rear knuckle upper spherical discussion
 

since bob has convinced me not to go poly(that discussion can be found here https://www.miataturbo.net/race-prep...ushings-81552/ ), im going to start with sphericals in the rear upper. i was just going to get the ISC kit, but i dont like the idea of welding the retainer rings in. its really not a big deal, so i will if i have to, but is there a better way?

i was thinking of drilling through the knuckle perpendicular to the bore, and threading the keeper rings and then threading 2 screws through the knuckle into each ring to hold them in. something small like an M4 or 5. the same idea behind the grease zerks holding delrin bushings in place. i was even thinking of maybe threading the ID of the knucle and making collars threaded on the outside to clamp the bearing in. kind of the inverse of a shock body and its adjustable perches. i need to see if i have access to the right size tap before i could do that though, as buying a tap that size is prohibitively expensive for just this little project. yet another thought if the wall thickness of the bushing bore is enough, would be to drill and tap around the circumference and parallel to the bore, and make a cover plate, using spacers to hold the bearing in. you could ad a sealing element to the plate to keep water and junk out. its hard to describe and i cant think of an example.

got a better idea? i have a mill, lathe and welder, and 2 spare knuckle to experiment with, so just about any option is open.

my other question is what type of spherical is best for this application? standard PTFE lined? nylon lined? unobtanium lined? and since i can chose my own, would it be worth the effort to get one with a grease groove, and setup a zerk to keep it alive longer? those of you running sphericals, how long do they last you and under what conditions?

my rear upper knuckle bushings are so shot, i get a least 0.5 degree of camber change, and figured why go replacement rubber when i can be a baller.

discuss:

im bored out of my mind, so i made a highlighter cad drawing to help you guys understand what im talking about:
https://www.miataturbo.net/attachmen...ine=1417304871

and having thought about it, you would obviously only have to do this on one retainer, the other can be permanently welded in.
i think itrs pretty self explanatory but
pink is miata knucle
blue is the bearing
green is the retainers
screws are orange in the fist, yellow in the last pic (and they would be countersunk to avoid conflicts between them and the ruca)
retainer plate on the last one is orange

I would be tempted to use green loctite (bearing mount). That stuff is pretty strong but with heat can be removed.

I agree. Make a sleeve with a step on one end for the bearing to sit against and a groove for an internal snap ring on the other end. Press in sleeve with green loctite retaining compound and call it a day.

--Ferdi

i thought about retaining compound, i have 609 and 638 in the garage. i just didnt want to rely on that by itself to hold the bearing in. the static numbers look fine, im just not sure how it will hold up to repetitive shock loads. the sleeve idea is fantastic, much more surface area for the retaining compound and i can control the interference fit, snap rings make it easy. i could even pin one end of it for insurance. i was trying to think of how i could mount the upright in a 4 jaw and machine a groove into it as the snap ring idea occurred to me. using a sleeve didnt :rofl: . the only issue i can see, is with only a 1.5" bore, by the time the sleeve thickness is accounted for, your left with a smaller bearing. i need to run the numbers to see, but i think 1/8" wall would be plenty with a 0.060" ring groove, leaving me with 1.250" bearing. im sure that would be fine.

i got a chance to measure everything today. i was going to go with idea 3 (retainer plate on the end), but there is only 0.360" difference between the width of the upright and the width of the ruca. adding an 1/8" plate would reduce the amount of permissible misalignment. not sure by how much, or how much is needed, but i think that would be difficult. the thinest section of the bushing housing is also only 0.220", which doesnt leave room for a very big fastener.

638 is some good shit
https://tds.us.henkel.com/NA/UT/HNAU...ile/638-EN.pdf

4,200 psi shear strength and oil/hydrocarbon proof. i used it in the past to fix a wallowed out steering stem on my kawasaki.

i dont know why i have the 609, shear strength is lower at 2,290 psi

anyone have advice on which series of spherical to use?
http://www.qa1.net/rod-ends-and-rela...rical-bearings

I really think that the retaining compound would hold the sleeve in just fine. Though you could have the sleeve flanged on one end and use an external snap ring on the other.

If I remember correctly, 1.25" spherical bearings are not a common size. It will most likely be 1.1875", which would leave you with plenty of wall thickness for the snap rings. Plus, I think the bore is 39mm = 1.535", which gives you even more.

--Ferdi

:dunno:

https://www.miataturbo.net/attachmen...ine=1417485978

theyre actally 38mm, as this is the largest reading i get, its measures closer to 1.496 in other positions. ill look into sizes and hopefully order some bearings tonight. thanks for the idea ferdi. you are the winner.

Ah, I am sure your measurement is right. I had an ES bushing sitting on the table and it measured a tad over 39mm.

What are your plans for the other bushings? My plan was to use delrin or nyloil for all the others. I was being lazy and initially planned to use the ES bushing in the rear upper, but I do have access to a machine shop and could easily make sphericals happen.

--Ferdi

delrin, AF blend, or nyloil. i need to tackle this and some offset front uppers asap so i can get a decent alignment. i just got a new set of rivals and dont want to camber wear them like i did to my last set of tires. after that, ill think about the rest, but more than likely just delrin as AF bend is expensive and i havnt seen any feedback on nyloil. the lower control arms will probably stay rubber as i dont want to deal with binding, unless i get out of hand and try to stuff bearings in those too.

the ES bushings are always a little big so they press fit a little.

the installed diameter of the snap ring is what will determine everything. a 1-5/16" snap ring has an installed diameter of 1.396", so that leaves exactly 0.050" wall at the snap ring, which is fine if i make it a slight press fit.

i decided on that size based on this:
Internal Retaining Rings | Arcon Ring

they are 0.050" thick and i happen to have a 0.059" internal cutter.

1.3125" bearing. SS, PTFE lined, its supposed to be their best wearing bearing that isnt nylon based, we will see.
http://www.summitracing.com/parts/hal-sib10t/overview/

another thought is to make the sleeves 2 separate pieces, no snap ring groove machined at all. now make the snap ring 1.5" installed into the bore itself, probably using a 1-7/16", and using a 1.375" bearing. then press the 2nd sleeve in against the snap ring (maybe 0.002" short so its not stuck tight and impossible to remove) so the 2 separate pieces comprise the snap ring groove.

the 1-5/16" snap ring has a thrust load rating of 9,300lbs, which ironically enough is less than what i calculated to be 9,732lbs if i were to use just 638 on a 1.3125"x0.562" bearing race, let a lone a 1.5"x whatever"

Nice find on that bearing, if I decide to go this route, I'll most likely get the same ones.

--Ferdi

decent options in 1.375 for idea #2 as well
http://www.summitracing.com/search/p...SortOrder=Desc

Skip that bearing, unless you want to have to replace them all the time. Wait I take that back, looks like thats just QA1 re-selling the Auora SIB series bearing. I like the AIB because of the anti-corrosion stuff on the inside, couple dollars more money.

Here's what you do. You make a sleeve that is the width of the knuckle, one end is 1.125" diameter and set so the bearing is in the middle, then the width of the bearing is 1.3125, snap ring groove, and then 1.3125 to the end. Press that into the knuckle and drill some holes in the knuckle to spot weld the press fit sleeve to the knuckle. You'll also need to make aluminum spacers which fit inside of the 0.75" diameter of the spherical and have the ID of the control arm bolt (10mm?) and also have a taper cut on them.

Use Aurora AIB-10T.

Another option thats a billion times easier and cheaper but makes adjusting toe a HUGE pain in the dick. Put a solid aluminum bushing in there with a 10mm ID bore, and make 1 tie rods to replace the upper control arm with. This gives up camber adjustment at the top of the upright but also requires you to adjust the lengths of the arms when you change toe at the bottom of the car, and it should only fit with 60mmID springs at a max. You'll want to use AM-10T rod ends for this, and aluminum hex rod. If you really want to go this way I'll run the numbers and make sure you dont have to go to the AM-12T just to get the larger hex rods.

the AIBs are about half the price, and the sales literature indicates the SIBs to be "top of the line"...? it would make sense that a chromoly race would wear better though.

im not sure i want to go through all the hassle of tie rod control arms, but feel free to run the numbers for science.

Wonder if there is enough meat in the knuckle to just cut the top hoop off the knuckle and drill and tap for a threaded rod end screwed into whats left of the knuckle to replace the upper pivot point.

Threads in bending bob, dont do that. The press fit and tack with a spherical isnt all that difficult. I guess you could just press fit with green locktite, but you're really relying on mazda having held a decent tolerance on something they only ever intended a piece of rubber to press into.

its a machined hole, its within 0.001, not including the wear from 23 years on the road and years of autocross.

also:
"LOCTITE®
638™ is designed for the bonding of cylindrical
fitting parts, particularly where bond gaps can approach 0.25
mm "

agreed about the threads in bending mode, and it necks down substantially after the "hoop", so i dont think there is enough meat anyway.

I know that green loctite can do that. Do you want to try it? I realize the bonding strength, The wheel bearings on my FSAE car were held into the uprights with just a press fit and green loctite, no snap ring because lazy. It probably would be fine, and really even if the press fit + loctite failed its fully encapsulated in the control arm so you're not going to crash.

that was my thinking. i dont want to weld it only because it will be hard to reverse, especially if i plug weld it.

so i want to order the bearings asap. i haz snap rings and steel and lathe.

AIB it is? im not concerned with cost,(within reason) i want what will last.

Yeah wait, I got the different aurora levels mixed up. AIB and SIB are more or less the same but AIB has a alloy steel inner race and SIB has stainless. They're rated for the same so the weaker stainless doesnt have a down side besides price. Its up to you then. Just dont forget to get the one with T added to the end to get teflon liners.Dont forget to snag some 1" do 6061 round stock so you can make he spacers that slip over the bolt and inside the spherical.