NBM CNC machined DH bike, side shot

Although it isn’t the method of choice for any large bicycle manufacturers, it would be cool to see more effort go into creating CNC machined frames, if only because they tend to look pretty awesome! This eye catching downhill bike was built by Stewart Palmer, a fifth generation engineer with past experience machining F1 race car components and high performance engine parts.

After his Dad’s job became redundant, Stewart’s parents founded North Bucks Machining in 2011 and took their son and daughter on as employees. Stewart enjoys riding in his spare time, and with the dream of creating his own project suddenly possible he spent 18 months designing and building his first bike frame…

NBM CNC machined DH bike, pivot area

Although North Bucks Machining started out with 3-axis machines, Stewart wanted to utilize his past expertise and push NBM into more sophisticated 5-axis manufacturing. The company now uses a Quasar 5-axis machining center and Open Mind’s HyperMILL cam software, an upgrade that made the bike project possible.

NBM CNC machined DH bike, head tube junction NBM CNC machined DH bike, pivot, side

Working from Stewart’s sketches of the frame a company called Laser Scanning created a 3-D model, then virtually simulated loads and stresses on the design before the machine work began. Stewarts aim was to improve upon the strength and structural integrity of traditional mountain bike frames. Since hollow tubes have inherent weak points at every weld, he cut his frame from solid billet aluminum and scalloped out unneeded material to keep the weight as low as possible.

NBM CNC machined DH bike, rear shock area

The NBM Bike’s frame is comprised of three parts- the main frame, the seat post and the swingarm, and it’s amazing how much aluminum is left on the factory floor- The main frame was machined out of a 100kg block of aluminum, and cut down to a 4.5kg front triangle. The seat post goes from a 15kg block to a 250g piece, and the 2kg swingarm is cut from a 50kg chunk.

NBM CNC machined DH bike, swingarm on machine

It took 40 hours to machine the main frame, 18 hours for the swingarm and 15 hours for the seat post. This is a costly and slow method of production, but at this stage the company isn’t trying to make a mass consumer bike, they are only seeking to prove Stewart’s concepts. The bike project also helps NBM fine-tune their processes to produce the best possible surface finishes. With the capabilities of HyperMILL’s advanced finishing machining cycles, the bike’s pieces come off the mill ready to assemble and ship, with no further hand finishing required.

NBM CNC machined DH bike, angle shot

Stewart does intend to reduce the machining time by employing Hypermill MAXX software for rough machining. With this software and a faster spinning CNC machine, production time could be reduced by up to 80% in the future. Stewart also plans to keep shaving weight off the 6.75kg frame until it sits around 5kg (11lbs). Given his F1 experience, strategic weight reduction is nothing new to him. Once the design has seen these revisions, NBM hopes to eventually retail the next generation frames for about $9,820 USD and as a complete top-tier build for roughly $14,030.

Stewart says he’s ridden the bike but hasn’t had a chance to push it to its limits, so unfortunately we don’t have much info on how it actually performs on the trail. Interested riders can contact NBM for more information on the project, and if you’re anywhere near Birmingham, UK, the bike will be on display at the MACH 2016 manufacturing exhibition from April 11-15th.

H/T to Rhys Williams at Pulse PR



  1. The surface finish does look nice, particularly if it has only minimum post-machining polishing, but I would be hard pressed to not immediately anodize it teal, purple or some other ridiculous 90’s color. Maybe a Kooka-style Rasta fade for extra silly points. So much un-ano’d aluminum just seems like a travesty to me.

      • Keep in mind, engineers means different things in different parts of the world. In this case, this “engineer” would be a machinist in the US.

        Machining exercises like this is cool and all, but have little use in production. The owner of the company I work for wanted to mill a transmission housing for a helicopter out of a 800 lb block of magnesium, finish product would be 10 lbs. The engineers thought it was stupid, the machinists thought it was a waste of time, the shop foreman wanted to farm it out because he didn’t want the wear and tear on the machines just rough cutting for a few days per part.

  2. “After his Dad’s job became redundant, Stewart’s parents founded North Bucks Machining in 2011 and took their son and daughter on as employees.”

    Confused. Is his dad in this instance, his grandfather? The wording is very weird.

  3. There is one almost identical make by a Chinese company….. for as little as 10.00 / frame set….. and in anodized colors. I wish I could post the picture here

    • Aluminium is very very easy to recycle (and recycle, and recycle, etc, over and over), without losing any of the qualities of the material. It does take quite some energy to do so, but it’s one of the great advantages of alu.

      My main worry (production-wise) would be the machine time and wear. Product-wise, you could wonder if this is in any way better than a properly welded alu frame. It’s probably not, not at this point anyway. Design-wise, it’s a nice project though, with good potential to learn a lot from.

  4. I presume once he’s happy with the design, he’ll look into casting it. Then it nearly makes sense.

    Very pretty though, but why does the word “mudtrap” stick in my mind?

  5. As a marketing exercise for the capabilities of the engineering company it’s brilliant. From a practical industrial design standpoint it’s impractical. I do appreciate though what must have been a massive amount of time put into the 3D modelling.

  6. Time to machine out a floating brake for it in similar fashion. Whom ever was bummed about the wasted material; chips are easily and readily recyclable.

  7. “Stewart Palmer, a fifth generation engineer” … “a company called Laser Scanning created a 3-D model, then virtually simulated loads and stresses.” So the fabled engineer of 5 generations paid someone else to do the engineering? That would make him a designer, not an engineer.

  8. Really cool concept but I’m not sure if it’s going go take off considering weight, price and thr fact that conventional tube and weld bikes don’t reaĺly fsil that often. Besides you’ve got carbon monocoque if you want bike without welds.

  9. PaulM,

    Aluminum casting has no where near the strength required. The design would have to change completel . Otherwise, you’d already have casted stems, hubs, etc.

  10. Want to give this exercise a double thumbs up – however, the lack of an integrated seat post clamp prevents my full digit elevation

  11. The flexiest 14+lb frame ever made. As a promotion, fine, but it perpetuated the myth that billey frames can be a viable solution. It just reminds me of the bad bicycle concepts put out by design students, every year.

  12. Such a pretty thing to look at! More of a showpiece than a bike you will do shuttle runs on with your buddies.
    I guarantee it will end up in the companies lobby hanging on the wall.

  13. an engineer that did sketches and had some other company build models? F1 and he didn’t use composites? cool little machining project to take to trade shows, but i am dubious about their use of the title “engineer”.

  14. Piece of incredibly expensive bicycle junk. This thing has ZERO torsional stiffness, and in order to divert everyone away from this fact they waffle about the alleged weakness of tubes. How ludicrous.

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