I want to drive the Cliffhanger but without pedalling it, which of course was the whole goal of getting a garbage bike. But is it possible to build a sane commuting e-bike for not very much money? I decided to start with the coolest part: buying a motor.

The bike plan

For reasons that are still unclear to me, I decided that I wanted a mid-motor arrangement. A lot of the inexpensive e-bikes out there use a hub motor, where the hub of one of the wheels is replaced by a motor. This makes a lot of sense to me, and the motors are cheaper, but I am not ready to learn how to make a bicycle wheel yet. Instead, I picked a mid-motor, where a motor sits in the middle of the bike, and helps drive the crank in parallel with the pedals. Think of it like a Prius-style hybrid.

My goals for the project are as follows:

• Don't spend too much money, like under $800;
• Hit at least 30km/h;
• Climb the hills outside my house without making me have a stroke;
• Carry at least one dinner's worth of groceries home from the grocery store.

The sketchy plan

My initial plan was to buy one of the cheap brushed-motor kits like the MY1016Z, fabricate a bracket for it, and mount it so that it was driving the crank in parallel using a second, tiny chain.

These kits cost well under $160, which would make it easy to hit my price goal of "be cheap as hell." You can see that they are shipped as a grab bag of so-called "universal" parts, which will actually need fabrication to fit virtually any frame:

This started to fall apart as I wasn't able to find any non-sketchy folks doing this: almost all of the people setting this configuration up on YouTube were using the crappy freewheel sprocket that the kit came with, and an angle-grinder-modified chainring. This would still be a fun "ultra-low-buck" build for later, but I decided (somewhat atypically for me) that I would just spend a little more money and buy a drop-in mid-motor kit.

If I knew someone who had already done a conversion with this exact setup, I would have felt much more comfortable doing it with someone to bounce ideas off of. That said, one of my favourite YouTube channels, Low Buck Garage, managed to spend what looks like a really fun couple of days in the garage slapping this thing onto a tricycle. Maybe this kit would really shine moving a go-kart...

The expensive plan

These drop-in motor kits replace the crank entirely, and handle all the motor controlling, parallel drive, and freewheeling inside an enclosed module which hangs off the bottom of the frame's "bottom bracket."

From what I understand, I will remove the old pedal crank from the bicycle, and shove all this in. I'll lose the front three gears, which means I'll have to change some things, but it'll be fine.

I quickly determined that there are two major games in town for inexpensive DIY mid-motor drop-in kits: Tongsheng and Bafang.

Tongsheng's TSDZ2 seems to have the advantage in terms of smoothness and controller sophistication, using a torque-sensing system that gently applies power to "torque-fill" your pedalling as it detects the force your legs are putting into the pedals. In contrast, Bafang uses a speed-sensing system that has to watch you pedal past a sensor a few times before it kicks in a given level of assist, which can be a little jerkier.

Tongsheng's little spinner is also a bit cheaper than the Bafang, but not enough to make a material difference.

Bafang seems to make a motor that's a lot tougher, and a lot more tolerant of modification for performance. For a couple bucks, you can buy or make a serial cable that lets you make the onboard controller do basically whatever you want, and there's a fully open-source firmware if you want to get really wild with it.

Keep in mind that a lot of the information is from pre-pandemic days: it seems like both manufacturers have released upgraded systems (such as Bafang's M625) since the initial flood of competitive reviews, but I can't figure out what those upgraded systems add, or how to buy them. It's possible a lot of them are simply a bundle of the motor with a battery system that works well, and some goodies to make a conversion easier for normal folks like not-myself.

A third comedy option was to buy a used Bosch mid-motor setup. Bosch makes a lot of trustworthy – if expensive – car parts, and their solution looked pretty slick.

Unfortunately, it took almost no research to determine that there is a flood of cheap used ones on eBay because the Bosch units have poor waterproofing and eat themselves alive if the bearings aren't routinely serviced. Also, their proprietary software requires an internet connection and "phoning home" to the manufacturer even just to read information off of the motor. Spare parts are also largely unavailable, and some models need a specialized bicycle frame to mount them, which makes them impractical to use in conversion.

All this is a shame, because you can get a pulled Bosch gen-1 for about 200 bucks, and the construction seems good outside of the reckless bearing seal design. I assume that an open-source controller is somewhere out there, but it's not enough to overcome the rest of the negatives.

Ultimately, I decided on the Bafang BBS02, sourcing it from AliExpress. Even though it's a more expensive option, being able to rely on the community to figure out how to fix things or debug my install will probably come in handy in the future.

Buying it

I have been buying crap off AliExpress for the better part of a decade. I am extremely comfortable with it, and have a pretty high-ranked account status which entitles me to a lot of leeway with refunds and returns. As a result, I felt comfortable shopping there for motors.

The first thing you need to know about AliExpress is that it's really easy to start a store, and very hard to keep a store going. Some stores will create multiple "sub-stores" on AliExpress in order to create the illusion of competition, play with pricing strategies, or have a backup in case they build up too many bad reviews and get hammered by the platform.

AliExpress' requirements for listing things in the search results are very strict, and there are a lot of little tricks and traps that you'll run into. For instance, sellers are excluded by default from the "sort by price" feature, unless they pay the platform more money. Don't use it.

Initially, I was kind of dumb and used "Bafang" as my keyword. This brought me to a bunch of sponsored results for motor kits in the four-digit price range, and made me think that this project was not actually feasible. Sticking with it, I did some more research and came back with a more specific search query: "BBS02." Now there were identical kits in the sub-$500 range, which is exactly where I wanted to be.

You want to try and buy from a supplier who has been around for a long time. Look at the "Open since" in their store info, and also the number of units sold.

I find that the "Detailed Seller Rankings" are not terribly useful on their own, but reading the reviews can help find some common threads if they have abysmal customer service or you should expect unusually long wait times. Sometimes reviews are bad for reasons outside of the seller's control.

My shopping took so long that I ran into an AliExpress summer sale. On top of a reasonable discount, this sale handed out big coupon codes if you purchased over $300 in stuff, which netted me in this case a $55 coupon. The platform has sales basically all the time, but some of them are much bigger than others. If you load the phone app, you sometimes get different sales. If you open the app and get a screen telling you that a big sale is coming up in a few days... wait for that sale.

For the Bafang stuff, I quickly determined that all of the Chinese sellers were likely drop-shipping out of a US warehouse, and not out of inventory that they themselves owned. This is a common pattern on AliExpress for more expensive items, and it can work in your favour for fast shipping, especially if you pick a new seller who is desperate to build good reviews early on. Yes, I realize this means ignoring all the good advice I just gave you. Such is the nature of deals.

Knowing that they were likely middle-men, I ordered from a relatively junior seller, "Deruiz Bike Store," with very few sales, and only about a year of history on their account. This motor was the cheapest one that I didn't feel sketchy about on AliExpress, and before a coupon it was about $30 cheaper than any other store's. I missed out on an even cheaper one at one point, as I decided not to buy one night and returned the next morning to find the price had been raised by that exact seller.

After a week of not shipping it, Deruiz came back over AliExpress chat and (slowly) asked me to pay more money for a unit with a different screen, because they were out of the cheap one. I gave them a couple more bucks through the platform, and had a tense moment about whether or not AliExpress would automatically refund the first order for non-shipment. Grabbing it off eBay from an established seller would have cost about $50 more, and I think I would rather have done that than have this little bit of extra "will-it-ship" anxiety.

Initially, I got a FedEx tracking number that reported it would be a 36kg package – that seems a little heavy for just a motor! Then about a day later, they sent me a DHL Express number over the AliExpress messaging system, which never resolved to anything. Then, the FedEx package was recorded as damaged and returned to the sender. Then, I got a third tracking number in my texts, again from DHL. This one finally burped up some customs documentation claiming it contained "ELECTRIC BICYCLE MOTORS," but it cost me a little more money in duty and clearing fees as well.

Most packages I've dealt with on AliExpress go much smoother than this, so I wonder if it is some kind of trick to make on-time-delivery stats look better to the AliExpress system.

Arrival

Eventually, the third tracking number started to do something. It promised a delivery date and then lived up to that delivery date: a ratty DHL Econoline pulled up at the very end of the day and dropped off a heavy box.

There's a lot of stuff in here. An initial eyeballing revealed, at the very least:

• The motor;
• Crank arms;
• Chainring and chainring cover (thin powdercoated metal – a Lekkie Bling Ring may be in the future;)
• A clear-lensed light of some kind;
• A sticker claiming that the motor only makes 350W, constable. It's for you to place over the label on the motor that states it makes 750W;
• The screen;
• A bunch of wiring that I'm not sure where it goes to. Some of it has sticky pads for mounting and magnets. They're probably reed or Hall switches for brake controls;
• A ton of zip ties.

This is gonna be fun!

Keep in mind that Deruiz did something really risky here. To AliExpress, the only package that I "received" was the FedEx one that got destroyed. I was fully within my rights to claim package non-delivery and get a full refund, especially since the tracking number they provided was not addressed to me at all, but I decided that would be bad karma. I have, however, gotten expensive items for free on AliExpress for late or temporarily lost shipping. It is not at all in the platform's interest to tolerate sellers who don't have their poop in a group.

Spin to win

Now that I have the motor, the real fun can begin: shopping for batteries. I have some good ideas in mind for places to source safe-but-beefy packs, but a lot is going to depend on what I can mount with this somewhat unusual soft-tail frame. More on this soon, I hope. Thanks for reading!