John Parson's II MUCH Suspension Thread Hijack [Archive]

Salt Racer

03-22-2005, 07:08 AM

Yeah great article very similar to what I did with my front end. I found it a lot easier to have Coleman make me the spindle though based on their blanks than to whittle out of aluminum with 80 hours of machine time.

Also made me realize how much easier I made my life by going with a super wide track width to avoid clearance issues, although getting the lower arm setup for full turning radius is always a pain.

I didn't know Coleman, SCP, etc can build uprights to custom specs back then, and it's damn near impossible to get decent scrub radius with their standard uprights. So I chose to use Corvette hubs and design knuckles around them. It also took some negotiations with Kinesis to have them build 9" rims with 7.38" BS for some reason. They kept telling us it cannot be done, even though it's very similar to OE Corvette rim offset (and they build rims for Vettes).

I think you posted that Bruce Griggs or someone told you that modern radials like lots of KPI at CC.com. I personally think that statment came from resultant reduction of scrub radius. The fact remains that most low profile radials generate maximum lateral traction with slight negative camber (@ wheel), and steep KPI is counteractive to get that with acceptable FVSA length.

That said, if I were to do this all over again, I'd still choose to make the uprights ourselves. But I'd use C5 hubs instead of C4 hubs and a touch more SAI angle for further reduction in scrub radius, and the kunckles would be fab'ed steel pieces instead of billet aluminum. This revision will happen one of these days.

JP had a hell of time trying to get decent turning diameter. The car's ride height, and the fact that '66-'67 Chevy II's fender openings are squared off made it much more difficult. My hat's off to him for pulling it off.

Mean 69

03-24-2005, 07:03 PM

John, in the latest photos you show the UCA forward mount on a U shaped piece of tubing. How did you reinforce it? There is a good amount of tension on that mount under acceleration, and as the picture shows, there is quite a bending moment on the piece. Did you triangulate it back to the frame sections somehow? If you can join it back into the floor sheetmetal (as a secondary, not primary reinforcement), you can gain some additional rigidity in that the floors will act as a sheer plate. Don't worry about side forces, the Lion's share are longitudinal.

I'll jump on the bandwagon, for an amateur builder, you are doing a really nice job. Great, great work. I am sure you are proud of it, you should be.

Mark

Edit: I don't know how to spell.

JohnUlaszek

03-24-2005, 08:11 PM

Mean69,
Excellent observation. John and I pained over the best approach to triangulating the 3-link mounting point for quite some time. There just wasn't an elegant answer to this question as the chassis had initially been laid out for a 4-link.
The photos don't tell the whole story, I am confident it is strong enough, but you're right, picking up up the sheetmetal as a shear panel makes good sense.
Why am I qualified to say this? I am one of the two mechanical engineers John has had running FEA on suspension components for him.

parsonsj

03-24-2005, 08:38 PM

Mark,

Thanks!

It took me a little time but I finally realized you meant the rear UCA frame mount (from the pic above). The pic you see was taken as I positioned the mount point. The actual frame bracket is far more substantial.

The U bend itself is 1.75 x .125. I took another U bend and cut it in the middle of the bend, making two J-bends. The bend part of the J bend was welded to the bottom of the U-bend, notched and welded to the bottom of the crossmember. The "positioning" braces you see above are welded to the top of the crossmember. There are also triangulated braces welded from the top of the U-bend next to the bracket itself. Plus the top of the tunnel is 16g steel and is welded to the U-bend.

All in all the bracket is positioned by 6 tubes plus 16g rolled sheetmetal in tension/compression. I'm sure it will handle anything I can throw at it.

jp

parsonsj

03-26-2005, 10:08 AM

As John says, we agonized over how to mount the bracket for some time. Katz, John, and I kicked around several ideas. We started with having the bracket hooked to the frame rails with "sideways" tubes and reinforcing tubes between the crossmember and coilover crossmember.

In the end, those tubes would have been too long and subject to too much leverage, so we came up with the 6 way mount to the crossmember reinforced with "torque tube" sheetmetal.

jp

JohnUlaszek

03-27-2005, 12:05 PM

While JP's Nova may be an "amateur" build, I think the real story is the collaboration of professionals that have supported the project.

Consider, that including himself, John has had at least five engineers contribute directly using standard engineering practices for the design and fabrication of the chassis.

Katz, Suspension Engineer
Brian Schien, Machinist (Engineering Student)
Glenn Estelle, Mechanical Engineer
John Ulaszek, Mechanical Engineer
John Parsons, Electrical Engineer

Yes, John is a talented guy, but I am quite certain he takes a dump just like the rest of us (ok, this is an assumption).
What's unique in John's buildup is his tenacity and willingness to seek out experts to teach and guide him in those areas outside of his realm of expertise, often resulting in an addition to his automotive art collection.
Everyone wants to know how John found the time to buld a car like this. Maybe the right question is, how much time does the average person spend watching TV?
John is living his own reality show.

Salt Racer

03-28-2005, 01:16 PM

That is pretty sexy. What kinda rims are those? (Just kidding)

Yeah, I know you were kidding. Just had to give you a hard time.

Those are Katz Wheels - 1pc. forged, minimal drop center, and 1.63" caliper overhang clearance @ 10.5" bead width and +70mm offset. Suspension engineers' dream wheels, manufacturer/tire installer's nightmare.

The 3D model is sexy, but that's not all there's to it. Notice the number "91.2*"? That's wheel camber relative to the ground plane (ie, -1.2* wheel camber). Camber loss due to deflection should be less than 0.2* or so. This is at 3.0* roll angle and 10* steering on the outside wheel - pretty good representation of a sedan-type car going around a low-speed corner. R-compound tires will stick like mo. There's room to increase static camber further, but that might reach the point of diminishing return. We shall find out upon actual track testing.

parsonsj

03-28-2005, 05:50 PM

I really appreciate the nice comments. As Steve said, this article and the content within took many months to live (though the main textual story was written in a day or so in mid-December).

Primate, I agree there is nothing amateur about it from an engineering point of view. Katz's design and the extraordinary support I got from many people are top-notch. And it wouldn't be cheap to make another one either. Those damned uprights were very time consuming and expensive to make. Brian Schein and I were talking about it the other day, and he thought a production line with his machine jigs could cut the time down considerably. But the 7075 material in those sizes is expensive before machine work.

Remember Katz's words (which is where Johnny's title and editor's note came from): this suspension still has to prove itself on the track. A significant amount of time testing and tuning will be needed to get the right setup out of it. We are confident all the adjustment required is in the design, but finding the best overall settings will take time and effort. I can't wait for that part of the journey!

jp

preston

03-29-2005, 01:57 PM

I just came back to this thread a couple notes -

CCW built my front wheels 10.5" wide with 9" backspacing although he did say that was the limit. Backspacing and packaging is the key to scrub radius. For my track wheels I'm planning on 12" with 10" backspacing so we'll see if he can do that.

Katz I no longer agree with Bruce on that statement concerning SAI. I ended up at 12 degrees and if I did it again I would drop down to 5 like you did, even taking the hit in scrub radius (I'm only at 0.4", so I don't think it would be a big deal). I find if I dial in more than 5 deg caster it starts feeling weird, and my intuition says its the combo of sai and caster. I agree that he was probably just saying that to justify the high SAI that he had to have in his early mustang design because of the SN95 spindle and adapter packaging and the limitations of the pickup points etc. Also that SN95 spindle has a very lower pin in my eyes (too close to the lower BJ) which would also contribute to difficulty getting the scrub right.

As far as the spindles, they seem as custom as you want. I had Coleman raise the pin 1.5" fro mtheir standard design, the upper bj mount determines the SAI and they could set it up at whatever angle (and offset) you wanted, its welded on custom. They made a set of custom "stepped" steering arms for me that I didn't end up using (went with their standard bolt on arms with a bit of ackermann). Even the spindle pin was competely custom machined to match my '70 Ford intermediate spindle based Baer hubs (a mistake I would correct next time around and just use a stand stock car hub, I think the problem was finding a 5*4.5 bolt pattern at the time).

And they were still only $300 apiece, although the custom hats they made were $550 d'oh !!! Using the stock car hub would also have allowed using a bolt on rotor plate, completely eliminating the hat.
I sent them my caliper and they welded on the mounts and everything.

So I guess I'm having a hard time imagining a spindle they couldn't make fairly cheaply. The only "constraints" were I stuck to the standard Chrysler (772 ?) ball joint on the lower and the standard 4029 ?? upper 4 bolt GM ball joint, but this was fine as I used circle track parts to fab the control arms anyway so that was perfect.

BUt as I said I had two big advantages - a pretty wide track (60" center to center) and a huge engine setback that avoided any rack packaging problems. I don't know how much you paid but my custom BRT rack was $700 but those guys have also been great and they changed out the center "rack gear" for a custom length when I built a 2nd car for only lik $150, and setup the servo with a real light assist for me real cheaply as well when the initial steering was too heavy.

Without bragging too much, I think mine is the real driveway suspension considering I didn't have any engineers help me (well I'm a EE but I didn't use any engineering other than using a suspension program) and I ACTUALLY BUILT IT IN MY DRIVEWAY !! In fact I didn't even have a carport the first two years, just a tarp shelter. But then it takes a lot of work to write and photograph an article and get it published, not taking anything away from II MUCH. (I'm still trying to get Hot Rod to feature the car. Had some promises but no appointment. A few more months of track season and it won't be presentable enough for a photo shoot.)

I've had the car at 3 autoxes and 2 track days and am very happy with it. I'm no expert driver, but I have been on track for several years and raced shifter karts for 3 seasons so I have some idea where it should go. It certainly drives better than any version of the hot rodded stock '67 Mustang suspension ever did. Not only does it perform nicely on track, but it satisfies my number one design goal of being stable and easy to drive even on rutted freeways. That doesn't mean there isn't plenty of chassis tuning to be done but in the ballpark is a good place to start.

Now if I could just tone down some of the NVH.....

JohnUlaszek

03-29-2005, 02:43 PM

Preston,
The majority of the Mechanical Engineering assistance that John recieved was Finite Element, cyclic fatique, and bolted joint analysis to make sure the uprights were safe.
I felt compelled to mention the engineering effort because designing an Aluminum upright is not trivial and the failure mode is not pretty.

I am sure your uprights had similar engineering efforts applied to them, so indirectly you relied on the same kind of engineering that John relied on Pro-touring.com members for.

As a result of all of us working together we all became smarter for it.
That John was able to lead several engineers to design and fabricate a wholly new upright impressed me and enriched all of those involved. I would love to see the community collaberate more often like this, I think we will all benefit. IIMuch is a good example of what one seriously driven guy can do with a little help from his friends.

Your car is a hell of a nice piece, its a shame you couldn't have shared the buildup the way JP has done. Having said that, I don't even want to think about trying to compare the two, they both kick ass.

Salt Racer

03-29-2005, 03:10 PM

You know, it really amazes me that you pulled the whole thing under your carport. Having done engine rebuild and a 6-sp tranny conversion in parking lot when I was in college, I'm no stranger to working outside but fabbing the whole chassis is something else :worship:

60" track width is really wide for 1st gen Mustangs as low to the ground as yours. I think you made the right move with those fender flares.

I'd imagine your CCWs don't have much caliper overhang clearance? That's one of the things that I'm debating myself - whether to go with moderate offset rims (like +2.25") with good overhang clearance and use shallow hats, or the other way around like you did. I tend to stick with the former due to typical availability of rim offset. It'll be interesting to compare side effects on different designs.

With front tires as wide as yours mounted on 12* SAI, I can see why the car would feel funky with steep caster even with small scrub radius. That's part of the reasons why I stayed with 5* caster when I designed IFS around MII drop spindles (designed for 8" rims). In your case, perhaps light valving on PS may be compounding the problem?

I had no idea that Coleman can make that many alterations to their standard stuff for such reasonable price. Being able to use circle track parts is a good thing. You can get replacement parts pretty much anywhere. I definetely have been considering using BRT R&P. My soon-to-be empolyer and I are kicking around the ideas on Camaro subframe, and BRT is a strong candidate.

It still amazes me to this day how much changes suspension geometry makes not only on cornering performance but also on stability, ride quality, driveability, etc. I guess this is why I'm so anal about the stuff, and getting good feedbacks from happy customers who actually drive their cars is really nice. Unfortunately, most of the stuff I design at my current job end up on show cars with hideous 20+" wheels. It's extremely disappointing and that's why I'm leaving here.

Have you posted your lap times at PR at CC.com, or did I just miss it? Have you driven at Spokane Raceway? With limited track driving, I'm too chicken to take my car out to PR (trees and walls), but I might try Spokane before I move out of Seattle area.

Last but not least...Fu(k NVH! You got a killer ride - don't make it any heavier than necessary ;-) Seriously, it's really cool you still take the almost-racecar Mustang on street enough to care about NVH.

It's been quite sometime we had nice design/tech talk like this here. Damn it's fun!

B Schein

03-29-2005, 04:59 PM

Here are some pictures of the upright during the machining processes. I know we didn’t do it in the drive way but it was in one car garage packed full of stuff in the winter time with no heat or installation The first picture shows how I utilized the piece of material that so that I could get three up rights out of it.

Brian

Steve Chryssos

03-30-2005, 05:14 AM

its an amazing article, but the title is misleading.... theres nothing amatuer or driveway involved in this suspension.
it has been read by me a couple times, and will be read a few more.

Hey Brian,
Show the nice people a picture of your state of the art CNC upright manufacturing facilities.

preston

03-30-2005, 09:30 AM

INteresting thoughts on the caliper overhang thing. To be honest I haven't given it much thought before although I have noticed the shallow hat dish on the late model aftermarket brake kits and kind of pondered how I ended up with such a deep hat because I remember studying hub options and did not feel that my chosen hub was any thicker than other hubs - I mean they have to have some width to do their job. A couple advantages to the deeper hat is the caliper is mounted more in line with the spindle and you can use a wider caliper. But you think this would mean you are using a deeper hub. In fact I've always kind of wondered about this. I'd have to look closer at a corvette setup to understand where the difference is being picked up - maybe its just a matter of pushing the caliper deeper into the rim but it seems like it would be mounted so cantilevered out then. I do have more outboard rim clearance than I'm using, but I just told Coleman I only had 1/2" outboard of the hub mounting face for caliper clearance and that's how it came back.

That's the danger of doing this yourself, there is usually 1 or 2 parameters you don't fully understand that can bite you, but for me it worked out good.

Actually that track width is more like 62", its 60" on the back wheels which are wider of course.

I definitely like light steering which is unusual . The funky effects of too much caster that I was referring to is more a feeling like the self centering effect gets really peaky as you turn off center. I like a real strong return to center but it should be somewhat "linear progressive" in feel, and after 5 deg caster the parabola graph of steering effort gets kind of steep. That's the best way I can describe it !

Yeah kudos for BRT - they certainly treated me well and the rack has had no problems.

No lap times yet - I'm only driving the car at 7/10ths if that, still working on heel/toe etc. not to mention I'm on street tires and watching my gauges etc. I have a lot of respect for not diving in too deep with 800 hp in a home built jalopy. There were 3 vipers at Bremerton last week, and I got around all of them at one point, but its a track day so that doesn't count for much, but its better to pass than to wave by the pass.

NVH - Man I have over 150 lbs of sound proofing in this car and its still so damn loud on the freeway - mostly tire noise and what sounds like metal resonance from the rear. Looking to dampen some of the trunk panels etc. Of course I am 75% heim joints, but still. Engine is actually very quiet now. In fact people said the car seemed silent when I passed them. Damn mufflers weigh 19 lbs apiece though.

Yeah its nice to talk tech with people - I look forward to seeing you out on the track sometime. People love the car but I'm surprised how few really seem to grasp what all has been done to it. I"m waiting for someone to actually ask me questions about camber gain or ant-squat or CG or something LOL.

Salt Racer

03-30-2005, 02:02 PM

I think your car will look good with splitters, rear wing, and diffusers (seriously). Kinda like LMP car with vintage Mustang body. You'll probably want them when you unleash 800hp at PR anyway. BTW, your car is far from jalopy. It's one of my favorite early Mustangs for sure, and the fact that you use your car like it's intended makes it even better!

I seem to recall reading something about deep hats causing some unwanted rotor deflection or cracking or something. But the info is probably outdated, as I'm pretty sure it was in either Donohue's or one of Caroll Smith's books. Both design and metallurgy have improved. FWIW, TA cars are just like yours - tall hats, monster Brembos, and rims with as much + offset with not much (if at all) caliper overhang. It's probably easier to design spindles that way (bearing/pin loading, spindle rigidity, etc), easier to change tires (centerlock nut more outboard), and perhaps there's slight advantage in brake cooling with the rotor being closer to ducting. EDITOops, never mind. Rotor will be in the same location for given rim and scrub radius.

Late model OE bearings are much different. The pin is a part of hub forging, and sealed bearings are pressed into the bearing housing, which bolt on to the knuckles. I'm sure you know all that. The pin is rather short - I think it works b/c rim offset is designed such that wheel centerline falls near the centerline of bearings. IMHO, using neutral offset rims with those bearings, like many Corvette transplants on street rods, is a big no-no. But then again, I've seen a late model S10 4x4 with negative offset rims getting pounded offroad w/o bearing failure so what the hell do I know? The advantage of this design is it accepts wider range of rims, I guess, as there's no pin snout to stick out (just registering boss). Possible disadvantage is heavier rotating mass since the pin rotates (though it's damn near the centroid), and you're stuck with steel hubs as opposed to aluminum. But then again, shallow hats are lighter too.

With either design, caliper mount usually ends up close to the main body of knuckle, if things are designed right. I guess these are just different ways to accomplish the same goal for the most part.

Now if you can get rims with +3" or more offset with good overhang clearance, you'll be able to use shallow SAI and still end up at very small scrub radius...But more than likely the improvement is nil, and wheel spokes sticking too far from tire sidewall would hinder aerodynamics rather badly and designing rigid A-arms with rim clearance would be a major bitch.

I wish I had unlimited money and resources to conduct extensive R&D...All this stuff really fires up my curiosity.

Now this is a good tech talk! Where are Mean69 and Norm when we need their perspectives?

Would you let me know when you go out to track next time? Shoot me a PM over at CC.com. I definetely would like to check out your car. I'll be in WA until summer.

preston

03-30-2005, 03:14 PM

Thanks for the education - I knew the Corvette style hubs bolted on but I didn't realize how different the construction was from what I did, and hadn't even considered all the engineering ramifications. Like I said before even if you understand this stuff it seems like there's always lots to learn. I did base the car a lot on TransAm style construction so that's probably how I ended up making the right decisions. I know one thing that Sierra Caliper I have is pretty damn wide. I"m thankful for everything I've learned but if I started over I'd just build a C5 based setup, I don't see where my design really gained me much in the end other than clearance for 12" wheels.

Car does have the small splitter already and rear diffuser. For now I leave the underengine and underaxle flat panel out for cooling and noise reasons when I need the extra lap time I'll start experimenting with it. At one time I was gonna do a front diffuser but without testing/CFD it would be pointless and I needed the real estate for the IC.

Splitter comes off easily so I could easily put something much bigger on for the track and I have hard points to support it with heim links on the bumper mounts.

I"m glad you mentioned the wing thought I've been really torn between just putting a big adjustable spoiler on it or a wing. If a wing it would be a real TransAm wing or some such. Just not sure if it would work on the vintage stang. Even a big spoiler would look really race car-ey - other option is just put on the standard Maier fiberglass trunk lid with small spoiler for aesthetics. Steel trunk lid weighs 30 lbs so the fiberglass lid is sort of on my list anwyay. Of course I would like an electric ram controlled spoiler so I could have an air brake !!

I guess I know the wing is much more efficient in the long run, probably best combined with the small Maier spoiler, but just worried about how it will look. I mean, it will look cool regardless, but I want it to match the styling of the car properly.

I'll try to let you know if I'm going out - thrashing to make the SCCA this Saturday at Bremerton not sure if I'll make it.

Mean 69

03-30-2005, 04:28 PM

Hey now! I like the direction (er, hijack) that this thread is going!

John will sit along side in his lounge chair sipping a diet Sprite and telling everyone how it's so fast you could'nt reach a 100 dollar bill on the dash when he launches.

You know, this is the biggest fear that I have in planning the "next" project. Making it too pretty, and too special to actually drive the poopy out of it. There's a gentleman doing a 65 Mustang with complete SN95 Cobra underpinnings, I think he's in the show car rut, which is not where he originally wanted to go. If I were John, I'd be very careful if I drove the car. Proud, but darned worried. Gee, John, time to build a sister car to beat on!!!

Regarding the front spindle, hub, caliper, rotor deal, I am about at wit's end. With the present car and donor parts (first gen Camaro, Alcon rotors, "reasonably" priced rotor hats/rotors, stock hub, and huge positive offset wheels), I can only say that a "proper" solution needs to be engineered. A "proper" solution is going to require a very specific set of design requirements up front (it's the ole' compromise thingie), it seems to be very vehicle specific.

It feels to me that satisfying the suspension geometry comes first, making it strong enough comes second (well, parallel with requirement #1, don't mean to belittle this, it is of primary concern), then making it light comes last. Obviously a compromise is needed, but if you aren't already buying the absolute lightest wheels you can buy, then saving a pound or two of unsprung weight through spindle weight loss, etc, is probably an expensive endeavor. I'd have to look at more examples of the caliper overhang, etc, deal you guys mentioned, interesting, but down on my list of "crap" right now. I just want to make it all fit, the Alcon's are HUGE. I'll try to steal some ideas at Cal Speedway this weekend (Rolex Grand Am Race, yippee!!!! Riley's, Crawford's, Doran's, Fabtech's, I'm so happy).

I can tell you that some of the noteworthy Trans Am guys use a "modified" stock car spindle setup. Fabricated, like Preston's, ~10 degree KAI, ~9" or so spindle height. Now, the F1 guys, well, some seem to be experimenting with Carbon Fiber. Heck, if they can make a gear case out of the stuff, why not spindles?!?! Gulp! I still feel really comfortable with Timken (tapered) bearings for the front hub pack.... Sorry for the lack of tech, I'm still learning!

John, don't paint the car. Build it all up, bolt it together, go have a ton of fun with it, then strip it down and paint it.

Mark

JohnUlaszek

03-30-2005, 07:45 PM

Very informative posts Katz, Preston, and Mark. Thanks for showing me more of what I don't know :)

I will try to articulate the design process on the uprights. For any of you working in an engineering or product development environment this is nothing new, but we all bring something to the table so I will try to share some of what I know and what we learned.

JP or Brian feel free to correct me as I am fuzzy on some of the earlier work flow.

JP and Katz worked out the design requirements for the front suspension and then Katz derived the geometry. Once the suspension geometry was nailed down, Katz worked with John and Brian to model up a manufacturable upright.

At this point I became involved as John was rightfully concerned about the durability of a machined aluminum upright. At this time John was concurrently procuring a cast stainless steel upright that would be sufficiently overkill that he wouldn't have to worry about Finite Element analysis (FEA).

As I didn't have access to an FEA package at this time we turned the analysis task over to our buddy Glenn Estelle who was able to perform preliminary static analysis. Glenn's analysis revealed weak areas in the upright which called for minor design changes. Once the changes were incorporated into the model, additional conservative analysis cases were run followed up with cyclic analysis to determine the fatigue life of the billet AL part.

While forged aluminum would be ideal for this particular spindle design, the costs were well beyond the budget, this left cast stainless steel or the billet aluminum piece as options. By now John had received a pair of gorgeous cast stainless parts, but they were pretty heavy.

The results of very conservative analysis gave us confidence to run a machined Aluminum part, but with the understanding that the fatigue life would not allow unlimited mileage. The upright would be safe for tens of thousands of miles, not the hundreds of thousands you can expect from an OEM forged first gen part. Given the car would probably not see more than five thousand miles a year, this should not be a problem for years down the road.
If we had the opportunity to do it over, I think we could design a cast stainless part with the aid of FEA for a reasonable weight and essentially infinite fatigue life.

In addition to the suspension loads we were also concerned about the interface at the tapered ball joint and the bolted joint at the steering arm and hub.
Bolted joints are almost always neglected and generally people get away with murder in this area of design because they typically oversize the hell out of the fastener and are usually working with steel which is less compressive than AL. Given the dissimilar,materials we had to take a close looks at the fasteners involved and do some basic calculations to assure ourselves we had sufficient torque to properly stretch the fastener to provide adequate clamping force in the joint.

IIMuch should never see salt and very little rain, so corrosion should not be a big problem, but galvanic corrosion is still a possibility from the use of dissimilar metals, so appropriate protective coatings are still required.

Finally the improvements were worked into the solid model which was converted to a format Brian Schien could ultimately distill down to G codes to run his "state of the art" 3-axis maching center.

The amount of machine time would be drastically reduced if these uprights were made in a production environment, but then JP and Brian would not have enjoyed quality time in the garage freezing their nuts off together.

And for the record, I think paint chips rule.

B Schein

03-31-2005, 02:48 AM

You pretty much got the time line right. The one major change was in the steering arms witch original only bolted to the front hub bolt and the outer flange. They were made to bolt to both hub bolts and the flange but then caused some hub interference.

I still have the stainless pieces in my garage unmachined the way around 17 pounds if my memory is correct. the AL pieces are less then 3.

I am confident that with a real CNC mill such as a haas or fadel you could make on of these upright in 3-5 hour range. My little Bridgeport CNC is well just slow it cant take much of a chip load with out throwing the head out of whack chattering like hell or stalling.

Brian

Steve Chryssos

03-31-2005, 04:44 AM

I sure wish we could move this hijack over to the suspension topic where we can go into greater depth.

So basically we have two narrow track cars: an early Mustang and a 67 Chevy II. Neither car offers a lot of room for modern suspension. MUSTANG: One builder, Preston, worked around his packaging issues by pushing the wheels out and covering them with flares (which look totally hot by the way). Unencumbered by the limits of stock fenders, Preston was able to use Coleman spindles.
CHEVY II: II Much is restricted by the fenders. These packaging restraints led to the desing of custom uprights (among other things). If II Much were a Chevelle, you may have been able to incorporate off the shelf spindles into your design.

Is that the case? Or did you guys just whip up a pair of uprights because the mood struck you upside the head?

derekf

03-31-2005, 06:12 AM

I sure wish we could move this hijack over to the suspension topic where we can go into greater depth.

Trying something spiffy with the "Split Thread" option. If this works, the hijack will be properly moved per your request.

MoeBawlz

03-31-2005, 08:02 AM

I wanted to jump into this topic a while ago, but im not very knowledgeable about a lot of the topics being discussed here...

However Im very interested in the world of solid modeling and making parts like your uprights. Very cool stuff... I was wondering how did you do your FEA analysis? I know that programs like Unigraphics and Pro-E have FEA built into it, but I dont know just how accurate stuff like that is and I was wondering if thats what you had used or if you had just gone about it by long equations and such? I would presume that the programs would be pretty high quality analysis considering the price you pay for them but I was more or less curious as to how you guys go about this.

Also which one of you guys did the solid modeling?

parsonsj

03-31-2005, 09:22 AM

very interested in the world of solid modeling and making parts like your uprights
I have the complete Power Point output Glenn Estelle produced for the FEA on the uprights and steering arms. It is many pages long, but shows the stress "hot spots" graphically. It is very interesting and points out the problem areas that Katz addressed by adding more material to the steering arm and an additional bolt.

I'll post it up (either here or my website) when I return home from vacation this weekend.

I was torn for a long time on the material for the uprights. I wanted the security of stainless steel, but the performance of the aluminum. As Brian mentioned, the difference is over 10 lbs unsprung weight. The aluminum version needs to be considered a one-off (or two-off) part, and I think a manufacturer would used the cast stainless steel version. More analysis and engineering effort can cut the weight difference down some, I would expect.

jp

MoeBawlz

03-31-2005, 10:52 AM

Id definately like to see it...

I havnt gotten into any structural analysis yet, only surface and mold flow. So this would be interesting.

Is Glenn Estelle on this site as well?

preston

03-31-2005, 01:32 PM

Another data point - My coleman steel spindle weighs 12 lbs. They make an aluminum version (with bolt on steel pin) that weighs 7 lbs. I've thought about using that one, but the brake plate is also bolt on and I'd have to think about that a little bit - be nice to adapt it to radial mount calipers I don't think my Sierras will work with 14" rotors which is the upgrade path.

FEA is cool I don't know anything about it though.

Another downside to the "deep rotor hat" style of design is you lose room for ackermann on the steering arm, I have some but not as much as I would like but hey everyone disagrees on what proper ackermann is anyway.

One note on track width - The main reason I went wide was because lateral weight transfer is a product of CG and track width, wider is better. I'm still 4" narrower than a TransAm car or Ferrari Enzo but the flares would have looked ridiculous at that point and it barely fits on the trailer as it is. The secondary reason was long control arms for a very stable RC. Packaging really didn't have anything to do with it although it turned out later that it was a huge advantage when trying to fit all the turbo stuff in etc. I actually started out dreaming of keeping it inside a Maier fender flare envelope but the radical lowering of the car body made that impossible.

YEah sorry I didn't mean to hijack the thread but its been some really good information exchange eh ?

I as well am really jazzed about the PHR article part II. John's stuff is way more porn worthy than mine.

Probably another couple years before II Much hits the streets though ?

Mean 69

03-31-2005, 04:08 PM

Preston, I have stated it before, and I'll state it again. Looking over your design approach on the front (especially) really inspired me to gain an education into all of this stuff. It'll be fun to compare notes when I (we) do the front of my 69. What is your overall width front/rear (i.e. tire width)? I am sure I read it somewhere, but don't recall. One of the things I'd like to do on the Camaro is to keep things tucked under in the front, I thought about flaring things, but want to try to stay away from that. The basic body width is about 72" and the new wheels are 9.5" with a 7" backspacing. I'd really love to go bigger, but a 275/285-ish front tire is probably all that will fit, with a reasonable turn radius, and not going to nutso in the engine compartment. Anyway, that is the thought for now, but this is subject to change. It is going to have to happen sooner than later though, I will need to run about 1.5" of wheel spacer to make thing fit in the interim. I am not terribly happy about that, but it will be worth it in the end.

The 65 Mustang project is going to be sinister, maybe not as much as yours, but darned serious in every regard. One of those "build it around the wheels you have" projects. 305's front, 335's rear. I want to keep the weight under 2600 lbs.

12 lbs is pretty stout, I think the stock early Mustang spindles weigh about 5 lbs, maybe a bit more. Those things must be beef, which is generally the case for circle track parts anyway. Unsprung weight? Huh?

There are two great racing events closeby the next two weekends that I hope to gain some current race setup tech at. This weekend the Rolex/Grand Am serie(s) are in town, next weekend is the Long Beach GP, with T/A and of course, the Champ Cars. To say that I am excited is an understatement. Of course, what works on a stripped down race car, with huge slicks, very little roll due to huge roll resistance, low CG, wide track, doesn't necessarily work so well on the average PT type car that will see any street usage. Sometimes it is easy to lose that perspective. I'll take my licks on the street, as long as the car gets after things on the track!

Mark

parsonsj

04-03-2005, 01:22 PM

Here's a graphical representation of the FEA done by Glenn Estelle on my uprights.

Based on this analysis, we thickened the steering arm and added a bolt location to it. That removed the red spot, making the part acceptable. But as has been mentioned before, no OEM would field a car with this sort of margin. The uprights ought to be replaced somewhere in the neighborhood of 80K to 100K miles. Imagine if you took delivery of your new Z06 and the dealer told you that an expensive suspension component needed to be replaced very 5 years or 50,000 miles. Many of us would be unhappy about that.

The neat thing is that the analysis shows the parts that need to be rigorously inspected.

jp

MoeBawlz

04-03-2005, 01:57 PM

very cool stuff... Looks like a triangulated export on an STL model... not that that means anything to some of you. But its interesting to me. Hmmm maybe ill have to go and play with FEA for a little wihle this week...

Marcus SC&C

04-03-2005, 05:28 PM

That FEA is very interesting. Question,does it show the areas of relative stresses or the areas of relative strength/weakness of the component? It would seem the most likely failure point would be the thin cross sections above and below the first bolt hole with the edge of the hole acting as the most likely stress riser. I assume these holes are all radiused? At any rate,very nice work guys!!! John,that`s surely one of the trickest Chevy IIs goin. :) Marcus

MoeBawlz

04-03-2005, 05:41 PM

Im not positive, but i think you can input forces on specific features the part and then do the FEA with forces input on the upper and lower balljoints and the steering arm. at least thats how it appears with the arrows pointin inward on those three holes.

JohnUlaszek

04-03-2005, 06:08 PM

The screen shot and resulting comments are a good example of why most companies will never show FEA results. The results you see above only tell the final 1% of the problem.

FEA is a difficult tool to use by those with experience, and the results can be manipulated or misinterpreted far too easy. One only has to change the scale to make areas exceeding yield (red areas), disappear or appear.

Assumptions are made by the analyst regarding the loads, constraints, material properties, model simplification, type of analysis, mesh, and many other areas. And this is before he starts to interpret results.
An experienced analyst will do hand calculations to determine if the FEA results are in the ball park and also look at areas of high or low stress with a very critical eye to assure he/she is not tricked by artifacts or mistakes.

I have about three years of experience running Pro/Mechanica working with some top notch people. This experience has taught me what I don't know about the tools and theory, far outweigh the little I do know.

FEA is a dangerous tool in the wrong hands as it is way too easy to see what you want to see. Even an experienced Mechancial Engineer shouldn't be trusting his life to an FEA package unless he has had proper training in the use of the tool.

Steve1968LS2

04-03-2005, 06:41 PM

I no longer post much on this board, but JP told me there is one critical error in the article that needs to be corrected.

Rim width doesn't dictate how much scrub radius you should have. Scrub radius should really be less than 2.0", less than that if you have wide rim/tire combo. JP's II Much has 1.38", which will be reduced further in the future.

Ever noticed EVERY passenger vehicle manufacturered within the past few years has flat-face wheels regardless of drivetrain configuration? It is done not just to improve aerodynamic slightly to help meeting CAFE standard or to minimize torque steer on FWD and AWD. There are other important reasons for that.

PHR will fill in the rest with their next issue.

You know what.. you should write an article on scrub radius for Popular Hot Rodding.. and maybe you should work with someone on it.. someone at a suspension company.. HEY! how about Craig Morrison???

Just an idea.. ignore me if it sounds lame ;)

FYI.. the story came out great! People will enjoy it in the June Issue.. and you are now a magazine model.. ;)

parsonsj

04-03-2005, 07:09 PM

Yeah, as John says, the FEA is a dangerous weapon in inexperienced hands. It requires training and experience even for real mechanical engineers (which I'm not). This one slide was 1 of 30 different looks at the upright and steering arm. Glenn spent countless hours working on this in his spare time.

The resultant design change thickened the steering arm by 1/4" and added radiused bolt holes. You can see the difference in this picture of the actual upright/steering arm.

jp

https://static1.pt-content.com/images/pt/2005/04/IMG_5877JPG-1.jpg

MoeBawlz

04-03-2005, 09:11 PM

that looks sooooo incredibly incredible... wow...

and ive heard the same about FEA, I would NEVER trust what i do in FEA with my life. I just think it would be cool to check it out and see how it works. That would be something id leave to an engineer.

In the FEA, it looks like the steering arm is part of the upright, but obviously they are seperate parts. So there has to be a way to test assembly models like that with "clamping" forces of the bolts figured in as well. Or am i missing something?

Could i possibly get a copy of the power point? Im very interested and would like to see more of this.

Salt Racer

04-04-2005, 07:02 AM

...If II Much were a Chevelle, you may have been able to incorporate off the shelf spindles into your design.

Is that the case? Or did you guys just whip up a pair of uprights because the mood struck you upside the head?

We did it just b/c we could. No, actually, most off the shelf uprights could be made to work depending on ride height and whatnot. This wasn't the case with II Much, and OE uprights probably won't give you as good a geometry as custom uprights.

...I was torn for a long time on the material for the uprights. I wanted the security of stainless steel, but the performance of the aluminum. As Brian mentioned, the difference is over 10 lbs unsprung weight. The aluminum version needs to be considered a one-off (or two-off) part, and I think a manufacturer would used the cast stainless steel version. More analysis and engineering effort can cut the weight difference down some, I would expect...

The uprights were designed as aluminum from the beginning, so they are a little overkill (strength and weight) when you make them in steel. When you use late model bolt-on hubs as opposed to press-in or forged pins, uprights tend to become big and bulky. Fabricated uprights would be a better way to go since they can be made hollow. Uprights are mostly subjected to bending and torsional stress, so hollow cross section makes more sense.

...Another downside to the "deep rotor hat" style of design is you lose room for ackermann on the steering arm, I have some but not as much as I would like but hey everyone disagrees on what proper ackermann is anyway.

One note on track width - The main reason I went wide was because lateral weight transfer is a product of CG and track width, wider is better. I'm still 4" narrower than a TransAm car or Ferrari Enzo but the flares would have looked ridiculous at that point and it barely fits on the trailer as it is. The secondary reason was long control arms for a very stable RC. Packaging really didn't have anything to do with it although it turned out later that it was a huge advantage when trying to fit all the turbo stuff in etc. I actually started out dreaming of keeping it inside a Maier fender flare envelope but the radical lowering of the car body made that impossible....
Probably another couple years before II Much hits the streets though ?

Ackermann is defined by the relative location of tie rod center to SAI and a couple of other things, so hat depth won't change it. JP's IFS has less than 100% Ackermann (shallow SAI pushed out as close to the rotors).

You're absolutely right about lateral weight transfer. It's a difference between build styles from your car to JP's. Your Mustang is more like a racecar with mufflers and license plate, while II Much is a street car modified for track duties. Speaking of mufflers, have you checked race mufflers from Coast Fabrication? They are extremely light. With a pair of turbos, you really don't need big mufflers to quiet down the exhaust. I'm thinking about running four of them on my car, 2 per side. I think that would make the car quiet enough, and they're still lighter than a pair of 50-series Flowmasters. Of course, it's only a matter of money...

JP is trying to get it running by early fall, and at least conduct skidpad testing at VIR(?) before SEMA. It won't come close to what your car is capable of, but based on my previous work (0.94G on a tall, narrow car with very mild geometry and unshaved KDs), I'd say 1.0G will be easy with much better geometry and R-compound Pirellis.

..It'll be fun to compare notes when I (we) do the front of my 69...but it will be worth it in the end...

Yes, "we". And yes, it'll be worth it.

Steve,
I'll ignore you per your request ;-)