you know that you can set about achieving it. We briefly touched on that in the discussion about toe change in up-travel for cornering earlier in the thread but then dropped it after that. I have no idea what good steering geometry looks like (beyond the obvious stuff to reduce bump steer).

 

[Sterlingfire]

2 reasons jump out, steering ratio and assist level.

that box in post #220 is pretty massive, so blowing up the box or lacking assist is probably not much of an issue.

it is cheap to get a cylinder that can be very durable and is easy to adjust how much assist and what ratio you want

It has ram assist. I circled it in blue.

 

[Isdtbower]

First, I have to comment that I am building off a proprietary set of "Plans." And I have no knowledge how the geometry or steering was set. I do know it works well in simulation and built into a couple rigs that show the benefits. . There have been later generations to make the intended geometry even more effective. And I can relate to all that has gone on. Again, I stress checking your numbers with body roll. That should be your best indication that things might not go right.

I believe the rack, with attached hydro ram made packaging and strength improvements over attempts at swingers. Swingers are probably less expensive, but a lot of motion that is hard to control for strength. Both are mechanically linked to the steering wheel which is the biggest benefit to IFS.

From what I have "heard," Ackerman is established at steering link position at the knuckle. So that has to be set when designing the knuckle. Bumpsteer is set by the location of the inner link distances (Shuttle) and the location of the shuttle. front to back, up and down. In CAD that can probably be found. Before CAD it was generally moved around till the best location was found. In many asphalt cars they can be moved because of changes in ride height from track to track. Offroad. it seems like a compromise for offroad vs short course. That might be different for Pro4 though.

Time to add some pics. These are older cars remember. The cat is out of the bag and many have be changed.

 

[arse_sidewards]

Time to add some pics. These are older cars remember. The cat is out of the bag and many have be changed.

Isn't that last picture the opposite of what the tire wants for best cornering performance?

 

[JR4X]

Isn't that last picture the opposite of what the tire wants for best cornering performance?

I was standing right next to Josh England (photographer) when that picture was taken. That’s Loren Healy and the first race in the red dragon at Glen Helen, which he won. He rolled it right there figuring out how hard he could dive it into the corner. Someone already mentioned earlier how U4’s can’t corner worth a shit because they don’t have enough camber gain. As long as they go as high up the bank/berm as they can, they can haul ass. If the tire catches an edge and tucks under like that they roll. The wheel inside that tire is not in the same orientation as that tire is,

 

[arse_sidewards]

I was standing right next to Josh England (photographer) when that picture was taken. That’s Loren Healy and the first race in the red dragon at Glen Helen, which he won. He rolled it right there figuring out how hard he could dive it into the corner. Someone already how can’t corner worth a shit because they don’t have enough camber gain. As long as they go as high up the bank/berm as they can they can haul ass. If the tire catches an edge and tucks under like that they roll. The wheel inside that tire is not in the same orientation as that tire is,

Safe to conclude those of us without a berm telling us where to go should be running substantially more camber near full bump?

 

[JR4X]

Safe to conclude those of us without a berm telling us where to go should be running substantially more camber near full bump?

I’m not sure if you can achieve that with a 4 wheel drive. Plunging CV’s are one of the lines in the sand builders try not to cross because supposedly it builds heat. I don’t see how you make big camber change with out the axle shaft needing to accommodate that effect.

RZR’s have zero camber change designed in. When I assembled my long travel stuff I adjusted it to have 3° static camber front and rear to maybe help in the corners.

 

[Provience]

I was standing right next to Josh England (photographer) when that picture was taken. That’s Loren Healy and the first race in the red dragon at Glen Helen, which he won. He rolled it right there figuring out how hard he could dive it into the corner. Someone already how can’t corner worth a shit because they don’t have enough camber gain. As long as they go as high up the bank/berm as they can they can haul ass. If the tire catches an edge and tucks under like that they roll. The wheel inside that tire is not in the same orientation as that tire is,

yeah looking at all 3 of those pictures, it is fun seeing how much different of a path the tire is taking compared to the wheel.

 

[patooyee]

Time to add some pics. These are older cars remember. The cat is out of the bag and many have be changed.

I'm sorry if I'm being an idiot, but were there specific points you were trying to make with those pics? If so, can you please caption them for my dumb ass? Or were they just cool pics?

 

[JR4X]

patooyee and back to the geometry part.

I met Bill Baird, who’s featured in one of Bens pictures above. Made his own front suspension Trying to add camber change. Working off a pro-am front end as a base design that came in a car he bought from Shannon Campbell that Bill totalled.

What Bill ended up with was a front end that does have camber change. The tires are at 0° at ride height, and go negative/positive through the range of motion so as not plunge the inboard CV constantly. So at full droop the top of the tires tip out, at full bump the top of the tires tip in. Supposedly no bump steer with this range of motion. There are two cars with Bairds design of front suspension. Jeff Allsouth has Bills car and Jordan Townsend has the demo version Bill was trying to market before he retired.

I can’t picture how you don’t end up with crazy amounts of toe change through full travel If you also have a lot of camber change. Any thoughts?

 

[SLOWPOKE693]

patooyee and back to the geometry part.

I can’t picture how you don’t end up with crazy amounts of toe change through full travel If you also have a lot of camber change. Any thoughts?

Keeping all the steering and suspension pivot points in line and make everything arc in the same path seems like the easiest way...... with the wheels pointed straight ahead anyway.

 

[JR4X]

Keeping all the steering and suspension pivot points in line and make everything arc in the same path seems like the easiest way...... with the wheels pointed straight ahead anyway.

To get the camber change we’re looking for, the top of the uprights are getting closer together through the arc of compression travel. Unless the steering arm as in the same plane and sharing pivot point spacing with solely the lower a-arms the change in knuckle spacing is going to cause toe change. Every IFS setup I’ve ever looked closely at has the steering arm somewhere in the middle of the upper and lower pivot points.

 

[Weasel]

heres a calculator for IFS susp geometry but unfortunately you gotta pay to use it

https://www.racingaspirations.com/apps/suspension-geometry-calculator/

Here is one I made way back in college:
https://drive.google.com/file/d/0B0SZR_5YG-vdV0dUeTZ0YXFYUTA/view?usp=sharing

I’m not sure if you can achieve that with a 4 wheel drive. Plunging CV’s are one of the lines in the sand builders try not cross because supposedly it builds heat. I don’t see how you make big camber change with out the axle shaft needing to accommodate that effect.

Might not be able to but that pic of Loren is a good one. Could use more for that turn but what's the trade off. I don't think plunging CVs are the end of the world as we got them to work on a smaller scale but greater speeds, weights, power, distance if could be problematic.


So is anyone looking a roll moments or polar moments of inertia when building? Roll moments really seem to make a difference in how the car handles.

 

[vetteboy79]

Just for fun and comparison, a few shots of mine at varying levels of roll & articulation.

Funny thing is that last one didn't feel terrible at all from inside the car. The course came into that corner from over the berm so it was really unloaded when you had to turn, so likely a short time after that picture was taken, the suspension compressed and the camber did what it was supposed to. I had no idea it looked that squirrely from outside.

For anyone just tuning in, it does look a bit more sporty these days, those pics are all from when I first had it moving.

 

[arse_sidewards]

Just for fun and comparison, a few shots of mine at varying levels of roll & articulation.

Funny thing is that last one didn't feel terrible at all from inside the car. The course came into that corner from over the berm so it was really unloaded when you had to turn, so likely a short time after that picture was taken, the suspension compressed and the camber did what it was supposed to. I had no idea it looked that squirrely from outside.

For anyone just tuning in, it does look a bit more sporty these days, those pics are all from when I first had it moving.

You beat me to it. I was just about to say that for all its flaws at least the TTB nails the caster when it matters and ignores it when it doesn't

How terrible would it be to gain caster in compression by having the inboard A-arm separation be greater than outboard A-arm separation? You'd have negative in full droop but the tire has no traction there anyway.

I’m not sure if you can achieve that with a 4 wheel drive. Plunging CV’s are one of the lines in the sand builders try not to cross because supposedly it builds heat. I don’t see how you make big camber change with out the axle shaft needing to accommodate that effect.

RZR’s have zero camber change designed in. When I assembled my long travel stuff I adjusted it to have 3° static camber front and rear to maybe help in the corners.

I get that you'd have some plunge if the knucles aren't parallel to the A-arm pivots at all times but I feel like as long as it's not a ton that's an acceptable tradeoff. I feel like heat is so easy to fix with band-aids as needed (who was that Michigan guy who put a heat sink on his drive shaft slip joint?) that it can be one of "cross it when you get to it" type bridges.

 

[KrisKYK]

Dumb question, but why are more people not running ttb setups?

 

[rockyota83]

patooyee and back to the geometry part.

I met Bill Baird, who’s featured in one of Bens pictures above. Made his own front suspension Trying to add camber change. Working off a pro-am front end as a base design that came in a car he bought from Shannon Campbell that Bill totalled.

What Bill ended up with was a front end that does have camber change. The tires are at 0° at ride height, and go negative/positive through the range of motion so as not plunge the inboard CV constantly. So at full droop the top of the tires tip out, at full bump the top of the tires tip in. Supposedly no bump steer with this range of motion. There are two cars with Bairds design of front suspension. Jeff Allsouth has Bills car and Jordan Townsend has the demo version Bill was trying to market before he retired.

I can’t picture how you don’t end up with crazy amounts of toe change through full travel If you also have a lot of camber change. Any thoughts?

bill did some really cool stuff like making the comp arb locker for the 10" before arb came out with theirs

 

[JR4X]

You beat me to it. I was just about to say that for all its flaws at least the TTB nails the caster when it matters and ignores it when it doesn't

How terrible would it be to gain caster in compression by having the inboard A-arm separation be greater than outboard A-arm separation? You'd have negative in full droop but the tire has no traction there anyway.



I get that you'd have some plunge if the knucles aren't parallel to the A-arm pivots at all times but I feel like as long as it's not a ton that's an acceptable tradeoff. I feel like heat is so easy to fix with band-aids as needed (who was that Michigan guy who put a heat sink on his drive shaft slip joint?) that it can be one of "cross it when you get to it" type bridges.

Bill Bairds suspension was that way. The pivot points on the chassis are closer together than the pivot points on the knuckles. Equal length upper and lower a-arms. At ride height the lower a-arm goes down hill from the chassis to the knuckle, while the upper a-arm goes uphill from the chassis to the knuckle. At full droop the upper a-arm is flat and the lower is at a steep angle. At full bump the lower a-arm is flat and the upper is at a steep angle. Very minimal CV plunge, very minimal bump steer.

Whereas the Campbell cars have unequal length arms. The uppers are shorter than the lowers. So the tires are at 0° at ride height. But no matter which way the wheel goes from static (up or down) the tire tops tips inward. They have to limit their steering more because at full droop the tires are cambered in using up some of the outer CV misalignment.

Healy designed Armada front ends are more like a rzr. Equal length upper and lower a-arms, pivot points the same vertical spacing at the chassis as the knuckle. Lots of travel, minimal plunge, minimal toe change. Zero camber change.

Ive talked to Joe Thompson a bit about the IFS/IRS UFO cars but there is so much going on there I got lost. They do have both a steering box and a assist ram up front, with a swing set. The tolerances in his rear IRS setups are insanely tight. I don’t even know if Joe sleeps.

 

[rockyota83]

Dumb question, but why are more people not running ttb setups?

what about TTB and portals?

 

[Weasel]

How terrible would it be to gain caster in compression by having the inboard A-arm separation be greater than outboard A-arm separation? You'd have negative in full droop but the tire has no traction there anyway.

It's not, who car what the tire is doing if it doesn't have traction.

I get that you'd have some plunge if the knuckles aren't parallel to the A-arm pivots at all times but I feel like as long as it's not a ton that's an acceptable tradeoff. I feel like heat is so easy to fix with band-aids as needed (who was that Michigan guy who put a heat sink on his drive shaft slip joint?) that it can be one of "cross it when you get to it" type bridges.

You can minimize the amount of plunge on the CV in the same plane of the control arm pivots on both ends and the ratio of the height the same inner and outer. Sorta like bumpsteer. So where you put the diff and CV plays a role in this.

And this is the annoying things with IFS, every time you move one thing is screws 10 other things.

 

[SLOWPOKE693]

And this is the annoying things with IFS, every time you move one thing is screws 10 other things.

So true.

I think this is why you dont see many home grown IFS/IRS builds out there. One miscalculated measurement or an overlooked obstruction in where things need to be placed when building, and its right back to the drawing board on EVERYTHING. Like you said, move 1 thing and it screws up 10 others.... Computer modeling is a huge time and money saver when it comes to this stuff but not everyone has the access and/or the capability to use those tools.

 

[KrisKYK]

what about TTB and portals?

Who makes this and where can I get one? I actually may try this FML lol

 

[rockyota83]

Who makes this and where can I get one? I actually may try this FML lol

you got a link to more detailed pics of this rig?

 

[KrisKYK]

you got a link to more detailed pics of this rig?

Believe it's this car

https://www.pirate4x4.com/threads/2011-torchmate-ttb-ultra4-build-thread.924520/

 

[KrisKYK]

So true.

I think this is why you dont see many home grown IFS/IRS builds out there. One miscalculated measurement or an overlooked obstruction in where things need to be placed when building, and its right back to the drawing board on EVERYTHING. Like you said, move 1 thing and it screws up 10 others.... Computer modeling is a huge time and money saver when it comes to this stuff but not everyone has the access and/or the capability to use those tools.

building an ifs setup is akin to building your own knuckle and not too many people do that alone...

 

[Isdtbower]

Interesting comments: Best answer might be "If it was easy everyone would be doing it." It took some sophisticated THINKING with CAD and simulation. We also saw good geometry in some of the winning 2WD dez trucks. They mastered the outside wheel digging into the turn with negative camber. We could see it so the geometry was there. Then it was a project to limit or eliminate axle plunge. Plunging CV's only plunge 3/8 inch or so. Therefore a good challenge. We also saw that they were using positive (?) Ackerman so the outside wheel was turning more than the inside. I am not going to be the one to "spill the beans online." Suffice it to say that not much, if anything, is equidistant or parallel.

I am just pointing out with those pictures what you don't want to do. The side of the tire has no traction and tucking that tire under the rig really destroys the tread width so you flip REALLY quickly! And anyone with a SXS can attest to that also. SXS's apparently have to compromise for hard terrain and not true offroad I guess. But I could be wrong. I am not takng sxs video to see if there has been improvement, but I did do a little video of a current Can Am and the roll camber looked bettr than in the past.

I guess I should comment that most everyone can get good geometry for going straight. The drawing shows fairly easy articulation. And why most IFS go fast in the Dez where there is no turning. It is the turning that makes a difference in the fast rocks and short course for sure.

When we were looking closely to determine "how much," we could, almost easily, tell which tire brand was being used. I'll just leave that there. Carcus, internal balls or liners, and air pressure make a difference. Maybe more than tread pattern (To a point). A Baja tire has minimal flex, Apparently too little flex and traction for KOH and why different builds.

If you want to compare Miller's and Randy's Straight Axle cars for traction in turns I will post a SA pic in a turn and notice the tread is flat to the ground and not tucked under but the chassis really moving over that outside tire. We are not looking for low tire ware here, We are looking for traction. I think every Ultra4 should have 3* or so negative camber at "ride height." SA included. Look to see who might be thinking when they roll thru contingency or the start line. Seeing them turn down the streets will show you a lot. (without body roll) If you get a chance, look at the Newer TT"S with 4wd......

I have some great pics for Ackerman. I thought I had a file for that but can't find it. I also have shots where cars are landing with their wheels already turned for a quick upcoming turn. That either takes confidence while braking or you intend to power slide out with the rear to not get into the tire tucking problem. Those cars also have big front sway bars to minimize the body roll. Common in short course where articulation is not the game. Just wheel travel.

Shock testing is one thing. Turning at the end of that run is another.

No expert....Just what "we" are seeing.

With portals now in the mix. That hub torque and rotation with camber and caster gains will probably add another dimension into the design study.

 

[Weasel]

So true.

I think this is why you dont see many home grown IFS/IRS builds out there. One miscalculated measurement or an overlooked obstruction in where things need to be placed when building, and its right back to the drawing board on EVERYTHING. Like you said, move 1 thing and it screws up 10 others.... Computer modeling is a huge time and money saver when it comes to this stuff but not everyone has the access and/or the capability to use those tools.

It isn't exactly eaiser with CAD. You can see the results more readily but it still takes weeks/months of moving and checking.

Who makes this and where can I get one? I actually may try this FML lol

Torchmate built car for when Robby was racing KOH. Engine never servived iirc.

Those cars also have big front sway bars to minimize the body roll. Common in short course where articulation is not the game. Just wheel travel.

The front sway bar doesn't just help with body roll. It's adjusting the roll moments which has a effect on understeer/oversteer behaviors. Going to help get rid of the understeer that alot of cars have. Or plowing. We fought understeer for many years before getting to adjusting the roll moments. Couldn't run a front sway bar but it was amazing the difference in the handling once we started making changes. In the fact that when you went into a corner, you didn't have to worry about a berm cause it would go where you pointed it.