Datsun Roadster: 2020 Challenge Build

checking in on this for the first time in a few months... wow what a bunch of awesome changes

Looks like I got a bit behind on my posting. 

Over the last week or so, I started with finishing up the rear trailing arms. Needed to plate the big openings, and trim some fat.

Some cutting, welding, and hammering and old cutouts from datusun body sheet metal become new filler plates.

Finally I painted them up (more cans of random leftovers!)

I also took another look at my wheels and the valve stem interference. I think I can now confidently cut more from the hubs to make some breathing room. This is the valve stem reversed.

Next I did a lot of welding and painting. Conveniently, the diff mount serves a great place to store the engine while you are welding and painting. 

I got the engine reinstalled but didn't take a photo yet. Then I painted the diff mount. 

Next up, do all the same stuff to the front suspension.

Adding in Nocones time on the spacer - a big thank you! - the total hours climbs to 785.

cruisermatt said:

checking in on this for the first time in a few months... wow what a bunch of awesome changes

I agree! Hopefully the way the car drives is transformed too.

Sunday I did more work. Final weldup on the front suspension. Remember to brace your brackets to minimize movement from the heating and cooling of the weld!

And today the repainting.

Also, I was missing one of the Miata lower control arm cam adjustment washers. I looked online and found them cheap but they didn't exactly look like mine. (Maybe my front subframe I used had aftermarket adjustment bolts installed?) So I was able to trace a washer on a cutoff tab in the scrap bin and then grind out the D shaped in the center with my Dremel and grind the outside with regular grinding tools. Not perfect but it works!

Finally, I had a couple of tiny bottles of evaporust that I think came as gifts at a past challenge. I never used them yet so I decided now was a great time to try. Dropped all the Miata lower control arm bolts nuts and washers in there to let it sit for amciuple days. We will see!

789 hours.

I added a 15ish% steering ratio quickener!

It's just a new hole closer to the steering axis. However, it also serves as a weight reduction mod! Hope to use this during testing to see if it helps get through slaloms a bit better, if not, it's easy to change back. 

I also checked for bumpsteer, and from what I can see (standing behind hub and sighting down the ruler) it's negligible. I'll also check with the steering turned left and right.

790 hours.

I'm not sure I ever posted this in the thread, but since I am now reassembling the front suspension I feel like now is the time. 

A while back I mocked up the front suspension in VSUSP (which is an awesome tool, btw). This is approximately how I had it for the first 2 challenges:

...yeah, not great. roll center basically on the ground, and really long virtual swing arm length means that as the car rolls, the outside front loses basically the exact same amount of camber. This may have been ok with rubber pucks and nearly zero travel (but actually I think it still wasn't helping), but this will definitely become a problem when we let the suspension start to move. 

Unfortunately, there's not much that is easy to change at this point. Ideally you'd have shorter upper arms than lower for camber gain during bump travel, and the chassis mounting points would look more like a 'V' than an 'A'. That's not something I can easily change now. However, I looked at what I CAN change. and that is I can change the length of the a arms a little bit (about .5 inch) by threading the rod end in or out. on the knuckle itself, I can also change the length of the knuckle between the rod end and the center of the wheel by adding spacers - you can see the ~2 inch spacer I've added under the rod end in the bumpsteer photo. I can do this both top an bottom. 

That led me to the following solution. By spacing the upper rod end up as much as im comfortable (the length of that bolt is the limiting factor), and moving the lower one down a bit too and then lengthening the lower A arm to achieve static camber to match, I can REALLY improve the suspension layout. It is still leaving some to be desired, but it is much more workable as we shouldn't lose camber on the outside front nearly as fast and the roll center is up off the ground. Note, this VSAL gave us our targets when we designed the rear suspension movements. 

I just remembered, I also raised the front ride height about an inch, this really helped get the roll center off the ground. 

I do love how much my front suspension looks like a Morgan 3 wheeler. 

Coming from the world of stock/street driven Datsuns,  offer these observations;

First, having add a steering rack quickener,  it does sharpen the steering response. On my car you now have to pay attention, all the time at any speed. Slow speed turning is also impacted.  I am running 195/60 14" Falken 615's on 14x7 rims, parking lots are now a workout.

You can shim the A arms much like an old chevy, at the two bolts the attach at the chassis. I was suppressed how much change I was able to induce with nominal shimming.  The amount of Ackerman angle built into these cars is effecting things that I am still figuring out.

David

Ok, now I can see you front a arms.  Never mind...

Hey, did I mention that I pulled these off my junkyard motor?  So 0 hours, $0 budget hit?

Uh, those look pretty optimal. Am I reading your caliper right the hole diameter is .36? Or is it .46?

How wide are they?

In reply to Robbie (Forum Supporter) :

The calipers shifted a bit, but .36" is close.  You're working with a 3/8" bolt, I assume? or Metric?

They are a little thick.  5/8 or thereabouts.  Couldn't remember that dimension of what you needed.

Mr_Asa said:

In reply to Robbie (Forum Supporter) :

The calipers shifted a bit, but .36" is close.  You're working with a 3/8" bolt, I assume? or Metric?

They are a little thick.  5/8 or thereabouts.  Couldn't remember that dimension of what you needed.

I actually just went through my cbr600 hardware bin to find the correct shock mounts bolts. They are m10x1.25, and have a nearly exactly 10mm shank/shoulder/(the unthreaded part). 

That said, I did find I have a handful of spacers that should work just fine for the task, so I don't think I need spacers. 

HOWEVER! If you're itching to build something for me, I think long ago we talked about brake light surrounds that look like fighter jet engine cones? I still think those would be awesome on this.

Dang! Another week behind on posting in here. I am sorry, I am rushing to get ready for a test and tune on Sunday so spending all my extra minutes in the shop. Let's quickly recap:

Saturday I finished putting the front suspension back together and getting it aligned. I don't know why this was so annoying but it was. Ended up at about 2 degrees static front camber and zero toe. That'll be the starting point.

Next I grabbed my rear hardware (mostly Miata stuff) out of the evaporust. Gotta say that is a nice result for simply dumping stuff in a bucket and waiting a while! You can see the cam washer I made by hand here.

That led to being able to reinstall the rear trailing arms. 

Next I took the diff apart to add a bunch of grease. Normally this would be lubed by the trans fluid, so grease is a slightly different method, but I think it'll be fine for shorter periods of time. 

I added electrical tape over some of the holes, and then installed the axles so I could manually differentiate a little bit to distribute the grease. Once I saw grease coming out of the visible holes there I called it good. (Still need to make a grease/dust shield for those holes).

More, shortly.

Last big fab job for now is to fit the rear brake. I cut the old bracket off the old chassis, and sorta mocked up how I wanted it (btw, that's a used sprint/midget circle track rotor, with a 3 hole bolt pattern on a 5 inch diameter bolt circle - which bolts nicely to my 12 on 5 inch diameter bolt pattern diff!).

Fortunately/unfortunately, the caliper needs to move with the diff, because I built adjustment into the diff mounts for chain tensioning and alignment. So that means my brake caliper has to move with all that stuff.

So we mount to the same place the bearing does, and we try to stay fixed relative to the bearing.

Square tube cut into brackets:

Bend a flat bar (that used to be a floor mount in the f440 chassis) around the bearing taking care to avoid the grease nipple:

Weld:

Here's where Nocones beautiful remote lathe work comes in. That's a 1.5 inch aluminum spacer for a Chevy van. The van uses a - wait for it - 6 on 5 inch bolt pattern, so the spacers holes line up perfectly with the diff and the brake. And it is perfectly 1.5 inches thick, and it forms a great grease/dust shield for at least that part of the diff. It also may be the single most expensive part on this while unit!!

Next I picked a good location for the brake. Wanted good clearance from exhaust, frame members, bolt holes, etc.

Clean and mark the bracket:

Test fit:

Cut an additional support piece from scrap:

Weld more:

One final issue was the brake rotor uses countersunk holes, and my hardware (m10*1.25 thread is the thread on the diff holes) was flange bolts. I couldn't find cheap bolts long enough with tapered heads, but I could find this cheap set of

 ATV lug nuts that come with adapters for both countersunk and flat wheels.

Perfect!!

And now, I hereby present to you, a chain-driven, braked, torsen limited-slip diff on a challenge budget.

Go Robbie, gooooooo!

Couple quick things that you've probably already thought of:
-Does the grease have a way to exit the housing anywhere near the brake rotor?  If so obviously something to keep an eye on.
-We ran an FSAE car one year with a Torsen and a centrally mounted brake like that- if there's a quick and dirty way to drastically increase the front suspension stiffness, I'd bring it to the event.  If they lift rear wheels at all, even slightly, weird stuff happens.

Fantastic progress!

EDIT: I see what looks like a very direct route to fling grease onto the rotor from the ends of the worm gears, even something like a cardboard tube jammed in there would probably help avoid a self greasing rotor.

That diff/brake/axle situation is bonkers. Can't wait to see it work!

¯\_(ツ)_/¯ said:

Couple quick things that you've probably already thought of:
-Does the grease have a way to exit the housing anywhere near the brake rotor?  If so obviously something to keep an eye on.
-We ran an FSAE car one year with a Torsen and a centrally mounted brake like that- if there's a quick and dirty way to drastically increase the front suspension stiffness, I'd bring it to the event.  If they lift rear wheels at all, even slightly, weird stuff happens.

Fantastic progress!

EDIT: I see what looks like a very direct route to fling grease onto the rotor from the ends of the worm gears, even something like a cardboard tube jammed in there would probably help avoid a self greasing rotor.

Yes, I do have a plan for a grease catcher - it is not much better than a cardboard tube. Might be worse.

As far as lifting rear wheels... I'll have to think about that. We can increase the front spring preload easily, but that doesn't really help I don't think.

In reply to Robbie (Forum Supporter) :

On the FSAE car, the bandaid answer was a massive front swaybar.

maschinenbau said:

That diff/brake/axle situation is bonkers. Can't wait to see it work!

Yes it is bonkers. I hope it works!

Can the grease holes be tapped?  Zerk fitting on one or two, actual tapped plugs on the rest?

Mr_Asa said:

Can the grease holes be tapped?  Zerk fitting on one or two, actual tapped plugs on the rest?

No. Here's a closeup of the issue. Worst part is the gears actually are proud of the case, so something simple like tape probably wouldn't even work.

That said, I started working on a dust cover. 

It's close, but not quite the right angle. 

In reply to Robbie (Forum Supporter) :

Put a sheet of aluminum under the bolt heads.  Cut a hole that just touches the diff and RTV it onto the disc..   should work to keep most grease in and dust out.

In reply to Robbie (Forum Supporter) :

Ahh.  That sucks.  They're probably proud so that the movement of the gears in the fluid helps lubricate them.

Weld-on lathed part?

Robbie, is that a dadgum styrofoam bowl?  That E36 M3 ain't gonna work.