S2's Build Thread


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Colin, titanium is a more expensive material, but the primary increase in price is the labor, especially if you have a lot of pie cuts. Each pie is cut on a horizontal bandsaw, cleaned up on a belt sander, deburred, brushed with a tube polisher, handled with gloves and carefully cleaned with acetone. Since the welding wasn't done in a chamber, Abe only does 10-12 dabs and then keeps the gas running until he's sure that everything has cooled. He spends more time cooling under gas than actually welding so the process is a lot more time consuming than stainless steel.

My small x-pipe probably has as many cuts as a simple set of headers and more welding when you consider that the OD is 3.5". Depending on how the routing goes, my guess is that I'll need 6-10x more pie cuts to integrate the mufflers. The point is if you're trying to figure out a budget, you really need to focus on the labor.

That part would be made in 4 pieces if it were done in Inconel, with each piece formed from sheet - probably just as time consuming. In fact all the F1 systems used to be made that way until Inconel tubing and specialist cnc bending became available.


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The Daily Engineering dry sump pan is a piece of art. Unlike most other dry sump pans that have a multitude of scavenge lines projecting from the sides, Daily CNCs those pathways into the pan which provides a much cleaner installation. However, this results in a single large scavenge line which requires a massive scavenge filter rather than a small filter or screen on each of the protruding lines. Daily recommends a -16 400 Series filter from Peterson Fluid Systems. It’s 2-1/2” in diameter, 9-3/4” long and the -16 hose and hose ends are huge with a large bend radius. All of this makes it difficult to package the filter between the engine and the oil reservoir.

The top and bottom halves of the oil reservoir can be independently clocked which is helpful when routing hoses. However, no matter what I tried, I was unable to get any flexible hose between the filter and the tank and I settled on a solution that utilized a 45-degree union fitting that attaches the filter directly to the reservoir. The issue with that approach is that there is no flex hose to isolate the filter from the reservoir and they will vibrate at different frequencies which will eventually cause the weld on the bung in the reservoir to crack.


Temporary “angle finding” jig

To solve that problem, I needed to fabricate a bracket to dampen filter vibrations. The challenge was that the filter and the 2”x 2” chassis tube were pointed in different directions with a compound angle between them. I purchased a panel-mount billet bracket from Peterson, but measurements and angle finding attempts between it and the chassis provided futile. I then hacked together the above “angle finding” jig with two pieces of scrap right-angle aluminum and a vibration-dampening sandwich mount. Since there is only one screw per connection it provides four axes with 360-degrees of rotation each of which was orthogonal to the adjacent axes.

Within a matter of seconds, I was able to get it perfectly aligned. Wow, that was easy! I tightened the screws to preserve the orientation and removed the bracket which made it easy to measure the angles on the bench. This allowed me to design a bracket. The single screw per connection was critical to the angle finder, but antithetical to the bracket’s purpose so it utilizes two screws per connection to prevent rotation.


The bracket was laser cut from 1/8” stainless steel because welding small aluminum parts isn’t fun and the parts were well under the $29 order minimum. I added a couple of other parts and was still under the minimum.


3D-printed prototype bracket (left), welded stainless steel bracket (middle) and billet Peterson bracket (right)


Bracket assembled and ready for installation


Filter and bracket installed

The next step is to run the -16 hose to the pump and weld a couple of gussets to the weld bung just to be safe.
Impressive work as usual. Are you printing your prototypes in PLA? Avoid ABS because it's harder to print and has some post-print shrinkage?


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I print everything in Onyx which is a proprietary filament composed of high-quality nylon and chopped carbon fiber strands. It's not cheap, but I've never had a problem with post-print shrinkage, warping, separation from the print table, etc. In the last 5 years I think I've had two misprints and I've probably level my print bed about once per year. I'm really happy with the Mark Forged printer.


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In a previous post the muffler assemblies were tacked together. The next step was to extend the tail subframe to support the muffler assemblies, bumper and diffuser (the latter two are still in the conceptual phase). The main subframe is fabricated from 1” OD 4130 and the new extensions are made from 1/2” OD 4130 which is difficult to bend with a manual tube bender. To facilitate prototyping, I purchased a coil of 1/2” aluminum tubing. It’s inexpensive, easy to straighten with the right tool, easy to cut, easy to bend and simple to recycle when done. Once the subframe extension was prototyped in aluminum it was replicated in 1/2” 4130 and welded to the 1” subframe.


Muffler assembly resting on 3D-printed supports sitting on top of a motorcycle jack

The next step was to figure out exactly where the mufflers would be positioned. I 3D printed two brackets to support the bottom of the muffler assembly and placed them on top of a motorcycle lift sitting on a cart with lockable wheels. Which, combined with the car lift, made it easy to position the muffler assembly exactly where we wanted it and quickly move it to tack something without worrying about dropping the assembly on the floor.

Vibration isolator (top left), titanium tab (top middle), 1/8” 4130 tabs (bottom left), 3D-printed muffler supports (right)

I opted to hang each muffler assembly via three vibration isolators. To accomplish that, I designed and laser cut three different 4130 tabs to weld to the 1/2” sub frame and three copies of a titanium tab for the muffler assembly. Note that in the pictures below many areas were just tack welded when the pictures were taken.



The next step is to replicate this on the right side.



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The fuel tank is well protected from an impact. However, it’s possible that a crack forms on one of the welds due to a collision or a from vibration fatigue. For this reason, it has always bothered me that the fuel tank is essentially in the cockpit. I considered a fuel cell, but they need to be replaced every five years and there are only two ways to remove one, both of which are onerous in street car with a finished interior:
  1. via the cockpit: If you have a tub, which I do, you need to remove the body, windshield, cage, interior, tub and fuel tank cover panel. That’s a lot of work, but the real issue is that the body requires a massive amount of attention to seal the footbox, side pods and firewall and all of that needs to be torn out and replaced. UGH!
  2. via the engine bay: This requires the engine, oil reservoir, surge tank, coolant swirl tank, firewall, etc. to be pulled which isn’t that bad in a race car which is specifically designed to efficiently pull the engine, but a lot of work for a painted street car. However, the mounting brackets that I welded to the top of the fuel tank would prevent it from sliding through the chassis rails and I would have needed to carefully mount the tank so that I didn’t need access to the interior to reach any bolts. Lastly, I had already installed a permanent fire wall between the tank and engine compartment. So, this approach wasn’t a viable option for me.
Then I had an idea which is always dangerous. I could cut a big hole in the bottom of the stock fuel tank and the monocoque’s floor so that I could install a bladder from the bottom of the car. This would allow me to address several things that I don’t like about the fuel tank:
  • E85 doesn’t like raw aluminum.
  • The 2” fill tube doesn’t have a flapper valve. If you roll the car, you’re relying on the flex tube and gas cap to contain the fuel, both of which are attached to the fiberglass body and could be easily torn off. If that were to happen, the opening is 28x larger than the -6 vent that everyone puts a roll over valve on.
  • The rollover valve should be located inside the fuel tank. Otherwise, it needs to be located in the engine compartment which increases the number of connections, takes up space and creates the potential for a leak if the line between the tank and the valve is damaged in a collision.
  • Significant modification is required to implement a fuel pickup system (e.g., HydraMat, corner pickups, sump with trap door, etc.).
  • If you have a tub, you need to tear the car apart (i.e., via one of two options listed above) to service the fuel-level sensor and I’m aware of many builders who have had them fail.
  • Doesn’t support an internal lift pump without modifications.
  • No foam to prevent a flame front from forming or reduce sloshing.
  • The NPT bungs should be ORBs.
The first step was to remove the “finished” low-pressure fuel system and fuel tank. In a previous post, I used dry ice to remove all of the sound deadener from the tank. I then cut the largest hole possible between the 2” x 2” welded to the monocoque’s floor.


Access hole cut into floor. The large size makes it as easy as possible to install the bladder.

After reinstalling the tank, I marked the location of the 2” x 2” chassis tubes on the bottom of the tank. I removed the tank, flipped it upside down on the bench, marked an access hole that left a small flange around the 2” x 2”s and the front and back of the tank, drilled the four corners with a 5/8” hole saw and cut the hole with a 4-1/2” cutoff wheel. There are two baffles in the tank, each with two weld beads on three different edges, which meant that I had to break a total six weld beads per baffle. I accomplished this by cutting the baffle into thirds so that each piece isolated the two beads on each edge. After which I wacked each piece with a hammer to rock it back and forth until the weld beads cracked. The baffle in the picture above was relatively easy to remove because it was in the hole that I had cut. The other baffle was a more difficult to remove because it was tucked inside the tank.


Rough opening cut, baffles still in place

I then clamped a piece of steel to act as a limiter while I ground the edge with a 4” 40-grit sanding disk. As you can see in the picture below, the right side is straight and smooth whereas the top and bottom edges haven’t been finished yet. Because I don’t trust my cutting skills, I left more material than needed which required a LOT of grinding.


Right edge finished, top and bottom edges will be finished next

I then removed the weld bungs for the fuel outlet, fuel return and vent because they protrude inside the tank and would hit the bladder. The easiest way to accomplish that was with a hole saw. Since the existing hole was much larger than the pilot bit, I fabricated drill guides by chucking up NPT plugs in the lathe and center drilling them. I had a similar issue when enlarging the fuel fill hole. In that case, I tack welded a temporary disk to act as a drill guide for the pilot bit (see picture below).


Temporary disk tack welded to act as a guide for the hole saw’s pilot bit

Once that was done, I removed the shift cable tube (I’m using paddle shifters) and the fuel-level sender flange after which I smoothed and deburred every edge in the tank. When I was done the shop was a mess and I had exerted significantly more effort than I had originally anticipated. If I had paid someone to do the work, it would have been much less expensive to have had a custom shell fabricated out of thinner aluminum. I took this approach because I had already mounted the tank and made perfectly aligned cutouts in the in the firewall not to mention that my labor is free.

I drew the tank with the desired fitting locations in CAD and worked with Hill at Agile Automotive to help me spec and order a fuel bladder that solves all of the aforementioned issues with the tank.


All connections are easily accessible via the access panel cut into the floor (the above picture was taken through that opening); fuel outlet (bottom left), motorsport electrical connector for the lift pump and fuel level gauge (middle), and fuel return (top right).


The foam, lift pump and fuel pickup rig is installed/removed through the oval access panel. This enables the fuel bladder to collapsed so that it can be installed/removed through the holes in the monocoque floor and the bottom of fuel tank.


The fuel fill has a flapper value to prevent a leak if the car is rolled. I need to modify my firewall to accomidate the flange and allow the retention clips to be rotated when installing or removing the bladder.


Stock fuel level sender flange has been removed. The new fuel level sender can be easily serviced when the bladder is removed.

The hose end that connects to the roll over valve doesn’t clear the fuel tank cover panel because they weren’t able to locate it directly against the back of the bladder because they needed to provide room for the internal flange. This moves the location forward into the sloped fuel cover panel. I’m on my third iteration of a solution… I’ll figure it out eventually.
The next steps are:
  • solve the roll over valve clearance issue
  • clean up the cut out in the floor
  • fabricate a support shelf for the bottom of the bladder
  • fabricate a close out panel for the bottom of the car
  • modify the firewall to accommodate the fuel fill flange
  • validate that the bladder can be removed and installed using only the two access panels
Such a smart rethink of the fuel tank. This truly should be part of the fuel cell option from Superlight. I would bet money that Superlight would sell a lot more fuel cells if this was offered from the start.
Hey Scott, my fuel bladder can be removed by taking out the seats and removing the large fuel cell cover. Perhaps your roll cage is what would keep you from going this route.


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It's hard for me to comprehend how much time and effort you spend thinking everything through
Del, my wife has made the same observation more than once LOL

a smart rethink of the fuel tank
Thanks Dusty.

my fuel bladder can be removed by taking out the seats and removing the large fuel cell cover. Perhaps your roll cage is what would keep you from going this route.
Mason, the issue is the tub. It provides a big step towards making the interior feel OEM and it indexes and supports the body. This is great up until the point that you want to remove it which requires the following to be removed; windshield, body, roof panel, and cage. At that point the stock fuel tank cover can be removed. To avoid that level of work, everything in the car will be able to be serviced without removing the tub.