Stim.Tech Articles

Keeping With The Flow: Carbon E30 Brake Ducts

July 29, 2018 Braking 0 Comments

Returning from our recent blog drought, we bring to you a new product which we are quite excited about. Who am I kidding, we’re always excited, but perhaps slightly more excited. To keep with the times (well, not really), we have delved into the world of composites to progress our product line.

Some time ago, I was fabricating the tubbed, tube style front uni-body for our e30 race car and the front suspension was sitting on a shelf near by. Looking at it I thought to myself “those strut housings are really nice, but those brake ducts look totally pre-war”. This was not far from the truth as they had been fabricated from looting the scrap bin at 3AM prior to loading up for the track one night. I decided one day we would make something superb, beyond superb even.


Enter, the STIM.TECH E30 Carbon Brake Duct. With help from our friends over at Spage Sport we have the initiation of our composites product line.

Designing a brake duct backing plate is not the most daunting of tasks, as it has but a few criteria, i.e. it shall fit on the car, it should direct air into the rotor veins and it should be versatile with various brake set-ups.

The biggest consideration for this project was “Design For Manufacturability” or DFM for short. This means that we had to come up with a design which would meet our functionality criteria, but also be a part in which we could produce without incurring costs so great that it would be unaffordable to our end-user.

The first step for this project started with my lovely welded steel / tremclad rust paint original brake duct. We ripped the bolt-pattern and basic dimensions from it and we were on our way. Quickly, we had a model whipped up and we got right into prototyping. Going through numerous revisions of our shape, the major refinement was the position of the duct inlet. Providing enough room between the inlet and the strut housing was critical so that installation of duct hose would not be a monumental irritation. On the e30 front strut housing, moving the duct inlet outboard from the hub helps add clearance against the strut housing but also distances the airflow from the rotor vain entrance.

Revisiting the aspect of manufacturability we had to asses how complex we could make this part. If we were creating a one-off unit for a specific brake set-up and cost was no limitation our end design would be quite different, but our goal was to create a brake duct which would be universal to all brake set-ups used on e30 strut housings.

After a number of revisions we arrived at a position far enough from the strut housing to allow ease of duct hose installation as well as an air entrance fairly centralized to the rotor vanes.

Upon arriving at a design which we were satisfied with, we moved on to planning our manufacturing strategy. We wanted the outside of our ducts to have a crisp, uniform carbon appearance. This would require a “negative” mold of the part. We 3-D printed a lineup of  “plugs” for the creation of our negative mold. A plug is essentially just the positive body of our part. Our plugs were modelled to feature what is known as a “draft”. This is when the entire part has a very slight taper along one axis. This draft is critical for our mold to allow easy extraction of completed parts.

This is where we joined forces with Spage Sport. Armed with our 3-D printed plugs, they quickly had our mold built and prepared for production. Spage uses primarily the vacuum infusion process to lay-up composite parts. This process is the industry standard for composite production, unless of course, you just happen to own a large volume autoclave.

The infusion process consists of producing a dry lay up of carbon layers in which you will submit to vacuum and draw the bonding resin through. This process, under load, pulls all of the carbon layers together and infuses them with the exact quantity of resin required with no voids.

To ensure the best possible results ,the layups are kept in the molds under vacuum until the resin has fully cured. The time required for the curing process is dependent on the resin used. This is typically in the 8+ hour range.

Above, our first set of carbon brake ducts are shown. At a structural 7 layers of carbon fibre, these parts weigh 2.3oz each, or 65 grams, to us Canadians. Once again, we have managed to create some beautiful parts that no-one will see unless they are stealing your wheels.

Test fitting our completed duct on a strut housing allows us to verify we have no interference issue’s.

On to some details: The brakes shown in the above mock-up photo are the standard 288MM upgraded rotors. Our kit will be available with a variety of spacer options. As shown in the mock-up picture, the duct can be spaced off the strut housing to gain a tighter fit against the rotor, this is critical in achieving the maximum amount of airflow into the centre of the rotor. Our kit will include all necessary hardware for mounting. The ducts are designed to be used with standard 3″ duct hose.

Stay tuned for updates!

Check out our friends at Spage Sport for all of your composite needs!



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