We get a lot of press releases for e-bike conversion kits
in our inbox. Most are hub-drive motors, which aren't ideal for mountain biking. Recently we got an email from an Italian college student called Davide Zanetti who has made a DIY mid-drive motor that can be fitted to a regular MTB, and he says it only cost around $300. The advantage of a mid-drive motor is that it utilizes the bike's gearing, so it can provide more torque to the rear wheel when climbing in the lowest gears. It also improves the sprung-to-unsprung mass distribution for better suspension performance.
Davide's DIY unit uses a skateboard motor which he's limited to 300W of power. This isn't far off the output of commercial e-bikes, and Davide says it's enough to roughly double his climbing speed. It's paired with a DeWalt 5ah 21v
power tool battery. These only provide about 100 Wh of energy, which he says is enough for about 500 m (1600 feet) of elevation gain, but because these batteries are relatively cheap and light and commercially available, it's possible to carry a spare or two to extend the range. You could even pop into a hardware store if you run out of juice!
The motor uses a belt drive on the left-hand side to provide a 4.5:1 reduction gearing. This is connected to a 12-tooth sprocket on the right, which drives the crank via a chain and a larger sprocket welded to the chainring. This should provide an overall reduction gearing of about 12:1, meaning the motor's torque is multiplied by 12 times at the crank. The skateboard motor is only rated for 2 Nm of torque so that works out to about 24 Nm at the crank - about half the assistance of the lowest-torque commercial e-bike motor, the TQ HPR 50
. But still, if you use a high cadence that should still be a meaningful amount of assistance. Davide says his drive unit weighs 2.5 kg including the battery. That compares to 3.7 kg for the TQ (the lightest on the market) with its 360 Wh battery.
Best of all, it can be removed with a few bolts to return to a regular bike.
There doesn't seem to be a pedal sensor but rather a throttle on the handlebar to control the motor. This technically makes it different from pedelecs
(which we usually incorrectly call e-bikes), because the bike can move without the rider pedaling. This may have certain legal implications depending on the country.
But whatever the case, it's really cool to see what can be done on a budget with a bit of ingenuity. While this is just a hobby project, the idea of a lightweight, removable motor that can be fitted to regular bikes with interchangeable off-the-shelf batteries is something I think plenty of people would be interested in.
interesting that no f*cker has identified as or owned up to being a dewalt guy ( or gal) yet
jk I loved my Stihl chainsaw
I'll always be DeWalt but I must say Milwaukee has an astonishing variety of random and very specific tools, and it seems to be increasing daily. Also the storage packout system thing is the undisputed best of the field from what I can see. They have to have an entire section of the HQ office staff on acid just brainstorming insane stuff that nobody else is thinking of.
It is now firmly a prosumer tool, with a marketing budget that likely far exceeds anything else out there.
Many moons ago Milwaukee was bought by the Asian conglomerate TTI, they also own Ryobi, Dirt Devil, Hoover. www.ttigroup.com/our-business/brands
Check out “Boltr” tool review, tear downs by a slightly crusty French Canadian lib=vying in Northern BC, his videos are pretty funny, and very informative.
Makita is one of the only remaining independent tool manufacturers, and they come in a great anti-theft teal.
Hard to beat Hilti tools, Makita is a good prosumer tool
Makita stuff does seem pretty sturdy, I manage industrial construction projects and my company is full blown makita unless they need a tool they don’t make, it sure seems to hold up well because we have some pretty old stuff that still works great and our guys just beat the absolute f*ck out of anything they can touch.
Hard to beat hilti for sure, and they charge accordingly. Their sales reps can also be just a nightmare. You either cannot get a hold of them if your life depended on it, or you can’t get them to shut the f*ck up. This is first hand experience.
I think purple tool or so could cost more or burn your eyes.
Using this as an example, it would be a poor internship project because the student has not had to factor the economics required for production ( a key part of being an engineer) and the end result as it is wouldn't be something usable by a company. Where a new college grad could get hired in to an R&D team and spend significant time prototyping and developing a manufacturer-able version that would meet company profit goals. That would take more than 6-12 weeks (most internships in the US last that long.)
I was really excited about his product when it was announced at Sea Otter a few years back. Trying to see if any early adopters have any real world experience with it. Looks like it is throttle driven at the moment but pedal-assist is in development. No I am not affiliated or an employee of this company. Just trying to see how I can add some juice to my beloved stumpjumper evo without getting a levo and having to maneuver a 50+ pound bike.
$6000 bike plus $300 motor......
I feel most mtb trails will be full of bikes with throttle s and asshats riding them. Bought or built they are coming for the trails. And the only real answer is enforcement and that sucks too…. Should have left pandora in the box.
In all seriousness though. If someone can get batteries to store more energy in a lighter package a more polished version of this and bikes that are made to accept it would be the future.
that thing with adapters sold for different models.
it could be taken to the next level by
1 implementing torque sensing, motor cut out during shifting or braking
2 moving the freewheel from the rear hub to the bottom bracket, letting the motor apply Regen when needed (you could also shift without pedalling)
3 make it even even easier to pop in/out of the bike. ideally just to gears that would engage when you lock the power unit in place, removing the belt and providing gear reduction at the same time. The only downside would be having the large gear permanently on the bike but that would be an acceptable compromise, or you could still dismount it when you know you're going to use the bike for a while without assist/racing...
4 have different battery sizes and multi battery configurations, depending trails. you don't want to be carrying dead weight. lockers at the trailhead or even jus locking your battery to a fixed point
Nicely done bit of engineering Davide!
Has anybody already thought of that??
Seriously-.Nice Work Davide!!!!
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