D-6

mcutler said:
Again what's your excuse for acting like an adolescent as an adult, never owning your mistakes...

I know for certain you were crouched in the corner of your shop, sobbing, in the dark, when a particularly unhappy customer drove about 5 hours to pick up his parts and unfinished clapped ass chassis...

Sent from my SM-G892A using Tapatalk
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I had sworn this thread off for my mental health...but something drew me back.
I think it was closer to 7 hours..and its a shame too, because Adam and pops are two of the best dudes I had the pleasure to meet in this sport.
I mean shirt off their back dudes. And the funny thing is they've never had a bad word to say about the person behind the experience...but you'd expect nothing less from them folks.
 
That shop was 9000 square feet. It didn't have corners. Pop Carter woke me up in a race seat I was sleeping in at 5:30 am. They grabbed their parts, and got the $3,000 back they fronted for material. Then I started tacking up 2 Bomber chassis I had in a box.
 
MetalCraftSolved said:
Using 25 degrees of inner CV angle. The pivot geometry on my new front suspension boasts 25.5 inches of wheel travel, 16.5 inches of ground clearance below the diff protection, and 35 degrees of steering angle assuming I can make the rack turn the knuckle that far.
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Now that I see this in drawing - really curious about the scrub radius on this with that giant hub.
Is that a problem? On the street it would be aweful.
 
RatLabGuy said:
Now that I see this in drawing - really curious about the scrub radius on this with that giant hub.
Is that a problem? On the street it would be aweful.
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The more I understand scrub radius, the more I feel like she's kind of an evil bitch. Most all of your rock crawlers or four-wheel drive vehicles are probably going to end up with positive scrub radius.

The "kingpin", "suspension column", whatever you want to call that imaginary line in between the top joint and the lower joint on the knuckle. You end up having to place that line close to or directly in line with the center of the CV joint or universal joint out there on the hub.

I chose to run the suspension column directly through the center of the CV joint on the hub, because I did not want to see that CV joint moving fore and aft. I have it locked in a position where it just rotates on itself.

I don't know how far I can venture down this rabbit hole, but I'll try to explain it pretty simply. What you end up dealing with when you have positive scrub radius is a toe in pressure while the drive train is digging forward, and a toe out pressure while under braking.

If the scrub radius were 0 degrees, the tire kind of wouldn't know where to go and you would end up with a squirrely front end.

All right so, that tow in pressure during forward load is going to keep the car driving straight. When you get on the brakes what's going to happen is the tire crush is probably going to experience a toe out flex a little bit and that's where you're going to feel the difference.

The original suspension I had drew up had around I'm going to say like 6 and 3/4 inch positive scrub radius.

I have not measured it but it looks like the scrub radius is going to be positive between 5 and 6 inches scrub radius.

There is a possible scenario where I can change the wheel and redo the front control arm pivot geometry to achieve a smaller number.

I'll look into it.

Screenshot_20201124-065619.png


Screenshot_20201124-065415.png
 
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Mac5005 said:
Have you ran your geometry on the IFS to determine the torque vs thrust based anti-values for accel and braking?

What about with inboard brakes?

What’s your roll center height difference front to rear?
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I engaged in mounting inboard brakes on the D-80 but I ran into a bunch of trouble I didn't want to deal with concerning all of the surrounding space of the differential. The lengths I was gonna have to go to protect the rotors was going to ruin the front end.

I don't know the torque vs thrust based anti-values for accel and braking. Sounds interesting. I wonder how to figure that out? Kind of sounds like it has to do with shock tuning, or something along the lines of anti-squat.

I don't have the rear suspension of finished. I've been trying to get all of everything else figured out first.
 
I'm confused about how CV fore/aft motion is worse/different than vertical motion (which you need a LOT of), and how you're planning on keeping CV fore/aft motion from occurring with KPI/caster/anti-whatever/unequal-arm-length as the wheel moves vertically, in pitch/roll, and in steering.

Put it this way: I don't think you can constrain fore/aft motion of the CV in the way that you think you can.
 
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Fabrik8 said:
I'm confused about how CV fore/aft motion is worse/different than vertical motion (which you need a LOT of), and how you're planning on keeping CV fore/aft motion from occurring with KPI/caster/anti-whatever/unequal-arm-length as the wheel moves vertically, in pitch/roll, and in steering.

Put it this way: I don't think you can constrain fore/aft motion of the CV in the way that you think you can.
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Alright, I'll try to clear things up. Let's assume that the only thing we're talking about is the fore and aft motion of that CV ball. Once you establish the kingpin incline and the caster angle they both together create a line. All of the other variables disappear now. The knuckle's only job now is to "orbit" that line. The wheel side of the knuckle moves fore and aft, but the absolute center of the CV ball located on that kingpin caster line does not orbit. It's the sun
 
MetalCraftSolved said:
I engaged in mounting inboard brakes on the D-80 but I ran into a bunch of trouble I didn't want to deal with concerning all of the surrounding space of the differential. The lengths I was gonna have to go to protect the rotors was going to ruin the front end.

I don't know the torque vs thrust based anti-values for accel and braking. Sounds interesting. I wonder how to figure that out? Kind of sounds like it has to do with shock tuning, or something along the lines of anti-squat.

I don't have the rear suspension of finished. I've been trying to get all of everything else figured out first.
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Figure it out with math, yet it has absolutely nothing to do with shock tuning.

It has everything to do with KPI, caster migration, a arm inclination, and all the other associated a-arm/ifs geometry.

You can all it anti-anything or pro-anything. It’s a torque and/or thrust based force and opposition force.

Not only does it matter for sandbox races and handling but also matters in the rocks and climbing obstacles.

Scrub radius also plays a critical role in the above as the moment gets longer, ie scrub radius creates a longer lever the tire and wheel has an effect on the upright.
 
MetalCraftSolved said:
Here is a torque equation. I could use a little elaboration on what I should expect to do with it. Like, after I figure out the values. What do I do with the information.

Torque - StickMan Physics
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Torque is rotational force. The tire is being turned rotationally forward. There is a force in the opposite direction of the tire rotation that is upon the component that secures the tire.

On Solid axles,that is the housing rotating or trying to rotate the opposite direction of the tire.

On IFS some of that force is at center section onto the chassis, some of it is from knuckle and a arms onto chassis.

Thrust based is from the tire’s rolling resistance. On asphalt, this is low, so very low thrust based force or anti-force. I call them anti’s bc they are opposite to the normal force.

On sand/dirt, the rolling resistance is much higher, so the thrust based force ( and anti-) is much higher.

The aero resistance upon the tire increases at the square of ground speed. So again this increases the thrust base force (and anti).

Larger scrub radius increases the length of the lever, the thrust based forces have onto the upright, and a-arms, and then chassis.

These factors all contribute to how well an IFS system works.

I’m not doing your analysis and design, mainly bc I assume you will be paid for this “project” and I won’t be getting paid.

Further, my knowledge on this is not proprietary, so just as I have learned this, you can too. (Although, I assumed you already knew all this, being that you are designing your own IFS).
 
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Mac5005 said:
Torque is rotational force. The tire is being turned rotationally forward. There is a force in the opposite direction of the tire rotation that is upon the component that secure the tire.

Solid axles that is the housing rotating or trying to rotate the opposite direction of the tire.

On IFS some of that force is at center section onto the chassis, some of it is from knuckle and a arms onto chassis.

Thrust based is from the tire’s rolling resistance. On asphalt, this is low, so very low thrust based force or anti-force. I call them anti’s bc they are opposite to the normal force.

On sand/dirt, the rolling resistance is much higher, so the thrust based force ( and anti-) is much higher.

The aero resistance upon the tire increases at the square of ground speed. So again this increases the thrust base force (and anti).

Larger scrub radius increases the length of the lever, the thrust based forces have onto the upright, and a-arms, and then chassis.

These factors all contribute to how well an IFS system works.

I’m not doing your analysis and design, mainly bc I assume you will be paid for this “project” and I won’t be getting paid.

Further, my knowledge on this is not proprietary, so just as I have learned this, you can too. (Although, I assumed you already knew all this, being that you are designing your own IFS).
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That's a lot of force. I think you're right though. Other than defining leverage, I can see it being used to find patterns. That equation makes me feel like I could work a stint at sway-away plotting line charts to graph strength patterns on different lengths of sway bar linkage.
 
Just get an armada,triton, or pro-am bulkhead and be done with the front and move on.

Those are three that have the engineering figured out and it’s proven across u4, 6100/TT spec, and the unlimiteds out there.

Build a arms and uprights and move forward.

Sure there is pride in building your own with your own design, and doing such like Jimmys, UFO, horschel, Dan trout, etc, but it takes several iterations to work the bugs out and get things 100% after leaving the design phase.

Save a ton of time, effort, headache, and cash and move forward.

Honestly, ditch the proformance diff, and get a narrowed spidertrax/tubeworks/Currie 9/10” center and move forward. There is a reason you don’t see everyone opting to use the proformance diffs and 99% running the 9/10” stuff.

Rather than reinvent the perfect package, pick some items that other much higher paid engineers and better funded race programs use and put it together.

I appreciate the thought of getting a competitive edge by thinking outside the box, but you should also draw some wisdom from those leading the current packs of racers and what is proven to work, and work well.

Honestly if you want this to be taken seriously, on here, in the real world, and in the racing community, you need to stop thinking so micro, and start thinking macro on the race program as a whole. Huge Difference in bench racing and spit balling a dream build in cad, vs putting together an actual race car and race program.
 
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Fabrik8 said:
I infer that's a rear LCA, judging by the orientation of the outboard monoball?
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I've been dropped word that you have previously or presently been involved with high profile racing suspension and design in multiple industries. Sounds like a cool gig.

They were actually all 3 rotated perpendicular to begin with, but I felt I exceeded the angle limitations of the joint using that orientation. I had to turn them. Here is the housing. Oversized, and Heavy duty.

Trophy Truck 4130 Chromoly Uniball Cups For 1-1/2" Bore Uniballs 2" Tall 3-1/2" Outside Diameter - Kartek Off-Road
 
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MetalCraftSolved said:
They were actually all 3 rotated perpendicular to begin with, but I felt I exceeded the angle limitations of the joint using that orientation. I had to turn them. Here is the housing. Oversized, and Heavy duty.

Trophy Truck 4130 Chromoly Uniball Cups For 1-1/2" Bore Uniballs 2" Tall 3-1/2" Outside Diameter - Kartek Off-Road
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The inboard orientation (that you currently have) is very normal, and very good because you're rotating the A-arms about the axis of the monoballs. The outboard joint should likely be rotated though, there is a reason that standard ball joints are oriented the way they are; the greatest angle of joint rotation is about the axis of the monoball, plus/minus the offset from KPI and/or caster. If you've got enough angle range for steering in the orientation you have now, you'll have plenty of angle range for suspension motion if you turn the joint sideways to the normal orientation. The orientation you currently have is very common for rear suspension, because almost all of the travel is vertical, and there's no steering, so it makes for simple mounting without a steer axis.
 
Fabrik8 said:
The inboard orientation (that you currently have) is very normal, and very good because you're rotating the A-arms about the axis of the monoballs. The outboard joint should likely be rotated though, there is a reason that standard ball joints are oriented the way they are; the greatest angle of joint rotation is about the axis of the monoball, plus/minus the offset from KPI and/or caster. If you've got enough angle range for steering in the orientation you have now, you'll have plenty of angle range for suspension motion if you turn the joint sideways to the normal orientation. The orientation you currently have is very common for rear suspension, because almost all of the travel is vertical, and there's no steering, so it makes for simple mounting without a steer axis.
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Ok, so I'll show you what I'm looking at. The stack height on the misalignment spacers come to 4-3/8". I'd like to ensure the bolt runs through an inch of aluminum on both sides. It looks like if I change the orientation from what it is now, I won't have enough room for a nut because the CV is in the way, and tapping is out of the question. One more thing. I think the knuckle will have a removable plate on the back side for bearing removal, so I've got to be calculated with everything I do back there. What do you think?

lower ball joint.jpg
 
MetalCraftSolved said:
What do you think?
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I think the packaging around the CV doesn't matter at all, because you're not going to have enough steer angle with the monoball in that orientation. Might be marginal at normal ride height, but then you have compound angles in bump and droop that might not get you where you want to be. I'm going to play the "there is a reason why front ball joints are oriented like that" card. ;)

Why is tapping not an option? That's pretty common to do for a steered upright like that, with a retaining tab/plate/bracket whatever to capture the bolt head to prevent it from turning and falling out. Make sure that whatever orientation you use that the monoball is mounted in double-shear, which is normally just a machined pocket to capture the monoball on both sides. I'm not sure if you need as tall of a misaligntment stack as you think you need, depending on what type of clearance you have around the monoball.
 
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