Datsun Roadster: 2020 Challenge Build

In reply to Mr_Asa :

How's this? Very simple. And the OD is not critical, just needs to be bigger than about .75 or so.

Honestly I have some aluminum plate that is 3/8 thick, and that might be a good place to start.

Ok, it's time to get serious. Long way to go and not long till we need to be there. 

I needed to make the 5*114 wheels fit the 5*110 hubs. Also, the centerbore was a little small on the wheels. 

Solution? Drill the lug holes one size larger and open up the centerbore with a burr and Dremel. 

The fit is very good (after removing the steering link from the knuckle), and will be perfect after I remove just a little more material from the outside of the brake mount bolts.

Unfortunately, since I made these wheels out of 4 "outer" halves, the inner halves have valve stems. One wheel it is no problem, but on the other wheel the valve stem was installed much more outboard and it will not work at all. Valve stems need to go. 

All that work on the wheels put me back about 4 hours, up to 672.

And THEN, ladies and mostly gentleman, we have the foundation of rear suspension.

We had a separate thread talking about the virtues and complications and calculations on semi-trailing arm suspension. It escalated when nocones made a spreadsheet that did all the design calculations for us. We aimed for a roll center a tad higher than the front, a similar camber curve to the front suspension, and an anti-squat number that "wasn't horrible" (I think we ended up around 50% Anti-squat).

Then, we had to transfer spreadsheet to metal. We used wood to make ground lines, mark axle centers, etc.

Then we made our virtual swing arm out of string. (It needs to be 69 inches long - I didn't plan it that's just what we have to do).

Then, a free Miata subframe that Gumby got from EvanB (initially for a different project that no longer is with us) enters from stage left.

That donated lower a-arm brackets, and one un-bent a arm. 

Combining the brackets with a couple of scrap desk legs (add 6lbs 6oz to budget) gave us trailing arm mounts that fit Miata front lower arms. 

Then it was as simple as making the mounts go around the string!

Second side (you can see the first side has the Miata arm attached).

Behold! (Also, see the roll center where the string crosses the vertical line on the 2*4 - the bottom of the 2*4 is the ground).

Again I had some excellent help, and I'm nearing the 700 hour mark at 693 hours.

Robbie (Forum Supporter) said:

In reply to Mr_Asa :

How's this? Very simple. And the OD is not critical, just needs to be bigger than about .75 or so.

Honestly I have some aluminum plate that is 3/8 thick, and that might be a good place to start.

I missed this! I'll start workin on em, how many you need?

Watching Dan's spreadsheet come to reality in 2x4's and string was a thing to behold!

Smol adaptation required for connecting the Cobalt knuckle to the Miata swing arm

Yes this was cool.  Hopefully it works. The next build day should be really good for progress this one was very fiddly to get the suspension roughed in.  

Mr_Asa said:

Robbie (Forum Supporter) said:

In reply to Mr_Asa :

How's this? Very simple. And the OD is not critical, just needs to be bigger than about .75 or so.

Honestly I have some aluminum plate that is 3/8 thick, and that might be a good place to start.

I missed this! I'll start workin on em, how many you need?

Just two! 

Robbie, on the typical NASCAR wheels, there are two valve stems. For events without the inner liner those can be sealed with a threaded nutted and lock tite'd plug. Usually brass, but can be aluminum or steel if easier. A fine thread bolt and nut can supply the needed parts.

Berking Heck, this is cool! 

Yesterday I was able to build wood mockups for the rear hubs. This took me a lot longer than it probably should have, but oh well. Blame my crappy drill press that can't put a reasonably straight hole where you want it. That problem should be resolved soon. 

And then

Everything is lined up, about 1degree of camber on each side, wheelbase is matching side to side, and toe in is about 1/8 inch total (just by luck). I will probably shim the hubs in the mounts before making permanent so I can get closer to zero toe as a starting point.

Today I pulled the bearings off my diff. Luckily they didn't fight me very hard. I appreciate that Mr diff.

698 hours

stafford1500 said:

Robbie, on the typical NASCAR wheels, there are two valve stems. For events without the inner liner those can be sealed with a threaded nutted and lock tite'd plug. Usually brass, but can be aluminum or steel if easier. A fine thread bolt and nut can supply the needed parts.

This was my first thought but the location of the one that interferes is perfectly awful. I'm not sure there's room for even a thin bolt head there. (Maybe if I tighten it and then grind it down). 

We were also thinking to just jbweld a cover on the inside. 

Wow, I haven't checked in for awhile I guess. The miata trailing arms are genius! Will be following more closely.

Time for a big update!

Now that the hubs were located, it is time to turn my attention to the diff. 

First I noticed that at the last challenge I had finally overcome the keyway's torque capacity...

Well I do need to try and re-use this sprocket. Need to cut a big hole in it. Don't have a lathe.

Wait, maybe I do have a lathe...

If I use the grinder while turning the axle, then I'll get "lathe effect". It actually worked better than I thought, as the grinder tended to rotate the axle on it's own and I just had to lean my arm on the brake rotor to keep the axle from going too fast. 

After not too long I had this:

And then:

I'm very excited to be done working with this 1" axle. Set screws, collars, keys, everything is always stuck, etc. 

Unfortunately, I went a bit too small on the hole in the sprocket, and therefore I had a LOT more grinding to do before I could fit the sprocket on the diff. But I got there.

And that led to me being able to take what I will call the 700 hour photo.

Bam!

Oh damn.  That's sexy.
How confident are you that you got the diff and gear concentric?

Ill say it now: use a belt tensioner with a sprocket for the chain. Theres going to be a lot of slop, and hopefully itll keep it from throwing chains at your head. 

I'm currently not planning on having the center hole in the sprocket locate the sprocket on the diff. I still need to drill the bolt holes in the sprocket and my plan is to make them concentric. 

Also, it doesn't have to be perfect with a chain. As long as it is tight enough to not jump teeth, the non-tension side can soak up a bit of imperfection. 

I also, fortunately, do have this guy to use as a drill guide:

Found a piece of scrap plywood and used nails to firmly hold the sprocket in place. 

Measured carefully across, divided in half, then made some marks at the radius distance from a few different points. Sprockets are weird because there isn't really a good reference point anywhere on the outside edge, but I did the best I could.

Next I was able to use that center to center my ring gear, and then I used a transfer punch to mark the points.

702 hours.

Robbie (Forum Supporter) said:

Sprockets are weird because there isn't really a good reference point anywhere on the outside edge, but I did the best I could.

To be fair, you did have reference points you could use before you cut the center out...

You really need a 3D printer.  I can think of half a dozen solutions for that that would work with a printer.

Shop day!!

First drill and tap this aluminum spacer. Yay used motorcycle hardware!

Next up, harvest some tabs and a straight section from the used metal bin.

Zap zap

Next I took a long time (relatively) just standing and looking, trying to make a plan. I considered many options, but finally ended on KISS. 

Here's a couple pieces of scrap tube cleaned up and with a chunk cut in the end and a slight bend applied.

Hopefully you get the idea.

Then, it was finally time for me to get up the courage to drill my sprocket. I think it came out pretty darn good. Soon I'll be able to line up a chain and see how out of round it is. With the dial indicator, I measured about .020 max to min in the valleys, but 3/4 of the sprocket was basically the large dimension and then there is a "dip" of .020 in one quarter. 

Then I was able to take this photo!

This may end up actually working... +6 hours.

Nice work!

Another big day.

We started off relatively slowly by unbolting ball joints and cutting spring mounts off of some Miata front lower a arms.

I realized a few days ago that the old rear outer axle supports were actually a perfect fit on the Saturn hubs - 1.25 inch.

It's always better to be lucky than good is what my mom would say. So we cut them and mocked them up. I'm not sure I could have guessed exactly how lucky I was. 

The fit is incredible.

Since it all fit so well, we fired up the burninator. And burninated. That's a Saturn hub bolted to a red devil f500 axle support tube, welded to the bottom of a Miata front lower control arm. Because naturally.

Check out the penetration!

It was about here that a pizza arrived, and we ate.

Love it.  F'ing absolutely love it.

Next was assembly, and we could remove the wooden bucks holding everything in place. We have travel!

Wheels, tires, and just about a full rear suspension.

But WAIT, there's MORE!

We got the wood back out to hold up the diff so we could mock up the engine location. With the diff centered, we had a new problem with the chain being offset to the left of the engine. The existing frame prevents us from moving the engine far enough to the right. Solution? Use those cv axles for what they were made for.

After this the shop got busy. We all put our heads down on individual projects. Grinders, cutoff wheels, strip disks, drill press, etc all being rotated around by 3 builders each doing their own thing. Nocones was on spring mounts. Gumby was on rear engine mount. I was making front engine mounts. 

Ladies and gentlemen, and Bob, I present to you, four wheel independent suspension. Bask in its glow.

+27 hours

F'ing brilliant day!