Building a bike for heavy hill climbing on country roads.

[Ash21014]

After the throttle simply broke off my Sirocco CD leaving me lying in the middle of the road I have decided now is the time to get round to building my own custom ebike, in this coming year

After coming to the realisation that no one has even heard of an ebike, I'm willing to forgo minor legalities on throttle, speed limits and motor power restrictions. And with proper outdoor, insured storage for my bike meaning I don't have to carry it, I'm not as bothered about the weight, though obviously I'd still prefer less where possible.

Since my experience with my previous bike on the country/non-well maintained roads was that it makes for bumpy rides at times I'm looking for base bike that is really durable, with tyres suitable for wet dirty roads and the occasional sand or gravel drive, and maybe a suspension to help adsorb the shock of sometimes poorly maintained roads. Comfortable seat too, comfort and handling are more important to me than performance.

Gearing, I'd like to be as simple as possible, the single piece chain-set with a handful of rear sprockets seemed to work well enough, save for the fact that 7 sprockets on the rear was more than necessary and I found myself only using a few of them regardless of road and weather conditions, gears 1-3 were never really used.

I have a 48v 12Ah battery, the capacity of which I actually verified personally because of how many manufacturers overstate their capacities. Because of the hills I definitely need a crank drive motor, I was thinking maybe in the 48v 350W range? And I'm not sure what controller to get or sensor, the rotational sensor on the CD was kind of like using the throttle, all or nothing, and I think I'd like to try a torque sensor so that I get a greater workout and can more easily navigate pedestrians on shared cycle path areas.

I have two 1000 lumen torches as headlights, don't know whether it's better having them independent or connected to the battery to save charging them every night. I want a couple of bright rear lights too of course, but I'm not sure where to go for that.

Any advice on where to start would be appreciated guys, I'm fairly green to bikes in general, never mind electric ones, I'm having to learn a lot fast!

 

[D8ve]

Independent power for your lights and try hub gears.

 

[Deleted member 4366]

Why do you say you need a crank-motor for hills? You shouldn't limit your choice at the beginning. You need a motor with enough torque to get you up the hills. There's hub-motors that can get you up your steepest hill at 30 mph if you want.

If you reduce your number of gears, a crank-motor is even worse. The whole point is that they can use their power through a wide speed range of speeds by using the gears. A hub-motor has a much wider speed range that means you can go down to single-speed if you want. Better still is the Xiongda 2-speed motor. It can match a crank-motor for torque in low gear and can still reach a maximum speed to suit its power. It's probably the best motor if you want a limited number of gears.

 

[Ash21014]

The reason I say crank motor is because I've been told they produce a lot more torque at the same power output level than a hub motor, which can overheat when going up hills. I know you can get hub motors that will take you up a hill at 30mph but I don't want a motor with a large power output with the performance of a moped.

As for gearing, in the past I've experienced problems with changing gears and thought that with less gears there's more margin of error when changing gear which would make it more reliable.

 

[trex]

8-Fun BBS02 48V 18A 500W would be a good match for your 48V 12AH battery. It's twice as powerful than the 36V 15A 250W Woosh CD motor that is on your Sirocco CD.

 

[Ash21014]

You see the thing is I don't think I need that much power, the 250W motor was perfectly adequate, it'd be nice to have a bit better performance like a 350W motor but I think that 500W is pushing it. I only weight 64kg after all!

 

[trex]

you don't have to push the 500W motor, but the power is there when you need it. The 500W motor is only a little heavier.

 

[JamesW]

Don't remove the extra gears. I have the experience of electrical connectivity failure when halfway through a ride and know full well that you need to be able to cycle some way at least with the gears that you have - even if it's only to get some movie reception to call for help!

 

[MikeRo]

It sounds like you may be confusing power and torque, Ash. Simply, power= effort x flow. For electrical side, power = current x voltage. For the mechanical side, power = torque x speed.

So at a given speed, a higher power motor has more torque than a lower power motor.

The advantage of a crank drive is the torque multiplication effect of gearing, but at the expense of road speed.

 

[Deleted member 4366]

The reason I say crank motor is because I've been told they produce a lot more torque at the same power output level than a hub motor, which can overheat when going up hills. I know you can get hub motors that will take you up a hill at 30mph but I don't want a motor with a large power output with the performance of a moped.

You shouldn't believe everything you've been told. Many people that spout these misconseptions have very little experience of the different motors that are available. There's many light-weight hub-motors that can produce a lot of torque without over-heating. I weigh nearly twice as much as you and encounter hills of 30% and more on my rides. Like you, I thought that crank-drives would be the best solution, but I soon found that they're not. Their disadvantages outweigh their advantages.

A code 14 Bafang BPM doesn't weigh much different to a 350W BBS01, but it'll give a lot more torque - not that you need that much torque.

If you're good at DIY, the Xiongda would be perfect because it's light. You don't get any of the gear-changing problems with a hub-motor. The torque of this one would allow you to stay in top gear all the time if you wanted, since it has enough torque to get you up a 1 in 4 hill without pedalling if you want. The LCD allows you to turn the power down too, so it's no moped.

You've already tried a crank-motor and found shortcomings. When you get a more powerful one, the shortcomings become worse. I'm sure you can imagine your crunching gears when there's twice as much tension in the chain. I tried a Nuvinci CVT hub with my crank-drives to eliminate the problem. It worked quite well, but then you've added another 3kg to your bike, so no advantage over a big hub-motor, which is just a lot more relaxing to ride. By relaxing, I don't mean lazy. I mean free from hassle.

 

[Ash21014]

How does having a hub motor effect the wheel that can be used and changing a tyre?

 

[Deleted member 4366]

It takes about 2 minutes longer to change a tyre, but how often do you have to do that? Tyres last about 1500 to 2000 miles on a rear drive (crank or hub) and about 500 to 100 miles on the front, which is one reason you should avoid high torque front motors if you can. With your light weight, you can probably double those mileages.

 

[RobF]

A lot of kits come with the motor built into the wheel, so you get what you get.

I lack the knowledge, patience, and will to build a motor into a wheel - it's quite an ask for someone new to kits and my suggestion is don't try it, although you may have all the qualities I don't have.

Changing a tyre should not be complicated, the electrics unplug via a single multi-connector, usually cable tied to the chain stay.

One point to bear in mind is you will have a solid, nutted axle, so no quick release.

Fine in the workshop, but it means carrying a spanner on rides.

A rear wheel motor denies you the option of a hub gear, but you could have one of those if you put the motor in the front wheel.

 

[Ash21014]

So what would you guys recommend as a rear hub motor for my use case then?

 

[Deleted member 4366]

How fast do you want to go?

 

[Croxden]

How fast do you want to go?

That sounds like the American Express joke.

 

[Cyclezee]

You shouldn't believe everything you've been told.

Especially on the forum

 

[trex]

they are just trying to confuse you.
Power applied to hub = risk of breaking spokes,
More power to the hub to climb your steep hills increases this risk.
the bad road surface makes this risk into a near certainty.

 

[Deleted member 4366]

they are just trying to confuse you.
Power applied to hub = risk of breaking spokes,
More power to the hub to climb your steep hills increases this risk.
the bad road surface makes this risk into a near certainty.

Sorry Trex, but that's just total ball cocks.

You come on this forum telling everyone to buy a Woosh Big Bear believing that they're all going to be condemned to disappointment when their wheels disintegrate down the road?

People on Endless-sphere put Hubzillas and Cromotors in their bikes with ten times the power that we see here. I don't remember any of them reporting broken spokes.

 

[trex]

...

People on Endless-sphere put Hubzillas and Cromotors in their bikes with ten times the power that we see here. I don't remember any of them reporting broken spokes.

of course they do. But that does not change the common observation that broken spokes affect mostly rear hub motor wheels. People who use hubzillas on ES are also very experienced builders.
I believe that crank drive bikes are easier to maintain and statistically require less maintenance.