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Moots 3D printed Flat Mount dropout

Flat mount brings the caliper inside the rear triangle for a cleaner look.

I wanted to explain in some detail why and how we decided to use this new and different technology of a 3D printing the parts for the Flat Mount brake mount and dropout on our Disc RSL versions of our road, cross and gravel bikes. We understand this is a different look from Moots, but we will share the reasoning behind this choice. The end goal is to make the best possible bike.

For those of us who have been building bike frames for some time we have seen and built frames with a whole host of brake mounts – U-brakes, roller cams, cantilevers, v brakes, caliper brakes of various lengths, drum brakes and disc brakes. Here at Moots we have built disc bikes with ISO mounts, Post Mounts and “Hayes” 22mm Mounts, which most closely resembles the new Flat Mount standard. All of these standards, except the flat mount, were designed primarily as additions to existing frame designs, easily added on. This has resulted in very consistent results by being able to place the brake in precisely the right spot each time while making a stronger, stiffer brake platform without affecting the frame design significantly. Flat Mount however is designed more as integral to the chainstay of the frame.

When we were first introduced to the design a couple of years ago we knew this would present a challenge. Our goal with every product we make is to use the optimal method to maintain and elevate the strength, lower the weight, improve the ride and maintain the alignment of all aspects of the frame. The best way to introduce this new brake mount and know each frame is going to hit that mark was to design a system that had the dropout and the mounts “built as one”. This assures that we can design our frames around the best design for the ride, function and durability of the bike.

To explain; each variation in frame design regarding chainstay length and bottom bracket drop the top of the brake mounts have to pivot to match the center of the dropout. By making this as one part the dropout, the brake rotor and the brake are held in the proper place. The dropout faces are also square to one another every time and the wheel sits straight in the frame.

The final version with Mr. Moots printed in part, wire channel, 142 x 12 thru axle and flat mount.

Another very important design element that needed to be addressed was the brake clearance with the seatstay. Again we wanted to use this mounting system for a broad range of seat tube lengths, seat angles, bottom bracket drops and chainstay lengths. This is why the dropout has the built in seatstay landing that is above the axle therefore clearing the brake on all size bikes.

From a production viewpoint whenever you can use a single set-up to tack your frame the consistency of alignment will be higher than jigging, welding, jigging. The “built as one” dropout and brake mount loaded into the jig and tacked as a complete frame assures the rear wheel is centered and straight and the brake will align perfectly every time.

Why did we spend over a year working to have a 6/4 printed part and not one that is machined from 6/4 billet?

The size of a piece of 6/4 billet to make a part of similar dimensions to the printed part you see would weigh 2.4lbs, per side, not to mention the hours of machine time and the limitations in design features. This creates about 85% waste. The way a 3D printer works is to put down a very thin layer, 60 microns thick in this case, in an Argon filled chamber, and then a laser fuses the material along a precise computer controlled pattern. The waste is for this process is well less than 10%. Our partners in this, Mirada Pro, have extensive experience in utilizing the benefits of this technology. They have made a wide variety of parts for most of the cars on the F1 starting grid, for aerospace and for surgical aids. Applying their printing knowledge and our expertise in bike design (and 5 prototypes) we have a great part.

Proto #2—a view of the wire channel.

Some other great benefits of the printing process are that we have a part that is hollow and can be built with features like an internal tube for routing a Di2 wire. Also 3D printing in Titanium works best with 6/4 alloy. This is comprised of 6% aluminum, 4% vanadium and 90% titanium. It is the most common alloy used in the aircraft industry for structural elements of a plane and the alloy we have used on our dropouts for many years. A printed part in this material tests out to match 6/4 billet for tensile and yield strength so there is no strength compromise while creating a hollow lightweight part with very little waste.

Non-drive side with flat mount, chain stay plug-in and radius seat stay landing.

Bottom line, a strong, lightweight part that assures alignment for very critical elements, brakes and rear wheel. Different, yes, but it answers the challenges presented for manufacturing a great Titanium frame by utilizing the latest technology available.

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