DIY makes your electric bike yourself - step 2/5: assemble the engine and the bike disc brake
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| 2: Placing the engine on bike |
In theory any kind of between 150 and 1000W motor could be used (or more, but put more seems unnecessary and dangerous), with or without brushes, etc, but if we think much use bike, is better to spend more on a good DC Brushless motor (BrushLessDdirectCcurrent BLDC) which will last us as long as the own bike (while not burn due to overheating)Since the only mechanical parts, bearings, last almost forever and can be changed if necessary.
Brush motors have the advantage of being simpler to manage (does not require an electronic controller), however require greater maintenance to bring parts that wear out (brushes, and gears if they have).Among the BLDC have small engines from 250/380W gears to increase the torque, its gears are usually nylon and after a few thousand km. often fail (although they can get spare parts from metal). These motors are recommended for people who used the bike for walks, and for having one helps with small slopes; they are small and cheap.
Is always better on a bike a BLDC motor without gears for the following reasons:
- They are the most efficient (up to 97% efficiency).
- Very good power-to-weight ratio.
- Very low maintenance.
- High acceleration (there is nothing mechanical limit it; the limit is usually electronic).
- Controllable speed with precision.
- Low noise in operation (only a soft rrrr at low rpm).
I chose the Prokit 901, a kit composed of RIM GoldenMotor motor brushes 500W, controller, manetas (right with bike throttle-type), and a couple of switches for the Horn and cruise.
This engine runs about 30 kms/h with 36V, and according to the specifications we can feed the Prokit 901 with up to 60V; I can't imagine how fast he could go with this voltage!
A US Editor did put it at 120 km/h!. That Yes, theoretical vacuum, 1050 RPM. and running to 72V I guess.
Riding the rim with bike engine
The Prokit 901 brings a BAC-281 controller 50A peak (30A continuous) which is fine, because it can also run without hall sensors (in case one fails), in addition to bringing speed control cruise, Horn, etc, although its setup by PC program brings few modifiable options.
But Let's get to the topic of engine kit, because to try it need to place on your website (or locate the shaft safely to avoid damage to the wiring).
It must be observed that the tire does not come with pine nuts, so you have to buy a set of sprockets of 7 changes (a thread); in the shop can place you in a second, simply screw the set and is already fixed.Also it is ready to put disc brake, but very little space for it, as we will see.
The shaft is flattened so it fits and it unable to turn (if it did the cables will be damaged since the stator where goes the armature should remain still while tour abroad or rotor, where are the magnets and that is attached to the spokes), and had a little more as the hole in the support, so I used the dremel craft with a grinding wheel stone cylindrical to abrade the faces where he was housed until well enter a little small.
Bring lock washers with a side stuck to clamp the shaft to the picture, but as in this picture, it did not coincide with none, modified by flattening it and a small squadron of stainless steel welding. Thus, it continues to play its role, which is that if you loosen the wheel nuts, not is leave your website.
Taking into account the strength that can make this motor, all security is low.
And so it would be on the side of the brake disc (even loosely):
Place camera and tire
First of all, it is convenient to put the camera and the old wheel tyre:
We are introducing the camera on your website first putting the valve in its hole. This is a reinforced rim, so valve protrudes just 1 cm, and even can be a stopper uncut half. It is advisable to put a washer to secure the valve in place and that no can twist where the tire pull to the side (as usually wear narrow Chamber as the cycling valves). Anyway, to avoid esto we must remain always well inflated wheel since it could only occur if little inflated and we exert too much force on the wheel (which the engine can pass).
In the absence of tools, I used spoons to fit tire, since they have killed edges and do not constitute any danger nor tyre camera:
To finish will we inflate the half wheel and slip on the floor to verify that all sides of the tire are well embedded in the tire, and we ended up inflating until the correct pressure.
By placing the disc brake
With the weight that takes on the bike, and at speeds which we could reach, the most advisable is to replace at least one brake pads by another disc and pads for longevity and reliability, if we want to be able to stop in walking distance.
I have opted for one of the cheapest cable, but if you can, better place one hydraulic with disk without perforations (wears more pills and I see it unnecessary unless let's us to descent).
The downside of this engine is that it occupies part of the space normally reserved for the mechanics of the disc brake, and after placing in the box brake, this hit me on the top of the engine (perhaps only this model, carrying pills fast switching on both sides), and I was forced to cut the shaft pressing the pad inside the limit without that prevents normal operation, although the rapid change of PADS is perhaps cancelled (forcing to release the handbrake to do so).
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| With a file or grinder with cut-off, I carefully cut stub shaft that stood out |
In the picture below you can see just who is the lid brake.
Also the position of the pads was so foreign that he barely touched disk abroad, by what I had to eat a side of positioning washers (the Interior) so that the pills made contact on the entire surface possible braking:
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| The brake already installed and running; with the black nut we regulate the voltage |
On the other hand, Let excess cable that goes to the engine, so that in the event of a puncture, not be us just that when released (in my case by cutting the flanges of electrician that subject it) it is not us room for manoeuvre to take the wheel of your site to access the camera.
I recommend placing a little silicone on the dock where out the wires from the inside of the shaft so that it cannot come water out there.
Technical details and operation
The 901 Prokit brushless 500/1000W handles from 24V to 60V, and has 46 neodymium magnets permanent on the wheel (rotor), with 51 Pole on the shaft (stator).
In the example in the photo, the Poles are copper and magnets are small grey rectangular segments from the outside, with 3 Hall sensors that detect the position of the wheel by monitoring a magnet that passes close to the sensor.
As shown in the image below, the Poles are in groups of 3, with the central pole winding in the opposite direction to the other two. The magnets alternate polarity, in a way that when current passes through the first group of Poles in one direction, the following Magnet attracts and repels the previous one, resulting in the movement, which perpetuates the alternation of phases. If you look at the colors, red, green and blue, each color is a phase, current circulates counterclockwise at every stage, the driver, according to the position indicating the Hall sensors (placed 120 degrees most of the time), alternating current phases, more quickly the more revolutions per minute turn the wheel and activate only two phases in every moment (you can see it better in this video )).
The driver the MOSFET transistors control the direction and amount of this current, therefore they regulate power and rotation of the wheel according to the position indicating the Hall sensors. Depending on the driver, there may be two MOSFET or more controlling each phase (depending on the power of the same), half controlling the positive and half negative. One hall sensor detects when a magnet is close, sending a signal to the micro-controller to activate power (MOSFET) transistors, controlling the flow of electricity and address.
More electricity magnetic field is stronger, so it increases the strength and speed.
Higher voltage means more current, this is so higher voltage means greater top speed (RPM).
Drivers are (such as the included with the prokit 901) that they can also work with damaged or non-functional sensors determining position by measuring the electricity that induce the magnets on coils with the movement. This function requires that the motor is in motion, for we have to start moving us to apply force, and unless the driver is quality, precision is less than with Hall sensors at low speeds, so the maximum power and speed down slightly.
In the example in the photo, the Poles are copper and magnets are small grey rectangular segments from the outside, with 3 Hall sensors that detect the position of the wheel by monitoring a magnet that passes close to the sensor.
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| A similar engine without cover image (changes number of Poles and magnets) source |
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| Source |
More electricity magnetic field is stronger, so it increases the strength and speed.
Higher voltage means more current, this is so higher voltage means greater top speed (RPM).
| Hall A | Hall B | Hall C | Red phase | Blue phase | Green phase |
| 1 | 0 | 1 | NC | V DC- | V DC + |
| 1 | 0 | 0 | V DC + | V DC- | NC |
| 1 | 1 | 0 | V DC + | NC | V DC- |
| 0 | 1 | 0 | NC | V DC + | V DC- |
| 0 | 1 | 1 | V DC- | V DC + | NC |
| 0 | 0 | 1 | V DC- | NC | V DC + |
Drivers are (such as the included with the prokit 901) that they can also work with damaged or non-functional sensors determining position by measuring the electricity that induce the magnets on coils with the movement. This function requires that the motor is in motion, for we have to start moving us to apply force, and unless the driver is quality, precision is less than with Hall sensors at low speeds, so the maximum power and speed down slightly.
Getting more power from your engine without frying it
Public enemy n ° 1 of any electric motor is the temperature. In addition, the power of these engines is only limited by the heat generated. There are controls such as the Kelly including the engine temperature sensor, although for placement this kit it would require opening it and modify it by adding a couple of thin wires of the phases and hall and sticking a probe on the stator.
When climb the Hill to my house the engine temperature is healthy, you will need approximately 30 ° C, but I am concerned that a route by endless slopes you can fry it, so I will raise that modification should do similar routes with it.
A 500W motor can give that power for brief moments, but not all the time because it could burn, since the main beats bike engines is the poor ventilation not being able to put any kind of fan (although Yes might result put some kind of aluminum heatsink; a disc around the interior in such a way that turning the rotor heat eliminates)cooling the whole work).
A summer storm being the bike on the street (34 l/m2 in a few minutes), a real shower for bike fell yesterday morning. Luckily as he had sealed with silicone those sites by where the water could seep, and in the box left well sealed at the top and opened by the bottom so that the little water that might seep out freely and do not accumulate.
It is for situations like this that I do not recommend to do air vents engine lids, but well seal with silicone, which can be removed in case of maintenance.
Although a motor with ventilation and some liquid oily guard against corrosion could give good result, since rarely use it with rain.
Well, that is all for now on the motor; in the next entries, we will see how to mount the battery box so light and strong, will analyze the different drivers available (depending on what you want to complicate life) and will schedule a Kelly, to finally analyze the things that can be improved and the general feelings of this project. Have fun!
Well, that is all for now on the motor; in the next entries, we will see how to mount the battery box so light and strong, will analyze the different drivers available (depending on what you want to complicate life) and will schedule a Kelly, to finally analyze the things that can be improved and the general feelings of this project. Have fun!
