Planning my first build, lightweight + 1000W double-torque

Desired max speed: 30 MPH under hard pedaling
Desired range: 15 mi @ 20 MPH
Donor bike: Touring road bike
Desired bike weight after conversion < 40 lbs
Desired brake type: Disc
Rider weight: 185 lbs
Terrain: Mostly flat with occasional steep hills of 20%+ grade
Budget: ~$1,200

I bought my first Ebike a few weeks ago and have been enjoying the imperviousness to wind and inclines. I was riding a pedal-only Brompton every day for 13.5 miles with some gnarly San Francisco hills, and my knees, hips, and lower back were not happy about it. I picked up a used X-Treme XB-300 Li and found it to be a huge help, but soon wanted something significantly lighter and more powerful. I realize that these two characteristics don't usually go together, but I have my reasons.

I would like to build a bike that is as close to 35 lbs as possible, as I believe that is the max weight I will be willing to carry up a flight of stairs on a daily basis. The XB-300 is about 55 lbs, so I have been locking it up outside in some very shady neighborhoods, albeit in daylight and for short periods of time. I'd like to stop doing that and also quit lugging around the heavy U-lock everywhere I go.

I would also like to be able to hit 30-35 MPH with the motor doing its work and me adding another 300-500 watts pedaling. This is because bike lanes in SF are not respected and are frequently blocked. Some streets don't have enough clearance to ride separated from traffic without getting doored. The XB-300 travels too fast to exploit a gap in traffic without having to slam on the brakes but is too slow to merge into the traffic lane without getting run over. I need something that can quickly get up to traffic speeds so I am not stuck waiting for a long line of cars to pass every time an Uber driver decides to block the bike lane (ie constantly). I'd like to be able to do 35 since a lot of drivers reflexively speed up and try to cut off cyclists who are merging into their lane ahead of them.

For a donor bike I was thinking something along these lines: http://www.bikesdirect.com/products/gravity/disc-brake-road-flat-bar/avenuefxd-disc-brake-bikes.htm

It would be sufficiently light weight, has straight bars for comfort, disc brakes, and a CrMo steel fork. I would swap out the gears for a Shimano Nexus or Alfine IGH. I got used to an IGH on the Brompton and don't want to deal with derailleurs anymore, although I might leave the one up front.

For a motor and battery, I was planning on the Double Gear / Double Torque with the 52V Mighty Mini 30Q with the motor on the front wheel and battery in the back (perhaps on the seat post but not married to that idea). https://lunacycle.com/double-gear-double-torque-motor/

Custom options would be the DM24 700c rim, Luna twist throttle, torque arm, and 300W charger.

Am I on the right track here, or will I run into unforeseen problems with this build?

It is not with 1000w that you will accelerate cars, especially up the steep hills of SF.

If you want light weight and acceleration power, you need a mid drive and not those BBS type. You have to build your own, or buy an expansive one, that will give you acceleration power without shifting through a set of gears. I guess 5 to 7Kw would do it.

I don't need to match car acceleration uphill, just to be able to get up to speed on flats and get up steep hills at a low speed.

That does beg a good question, though: What is the acceleration like with 1 kW hub motor including pedaling? I can already get from 0 to 10 MPH faster than most drivers without a motor (if they don't have a lead foot), so I imagine that standing on the pedals and cranking the throttle will yield similar acceleration to the flow of car traffic, but maybe I'm overestimating the power of 1,000 Watts.

You can climb 20% with 1000w hub motor but it would have to be in a small diameter wheel. Otherwise, heat will build up quick in both, motor and controller. A BBS type mid drive would do it, but to gain speed on the flat you will have to shift through a set of gears.

Both will accelerate much faster than a fit cyclist, but both are much slower than cars.

S.F. go check out Ilia at ebikes.sf and go for a test ride. After that some answers will answer themselfs. Your first ebike is Bargain Basement.

I saw that double torque 2 Speed Motor I'm wondering which one it is or how it really works in real life performance

That motor lookslike the Xiongda 2-speed that I have on my bike. You can just make out the XD marking. Assuming that it's the same as mine, maximum speed is about 23 mph at 48v. The 36v one at 48v runs slightly faster at about 24 mph, though it doesn't seem to be as efficient as the 48v one.

There's one complication with these motors. They're a bit wider than a normal one, especially if you have a disc brake. You have to stretch your frame a bit, which is no problem, but to get the rim cenral, you need to either go wider and fit a spacer in the left side, or build a substantial offset (dish) in the wheel, which can cause spoke problems. The spacer method is OK forrim brakes, but for disc brakes, the caliper won't line up with the disc, so you need additional spacers behind the caliper adaptor.

The main advantage of these motors is their winch-like climbing ability. They wouldn't be the best choice if you don't have difficult hills.

The front version without disc brake fits normal 100mm forks, but if you fit a disc brake it's too wide for normal suspension forks because they can't be stretched, but OK for rigid forks provided that they're not too rigid.

My current Two Wheel Drive 1000 watt Electric Bicycle easily meets all but one of your Desires. Desired bike weight after conversion < 40 lbs. I use 32 pounds of batteries alone to have enough reserve to overcome the wind resistance at 35 mph. The amp draw on just the rear motor at 35 mph is around 35 amps with the wind the steep hills and no peddling. I usually need Both 1000 watt motors to climb the steep hills here. I have seen pictures of the hills where you live. They are similar to the Very steep roads here.
The motor you are selecting is NOT going to work with the load you want to move. 20 amp controller?
I do not even like the cheesy torque arms . Hose clamps?

Under 40lbs. Never happen. Under 70lbs. Easy for under $700. See sig videos. I weighed 270lbs when they were made.

d8veh said:

That motor lookslike the Xiongda 2-speed that I have on my bike. You can just make out the XD marking. Assuming that it's the same as mine, maximum speed is about 23 mph at 48v. The 36v one at 48v runs slightly faster at about 24 mph, though it doesn't seem to be as efficient as the 48v one.

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So about 25 MPH with 52v and no pedaling, then? That won't get me to 35, but 30 should be doable.

There's one complication with these motors. They're a bit wider than a normal one, especially if you have a disc brake. You have to stretch your frame a bit, which is no problem, but to get the rim cenral, you need to either go wider and fit a spacer in the left side, or build a substantial offset (dish) in the wheel, which can cause spoke problems. The spacer method is OK forrim brakes, but for disc brakes, the caliper won't line up with the disc, so you need additional spacers behind the caliper adaptor.

The main advantage of these motors is their winch-like climbing ability. They wouldn't be the best choice if you don't have difficult hills.

The front version without disc brake fits normal 100mm forks, but if you fit a disc brake it's too wide for normal suspension forks because they can't be stretched, but OK for rigid forks provided that they're not too rigid.

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How hard is it to widen the front forks and fit the spacers for a person with only moderate maintenance ability? This will be my first major bike project, so it sounds like I might want to stick with V-brakes.

tiny_n_terrible said:

My current Two Wheel Drive 1000 watt Electric Bicycle easily meets all but one of your Desires. Desired bike weight after conversion < 40 lbs. I use 32 pounds of batteries alone to have enough reserve to overcome the wind resistance at 35 mph. The amp draw on just the rear motor at 35 mph is around 35 amps with the wind the steep hills and no peddling. I usually need Both 1000 watt motors to climb the steep hills here. I have seen pictures of the hills where you live. They are similar to the Very steep roads here.

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That's why I chose the double-torque motor. It seems like the only one that has enough torque in the climbing gear to help with the bigger hills, yet won't put me over the weight budget. I'd like to be able to hit 35 under hard pedaling (300-500 watts of leg power out of the seat), but I'm guessing 30-32 will probably be the max, which is fine too.

The motor you are selecting is NOT going to work with the load you want to move. 20 amp controller?
I do not even like the cheesy torque arms . Hose clamps?

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I thought everyone used torque arms with hub motors over 500 W?

Check out my BBS02 Cube cyclocross build (29er/700c rims with disc brakes). Easily do 15miles on a 52v 5800mAh lipo pack and weigh about 40lbs To hit the 32mph speed you need a 48t chainring or bigger without spinning like mad and if you want the BBS02 to keep pushing past 35mph, change the wheel diamater setting in the programming to 18". This should trick the motor to keep pushing past 32mph.

It also climbs like a goat with a MTB megarange cassette out the back ( I run a 9 speed ).

It'll do about 26 mph max at 53v in a 700C wheel.

It'll have all the torque you need for steep hills. Mine runs at 15 amps 48v, and I can easily get up 30% hills with moderate pedalling.

Stretching rigid disc brake forks to make it fit is no problem You only need something like 10 mm or less. you can't do that with suspension forks because it locks them. The motor easily fits in rim-brake forks.

As I said before, the motor's advantage is its winch-like torque for climbing. if you want to cruise at 30 mph, it's the wrong motor. Look at the 328 rpm Q100H instead.

Yes use torque arms. Hose clamps work. There's a thread about that 2 Speed Motor I don't know if it's the exact same one but maybe read up on it. Hills are tough on electric motors especially long steep hills.

It seems like the idea is not completely demented, so I'll probably give it a shot! I'll update with how it went when I get the funds together.

999zip999 said:

Yes use torque arms. Hose clamps work. There's a thread about that 2 Speed Motor I don't know if it's the exact same one but maybe read up on it. Hills are tough on electric motors especially long steep hills.

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Luckily the hills in SF are steep but very short. They all plateau into a flat intersection after each block, which would give a motor a chance to rest before the next climb.

d8veh said:

It'll do about 26 mph max at 53v in a 700C wheel.

It'll have all the torque you need for steep hills. Mine runs at 15 amps 48v, and I can easily get up 30% hills with moderate pedalling.

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Good, the steepest ones on my commute are about 25% and I may occasionally visit clients in Potrero Hill where the grades can get up past 30%.

Stretching rigid disc brake forks to make it fit is no problem You only need something like 10 mm or less. you can't do that with suspension forks because it locks them. The motor easily fits in rim-brake forks.

As I said before, the motor's advantage is its winch-like torque for climbing. if you want to cruise at 30 mph, it's the wrong motor. Look at the 328 rpm Q100H instead.

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Cruising will be more like 25 with soft pedaling, I only want to get up to 30 occasionally to briefly merge into traffic when the bike lane is blocked and I don't mind if I have to get out of the saddle and pedal hard to achieve it.

Now that I think about it, if I'm going to be carrying the bike upstairs, it would make more sense to go with a detachable battery. Even less weight to lug and without the range limitation of a Mighty Mini.

First of all, you won't be putting out 500w of pedal power at 35 mph, unless you happen to be a world champion sprinter. This is because for one, your bike is only geared to be pedaled about 25 mph, or less. ( since most of the world is not world champs)

It is possible to gear your bike for 35 mph, but 30 mph pedaling is a much more realistic goal.

So, make the bike go 35 without pedaling, easy, but it won't weigh 40 pounds.

Welcome to the catch 22 of e bikes. But its not THAT bad. Typical 500w geared motor kits with a 48v ( giving you 1000w) battery are fairly light, and can go 25-27 mph easily. This would be the Mac motors, or other similar motors easily found from US vendors. It will climb decent enough to not overheat if you are pedaling hard enough, and are not over 250 pounds body weight. You will need to sometimes find a less steep route, so you don't go less than 10 mph up the longer hills.

This might work fine with the double torque motor too, I just can't say because I don't know about the motor, what it can take, what it can't. I have not tested that type motor to destruction myself.

So what you need is just a slightly lower expectation, and you can get enough of what you need. Later on perhaps, when you don't have to carry the thing up stairs, you can make a heavier, faster, and much more powerful bike. A "flyweight motorcycle with pedals" able to easily hit 40 mph.

dogman dan said:

First of all, you won't be putting out 500w of pedal power at 35 mph, unless you happen to be a world champion sprinter. This is because for one, your bike is only geared to be pedaled about 25 mph, or less. ( since most of the world is not world champs)

It is possible to gear your bike for 35 mph, but 30 mph pedaling is a much more realistic goal.

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Yes, I figured as much. Just changed the OP specs to 30. Going faster than that on SF streets would have been dangerous anyway, but a man can dream

So, make the bike go 35 without pedaling, easy, but it won't weigh 40 pounds.

Welcome to the catch 22 of e bikes. But its not THAT bad. Typical 500w geared motor kits with a 48v ( giving you 1000w) battery are fairly light, and can go 25-27 mph easily. This would be the Mac motors, or other similar motors easily found from US vendors. It will climb decent enough to not overheat if you are pedaling hard enough, and are not over 250 pounds body weight. You will need to sometimes find a less steep route, so you don't go less than 10 mph up the longer hills.

This might work fine with the double torque motor too, I just can't say because I don't know about the motor, what it can take, what it can't. I have not tested that type motor to destruction myself.

So what you need is just a slightly lower expectation, and you can get enough of what you need. Later on perhaps, when you don't have to carry the thing up stairs, you can make a heavier, faster, and much more powerful bike. A "flyweight motorcycle with pedals" able to easily hit 40 mph.

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If I'm going to build a heavier bike later, it's going to be a monster. 2WD large DD hub motors or maybe a Cyclone mid-drive, or even both together! MOAR POWER!!

Ya need to lower your sights.

Pedaling rarely gives more than 1-2mph to top speed. This is because the motor power is decreasing linearly with as speed increases, and it is decreasing faster than your legs can make up for it, all while your wind resistance is going up exponentially. Pedaling does almost nothing in most cases (unless you have a very small motor, very strong legs, and relatively slow speeds).

35lbs is also a very hard target to meet if you want to go fast.

I speak from experience. I have an ultra-light build (19lb donor bike) with a light motor and strong legs, but at that light weight it only works on relatively flat ground. You gotta give somewhere…

Sub 40 lbs and power to accelerate cars can be done, but not with anything ready made to install on a bike. It does require fabrication skills, and the use of carefully selected components. I don't believe the OP is willing to go that route. He will lower his requirements and build with a readily available kit.

Because its San Francisco, his best possible approach for bike one would be a mid drive kit.

Can still be pretty high power, and it will out torque the geared motors.

The real catch 22 of higher power and speed is it starts taking a battery that weighs more than 8 pounds, or range is short.

Find better routes that don't require as much keeping up with fast cars is the first thing to do. Then a 25 mph mid drive bike will do er fine. You can do the steeper back way routes with a mid drive easy.

You can keep it under 50 pounds, with a 25 pound bike as the starting point.

chas58 said:

Ya need to lower your sights.

Pedaling rarely gives more than 1-2mph to top speed. This is because the motor power is decreasing linearly with as speed increases, and it is decreasing faster than your legs can make up for it, all while your wind resistance is going up exponentially. Pedaling does almost nothing in most cases (unless you have a very small motor, very strong legs, and relatively slow speeds).

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Hmm so 30 might still be too optimistic. All I really need is 26-28, TBH, but who doesn't want more speed?

35lbs is also a very hard target to meet if you want to go fast.

I speak from experience. I have an ultra-light build (19lb donor bike) with a light motor and strong legs, but at that light weight it only works on relatively flat ground. You gotta give somewhere…

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I'm hoping the double-torque motor will change that equation. The motor only weighs 6.5 lbs, so we're looking at a ~40 lbs bike that can cruise at 25 and climb any hill, and if I detach the battery I'm only carrying ~33 lbs on my shoulder. That's pretty damn good.

Still, I'm wondering now if I should just forget about the weight and invest in some extra security features.

I think the real problem might be the light weight rigid road frame. I know that 20MPH is about as fast as I want to ride my bike on the pavements in Houston. Hitting a bad bump at that speed can really challenge your stability ... I can only image the effect of doing 30MPH in a similar situation. Skinny, high pressure tires LIKE smooth pavements.

The not so mighty mini is a back up battery or one for a hangful of miles. BBSHD or MAC, with a EM3ev Dolphin pack.

LewTwo said:

I think the real problem might be the light weight rigid road frame. I know that 20MPH is about as fast as I want to ride my bike on the pavements in Houston. Hitting a bad bump at that speed can really challenge your stability ... I can only image the effect of doing 30MPH in a similar situation. Skinny, high pressure tires LIKE smooth pavements.

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That's very true, and SF has some really terrible roads. I'm now thinking that, while not impossible, this build is so close to the edge of feasibility that it's not a good idea for a first project. I'll probably take a much more conventional strategy of a downhill bike paired with a BBSHD or MAC instead and shoot for a weight of around 50 lbs.