Adjustable Upper Control Arm for '88 Front Suspension

[The Dark Side of Will]

You can buy a set from WCF right now, with Delrin bushings instead of rod ends.
https://westcoastfiero.com/products/88- ... per-a-arms

[draven]

You can buy a set from WCF right now, with Delrin bushings instead of rod ends.
https://westcoastfiero.com/products/88- ... per-a-arms

Yeah, but the 450$ price is a bit much to swallow.... all the parts are generic SPC except for the plate, correct?

[The Dark Side of Will]

The plate and the pivot shaft. Add it all up... The parts aren't cheap, ESPECIALLY from SPC.

[The Dark Side of Will]

Edit: Just ordered the rod ends. The BOM comes to $360, WITHOUT the pivot block and ball joint plate, also excluding shipping from four vendors.

[The Dark Side of Will]

You can buy a set from WCF right now, with Delrin bushings instead of rod ends.
https://westcoastfiero.com/products/88- ... per-a-arms

Yeah, but the 450$ price is a bit much to swallow.... all the parts are generic SPC except for the plate, correct?

I think Steven said he had to design the plate, the welded "pivot stud" and sleeves to adapt the delrin bushings to the factory style inner pivot shaft.

[The Dark Side of Will]

The pivot blocks are finished. They weren't cheap. I'll have to figure out if the prototype guy can make a few for a significantly lower price or if I'd be better off going to a place like eMachineShop to have them done.

I don't know if I'll be able to do anything with them this weekend, as I'm flying out to Pendleton early (early! ) Sunday.

[The Dark Side of Will]

Kind of back-burnered the '88 control arms since I bought a 2005 diesel Benz as a daily, was able to give the Storm Trooper a rest AND I've been focusing on pulling The Mule's engine, and tearing that down to finally get it rebuilt and on the road long term.

I had to go through a couple of design iterations on the lugs to lock the pivot blocks into the crossmember, but I have those set now. I had to have a couple of fit check tools cut out of a piece of aluminum block so as not to have to modify and/or re-make the actual steel blocks. The pivot blocks will be powder coated this week. I'll be able to get the control arms installed this weekend and aligned Monday.

I took some photos of them naked, but apparently never posted... will do so this evening.

[The Dark Side of Will]

[Shaun41178(2)]

Those look good.

How many project and or cars do you have now?

Northstar fiero.
White formula
Ferrari
Benz diesal
Eagle wagon
White rapist van

Missing anything?

[The Dark Side of Will]

And an E30 and 20 more in my head... with no workshop of my own.

[draven]

Any interest in making another set of ball joint plates and blocks?

[The Dark Side of Will]

I intend to do so once I get a few miles on these.

The blocks weren't cheap on a prototype basis, though. >$300, IIRC

Also, I may want to change up the adjuster tubes on the forward link for the next longer size.

[The Dark Side of Will]

Oooops.... It turns out my dumb ass was designing these things in the wrong hand

[The Dark Side of Will]

After some development... I could see that my legs would be closer together than Steven's owing to the differences in our inner pivot mechanisms. I just couldn't see how little clearance there is around the spring bell on the crossmember.

So I had to whip up some spacers to get things into place, and I still need to update the ball joint plate a bit to have the two legs wide enough to clear the spring bell. Also need to figure out if I want to angle both ends of the pivot block. I have to have it machined to get the lugs cut... I need to talk to the prototype guy about whether it's the weight relief pocket or the angled end that makes them expensive... Maybe I can reduce the machining costs enough to cover a little welding.

[ericjon262]

that looks awesome so far!

[The Dark Side of Will]

As demonstrated by my spacer for the forward rod end, I need to lengthen the front end of the pivot blocks considerably. That would then put that end of the block at an angle and make them more expensive to machine. I was thinking about how to approach this. Making my own 3/4-10 tapping blocks is not a good use of time or engineering resources.

3/4-10 square nuts are available, but only in medium strength (Grade 5) at best, and even at that, they are thinner than 3/4", so still not great from the strength perspective. I was brainstorming at McMaster--which 2nd only to sitting on the can is where I get my most useful ideas--and realized that T-slot nuts for machine tool fixturing were probably pretty good steel AND being squar-ish would be pretty easy to weld to a laser cut plate to make fabricated pivot blocks. BAM! I emailed McMaster to see if they know what strength steel the T-slot nuts are made from. The studs in their kits are 125,000 psi, which is Grade 8 strength.

ETA: Looks like 94750A598 is pretty close to what the doctor ordered. They probably also have some shelf spacers I can buy so that I only have to have top & bottom plates cut out of 5/16" steel.

ETA2: McMaster says the T-Slot nuts are Grade 2 1018 steel... so not very strong, but easily weldable. They are thicker than the diameter of the bolt, so they should still be fine. I'm using stainless bolts anyway, so it's not like a need to pull them very hard. Even low strength 3/4" bolts go to >150 ftlbs.

ETA3: My prototype parts pictured above are 12L14, which isn't super strong anyway, so 1018 shouldn't be a problem.

[The Dark Side of Will]

I ended up just using 1018 1" square bar to have my own bolt blocks made. I'm dropping the lugs idea, as that added a lot of machining complexity unecessarily. I'll just push the bolts against the inboard end of the slots and tighten them down. That will (theoretically) provide some cushion if the car gets curbed hard... the joint will be able to slip instead of being rigid and making something bend.

My resulting welded assembly looks a LOT like some of the pre-built control arms available from SPC... that's because there are only so many ways to skin this particular cat. I tried an intermediate plate (below) that looks a lot like the one Steven designed for his control arms--again, only so many ways to skin this particular cat--but I'm not wild about the way that offsets the ball joint center from the line of action of the adjustable link. I spaced the rear pivot back a bit in order to provide clearance to the spring bell with a ball joint plate similar to the first rev (above).
on the
The wider ball joint plate gives me JUST enough clearance with between the rear link adjuster barrel and spring bell to make it work, but I don't like the wide ball joint plate. The front link can still use some work.




Rear link clearance to spring bell:



Forward link hitting spring bell; I think this is ok, as the ball joint plate appears to get lower than the stock control arm's ball joint plate when it's on what is effectively the droop stop.



Here's the baseplate for the new design. I don't know why the laser guy cut 4.

[The Dark Side of Will]

Of course when the prototype machinist txts me that he has cut the pieces I designed--which are essentially high square nuts--I realized that there's no reason I can't use high hex nuts. Those are only available in fine thread, so I'd have to switch bolts. If I'm switching bolts, then I have opportunities to switch other things too.

The clevises that connect to the ball joint plate are "compact clevises" which seem to be an invention of SPC... the part can be made from a round bar in the nominal diameter of the threads. The threads end up being way overkill for the strength of the clevis, but that means that the threaded shank can be hollow and light and allows larger diameter adjuster tubing, which makes a longer link less likely to buckle. Part of the design paradigm of the compact clevis is that its jaw opening is narrower than a conventional clevis. 5/8 & 3/4" conventional clevises have 3/8" wide jaw openings, for example, while a 3/4" compact clevis has a 1/4" jaw opening.

However, these links are short and the highest loads are in tension, so the buckle-resistance of a tubular structure based on 3/4" threads is overkill.

I can keep the 1/4" thick ball joint plate and go with a 1/2" conventional clevis, which I can get from McMaster with left hand thread. I can use 1/2-20 RH/LH adjuster tubes (Found! in steel at Summit) with the LH threads at the clevis end, allowing me to use RH thread 1/2" rod ends at the inner pivots. Going to 1/2" hardware makes EVERYTHING easier to package, makes everything cheaper and makes everything lighter. I'm going to go ahead and bolt together the prototypes with the 3/4" hardware I have, but will look at building follow-ups with 1/2" hardware.

[The Dark Side of Will]

All the BOM parts for the 1/2" design are here. The laser had some down time this week, so the latest rev of the bespoke parts didn't get made. That's ok, as I need to rev the design for the ball joint plate to accommodate the new clevises.

I ordered 1/2-20 LH clevises from McMaster, and QA1 parts showed up. If you order some types of extreme strength bolts and nuts, ARP parts show up... McMaster-Carr is becoming McMaster Speedshop.

The only ready-made 1/2" adjuster barrels I was able to find are swedged steel by All-Star, ordered through Summit. They're almost junk, to the point that if you don't already have taps to fix the threads, you should get the appropriate taps. I bought 4 and every one of them needed to have the threads chased in one or both ends. And of course because they're swedged steel, the outside is round rather than hex, so they're difficult to get a grip on to do said thread chasing or, you know, use them as adjusters.

[Series8217]

Forward link hitting spring bell; I think this is ok, as the ball joint plate appears to get lower than the stock control arm's ball joint plate when it's on what is effectively the droop stop.

My design does this too. The 88 front suspension can use a shorter droop stop anyway so I think it's fine. I just forgot to note it above.