• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

Volvo 122S Build Thread: Scope-creep the Sequel

Man this is awesome.

Did you measure a Miata rear subframe?

You bet...if it wasn't for all the autocross guys snapping that junk up, it may have been the winner. Gave it some good thinking as it's 56" hub to hub (IIRC) and aside from having to remove about what I did it packages pretty nicely (outboard springs/shocks are a PITA but I could have changed that). Probably easier if you're just going to swap in the existing subframe.

The issues were that it's good to about 300 WHP from what I've heard and has limited gear selections, and at the time there just wasn't one around. The Miata guys have developed an 8.8 swap for a reason. Even the Toyota was about a year of JY trolling. I don't live in a metropolis - we have one PYP yard and I've got to get most things out of Calgary which is 2.5 hours up the road. So it fell off the table.

The Toyota unit is good for more than twice that WHP and TRD has gear ratios covered for cheap to the moon. My unit came with LSD and a 3:91 - but I can change that if I wanted to from 3.0 ish to 4.88 or some such (which isn't happening) but is possible. Most consider the 8" Toyota to be pretty bomb proof. Bomb proof was the sell point to be brutally honest.
 
Makes sense. More of a complete swap if you're not going as extreme as you plan...

And I never thought about it, but I guess due to the rule sets in the series most populated by Miatas, the factory gear sets are adequate and thus there is a lack of aftermarket gears and LSDs. Well, compared to the 8.8s, 9", and other more popular swaps.

The guys really getting into the LS swaps for Miatas are trying to shoehorn Jag and even BMW rears under them now...
 
To continue the story - version 1.1 of this IRS swap goes like this. I made the critical error of not making a full frame table to jig pick-up point from and was mostly referencing the front suspension for locating the IRS subframe. I discovered that elements of my original effort to located the various arm locations created a degree of variability - the worst of which was the differential was out of square to the car by 1/4" with the subframe mounted straight and I didn't like that, so I decided to square the differential (thus squaring the drive axles and thrust angle of the car) to the car by skewing the frame. I now know this is stupid, but it seemed reasonable at the time.

This messed up all the suspension pick up points and I ended up with a square differential, but a wheel base that was not square (3/16" more on one side than the other) and suspension geometry compromises that I was not willing to live with. At around this point I did realize that I was in over my head and I took some time off (like a year) and basically read every book on suspension geometry I could find and got on with other projects. So the rear sat skewed for a long time.

Then I figured I could just reposition the suspension mounts and I got inspired and broke out the plasma and did this.



Then welded that mess back up like so.



Then put it all back under the car while I worked out how to mount the coil over. I was still not happy as the cross member was still crooked and I'm well on my way to OCD. But let's let around another 8 months go by.

I had to add a rear cross member for the frame to sit on. A little 10 ga bent up and bingo, we're in business. Now it's in crooked remember :-(. I added some stiffeners inside the cross member and welded on the brackets with sheetmetal returns.









And got busy with an idea for the coil overs.



I have to mount the coil overs a little goofy for packaging and trying to keep a useable trunk. Fitting the tube up in the car was a challenge.

But it worked out just fine.



Now it's still crooked - if that's bugging you, you can only imagine how much it's driving me nuts. I'm trying to make progress and would like to drive the car sometime before I die. There it is - the end of version 1.1. It's done, but I'm super unsure that it'll work. I'm not happy with the coil over towers but can't work out how to make them better, the subframe is an embarrassment as it's not perfect, and I simply can't finish projects unless they don't bug me. This is really, really bugging me. So let's pause for about another 8 months.

I'll show you the solution to all the issues in the next post.
 
Sorry for the delay - working hard.

Here we go again. The rear cradle is out to get corrected before final welding. I was always going to drop it to weld it up...but I WASN'T planning on having to redo the entire thing. So to recap - the cradle was welded in the car with the diff perpendicular to the car. To get this to happen, it had to be shifted about 3/16" to the rear. This caused a shift in the wheelbase side to side by the same amount and was causing all sorts of problems getting my suspension to work. Turns out you can't just shift this stuff like you would a live rear axle. Who knew?

So after much thought and a little swearing, I just undid my "fix" of the tube that I had done after waiting 2 years on the fence. Well sometimes it takes momentum to just do it properly. Now I don't have to account for a bunch of stuff that isn't right...like the rear cross member that I built and installed into the car out of square because of the shift in the cradle. Time to get this all squared up and done right.

The subframe has been mocked up on my welding table and I've used some 2 X 4" steel tube as reference rails. Everything is being squared to this reference plane. So off with the tube fix and refit the tube.



Tack the bushing holder back in place square and level. This takes a lot of time when the garage is over 30 C.



I'm also having issues with all the suspension mounts (lower) - they are so tight that when the subframe gets powder coated, there is no way the arms will fit. The torque rod mounts needed to go as they were too tight and not deep enough to accommodate the bushing. Not sure how I missed this detail - but the inside weld was fouling the bushing. So new ones were fabricated and placed in precisely the same location.



Old left - new right.



Jigged - dead perfect.



Done.



I also cut the tacks holding the two differential cross members in place and got the pinion dead square to the frame. No pics. Next will be getting the rest of the errors out of this subframe. I'm still not sure how I could have worked out the location of the pick-up points from the original without my jig...but I sure could have built this frame more accurately without the not so accurate jig. It's not really that bad - just a 1/16" here and there. I will get it to be much better than that.
 
Well, after another week of work, we're just about ready to wrap up the rear cross member and get it welded. I have to be away next week for work and this coming week won't see much progress, but after I get home, I should be ready to roll.

The next part that had to go was my fabricated cross member that held the differential snout. The one that I built didn't locate the toe arms correctly and I really wanted it gone as it just couldn't be fixed and not have it look like I hacked it.

So here's the start.

I had cut the brackets off in the hope that I could salvage the part - but you can see the bottom plane is not level and was off 1/2" side to side. So off it came.





Then I started to make this.



Join a few more tubes to handled both the toe brackets and the torque of the pinion trying to climb the ring gear.



And we have this. The bracket mount surface is perfectly level now.



The proverbial K member. The tube ends will be cut and capped when welding. Mounts are 1/4" steel with TIG welded captured nuts.



That's a day worth of tube fitting.



Toe brackets were fun to build as the two legs of the K are different lengths due to the offset of the pinion.



I built them longer then trimmed to fit. Hole saw came in handy for fitting and getting it all tight.



This bracket is mostly controlling motion to the outside/inside in an effort to keep the tire from toeing in or out. The way I had to fabricate it wasn't the way I wanted to do it, but there wasn't any other way to do this and still have things clean and free of areas that will collect dirt and moisture and if welded all the way around, it should be fine.



I left a mostly open corner on both sides of the bracket as that way I can get good penetration from one side.

Backside is notched for clearance.





Next up - fixing the coil over mounts.
 
Tacking leads to welding. Cracked open a roll of dimes on these parts tonight.



Welded all the way around the shock tower base.





Then put the reinforcing parts on and welded them up.


Tops coming tomorrow once things cool down.

31183234132_7dd6b9defa_b.jpg


A lot of this is done either with my left hand or seemingly with some part upside down. Tube is HARD to weld pretty.
 
A lot of this is done either with my left hand or seemingly with some part upside down. Tube is HARD to weld pretty.

It gets easier the more you do it. Fabrication looks really good!

I'm not getting the warm and fuzzies from the damper mounts though. Are you going to brace those towers to each other and/or down to the new frame rails?
 
It gets easier the more you do it. Fabrication looks really good!

I'm not getting the warm and fuzzies from the damper mounts though. Are you going to brace those towers to each other and/or down to the new frame rails?

I've thought a lot about this over the years. The solution that I've seen on cars like the F40 and the RS200 is to just join the two towers. So, I've worked out a solution.

10986334_917655748258956_954396954_n.jpg


18rbb9bsqapw2jpg.jpg


The design was not really inspired by either of these cars, but they both sport IRS's with high mount coil overs that are similar to what I'm working with. It's a little "old school" compared with how it would be done today and I could have switched it up to have either cantilevered or offset coil overs, but packaging was harder.

Here's what I've done. I made an exact scale replica of the rear shock towers using 3/32" TIG rod. Then I analysed the various stresses as I added parts. Sorry I didn't take pictures of the entire thing, you get the idea.

Without any cross bracing at all, the "towers" were very easy to move in bump or droop. They could be bent in every direction. Then with the addition of just the cross brace, all that happened was motions on one side were transmitted to the other side. it was a little stiffer, but I don't think I could characterise it as better, in fact worse in some ways as the motions were translate which would add to the stresses over time.

Then I added some 1/16" TIG diagonal braces following what was shown in the F40 and RS200. I used 1/16" as they used smaller tube and I happen to have some 1" 100 wall DOM. Bam - I can not make this move laterally at all. Or at least not with just simple hand movements. If I went full gorilla on it - sure, but the only thing you can do with this shape is twist it a bit which is not a force that it would see unless something catastrophic went wrong. It was shocking how much of a difference this made.

30574101054_4dd02eea5d_b.jpg
 
The entire design is actually done - so I'll just bomb away with what I did.

31327348512_e0e899290a_b.jpg


You can see it a little better this way.

31473554115_d2e59a5879_b.jpg


31473590345_30a4fbf1be_b.jpg


This gives me easy access to the shock bolt and other potential service items and I don't think sacrifices strength where needed. It also does meet my objective of getting the bar up and out of the way a little so the space isn't gratuitous in the trunk.

Bar in place.


31372955662_9583171fd7_b.jpg


Then I added the diagonals.

31585948145_01d61ff876_b.jpg


Both the tops and bottoms of this bar are attached using 1/2" captive nuts as I don't want to be working with more than one socket to take it out if the need should ever arise.

30776078123_ded4fed3bd_b.jpg


There are 1/8" plate doublers on the frame rails with nuts welded on to the plates. It's not all tacked up as I'm out of argon and that will have to wait for another day.

The main bar went together with 1/2" button welds plus the closing plates. It's not going anywhere.

31191957970_89fd45d35d_b.jpg


Once welded - it's not going anywhere.

The idea is that it can come out to make removal a little easier...but in the end it didn't matter when I refit the subframe. So it is what it is.

I'll post the rest later - It needs some serious sorting so this thread continues to "make sense" from a build perspective.
 
Time for another update. I have to try to remember where this all left off (takes a moment to scroll down - right)...it's been too long.

So the front brackets for the subframe are all welded in and I made sheet metal returns up to the floor pan. Start with some 20 ga bent to 90 degrees and stretch to make the curve.

31915039822_8bf1e7603d_b.jpg


That gets these done faster than you think.

31945653831_252aa780dd_b.jpg


Then weld them on and tidy up the welds.

31281141263_c6dffd4dec_b.jpg


Then I thought that even with the gussets, it might be worth boxing the top of the seat pan and joining it to the cross member for extra unneeded strength. So I made some cardboard templates (I'm getting good at these now).

32033689901_6024decae5_b.jpg


Scribed them onto some 18 ga steel (love the smell of blueing).

31310508884_89d3b98fa2_b.jpg


And got to work bending this all up.

32034209771_f6e1cd51e7_b.jpg


Good patterns produce good parts.

32034566131_2291a9fbdf_b.jpg


Welded up the joins.

32128216656_2619d6f6cf_b.jpg


Welded them in place - the tricky part was accounting for the slope of the cross member.

32021608432_71730e1a77_b.jpg


Seat fits in and you can't see a thing - perfect.

31795001960_21a1ef4a2c_b.jpg


Then I gave the subframe a quick shot of black paint to hold it until I'm done fabricating and get it powder coated.

31942725781_72bd2f8794_b.jpg


Stuffed it all back in the hole and started to work out the sheet metal for the trunk.

Turns out I didn't need to make the strut bar removable, but it was probably easier to fabricate this way - or at least that's what I'm telling myself.

32187468202_a71ffe1b12_b.jpg


Time for some serious pattern making.

32217786991_6a822ef7cf_b.jpg



I also made this panel - didn't take pictures of how. It's just a closing panel with dimples and flanges.

32318918002_18be20b18e_b.jpg
 
Then on to the rest of the trunk. Lots of pattern making - first in tape, then paper, then cardboard, then wood (depending on what it is), then metal. You get the idea.

A few tape guidelines to get the general shape of things.

32423844122_d815a4e2cc_b.jpg


Then some cardboard templates.

32035760390_18a36c82ef_b.jpg


Not really loving this design - the idea was that I'd like to have access to the shock towers to change springs, adjust shocks or whatever else you do back there.

A little more tape...it's starting to take shape.

32197681480_54d9e1e914_b.jpg


Then I built the centre section...it ended up looking a bit like a BBQ lid, but it gave the maximum area.

Put together the end plates first. Not bad for fit up.

32154375874_68226c3e72_b.jpg


32957664886_84bb05996c_b.jpg


Then I rolled out the middle bit. Formed on my MIG trimix tank.

32617413140_8df184caab_b.jpg


Then tacked it all together.

32185005723_a4cef7917c_b.jpg


Done.

32876018751_6db5f99fe1_b.jpg


Then I'm going to need a closing panel at the top of the trunk (bottom of the parcel shelf.

It starts like this...a little shrink and stretch.

32349996560_ab7b3e38c4_b.jpg


And you have this.

31887435204_d37a319cb9_b.jpg


32577393502_aa67a05ecb_b.jpg


Side parts to extend from the wheel housing to the new metal.

32621009572_2eb26e0c4f_b.jpg


Stuff all that back into the trunk with a few cleco's and we're testing with tape again.

32779729361_094b6e3678_b.jpg


I didn't like the stealth fighter look of my previous design. So the angles evolved into these things.

32779728131_7d047fbaae_b.jpg


Turn a few flanges with the tipping wheel and they start to look a bit like shin pads. It's starting to come together but I'm not liking the joins...and the right hand shin pad looks a bit wonky.

32846536562_97357034c4_b.jpg


So I added a return flange to the top parcel shelf panel.

32975515286_a30abbeaff_b.jpg


Which ended up like so.

32863783692_2626a4d784_b.jpg


Then make a matching return on the BBQ lid, roll some steps in the shin pads (remake the right hand one to match the left) and remake the pan as it wasn't perfectly symmetrical.

Ta Da.

32925957903_48ff3aa592_b.jpg


33609899771_8d36e5ce4c_b.jpg


Just a few little flanges and finish work and the trunk is all done.

Clearance is good all around.

33739070535_818ce8ee4f_b.jpg
 
Back
Top