Watts needed to replace a 125cc? (pun)

[datahar]

HI all,

Now I have a garage and funds have settled down after the house move, I'm finally in a position to seriously start a build!

Currently I go to work on a 250cc chopper, so would like the same 60mph-ish performance (who doesn't, I know) but 40mph would be acceptable (until upgrade day) if it acted like a 125cc I'd be happy, if it acted more like a 50cc then I might need a bigger budget.

The plan is to make a custom hard tail chopper frame, unless something really takes my eye, and use motorcycle parts for the front suspension. Then I will need to put it through the testing and get it road legal.
Things like:

and of course the awesome HOBO cruiser
http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=12810#p190144

Float my boat, but I want to get the hardware purchased before I start planning the frame

My stats for my commute (one way):
Total distance: 2.62 km (1.6 mi)
Moving time: 04:32
Moving speed: 34.56 km/h (21.5 mi/h)
Max speed: 77.12 km/h (47.9 mi/h)
Elevation gain: 149 m (487 ft)
Max grade: 19 %
Min grade: -3 %

I'd plan on charging at work, so a removable lipo pack that's good for 5 maybe 10 miles is all I would need, the only thing I need to decide on is drivetrain.

Would you recommend hub or mid-drive? Hub appeals for the simplicity but I am guessing I would need at least 3000w for the speed I am after? As hub motors have gone down in price recently it would make for an easier build.

I also have a Turnigy c80100 that I could utilise for a mid drive?

What do you think? What wattage hub motor should I be looking or, or would the turnigy be up for the job? If not what mid drive motor would you recommend?
Are the generic eBay offerings any good? there's a 1000w offering for £100, any potential in there?

 

[Dauntless]

So you have the right idea in the power of the 80100, but it's probably not going to hold up physically. Oops, your job is just getting more expensive.

So here's a more physically substantial unit in a hub motor, but it's probably closer to the 50cc than the 125cc, I don't know how much good a bigger controller would do. http://cnebikes.en.alibaba.com/product/1333913145-212862866/2013_NEWEST_3000w_ebike_hub_motor.html

And the price just keeps going up. This will cost you as much for just the hub, but we're at least getting to the power level you want. http://www.uumotor.com/shop/6000w-16inch-brushless-hub-motor-for-electric-motorcycle?cPath=16_27&zenid=87mcpvh8gad7juc1evtns5itq7 Or bigger power, bigger price. http://www.uumotor.com/shop/8000w-16inch-brushless-hub-motor-for-electric-scooter?cPath=16_29

Who's up next?

 

[amberwolf]

so would like the same 60mph-ish performance (who doesn't, I know) but 40mph would be acceptable (until upgrade day) if it acted like a 125cc I'd be happy, if it acted more like a 50cc then I might need a bigger budget.

Start saving up.

What wattage hub motor should I be looking or

You'll need to go to the simulators (several listed in the ES wiki) and see what power you need for the speed, terrain, weight, rolling resistance, wind resistance, and acceleration you are after.

Then I highly recommend you read the "noob 50MPH" wiki entry, whcih links many many threads discussing this kind of power level and other associated stuff.

After that, then you'll be able to come back and figure out the exact numbers you'll need, and you'll have a much better understanding of the list of problems you'll need to solve.

And yes, it is a lot of reading.


BUT the very first thing you have to do, if you want something road legal, is to go find out from your local government facility for such things exactly what the requirements are for such a vehicle, and start your whole design based around those.



Just to give you a quick idea, it takes 2500-3000W, with two hubmotors and two controllers and a 20AH 14s EIG NMC pack (or a 10Ah 14s RC LiPo pack) just to give my CrazyBike2 ~4 seconds 0-20MPH acceleration. Me plus the bike is around 330-350lbs, typically. I don't ride past 20MPH so I dunno what it's actually capable of for speed.

 

[friendly1uk]

Think 1000W=1hp But remember an electric hub has no gears to change, Just a nice wide power band.

 

[amberwolf]

Think 1000W=1hp

Last time I checked, 1kW is closer to 1.25hp...or 750W is about 1hp.

Though I guess when you need a lot of power, it doesn't make all that much difference.

 

[Dauntless]

Interesting question on the power. A 50cc moped or pocketbike is supposedly putting out 3hp, but the specs say 1,200w. A 250cc engine, 16hp, right? But if it can, it'll only do that at maybe 5,600rpm, you won't be winding it up like that when you ride normally. So do you really need to compare the continuous power of an electric motor to the peak hp of a gas engine? That 1,000w hubbie probably isn't so far off what a moped or small pitbike would do.

 

[datahar]

Thanks guys, Luckily I have found my receipt for the turnigy, bought 23.02.2012, 3 years to actually starting the project isn't bad for me! :wink:
The receipt was important as I can prove the motor is new then when it comes to registering it as a kit bike then if I can prove all new parts I can get a brand new year license plate and not the usual Q plate! Means I can't cheat and use cheaper used parts, but for a real license plate, it's worth it to me.

So the build will commence with the turnigy, it's the 180kv version though, I am thinking a centrifugal clutch somewhere in the reduction box, that way I can stay sensorless, as it's the starting that sensorless outrunners suffer with?

Over the weekend I am going to plan the frame, then I can then get an idea of the weight so I can start using the simulators properly. I am also going to plan it for a MARS 10KW or maybe the golden motor 20KW for when I want more speed

As I won't be using a hub motor then, would an aluminium brazed frame work OK or shall I stick to steel as the safe(r) option? Aluminium I can braze, steel I'll need to practice...

@dauntless, the continuous vs peak ICE power was exactly what I was trying to get across, you worded it so much better! My chopper is meant to be rated at 16hp at the wheel, but it doesn't have a rev counter, so I couldn't tell you what I average for a true comparison : -( not that I'm aiming for 250cc performance straight away anyway

Thanks for the kinder than they could have been replies! I was kinda hoping NOT to sound too much like the I'm a noob and I want to go 50mph, but at least I'm going down the motorcycle component route, and besides I really wanted 60mph :wink:
My commute is about: Half mile @40mph, half mile @60mph, half mile at 40mph, then just under half a mile @30mph. On a motorcycle anyway, very excited to see what something I can create can do, without breaking the bank too much (it's the pre project optimistic, I know it's going to cost me a fortune, but saving money is not why anyone does this I'm sure)

 

[gwhy!1]

I dont think just one 8085 or 80100 will hit your goals ( but depends you what you are looking for in real terms performance wise) , think very carefully about making your own frame it can become a massive minefield if you want to get it reg'ed ( at least find a 50cc old frame/log book that you can just cut the frame number out and fit that into you new frame some where anything 50cc or below is less hoops to jump through )

 

[parabellum]

Think 1000W=1hp

Last time I checked, 1kW is closer to 1.25hp...or 750W is about 1hp.

Though I guess when you need a lot of power, it doesn't make all that much difference.

I follow the thumb rule 1kW electrical input=1hp mechanical on the road.

 

[friendly1uk]

75% efficiency is a reasonable expectation.

The article on Bosch making E-M/C parts stated 600w was equivalent to a 50cc. Pure spin of course. Based on the width of the power band not peak. Though in use they have a fair point.

UK legislation offers a prospective.
50cc must be below 4kw.
125cc bikes 11kw/14.6bhp

 

[datahar]

think very carefully about making your own frame it can become a massive minefield if you want to get it reg'ed ( at least find a 50cc old frame/log book that you can just cut the frame number out and fit that into you new frame some where anything 50cc or below is less hoops to jump through )

Thanks but wouldn't cutting the frame number just result in a 'radically altered frame' meaning the same MSVA as a new frame anyway? Or is the aiming for the 50cc category what you are suggesting?

I think I am going to go with the hub motor route for now, the mid drive I know has the potential to produce greater speeds with a different motor in the future, but for now I will focus on the frame and getting in registered, so an easier drive chain may see it completed in the same year I start in

Just need to convince the missus I'm not mad and get this ordered:
http://www.aliexpress.com/item/High-Quality-E-bike-spoke-motor-3000W-Brushless-DC-Hub-Motor-for-Rear-Wheel-E-bike/2045060945.html

Unless you would suggest the Golden Motor 1000w at 72v as the better solution? From other's builds 40mph is achievable, keeps the voltage down, so smaller battery/ quicker charge time and from what I've read the GM has the larger torque of the 2? but I know it's hot rodded vs allowed tolerences (or at least the labelled and presumed ones)

Cheers

 

[gwhy!1]

Im assuming by having a existing log book and frame number it will cut out a lot of bother .. Im just going by some knowledge i gained from people that made ther own MC trials frames and then wanted to get them reg'ed but never gone through the process myself. The rules for a 50cc conveted reg'ed bike is slightly easier than above 50cc as long as the weight is still ok , again I have never gone through the process but have been told by a vehicle examiner that at the moment its the easiest way to get a converted bike back on the road. What ever way you decide to go please keep us informed as it will all good information.

 

[parabellum]

think very carefully about making your own frame it can become a massive minefield if you want to get it reg'ed ( at least find a 50cc old frame/log book that you can just cut the frame number out and fit that into you new frame some where anything 50cc or below is less hoops to jump through )

Thanks but wouldn't cutting the frame number just result in a 'radically altered frame' meaning the same MSVA as a new frame anyway? Or is the aiming for the 50cc category what you are suggesting?

I think I am going to go with the hub motor route for now, the mid drive I know has the potential to produce greater speeds with a different motor in the future, but for now I will focus on the frame and getting in registered, so an easier drive chain may see it completed in the same year I start in

Just need to convince the missus I'm not mad and get this ordered:
http://www.aliexpress.com/item/High-Quality-E-bike-spoke-motor-3000W-Brushless-DC-Hub-Motor-for-Rear-Wheel-E-bike/2045060945.html

Unless you would suggest the Golden Motor 1000w at 72v as the better solution? From other's builds 40mph is achievable, keeps the voltage down, so smaller battery/ quicker charge time and from what I've read the GM has the larger torque of the 2? but I know it's hot rodded vs allowed tolerences (or at least the labelled and presumed ones)

Cheers

Im pumping 10kW battery in a 500w Mxus DDhub, embracing 125cc Chinese bikes on green, up to 50kph, they still can reach me shitting their panties loudly.