Lightweight bike project

J

Jimbo

100 mW
Joined
May 10, 2011
Messages
47
Hi all, just registered on here, looks like an excellent forum with some very knowledgeable members! Was hoping you could offer a little advice...

I currently commute around 8 miles (each way) on my full sus Trek fuel, perhaps not a super lightweight bike, but with the skinny road tires it doesn't do too badly; and its nice and comfy. I can keep an average of around 17mph for the journey but was considering adding a small 'leccy motor in the front wheel to give me a bit of extra oomph. The motor would be to increase my speed and add a little help, not to drag me along without pedaling or get me flying along at 40mph, though this would be nice!

I want to keep it as lightweight as possible as I still want to be able to pedal the thing. I have had a test ride on a Cytronex http://www.cytronex.com and its pretty much what I’m after, just with a little more power maybe, without the hefty price tag and keeping my current steed. I had intended to use the same motor but having read a few reviews it seems there may be some better stuff out there. I like the batteries in the waterbottle idea, and the on / off switch (no point having a throttle with only 180 watts).

so over to you, suggestions on lightweight hub motors around the 300 - 500 watt mark? Decent batteries? - I’m thinking LiPo's from a model helicopter with model PWM control...?? Keep the voltage high for speed, not too worried about AH as I can charge the pack at work....Open to suggestions really,

cheers :)
 
As you said you wanted 40mph, You will need 9C 9x7 Direct Drive hub motor and LiPo is not for lack experience because it can be lead explode or lead start fire. Ping battery 60v can take you near 40mph and Play'N Plug less worry about getting careless.

These are not legal in England, I assume you are from England due the link you gave was relate in england.

Lastly, skinny tire is not recommend for the 40mph zone, stick with the FAT tire I.E. Hookworm tires 2.5" or Cyclop CST 2.4". These are great for the high speed and My ebike runs like champ.

PS. If you really experience with the LiPo battery then get 20s2p or 20s3p (10Ah or 15Ah) depends what you plan travel distance and this will take you into 40+ mph zone.


Good luck! 8)
 
I'm just a bit unclear what you really want. I get it that you like light and stealthy. Right away that brings Ampedbikes to my mind.

http://ampedbikes.com/ They sell a waterbottle battery, and a small geared hubmotor. Typically the small gearmotors weigh about 8 pounds, though the whole wheel ends up about 15 pounds in most cases. Heavier spokes, sometimes heavier rims, fat tire, etc. Ends up 15 pounds, plus battery weight added to the bike. Usually this type of motor will go at least 20 mph on the flat. Not as powerfull on the hills as much heavier and higher wattage direct drive motors, but a great solution for a slightly lighter ebike, especially since smaller batteries can be used. I'm a bit vague on performance for amped, since I've never tested one personaly.

On the other hand, googling a trek fuel, the one I looked at is an excellent candidate for a much more powerful and faster ebike, using the above suggested, or other similar direct drive motor. Also a good idea is larger gearmotors, such as the BMC and Puma. http://endless-sphere.com/forums/viewtopic.php?f=31&t=17029

Forget the RC controllers and either use one that comes with the kit, or look at Lyens in the for sale section for the Hot rod stuff. Lipo for the battery is the way to go for performance, while pingbattery lifepo4 can still be a great way to power a commuter that only wants to go 25 mph. Lipo will be easier to carry on that particular bike. You definitely want rear hub for that bike, and will have to fabricate some kind of torque plate to keep from ruining the frame.

Lastly, I can't stress enough, that finding a cheap steel frame mtb is the best way to start out. Get riding on it, learn some more, and then move the stuff over to the trek when you know what you are doing, and have the torque plates, etc figured out. Making mistakes that ruin that trek would be a bummer.
 
If you are more interested in assist power than in the 40 mph, you could consider a cell_man geared hub kit (in the for-sale-new section here http://endless-sphere.com/forums/viewtopic.php?f=31&t=19971&start=75#p314103). I've got the 350 W front geared (17A controller) and run it 18 km (11 miles) on a pair of 5S 5Ah LiPo batteries in series (10S) with a little room left over. That's with me pedaling at least lightly all the time, and medium up hills).

Very very lightweight setup, excellent range for such small batteries. And the acceleration and assistance up hills is much more than I was expecting. I still get (pedalling along) at least 20 kph even up fairly steep hills. And with the geared hubs, if you want to go pure human power, there is no drag.

On 10S LiPo I'm only getting 28-30 kph (under 20 mph) but I've tried it on 12S LiPo and got around 35 kph. Its not rated for that high a voltage, but it is comparatively cheap enough that the possibly shortened lifetime might be acceptable. But I went back to 10S because, well, for me I was losing the love of biking on 12S -- it was fun for a few trips but then I found I was missing the high I got from biking with more of my own power.

If you really want the higher speed, you could add a few more pounds weight and some more money and get the larger geared kit already mentioned.

Sounds like you know a bit about LiPo already -- it is not for the faint of heart, but I made the choice to go there even though I was a newb. I spent the money for a good charger and take all the precautions. It's really a great option to keep things light and modular.

Oh, not sure what's on your bike, for a first build if you go with front hub you should have steel/cromoly forks, and torque arms for extra strength.
 
First the Wired review said Cytronex was running out of power towards the end of their 14 mile test run. You can do better.

The AmpedBikes controller is rated for 36-60 volts. 36V will get you 22mph, just slightly illegal here in the states. 48V puts you around 30mph. (AmpedBikes only warrants the controller for 36V) 30mph on a bike is a bit fast I couldn't imagine doing 40! Keep in mind you're on skinny bike tires on a lightweight bike. If you want to sustain speed get something with at least 1.95 tires or maybe a low-slung trike.
 
Thanks for the replies guys!

To clarify, im after something that is as lightweight as possible that I can turn on at around 17 mph (which is my natural cruizing speed) and which will then take me to say 25 - 30mph. So im not after torque, rather top end.

The amped bikes kit looks good - though it seems to run at a max of around 20 mph.....I really want this motor with different gearing for use from 15 – 30mph rather than 0 – 20 as stated. I suppose I could over voltage the motor to around 48V but I assume I’d burn it out fairly quickly? Stanz, you say the controller is rated for 36 to 60V, you think the motor would cope as well?

Good points about the legality issue, but im all for law breaking on a subtle scale ;) Point taken about the tires as well - fatter may be better.

As I understand it a direct drive motor would act as a generator when im pedaling, hence making it harder; whereas a geared motor has a freewheel built in so allows me to pedal with no drag from the motor? I assume a geared motor would be less durable though due to the extra gears etc?
 
It won't work on a full suspension bike, but you might be interested in my little project. I built a friction drive that is about as light weight as an ebike kit can get.

http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=22187&start=585#p375065

Otherwise get a hub motor, slap it in the back wheel and ignore the weight. It is really a non issue as long as you don't run out of juice.

- Adrian
 
Jimbo said:
Stanz, you say the controller is rated for 36 to 60V, you think the motor would cope as well?
Click to expand...

Sure, stock it handles 500W at 36V. The FAQ states they get 23MPH from the 26" wheel kit.

Here's a quote from the AmpedBikes FAQ: "Our motors can run up to 750W without generating any heat due to over amperage."

There used to be some stuff about running 48V on the site but I don't see it.
 
Sounds like 12s lipo would run the smaller cellman motors at just about the right speed for you. A small rear hub gearmotor is not a bad starting point to begin your ebike addiction. I like gearmotors fine, but I climb a huge hill in searing desert heat. So I have a bias toward direct drive motors.

Anyway, it's takes a very very small trickle of power from a tiny bit of throttle to make the dd motor resistance dissapear completely. I'm a pedaler too, so here's how I ride. Throttle to about the speed you like, then pedal for about 1-2 mph more speed. It's odd that just 2 mph could take so much effort, but it has to do with wind resistance above 25 mph. You know what I mean if you ever tried to maintain 30 mph without a peloton to hide from the wind in. Above 25 mph, adding 1 mph is a bitch.

But it still sounds to me like you'd like a gearmotor for the light weight, and 10s or 12s lipo should be a winner for you. You might find yourself pedaling up a few more mph, and traveling 25 mph.

Still a REAL GOOD IDEA, to try out ebiking on a cheap steel mtb. Newb mistakes get costly enough without adding wrecking the dropouts of a nice bike.
 
For 25-30mph, the MAC/BMC motor is the lightest you're gonna find that can handle that kind of power reliably.
As a bonus you will be OK on 36 volts for that speed. 48v gets you into the low-mid 30mph zone.

Bikes get heavier as they get faster. Your Trek is actually very ideal for 25+ mph operation. You will have to get used to it being a bit heavy. I started out light and realized i needed a frame that can handle BIG disc brakes without flexing during braking. The extra speed requires additional demands that a bike usually isn't built to deal with.
 
I am curently doing a Trek Navigator, Also wanted to go lite, Bottom line is if you want to go up in performance from the basic kits, You gotta use Lipo, or youll be caring arround a cinder block of batteries on your bike, so you will kill the Bicycle part of your bike, becaus only lipo can put out alot of power in a small size. Your dropouts look tiny like mine, so you might want to think about some torque plates on both sides of the axel, I worry that any twisting is going to really open up my drop outs. I could see a wheel pop out in a bad case scenario. And if you want to save five pounds you gotta go with a gear motor. But I'd say when e bikes get main steam and are designed as e bikes the high end ones will be all aluminim in the future, as long as the componentry is relatively light which it all ready is you don't need steel. Its a different story when your going to stap a 150lb engine on a motor bike. E bikes shoud be light, or whats the point. Of couse if you want to build a motorcycle that you dont need to insure, build anything and throw some pedals on it. I love lite. Heavyness is a atribute seldom desired but some times needed. But how did the Egyptions build thoes temples any way.......?
 
All sounds good guys. Adrian_SM - very nice project, I like the simplicity of it all, looks like a beasty RC motor?

I've been doing a bit of research and i'm thinking of using Cell_man for my batteries and motor. I did have a look at some Li-ion batteries from electric wingman, but the A123 cells everyone is raving about seem to be much safer, and cell_man seems to do them at a reasonable price as well.

So for the batteries I'm thinking of doing two 14 cell A123 series packs in a cylindrical arrangement to fit in the waterbottle carriers I have. Thats 46V @ 2.4 AH per water bottle (ish) sized pack, should be about 85mm dia by 140mm long each and about a kilo. Two packs for about 5AH...

For the motor Cell_mans MAC 500W rear Kits look pretty sweet, though I’m unsure about the weight penalties with this – anyone have any specs for motor and controller weights?

Im aware that although the A123 cells have a high C rating I only have 230W of power in my packs = a theoretical less than half hours run time. In reality am I going to get 10 minutes out of this and end up hacking home by leg power? Lots of factors to consider I know, but im after a general feeling based on the following: -

I want to commute about 8 miles on a charge - If my calcs are right I should have theoretically 27.6 mins of continuous use at 500W. Assuming 500W = about 25mph then I should be ok. The motor will pull more under acceleration but a lot less when cruising, so maybe I’ll get a fair bit more? For info im about 65kg, the bike = 12.5kg + 4kg?? of motor, 2kg of batts and controller etc = about 20kg. my route has no hills and hopefully little headwind!

Last question, since I’m not a fatty, and the bike should be reasonably light(ish) then what can I expect in terms of performance? Will it loft the font wheel off the throttle? Will I get to 30mph? I’m getting a bit obsessed by the power thing now.

Cheers!
 
Hey man,

I'm doing a lightweight build based on a modern trek road bike. I'm considering one of these motors: http://www.ecitypower.com/index.php?option=com_content&view=article&id=66&Itemid=99

I haven't heard much feedback from anyone, but at 3.5 lbs I'm willing to sit on the learning curve a bit!.

Edit: nobody seems to have stock. Ill have to see what I can dig up...
 
Jimbo,
Your commute and bike sounds a lot like mine. I recently converted from a hard tail to a trek fuel. I must say the Fuel rides like a dream compared to the hard tail. I also have an 8 mile commute with a decent hill at either end I have found that 48 v 20 amps is more than enough to make a 8-10% grade manageable with light pedaling.

On days where I let the bike do most of the work I use about 4 ah going to work (mostly uphill) averaging 25 on the flats and 15ish on the hills. (pulling 850w on the hill) If your commute is mostly flat 5ah is enough to do what you want but doesn’t leave you much room to spare. I went for 8 ah hoping to make it to work and back without a recharge. I can but I run the pack so low that I usually charge at work anyway, I feel more comfortable knowing I have room to spare in the battery.

On days that I do most of the work and just use the battery for a little extra speed I end up using about 2.8 ah (at 48v) to get to work and 1.5 ish to get home. So pedaling makes a huge difference in your range.

As for performance with a 9c I can hit 28 without pedaling at 48v. I can pedal to 30-31. You probably won’t hit 30 even pedaling. Plus the stock fuel gearing won’t help you much past 25mph. I had to change out the front chain ring to make 30 realistic.
 
cell_man 500w motor: about 9lbs heavier than a regular rear wheel.
9FET controller: maybe about a pound.

10S 5ah lipo: about 3 pounds.
With the lipo in the front triangle, the bike will feel very balanced and ride much like a regular bike.

That's a ~15 pound setup or so. Add about 3 pounds per 5 amp hour.

oh.. and 10S is quite fast on the 320rpm wind in a 26" wheel. i've hit up to 30mph in mine, though 24-26mph is more typical, and 20mph+ on hills.
 
neptronix" about 9lbs heavier than a regular [/quote said:
9 lbs in a wheel is HUGE. I agree that would make a nice ebike.
But for a lightweight, definately go with something small and geared. I just got in touch with BMS battery and ECitypower, and I'm going to to put in an order for the q-100 (which is 4 lbs) there is a smaller q-85 (which is only available in a front wheel configuration and my fork is carbon so....) which is 3 lbs. Let me know if you want me to order you one.
Click to expand...
 
Jimbo said:
suggestions on lightweight hub motors around the 300 - 500 watt mark
Click to expand...
neptronix said:
For 25-30mph, the MAC/BMC motor is the lightest you're gonna find that can handle that kind of power reliably.
Click to expand...
Are you kidding?

MAC is the heaviest of all geared freewheeling motors.
Any small geared can handle 300-500W (provided the rider is not a total moron)

Jimbo, look up Ananda (often ref as Cute) and Bafang Jewel. Its very likely that you will want something more powerful later on though
 
No I didn't. I didn't realize they ever made them to begin with... I assumed it was just bigger and they couldn't fit the lightweight version on the axle, not sure.

I picked up a Q100 for my rear. 4 lbs isn't bad, and my goal is to take another lb out of it. I wanted to do the Q85 front, but I fear it would obliterate the carbon fork, and I really want to keep that fork. I wouldn't be surprised if I could take half the weight out of it by milling, and drilling. We'll see mechanical stuff usually isn't my forte, but I really want to see what a lightweight ebike is like. I should still easily be able to get the bike down to 26 lbs or so, which is more like a touring bike weight, but with 2x human power, which should be really interesting.
 
Unless yours is different from the one I've got the QX100 is 2.4kg (5.3lb)

The shell with bearings is 655g (1.45lb) so shaving a lb of that is not a good idea.

If you really want to save weight - go singlespeed. More fun too.
 
full-throttle said:
Jimbo said:
suggestions on lightweight hub motors around the 300 - 500 watt mark
Click to expand...
neptronix said:
For 25-30mph, the MAC/BMC motor is the lightest you're gonna find that can handle that kind of power reliably.
Click to expand...
Are you kidding?

MAC is the heaviest of all geared freewheeling motors.
Any small geared can handle 300-500W (provided the rider is not a total moron)

Jimbo, look up Ananda (often ref as Cute) and Bafang Jewel. Its very likely that you will want something more powerful later on though
Click to expand...

300-500w is not gonna do 25-30mph though dude!...
And yeah, i forgot about the BPM. It's about a pound or pound or a half lighter than the MAC. That's another alternative, but apparently it only works if you have fairly wide dropouts ( what was it, 138mm wide axle? something non-standard )

The little cute motors are amazingly light, but also have very very low amp limits. Low amps = not very useful on hills.. also at 25-30mph you are typically using about 10-20 amps or so, which happens to be the maximum amperage limit for those motors. hit an incline and it will slow down. hit a major hill and it will sputter.

*shrug* i guess i just can't recommend those little ones anymore tho due to the amp limitation. I had a little geared motor, it was cool, for a week. But i have monster hills to climb where i live and i like fast acceleration and good speeds on hills.

If Jimbo has flat terrain, overvolting a smaller motor may work.
 
Agree, I would recommend BPM (3.9kg)

PS power output (from simulator):
329W @ 25mph
527W @ 30mph

EDIT: I started with a small geared hub too - under 20kg whole bike, 500W peak, top speed 37kph. Its ok, but it didn't take long to change to 1200W 55kph 23kg with fat tyres and I wouldn't go back!
 
Hmm... i use more like 600w on the flats ( 15 amp, 40v ) to go 27mph with my MAC motor.
But i'm also 230lb and i have 2 inch tires that are a bit knobby.

But to clarify for the OP: a small geared motor can't take the kind of amps that a large one can. The smaller ones are usually rated for 17 amps or below, which is pretty piddly, torque wise, in terms of hill climbing power, resistance to a headwind, and acceleration from a stop.

So yeah, there is a definite weight penalty with the larger motors ( BPM Climber/Code9/Code12, MAC, BMC ), but their ability to handle 25-40 amps makes them kick ass.
 
full-throttle said:
EDIT: I started with a small geared hub too - under 20kg whole bike, 500W peak, top speed 37kph. Its ok, but it didn't take long to change to 1200W 55kph 23kg with fat tyres and I wouldn't go back!
Click to expand...

Hehe yeah.. i do miss the lightness of my old setup, but for that kind of riding i realized that riding a regular bike would be almost as fast. now i keep a 700c bike around :)

I never did get around to upping the voltage, i found the torque to be the biggest problem. All it took was one 3-4 mile long 5%-7% grade run to discover that the lack of amps was the issue. And the little motor couldn't handle much more, and nobody sold replacement gears for it, so if i destroyed them, i was done for.

Then i found that once i got the bigger motor, i needed a frame with disc brakes because the vbrakes weren't adequate for such high speeds.
Then i found out that i need wider tires because stability became an issue at the higher speeds.
Then i got even bigger and heavier disc brakes.
Now i'm looking into a more heavy duty front fork.

The sad but true progression of every ebike enthusiast ;)
Car guys call this 'getting bit by the horsepower bug' ..
 
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