Bike Check: Kova Bikes #2 Is A Machined & Bonded High-Pivot Engineering Project
Most students leave university with a piece of paper, a pile of debt and a hangover. But mechanical engineering students from Finland, Jere Laine and Tommi Riite, have something more tangible. Two years ago they decided to combine their passion for mountain biking with their engineering know-how to create a rideable and innovative enduro bike for their thesis project. By the looks of it, this isn't just another homemade bike but something made with impressive craftsmanship and attention to detail.
The foundation of their Kova Bikes Number 2 prototype is a lugged design - something that's becoming more popular, with Atherton, Specialized, and Pivot all using it at the highest level - with CNC-machined aluminum lugs bonded to carbon tubes. This method doesn't require heat treatment during manufacturing, which Jere and Tommi claim results in tighter tolerances compared to some mainstream manufacturers. The lugs are machined out of 7075-T651 aluminum (this is very different from the 3D-printed titanium lugs used by Atherton) and the carbon tubes are sourced from a European manufacturer.
The suspension kinematics are based on the Kavenz VHP (virtual high pivot) platform, subtly modified. The geometry, with a 485mm reach and 640mm stack, is based on bikes the pair have owned and enjoyed. The dropouts and seat stays are modular, enabling customization of chainstay length and rear triangle stiffness. A modular lower shock mount further enhances versatility, accommodating rear travel figures from 120mm to 180mm. The bike shown here is running 162mm of travel and a 425 mm chainstay length (438 mm at sag).
A BB/downtube/seat-tube lug taking shape on the CNC machine.
The improvised glueing jig on a welding table.
The engineers used Fusion 360 and Siemens NX software for the computer-aided manufacturing process. The bonding jig, for accurately glueing the carbon tubes into the machined lugs, was made by simply modifying a welding table with parts they custom machined to hold the lugs in place. This worked well enough for the run of four frames they made but would need to be improved for bigger batches.
To complement the frame, a full set of silver Hope components and a Fraezen cockpit were chosen, along with EXT suspension. The bike as shown sneaks under 17 kg (37.5 lb).
Lugs and machined parts for four frames.
The pair are grateful to have benefitted from unlimited access to machine time and almost unlimited amounts of aluminum. Even so, these four frames represent around 2,000 hours of work. They don't recommend their approach to first-time frame builders.
Kova Bikes doesn't have any commercial plans. "We just love it as a hobby and are looking forward to a full summer of field testing with the prototypes," says Jere Laine. "Maybe after summer, we will find ourselves back at the drawing board again. However, we both graduated as mechanical engineers in January and we hope that this project will be helpful in getting to work in the bike industry or something related to machining."
You can follow the project on Instagram.
Buid Details
• Frame: CNC machined 7075-T651 aluminum lugs bonded to custom made carbon tubing from Europe
• Fork: EXT Era V2.1
• Shock: EXT Aria
• Wheels: DT Swiss FR541 with Hope Pro 5 Hubs, Mullet
• Tires: Continetal Kryptotal with Pepis R-Evolution
• Drivetrain: Hope Evo cranks with 32T Hope chainring. Sram GX AXS derailleur
• Brakes: Hope Tech 4 V4 with 200mm floating rotors
• Cockpit: Fraezen stem with Title AH1 Handlebar
• Pedals: Crankbrothers Mallet E Silver
• Headset: Enduro Bearings Maxhit ZS44/ZS56
• Bottom Bracket: Enduro Bearings Maxhit BSA30
• Frame: CNC machined 7075-T651 aluminum lugs bonded to custom made carbon tubing from Europe
• Fork: EXT Era V2.1
• Shock: EXT Aria
• Wheels: DT Swiss FR541 with Hope Pro 5 Hubs, Mullet
• Tires: Continetal Kryptotal with Pepis R-Evolution
• Drivetrain: Hope Evo cranks with 32T Hope chainring. Sram GX AXS derailleur
• Brakes: Hope Tech 4 V4 with 200mm floating rotors
• Cockpit: Fraezen stem with Title AH1 Handlebar
• Pedals: Crankbrothers Mallet E Silver
• Headset: Enduro Bearings Maxhit ZS44/ZS56
• Bottom Bracket: Enduro Bearings Maxhit BSA30
Photos: Jere Laine / Kova Bikes
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Its so they can Scan-da-navy-in.
youtu.be/oHqJA_HrzYs?si=zepQxXfop0YlQHJj
That being said, the world of actual brands and manufacturers is vastly different, and testing in that world (even for small brands) is rigorous and intensive. Passing testing is no guarantee that something won't break, but is a good check that real engineering has happened with an eye toward performance and safety.
It's Europe so maybe they're not as dead-ass broke as a student here, but maybe get their used futon or a MC Escher poster in the settlement?
This "438 mm at sag"!
Big brands (every brand) you can all add this real world useful piece of information to your geo diagrams henceforth please so I can actually compare an apple to an apple rather than an apple to a cumquat.
And you could start using averaged effective reach, also at recommended sag, (centre of seat post/ saddle to centre of bar; with saddle at averaged saddle height for the inseam of the size of rider that the frame size is aimed at) to help the consumer too whilst you are at it.
And is very much the same as the machined lugs used by Atherton on the A-series.
Design and send to a 3d print / proto shop, then final assembly at home using catalog hardware.
Will be a great way to get custom geo exactly the way you want it.
(and then realize "oops I should have made the chainstay longer by 3mm" lol)