lightweight ebike

[iflyadesk]

Hi everyone!

I'm thinking of building a lightweight ebike. I've google a lot but "lightweight" means 50lbs to some people, and most of the discussions on here are about more power, not less weight.

I used to race but messed up my back pretty bad in the Air Force so I have too much pain when riding a racing bike. I tried recumbents but they are too dangerous in traffic (too low to be seen). I also tried cruisers/hybrids/city bikes but they are too heavy and cheap feeling. So I pieced together my own 13lb carbon fiber single speed with Gates Carbon Belt Drive and Mavic Kysrium wheels. I used it to commute every day for years in Chicago (9mi round trip) and loved it because I could easily carry it up stairs.

I just moved to Charleston, SC and my commute will be 18mi round trip. There is very little vertical climbing (only one "hill" at 200 feet, 4% grade). I don't want to get soaked with sweat on my way to the office.

I test drove an EMotion City Wave in a parking lot and rented a Trek XM700+ for a day and rode it about 40 miles. I thoroughly love both these bikes when riding them, but there is absolutely NO WAY with my back problems I can pick up a 50lb bike and carry it up a flight of stairs without hurting myself.

Desired max speed on level ground: I'd like 28mph, but 20mph is probably fine.
Desired max range at what cruising speed: 18 miles at 20mph while pedaling
Preferred bike wheel size, or wheel size of bike you want to convert: 700c
Brake type of motor wheel: Shimano 105 caliper brakes. I would consider replacing the front fork and wheel in order to get disc brakes on the front because they are so much more effective in the rain.
Rider weight: 150lbs
Terrain: Mostly flat. Only hill is before-mentioned bridge that is a 4% grade, 200ft elevation change.
Budget: $1,500 or less. Preferably less.

I'd really prefer to keep the whole thing under 28lbs if not lighter. That gives me 15lbs over current weight (so ~16lbs of new equipment if mid drive, 17lbs if hub drive).

I'd like to get this right the first time by leveraging your experience!

Genuinely,
Sam

 

[friendly1uk]

Perhaps the 2.1kg cute 201 with the 3.5kg 48v 10ah removable dolphin battery which leaves the 20a controller in the bracket. 500g of associated wiring and controls. Should be golden. It can come in a plug n play kit too.


https://bmsbattery.com/ebike-battery/680-48v116ah-bottle-09-panasonic-battery-pack-battery.html
https://bmsbattery.com/ebike-kit/631-q100h-36v350w-rear-driving-ebike-hub-motor-ebike-kit.html
Don't forget some spokes and torque arms


Get a second opinion though and also look on the ebikes.ca simulator to see how it climbs

 

[leo99]

Hi sam
I would go with the Q100h 201 from bms and a tiny battery pack from luna cycle 14s and 6ah.
The motor weights 2.1kg and the battery 1.5kg.

Take a look at my build in my signature.
Good luck

 

[friendly1uk]

That battery is very light, but won't go the distance.

The 260 rpm version would tickle at 25mph but that 4% hill would see that drop to 20mph and motor overheat in about 90 seconds. To do that 18 miles flat out would take 11Ah. At 20mph that same 11Ah would take you 25 miles. As batteries are seen as good with only 80% capacity left through aging, you need to specify 25 miles to get 20 miles. Add some wind, it gets worse and oddly when you turn to come home, the wind usually turns too lol. I would go with the samsung pack with just under 12Ah knowing you could drop to about half throttle and do 15mph for 40 miles. Which with some pedal effort should get you through the wind without loosing power before you get anywhere.

Now can you get up that hill in 90 seconds? Could you switch down to 80% power, accept 17mph and get up in just over 2 minutes? 13mph for 3.5 minutes at 60%? Remember you would add some yourself.

It might be better to stick with plan A and get the 201 motor, as it climbs better.

 

[iflyadesk]

The ascent to the top of the bridge is about 1 mi, so at 20mph it would be exactly 3min. There aren't any other hills anywhere. Maybe 10ft elevation change.

 

[friendly1uk]

Nice bridge. With the 260 you might have to drop to about 50% power, giving you 10mph for 5 mins. Too which you would have to add some effort to cut down that 6 minute journey by reaching 12mph. Perhaps walking effort on a good day. I bet it can get windy up there though.

I forget what to call the 201 motor so i can provide the numbers. Here's what I'm doing though http://www.ebikes.ca/tools/simulator.html

 

[iflyadesk]

Here's what I'm doing though http://www.ebikes.ca/tools/simulator.html

Oh wow, thank you for showing me this!

 

[iflyadesk]

Here's what I'm doing though http://www.ebikes.ca/tools/simulator.html

Oh wow, thank you for showing me this!

Except now I need to figure out what all this means.

Geez after lurking here for a few weeks and reading several articles on electricbike.com and electricbikereview.com, I thought I was close to having this figured out, but looking at the charts this simulator spits out and all the verbiage about what it all means, I feel like I don't know anything!

Do you know any electric bike builders I could email for advice based on experience? I really need someone who's done this several times to tell me, "buy this box and that box and that box and plug it all together... it should work great." Maybe after putting it all together and owning it a little while I'll better understand what all this means.

I just want a light electric bike and I don't want to waste money and time getting it horribly wrong the first time.

 

[friendly1uk]

Chas has done a few builds like this and motomech has good experience to. That is by no means an exhaustive list though. I think you would be happy with the kit I first showed you. The 201rpm not the 260rpm I have talked about since. The 260 will reach 25 but then you won't pedal as it's very hard to add anything at 25mph. Your efforts would just extend range. With the better climbing 201 the top speed (which needs confirming) is still about 21mph and the lot just plugs together in a fashion a child could understand. Stopping the motor turning in your frame would be the technical bit. Many solutions exist, but we need to see the dropouts to advise which might work.

Your in the right place

 

[iflyadesk]

is this a fair-weather or all-weather commuter?

All weather.

 

[iflyadesk]

The 260 will reach 25 but then you won't pedal as it's very hard to add anything at 25mph. Your efforts would just extend range. With the better climbing 201 the top speed (which needs confirming) is still about 21mph.

Does it matter that I can't possibly pedal 25mph by myself because it's a single speed 50/22 so I have to pedal about 100rpm to get to 17.8mph?

Stopping the motor turning in your frame would be the technical bit. Many solutions exist, but we need to see the dropouts to advise which might work.

Your in the right place

Thank you for your patience!

 

[slacker]

ypedal.com for motor, luna cycle for battery. If i was doing a light weight build this is the what i would do. Jmo. Good day

 

[2old]

You're going to lose the belt drive with a rear motor; don't recommend a front motor with a carbon fork, so you have two choices AFAICT:
1) steel fork with front hub
2) mid-drive
I would recommend the mid-drive with light (3 pound, 52V, 6 a/h) battery if you can charge at work. Otherwise 48 or 52V 12 a/h. The motor will weigh about 10 pounds making the system possibly as light as 13 pounds or so.

 

[iflyadesk]

You're going to lose the belt drive with a rear motor

Why is that?

I would recommend the mid-drive

I would love a mid drive with gears and I might even go so far as to add a Rohloff rear hub just to get gears, but unless I do, isn't a mid-drive going to limit me to however fast I can pedal? As I said above, with a 50/22 gear ratio and a 700c wheel, that's about 17.8mph at 100rpm.

 

[Chalo]

If you have power assist, you can have a taller gear.

 

[LewTwo]

Where have I heard that before ....
https://endless-sphere.com/forums/viewtopic.php?f=3&t=70586
You may find the spreadsheet helpful for the weights.
What I would up with is actually right at 30 pounds.
https://endless-sphere.com/forums/viewtopic.php?f=6&t=79545&p=1173723#p1173723
... of course since then I have replaced the seat (my butt got sore) and added a light weight rack for the time I did not want the trailer.

If you build it yourself (and I highly recommend that) then you will NEVER get it right the first time because there will always be something that you will wish that you had done differently .... accept it. :?

If you use the bike that you have pictured then you are going to need new wheels ... at least the one with the hub motor. All hub motors are 36 spokes.

Regards the battery: SU Power can build to your spec and they do very nice work.

Biggest Mistake I made:
I used a road frame with a true horizontal top bar.
The maximum width tires are 700c x 28mm which does not allow for wider lower pressure tires.
I ride upright (i.e. not tucked with my butt 2 feet above my head). Thus the seat has to be close to the top bar.
A mountain bike frame would allow for wider tires and shock absorbing seat post.

Biggest thing I did right:
Travoy trailer for grocery runs.

Here is something I thought of after all was done:
You only need two or three gears with an e-bike (I use low when starting up and high to try and pedal as fast as the motor).
If I were to do it again (and I probably will) then I might consider a single speed rear hub and BB with a two or three speed shifter:
... less weight (you would need a spring loaded chain tension idler)
... less stuff to mess with if the rear wheel has to be removed
... a little bit different :lol:

 

[leo99]

All hub motors are 36 spokes.

Not true, my Q100 cst 201 is 32 spoke.

Leo

 

[LewTwo]

All hub motors are 36 spokes.

Not true, my Q100 cst 201 is 32 spoke.

Leo

'tis true they made some 32 spoke hub motors .... I tried to buy one last year.
I didn't because I could not find one.

 

[leo99]

I just bought mine at BMS battery a month ago. :wink:

 

[LewTwo]

I just bought mine at BMS battery a month ago. :wink:

interesting ....

 

[Railgunner]

One option would be to buy two of the luna 6 AH batteries and charge one at work at one at home. That way you would get 12 AH round trip but never carry more than 6AH in weight.

http://lunacycle.com/batteries/packs/52v/52v-mighty-mini-cube-ebike-battery-pack-panasonic-pf-6ah-affordable/

 

[iflyadesk]

https://bmsbattery.com/ebike-battery/680-48v116ah-bottle-09-panasonic-battery-pack-battery.html
https://bmsbattery.com/ebike-kit/631-q100h-36v350w-rear-driving-ebike-hub-motor-ebike-kit.html
Don't forget some spokes and torque arms

So if I understand correctly so far:
(1) Buy the these two items
(2) Have a wheel built around the hub
(3) Buy some torque arms
(4) Wire it all up

Is that correct? So I should probably just skip mid drive for this application?

Looking at the picture on bmsbattery.com, how do I mount the rear sproket? I don't see the splines for a standard Shimano 9/10/11spd cogset back there. I am running a single speed, but it's just a splined gear with spacers. What length/gauge spokes do I use? Is there a vendor who sells complete 700c wheels with this motor already in it?

Is there a shop out there who's done this a lot that can just do it all for me? (for example http://www.charlottecycles.com/about/electric-bike-conversions-pg111.htm - they are a 3hr drive away but easier than having to try and explain all this to the LBS while they stare blankly at me).

I am sincerely appreciative of your advice, so I have to say it's more than a little disorienting that you (friendly1uk) have linked me to buy something from BMS Battery, while your signature says "bmsbattery sent me broken and incorrect stuff, and won't even talk to me about it." Plus when I read through all of the threads about your build, you don't seem too happy with the way it all turned out.

Is there an easy button? I just want a light ebike that works. I really don't have the time (unfortunately) to constantly research, tinker, and iterate. Can I just send my bike to someone and have them convert it or buy a bike off the shelf that just works?

For example, are these legit choices?
http://www.emotionbikesusa.com/en/bicycles/ebikes/easygo-race-eg566-us.html
https://www.freygeist-bikes.com/
http://gocycle.com/g2/product/#features
http://www.vivax-assist.com/en/produkte/e-mtb/vivax-alpha_2-0_26.html
http://www.vivax-assist.com/en/produkte/e-rennrad/fahrrad.php?id=1021

Those are the only commercial eBikes I've found under 40lbs. Would prefer sub 30lbs, and I can get there starting with my bike, but I also want it to "just work."

Is the distance to an ebike dealer going to be a major issue? I once bought an exotic Danish recumbent and every time it broke (which was often) it was out of commission for months while I waited for parts.

If that is the case, there is a local Emotion dealer, so the "Easy Go Race" is probably the only option because (1) I don't have any local ebike conversion specialists to handle my build and (2) there aren't any other brands represented in my region with an off-the-shelf choice under 40lbs.

Please let me know if I'm missing something.

Thanks again for all your help! Better to figure this stuff out before you do it, right?

 

[friendly1uk]

The motor I linked to uses a screw on set of gears, but also comes as a cassette version. One will take your belt drive if you wish to keep it.

I don't see the problem with rwd. You have a nice flat dropout to bond or screw a torque arm on. Something like this perhaps, without using the long slotted bit http://www.pandaebikes.com/product/multi-angle-eyelet-style-torque-arm-4-ebike-electric-bike-stainless-steel/

Perhaps you should just buy a bike though. People build because they like to, or want something special or simply want something as cheap as possible. I'm not sure you fit any of those categories. If you just want it to work and have spare parts in your part of the globe, Then it's perhaps your only choice.

I didn't look at your links as I'm over the pond. I won't know them. Nor any here tbh. I like building them.

 

[iflyadesk]

I just got off the phone with Charlotte Cycles (http://www.charlottecycles.com/about/electric-bike-conversions-pg111.htm)

They do ebike conversions and will do the Bafang BBS02 Mid-Drive conversion kit from e-Rad. Takes 3 days.

I wish I had called them earlier.

For one, I never realized that with the Mid-drive, the chainrings and the cranks are not "connected", so the motor can spin faster than you can pedal. That makes a ton of sense but for all my forum lurking and blog reading, I never once realized it. I love talking to a person on the phone!

Turns out they also sell the Emotion Easy Go Race I mentioned above (33.5lb/15.2kg bike, 250W rear hub motor, 216WHr battery for $1,300). So I'll drive up there, test that bike, and if I don't like it, I'll have them convert mine to a 28lb/12.7kg bike, 750W mid drive, 557WHr battery for $1,400 (+ my bike of course). The price includes labor and warranty.

Sounds like an easy button to me.

The only hassle is it's a 3 hour drive one way, plus I'll have to drop it off and pick it up, so 12hrs total travel time if nothing ever breaks

 

[d8veh]

Personally, I have a lot of reservations about that bike. It's a complete waste of it to fit a 750w BBS02. Sure, it'll be light, but you don't need so light when you have that much power. To me, it would make more sense to keep that bike how it is an get a lightweight hybrid or cyclocross type bike with disc brakes. That's if you insist on a BBS02. I've got a feeling your present braking system would be overwhelmed by the extra speed. The other reservation I have is the torque. Your frame isn't designed to take any torque around the bottom bracket, and a BBS02 will make a lot. If you must fit a crank drive to it, I'd go as low as a BBS01 at 15 amps.
I built this one, which was about 19kg and could easily sustain 20 mph with its "250w" Bafang CST motor. It was actually featured on a TV show (The Gadget Show season 21 episode 9). The bike and kit cost me about £800. It would still be a good build with a BBS02, which would make it about 5 mph faster.