Datsun Roadster: 2020 Challenge Build

Ok, build update time:

I've been knocking out the little stuff. Like replacing these rod ends.

Assembling the rear axle:

Reducing side to side slop in the shifter, running it through the gears on the stands, making sure the shifter is working well. It is.

Connecting up the brake light switch extension wires, planning out a wind deflector, etc.

Mounted the other 3 wheels and tires.

Also, I spent about 7 hours fixing the control arm that was had the rod end busted off in it.

Short version:

365 hours.

Looking great man!  Nearly there.

Knocked replace heims, change oil, and alignment off the list this morning.

Next up finalizing the windshield mounts and making a chain guard.

366 hours.

Ps, any other formula guys have alignment recommendations? I set it at zero toe and about 1 degree of negative camber on each side. I figure suspension won't move much and car shouldn't roll very far so I don't need a ton of camber.

In reply to Robbie (Forum Supporter) :

Depends on tires- we needed more camber on the FSAE cars with a 10" wheel and more sidewall vs a 13" with the same height tire, for example.

Running an Fmod here.

TONS of caster.  I think I have about 9* on mine and about 2 degrees of camber and only slightly toe out. 

The caster is because with the solid rear axle you want to unload the inside rear to prevent the non-differential from inducing understeer. 

Apexcarver said:

Running an Fmod here.

 

TONS of caster.  I think I have about 9* on mine and about 2 degrees of camber and only slightly toe out. 

 

The caster is because with the solid rear axle you want to unload the inside rear to prevent the non-differential from inducing understeer. 

+1 on the TONS of caster.

And with the "heavy" body on top, I'm guessing it will roll quite a bit, so I'd put more camber (3 degrees) and you might be able to set toe to zero.

I just measured caster at about 11.3 on one side and 12.1 on the other, so there is lots of caster already. 

I'm not sure how to adjust it though, short of grinding down the "axle" ends of the control arms and shimming them to move them forward and back.

Adjusting the camber would affect caster, although only slightly.

In reply to Robbie (Forum Supporter) :

That should be plenty of caster assuming you have a good amount of positive scrub radius. How much do you have? With the caster angle and scrub radius, you can estimate how much "jacking" of the inner rear wheel you'll get. 

Big. Weekend. 

Ian came into town this weekend to help get more hours under the f-dat belt. So big update here, I'll try to keep the words to a minimum. 

1st I spent about 2 hours making a chain guard. Start with 2x2 square tube. 

Cut out a C shaped section. 

Cut triangles (accidentally make them too large - a bit more foresight here would've been slightly better). 

Make a front bracket.

Weld the triangles that were cut out back in, after having bent the piece the right amount. 

Drill and tap a hold for the back, weld the front to the tab, boom, done. Note that I may need to slot the rear hole a bit if the chain stretches and I need to re-tension it. Oh well. 

Next we got on to adding the rear wing and muffler support. This is a super nice piece that came from the AMC spirit build and from behind a drag racer's shed before that. It is almost freaky how well it fits the F-DAT. Held it up in the right position with carefully placed bungies:

Then made the bottom attachment points. 

Next, mount the muffler to it. The below are BACK SEAT BRACKETS FROM THE SAAB UTE CHALLENGE CAR. Ian told me this is the kind of good luck you have when you are a packrat extraordinaire. I told him not to encourage me. The rubber isolators from various CBR brackets fit the bill perfectly in the large holes at the top of the saab brackets. 

Cutty cutty, drilly drilly, rivnutty rivnutty, better to be lucky than good is what my mom always says. Also, the angle of the exhaust means that hot and high energy exhaust gasses will be getting blown directly on the bottom of the wing. Excellent!

While I was working on the wing and exhaust mounts. Ian was busy with stuff like mounting the windshield, making a bracket that prevents chafing on the radiator hose, wiring the clutch switch, and doing a nut and bolt job on the entire car. 

I handed him a sharpie and asked him to mark every fastener with it's size. This is a racecar after all, and any time we can save on serviceability is good time in my mind. 

Ian even was kind enough to spent time to get those brake hoses perfectly zip tied back. 

With that, we bolted on the wheels and rolled it outside for it's maiden (sans body) voyage. Nose cone was quickly added for reasons that will soon become apparent.  

I drove once around the block, and then Ian took a turn. We didn't wind it out as I happen to like that my neighbors don't ask any questions about what I do in my shop. Here are some things we learned from the first outing:

1. Parking lot turning (radius and solid rear axle) are not a strength
2. The shifter wasn't tightened appropriately - Ian asked me to do it like 4 times while doing the nut and bolting and I never did it 
3. It sounds awesome!
4. Brakes work
5. Launching from a standstill is very easy in 1st, easy in 2nd, and quite possible in 3rd. Really not an issue. Throttle pedal works brilliantly. Clutch lever just like the bike. Ian has never even ridden a motorcycle and had no issues. 
6. The sprocket can shift a little bit on the axle - eeeeeesh
7. Cannot. wipe. smile. from. my. face.

Between Ian and I we added about 25 hours of work on Saturday. But we had a running and driving car.  391 hours!

Ooooh I can't wait to hear where that wing tree came from!

I like how you wrote the wrench sizes next to all the bolts.  Looks like you've got quite a mix of sizes there too.

Twas ditched last year off the AMC, but we thought best to keep (you know, just in case...).

When we did the traction bars/rear axle mounting strategy on the AMC, we no longer needed the tree.  But its an insanely nice piece, so we kept for future projects.

That moment finally came to fruition!  It was literally meant for this, and mounts the exhaust so nicely.  Robbie outdid himself on that features design and execution.  I'll let him comment more on the other benefits of the design since its his baby.

The exhaust going between the wing supports is just perfection.

Yeah, tight turns without enough throttle to dance the rear are no good. Its a commonality on Fmods. 

Photo dump from Ian's phone.

Almost there, so close we can taste it.

Like a proud papa bear standing with his creation.  About to set it down from jack stands for the first time (well, we had to weigh it first!  But Robbie gets to spill those beans.)

Oh my goodness!  It is on the ground, rolls even! (post weighing, again, Robbie's discretion and thunder, not mine)

Wow, looks good outside, about to hopefully NOT go to jail!

MAIDEN VOYAGE A SUCCESS!  HOLY SH*T IT RUNS AND DRIVES!

https://youtu.be/2xH76TJmfbY

So, what do you do with a freshly completed racecar on a Sunday when you have a good friend and a rental trailer handy?

Why, you go racing of course!

Ian and I loaded up the F-DAT in the rain and dark late Saturday night so we wouldn't have to do it in the AM. Sunday morning we headed 1.5 hours due south for Rantoul AFB. Bullet point list of mention-worthy things to follow:

• The car is violently fast. Formula car autox is a totally different experience from street car autox. 
• Nothing significant broke (this might have made me the happiest). 
• Car fuel starves even when tank is about half full. Need to keep the tiny 1 gallon tank topped up. 
• Lost a cotter pin and one point and pedal assembly tried to remove itself from the car. Scary, but easy fix. Replaced cotter pin with paper clip wire stolen from my FIL's center console.
• Shifter came loose multiple times. Probably need a better solution. Once adjusted correctly and tight it worked great however. 
• Car sticks like glue until it doesn't. And when it doesn't the spin happens fast. See bullet point #1. 
• The engine is one pissed-off little unit. Very happy with the choice. 
• Surface was cold. Not sure we ever got above 60 degrees during the day. When we went back to back runs the extra heat in the tires was noticeably improving grip. Gainesville (and adding weight from a body) should be better. 
• Surface was very bumpy. This was an old AFB surface in front of a hangar. Basically 10x10 squares of concrete as far as you can see. Pretty old and beat up too. Lack of suspension travel was absolutely an issue. 
• Surface was wet in the morning. With our tires this was a problem. We thought about aiming for the middle and trying to cross straight like you would a jump during the course walk. While driving we found there is no time for things such as 'thinking' and 'aiming'. 
• Once adjusted appropriately and correctly tightened, the shifter works great.
• When you spin out, corner workers can hear you yell BERK
• The car is violently fast. We ran with 17 psi in all 4 tires. 

Officially 5th fastest time of the day on the first event. But unofficially, Ian scored a 52.8 that was DNFd becase he skipped a gate to dodge a corner worker. The gate wasn't critical to the racing line so he likely would've been faster if not for letting off to give the worker space. He definitely should have been red flagged and given a re-run, but it was as end of day, we were tired, course workers were tired, and we weren't there to win. We were incredibly happy with the car completing all 19 runs in such stellar fashion. 

Pretty sure that other SS Porsche was a GT3 911. 

I'm so stoked with the performance so far. Now I've got 2 weeks to attach the body...

So rad. Can't wait to see the body dropped on. 

In for weight below AM minimum

No GoPro footage, but here's maiden voyage on Robbie's first or second run.

https://youtu.be/pM1KpZAnN7k

Here's a photo from some of the great folks at Champaign County Sports Car Club. Probably the most welcoming autox event I've ever been to. 

https://HoemannPerronePhoto.zenfolio.com/p720698128/eeeaa3e53

In reply to Robbie (Forum Supporter) :

Here's a good one as well!

This, I like

Well done!

Fantastic.  I was out of town otherwise I was planning to be at the event Sunday.  Glad it's going well.  I am busy next weekend but if you need a thrash the weekend of the 17th I could probably adventure up to your place.

Looks awesome!  Congrats on the successful shakedown!