Bike Check: Brotlos Design's mpEV01 - Inspired by Kavenz & Made From Steel
Earlier this year I had the chance to meet Michi and Pascal from Brotlos Design. They both have an engineering background and work for Swiss engineering companies, and when they find time, they meet in their workshop and create wooden furniture and lamps.
As they both got more and more into mountain biking, they decided to stray away from woodworking and build their own bike. They were fascinated by the Kavenz Youtube video series and the design of the bikes, so they got in touch with Giacomo from Kavenz. Under the condition that they don't make the frames commercially available, they got permission from Kavenz to build their own steel frame with 3D printed parts, which is based on the Kavenz suspension design.
While Michi and Pascal designed the 3D printed parts (made by Ecoparts), the frame was brazed by Stefan from Scarcycles. It comes in at around 3.7 kg (without shock) and the tubing is Reynolds 853.
As they both got more and more into mountain biking, they decided to stray away from woodworking and build their own bike. They were fascinated by the Kavenz Youtube video series and the design of the bikes, so they got in touch with Giacomo from Kavenz. Under the condition that they don't make the frames commercially available, they got permission from Kavenz to build their own steel frame with 3D printed parts, which is based on the Kavenz suspension design.
While Michi and Pascal designed the 3D printed parts (made by Ecoparts), the frame was brazed by Stefan from Scarcycles. It comes in at around 3.7 kg (without shock) and the tubing is Reynolds 853.
Names: Michi and Pascal
Hometown: Lucerne, Switzerland
Height: 185 cm
Weight: 80 / 84 kg
Website framebuilder: scarcycles.ch
Instagram: @brotlos_design / @scarcycles
Hometown: Lucerne, Switzerland
Height: 185 cm
Weight: 80 / 84 kg
Website framebuilder: scarcycles.ch
Instagram: @brotlos_design / @scarcycles
The dropouts as well as the bearing seats for the chainstays and the seatstays are made using additive manufacturing; the material is high performance tool steel 1.2709 (maraging steel). The AM Rocker is made from Ti-6Al-4V titanium alloy.
In order to keep the costs low, they went for a secondhand SRAM Eagle drivetrain and Fox suspension. When we took the photos, they were running a Fox DPX2, but in the meanwhile they replaced it with a RockShox Super Deluxe Ultimate (love the name) coil, which has improved the performance a lot according to Michi and Pascal.
To get some light wheels and lots of grip at the same time, Michi and Pasci went for Pirope A.30 wheels with "heavy but awesome" Michelin Wild Enduro tires. The Shimano XT four-pot brakes are basically maintenance free and just work.
A Renthal Fatbar 35 is clamped by an Apex 35 stem, the grips and saddle come from Ergon. The handlebar has a rise of 40mm, as the steerer of their secondhand fork was a bit on the short side.
The Brotlos Design mpEV01 rear triangle.
The 3D printed, generative design titanium rocker weighs in at just 150 grams.
A closer look at the bottom bracket area. Note how the shock mount looks quite different from the original Kavenz design.
Brotlos Design mpEV01 (Michi Pasci Enduro Version 01)
Frame: Custom, one-off steel frame with 3D printed lugs. Brazed by Scarcycles, designed by Brotlos Design, inspired by Kavenz.
Shock: Fox DPX2, 160 mm travel (205x65), 210 psi, no tokens, LSC 9 clicks from open, LSR 3 clicks from open. Second shock: RockShox Super Deluxe Ultimate Coil 2021, 205x65, 450 lbs, LSC 6 clicks from open, LSR fully open
Fork: Fox 36 Fit4, 170 mm travel, 88 psi, no tokens, LSC 6 clicks from open, LSR 6 clicks from open
Wheels: Pirope A.30 29"
Tires: Michelin Wild Enduro Front and Rear (21 psi front, 24 psi rear), no inserts
Drivetrain: SRAM Eagle
Brakes: Shimano XT
Cockpit: Renthal Fatbar 35 and Apex 35
Size: custom, 505 mm reach, 648 mm stack, 78.6° seat angle, 64° head angle
Weight: 16.5 kg (frame without shock: 3.7 kg)
Colour: The frame color "bottle green RAL 6007" was chosen by one of the partners as a testament to the countless hours that Michi and Pascal were not at home. They like the color too.
Frame: Custom, one-off steel frame with 3D printed lugs. Brazed by Scarcycles, designed by Brotlos Design, inspired by Kavenz.
Shock: Fox DPX2, 160 mm travel (205x65), 210 psi, no tokens, LSC 9 clicks from open, LSR 3 clicks from open. Second shock: RockShox Super Deluxe Ultimate Coil 2021, 205x65, 450 lbs, LSC 6 clicks from open, LSR fully open
Fork: Fox 36 Fit4, 170 mm travel, 88 psi, no tokens, LSC 6 clicks from open, LSR 6 clicks from open
Wheels: Pirope A.30 29"
Tires: Michelin Wild Enduro Front and Rear (21 psi front, 24 psi rear), no inserts
Drivetrain: SRAM Eagle
Brakes: Shimano XT
Cockpit: Renthal Fatbar 35 and Apex 35
Size: custom, 505 mm reach, 648 mm stack, 78.6° seat angle, 64° head angle
Weight: 16.5 kg (frame without shock: 3.7 kg)
Colour: The frame color "bottle green RAL 6007" was chosen by one of the partners as a testament to the countless hours that Michi and Pascal were not at home. They like the color too.
The bike was designed with a certain trail in mind. It's rooty and very fast, and their trail bikes were just not capable enough. The goal of the whole project was to get a nicely performing bike with sturdy parts. They intentionally didn't use any carbon parts. Because they bought a lot of used parts, the whole bike wasn't too expensive in terms of money - however Michi and Pascal acknowledge that they've invested a ton of time into this project.
 | Design and engineering were very important to us. Our goal was to create a high-end, self made frame. Just brazing some tubes wasn't what we were looking for, we wanted to use new and traditional techniques. We've invested a lot of time in the design process. Proportions were important to us. From the first CAD sketch to the first test ride it took pretty much exactly one year, of which we invested about 9 months just in design and engineering. Thanks to AM technology we were able to design lightweight and high-strength parts, which are also nice to look at. |
When your handlebar diameter is nearly the same as the top tube diameter, you know you're riding a steel frame.
BikeYoke dropper post and the brazed-on Scar Cycles head badge.
How do they like the bike? 11 out of 10. They say that the bike performs perfectly on the trail that they had in mind when designing the bike. The steel frame has some flex which took some time to get used to, but it provides a lot of grip in turns and off-camber sections. Nevertheless, they think they'd have even more fun on a shorter bike and in case they ever build a second frame, they'd do some little things differently.
Michi and Pascal designed two versions of the rocker. The one you see in the photos was designed using generative design and weighs 150 g. The second one was also additively manufactured and optimized to the max, so that they could achieve a weight of 130 g. When designing the generative design version, estimating the loads was difficult, so this version turned out a bit heavier. Further, they did some design-assisted FEM analysis. Again, it was difficult for them to make suitable load assumptions.
All 3D printed steel parts are hollow and have a wall thickness of about 1mm. The bearing seats in the dropouts are printed directly, without any rework.
The rear end got some extra reinforcements compared to the original aluminum Kavenz.
Pirope A.30 wheels keep the weight low.
Michelin Wild Enduro front and rear tires.
"Heavy but awesome" Michelin tires.
Custom sizing: reach 505 mm, stack 648 mm, seat angle 78.6° at 785 mm seat height, head angle 64°.
Michi and Pascal are grateful for the support they got from ECOPARTS, who not only gave them modeling tips but also provided test material for soldering. They would also like to thank Stefan from Scar Cycles for his support and brazing the frame. They built a very good relationship and exchange ideas on a regular basis.
Author Info:
Member since May 15, 2020
Must Read This Week
10/10 for the brazing. You get my upvote.
Have a look:
www.pinkbike.com/news/sram-produces-generative-design-prototype-cranks-in-partnership-with-autodesk.html
You'll also find a few research papers on the internet.
I know topology optimization is not generative design, but nevertheless have a look at this project from Nelson Mandela University:
aedg.mandela.ac.za/Projects/Mountain-Bike-Frame
That said, there are manufacturing challenges in creating complex designs. For the foreseeable future, it will be cheaper to extrude, stamp, and forge than to use SLS powder metallurgy or similar techniques. Advances in filament winding are likely to lower the price and raise the performance of fibre composite parts.
images.app.goo.gl/9ApU1RZbWZDKNQU59
Yeah I'm just gonna go ahead and assume that picture didnt work hahahaha
But in there lies the problem, but just ask AI to design a super mountain bike it for $1000
I am sure it would be wonderful!
Riding a heavier bike makes you fitter.
This is the future
Really cool project, regardless. 420 braze it
Homemade carbon bikes, Steel HPP bikes and what's to come up in the near future.
Imagine, talking bikes all day long and testing that stuff - sounds pretty good to me!
@TEBP @SleepingAwake @pensamtb
Cool project indeed!
Thanks for the answers regarding the alloy by the way. Indeed for my frame I wanted a 400mm seattube instead of the standard 440mm seattube and according to Tom's calculations (BTR) they indeed had to get a replace the 631 seattube by a 853 one. But I automatically thought it was because they required stronger welds. Could be that they just needed a stronger tube too.
In this case for me, I am exactly the same height as the owner of this bike. And surprisingly/not surprisingly, the geo is almost bang on for what I had theorized as my "best fit".
Custom builders have a chance to keep that shit alive
There is an initialism called D.I.Y. that means do it yourself. Some people with general skill and a willingness/ability to learn things do almost all of their own service on everything. Literally everything I own I service and maintain myself. Except computers, they are made to self destruct so I let nature take its course.
On sailboats it has allowed us to use remarkably small lines for huge loads. And with lighter weight and less stretch as well.