Tow Hook

And most recently abrasive…

I cut the the front tow hook out of 1/4” cold rolled steel. At two hours and 42 minutes it was by far the longest cut that I have done. I was a bit nervous about having an issue in the middle of the cut which would waste a lot of abrasive not to mention the material.

I had an issue during a previous cut in which the Wazer stopped cutting all of the way through a piece of 1/8” stainless steel. When this happens the water jet and abrasive bonces off the material in the direction opposite to the cutting head’s motion. Unfortunately the seam between the lid and the sides is not well sealed and some water and abrasive will escape. If you don’t catch this right away you’ll have a bit of a mess to clean up. While the mess is manageable, water will drip down the side and into the abrasive hopper which wrecks it. I scooped all of the wet abrasive out using a specialized tool… I know that it looks like a serving utensil, but I would never use a kitchen implement in the garage;-)

The bounce back when piercing doesn’t case any issues. I assume this is because it bounces back vertically into the cutting head.

After running a test I determined that the abrasive flow rate was too low so I emptied all of the abrasive and used compressed air to ensure the abrasive feed tube was clear. After than everything worked fine. As can be seen in a picture below, the cut quality was outstanding. The cut consumed a whopping 53.4 pounds of abrasive. While that seems completely uneconomical, that’s $76.89 if you purchase by the bucket and only $24.03 if you purchase by the palette. Even the higher bucket price is about half of the minimum cut fee around here.

A couple of takeaways:

  • Per the Wazer manual, stay in the same room as the Wazer when cutting. When the water jet is bouncing off of the material is makes a different sound which will alert you to look at it. Unfortunately, the piercing operation sounds the same so you need to look at the LCD panel to determine it’s piercing or cutting. If it’s cutting you have an issue

  • Wazer should have designed a channel into the top of the abrasive hopper so that water dripping down the side doesn’t contaminate the abrasive.

  • Wazer needs to add a feature that allows a cut to be restarted at a given place. If this cut had failed like the prior one did, it would have wasted over $100 of material and abrasive.




Pressure Regulator

I converted the fuel rails from a deadhead-return-style to a flow-through-return-style configuration to better support my power levels. While doing this I replaced all of the barbed fittings with AN fittings. Most SL-C builders mount the pressure regulator to the firewall or chassis, but I decided to mount it between the fuel rails on the supercharger. This results in less hose and I think it looks cool because it fills in an otherwise empty space which is visible in the rear window. That said, it was a lot more work than mounting it to one of the standard locations with the provided bracket.

The primary challenge was figuring out how to securely mount the regulator so that I could use hard fuel lines. There are two casting holes in the intercooler which I tapped for 1/4”-20. I then used 1/8” aluminum to fabricate the mounting plate which provided an opportunity to use my dimple dies. Yeah, I know they’re more commonly seen, and often overdone, on hot rods, but I think they’re cool. Both the aluminum monocoque and the dimple die originated in the aviation industry, so they aren’t out of place. Abe did a nice job welding it together.

Self-adhesive 1/4” rubber was used to pad the plate above the cast boss for the vacuum reference port and to help dampen vibrations. This finalized the height of the plate and two aluminum spacers were turned on the lathe to fit between the holes tapped into the intercooler and the plate. The two extensions at the back of the plate are wedged under the supercharger and are intended to help keep the plate in place.

Abe had two pressure regulators from Fore Innovations; a F1i which is two tone (raw aluminum and black) and a F2i which is all black. I prefer the appearance of the former, but the latter has superior internals, specifically a ceramic/stainless valve and a fluoropolymer coated spring. After confirming with the manufacturer, we swapped the internals.

Fuel pressure gauges are bulky. This normally isn’t an issue, but mine is on display in the window so I spent several late nights looking for a thinner one (see comparison picture below).

I wasn’t able to remove the 1/4” NPT plug from the vacuum reference port. Worrying about stripping something in an important part is one of the most stressful parts of building a car… and the supercharger is both important and expensive. I tried using a hex-bit socket and a 3/8” impact gun to no avail. I then made a simple heat shield (a hole in scrap aluminum) to protect the paint, heated the plug with a torch and tried again to no avail. If it was going to strip, I wanted Abe to be vested so I let him deal with it ;-) He heated and wailed on it with the 3/8” gun and it didn’t budge. The last attempt before pulling the super charger off and drilling it was more heat and a 1/2” impact gun. Fortunately, that worked! I replaced the plug with a stainless steel barbed fitting.

The fuel lines were fabricated out of aluminum. I’m going to look for a thinner vacuum line, but this part of the car is done until final fit up. The next step is to install the surge tank, high-pressure pump, E85 sensor and fuel filter between the fuel rails and the low-pressure fuel system.

Front Sway Bar Drop Link Redo

In a previous post I replaced the front sway bar that was mounted to the top of the monocoque with one that’s mounted to the nose tube structure. Although the drop links are a lot shorter, they connect to the lower control arm in the same location. However, I replaced the stock clevis with a custom chromoly bracket. The clevis was mounted with a single bolt that focused the drop link’s forces between the shock mounting pin and the chassis. The bracket distributes these forces outbound towards the hub. It is mounted with two bolts; one closer to the shock mounting pin and the other between the pin and the hub.

The pockets machined into the control arm are great to look at, but they’re a real pain in the ass when you want to mount something because you need to be careful where the holes are located. In particular, you need to avoid the chamfer unless you’re going to machine the hole on a mill. As shown in the picture below 3/8” holes were drilled into the pockets that straddle the shock mounting pin. I fabricated a 1/4” aluminum spacer to pad the bracket above the shock mounting pin (the notch shows where the interfere is). On the underside there is no room in the pocket for a bolt head, let alone a washer, so I fabricated plates out of 1/8” chromoly to span the pockets.

Intercooler Swirl Pot and Oil Filter

Custom swirl pot for the intercoolers

Custom swirl pot for the intercoolers

The intercooler system needs a reservoir, a way to add coolant and a way to bleed air. I decided to combine all three into a swirl pot. A swirl pot de-aerates coolant by swirling it around the inside of the pot as it flows from top to bottom, allowing air bubbles to break up and rise to the air pocket under the cap. The swirling action is created by aligning the inlet and outlet to be tangential to the inside diameter of the pot (if you look at the swirl pot above you will see that the fluid will swirl in a clockwise direction). The system is filled until the swirl pot is about 2/3 full to ensure adequate space for the coolant to de-aerate, while also providing a sufficient volume of coolant in the swirl pot to prevent pump cavitation.

It was a fair amount of work to fabricate the parts and a lot of welding!

While I’m going to hide the stuff I don’t like (e.g. electrical, coil packs, etc.), I want the cool parts of the key systems to be visible. With that in mind I located my super trick oil filter mount to be symmetric with the swirl pot in the rear window. This location accommodates a 5” tall filter element and enables me to easily check for debris through the view port.

viewport.png

I’m looking for a weld on sight glass like the one shown here for the swirl pot. If you know where to get one, let me know.

Nose Box 1.2

The tube frame around the nose box is almost done. As you can see in the picture below diagonal tubes were added to mount the sway bar, four 1/8”-thick tabs were added to each side to mount the vertical aluminum panels, tube gussets were installed where the top tubes meet the monocoque and a 1/8” plate gusset was was added to the tow hook bracket. The next step is to add two tube that connect sides; one on the floor behind the radiator and one at the top near the monocoque and four gussets to reinforce the bar that crosses in front of the radiator.

The sway bar’s pillow blocks are mounted to 3/16” steel plates supported by three 1/8” gussets. The Wazer was really useful cutting out the gussets. They’re small and would have been a pain to make by hand. The center gussets are 3/32” shorter than than the end gussets. As you can see if the pictures below, the pre-welding fitment was perfect — just like all of my tube notches LOL. The tube collar’s OD was taller than the pillow block’s offset and they were biding on the steel mounting plate. A 1/8” thick aluminum spacer solved that issue.

Nose Box 1.1 and Oil Filler

The SL-C’s aluminum semi-monocoque chassis is a work of art, but the nose support structure is an after thought. There are two vertical 0.19” aluminum supports, each bolted to the chassis with two 1/4” bolts which are vertically separated by only 2”. It works, but it allows the nose to move around more than one would want and it would absorb very little energy before before a front impact reached the monocoque.

Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.

— Jeremy Clarkson

That’s why modern cars have crumple zones to absorb the energy from an impact during a collision by controlled deformation. While I’m not capable of designing and building an engineered crumple zone, I’m going to build a tube structure which will absorb some energy before the the stout monocoque is reached. I have the following objectives:

  • Stiffen the nose and splitter

  • Absorb some energy in a collision without being too stiff

  • Provide a towing/recovery point at the front of the car

  • Provide a solid mounting plate for the nose hinge

  • Isolate the radiator which is wedged between the support verticals which move around

  • Provide additional support for the intercooler’s two heat exchangers mounted on the splitter

The first challenge was that the floor of the nose was sloped down towards the front-left side because the bottom of the extended foot box was not properly fixed when it was welded. As can be seen in the picture below the footbox extension is pushing the floor down. This required a massive amount of grinding (see the green arrow pointing to the black sharpie line), but I was able to get it to a good place without causing a structural problem.

Each side of tube structure will be mounted to the nose box via two 3/16” steel plates, each with four 1/4” bolts. This results in 4x the bolts and slightly more than 4x the vertical separation between the top and bottom mounting points vs. the stock solution. The top plates ties into the 1/2” upper-control-arm bolts and the lower plate wraps around the corner of the chassis. To create the bend in the lower plate, we clamped the plate and a steel rod which matched the radius on the corner of the monocoque in a vice. We didn’t have an acetylene torch, so we heated the metal with a propane torch. This took a while and the metal never got red. We bent the metal about 30 degrees and noticed that the bend was occurring above the steel rod (i.e., higher than desired). We opened the vice, dropped the hot rod on the floor and re-positioned the bend where it should have been with respect to the steel rod and bent it to ninety degrees… basically a game of hot potato with profanity. The result was a near perfect bend.

The first picture shows the top plate and a modified version of the vertical support mounted on top of the bottom plate. We cut 3/16” off the back of the vertical support to account for the thickness of the lower plate and welded it back together. This allowed us to use the vertical support as a surface on which to mock the tube structure. The stock solution is just the two 1/4” bolts spread 2” apart on the lower plate.

The frame will be made from 1” x 0.095” chrome molly tube. I choose 1” tubing for two reasons; I didn’t want the tube structure to absorb too much energy before crushing (I hope) and there is only about 1” between the vertical support and the radius on the monocoque and I wanted the tube to T-bone the chassis on a flat surface. The picture below shows a mockup of the bend angles using pieces of DOM tubing. The side tube will be made in two pieces.

After bending the side tubes we machined slugs out of 1” solid stock. I learned about the importance of drilling a small hole (i.e. 1/16”) so that hot air can escape the tube while welding. In this case I drilled the holes in the mounting plates. I also learned a way to quickly dress up the chrome molly tube. The side tubes are fully welded and tacked to the mounting plates. The tube that crosses in front of the radiator will be 0.095” chrome molly. I now need to decide if I should use 1” or 1-1/4”. I will mount a towing point to the center of the cross bar so strength is important. The 1” tube can be bent and coped into the side supports and it will look at lot better. The only question is, “is it strong enough?”

After bending the side tubes we machined slugs out of 1” solid stock. I learned about the importance of drilling a small hole (i.e. 1/16”) so that hot air can escape the tube while welding. In this case I drilled the holes in the mounting plates. I also learned a way to quickly dress up the chrome molly tube. The side tubes are fully welded and tacked to the mounting plates. The tube that crosses in front of the radiator will be 0.095” chrome molly. I now need to decide if I should use 1” or 1-1/4”. I will mount a towing point to the center of the cross bar so strength is important. The 1” tube can be bent and coped into the side supports and it will look at lot better. The only question is, “is it strong enough?”

"Beer Holder" Enigma Solved

The SL-C has two large recesses in the body which are covered when the tail is closed. Lots’s of builders, myself included, ask their purpose. A common response is that they’re for holding a beers. While they’re perfect for that, they’re typically used to hold stuff when working in the engine compartment before the car is painted. Once the car is functional they become unwanted water reservoirs and are usually drilled.

They were originally a place to mount the body to the chassis. The chassis changed, but it wasn’t economical to change the body mold.

In any event, to make room for the cold air induction box located next to the rear vent, I had to mount my oil reservoir near the firewall which would require me to use a long funnel to fill it. What to do?… fabricate a remote oil filler and locate it in the beer holder.

I bought a billet screw-on cap and a -12 AN weld bung. I then used the Wazer to cut an aluminum weld plate, a cork spacer and a carbon fiber trim ring. The spacer was used to pad the cap down so that it was below the surface of the body. Everything was welded on the inside diameter. Welding the outside diameter would have been easier, but I didn’t want oil to get trapped between the weld plate and the weld bung or cap body. The weld bung is offset to make it easier to run a hose from the filler to the tank. The cap fits perfectly inside of the beer holder (i.e., my fingers easily fit between the body and the cap), but I need to increase the OD of the carbon fiber ring to better fill the space and counter sink the flat-head screws. The next step is to modify the top of the oil reservoir, connect it to the filler with some hose and laser etch the cap.

Nose Hinge Group Buy

First batch of 15 hinge sets

Bob and I offered our nose hinge to the SL-C community in what’s know as a “group buy” and so far we have 25 orders. The picture shows the first batch of 15 sets of hinges. That’s 210 billet parts, 75 laser-cut parts and 870 miscellaneous parts.

We made a couple of design improvements. Most notably, we improved the aesthetics of the ball bearing. In the first iteration we used a nyloc to hold the shoulder bolt in place. In the second iteration we added a washer to hide the ball bearing and then machined a longer shoulder bolt to the perfect length and then tapped it for a button-head screw. The result is a completely streamlined appearance. Version one is priced at $700 and version two is priced at $730.

Transaxle Adapter Plate Mounting Brackets

I was having some fitment issues with the shift cable bracket which led me to notice that the engine was sloped three degrees upwards towards the back. The LS7, transaxle adapter plate and brackets were installed by Superlite, so I never paid much attention. The only way to remove the bracket / adapter plate bolts was with a 1/2" impact gun. All of the plating was stripped off of the grade 8 bolts, aluminum speckles fell on the floor, the holes were "threaded" at an angle and the nice chamfered edges were torn and jagged. Even when the bracket is removed the bolt won't slide through. In fact, I needed to use a socket wrench because it was too tight to spin by hand... I guess there's a reason a tap has channels to evacuate chips when threading a hole. Here's what the hole looks like after removing the factory-installed bolt.

What happens to perfectly machined clearance hole when an impact gun forces a bolt in at an angle

Clearly the engine was installed with the wrong brackets. My plan was to fabricate new brackets, but then I got to thinking… The Ford GT drivetrain has only three mounting points, two for the engine and one for the transaxle and it's my understanding that this is a very common approach for mid-engine cars. Since the rear suspension cross brace provides a rigid location to mount the transaxle, it makes sense to remove the brackets causing the issue. This has the following benefits:

  • The three hard mounting points can be replaced with polyurethane mounts to reduce vibrations.

  • The exhaust is easier to construct because you no longer need to do a 180-degree bend to clear the bracket. Remove the 180 will only improve flow.

There is some debate as to weather the brackets are intended to create a stressed member. To be safe, I’ll fabricate a 1” x 2” chrome molly tube flush with the bottom of the chassis to tie the two vertical billet pieces together. I also plan to machine the two mounting ears off of the adapter plate to increase room for the exhaust.

The next step is figure out how to build the engine and transaxle mounts.

Fuel Filler

Superlite provides a nice Sparco fuel filler cover. However, because I added a supercharger, the fuel funnel was t-boning the induction tube and the throttle body. Most SL-C builders simply clamp a flex hose to the fuel funnel and run it on the engine side of the 2” x 2” chassis tube, but the only way to make it work in my situation was to modify the funnel which is made of thin, spun aluminum. It’s a good thing that Abe can do that type of welding in his sleep, because I would have burned right through it. The steps were as follows:

  • Cut the filler neck (see red “X” in picture below).

  • Weld a piece of aluminum to close the opening.

  • Drill a 2” hole in the bottom corner (a funky angle).

  • Weld the 2” tube into the outside and the inside of the hole.

  • Add a bead to help hold the flex tube in place.

I’m very happy with how it worked out. It easily clears the chassis and I think it will actually work better than the standard approach because the fuel stream is pointed down into the tank rather than into a 90-degree bend. In addition, the fuel tank inlet has a 2” diameter and the funnel has a wider (I believe 2-1/4” ) diameter. The discrepancy is typically solved by the use of an adapter and a set of clamps. By using a 2” tube I didn’t need the adapter or clamps.

Wazer

The Wazer is the world’s first desktop water jet. I’ve been watching them since their Kickstarter campaign in 2016. I placed a preorder so long ago I forgot when, but after many delays it finally arrived. It has a cutting area of 12" x 18" (305 mm x 460 mm) and can cut a wide range of materials including (larger list here);

  • 1/16” 6061 aluminum at 3 in/min

  • 1/2” 6061 aluminum at 0.5 in/min

  • 1/8” carbon fiber at 1.3 in/min

  • .016” Neoprene, 50A at 74.8 in / min

  • 1/8” steel 1008 at 0.9 in/min

It’s delivered on a 500-pound crate which includes two 55-pound buckets of garnet abrasive. Everything from the packaging to the documentation to the equipment seems top notch. You definitely need two people to set the things up because both the cutter and pump each weigh over a hundred pounds. I won’t do an unboxing video because there is one here.

The machine comes with a rectangular piece of 0.1” aluminum mounted to the cutting table and a test file for a WAZER-engraved bottle opener. The result was a perfect cut and a great out-of the-box experience.

First car Part

The first usable part that I cut was a spacer for the upgraded front QA1 ball joints. This didn’t go as well. As can seen in the picture on the left, the top surface was cut very cleanly. However, the picture on the right shows the bottom surface of which only a small fraction of the cut penetrated full depth resulting in the entire piece being junk. Of the 12 pierce operations, only 5 went all of the way through. This is disappointing because 1/4” 6061 aluminum is extremely common and one would think that they would have that configuration working out of the box. The aluminum was from McMaster with a +/- 0.008 tolerance so it’s high-quality new stock. I mic’d it just to be sure and it was well within tolerance.

I should have cut a small test piece before going for the whole part. Fortunately, there is an easy was to change the cutting parameters. The Cutting Speed is set separately for the three different cut qualities: Rough, Medium and Fine. As quality increases, so does time and abrasive consumption. Here are the default / my settings for the parameters:

  • Fine Cutting Speed (in/min): 0.701 / 0.680

  • Pierce Time (sec): 79 / 81

  • Lead In/Out: (in) 0.038 / 0.038

  • Tab Width: (in) 0.017 / 0.02

The resulting cut quality was excellent and I was very happy with the part. That said it took one 67 minutes to cut and consumed a whopping 22.1 lbs of abrasive… a commercial water jet it is not! If you look at the table you will see that the cost of abrasive is heavily impacted by how you purchase it. On a per-pound basis, a pallet costs 69% less if you ship it to a residential address and 72% less if you ship it to a commercial address (lift gate service is provided in both scenarios).

These costs don’t include electric or water consumption. In addition, the cut bed is made of plastic and is a consumable item. It’s 4” thick and can be flipped so you get two sides. The machine comes with two cutting tables and replacements cost $79. Durability will be highly dependent on what’s cut and how much care is taken to spread the cuts around. Time will tell.

At the 87% completion point, cutting was stopped and I was prompted to refill the abrasive hopper and the empty the used abrasive buckets. I restarted the cut and about a minute later cutting stopped again and I was prompted to clean the drain filters. In all three cases there was plenty of capacity to complete the part, but since they don’t have sensors for these items I assume that these are just a conservative settings.

Second car Part

I then made gaskets for the adapters that are used when swapping the stock LS7 mechanical pump for an electric one. This demonstrates the diversity of a water jet, changing from 1/4” aluminum to a thin gasket without the need to change any tooling. The gasket was cut in 41 seconds which is half as long as a single pierce for the 1/4” aluminum which made it a lot more entertaining to watch.

IMG_6143.jpg

Wazer vs. Commercial WATER JET

Will (a.k.a. “pnut” on the forum) designed a spacer two years ago and he had it cut by a local water jet shop. After a lot of back and forth he was able to 12 pieces for $255 or $21.25 per part. Will’s part is on the left and mine is one the right. Will may weld better than me, but my CAD skills are better! Will contracted for a middle-of-the-road cut quality and I cut mine at the highest quality. If you compare the cut edges in the the second picture you will note that Wazer is capable of nice cuts.

The quote that Will received was divided into nearly equal thirds; project management, CAM configuration and cutting time. So, a quantity of two would have have had a unit cost of around a $100. The high cost at low-volume is due to paying someone to manage the process and a minimum cut fee. Basically 12 cost the same as two. For this part, beyond 12 is where a commercial supplier becomes cost effective.

To compare costs on a apple-to-apple basis I removed the the six lightening slots from my design which reduced the Wazer’s cut time to 40 minutes and 13.1 pounds of abrasive. The following table provides several price comparisons.

Low-volume price advantage aside the real advantage is cycle time. Will had to make several phone calls and send several emails. There was at least one delay and end-to-end it took several weeks to get his parts. If he had made a mistake it would have taken him a week or two for the next iteration. With the Wazer you can design the part and cut a prototype in thin plastic in a few minutes and quickly iterate until,you get it right at which point you cut the final part.

Nose Hinge

Prototype nose hinge mounted to Bob’s car

Prototype nose hinge mounted to Bob’s car

The SL-C’s nose is designed to lift off as a single piece. This works great for a race car because there are always crew members around to help you lift it off and you’re not worried about chipping the paint. However, if your crew is composed of your wife and kids, they’re not always available nor happy to be dragged to the garage when watching a movie or sleeping – yeah, last time I woke someone up to help move the nose it didn’t go well. Even with willing familial assistance you have to disconnect the wiring harness, make room to store the nose and you need to be careful not to scratch the paint.

What’s needed is a nose hinge. The primary challenge with designing the hinge is that the splitter, as is appropriate for a performance car, projects in front of the body work. Since the nose pivots forward its leading edge will bind on the splitter unless the pivot point is low and in front of the bottom edge of the nose. There are three general approaches that have successfully been used on SL-Cs, each with pros and cons.

Compound Hinge

A compound hinge raises the nose before allowing it to pivot forward. While there are many nice billet aftermarket versions available, they are generally designed for hoods which are lighter and they likely don’t have optimal geometry. Pros: Least visible when the nose is closed; may have integral gas spring; retains the splitter support rods. Cons: The motion isn’t as smooth as a single pivot point; the nose is wobblier when open; separate pull pins are required to lock the nose in place; and the nose may chafe on the splitter.

Forward Pivot Point

By placing the pivot point in front of the body it clears the splitter. Pros: Smooth motion, retains the splitter support rods; pull pins not required, easiest option to remove the nose (the bolts are outside the body!). Cons: Most visible (it protrudes in front of the nose); nose may chafe on the splitter; most difficult to implement (with a kit, it’s the easiest) .

Recessed Pivot Point with Rotating Splitter

The nose is attached to the diffuser and the pivot point is placed inside of the body. Pros: Smooth motion, splitter is strengthened, nose won’t chafe on splitter. Cons: All splitter and nose forces are supported by two pivot points mounted in fiberglass, the splitter support rods are removed (Fran doesn’t recommenced doing this for car that will see high speeds), heat exchangers can’t be mounted to the diffuser, more difficult to implement brake duct hoses.

Approach

I decided to go with the Forward Pivot Point approach because it offers smooth motion and allows me to mount the supercharger’s heat exchangers on the splitter. While noodling on the on the problem I discovered that Bob, another SL-C builder, had built a working prototype. The following video demonstrates how easy the nose is to open when gas struts are installed.

Bob shipped the prototypes to me and I tweaked and redrew them in SolidWorks. I then sent them to Allan and he installed them on a SL-C that he’s building (see picutres below). Based on Allan’s feedback, I relocated a few of the mounting holes.

The following video shows the updated CAD model. The plan is to do a group buy. The two largest pieces have left/right mirrors, so they take twice as long to achieve volume pricing as the other pieces. The target is to have a minimum order of at least ten hinge sets. Here are the top-level features:

  • Billet 6061 aluminum

  • Arms are 3/8” thick

  • All hardware, other than gas struts, is supplied

  • Stainless Steel mounting hardware from McMaster

  • Steel ball bearings from McMaster

  • Steel drilling jig

Depending on the shipping costs, we may or may not provide the gas springs.

We’re currently looking for someone to machine it!


Happy New Years!

I guess I should share a couple of resolutions. First and foremost I’m going to lose a lot of weight. In addition to health benefits, I’d need the world’s largest shoe horn to squeeze me into the car and even then NFW would I’d fit into the Tillet B5 seats. I’m also pushing to fire up the engine this year. That’s a lot of weight and a lot of work from where I am today!

The next step was to bench test the parking brake. Wiring it was trivial. You simply power it on a 10-amp circuit and plug in the ECU, calipers and switch. The results were anti climatic to say the least. As you can see in the video below, I hold the button for the requisite two seconds and the motors whirl and quickly stop. The LED on the button indicates that the brake is set, but it's clear that the brake pad is nowhere near the caliper. In fact it has moved less than 0.5 mm. Holding the button causes motors to return the calipers to their open position and the LED goes out indicating that parking brake is no longer set.

I’ve learned this lesson before… test everything as soon as you get it, because it often doesn’t work and if you discover this when you really need it, you’re going to lose a lot of time. So, back to England it went and it’s been help up in customs for 11 days.

So, on to the cooling system. To mount the 1-1/2” stainless steel cooling tubes I ordered some 1-3/4” billet clamps and lined their ID with 1/8” self-adhesive rubber to reduce conductive heat transfer. To reduce noise I covered the bottom of the side pods with Second Skin Damplifier Pro (I didn’t cover the vertical 2” x 6” because horizontal space is tight). I then covered the bottom of the side pods and the vertical 2” x 6” with DEI Tunnel Shield II to reduce heat radiation.

Zero-flute countersink

I mounted the clamps to the bottom of the side pod. To keep the underside of the car as smooth as possible I used flat-head screws which provided an opportunity to use one of my new zero-flute counter sinks. Wow, these cut so much smoother than the fluted ones.

The next step is to fabricate and weld the 1-1/2” tubes from the radiator to the engine compartment.

Parking Brake P2

I finally received the e-brake system for HiSpec. It seems to be well built and I was happy to see a quality assurance tag (see picture below) on the harness indicating when and by whom it was tested. The top of the ECU housing appears to be anodized cast aluminum with the backside potted with epoxy to encapsulate the electronics. The included button has an LED to indicate if the brake is engaged or not. It’s useful if you want to hide it or if you’re going with a race car interior, but I’m likely going to upgrade it.

The following photos compare the Superlite caliper (left) to the HiSpec caliper (right).

I expected the overall HiSpec system to be lighter, but I expected the calipers to be heavier due to the integral motor. I’m thrilled that the HiSpec solution has lighter calipers which results in lower unsprung weight. The following table lays out the weight for three different parking brake scenarios.

Part UnSprung Hispec Superlite Superlite & E-Stopp
Calipers Y 5.7 6.5 6.5
Caliper Brackets Y 1.0 1.0 1.0
ECU & Wiring Harness N 1.4 n/a 0.5
Handle N n/a 1.1 n/a
Handle Brackets N n/a 3.0 n/a
Cables N n/a 3.5 3.5
Actuator N n/a n/a 4.8
Total Unsprung Weight - 6.7 7.5 7.5
Total Weight - 8.1 15.1 16.3

There are three features to prevent accidental engagement/disengagement:

  • The button must be held for two seconds

  • An optional wheel speed input to prevent activation when moving

  • An optional ignition input to prevent deactivation

I spent a while trying to figure out how to mount the calipers. In particular I couldn’t figure out what the snap spring was for… at some point Bob pointed out to me that it’s a floating caliper design. Duh, that explains a lot! The caliper can slide (i.e. float) 0.35” towards/away from the rotor. I figured it would would be best to place it in the middle. While mocking the bracket I was constantly measuring and re-centering the caliper. I then figured out it would be easy to 3D print two temporary spacers to keep the caliper centered.

The rotors are 28 mm wide (1.1”) and the space between the pads is 1.2”. To ensure that the pads were perfectly spaced on the rotor I tried using some metal shims, but they weren’t the exact width that I wanted and they kept falling to the floor. So guess what? I 3D printed two brake pad spacers the prefect width and with a right angle to keep them from falling. The openings in the brake pad spacers aren’t for style points. They significantly reduce print time and the amount of material used. This is the exact opposite of CNC machining in which this would increase machining time.

Since the hydraulic brake caliper is at 3 o’clock I placed the parking brake caliper at 9 o’clock. While mocking the bracket I figured out that it’s critical to locate it in exactly the 9 o’clock position. Otherwise I would will get different fitment due to the curvature of the rotor and the shape of the upright (it’s sloped -15 degrees from vertical). I tried to do everything on the car, but after a couple of misses I decided to pull the upright… I hate removing ball joints. I think I’m going to put some anti-seize on them when I reassemble!

Rear left upright, the line scribed in the blue dye is the 9 o’clock position (when looking from the other side)

The Superlite bracket requires you to drill holes in the the side of the upright which has machined pockets behind it (i.e., the recesses above and below the 9 o’clock position in the picture above). This area is 0.3” thick which is only 0.95x the diameter of a M10 bolt which is well under the 2x rule of thumb for thread depth in aluminum. Given that the parking bracket doesn’t see much stress and that any stress puts one screw in compression and the other in tension this isn’t an issue. That said, it doesn’t feel right to put the screws there. In any event, the HiSpec caliper results in a bracket that places the screws towards the center of the upright. After careful measuring, it appears that the holes can be placed in the web between the machined pockets on both sides (see picture below). I would like to confirm the 0.934” dimension with Superlite before drilling!

Horizontal cross sections of the Superlite and new brackets

A bunch of iterations I wound up with the following bracket. This could be made from a 3/8” angle aluminum, but the Superlite bracket is machined from billet. If we’re going to machine it, we might as well give it some pockets to make it a little more like the upright!


To hold the mock bracket in place and ensure that it was parallel to the upright’s edge I used a piece of 1/4” scrap aluminum (yeah, that’s not bending). I wanted to position the bracket inboard of the upright’s chamfer so I used some scrap 1/8” aluminum to make a spacer and lined everything up using a centerline groove I designed into the mock bracket.

In the picture below you will note that the rotor’s OD is parallel with the edge of the parking brake’s pad. This leaves approximately 1/8” between the rotor’s OD and the caliper’s ID. You will also note that the caliper isn’t exactly centered on the caliper pin (or whatever it’s called).

The following picture shows an outline of the bracket and where and how deep the threaded holes will go to achieve 2x screw diameter (i.e., 20 mm).

Next step is to wire it up and test it. Apparently you need both calipers plugged into the ECU for it work.






Scale Model

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My blog aspirations took a major hit last week when my mom unsubscribed. Apparently my content was mundane and deleting the occasional email notification was a burden. She claims that it was an accident, but I have my doubts — my therapist is on the fence as to her real motivation:-)

At least when I didn’t like her liquid-margin-covered, boiled brussel sprouts I just hid them in a napkin! In any event, I’m now free to openly confess that I abhor boiled brussel sprouts, but I actually like properly-seasoned broiled brussel sprouts and I adore Kentucky Fried Chicken (don’t tell her).

So, in the spirit of more interesting content I thought I’d share a video that Kevin made about 3D printing a model of my car. As you might recall he’s designing the new tail and he wanted to see what it looked like in real-D. He makes some great points on how to optimize orientation to reduce print time and material wasted on support structure while also improving print quality.

Control Arm Clip

I needed to attach the hydraulic line for the front lift to the lower control arm. A zip tie looked a little naked and I didn’t want to use a P-clip because I’d have to drill and tap the control arm. So I decided to design one. My initial thought was to make something with a snap hinge, but that made it too bulky and not as durable as a zip tie. I wound up with two pieces that snap together on the control arm and have a recessed channel for a zip tie.

Parking Brake

I purchased the option parking brake kit from Superlite. Although it provides all of the key components the builder still needs to fabricate a custom bracket for the brake lever and route the cables to the calipers on the rear wheels. While this isn’t complicated, it’s a pain in the ass. My biggest issue was trying to figure out where to locate the lever in the cramped cockpit. This is why many builders replace the lever with an E-Stopp electric brake kit. Essentially it’s a linear actuator with an Electronic Control Unit (ECU) that utilizes a button to toggle between no tension (brake off ) and 600 pounds of tension (brake on). The unit is used in many hot rods and SL-Cs. Most SL-C builders mount the unit in one of the side pods. The issue with this location is that you have to take the body off to service it.

I spent a lot of time thinking about where to place the E-Stopp and one of Stephen’s forum posts provided the answer. He mounted the unit in the recessed floor which affords easy access for maintenance. I was already planning on creating a closeout panel that wrapped around the chair to create a flat floor. I figured it would be a great place for luggage. I figured I could could fit a T-shirt, boxers, socks and toothbrush is a Ziploc bag LOL. Stephen also fabricated a channel to protect the cables… brilliant!

So that was the plan until I spoke with Allan and Bob. Allan has successfully used the E-Stopp in multiple cars, but he’s had two cars in which he couldn’t reliably get the parking brake to hold. He called the manufacturer to see if he could increase the 600-pound tension and they indicated that they’d have to completely redesign the unit. Bob also had similar issues and his car let loose while on a trailer. He spent a fair amount of time trying to get it to work reliably to no avail. While many people have had success with the E-Stopp, two very talented builders have had issues with it while the car was in the build stage.

Back to the drawing board. I then discovered motor-on-caliper parking brakes. Instead of using a cable to actuate the caliper these systems utilize an ECU to drive motors that are directly attached to the calipers. Apparently TRW has shipped over 60 million units and Brembo and other manufacturers have integrated the motor directly into the hydraulic caliper. This reduces unsprung weight by removing the need for a separate caliper and bracket. It’s my understanding that some systems implement a true emergency brake by using accelerometers to ensure that the car doesn’t spin when the brake is applied.

The TRW looked like an ideal solution. I tried to buy an aftermarket version or at least get documentation on an OEM version to no avail. So to the junk yard I went. It’s easy to pull the calipers and ECU, but I couldn’t figure out how to activate them. I tried using a CAN bus sniffer on a running car to figure which CAN bus messages where used to activate and deactivate the brake. My conclusion was that that the e-brake ECU are typically deeply integrated into the OEM’s system and that it wasn’t going to be as easy as finding two messages and broadcasting them. There’s likely a OEM implementation out there that might be that simple, but god knows how long it would take to find.

So after over a year of intermittent researching and tinkering I ordered an E-Stopp. On the day it arrived I decided to do one final search before opening the box and installing it following Stephen’s method…. AND I found this… HiSpec Motorsport Spot Electric Parking Brake (EPB) Really?

It’s a standalone solution that includes two calipers and an ECU! To prevent accidental engagement/disengagement you need to hold the button down for two seconds. The harness enables the addition of a backlit button or LED to indicate when the brake is engaged. My understanding is that it has adjustable tension and that it’s capable of holding a mid-size truck (will get specs from Hispec). At £640.00 (~$835.00) they’re a good value given that the Superlite option costs $999 and an E-Stopp costs $479.00. I asked them the weight of the caliper/pads/motor and I’m pretty sure they said 1.2kg (2.6 pounds). I weighed the Superlite brake caliper and it was 3.2 pounds. I had assumed the the Hispec unit would have lower total weight, but a higher unsprung weight due to the motor being mounted to the caliper. It seems too good to be true so I’ll validate the weight when it arrives.

So the benefits appear to be:

  • Significantly cleaner and easier installation

  • Lower total weight

  • Lower unsprung weight

  • Lower cost

  • Better holding power

The only downside that I can think of how to release the brake if the system fails or power is lost. They quote 28 days to manufacture the units after which point they are shipped from the UK. The next steps are:

  • Weigh the unit

  • 3D print a prototype bracket. This bracket will also double as a drilling jig. I will have tabs that enable it to be clamped to the upright and drill bushings to ensure straight holes.

  • Mount and test using the prototype brackets

  • Determine how to manually disengage the brakes

  • See if Fran is interested in selling CNC’d brackets

Front Sway Bar Drop Links

I fabricated drop links to connect the front sway bar to the lower control arms. The drop link was fabricated by cutting 5/8” aluminum hex bar to length and using a lathe to remove the corners (i.e. make round) the entire length other than 0.6” on each end. The hex on the end enables a wrench to turn the link and the round section lightens the link… plus it looks trick. The ends were then tapped and drilled for 3/8”-24 Heim joints. One end is a right-hand thread and the other end is a left-hand thread. This is done so that when the link is rotated clockwise both ends expand and when the link is rotated counterclockwise both ends retract. If both ends had the same thread, rotating the link would have no effect. One end would expand and the other would contract by the same amount. I tapped the holes 1.2” deep to accommodate the entire shaft of the Heim joint. These were by far the deepest holes I’ve ever tapped and they took longer than I thought to complete. I also had to buy a new tap because I had never tapped a left-handed hole.

The Heim joint fit perfectly in the clevis. This makes sense because the clevis can be rotated so that its open ends are aligned with the Heim joint’s body (i.e., no binding issues). However, the mount in the sway bar arm is 3/4” and the only Heim joints that I could find were 1/2” wide. Since this joint will see some misalignment I didn’t want to use washers to make up the difference. I spent some time looking for 1/8” cone washers until I realized that they would be too thin to do much which is probably why nobody make them.

At that point “H” suggested that I look for high-misalignment Heim joints and I found one that was 0.875” wide. I made a jig out of some angle aluminum and a 3/8” bolt to keep everything square when removing 0.0625” (i.e. 1/16”) from each end on the sander. Apparently I can’t tap a perfectly straight hole (even after a couple of tries), so I used two nuts to lock everything in place ;-)

The lower control arm was drilled to mount a clevis. It would have be a lot easier to drill this hole on a drill press rather than when the control arm was mounted to the car, but I didn’t want to take apart the front suspension again. I used a drilling jig to ensure that the hole was square.

I also had to cut all of the grade 8 bolts for clearance reasons.

Air Jack Mounting Ring Lock

I designed and 3D printed a locking ring to prevent the air jack mounting rings from loosening. They don’t take any force so a 6-32 screw was used to keep them from rotating.

In the last post I notched the removable floor in the nose to clear the front floor jack. I created a 360-degree lock that spans the gap between the mounting ring and the floor to reduce drag… oh, and it just happens to hide my less than perfect notch ;-)

Getting Jacked

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I’ve been working hard to get jacked — don’t worry, I’m not taking roids or considering wearing a mankini.

Instead, I’ve been busy working on an air jack system. The hydraulic lift discussed in a previous post raises the nose to handle speed bumps or steep inclines. This system raises all four wheels off of the ground. Since I’m not going to do any endurance racing I have no rational need for it. However, this is my halo car so do it I must. I’m trying to talk my wife and kids into be my pit crew…

The write up and lots of pictures can be found here.