vehicular

iTrader: (3)

As long as the shock doesn't hit the upper arm, at worst you're only talking about a really minor change in motion ratio. Likely no change at all. I would use them.

hingstonwm

iTrader: (2)

Will mock everything up once I get my shocks back, they are currently at my shock guys place to be dynoed and freshened prior to the Runoffs.

hingstonwm

iTrader: (2)

New offset derlin bushings for front lower control arms, these will make it easier to get the camber needed with radial slicks. Still working on using the v8 roadster arms with the rod ends, but these are a viable backup plan.

vehicular

iTrader: (3)

Is that second picture set screws?

hingstonwm

iTrader: (2)

They are roll pins, with offset bushings if they are not pinned they can rotate in the arm, thus changing your settings. The bushing bores were trued/machined to make sure they were perfectly cylindrical. I am hoping that these just collect dust, But I needed a backup plan just in case I can't get the v8 roadster arms working. The friend that I bought the v8 arms from said he couldn't get enough camber out of them.

Leafy

iTrader: (1)

That arm will break with use with slicks. I already ran the FEA. No matter what wall thickness 1.5" DOM tubing (even 4130) you use for an LCA in that design its gonna fail eventually, normally near any of the tube weld joints. 1.75x.095 is the minimum if you never want to have to worry about them, ever. The older V8R arms in that style that used 1.5x0.095 1018 DOM would last about a season to a season and a half on an A6 shod auto-x car. The car that has been breaking them just got the new 1.5x.120 wall ones so we'll see how long those last.

hingstonwm

iTrader: (2)

Good to know, if you look at the previous page you will see some pics of a v8 roadster UCA and LCA, the guy running the set up in the pics is Rick Harris, former National Champion. He has had the current set of arms on the car for several years with no complaints. But a larger data base is always a better data base. I think the LCA's look very stout, I believe these are.120 wall arms. So do you think I would be better off running the stockers with the bushings?? could you post up a pic of your new .120 wall arms? I would be interested in seeing them. Thanks

Leafy

iTrader: (1)

Hard to say on these vs stockers. With true slicks the stockers are probably also in the no longer unlimited life range. I dont like the rod ends in bending either. and I REALLY dont like the use of a rod end as a lower ball joint. My loading math for my car said I needed to splurge on the NHBB -12 sphericals for the inner mounts because aurora's probably wouldnt last a full season. I think the rating on the rod ends are lower than the sphericals so YMMV there too. Maybe auto-x is more strenuous on suspension components, the e-prod guys still run those crappy EPmiata arms which would probably fail on a street tire'ed auto-x car.

vehicular

iTrader: (3)

The EPmiata rear upper arms are kind of horrifying. I can't believe people buy those things...

shlammed

iTrader: (8)

Just for *****, compare the price of a part that will be designed to last a season and sized appropriately to last that... and then design the same joint and compare the price for something that would be replaced after say half that time... but with the arm being built the same for comparison purposes.


I would bet if you designed it to have a maintenance cycle you could save both weight and money over the heavy piece.
Also, I remember reading your analysis was like 2g lateral plus 3g braking force simultaneously. how do you compare the lifetime of a part with these simulations as you might ever hit that limit (before safety factor) once ever. Genuine question if your reading this as hate... im not sure how to come up with a service life as I haven't had any experience with sizing joints like this that move.

M

Leafy

iTrader: (1)

Its all in the manufacture's catalog my man. Bearing catalogs are like the most useful manufacturer's catalogs in the world. That loading builds in its own a safety factor for impact loading that I dont want to model. Then the bearing manufacture has a nice chart for how many cycles the bearing will withstand at a certain percentage of its rated load. The -12 NHBB sphericals cost ~$6 more per bearing that the Aurora ones and gain a significant amount of of rated load, so its not really splurging when you're choosing between a $36/ea bearing and a $42/ea bearing. No real weight difference. If I wanted to have to replace them every half season I could probably save an ounce per arm and go with -10 NHBBs, the savings isnt too huge because it ends up being almost the same amount of steel, but less aluminum spacer, and it also make the aluminum spacer an expendable part at each bearing change (and a pain in the dick to make) rather than something that will last through a few sets of bearings. Now I could make the rest of the arm considerably lighter if I wanted to have them only last half a season but I think I'd be terrified of driving around on a suspension component that I intentionally designed knowing it would break.

After I did my studies on arms by copying the V8R designs and some others to set a base line I kind of came to the conclusion that no one has ever like actually FEA'ed miata control arms. FLCAs are too weak, RLCAs are too heavy (V8R RLCAs are like 2.5 times stronger than their new thick FLCAs).

hingstonwm

iTrader: (2)

Looking at my data from the races this year: 1.3 - 1.4 g lateral and about .9 g under braking. But you never throw a car around the race track as hard as you do in a autocross. At the Runoffs last year 1.2 to 1.3 g sustained around the carousel and 1.3 through the kink.

mcfandango

iTrader: (1)

Even worse than the design of the EPMiata rear upper arms is the workmanship on them. The cups are different width to attach to the knuckle. I'm lucky I have a crap load of AN washers in the right size to use as spacers.

I only bought them because, meh auto-x only. I'm not hitting the rumble strips/curbing. Had to do it again, I would not get these. The only nice thing is they fit 13s much better than the ones that use an eccentric for adjustment. Would not buy again though.

Leafy

iTrader: (1)

I kind of want to make rear upper arms. But with the stock arms I can adjust from like 2.0 to 3.2 of camber within the toe range I want so I dont NEED them, would be nice to be able to make camber adjustments without affecting toe. But then I'd need to make my rlca design that lets you adjust toe (mostly) independent of camber.

mcfandango

iTrader: (1)

Honestly, I wish I had just taken a file and slotted the factory hole. We did that to a "local" (Houston) D Prepared Miata. The alignment was all jacked up and we were just parking lot fixing at Nationals. I don't think it moved at all during the event. Weld on retainer and use an eccentric if it was a concern was the plan. Of course, DP and I still run bias ply so less camber is the goal. I'll be in MOAR camber when I move to the R75As next year.

I just want lighter & stronger front control arms. I should just get off my *** and build a jig.

Leafy

iTrader: (1)

Lighter in the back is a lot easier than lighter in the front. Lighter and stronger for the FLCA are mutually exclusive goals. I think I'm back to 4.75lb on my front lower arms that are designed for poly bushings and 5lb even for sphericals, not including the weight of the sphericals, bushings, or ball joint. The stock arms weigh 7lbs with bushings, the stock LBJ weighs 1.5lbs. I know I could take a metric **** load of weight out of the arms if I converted to a non-miata ball joint. I refuse to use a spherical or rod end as a ball joint though, so finding a press in BJ with the right taper is the hard part. I'd love to have camber adjustment on the arm, but I never play with front camber. There's a taurus one that fits, but its for a strut car so it probably has the same axial load problem as the sphericals/rod ends.

guttedmiata

Rear upper arm solution we did.

Cut the arm. Welded .50" steel "caps" on both halves then drilled and tapped for threaded rod with a hex center. Kinda ugly, but effective and practically free.

Not so much luck with the front lowers we made from 1.5x.120 that didn't make it two runs on 12" slicks. Upper fronts we made are holding fine, but of course the uppers don't see the load the lowers do.

shlammed

iTrader: (8)

Uni-Ball Weld Cups at The Chassis Shop

uni ball + ream upright and run a proper bolt through it. standard practice on a race/offroad vehicle.

vehicular

iTrader: (3)

I was going to suggest that, or a taper reamer and circle track ball joint/ press sleeve from Speedway Motors.


I don't follow your aversion to spherical bearings as lower ball joints. They're standard operating procedure on 4000lb Baja 1000 trucks. I imagine your 1900lb Miata would probably like them just fine. You mention having done analysis, is it on here someplace?

Leafy

iTrader: (1)

I think I have some pretty pictures of FEA on my build thread of the arms, but I forget. There's no need to ream the stock upright for a circle track LBJ, our cars are already 1.5in/ft just have to find one that give either a stock or improved roll center. I only found the taper last night after posting my last post in this thread.

That baja truck gets away with either running a HUGE uniball/spherical or their forces are actually way smaller than ours. For a 2000lb ish miata on slicks with aero you'd need a -16 NHBB to get the same life as the rest of the bearings. Or I guess you could get away with a -12 NHBB for the 1/2 season life cycle. But you'll almost certainly need high misalignment spacers for a spherical, and I constantly see other auto-x cars nuke 5/8" bolts in BJs or even tie rod ends so the -16 is probably the better answer. Those are only like $8x from NHBB. The aurora pwb sphericals dont have an axial load rating, just a recommended percentage of the radial load.