《220蚊收個車架，最貴嘅收穫叫「心裡有數」》A 220-Dollar Frame: What I Actually Bought Was Knowing the Score

[Zheng Ge's Take]

The idea came out of nowhere: buy an e-bike frame and rebuild it myself, one step at a time.

Two hundred and twenty, and stripped to the bone

I have been fixing bicycles for years, so I know my way round one well enough. An electric bike I had never once taken apart. Then I saw someone selling a complete frame that still ran, asking a bit over three hundred. I offered two hundred. He said yes, and threw in delivery. We rented a battery to go with it and I went along with him to hand it back, just to be sure the thing actually ran; in the end I took it for 220, which is cheap, and left it downstairs.

Whenever there was a spare hour I went at it. Off came the delivery box. Off came every part that did not need to be there, until the frame was bare. The underground car park was hot and thick with mosquitoes; crouched over the thing I was soaked in sweat and out of patience. Then I got a bit smarter: I stopped trying to finish in a day. Strip it over two days, wash it down properly, and then, while nobody was home, straight into the lift and up to the flat. Ten minutes when I had ten minutes. Half an hour when I had half an hour. Slowly, slowly.

The plan was simple: just get it moving

A new 60V30A battery is six or seven hundred at the very least, and that is silly money for the sake of finding out whether a frame works. I already had a 48V battery at home. So the plan was to change the controller and run the old battery — take the cheap road round.

A repairman near me was letting a controller go for 20. I drove three kilometres at one or two in the morning to collect it. At the time I assumed it would be a few wires and done. I bolted it on, connected the power, and the bike did not move a millimetre.

Then the real work started

I decided the controller was dead, took it back and swapped it. Bought another one online, fitted it, still nothing. Read the tutorials, asked around, checked the wire order, went round the loop again. Several controllers later it was still throwing a fault, still reporting a throttle error.

Everyone I asked said the same thing: it is the throttle. And then it landed — the one detail I had been walking straight past the whole time. I ordered a new throttle on the spot. The courier had not reached me, so I went to collect it myself, came back without eating, and fitted it.

One plug. One turn of the key. The bike moved.

What I actually learned

On the surface this was a 220-dollar bargain and a small tuition fee paid in parts. What I actually learned was a way of working a problem from zero: the power supply, the controller parameters matching, the throttle signal, the brake cut-off, the phase wires, the hall-sensor loom. Each one in its order. Never by guess, never by feel.

Years ago I was charged 160 to have a tyre changed. The same tyre is thirty-odd online, and the job is about as simple as a job gets. The biggest gap in this world is not labour. It is information, and what a person understands.

Learning a thing was never about taking the work out of somebody else's hands. It is about giving yourself a choice: if I pay someone to do it, I pay gladly; if I do it myself, I know the score and I stand on my own feet.

How I go about a thing

Everything in this world runs on the same rule. Do not take a thing on hearsay. Do not believe it because everyone says it. Take it apart with your own hands, check it with your own eyes, understand it with your own head — only then is it yours.

And never in a rush, never the whole thing at once. Break it into steps, work through them one at a time. That is the only way down to the root of a problem.

Where the line is

Let me be plain about one thing: this frame of mine is for study and for practice. It is not a vehicle. It does not go on the road — not the road, not the pavement, not any public place. In Hong Kong machines like this are generally not allowed on roads or pavements however well they are built, and the position differs from place to place; I am not going to assume it falls my way where I live. The build still has to be right, and it still has to be safe: 48V/60V matched, controller parameters that agree with each other, a loom properly secured, brakes that actually stop it, the battery fixed in place, no short circuits anywhere. "It runs" is not the standard. "It stops, it holds a line, nothing shorts, nothing burns" is. All of that is so the thing is sound standing still and safe to take apart — not so that it can go out.

One line to finish

The frame was 220. The tuition, the nights, the patience it cost — all of it came back as four words: knowing the score. That kind of clarity was worth every bit of it.