75km/h E-bike with Passenger Seat. Help

[marcovita]

Hi,

Im completely new to this forum but its very clear this is where the knowledge is at.
Im looking for advice on what I've chosen to build my 2 seater that will go roughly 75km/h.

Here's what I'm hoping to use, please let me know if I'm a dreamer or if this is possible.

Bike - 2009 Norco Kathmandu (kijiji)

Motor - Phoenix II Crystalite kit 7240 (electricrider)

Batteries - Two 36v 20ah LifePo4 wired in series for my 72v 20ah (pingbattery)

I am hoping to fit the two batteries within the triangle of the bike between my knees as i believe that is the best place for the weight.
I will build a bracket for the passenger seat above the rear wheel, as well as a torque arm.
Don't know much about modded controllers nor how to balance cells using a BMS.

I could really use some words of wisdom.

Thanks,

MarcoV

 

[bowlofsalad]

How will you seat two?

Your location is unknown, but I'd bet anything that you'd get pulled over if you were spotted going that fast. You'd be lucky to be going 35 in most places on an ebike and not get pulled over if a cop saw you. That is motorcycle territory without a doubt, the speed you are looking at going.

I don't know anything about that motor, but I am unsure that you would be able to attain your idea speed, personally I highly doubt it at 72v. In addition to this, the power consumption at that speed would be extremely high, you wouldn't go far with that many watt hours. You will need to spend much more to get that speed, but the range wouldn't be there. Check out ebike.ca/simulator Play around with it and get an idea of speeds you can attain with various voltages.

 

[Willow]

Most defenitely motorcycle territory. Adding the battery weight alone to a bicycle can be enough to make things unsafe. Motorcycle frame, suspension, brakes and tyres are a must if you want to carry an extra passenger.

Maybe consider building two light weight bikes - using your two 36V packs. Keep it simple.

 

[SamTexas]

Hmm....

1) 75kph on a bicycle carrying a passenger.
2) Two - 36V, 20Ah LiFePO4 batteries inside the triangle

Well, I don't have any word of wisdom to offer, but I would really love to see your dream machine come true.

Seriously, that plan is overly ambitious. I'm not saying it can't be done. With sufficient time and money almost anything can be accomplished. But since this is (apparently) your first ebike, I suggest you cut both requirements in half, so:

a) 37.5kph with a passenger
b) One 36V, 20Ah LiFePO4 inside the triangle.

Welcome to ES. Good luck and have fun.

 

[cassschr1]

I'm wondering who that passenger is. They will only be there once.

 

[neptronix]

A Yuba Mundo ( or Boda Boda ) frame would be a safe way to do this. They were designed for these loads.
A dual suspension aluminum frame would be the mind blowingly unsafe way to do this.

But you are in motorcycle territory with this 75kmh speed. There's nothing legal about doing that kind of speed on a bicycle and you are going to get busted. Bicycle brakes will never be adequate. Forks will never be adequate to take the front braking force. it's just too much speed for a bicycle.

Start with a good ol' steel motorcycle/scooter frame and think chain drive or large hub motor, like one of John in CR's hubs, or larger than that.

Keep dreamin', but dream about something that's not a bike :]

 

[The Stig]

Draw or post pics(see what you can find on google) of what your thinking for the 2 seats because normally bicycle frames will definitely not take the weight of two people. Maybe the toughest of tough DH frames used for easy riding on the street, but definitely not 75km/h. For those speeds and loading capacities we're talking heavily built(compared to bicycle) scooter or motorcycle frame.

Its ok to be dreamings a bit, but start developing your ideas in realistic directions.

 

[Philistine]

I think the title of this thread is what the passenger will frantically text message to their loved ones from the back of the bike as the last thing they ever do.....

I don't know where you live, but here in Australia, you could almost have a game show or a competition, where you are given an ebike with a passenger seat and passenger, and you have to ride at 75kph and see how long it takes to get arrested. It would be a 30 minute show, with an average of 60 contestants on each episode.

If you are deadset on proving the cowards wrong, check out some of John in CR's bikes. I believe he carries passengers on some of his bikes, and because he lives in a non-nanny state country most of his bikes do that speed.

 

[dogman dan]

Gee, I hope you didn't click "buy" on any of that yet.

Especially the battery, that will die fast used that way. Of course, you might die first.

Start thinking closer to legal speeds, and look at cargo bike frames or tandem bikes.

 

[John in CR]

You guys crack me up. If someone takes a bike and points it down a hill going that speed or higher, taking jumps and hitting bumps and rocks on the way down, you'll be cheering them on, but heaven forbid someone strap a motor on a bike and go 45mph on a flat level paved surface. :lol:

Marco,
Make sure you have good brakes. I'd like to see how you plan to make a 2 seater out of that bike. Personally I'd look for a steel frame bike. They're much easier to modify, and they give plenty of warning before failure.

John

 

[marcovita]

Wow! Thanks for all the replies!

I see I have to change my goals a little bit.

Speed - 75km/h (top speed) with 1 rider (160lbs + 80lbs bike)
Passenger Capacity - 1 Passenger seat (used for short rides, no faster than 35km/h)
Range - I need to get to work and back so as for range all i need is 20-25 km (theres one hill, not steep but its pretty big)

Heres a pic of the bike + the layout of the changed id like to make to it.



Let me know what you guys think.

MarcoV

 

[neptronix]

Sorry, unless you and your passenger are really, really light ( like 100lbs / 40kg each ).. that frame is not going to hold 2 people, it's not that strong. You need a bike designed for the task. That frame is designed for light weight, not carrying.

Also, you cannot fit much battery on that bike; you will find that 75kmh drains whatever battery you can fit in the triangle within about 10 minutes or less.

You will also not hit ~45mph ( 75kph ) on 40a x 72v. That's just 2880W. You'll need 3000-4000W to maintain that speed. You won't break 60kph and the motor might overheat before you drain the battery anyway if you're using a 26" wheel.

http://ebikes.ca/simulator/

Check what you're doing in the ebikes.ca simulator and you'll see what i'm talking about.

I think you are shooting way too high. Again, start thinking about a motorcycle frame that can reasonably handle 2 passengers, or a cargo bike, but ONLY if you are not exceeding about 50-65kph.

 

[marcovita]

Ebikes/simulator is great!

Not sure how to measure my resistance though.

Heres a vid of the kit im planning on getting. Hes doing 70km/h and carrying a 72v 40ah battery pack so im hoping i can do around the same seeing as ill be a bit lighter (20ah). Dont need it for more than a 2 km stretch.

[youtube]http://www.youtube.com/watch?v=s5sa6fC5Hig[/youtube]

Its very important that i dont leave the bike world. Ill sacrifice the 2 seater in order to stay here but motorcycles are a whole other thing. For parking/stealth factor its very important that i can pop this thing into a bike rack as well as talk my way out of confrontations with police.
I'm in Montreal, QC, Canada. And aside from the 500w motor i had a few years back ive seen maybe 6 other e bikes. I dont think they're on the radar yet here.

Heres an updated pic

MarcoV

 

[dnmun]

first thing is to make a replica of the ping pack from cardboard. make two individual boxes of the same size as the pack and then see how you can mount it on the bike. after that you can find a bike that will work.

 

[marcovita]

Hey

Just bought the bike off kijiji for a great deal. It's in great shape.
Here is a pic of the layout of the cut out batteries made to scale (2x 36v 20ah)

What do you guys think about this setup? I realize that a 7240 controller would
only let me go full throttle for about half an hour. Is this motor/controller/batteries/frame a setup
that will allow me to do at least 65 km/h, 30 km range ?

Thanks,

MarcoV

 

[marcovita]

The top battery i realized will have to be closer to the handlebars as it disrupts my thighs when i pedal.

 

[neptronix]

72v 20ah is going to be extremely heavy, like 24lbs of battery alone. You're looking at a motor that is something like 24lbs as well. The bike will weigh what, 30lbs? Then you gotta add the controller and mounting stuff... your bike is probably going to be in the 85lb range. It isn't gonna just pop on a bike rack.

I think you are underestimating the weight of this stuff. Also, how are you going to prevent a battery hanging over the sides of the bike so far from tipping left and right? this is going to require mounts that conform to the shape of the tube, and would be rather heavy as well.

 

[marcovita]

Correct. I will have mounts preventing the batteries from moving around but im hoping to make them out of plastic. Either way, my bike will probably weigh more or less 90lbs. Maybe 100 if i find room to put in my two 36v chargers. Are my goals reasonable or am i better off with a modded controller and building up my 72 volt batteries with single cells?

 

[dnmun]

nope plastic won't cut it. you might look to see if you can get them so they mount on each side of the head tube. above the fork with a bracket strong enuff to hold them and allow the cables space to clear. far enuff back to just clear your knees.

this is the other reason people go lipo.

 

[neptronix]

Plastic won't do it at all. Not when you have 12 pounds ( RC Lipo ) - 11 pounds ( samsung NMC or Panasonic NMC ) vibrating, bobbing, and tilting along as you ride.

Going with single cells would help you produce a better shape, but you've still got 22-24 pounds of battery to figure out how to mount solidly.

dnmun's idea of putting them along the sides of the bike is better but this might interfere with pedaling. I'm not sure how you'd mount it up though. That would be more secure but more difficult.

You're trying to jam too much battery into a very small frame not designed for it.

This is what 36V 30AH of RC Lipo looks like in a frame with an actually large triangle. You could configure this to run 72V15AH. You'd just need a large frame to jam all that in the center.

http://endless-sphere.com/forums/viewtopic.php?f=4&t=29211

 

[marcovita]

That looks pretty neat.
Ill scrap the idea of plastic and maybe just use that for the casing. As for the brackets I'm thinking fiberglass.
I did the measurements and the batteries just barely fit where I want them. One in the triangle and one above
the beam. Tried to make a makeshift casing with the cardboard batteries inside and I've got just the right amount
of clearance so it doesn't disrupt my pedaling. I'd also like to stick a dirt biking seat with a spring under it so I can
Still pedal (it's thin enough) and with some proper reinforcements stick a second person on.

Nervous to buy my batteries or my motor as they're both big purchases.

This is the idea and gives me the clearance I need.

Let me know what you think.

MarcoV

 

[Drunkskunk]

Your project is ambitious.. As someone who has built bikes that can handle these speeds, I have some sugestions.

Start with a cheap 9C/MXUS/Clone motor. You're going to run into a thousand problems with this bike, and it's better to do so on a cheap motor that won't overpower it too soon. Find the problems before they kill you.

The fork isn't going to hold up. A single crown fork is Iffy on a fast bike, but at high speed And high weight, it's not going to last, But that bike is even worse, in that it has a bottom end fork that needs replacing. Go with a Double Crown Fork from Marzocchi or Fox, or Even Rock Shox. You'll want something designed for DH riding.

Brakes. I can tell you stopping from 65KPH causes my 230mm rotors to get hot enough to warp. I have a small burn on my finger from yesterday's ride where I bumped my rotor with it 10 minutes after a ride. My bike is capable of hitting 85kph, but I've limited it's speed due to the braking issues. your bike has tiny little 160mm rotors, and will be carrying more weight. Expect the brakes to fail.

That frame may be able to handle a passanger of 50kg or less if you keep the speed down to 20kph or less. But from experiance, they're going to do a lot of screaming and begging you to slow the "F" down at speeds much over 10kph. A bicycle is not a motorbike. Also, the handling will Suffer in the extream on that short wheelbase and close sitting arangement. Also expect this practice to wear out parts fast, Including the frame, unless yuou have a parts group ment for a tandem bike. My first Ebike was built this way, and It had to be retired due to excessive wear.

 

[marcovita]

That's depressing. Just bought the bike and it seems like ill have to put about 1000$ into it.
Could I get away with getting a 240mm disc on only the front wheel?
And without a passenger, would the brakes, fork, and frame still be a big problem?

 

[SamTexas]

Why are you so set on 75kph? What is the real reason?

All your problems would magically disappear if you reset your goal to about 40kph.

 

[mlt34]

I would say right now, the best advice to you would be to WAIT on the purchases of the battery and motor so you can do a little more planning. I think you've realized that based on just about everyone's advice you need to re-evaluate your goals. Your plan is barely even physically possible, and definitely not safe. You're simply asking for broken parts (best case) and broken bodies (worst case) if you still want 75 km/hr on those components. If you were to change to a high winding of 9C style motor you could easily achieve 50 km/h on just 48V. That will make the battery easier to fit inside your frame, allow you to still pedal (or pretend to pedal when you see cops) and also save you some money and weight. The 26" Q11 kit (basically a 9C) from BMSbattery.com does a no load speed on 48V of about 60 km/h and a loaded speed of about 50 km/h. Plus it's only $150.

By aiming for a more reasonable 50 km/h, you can still use the bike you already invested in while staying within it's relatively safe operating parameters. I'd still upgrade the front disc to at least a 180 if not 200 though. And like someone said above, don't attempt a passenger trip at more than 25 km/h. It would practically be safer to give them roller skates and put them on a tow rope.