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Teh E36 M3
Teh E36 M3 SuperDork
4/8/21 7:56 p.m.

Well, a lot of time, and visually at least, very little accomplished. But got the upper a arm mounts done. Made a jig to get it accurate and replicate my final VSusp design.

Final VSusp 

 

bgkast (Forum Supporter)
bgkast (Forum Supporter) PowerDork
4/8/21 8:11 p.m.

Looking good!

nocones
nocones UberDork
4/8/21 8:38 p.m.

This is getting so good.  

Teh E36 M3
Teh E36 M3 SuperDork
4/12/21 11:03 a.m.

A note- the original plan was to go inboard with the GSXR1000 shocks, but damn... there just is not enough room for everything inboard. So I'm headed back outboard, but leaving the swivel link and I'll put a static pushrod in there for gross height adjustment, and will allow for future inboard placement if I am not getting enough travel out of the outboard arrangement. Sort of messes with my spring numbers and travel, but I'm going to punt on that for now. 

 

I HATE compromising. But I have an exhaust that needs to go in roughly the same place, and on the other side, a steering column. 

On the exhaust- still planning to run through the tunnel- I'd love to do a front exit, but fear it will just be loud and stinky.  Anyone have experience going through the tunnel and dealing with heat issues? I was thinking of shielding it with another piece of stainless and then maybe some insulation on the inside where/if there is room.

Teh E36 M3
Teh E36 M3 SuperDork
4/17/21 8:36 p.m.

Finally a day with good progress. Still not as much as I wanted, but I'll hopefully be done with the front suspension tomorrow after I finish weld everything, mount the rack, and shorten the tie rods a smidgen. 

I cannot adequately express how good this feels to see wheels on this motherberkeleyer.  I had a couple obstacles that threatened beer thirty (giving up and drinking the rest of the day) at about noon, but I think I'm out of the woods- the inner tie rod has miniscule clearance on the lower a arm, but I think I can raise the rack a bit and overcome. 

#2 was the forward mount of the upper a arm- I want it horizontal so I can adjust anti-dive a little bit, and it was binding at 80% of travel.  I sat on it for a minute and then adjusted the tabs so it won't bind in the whole travel. Which is good. 

Travel is 5". I hope that's enough, but as ground clearance is also 5", it's probably as much as I can realistically have- 1/3 droop means that I have 3.4" bump travel, so at max bump I'm at about 1.6" ground clearance. Yet another reason I've got to run a through the tunnel exhaust.  

Anywho- pics. 

nocones
nocones UberDork
4/17/21 9:05 p.m.

In reply to Teh E36 M3 :

This is so rad!

Everything is looking great.

Teh E36 M3
Teh E36 M3 SuperDork
4/17/21 9:39 p.m.

Dude, I'm so excited to get wheels under this thing- hopefully tomorrow ends with a good rack mount, and finish weld the "subframe" up there, put springs back on the shocks, and be done up there for a bit. Get to the IRS- I'd love to get Dutchman working on the axle shafts so I can get that sorted.

Teh E36 M3
Teh E36 M3 SuperDork
4/19/21 6:35 p.m.

Got the Steering rack mount made up, and finish welded the front subframe. I didn't get underneath but all the crap on top is now welded, and I'll be using about 40 flap discs to clean it all up.  I figured I'd do a torsional rigidity test between the frame rails while I had everything off it.  So, whatever this all means, but I am 190 lbs, butt centered at the 4 ft mark of a 2x2 steel tube. My handy dandy digital level showed .6 degrees deflection, repeated several times. 

So, 4ftx190lbs/.6 degrees = 1560ftlb/degree?  Still no trans tunnel, the passenger footwell is unfinished, etc etc. Maybe this is a good start?  I don't have any idea what's considered adequate or good, but read that OZ requires cars with 4 cylinder engines to have 4000nm/degree, and the conversion for mine is like 2200nm/degree give or take.

 

nocones
nocones UberDork
4/19/21 7:50 p.m.

Our rule of thumb for the FSAE car was a minimum of 10x the difference in roll stiffness front to rear.  We designed the actual suspension points to stay very stiff relative to each other on the relavent end (8 front points rigid to each other, 8 rear points rigid to each other).  The chassis only needs to be stiff enough to transfer weight from the front to the rear (or vise versa).  At 10x the stiffness difference it can achieve that.  

I didn't even check it on the MG nor will I on the Subaru.  They will be stiff enough.  I may try to twist the rear subframe just go make sure it doesn't have excessive flex.

I never really understood the modern obsession with ungodly stiff chassis.  It's became a metric like towing capacity that doesn't really mean anything so long as you increase if by 15% every generation..  .

Teh E36 M3
Teh E36 M3 SuperDork
4/19/21 8:32 p.m.

Bro it is great to hear an engineer say that. I have an ME and my instinct is to obsess over it until I lose my mind, but I didn't get crazy on the 4age Midget so I'll try to let it go- get it as stiff as I can but not kill myself over it. 

Shavarsh
Shavarsh Reader
4/21/21 12:06 p.m.

In reply to Teh E36 M3 :

As another ME I can relate to the losing your mind part

nocones
nocones UberDork
4/22/21 9:25 a.m.

It is VERY easy a a Mechanical Engineer when building something like this to just fall into the hole of trying to Engineer the whole thing.  I try really hard to use my Engineering knowledge to understand the basic requirements on a particular part and identify the critical dimensions (Be they physical demensions, load paths, heat resistance, whatever is important) and ignore the rest.  I always remind myself that real car manufactures employ teams of 100's of engineers to optimize their designs and unreliable bad designs still happen.  It's better to get the car done and on the track than have it half done in the garage and be "perfect".  

Teh E36 M3
Teh E36 M3 SuperDork
4/24/21 9:51 p.m.

Well said, and amen. My goal here is to design perfection, and try to build perfection, and then be ok when it is imperfect. Each of those steps is an intermediate compromise, but the desire to achieve perfection- and in the words of Tin Cup- "perfection, unattainable", maybe gets me past the shadetree mechanic who can have it running by the weekend, and a little closer to the guy who's building a legitimate good car.

Teh E36 M3
Teh E36 M3 SuperDork
4/25/21 7:25 p.m.

Almost zero today but got a small wind after re-renovating some bathroom E36 M3. My tub refinish epoxy failed around the drain and it berkeleying sucks. 
 

so, this. Upper rear a arms. 

 

lowers. 

Teh E36 M3
Teh E36 M3 SuperDork
4/27/21 9:58 a.m.

Got some more done yesterday. Getting there slooooowly. Lower picture is of my power plant frame. I'll be plasma cutting a piece to go between the bars and losing the placeholder piece. Even without the stiffening, it actually sorta works.

Teh E36 M3
Teh E36 M3 SuperDork
5/2/21 9:05 p.m.

Some progress today- motivation was tough to come by, but I found some. Rear inboard mounts roughed in. I adjusted my geometry to raise the rear roll center at the expense of swingarm length.  It's at 4 inches now, and swingarm at ride height is 62".  NoCones' thread gave me the inspiration- making the complicated math into metal isn't easy, but with some jigging, and creative welding, I have a rough setup that I'll reinforce with gussets once I ensure it fits properly under the car.

Vsusp 

 

nocones
nocones UberDork
5/2/21 9:43 p.m.

YES!  GET IN THERE!

That looks pretty good.  Glad to hear my ambitious stupidity is helping others!

Depending on what your camber settings are you may wish to bring the rear upper bracket forward some.  When the upper arm gets shorter for camber the distance between the rod ends will reduce also and you'll have ot adjust shims.  It looks like your close to running out of space.  

I'm excited to see how this will bolt or weld into the chassis.  

Teh E36 M3
Teh E36 M3 SuperDork
5/2/21 11:12 p.m.

You are totally right dude. I dont want you to be in this case, but you are. First thing I'll fix that. 

bgkast
bgkast PowerDork
5/2/21 11:27 p.m.

Rear suspension Looks Great!

On the front mount for the front upper A arm at you going to add any reinforcement to the triangle that comes off the main chassis tube? (First picture at the top of the page) It seem like there would be a good amount of twisting force on the chassis tube as is.

Teh E36 M3
Teh E36 M3 SuperDork
5/2/21 11:54 p.m.

Yeah- so, I hadn't planned to triangulate that, because I don't think the upper a-arm has a hell of a lot of force on it- I'm looking at, what 2 G max braking, 1500lb car, 100% weight on front wheels, call it 3000 lb, 1500lb per side, 750 per balljoint, 375 per upper mount. E36 M3, maybe it's worth another few ounces to lay a gusset in there. 

 

(The math is just complete and utter bullE36 M3, but gives a small approximation of what's up)

nocones
nocones UberDork
5/3/21 12:12 a.m.

In reply to Teh E36 M3 :

for that node in question just take a large adjustable wrench or vice grips and grab that tube where the load comes in (So you are in essence extending the horizontal tube forwards).  Try to flex it towards the center of the car and see how flexy it would be.  I think it will be ok, but you may get a bit of movement because of the torision in that tube running  diagonally forward.  

I'm not sure how your radiator will be mounting but an easy solution if you get twist in that node is to just run a tube horizontally from each front upper suspension node.   This tube would be a convienient place to mount the top tabs for the radiator.

Teh E36 M3
Teh E36 M3 SuperDork
5/3/21 3:46 p.m.

I like the radiator solution. I took a bigass crescent wrench to it today. It's not moving. 

Teh E36 M3
Teh E36 M3 SuperDork
5/4/21 7:04 p.m.

Some work got done today- I keep getting sidetracked by house projects and work stuff. Boo. 

So, the third repositioning of upper mounts, maybe not the last, but hopefully.... A bunch of shenanigans and up/down, in/out, etc. Pain in the ass- hopefully good news tomorrow and some good pictures of a "finished" product- gussets, finish welds, etc need to happen, so it might be a two day process. 

And then the damn shocks/mounts will be an adventure.  But for now, pictures. 

 

 

 

Teh E36 M3
Teh E36 M3 SuperDork
5/5/21 11:08 p.m.

Progress is incremental. It takes forever to just do the smallest things. Spent like four hours aligning it off car and moving lower mounts a little inboard so the tires have a little more clearance on the fender. 

nocones
nocones UberDork
5/6/21 1:13 a.m.

Be sure to include some droop limiters in your next iteration of the rear suspension laugh

 

I'm impressed that your getting a full IRS with ability to move within the Square wheel arches.  That's awesome.  

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