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BA5 Reader
11/21/19 7:07 a.m.

I've always wondered a bit, but I'm pretty sure it's Milano Red.

Yeah, I'm a really big fan of the 3g's (obviously) and the 5g carries on that on better than the 4g's.  The 4g's are good cars, but are different.

mr2s2000elise Dork
11/28/19 2:24 p.m.

Super low mile one on BAT now in red 

too bad gimpomatic 

BA5 Reader
12/6/19 6:02 p.m.

While I'm waiting on some steel to arrive (never had something take this long to arrive from McMaster!) I worked a bit more on my subframe.

Here's teh general design.  It's some structural steel tubing that will tie through some base plates to the actual frame of the car.

It's nice to have access to tools that let me know I'll be ok.  I'm putting quite a bit of safety factor on here..... or alternatively I'm designing with the assumption that one day this will be able to pull a LOT of G's!

Here it is in place on the car.  I'm pretty happy with this design (you can see it's not really fully fleshed out, a lot of the detailing I'll do during fabrication).  Now I need to design the rear toe links.  They're going to tie into the same frame plates.

corradocorrer New Reader
12/10/19 8:07 a.m.

how is the rear subframe assembeled, is it also all epoxied together?

BA5 Reader
12/12/19 6:31 a.m.

The sub frame is going to be welded and bolted together as a subassembly.  I couldn't come up with a simple solution that would allow me to get the surface area for bonding the pieces together.  Plus, the center section will be bolted together because I need to be able to drop the engine/transmission out through the bottom of the car.

However, I am going to epoxy the sub frame to the car.  In the FEA that would be the surface that is all highlighted by the green arrows.  As you can see I have a bunch of surface area there.  

BA5 Reader
12/12/19 7:31 a.m.

Unfortunately I'm still waiting on some material from McMaster.  But in the meantime I suppose I should at least start getting things ready.

Starting with the frame rail as is:

It's got some lovely underbody coating on it.  Luckily I had stumbled across another thread on here where someone was trying to remove this stuff and they recommended carpet adhesive remover:

First I cleaned ~30 years of road grime off.  Then per the directions I scored the adhesive so it could penetrate better.  You can just kind of see the scoring on the left

I didn't get a picture of the next step, but you're supposed to let the stuff soak into the adhesive over a couple of hours.  You're also supposed to dilute it on the order of a few ounces per gallon of water.  It'd be hard to dip the frame rail in it, and I figured underbody coating is probably a little tougher than carpet glue, so I soaked some paper towels in it (full strength) and then just pressed them onto the rails.  The fact that they were wet made them cling to the rails.  I then let them sit overnight.

It worked reasonably well.  Here's where I started scraping.

The bottom edges came off ok, but the coating was a lot thicker at the top and I got impatient.  So I busted out the grinder with a flap disc.  I was worried it would just smear it around, and it did a bit, but it really took it most of the rest of the way off.

I'm going to wipe it down with the adhesive remover one more time and hit it with a new flap disc to get it all really perfect for bonding.  Luckily the coating only seemed to be on the outside fo the frame rail, so I only had to take off paint for the rest of the area.

BA5 Reader
1/9/20 3:44 p.m.

So it always feels like forever between updates because I spend a lot of time designing and redesigning before I actually start fabricating.  There's also usually a couple of false starts in there two.  Sometimes it feels like I'm not making any progress on it, but luckily all the prep work makes the fabrication part go a lot more smoothly than I suppose it might otherwise.

It's finally time to start fabricating the rear suspension and subframe.  One of the big tricks is how I was going to located it, since the suspension pickups are basically just hanging out in space.

I'd been staring at the measurement tool in SW for a long time before I finally dawned on me that I could create essentially the same thing in real life:

It's just a bit of thick solder measured and bent to shape.  Is it accurate to .001"? No.  But it is better than .1", which I figure is about as accurate as my fabrication skills are going to get for this anyway.

I took this next picture because I liked the wierd perspective.  All the bends are orthogonal to each other, but it sure doesn't look like it!

So then I just hot glued it into my locating hole on the car.

I took some measurements from some other locating points and made sure nothing was sagging and it looks like we're all good!

So I have my steel and suspension pieces, so now it's just a matter of cutting and grinding till everything fits.  That'll hopefully be coming quickly over the next few days!

BA5 Reader
1/27/20 2:15 p.m.

Got a little bit further.  Got the first subframe piece fabbed up.

It's a piece of 3 x 3 x 5/16 steel tubing.  Just cut the angle.

Here I'm layout out the suspension member so I can make sure the window I cut is large enough.

Then get your son to help you cut out the window.

And here's how it all mounts up.  Right now it's just hot glued in place.  That way I can place everything and then I'll take it to my brother to weld it up.

LudeAEM New Reader
2/19/20 1:00 p.m.

yes Looking great man!

BA5 Reader
3/24/20 1:49 p.m.

I've been working on it before as well, but I'm certainly not one to let a catastrophe like this go to waste with regards to building my race car!

Next up is the toe links.  They take quite a bit less loading, so they're built out of smaller tubing.

But they're fabricated pretty much exactly the same way as the control arm mounts.

And then they're mocked up using the same method.  The rear is starting to look like an honest to god subframe.

Ignore that it doesn't look level.  I'm not sure why I'm able to level a whole car but can't take a straight picture. :D

The toe links are designed as well, just need to get everything in from McMaster.

Next up is to finish up the design for the radius rods and their mounts.

BA5 Reader
4/3/20 2:02 p.m.

Since it's going to be harder to take the parts in to be welded by my brother for a while, I decided to go ahead and bite the bullet:

All the reviews say that it's a really good bang for your buck welder.

Nickoftime22 None
4/13/20 3:28 p.m.

Really good to see someone working on a 4ws 3rd gen. I just got one myself and its hard finding any aftermarket support. Really ambitious swap, good luck!

BA5 Reader
4/15/20 7:28 a.m.

Alas it won't be 4ws after the swap, but I suppose the 4ws was only ever to make up for being FWD....

wheelsmithy (Joe-with-an-L)
wheelsmithy (Joe-with-an-L) UltraDork
4/15/20 8:11 a.m.
BA5 said:

Alas it won't be 4ws after the swap, but I suppose the 4ws was only ever to make up for being FWD....

My guess is you'll be able to steer the back wheels with the loud pedal. Great work.

Robbie (Forum Supporter)
Robbie (Forum Supporter) MegaDork
4/15/20 10:10 a.m.

didn't the 240sx have an optional rear wheel steering feature? HICAS? not that it's really relevant to this thread, but still.

And I still love this build.  

BA5 Reader
4/24/20 7:57 a.m.

It's Christmas Day for this project!  The welder is supposed to come today, so I'm excited to get my toe mounts tacked up!

In preparation for that I fabricated my toe links.

I used 1" hex stock.  It's beefy and kind of overkill, but the driving factor was how much meat I have at the base of the threaded holes, and i didn't want that fatiguing.  And I'm designing this for an engine with 500 ft-lbs of torque in anticipation of eventually dropping in a turbo charged J37 or something like that.

All my parts to make my toe links:

The rod end is the left handed thread, and the ball joint is a Prelude ball joint to attach to the Prelude upright I'm using.  The threaded rod is high strength threaded rod, which was surprisingly expensive.

It's pretty easy to find and mark the center on these.

Cut them to length, and use the grinder to bevel the ends.

I'm quite pleased with how they turned out.  I can wait to get the toe link mounts tacked up so I can mock everything up.

I need to do some final design work and checks on my radius rods, then fabbing those up will be the last major suspension component.

BA5 Reader
4/24/20 8:42 a.m.
wheelsmithy (Joe-with-an-L) said:
BA5 said:

Alas it won't be 4ws after the swap, but I suppose the 4ws was only ever to make up for being FWD....

My guess is you'll be able to steer the back wheels with the loud pedal. Great work.

Way back when I had a 2006 GTO and took it to a track day (Little Talladega, which is still one of my favorite courses).  When I pulled up to go at one point the guy stopped me and asked "you've been out on track before, haven't you?"

Me: "yeah" (I'd been doing it for a number of years at that point)

The track guy: "Have fun, but maybe do a little less of your steering with the throttle..."

BA5 Reader
4/24/20 9:03 a.m.
Robbie (Forum Supporter) said:

didn't the 240sx have an optional rear wheel steering feature? HICAS? not that it's really relevant to this thread, but still.

And I still love this build.  

They did.  HICAS was the Nissan 4ws system.  

The unique thing about the Prelude 4ws (and specifically the 3g 4ws system) is that it was a completely mechanical linkage attached to the steering wheel, so one could learn to drive to it.  Most (if not all) other 4ws systems were either passive or electronically controlled.

BA5 Reader
4/28/20 11:00 a.m.

Got the toe links roughed in.  As you can see in the video I don't have the proper bolts or spacers in yet and tightened down so everything can flop around still.

But still, it's headed in the right direction!

You can kind of see in the video that even with everything loose the toe is mirroring how it got designed.  It toes out on droop (so the inside tire points *towards* the turn) but compression is pretty stable.  I wanted the toe to be as stable as possible on the loaded side, so I gave up some stability on the unloaded side. 

And from the rear.  The mounts will be trimmed back and cross braced.  Ground clearance won't be great, but it'll be ok, and it's all in line with the wheels, so it's at least somewhat protected.

Robbie (Forum Supporter)
Robbie (Forum Supporter) MegaDork
4/28/20 11:21 a.m.

looks frickin awesome!

Run_Away (Wears Clogs)
Run_Away (Wears Clogs) Dork
4/28/20 1:20 p.m.

Really cool! 

Not far from being a roller?

BA5 Reader
4/28/20 1:25 p.m.

It's getting pretty darn close.  That's the goal I'm reaching for right now.

BA5 Reader
5/1/20 1:18 a.m.

Whoops.  That's not right.  Those angled lines are my toe change over travel.  That's about 1.5 deg /in, which is waaaaaaay too much.

After some investigation, looks like I drilled my toe link mounting holes about ~ 1/2" too low.  Luckily a relatively easy fix.  

I was a little dubious that being a 1/2" low would throw my toe off that much, so I went a plugged it into my model.  And voila!  Toe curve goes all out of whack!  In exactly the same way I'm measuring, to boot!  Toe is a pretty sensitive little turd.

BA5 Reader
5/14/20 9:07 p.m.

Time for a little good ol' fashioned GRM build thread task organizing!

So I wanted the full setup before I make any real adjustments.  The last link to be built was the radius rod.  First up was the chassis mount for it.  I posted the design a little further up.  I tweaked it a bit from that, but I'm really happy with how it turned out.  It's just some cut up aluminum plate that's bolted together.

And it mounted up to the chassis without a hitch!

The radius rod itself is just a piece of tubing with threaded tube ends from McMaster.  This an example of where some funky design leading to cost savings comes in: I already had a left hand M12 x 1.75 tap on hand from making the tie rods (the other end of the tie rod was the standard M12 x 1.25 thread that Honda ball joints use).  Since the fine threaded rod ends are harder to come by, I just put two left hand threaded rod ends in the radius rod.  That saves me from having to buy another tap.  But left hand M12 x 1.75 threaded tube fittings aren't available from McMaster, so I just got a 3/8-16 fitting and drilled and tapped it.

So now my radius rods have metric left hand threads at both ends.  Nothing too crazy, but I was just thinking how if I were to ever sell this car (not that I ever would) someone would one day give a serious WTF! to that.

Anyways, once that was all fabbed up I could finish up the suspension:

I'm really quite happy with it.  The track, wheelbase, and camber are all correct.  I still need to correct the toe, and in the video below you can see that I need to finish up the subframe components so I can really measure it (they're flexing quite a bit because they're currently just located by a couple of screws.

You can see in the video that I don't have a whole lot of travel.  I have a couple of ideas as to what's binding, but I need to by systematic in flushing them out.

  1. Properly welding in the subframe mounting components.  There's some bracing to be done to tie it into the frame rails.
  2. Tie the left and right half of the subframe together.  That's going to be some bolted braces that connect the two halves top and bottom.
  3. Re-angle the control arm mount.  It's in the right location, but pointed in slightly the wrong direction.  This is putting some distortion on the mounting bushing that doesn't need to be there.  It's only tacked in place, so I'll just cut the tacks and retack it.
  4. Fix the upper ball joint angle.  This is probably the toughest one that I don't really have a good solution for right now.  The suspension moves ever so slightly out of the plane of motion that the ball joint is designed for.  I've been getting incrementally closer, but I'm not quite there.
  5. Correct the toe mount.
  6. Repeat everything for the other side!


BA5 Reader
10/20/20 1:29 p.m.

Well! It's certainly been a while!

My wife got me a Nintendo Switch for my birthday, so the kids and I got detoured from this project for quite a while since Calamity Ganon needed to be defeated.  But now that Hyrule is safe once again (!) I can get back to our regularly scheduled program.

So when I left off, I had gotten most of one side partially fabbed up, and was wondering about some binding issues in my suspension.  But my mounts were just loosely bolted on so I didn't feel like I was getting a good feel for what the motion was really like.  So the first thing I worked on was getting my mounts tacked in place.

I needed to remove some brackets, but that was an easy matter of drilling it out the spot welds and hitting it with a hammer:

After that I needed to gusset up my mounts.  As always paper templates to the rescue!

I was a little sloppy with my templating: I figured extra material wouldn't hurt here and I can always clean it up later if I really need to:

And tacked everything else in place as well:

NOW it's stiff enough for me to really tell what's going on.

So this picture shows the two issues:

Issue one is the angle of the ball joint.  I'm using the standard rear control arm, but mounting it to the front upright.  3g Preludes have a funky 'sideways' rear ball joint as standard:

But that won't fit on the front upright, which uses a non-right-angle ball joint.  You can see in the first picture how it's already off at a funky angle.  That's basically at the limit of the ball joint travel, so the ball joint binds during suspension movement.

After pondering a whole bunch of funky/expensive solutions that I wasn't really happy with, I finally remembered these:

Beveling washers!  I bought a pack of those and slapped them in there.  It leveled out the angle of the ball joint and solved that issue!

But the bigger issue is that the upright and the spring want to occupy the same space. :( It took me a while to realize it, but the only good solution I can think of for that is to go with a pushrod type suspension.  Fairly straight forward, but a good bit more design and fabrication.  For the meantime I'm finishing focusing on getting the suspension links and geometry fabricated and finalized.  I'll tackle that once the links are done.

And then just today I'm finishing up the upright.  I really like the ARP extended wheel studs, so I added some.

Installing wheels studs is a nice, easy, satisfying job.

And then I took that, my wheel bearing, and my upright to a local shop to have them install the new bearing and hub.

I'll install that tonight.  So it's a Subaru transmission, and a subaru hub (just by luck a WRX hub will press directly into a Honda Prelude wheel bearing!), which means that I should be able to use an off the shelf Subaru axle.  I checked my lengths and it looks like it should work out.


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