First project, falling before start(250w)

Hi all, newcomer here. I have been reading in this forum for a while, even though i wasn't planning to build an ev back then. It is just interesting fun to read and learn about all this stuff. Very good community.

So recently i started to think that i could use an electric bike to commute between school and work and home. Without a personal transporter i started to feel like tied up. Go to bus stop, wait it, and it is crowded...
I can't afford a car. Besides there is traffic and gas consumption. And didn't want a motorcycle, too much trouble. Btw work is for now not paid. So i am broke

After some research i decided that a simple 250w hub motor kit with 10ah battery on my cyclocross bike is all i need. (40-60km a day) I would only use it in pedal assist mode in ascents. It is also very flat here.
Anyway i looked up their prices. Well what do you know they are cheap! Then i looked at their shipping cost and well... They are NOT cheap. Almost as much as whole kit.
So i think that 700c wheel must be raising the shipping cost so i decide to buy motor and controller only, i will make it lacet to my rims locally. Add only motor and controller to the basket, calculate again...
Nope. Still too high.

I am surprised because i shop from china regularly and almost always shipping is free or dirt cheap. Why a single hub motor ships for 60$?

Is this how this is? How do you guys order your stuff?

Cost is not my only problem. I want to keep my bike's drivetrain stock and as far as know there are no rear hub motors that allow 10 speed cassettes(Mine is sram). And the front? It is freaking carbon... I searched hub motors on carbon fork and saw that everyone was against it. It is a disc fork so i thought it would be ok with a torque arm. What do you think?

I consider changing the fork to a steel one. To my surprise, steel disc forks are not cheap. Lets say i found a used standart one. I have to weld disc mounts on it which i am not very confident that if i could do it. And i guess cro-moly forks can't be welded with standart equipment so it has to be hi-ten.

Another option is using the q100 hub motor as mid drive. Bafang mid drives are too expensive for me. I am still searching on this subject. If there is a way to do this while keeping the 2x10 speed drivetrain i would be very happy.

So this is my situation. All advices and suggestions are wellcome.

Hi Z welcome to the forums.
It might help if you give us a location so we can help you find a good dealer or shipping cost when trying to help you find product locally for you. I did a quick search on ebay and found a few ebike kits that had free shipping. Not knowing what kit you picked and if it had battery's with the kit sometimes the shipping could be due to the battery. It would also be helpful if you give us a budget range because battery's will most likely be a huge cost factor depending on your budget.

Here is a kite I found locally in my are on ebay 180$ free shipping.
Not sure if this one has brake disc mount on the hub.
http://www.ebay.com/itm/48V-1000W-E...961896?hash=item339dcf9fe8:g:nzwAAOSw7FRWX-JS

A 48v 10ah battery will run you between $200 & up depending on what kind you go with. If you go with Seal lead battery are the cheapest route but is the heaviest of all the options. And life cycle on those batteries are pretty poor if you do not keep up with the maintenance. Then you have your lithium and liFePO4 batteries which would be lighter but more expensive. You also have to take into account that anyone of these setup will required some type of charging system.

Here is a link that you can use to see the cost associated with battery.
http://lunacycle.com/batteries/packs/?sort=priceasc

http://www.ebikekit.com/electric-bike-battery/sla-lead-acid-batteries/sla-48v-9ah/

I can't afford a car. Besides there is traffic and gas consumption. And didn't want a motorcycle, too much trouble. Btw work is for now not paid. So i am broke

Click to expand...

That is not a good bike to convert, period.
Once you put on a system, it becomes an Ebike that needs to be used with some power all the time no matter how lightweight and trick the donor. A $100 dollar Wally World bike would be better.
The least expensive conversion kit with battery will be around $500 to $600, plus another bike, $700 min(Probably less, if you use something like the DD Yescom kits on Ebay).
But since the main theme of your post is you have no money, I would suggest you sell the bicycle and buy a 50cc motor scooter or moped.
In some States you can use them without Ins, reg., etc.
But since you didn't fill out your profile, I can't say whay the Laws are in your state.
There are also the gas motor conversions like the Spooky Tooth.
I have friends here who put $200 gas motor kits on beater cruiser bikes and they leave me in the dust(and smoke ).
The funny thing is, they think my Ebike is cool and ask me lot's of questions about it, like how money do I have in it. But when I tell them, the response is always the same, "I can't afford that much".

Thanks for fast reply Simon. I am from Turkey. I selected my country at register page and i thought it would show. I am checking it now, thanks for letting me know.
I looked for local dealers but no luck. These products are not popular here. But there loads of 1000w and 3000w scooters on streets. Their parts are available but those motor are huge and i am not sure about their quality.

Regards to battery,
I searched and found that same capacity lead acid agm batteries(widely used in said scooters above) are 3 times cheaper than ncr18650s and 10 times heavier. And their cycle life are pathetic. With time, even most expensive 18650 batteries will come to same price because they would last longer. So i decided to invest in battery department. 3x10 36v 10ah pack is only 1.5kg! Though i might use 48v still searching. Cute q100 is also small. The convertion won't effect the image of the cx bike which i would like very much! It would make a very good hybrid system, half human power half electric.

Also an update note: As i search it, i started to love the hub motor mid drive systems. It is almost perfect. The problems said above dissappears all together at once, just the shipping cost problem remains. No need to touch wheels, no worries to snap dropouts or carbon fork and i still get to use my 2x10 sram drivetrain. Actually motor uses the sram drivetrain too! I think that is a major advantage. Can get low end torque with 28-32t rear and 34t front and can get high speeds with 11t rear and 50t front. But 250w wouldn't put too much stress on drivetrain would it?

Still so much to search. Will post it again. There is hope after all. If i finalise the design, i will accept the shipping cost and order anyway.
This is the bike that made me love mid hub design:
http://s451.photobucket.com/user/d8veh/media/Crank%20drive/SANY0133.jpg.html
All i have to do is produce a frame mount for motor, lose my apex cranksets LEFT ARM ONLY(so happy about this) and produce a left side crank arm with sprockets. I guess it wouldn't be too hard to weld or fix with nuts a sprocket to a crank arm.
This:
Plus This:

If you do not mind losing 1 crank on the right side then you can piggy the system onto your current crank setup something like a 1-10 and use the 2nd crank for the mid drive. 250w is not going to damage your drive train I don't think but then it is very low power. The mount looks very simply just a flat bar of steel bend into a U shape then you can find some U bolts to attached it to the frame. Putting the motor inside the triangle of you bike will reduce the space for batteries. Have you consider lipo? or have any experience to feel safe using them instead of Li-ion battery's.

That is a good idea. But i would like to keep two chainrings in front and use the complete range of 2x10 gearing. But you gave an idea! An extra chainring added to crankset spider from the frame side. There are bolts that fix chainrings to the crank arm spider. If i can somehow machine longer bolts i might add an extra chainring that will be driven by the motor. Just another alternative to left chainring.
Anyway i decided to start the project It will cost me roughly 500$ incl. shipping. All parts from bmsbattery. q100h, 48v 10ah li-ion and other parts are yet to be decided. All system will weight around 7 kg, which is nothing. I could have weight 7 kg more Bike will be under 20 kg and i am 75 kg so total weight will be lower than 100 kg.

But before buying there are things i should clarify and i should finalise the design. I am still researching the forum. For example i need to understand freewheel system and pedal assist. Like, do i need one or not? I know that geared motors allow to pedal while it stopped but that is when it used as hubmotor. Would that apply if in my application(since it will be connected directly to pedals)? I would very like to avoid using a freewheel if a can. That would permit the use of smaller sprockets. Lighter weight and possibility of lower gearing. I will also modify the motor so that it's shaft spins, not case. An awesome topic about this: https://endless-sphere.com/forums/viewtopic.php?f=28&t=45245 This would also let the use of smaller sprockets and the motor mount would be lighter and prettier

Other things that i have to clarify:

-Deciding how much power i will get from the motor. I thought at first that if it is 250w, that is that. Than i see most people don't use it lower than 500w

-Buying a battery pack from bms vs buying cells and doing it myself... Their 48v 10h batterypack looks clean. But as i understand they used 2500mah cells so it weights over 3kg. Sanyo 3350mah ones would be lighter. Price would rise a bit though.

-Using PAS or not. If i don't use PAS i have to constantly regulate power with a thumb throttle all the time. That would make a simplier build, less parts. But would that be inconvenient? I will keep the dropbar and attach the thumb throttle somehow. I expect to get a bit better range and top speed with better aerodynamics.

-Calculating the ratios. Bicycle's gearing range is between 34:32 and 50:11 so 1.06:1 to 4.54:1. I have to find the ideal sprocket teeth count on the motor and the added chainring. Also i have to find the best winding. 201, 260, 3xx etc.

@motomech Thank you for your input. There are couple of reasons i am going with quality bike-light motor and battery combination instead of donor old bike and powerful motor and battery combination. First, i love my bike and enjoy riding it. But i am not cut for everyday 50+km commuting on it. So the electric system will assist me. I won't sweat or get tired, hopefully.
Besides if i would put a powerful system on a cheap bike i just wouldn't pedal on it. After my bike it would feel really bad if i were to use it as bicycle. That would make it an electric motorcycle. And for the same price, 1000$, i can get a factory 3000w scooter which would make more sense.

Without freewheels, the pedals will turn when the motor spins, so if you aren't ready for it it will knock your feet off the pedals, or perhaps worse.

As long as you are aware and always ready for it, it's fine. If not....

amberwolf said:

Without freewheels, the pedals will turn when the motor spins, so if you aren't ready for it it will knock your feet off the pedals, or perhaps worse.

As long as you are aware and always ready for it, it's fine. If not....

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Thanks for your input. Looks like i have to use freewheel than. I suppose i have to put it on motor shaft, as putting a freewheel on crank side would be very hard. Reduction ratio will be higher, but no big deal. I will get plenty of reduction with shaft spin conversion anyway.

How are your fabrication skills? I found a decent articles from back in 2014 showing custom mid drive system with freewheel.

https://www.electricbike.com/roys-ecortina/

Or if you do not need that much power and just a bit of assist so that you can rest during long stretch of bike path then maybe a friction drive would be a good idea? With a Friction Drive you would not have to mess around with freewheel or chains. And most of the parts can be source from hobby RC stores. I do not know how well friction drive do on hills or when its raining but you stated that the commute to work was flat. With a friction drive RC setup you can make the battery small enough to bring it into work and charge it. This would allow you to reduce the expensive battery size you would need to make the 60km range.

https://www.electricbike.com/friction-drive/

BTW One-Punch Man is the bomb! can't wait for season 2 of the manga.

zhd said:

Thanks for your input. Looks like i have to use freewheel than. I suppose i have to put it on motor shaft, as putting a freewheel on crank side would be very hard.

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If it's on the motor shaft, it can never drive the chainrings, if it is there to keep the cranks from spinning. So the motor would never do any work, but the pedals will still try to turn the motor (putting extra drag on the pedals if the motor isn't powered).

That's assuming you are trying to drive the regular pedal drivetrain with the motor.

The only options (that keep cranks from spinning with motor, but let the motor help you move) are:

--no freewheel
--freewheel on cranks
--motor not driving chainrings at cranks, but rather separate chain to wheel

Last option has at least two methods:
--left side drive
--motor and pedals on the right side with independent singlespeed freewheels on each (several methods of doing this). But this takes out all the rear gears except one for pedals and one for motor.

Neither one gives you any gear changes in the motor, and only the left side drive leaves your pedal drivetrain intact.

Or build a totally separate gearshifting chain setup just for the motor (using an IGH as a jackshaft, etc), with the whole motor thing on a separate chain from the pedals.

In the non-hubmotor section, there are hundreds of threads about different drives and methods, with a little of the good stuff linked in the sticky index at the top of it. I'd recommend going thru that to see how middrives can be done, and then pick a method that suits your specific needs and parts.



(you could also build a front fork that will hold a rear wheel, using a rear triangle and front fork off of another bike, and install the motor system on that instead of your rear wheel, so that the motor can then use all the gears on the front instead, separately from the pedal gears. YOu'd still have to shift those gears, but you might be able to setup a double shifter that does both your gear sets at the same time. )

@amberwolf, Thanks for explaining to me, it is very helpful. I know now how i am going to do it if i will do a mid drive system.

But after Simonvtr's suggestion i looked at friction drives and they seemed that they would be better for my application. They are cheaper and lighter while being more powerful. I searched in forum and web and read a lot of articles. I decided to go with friction drive Motor swings with its inertia so you can use the bicycle without it if you want. It is very convenient. Total added weight will be around 6kg to 7kg.

All that needs to be done after buying parts is design a mount which i belive won't be a problem for me.
Parts are these:

Turnigy 6374 190kv 2750W!!! (or other kv ratings 149 or 168)
VESC or alienpower 12s 120a (vesc rated 50a continuous, so probably alienpower it is)
Turnigy Multistar 16000Mah High Capacity 6s X2 Series (Very good energy density and very cheap! two of them around 4kg. Bigger capacity than bmsbattery 48v 10ah pack while weighting same AND cheaper)
A servo tester
Thumb throttle
Maybe a charger? I have 6A Accucell from turnigy. Would that be enough or do i need something bigger?
Maybe a BMS? Hobby chargers have their balancing and checking modes so maybe i do not need.
I might try adding hall sensors to the motor.


Well, if everything goes well, for about 400$ i will have a 2+kw system! Very excited about it. I thank everyone here for sharing their experience and knowledge.