"The Degenerate" - 10kW MTB to E-Dirtbike conversion.

E-Bikes/OneWheel/EUC/GoCart/Scooter
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Hello guys,

I’m looking for some input and if maybe someone has done a project similiar to this or knows someone/ can link me somewhere were I can learn a bit about the engineering challenges of this idea.

Obviously I’m not the first one doing a build like this but from what I have seen what makes it an oddity is mainly:

  • No mid drive or hub motors instead two flipsky 63100s powered by two linked 75200Pro with a 14s8p (Samsung 50S) battery pack. Motors are mounted around the head tube area going to a common titanium shaft via belts. The shaft ends before the seat tube area where another mounting plate with a second jackshaft assembly receives the power via a helical bevel gear.

On the same jackshaft is a 420 sprocket mounted transmitting the total power of the 24:1 reduction (theoretically ~350Nm) to the rear wheel where a big 420 chainring is mounted at the 6-bolt brake-disc mount. Since it is planned to be a full suspension aluminium frame there will be chain guides and top and bottom spring loaded tensioning arms.

The setup enables normal pedalling and doesn’t interfer with the coasting mechanism of the free hub. Throttle is applied manually via a lever/ twist throttle. The top speed with the gearing should be 50km/h and I hope the reduction together with sensored and FOC is enough to be usable when going slow while doing relatively slow and steep offroad climbs.

Overall the bike is configured like a DH MTB. 27.5/29*2.8’ wheels, 210mm rear shock, 200mm inverted DH fork.

I’m wondering if the forces e.g. along the chainline with this extreme reduction would simple be too high for a regular aluminium MTB frame to handle. Or there are other aspects I might have overlooked.

I want to do the mounting with custom molded 3d printed carbon-nylon sections that allow for fitting heavy duty square metal brackets onto the frame at multiple points from the head tube where the motors will be along the top tube to the seat tube.

The battery is planned to be in a custom carbon clamshell that fits into the main triangle only leaving space for the rear shock.

Any inputs, thoughts, criticisms are appreciated :+1:
Have a good one and I wish you all smooth riding!

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Sounds like you’re building your own version of a bimotal kit.

I’m not sure where you live, you should know that there is a lot of e-bike hate on mountain bike trails in the USA. Even regular pedal assist ebikes are restricted in a lot of places. Anything with a throttle is considered e-motorcycle territory, and is not ok to ride on public / shared use trails, at least where I live.

That said, if you’re using the throttle to blast up fire roads, and then ride down bike only DH trails, it could be a lot of fun. I know europe has embraced ebikes far more than the states, but they also have stricter regulations on ebike power and speed.

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Good point! E-Bikes are very popular on the road here I’d say you see more people riding them compared to regular bicycles. I was also surprised when I was at a bicycle (repair) shop that about half of their displays were E-MTBs.

I have hardly had contact with the local MTB community here in austria but I’ll check out some forums to get an idea if this issue is frequently discussed.

When it comes to power - I plan to have a switch to trigger a 250W and 25km/h limit preset for the road. I definitely won’t mess around on public roads.

But yes bicyclist can be very particular on a lot of topics and I get it. In vienna there is a long wide alley through a huge park. I’d take my E-Skateboard there almost daily, weave through people and bicyclists ofc keeping a safe distance. And I skated past the regular police patrol many many times, they didn’t bat an eye I heard the same from other E-Skateboarders. So at least in that regard it seems like you don’t have to worry about trouble with cops even if your stuff looks obviously modified as long as you behave and don’t disrupt/ endanger others.

Oh yeah the brake side mounting, haven’t seen that as a kit yet. Ok, I’ll l do some digging in the local forums - thanks!

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