New to ebikes and this forum

[Skyblade]

Hi, I'm very new to this scene and I'm not sure if what I'm looking for in a ebike is within line with most of you here. I currently have no ebike but I'm interested in making my own conversion to a ebike. I have a voodoo canzo MTB (not a great or expensive bike I know) this is what I want to convert to a ebike. It will never be used on the road (ever!) It will be a pure hill/ cross country bike, some of the hills I climb are very steep and looking to take advantage of the ebike to help get up these (usually end up getting off and walking).
I'm hoping to come here and get some advice on building my own ebike and what I need to get (what components are best for my needs). I'm totally new to this and any help would be much appreciated.
Looking to build something a bit more than average on the power side. I was to thinking somewhere in the region of 3000w - 5000w motor (providing it will fit within my rear dropout) with 72v battery and a decent controller to go with it.

Any advice would be superb, thanks

 

[Nealh]

Best advice is don't do it with a crappy ali bike frame.

 

[vfr400]

For off-road hill climbing, you need a crank-motor, not a hub-motor. You need to explain why you need that much power. The weight and size of the battery will work against you. Also, you couldn't have chosen a worst bike for conversion regarding the gears. Your rear gears won't fit on a 3000w hub-motor and it doesn't look like you have enough clearance for a decent sized chainring. Your frame will probably fold if you try and put 5kw through it.

You'd be better off getting something like this, then maybe replace the battery and controller as necessary:

Alibaba.com

www.alibaba.com

 

[Skyblade]

I don't want a motorcycle looking bike, I need a hub motor as I 2ant to be able to put the bike back to stock with ease just leaving wires in place and just removing the rear wheel, controller and battery. The hub motor needs to be powerful enough to power me up some pretty steep hills consistently using the bike I have even if it means getting a reduced rear sprocket or something. Is it possible that I could use a lower power motor to achieve what I require?

 

[vfr400]

You have a bicycle with low gearing. It's designed for pedalling up hills with an average power input of about 200W. You can put any 250W to 500W geared cassette hub-motor in the rear I'd you use at least one torque arm and maybe file the drop-outs a bit deeper. If it's climbing ability that you need, choose a 201 rpm version, which will give a top speed of 15 mph.

The first problem you need to overcome is where and how you're going to Install the battery.

 

[Skyblade]

I would like to have a bit more top speed than 15 mph as I can pedal faster than that already, the battery I don't have a issue if I can't fit within the triangle I could put on main cross bar or if it really came to it I'd get a rear mount over the back wheel. There are multiple places I could fit it unless I'm missing something here? Are they bigger than a car battery?

 

[Skyblade]

I'm basically after the most possible power and speed I can get away with on this particular bike

 

[vfr400]

You have full suspension, so how would you mount a battery over the rear wheel?

Your triangle looks to be too small for a standard battery.

On top of the crossbar looks tricky to me because it isn't straight. Even if you could mount one there, it's too high and will compromise the handling of your bike. Every time you take it out of the shed, it'll try to turn upside down.

You'd have to make or buy a battery that is the right shape to fit in the bottom of the triangle. How much are you prepared to pay for your kit?

 

[vfr400]

Sorry, Google fooled me with the wrong picture of your bike. You might be able to fit a standard triangle battery in a bag at the top of your frame triangle. Em3ev make some nice ones. You can also find them on Aliexpress, but I'm not sure pf their quality. Check sizes.

Once you have the battery sorted, you can work from there.

 

[Skyblade]

I'm prepared to pay as much as needed, if I need to make my own battery then that's what I will do. I need to start somewhere so if I need to make it work I will. There is a rear frame that sits on the back swing arm, I just need to make sure it will clear th seat when the suspension is fully depressed but this is not ideal. I think making my own batteries would be the way to go. The rear forks on this bike is I think 141x9mm Boost Open QR, I think this is going to be my main issue, what size is the biggest motor I could fit in this space?

 

[vfr400]

141mm is better for a cassette motor. Most are around that size.

You need to be more precise about what you want to do with the bike. How heavy are you? How steep and how long are the hills? How muddy is it likely to get? Hub-motor can be like tractors or racing cars, but not both from the same motor.

 

[Skyblade]

I'm 100kg at moment, I'd prefer top speed over climbing as I have very low gear ratios at present (probably a little to low), the track I run on has a few hills that are fairly steep but there only short there is a run that's around 1.9 miles of straight gravel stretch with a slight incline, it's this part I want the bike to go up at a fast speed as it's a little boring on that part. Most of the other parts the motor will just probably help to keep it going or am I looking at this wrong?.

 

[sjpt]

I don't think we can say it's wrong, though very different from the way most people here are using their ebikes.

Strictly its not legal if any of the tracks or paths you go on are public rights of way. You are unlikely to get caught, and its not really an issue as long as you are polite to other people and give way to pedestrians where appropriate.

 

[Skyblade]

Its part public and part private as it passes through farm land (we already have permission to venture on this land as my friend owns part of it). The parts that are public we obviously are very courteous to the people using it ( usually other bikers).

 

[vfr400]

I'd go for a 48v Q128C motor wheel from topbikekit. Select the 260 rpm one version. You'll have to build your own wheel, as no kit supplier does rims like yours.

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Choose their 20 amp sinewave controller and install it in an under-saddle toolbag. You can choose a throttle and pedal sensor. Avoid any 12 magnet pedal sensor. Choose the LCD3.

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Without knowing the size of the space in your frame, I can't help with a battery, but any 48v one that can supply 25 amps continuous should be OK. Have a look on Aliexpress for triangular ones. You can buy just the triangle frame bags for the battery. You might be able to find a rectangular cell-pack that fits in there along with the controller.

 

[Benjahmin]

Or you could make a cardboard template, have a triangle bag made from it to your spec, then send it to Jimmy at e-bike batteries and get him to make one. It'll be far superior to anything you can achieve and have specified known maker cells capable of delivering the max continuous current you need.
Do not be woo'd by Kw wattage figures on hub motors. They're all direct drive, highly inefficient at low revs (ie hills) unless you want a mobile heater.
The Q128 that Vfr has suggested is a well known and much used geared hub. 260 rpm seems to be the sweet spot between speed and hill climbing torque.

 

[Skyblade]

So would it be better for a geared hub, is the other type a direct drive? What's the advantages and disadvantages of each if that's a thing?

 

[Woosh]

a geared hub is like a direct drive + a reduction gearbox.
The Q128 that vfr told you about has a 10.5 to 1 reduction gearbox, that is the torque of the wheel is 10 times stronger with the gearbox than without. It's excellent for climbing.
https://www.aikema.com.cn/en/product/high-torque-500W-rear-wheel-hub-motor-for-electric-bicycle-conversion-kit.html
The reverse side of the coin is the maximum speed is limited.
Only a crank drive lets you use the power for climbing or for speed.
You should really try a ready made e-MTB before building yourself a powerful e-bike. You could end up spending £2k on a heavy lump that sends you flying at the first jump or breaks or burns the house.
This section of the forum is for road legal bikes. You can of course apply for registration to make your bike legal.

 

[Skyblade]

Ok so been doing some research on hub drive motors and mid drive motors and I've come to the conclusion that mid drive is going to be the way I need to go regardless of the fact that I probably won't convert it back to a normal bike after its built. One thing I want to ask is that do mid mount motors have a free wheel option? I.e if no battery is on the bike can I still pedel with ease or will I be pedeling against the motor?

 

[Woosh]

? I.e if no battery is on the bike can I still pedel with ease or will I be pedeling against the motor?

yes.
All geared hubs and bottom bracket motors have inbuilt clutch.
Your main issue is the trade off between weight and power.
Don't worry too much about the 250W label. It's for flat road at 15mph.
The real power at the rear wheel is a lot more than what the label says.
For good handling, you need to keep an eye on weight. I'd say under 23kgs.
Bottom bracket motors are not really as good as a factory built e-mtb because the power twists the frame.