Surely this monster hub motor isn't suitable for a bicycle?

[alfantastic]

Spotted this monster hub motor on fleabay and was astounded by the shear power and speed quoted by the seller.

Monster Hub Motor 5000w 125km/h

They mention about using a downhill bicycle for the strength of the frame, but surely a motor of this power would snap bike wheel spokes really easily, making it virtually unrideable?
I was going through the odd snapped spoke when using a MAC motor with only 1500w

 

[Ohbse]

This is a 4 turn wind of a Cromotor clone. I run the Cromotor on my DH comp as do many others on this forum, personally at 7000-8000watt and it's not very stressed. Spoked wheels can handle a great deal more than that! Just because their ad says 125km/h doesn't mean it would reach it in reality, DEFINITELY not with the controller they have there. Not nearly enough power.

If you're snapping spokes it's not likely to be the motors fault, more likely spoke tension too low, spokes too thick (conversely from what you might think) or you're doing some big jumps with rubbish suspension

 

[alfantastic]

Thanks for the reply Ohbse.
I'm assuming you use a regular bicycle tyre on yours, so do you have any problems with traction, utilizing so much power?

 

[Ohbse]

None, other than perhaps too much. Running anything north of 240 phase amps of power I struggle to keep the front wheel on the ground but haven't ever struggled in the rear. 24" Maxxis Hookworm on the back

Different motor, but similar capability running same controller etc as I am: https://www.youtube.com/watch?v=MmuKBPBY67w&list=UUYY7iokzWjmrRT57cVcNadQ

Same bike has top speed now >120km/h so it's possible, but at the more extreme end.

 

[Dauntless]

http://www.alibaba.com/product-gs/1138310936/High_power_3000w_electric_bike_conversion.html

Only claims 3kw, should be good enough for a bike and still be able to rip a WalMarter apart. A whole kit for around $500, they list a too good to be true price for a battery, too. http://cnebikes.en.alibaba.com/product/760691473-212862823/48v_20ah_lithium_battery_for_electric_bicycle_battery_case.html

 

[dogman dan]

Above 2000w, in my opinion, you really do have a flyweight motorcycle that has pedals. Still a bike sure, but not likely to be seen as a street legal bike in any state of the USA.

Damn fun off road though!

If you really will be running above 40 mph, I would suggest motorcycle tires on both wheels. Both for durability, and for grip.

As you see in the ad, 147 mm wide axle. So you will have to stretch a steel frame, or some how modify an alloy frame, if the bike is 135 mm.

If you want a "bike", then the HS crystalyte motor has decent power, fits 135mm, and handles 2000w with ease. Why 2000w? I found a 2000w bike still gets me up long steep hills, even when loaded to 400 pounds. So it's enough without needing a special tire, special bike etc. More is fun sure, but 2000w will do what you need and still resemble a bike enough to not attract police attention.

 

[gogo]

If you want to put 1 HP to the ground at a crawl speed, you're going to need a big motor.

 

[crea2k]

Thats only 5000w, my cromotor on mine is 6000w continuous, 10,000 max

 

[MadRhino]

We are many here always waiting eagerly for the next, bigger, faster motor. When they say it's 5000w, we feed it 20kw

On a good DH frame built with the best components, tuned and balanced properly, you never have too much power.

 

[crea2k]

Thats mine :

 

[alfantastic]

Seriously folks, I bow down to all you monster power gurus.

You gotta have some big cojones to ride some of the beasts I've seen on this forum :lol:

 

[999zip999]

Ohbse I'm coming by for a test ride.

 

[100volts+]

20 Kw is the new 10 Kw. For real fun do it on a Walmart frame. That's freedom baby.

 

[Alan B]

Motor power ratings are so varied that it is almost a joke.

My Cromotor is stamped "3000W" by the manufacturer. I've put twice that through it and it was definitely warming up under load (didn't do it long enough to get hot). I've also warmed it up with 1-2KW over a period of time climbing grades. Not hot, but you might expect it would run cold at such low power. Especially if it was really a 6KW motor. I'm sure it will take 6KW under some conditions continuously, but only when it is operating in an efficient part of the load curve.

The venerable 9C's are rated at 500W or 750W or 1000W, depending on who's selling, and I've seen 10KW put to them. So what power rating is right?

In California the legal ebike rating is 1000W output. On a gradient you may have to put 2000W into a laboring hubmotor to get 1000W of work out because it is not running efficiently. Regardless of what the label says.

Comparing the 9C vs the Cromotor on the same steep gradient, the 9C struggles in a 26" wheel while the Cromotor easily glides up in a 24" wheel. The wheel size helps a little, but that's less than 10% different whereas the torque capability of the Cromotor is roughly double the 9C, and that is really the key factor.

So if you want an ebike that doesn't struggle on the steep stuff then using a more capable motor is one way to do it, even if you only put 1000-2000W into it. It will produce less heat and ascend those gradients effortlessly.

 

[crea2k]

My Cromotor eats hills for breakfast without even barely braking a sweat.

 

[Alan B]

My Cromotor eats hills for breakfast without even barely braking a sweat.

Exactly.

 

[dogman dan]

Definitely the motor in the first post is suitable for flyweight motorcycles with pedals.

He asked if it was suitable for a bicycle, and I think no.

I sure as hell didn't mean to say don't put it on a "bicycle" and go have a hell of a lot of fun. No doubt Mad Rhino has some damn fun,,, whatever you call them. I can't afford what just one front fork of his bikes cost. Go for it if you have a place to ride it, and the cash to put it on a suitable frame.

I think putting a motor this powerful on a cheap thin wall tube walmart bike frame is not a good idea. Too much frame twist, and those pogo stick shocks suck above 25 mph. You want the bike to turn when you initiate a turn, not just warp the bike. So if you have a cheap frame, at least be sure it's damn stiff one.

But if you do intend to pass for a bicycle, 2000w is plenty to do a lot, without the cops looking like this at you. And for that there are decent motors that have 135 mm axles.

I do agree though, that 2000w running into a wide magnet motor works better than 2000w into a narrow 9 continent type motor. So I do suggest a motor with 35 mm or more magnet. I love my 5304 and 5305 for the heavy load riding. Even with less watts, they just pull noticeably harder, presumably meaning less wasted heat.

My only problem with the really big motors is they don't fit 135mm. Go for a HS crystalyte if you just need 2000w. But if you need 5000w, then get the huge motor, and screw it whether you are a "bike" or not.

 

[friendly1uk]

I agree. Anything with that much power is a motorcycle. All legislation says so. I'm all for a bit of rule bending, but trying to justify 20 times more than allowed is a loosing battle. 500% more is equally as hard to swallow. Maybe double the legal limit is a reasonable time to call your push bike a motor cycle.

I know some outlaws can't even admit it to themselves. Using pedals as justification for calling it a push bike. Even while motoring along not pedaling they call it a bicycle.


No line has been drawn by this forum. The legal view is clear though. Not a bicycle if your not cycling.

 

[Alan B]

My last motorcycle would do well over 100mph and weighed around 400 pounds, and most of them these days are well beyond that. A bicycle with a big hubmotor is hardly a motorcycle.

More like a moped-plus, perhaps.

 

[MadRhino]

If it is built on a bicycle frame with bicycle components, it is an ebike no matter the power that it has or the speed that it goes. It may be illegal but the forum is not about law enforcement, it is about EV development.

A motorcycle is built on a motorcycle frame with motorcycle components, and normally it can be licensed as a motorcycle (that may be considered an advantage or not by various riders).

Then, some ebikes are more powerful than some motorcycles, their respective classes have nothing to do with power or speed.

 

[friendly1uk]

250w pedelec

Motorcycle?

 

[Chalo]

Seriously folks, I bow down to all you monster power gurus.

You gotta have some big cojones to ride some of the beasts I've seen on this forum :lol:

Whatever. My last motorcycle was tuned to deliver a dyno-measured 120hp, and weighed over 700 pounds. It's hard for me to "ooh" and "ahh" over a few kW of electric power.

I prefer low power e-bicycles to high power ones because they are much better as bicycles. High powered e-bikes are clumsy, oafish bicycles and rickety flea-bitten motorcycles at the same time. They're not scary because they are powerful; they are scary because they are incompetent machines.

 

[Ypedal]

but oh so much fun..

 

[zener]

Seriously folks, I bow down to all you monster power gurus.

You gotta have some big cojones to ride some of the beasts I've seen on this forum :lol:

Whatever. My last motorcycle was tuned to deliver a dyno-measured 120hp, and weighed over 700 pounds. It's hard for me to "ooh" and "ahh" over a few kW of electric power.

I prefer low power e-bicycles to high power ones because they are much better as bicycles. High powered e-bikes are clumsy, oafish bicycles and rickety flea-bitten motorcycles at the same time. They're not scary because they are powerful; they are scary because they are incompetent machines.

UhOh

Big heavy personal transportation monsters are the dying out dinosaurs.
Ebikes Fast & powerfull like cars are the future. For some of us even the actual reality.
Personal transportation don't have to be destructive and air poluting.

"High powered e-bikes" are not a threat they are the cure.
And the developement in the "High powered e-bikes" world knows only one direction same power less wight.
We all know what less wight means.

[youtube]lC4gPvQ9H1Q[/youtube]

 

[MadRhino]

Whatever. My last motorcycle was tuned to deliver a dyno-measured 120hp, and weighed over 700 pounds. It's hard for me to "ooh" and "ahh" over a few kW of electric power.

What about 20Kw on a 70 Lbs bike, that is making your 120 Hp, 700 Lbs motorcycle a very unefficient and clumsy bike.