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

[MadRhino]

50 lbs is a very light target when starting with a DH bike. It sure makes a good ride and many DH bikes will handle fine at very high speed, but for a low speed bike their weight is a turnoff IMO. That would be starting with 15 lbs penalty at a minimum. I would suggest if you want to have suspension, to build on a lighter Trail or AM bike with 4" suspension. You are not planning fast enough, nor rough enough terrain to justify 8" suspension travel and a DH frame.

 

[arthurtuxedo]

Good to know, thanks! At what speeds would I want a DH bike?

 

[Alan B]

Welcome to ES. Consider putting your general location info in your account.

Ilia of ebikessf.com is an expert on what you are doing, and he is local to you there in SF. He knows what works there and can help you.

SF has a couple of streets reaching over 31 percent gradient. Those type of conditions favor the larger gearmotors or mid drives. You also need really good brakes for the descents. The potholes and rough roads demand a solid bike. Making something that will do 30 mph and climb those hills and still carry up stairs is a difficult balance, as the helpful ES folks have indicated. I would also add folding for public transportation, car trunks and easier storage indoors after carrying it up those stairs.

I'm building and testing two folding bikes now, one with the double-torque motor, and one with a BBS02. I am not far enough along with this project, but I have been running the double-torque with the Mighty Mini battery and it is a fairly light setup. It bogs down a bit on 15%, it is certainly not going to be fast on 30% climbs. On the level it is not fast either (in the low 20's due to tire size), I can easily pedal much faster. The BBS02 will outperform it in both speed and climbing and the weight difference is quite small.

Best of luck with your project.

 

[MadRhino]

Good to know, thanks! At what speeds would I want a DH bike?

With a DH bike you build a light weight motorcycle, or a heavy ebike. When you plan to build ebike kind of power and moderate speed, you are better starting with a bike that is 25 lbs max. DH bikes are around 35 lbs because of long travel suspension, robust frame and components. Most who build on DH frames are targeting 40+ mph and finish with 70 to 100 lbs bikes. My street bike is 69 lbs with a top speed above 70 mph. It is very light for that kind of performance, but would be considered heavy by most who are targeting common ebike performance.

 

[arthurtuxedo]

Welcome to ES. Consider putting your general location info in your account.

Ilia of ebikessf.com is an expert on what you are doing, and he is local to you there in SF. He knows what works there and can help you.

SF has a couple of streets reaching over 31 percent gradient. Those type of conditions favor the larger gearmotors or mid drives. You also need really good brakes for the descents. The potholes and rough roads demand a solid bike. Making something that will do 30 mph and climb those hills and still carry up stairs is a difficult balance, as the helpful ES folks have indicated. I would also add folding for public transportation, car trunks and easier storage indoors after carrying it up those stairs.

I'm building and testing two folding bikes now, one with the double-torque motor, and one with a BBS02. I am not far enough along with this project, but I have been running the double-torque with the Mighty Mini battery and it is a fairly light setup. It bogs down a bit on 15%, it is certainly not going to be fast on 30% climbs. On the level it is not fast either (in the low 20's due to tire size), I can easily pedal much faster. The BBS02 will outperform it in both speed and climbing and the weight difference is quite small.

Best of luck with your project.

Thanks for the advice! The Luna Mini Folder seems pretty similar to your BBS02 project, and would probably suit my needs well. My main concern is that I currently have a Brompton and I worry that it would be a big step down in every way except the motor, like going from caviar to PB&J in terms of the folding action. What donor bike are you using or what folders would you recommend as a starting point?

Good to know, thanks! At what speeds would I want a DH bike?

With a DH bike you build a light weight motorcycle, or a heavy ebike. When you plan to build ebike kind of power and moderate speed, you are better starting with a bike that is 25 lbs max. DH bikes are around 35 lbs because of long travel suspension, robust frame and components. Most who build on DH frames are targeting 40+ mph and finish with 70 to 100 lbs bikes. My street bike is 69 lbs with a top speed above 70 mph. It is very light for that kind of performance, but would be considered heavy by most who are targeting common ebike performance.

That does sound tempting. If I can't keep the weight under 40 and still hit my other goals, I might as well go for balls-to-the-wall power and blistering speed! It would actually serve a purpose, too, since I sometimes go to Tracy and the BART train doesn't go all the way there. I could theoretically take a bike like that on BART and then cover the distance from Pleasanton to Tracy. Normally that would not be doable on a bike since you have to take a mountain road with a 45 MPH speed limit and the low visibility corners would guarantee death-from-behind to a cyclist. I imagine that getting spotted by police doing 45-50 on a bike with no license plate could land me in pretty big trouble, though.

I had a crazy idea today about a build that's basically a stealth motorcycle where the pedals aren't actually connected to the wheels but drive a dynamo that recharges the battery, being driven by 2WD MXUS motors at 9 kW each, and with detachable dummy plastic panels that cover the pedals and make it look like a motorcycle when I need it to, complete with dealer plates on the back for brief highway jaunts. I'm not insane enough to try to build something like that, just to dream it up

 

[arthurtuxedo]

I'm thinking that I'm trying to do too much with a single bike. All I really need is something light that can take some stress off my knees so I don't get injured. I'm now thinking that my best bet would be something like a low-end Tern or Dahon with a Q100H @ 328 RPM in front. The 20" wheels make the hills easier and top speed should be about 20 MPH, which is all that I need. It should be better than the XB-300 Li for my needs, could replace the Brompton as a folder, and would hit the <40 lbs weight target. A 30+ MPH bike would be a completely separate build with a whole different set of constraints.

 

[d8veh]

Dahons and terns often have narrow and stiff forks, which makes fitting a front motor tricky. A rear motor would probably be better. If you choose one of the cheaper ones with 7-speed freewheel gears, you can use the Q100H. For the cassette gears ones, you need a Q100C, which is more complicated to fit and not as powerful.

 

[Alan B]

The Xootr Swift folder uses standard bike parts and is fairly light (about 25 pounds before motor), and the dual torque front non-disc motor fits in the steel front forks with minor effort. It reaches 20 mph in high speed and climbs well in low gear. The same bike with a BBS02 will reach higher speeds, around 28-30, and weighs a couple pounds more, and climbs faster as well.

The Dahons and many other folders tend to use nonstandard bike parts which creates problems for installing motors. They are often heavy as well, depending on the model. The Swift is often made lighter by substituting higher grade standard bike parts. It is very stiff and has a wheelbase and riding position comparable to a fullsize bike. Search for reviews on the Xootr Swift on the internet.

Making separate bikes with different goals is a good plan. Range, speed, power, climbing ability, efficiency, surface handling, suspension, folding ability, lightweight don't all come at once.

 

[d8veh]

I just just fitted a Q128C to my bike. I fancied a change from my Xiongda that I've been using for the last three years. i've lost a bit of weight, so i don't need the low gear winch anymore. I've been using 9-speed changers on the 8-speed freewheel so i also wanted to get the precise shifting from a 9-speed cassette.

This motor really rocks. It has a lot of torque and speed. I have the 201 rpm 36v version at 48v and 15 amps. i took it straight to my 14% test hill, where it dragged me up no problem without pedalling (109kg all-up weight). No-load speed is 29 mph, so should cruise at 25 mph easily on a hybrid-type bike with 26" wheels. It could be faster with 700c wheels. It's exceptionally smooth and quiet with the sine wave controller. I'm sure that this would be the perfect solution for OP. 20 amps might be necessary for cruising at 25 mph, but that would reduce the range proportionally.

 

[arthurtuxedo]

The Xootr Swift folder uses standard bike parts and is fairly light (about 25 pounds before motor), and the dual torque front non-disc motor fits in the steel front forks with minor effort. It reaches 20 mph in high speed and climbs well in low gear. The same bike with a BBS02 will reach higher speeds, around 28-30, and weighs a couple pounds more, and climbs faster as well.

The Dahons and many other folders tend to use nonstandard bike parts which creates problems for installing motors. They are often heavy as well, depending on the model. The Swift is often made lighter by substituting higher grade standard bike parts. It is very stiff and has a wheelbase and riding position comparable to a fullsize bike. Search for reviews on the Xootr Swift on the internet.

Making separate bikes with different goals is a good plan. Range, speed, power, climbing ability, efficiency, surface handling, suspension, folding ability, lightweight don't all come at once.

It seems like the Xootr Swift is exactly what I am looking for. The website is selling the frameset with fork and folding pedals for $541 with shipping, and then I can build it up to my exact specs. It looks like some people have built pedal-only versions that weigh as little as ~20 lbs, so I won't have to make nearly as many compromises as I thought. Thanks for the advice!

 

[arthurtuxedo]

I just just fitted a Q128C to my bike. I fancied a change from my Xiongda that I've been using for the last three years. i've lost a bit of weight, so i don't need the low gear winch anymore. I've been using 9-speed changers on the 8-speed freewheel so i also wanted to get the precise shifting from a 9-speed cassette.

This motor really rocks. It has a lot of torque and speed. I have the 201 rpm 36v version at 48v and 15 amps. i took it straight to my 14% test hill, where it dragged me up no problem without pedalling (109kg all-up weight). No-load speed is 29 mph, so should cruise at 25 mph easily on a hybrid-type bike with 26" wheels. It could be faster with 700c wheels. It's exceptionally smooth and quiet with the sine wave controller. I'm sure that this would be the perfect solution for OP. 20 amps might be necessary for cruising at 25 mph, but that would reduce the range proportionally.

That sounds like a good way to go. My only complaint would be that I don't like the delay that my current rear-hub motor bike has, and would like something that matches my pedaling more instantaneously. From my research, it seems like the TSDZ2 is what I'm looking for, unless there's a controller out there that can kick the motor on and off more quickly. I do like the way that hub motors don't stress the drivetrain, can move the bike even if the drivetrain is FUBAR, and move the weight balance forward if mounted on the front wheel, so please let me know if there's a controller out there that would be a good fit.

 

[Alan B]

I wonder how many SF hills exceed 14%? The 31% gradients are going to be a real challenge, only a mid drive, dual motors or a large heavy hubmotor is going to do much on that grade. A front motor is likely to have trouble due to traction limits. My requirement has generally been 15% corresponding to hills on my commute, and most small hubmotors (except perhaps the dual torque) will overheat quickly on 15% if they will climb it at all.

 

[MadRhino]

Yep. Climbing 30% can fry a hub motor pretty quickly. You need enough torque to climb it fast, ideally. Cimbing it slowly is gears domain.

 

[d8veh]

My only complaint would be that I don't like the delay that my current rear-hub motor bike has, and would like something that matches my pedaling more instantaneously.

The delay comes from your controller, not the motor. These KT controllers are instant, as are most modern controllers.

I don't even use brake cut-offs because cut-off is instant too as soon as you stop pedalling.

 

[tjgaryiv60]

I do not know if you are done yet but I have used this motor kit mfg before with very high quality and works perfectly. Great customer support. Ask for Jun Liu.
It is 1500 watt and the controller is 45 amp. Great LCD display. Plenty for your desired top speed and 50 % more hill climbing power than a 1000 watt 30 amp system. No problem keeping up with traffic merging etc and top end in the 40's mph or so and at least 30 mile range plus. Easy conversion . I have used their 72v 1500 watt fat tire kit and sold it to a local guy and he loves it. Got 2000 miles on it in 3 months.
He gets 48 mph out of it and nothing heats up.
Here is the link Only 408.00 total

https://www.aliexpress.com/store/product/48v-1500w-26-Rear-Wheel-Ebike-Conversion-Kit-with-Sine-Wave-Controller-LCD/513166_32432466379.html?spm=2114.12010612.0.0.OPn2BF

Here is the battery i recommend. I have bought about 10 from Hercules they are all great. This battery is rated at 48v 50a bms 25 ah
Only 505.00 Ask for Anna Hu.

https://www.aliexpress.com/store/product/2400W-Bicicletas-Electricas-48V-Lithium-Ion-Battery-Packs-48V-25Ah-Electric-Bike-Battery-Triangle-Li-Ion/1863299_32770022126.html?spm=2114.12010612.0.0.LyKJag

Pick your own 29 " wheel bike and your set. I recommend linear pull brakes and get kool stop mountain pads from amazon 15.00. Locks
em up at any speed. Let me know Thanks

 

[arthurtuxedo]

I wonder how many SF hills exceed 14%? The 31% gradients are going to be a real challenge, only a mid drive, dual motors or a large heavy hubmotor is going to do much on that grade. A front motor is likely to have trouble due to traction limits. My requirement has generally been 15% corresponding to hills on my commute, and most small hubmotors (except perhaps the dual torque) will overheat quickly on 15% if they will climb it at all.

According to Hill Mapper, the steepest hill on my route is only 13% grade. My current 300W bike handles it just fine as long as I get out of the saddle and pedal hard, so I'm hoping with more wattage I can remain seated. If I get the TSDZ2B then I won't have any trouble with hills. At 8 lbs it's starting to seem like a no-brainer for a lightweight build in a hilly city.

 

[Alan B]

It is difficult to assess the adequacy of a mixture of human and electric power. If the electric can't get up the hill by itself, is that a good ebike for commuting? One day I took a minor fall on the way home near work, so I had 12 hilly miles to get home. My knee was bleeding, my ankle had been hyper extended, etc. I had to get home without a lot of pedaling. I certainly didn't want to sit by the side of the road waiting an hour for a ride home that could accommodate me and the bike, or leave it alongside the road. A bike that required a lot of pedal input would have failed me that day. I easily rode my ebike home that day.

It depends what you want. But for a day to day commuting system I think the human input should be optional. That doesn't mean you don't pedal a lot, it just means that you don't need to. Pedaling is optional.

But this is a personal choice.

Mid drives are excellent for hills. I'm not familiar with the one you mention. They do require some maintenance, can you easily get parts and help locally, or at least in the US? If you are mounting it on a folding bike you may need a larger chainring to compensate for the small wheels. The BBS02 has a variety of chainrings available so I was able to obtain it with a chainring that matches the bike's standard unit so I can still pedal to around 30 mph. With a 42 the pedaling would spin out at a lower speed. BBS02's are common and parts and expertise are easy to find. Parts like internal clutches, gears, bearings, controllers, crank parts and chainrings are occasionally required and available.

 

[d8veh]

My requirement has generally been 15% corresponding to hills on my commute, and most small hubmotors (except perhaps the dual torque) will overheat quickly on 15% if they will climb it at all.

I can't really agree with that. I have a lot of experience with the smaller geared hub-motors. Where I live we have hills that exceed 30% and I've never seen one fail yet. I've seen one where the controller's phase wires melted, but the motor was still OK and when I tried twin high-speed Q100s up a very long (1 mile) 10% hill, both controllers overheated so that the thermistor cut them out. Bear in mind that I've been around 100kg for the last 7 years.

That Q128c that I just tried can pull me up a 14% (measured) hill without pedalling. With pedalling, it's speed would be enough to keep it out of the overheat danger zone for anything except really long hills.

I'm not saying that a hub-motor is more suitable than a CD, but I think they're OK for 15% hills unless you're more than 100kg. CDs bring their own problems, which is why I don't like them for a commuter bike: The constant need to be in the right gear wears you down, and the crunchy shifting. You can also get drive-train reliability issues that would leave you stranded. Everything has advantages and disadvantages.

 

[arthurtuxedo]

It is difficult to assess the adequacy of a mixture of human and electric power. If the electric can't get up the hill by itself, is that a good ebike for commuting? One day I took a minor fall on the way home near work, so I had 12 hilly miles to get home. My knee was bleeding, my ankle had been hyper extended, etc. I had to get home without a lot of pedaling. I certainly didn't want to sit by the side of the road waiting an hour for a ride home that could accommodate me and the bike, or leave it alongside the road. A bike that required a lot of pedal input would have failed me that day. I easily rode my ebike home that day.

It depends what you want. But for a day to day commuting system I think the human input should be optional. That doesn't mean you don't pedal a lot, it just means that you don't need to. Pedaling is optional.

But this is a personal choice.

That's a very good point and relevant to my situation. I bought the electric because I went straight from moderate riding to 13.5 hilly miles per day, which is in the ballpark of how a pro trains, except that I never built up the protective muscle tissue around the joints so my knees, hips, and lower back are constantly on the verge of being injured. The ability to let the motor do most or even all of the work when my joints need a rest is important.

Mid drives are excellent for hills. I'm not familiar with the one you mention. They do require some maintenance, can you easily get parts and help locally, or at least in the US? If you are mounting it on a folding bike you may need a larger chainring to compensate for the small wheels. The BBS02 has a variety of chainrings available so I was able to obtain it with a chainring that matches the bike's standard unit so I can still pedal to around 30 mph. With a 42 the pedaling would spin out at a lower speed. BBS02's are common and parts and expertise are easy to find. Parts like internal clutches, gears, bearings, controllers, crank parts and chainrings are occasionally required and available.

No, I would be totally on my own when it comes to parts and assistance with the TSDZ2. I think that brings me full circle back to my original idea, the Xiongda double-torque motor. I can run it in the high gear most of the time and pedal as much as I want unless I need a rest and want to go up a hill in which case I'd switch into the low gear.

 

[dogman dan]

I'm still saying because of where you live, go with a mid drive. Even a very low power one can be amazing on very steep hills.

So the low power mid drive, that thing can run on a tiny battery, further cutting the weight, which seems pretty important to you.

Very light 26" MTB, put skinny tires on it, entire thing can easily be 50 pounds including the battery.

Big motors that feed on 1000w, will need double the battery weight to run, and have the battery last.

 

[arthurtuxedo]

I'm still saying because of where you live, go with a mid drive. Even a very low power one can be amazing on very steep hills.

So the low power mid drive, that thing can run on a tiny battery, further cutting the weight, which seems pretty important to you.

Very light 26" MTB, put skinny tires on it, entire thing can easily be 50 pounds including the battery.

Big motors that feed on 1000w, will need double the battery weight to run, and have the battery last.

It's tempting, although I'm still leaning towards the hub for redundancy reasons. If my bike craps out in the middle of my shift, I'd have to rent a scooter to finish it out and call a Lyft to the bike shop afterwards. Mid-drives stress the drivetrain and won't run if the chain snaps or the derailleur blows up the rear wheel, whereas a hub can get the bike where it needs to go even if the chain is FUBAR, and can be pedaled normally if the motor gives up. I also have a soft spot for 8-speed IGHs and belt drives, which don't usually play nice with a mid-drive.

 

[Alan B]

Some of the IGH's do work well with mid drives. That would be a good setup. Maybe opt for fewer gears to get a more rugged drive.

Belts are probably not worth the trouble and expense. A spare chain is probably easier to carry, and belts require breaking the frame or strange frame geometry to install, and they require a lot of width as well as uncommon sprockets.

If you want lots of reliability then 2WD might be interesting. Geared hub in the front, and either DD rear hub or mid drive. Not going to be light though.

Do you ever get flat tires? Mid drives are quick and easy to change tires, hubmotors not so much.

If you want to use a less common mid-drive, buy a second kit for spare parts and go for it!

 

[arthurtuxedo]

Some of the IGH's do work well with mid drives. That would be a good setup. Maybe opt for fewer gears to get a more rugged drive.

Belts are probably not worth the trouble and expense. A spare chain is probably easier to carry, and belts require breaking the frame or strange frame geometry to install, and they require a lot of width as well as uncommon sprockets.

That's a shame. I demo'd a Faraday Porteur that had a belt and I really liked it. Sounds like it's not easy to install on an existing frame like the Xootr Swift, though.

If you want lots of reliability then 2WD might be interesting. Geared hub in the front, and either DD rear hub or mid drive. Not going to be light though.

Lightness is a must, otherwise we're talking a whole different build. If I can't comfortably lug it up the stairs 5x per day, then it's going to be a beastly stealth motorcycle, weight be damned!

Do you ever get flat tires? Mid drives are quick and easy to change tires, hubmotors not so much.

If you want to use a less common mid-drive, buy a second kit for spare parts and go for it!

I run Schwalbe Marathon Plus tires on the Brompton so I never need to worry about flats. I used to run the regular Marathons and flatted about 2x per year so I upgraded. The XB-300 is running el cheapo 26" mountain bike tires which I'm sure do not have any puncture resistance, but the rubber treads provide enough of a buffer that I haven't had a flat so far. On the Xootr I'll probably grab some Marathon+ since I like them on the Brompton.

I'll probably sell the Brompton to finance this build, so I don't have severe budget restrictions, but that doesn't mean I can afford a second motor. I'd rather use something that doesn't need parts shipped across the Pacific, so I'm thinking I have 2 options:

1. Hub motor and medium-sized battery. The double-torque motor weighs 6.5 lbs and a shark battery is another 7.5, figure an extra lb for controller and various housings and mountings and that's 15 lbs. 22 lbs for the pedal-only Xootr Swift is pretty typical so that's 37 lbs total. I could go with the Cute Q100H and save 1.5 lbs and a small amount of money, but I would lose the ability to power up hills on motor-only and support from a US-based company. Still an option, though.

2. BBS02 and small battery. The motor is 10 lbs and the Mighty Mini battery is only 3, so that's 35 lbs. I'd have even more torque in case I needed to tackle some of SF's gnarliest hills (the ones on my route are pretty mild, though) and higher top speed so I could fulfill my goal of briefly merging into traffic when the bike lane is blocked. I've heard that mid-drives feel better than hubs, too. I'd give up the redundant propulsion systems, some excess range (either option would be more than enough for my daily route though), and the ability to relax my legs and let the motor do all the work.

I'm leaning towards option 1, but I could easily be talked into #2 if there are considerations I don't know about.

 

[Alan B]

To me, mid drives feel like manual transmissions and hubs feel like automatics.