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  • Writer's pictureSpencer Powlison

How a Mosaic Batch Built Frame Is Made


Take two Mosaic frames — one Batch Built, one Made to Order — and look at them side by side. Can you tell the difference? Probably not, and that is because our Batch Built frames go through the same made-in-USA process as any Mosaic bike that rolls out of our Boulder, Colorado shop. Here’s how we build these frames so efficiently without compromising the hand-built quality you expect from a Mosaic. Step 1: Chain Stay Prep We offer three Batch Built models: RT-2 D for road, GT-2 AR for all-road, and GT-2 45 for gravel. As you’d expect, each model has geometry that’s optimized for its purpose. But you might not have realized that each of those three frames has a consistent chain stay length through the entire size run. This allows us to cut and weld the dropouts, chain stays, and bottom brackets in bulk so they’re prepped for the next step of the build.



Step 2: Tube Prep Next, we take seat tubes, down tubes, and top tubes and prepare them for assembly. That entails three bottle cage bosses per frame, internal brake line routing, and reinforcements for Di2 cable ports. Naturally, this stage of our Batch Built process is size-specific, and we keep each frame organized in tidy tube cubbies beneath our benches.



Step 3: Fixture Set-Up We rely on the best frame jigs in the industry, Sputnik Tool and Anvil, to ensure each frame in each size has consistent stack, reach, and angles. Now we’re getting into the fun part, when a bunch of titanium tubes start to look like a bike frame.



Step 4: Cutting and Mitering Tubes After the jig is set up to size, our framebuilders are able to see exactly how the frame’s down tube, head tube, top tube, seat tube, seat stays, and chain stay assembly will join together. It has to be a perfect fit, so in this step, they use the jig to guide the final tube cuts and mitering. Mitering? What’s that? Well, glad you asked; unless you’ve got really weird frame geometry (we don’t!), the tubes join at acute or obtuse angles. We trim the ends for a perfect fit, and also to account for the roundness of something like the head tube or bottom bracket shell. During our Batch Built process, we build several frames of the same size at once. This allows us to set up the tooling once and repeat the same precise cuts and miters over and over again until it's time for the next size or model.


Step 5: Frame Build At last, it’s all coming together! We put all of the tubes into the fixture and start welding. However, the frame doesn’t leave the jig in a finished state. For this step of the process, our framebuilders simply tack weld the tubes. Time for another definition: Tack welding joins the tubes so the frame holds together, but it isn’t a finished, full-strength weld. This allows us to move the frame out of the fixture to our welding booth so we can get started on the next one.


Step 6: Welding Here’s where the magic happens. We take a tack-welded frame, and give it the beautiful, finished, stacked-dimes welds that will last a lifetime. Just like every Mosaic, this is all done by hand, by an expert welder.


Step 7: Quality Control In the final step of our process, each frame is thoroughly checked over to ensure that the alignment, geometry, and finish are perfect. Whether it’s a Batch Built frame or a Made to Order frame, every one gets the same attention to detail.


Final Step: You Choose Yours! By now you can probably see that every Mosaic Batch Built frame is given the same hands-on TLC as every frame we build. The best thing is that these frames are on hand, in our shop, ready to be finished for you. Once you select the model and size you want, we’ll set up the cabling to your specifications and send it to the paint and finish shop to give it any look you like. Typically, this efficient process allows us to turn around a Batch Built frame in two weeks or less. Plus, if you end up going full-custom, our Batch Built process frees up our Made to Order queue so we can produce those frames with a quicker turnaround time. Whichever Mosaic you choose — Batch Built or Made to Order, it is built by the same people with the same care, right here in Colorado.


Words: Spencer Powlison

Photos: Mark Currie


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