Jesse OBrien

This is definitely behind the information you folks have been getting (video editing takes a lot longer than writing a post), but I'm still really excited to announce the video series of this build.

It's something that I'm considering more and more as I get further into the project. Ground clearance is (arguably) a bigger concern than CG for our hillclimbs ... but I really need to find the sweet spot between ground clearance, CG, and cockpit area. I'm really surprised by how much extra cockpit area is available after removing the bulky stock floor. The physical bottom of the car is really low. Yeah, it requires changing your frame of reference from the ground to the floor. Once you start thinking of everything as being relative to the floor, you can start moving the ground and roof around in isolation. It's a difficult concept to discuss clearly.

Update Time It's Saturday, so I don't have a 'big' update to announce. I think I've mentioned it before but in case I hadn't, we're recording a whole web series for this build, similar to what I did for the CRX. I've always enjoyed watching honest, well-produced video over reading build threads, and thought I'd give it a go. As I learned from the CRX build, it really requires a dedicated film crew (of at least 1 person). The level of quality I want really isn't possible if I'm trying to build and film at the same time. With that goal in mind, I spent the morning laying out the video capture gear and taking an inventory of what we use on a regular basis. This is the result. Yeah, I agree. This might be a bit silly. Anyway, with that out of the way Mike and I started off by finishing coping for the dash bar, which looks pretty solid now. After lunch, Mike took care of the sill bar coping and I took care of the bent door bars. They aren't quite ready to weld in, but we're making good progress. Unfortunately, we ran out of material for the remaining sill/rocker bar and the windshield bar (both are required to run Mt Washington). I'll have another 24' arriving Monday morning. Tomorrow, I think I want to set our sights on tackling the front suspension jig, since the 'core' of the cage structure is finally coming together. Also, after a whole lot of thinking about what you guys have said, I think I am going to move the floor up around 3-5cm. Right now, the bottom of everything is pretty much in-line with the bottom of the fenders, but it does make sense to have it tucked up a little bit.

A full day of work today, and it doesn't look like much progress. My friends Mike and Matty came out to help, and we wrapped up the rear body jig, then centered and leveled the body on the chassis. The A pillars weren't perfectly symmetrical, so they came out, received appropriate trimming, and went back in. We coped the dash bar, and bent up all the door bars. With the car on the rear body jig, we pulled the 2x4's that were supporting the middle of the car. A new horizontal support bar was welded in in front of the A pillars, and the existing horizontal support bar was removed. That free'd up enough room to test fit the seat, and it looks fantastic. I couldn't get any photos of it, but there's plenty of room all around in this thing. Finally, we took some measurements to ensure that everything that's tacked together so far will pass tech without any issues, and pressed on 'till midnight. Lots of tubing was cut today.

Finally, everything's aligned and tack welded into place. I spent most of the day fine-tuning fitment so it's symmetrical on both sides and so I have as much headroom as possible, but the results are worth it. All told, I bent 6 'not quite right' A pillars throughout this process, so roughly 40' of material that didn't make it onto the car. It'll all get used, as door bars or similar.

Hahaha that's one of my least favorite corners of our whole Makerspace. The floor is crap, one of the walls has loads of leaks, there's always a breeze going through that spot, and it desperately needs a few coats of paint. I didn't really plan to get anything done today, just clean up the shop a bit in preparation for the weekend. Man, was I wrong. I nailed the passenger side A pillar so nicely, I decided to make another driver's side replacement ... but twisted the wrong way, which resulted in another perfect passenger's side A pillar. Then I made one more driver's side, and went so far as to add a small bend on the back of it to get it to fit up with the main hoop just so. Tomorrow, I get to break out the welder, tack it together, and start in on reinforcements.

At this point, it isn't even energy. I'm just on autopilot. Leave work, and instinctively end up at the Makerspace doing the next thing on my to-do list.

Sorry, I'm miscommunicating what I'm planning. My seat will go where it needs to be for the driver to comfortably see over the dash and have as much headroom as possible. The 'floor' (covering the drivetrain/exhaust and giving the driver somewhere to put their feet) will be right under the seat base. That floor will be mounted to the rocker/sill tubes, and the underbody aero will be mounted to the bottom of that, where the stock floor would normally go. The weight of the chassis is all going as low as possible, without building lower than the stock floor. Essentially, the stock 'floor' will be replaced with the flat undertray, and the stock frame rail hang-down will be eliminated entirely (because the tube structure is above the flat undertray).

The plan is to have the 'floor' mount to the top of the round tube in the floor, and the aero undertray on the bottom of that same round tube. Hillclimbs really require some extra 'slop' in ground clearance. Spring rates generally need to be a bit softer as well, to accommodate the frost heaves and overall inconsistent surface condition. As a basis of comparison, a road race Miata would run something like 450lb/in springs. My hillclimb times stopped improving when I went over 225lb/in. I had 6" of ground clearance between the bottom of the rocker and the road surface, and still found myself scraping on certain hills. Boring Stuff For this, I hope to be around 20% lighter, so if I keep the same spring rates I should (rough theoretical math) have around 20% less compression, and can get away with being 20% lower. That would be around 4.75" ground clearance from the ground to the aero undertray. Assuming 1.75" tubing, that'll put my floor 6.5" off the ground, which happens to line up with where the bottom line of my fender is on the chassis table (assuming the table surface is ground-level). As a general rule of thumb, rallycross ride heights are pretty dead-on for US hillclimbs.

I'm planning to put the seat as low as necessary while still being able to see over the dashboard, to ensure that I have as much space in the cockpit as possible. The kevlar floor will go under the seat. I'm open to alternative opinions there. I'm skipping frame rails altogether, and going tube frame instead. I don't like the deformation characteristics of square/rectangular tube at all, and hillclimbs almost always end up with some sort of rock or tree intruding into the floor in an 'off-road excursion'. I was also planning to keep the seats as far inboard as possible, without having shoulder interference. The only downside I've seen from that is that ingress/egress gets more difficult, as you have to climb further to get over the door bars. I'm willing to make that sacrifice. I'm really curious as to why you want the floor higher. No obvious benefits come to mind, but it's entirely possible that I'm missing something critical here. Now is the time to ask questions.

To celebrate having registered, I spent the night re-mathing and re-bending the driver's apillar. Tomorrow is the passenger, and the weekend is coping and tacking, then adding rockers, windshield, and dash bar. So far, everything is 1.75" DOM. For my own future reference, this is 20" straight, then a 47 degree bend, followed by 24" straight, 13 degree twist on a 42 degree bend, then 24" straight (which will be trimmed and coped to fit the main hoop). I may add one more slight inward bend to meet up with the main hoop.

Today registration for the Mt Washington Hillclimb race opened (Climb to the Clouds 2017). This has been my life goal for the past three years, since I purchased this car. For those who aren't already familiar with it, Mt Washington is the closest hillclimb to my home (around two hours away). It's also twice as long as the longest hill we typically run (over 7 miles). It happens roughly once every three years, and is a pretty big deal overall. The last time it ran I crewed for a friend and one of my racing mentors, Jamie Melhuish. It was quite an experience. In addition to learning twice as much course, we only get four practice runs. Each of those runs is only half of the course, so the first time we stitch the whole hill together, it's the first timed run. There are two timed runs. This is where a rally-style codriver reading pace notes becomes a massive benefit, but I'll be doing it solo. That means watching a lot of footage from past events, and spending a few days driving up at street-legal speeds to ensure that I actually know the course. Right now, my registration is in, but that doesn't necessarily mean I've been invited to race. I would need to be selected from the list of applicants to be invited to race. In any event, the only way I can be ready for the event if I'm accepted is to continue as planned and assume I'll make it to the start line. To say I'm excited is a gross understatement, like saying that an atom is "rather small."

UPDATE TIME! Because it's Saturday, I have an update on the build! I think I've solidified most of the fender profile at this point. I'd say it looks pretty good, and is ready for some final touches and blending to the bumper. I don't really have a way to express how much math and thinking went into the cage so far, but here are the key points: 1. It's friction-fit. I didn't even need to tack it into place, it's so tight against the body. 2. It's symmetrical. ... and level within 5mm from any point to any other point 3. There are no visibility problems. The diagonal X is 16" lower than the roofline, so it won't interfere with my rear-view mirror. 4. It reclines 10 degrees. Originally I was planning on 15 degrees, as that would fit the lines of the body and rear quarter windows nicely, but FIA regulations require no more than 10 degrees. I'd like to keep my options open as to what racing I do in this car, so I'm going with the most stringent sanctioning body I know of.

Well, that didn't go very well. My body reinforcement is in the way of mocking up the seat. I'll have to add another reinforcement, then cut the existing reinforcement out. I wanted to do something though, so I finally mocked up the front bumper cover.

There are safety concerns with reclining the main hoop too far. The general 'rule of thumb' is 15 degrees back, from what I've seen. That sounds like the same position I'm looking at (relative to the dome light), and it clears the wheel wells perfectly. I'd like to retain the wheelwells, if only because they're handy for reference measurements. I also like having a 'hard stop' between where I expect the tire to travel, and where the cage structure lives. Right now, the main hoop basically rests on the wheel wells, and that's perfect. I love the screwdriver-spacer idea. That's a brilliant way to keep rattles down. I'm very concerned about head height. I'm shorter than you by a fair amount (5'6") and my floor is around 3" lower than the stock floor (and even more, if we're talking about stock seat rails), so I could pretty much place my helmet under the door-window opening. However, I need to place the helmet above 'see-over-dash' height, so I'm going to need to maximize the helmet space I have. In the past, I've added a 10-degree bend to A pillar bars just before they meet the main hoop. That tucks the A pillar bar up into the roof area, and buys me another 3" of headroom. You can see what I'm talking about in this photo:

I was hoping you'd weigh in on this. I can see a few problems with my current X brace design. One is that the X will be right in the rear-view-mirror space, and I'd much rather have it a little lower. The second is (as you mentioned) the seat placement, which I can't know until I test-fit the cockpit together. My hope is that having the main hoop reclined will give me plenty of room for everything, but I won't know for sure until I mock it up. Going from the 'standard' pickup point to the 'notch' in the ceiling seems to give me a lot more space for a seat. I don't plan to fix the body to the chassis structure completely, so I won't do final welds until I've tacked the whole chassis together. That means I don't have to do final welds on the top of the main hoop, because I can always pop the body off to do them again. More like a circle track car, where the body panels are just hung on the tube structure. It makes all of this testing a lot easier. I'll try to get the seat into a reasonable place tonight, and we'll just see how this all looks together.

Most of the weekend was checking and double-checking all of my math. The main hoop and diagonal braces are cut, and one is welded in. I think I'm going to make some minor adjustments to my A pillar design rather than making what I have mostly-work. This is the most critical point to get fitment spot-on for everything, since everything after this will be measured against these first 'core' pieces of tubing. A friend had a non-running ej205 (older 2.0liter Subaru WRX engine) taking up space in his shop, and I generally like having a spare engine on-hand in case something breaks on any of my engines. I just finished pulling the intake manifold off, and decided I'd compare that engine to the engine I'm putting in the Datsun. This is a complete valve-to-valve comparison of the two. If anyone is confused as to why I'd use a rotary in my Datsun, accept that simplicity and compactness are really the only reasons. Horizontally opposed engines are known for keeping their mass low and short (front-to-back). As you can see, the rotary pretty much wins in every direction here. I still need to weigh both packages to get a decent reference, but I can easily carry one but the other requires two sets of hands to haul around.

Today, my ego grew at least 6 sizes. Somehow, I managed to get extremely accurate measurements, and bent the main hoop and A pillars perfectly ... while the old cage was still in the car. I had planned on doing each of these three times before getting one combination that I could call acceptable. I couldn't have asked for them to come out better. I still need to do some coping and tack welding, but it's all coming together quite nicely.

Tonight I enlisted some help to get the body aligned on the chassis table. There wasn't quite enough time to finish the rear body jig, but overall it was a successful adventure. Within 0.5 degrees of being level with the chassis table.

More fender plug shaping happened today. It's really starting to take shape. Once I have the final profile formed the way I like, I'll cut some ribbing to make all four consistently shaped, and go to town with fiberglass. If I had to pick a car as inspiration for these, it'd probably be the Turner BMW M6. ] I also started forming and reinforcing the mold for the cowl. I never understood why there are louvers in the cowl, they only serve to collect pine needles and to let rain into the wiper motors. I decided to just smooth it all out, make a fiberglass mold, and reinforce that mold with 2lb urethane foam (to give it structural rigidity). I'll need a second set of hands to get it in place, but now the jigs are ready to hold the car level on the chassis table.

My weekend was spent cutting, welding, and filming. That is all.

Today was a bit slower than usual. I got a bunch of stuff done on the Subaru (winter wheels on, new belts all around, fresh plugs, etc) and picked up a few new tools. Then I headed back to the Makerspace for some fender forming. There's plenty more to do, but this is some basic blocking.

I spent most of the day welding together a body jig. I started with a simple horizontal alignment jig: ... then triangulated that toward the rear, and started to weld in the rear mounts, when I ran out of square tube. I have more in my garage, so I can still finish that tomorrow. Once that's finished, I'll be able to start test fitting the tube frame cockpit section, and align the suspension jigs I already started building. After that, I just weld it all together and discover what I did wrong. I'm really pleased with the little MIG welder we have at the Makerspace. After selling my Hobart to another hillclimber, I had forgotten how fast work goes with these, and how much easier certain jobs are. Finally, I went to ESS today (an electrical supply store) to help one of the Makerspace members pick up a sturdy welding bench, and they had some really burly casters that seem to be PERFECT for the chassis table. I won't be able to weld them in until the Datsun body is secured to the table, but I'm eager to get that done. I'll be able to wheel the whole thing over to the welding station and they're leveling feet all in one. For $75, I'm ecstatic with that deal.

Happy Birthday to me (no really, today happens to be my birthday). Cutting out such nice fabrication work hurts, but the project demands it. A little help from a few people, and I was left with most of a roll cage. If this were a single-seater, it'd be ideally set up. With a little reinforcement, the body is safely on the chassis table. I'll jig the body so it's roughly-ride-height up from the table surface, then finalize my suspension jigs to tie it all together.

One more unit of progress. Slow going, but I'm also prepping for the next 'major hurdle' as I have time.