Downhill E-bike project . assistance and knowledge needed

[subwoffer13]

hi guys . i was surfing the web when i found out about the "Stealth bomber" e bike . bad-freakin-ass bike , witch is looking even better than a couple of dirtbikes ( imo )
good looking it's not the only aspect on this one , he's also powerfull as hell ( 4500 w motor ) ..
anyways , before buying it , i was thinking if there's any way to save up some cash and build my own decent downhill e bike . ( bombers price is 9500 $ , no taxes or shipping included )

i'm pretty much newbie at the topic , so do not throw rocks please .


1. how should i make it torque advanced? i mean , 45 km\h is more than enough for me , any other source of power i'd like to put in torque , to handle offroad .
2. i have no idea what wattage on the motor will satisfy my urge for instant power , so can you please guide me to the right direction . ( i was thinking 3000 w )
3. if i'm getting 3000 watt motor , will my 48 v 12 MAH will be enough ? i guess not .

p.s

i'd like to get a pro opinion about a decent setup i should make for more torque powerfull than max speed dirt bike

thank you !

 

[MadRhino]

You can build better than a Stealth Bomber, or Fighter that is a better platform IMO.
Starting with a good DH racing bike, making dropouts to fit a big hub motor, fabrication of battery enclosure(s) for a frame that is really not made for this, custom mod and tuning to the rear suspension, upgrades of many components... Lots of work and a fair amount of money.

10+ Kw is making a mad dirt bike out of a good light weight DH rig, and that is where the fun begins. Your target speed and power are very low, very easy to achieve. The slowest of my dirt bikes is doing 65 Kmh and uses peaks of 12 Kw. I don't know about your battery, what is important is the discharge C rate to give you Amps for torque. Most of us who are building powerful dirt bikes are using RC Lipo for their high density and aggressive chemistry.

Then, if you need low speed and high torque, you might want to look at mid drive setups. They are optimal for this purpose, but require more fabrication and maintenance.

 

[wesnewell]

Please go to the User Control Panel, select Profile, and then enter your city, state/province, and country into the Location field (country minimum). This will help people help you. Example: Wylie, TX, USA. Without knowing what country you are in it's hard to make any recommendations. Thank you.

 

[parajared]

Stealth bomber has that unique transmission than makes it so expensive. That is hard to beat with a home brew setup. I always thought it would be cool to do a build with a go-kart transmission, a big mid drive motor, and a motor bike chain to the left hand side of the rear wheel.

 

[subwoffer13]

thanks for the reply guys .

i've updated my location , and hopefully i'll find any locals ( chances are close to zero i believe ) . i've never seen E-bikes here exept the " city style " ( 36V battery with 250 w motor .. a joke ) .
im also could't find a place that sells motors with higher wattage than 1000 ( maybe 1500 ) . but that is not an issue , i'll order online .

anyway, i was looking for a bit more specific suggestions . i mean , i believe i have the the skills to assemble and finish this project , but unfortunately i've never been into electrics , so this is my weak spot .
so if you could suggest a specific parts , i'd be more than thankfull .
as i said i'm looking for :
speed : 45-50 top
Torque : enough to know that when i'll need the power , i'd be able to squeeze the throttle and handle most of the offroad terrain . and by handle i mean easily and fun way , not just to make it over the hill .

so , i need to know :
1. battery type
2. control console type
3. hub motor type



as soon as i'll get 3 of those , i'll be ready to move on and search for a DH bike .

 

[MadRhino]

so , i need to know :
1. battery type RC Lipo, or any other that can supply high C rate
2. control console type None, ideally. Crashes break anything on your handlebar. I use half twist throttle and switches and that's it. It is good to use a Cycle analyst at first rides, to know your system range and power surges, then you leave it on a shelf until you mod something and need it again.
3. hub motor type Big DD hub

 

[Ariane]

Ok,

You want the bad ass ebike on the planet with an impressive torque that motocross can be jealousy you, flying over any hills that CR450R fourth stroke is to shy to climb ?

Then buy a Cromotor or a Chrystalite 5XX or even better a Hub Monster motor from John in CR and mount this motor as mid-drive, build your own frame and swing arm and gear it down for max 50 Kp/h.

And feed this baby at 90 Volt with a 30 Amps Lipo pack. Use 16" rim, motocross tire and you can throw sand and dust every where you want with this light package..

Good day!
Black Arrow

 

[dogman dan]

Yep. Big ass motor. Insanely high c rate battery of 72v minimum, but likely more. Then bolt it all onto a bike that costs half a years pay. Basicly, none of it will be ordinary "bike stuff", nor an ordinary bike. It won't be light when you get it put together, but it will be light compared to most motorcycles.

Now, you can do some nice riding on a lot less. But you won't be flying off the tops of those hills.

 

[Tinto]

These frames may be of interest if you don't plan on pedalling (although I believe pedals may become an option).

http://endless-sphere.com/forums/viewtopic.php?f=3&t=48089

 

[wesnewell]

thanks for the reply guys .

i've updated my location , and hopefully i'll find any locals ( chances are close to zero i believe ) .

Certainly zero if you don't save the location you entered. IOW's no one knows if you're in the US or Antarctica.

 

[Drunkskunk]

My advice: Build a normal ebike first, something in the 1000 to 1500 watt range.
Ride the hell out of it, melt the motor, break everything at least once. Learn how to make it fail, and learn how to keep it from failing. THEN start planning your Badass dirtbike.
The experiance you gain from it will save you thousands of dollars, and ultimatly give you a better bike.

 

[subwoffer13]

i've tried to find RC Lipo batteries on the web but i didnt find any to fit a e bike ( they're for RCs ) .

what if i'll use two of those ?

http://www.ebay.com/itm/48V-40AH-LiFePo4-battery-Lithium-Electric-Bicycle-Scooter-EBike-Rechargeable-/221231241980?pt=US_Rechargeable_Batteries&hash=item338268dafc

My advice: Build a normal ebike first, something in the 1000 to 1500 watt range.
Ride the hell out of it, melt the motor, break everything at least once. Learn how to make it fail, and learn how to keep it from failing. THEN start planning your Badass dirtbike.
The experiance you gain from it will save you thousands of dollars, and ultimatly give you a better bike.

nah , i dont want to spend money on a "beta" bike .



p.s

your profile pic bike is goddamn good looking one

 

[Racer_X]

what if i'll use two of those ? http://www.ebay.com/itm/48V-40AH-LiFePo ... 338268dafc

wow only 25 KILOS for those batteries. Are you kidding?

i've tried to find RC Lipo batteries on the web but i didnt find any to fit a e bike ( they're for RCs ) .

The link below will show you all you need to know about how to make RC Lipos ebike friendly.

Lipo noob thread links.
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=19956

 

[wesnewell]

i've tried to find RC Lipo batteries on the web but i didnt find any to fit a e bike ( they're for RCs ) .

Batteries are batteries, Put them on a bicycle and they're bicycle batteries. You make your own battery pack using rc lipo. Most people get them from HobbyKing (HK).
http://www.hobbyking.com/hobbyking/store/index.asp
You can string them and parallel them to any voltage and any AH you want. The C rates are high enough you can use a small pack you could carry in your pocket to power an ebike or you make a really high voltage pack to power a car. Until they come out with something smaller and lighter with as much power, it's all I'll use.
I don't know where you can buy hub motors in Israel, but I hear they have some strict customs laws regarding wattage. At minimum, I'd think you'd want a 1000W hub motor that can take 4000-5000W of powers for short burst and cruise at 50kph all day long. You can put together a bike like that for under $1000 here.
Suggest you start with the wiki.
http://www.endless-sphere.com/w/index.php/Main_Page