8fun crank drive kit

[banbury frank]

Hi we will be testing the new 750 watt motor soon with our 48 volt 15AH frame mount KUBE battery that has a 50A BMS

But will only be selling the complete Kit £1495

Frank

 

[shemozzle999]

I'm a new member and, based on my interpretation of the advice I've had so far, am interested in converting my bike (photo attached) with a crank drive.

View attachment 7275

I've not had the chance to try one yet but wondered what the forum thought about the 8Fun's power to get my 85Kg up our steep Yorkshire hills?

Hi CoachMark, welcome to the forum.

The first consideration would be mechanical, would the motor be able to be physically assembled onto your bike without obstructing any existing cable runs. At present it is only offered with a 46T chain wheel and multi chain wheels cannot be used.

There are too many variants to consider when asking about power requirements, see the bicycle power calculator thread, to be able to give you a definite yes or no answer to your question.

There is a mechanical advantage to using this motor i.e. you feed the power through the chain and can change gear to accommodate varying inclines.

 

[CoachMark]

Hi CoachMark, welcome to the forum.

The first consideration would be mechanical, would the motor be able to be physically assembled onto your bike without obstructing any existing cable runs. At present it is only offered with a 46T chain wheel and multi chain wheels cannot be used.

There are too many variants to consider when asking about power requirements, see the bicycle power calculator thread, to be able to give you a definite yes or no answer to your question.

There is a mechanical advantage to using this motor i.e. you feed the power through the chain and can change gear to accommodate varying inclines.

Thanks Shemozzle999, I'll take a look at the power calculator thread this morning.

In terms of cable runs I think I'll be OK since it's a cross bike and all the cables run on top of the top tube, and I'll be removing the front mech completely because of the single chain ring. The cable for the rear mech runs down seat stay.

I was running a 50/34 compact chainset at the front and 11/23 cassette on the rear but since I suffered a medical problem last year (I have to keep my blood pressure as low as possible) this gearing would be far too hard for me now any way (hence the investigation into a Pedelec). I was thinking of putting a 11/34 cassette on and this should be OK with the 46T chain ring.

 

[shemozzle999]

Sounds OK.

I can only think of one other problem, to overcome any motor run on you would need to fit these 2 wire switches at the wheel cable ends to retain your existing brakes. They would need to be spliced onto the cable form supplied.

Aliexpress.com : Buy electric bike brake sensor popular in Holland, Germany from Reliable sensor car suppliers on Golden Way Cycle (Hangzhou) Co., Ltd.

As for a battery solution perhaps this could meet your needs - 50 cell 36v,13Ah.

Aliexpress.com : Buy Newest 36v 13ah bottle battery LiNiCoMn for electric bike / e bike bottle battery from Reliable bottle cutters for sale suppliers on nne-bikes

 

[CoachMark]

Sounds OK.

I can only think of one other problem, to overcome any motor run on you would need to fit these 2 wire switches at the wheel cable ends to retain your existing brakes. They would need to be spliced onto the cable form supplied.

Aliexpress.com : Buy electric bike brake sensor popular in Holland, Germany from Reliable sensor car suppliers on Golden Way Cycle (Hangzhou) Co., Ltd.

As for a battery solution perhaps this could meet your needs - 50 cell 36v,13Ah.

Aliexpress.com : Buy Newest 36v 13ah bottle battery LiNiCoMn for electric bike / e bike bottle battery from Reliable bottle cutters for sale suppliers on nne-bikes

I've tried the power calc software and if I used it correctly says that I'd need to put in c300W at the pedals to climb a 10% gradient at 6mph; I don't know how much power I could comfortably apply myself though, although I would have thought that it would be at least 50W. Whilst useful these calculators are no substitute for trying a bike. I plan to hire a rear hub drive bike in a couple of weeks to see how I get on with that - trouble is that crank drives aren't as that common so probably would have to travel quite a way from where I live in Bradford to try a crank drive.

Is there much motor over-run? Thought of trying any splicing myself is pretty scary! [I'm OK with the mechanics but never been good with electrics or plumbing for that matter ]

 

[shemozzle999]

Yes agreed, it is really a case of suck it an see.

They are pretty rare beasties at the moment, I know some members have them but I don't know where they are located. If you could get to Milton Keynes, Cyclezee has a demo bike you could try.

Regarding the brake switches you only need to join 2 wires coming from the switch to the 2 wires on the cable form. You could at the simplest level just twist them together then insulate them with some tape.
They are not polarized so you can not get them the wrong way around.

 

[CoachMark]

Yes agreed, it is really a case of suck it an see.

They are pretty rare beasties at the moment, I know some members have them but I don't know where they are located. If you could get to Milton Keynes, Cyclezee has a demo bike you could try.

Regarding the brake switches you only need to join 2 wires coming from the switch to the 2 wires on the cable form. You could at the simplest level just twist them together then insulate them with some tape.
They are not polarized so you can not get them the wrong way around.

Thanks again for your helpful advice. I've exchanged a few emails with Cyclezee before I joined the forum so know about his demo bike but it is just so far away. I think I've found another up in the north-west but that isn't such a good comparator to my bike (its a cargo bike).

 

[shemozzle999]

What's the best 48v frame mounted battery to go with the 750watt unit.

Sent from my GT-I9300 using Tapatalk

Hi big_gems,

I suggest you contact Frank - his test units should have arrived by now:

http://www.pedelecs.co.uk/forum/electric-bicycles/14590-8fun-crank-drive-kit-17.html#post191449

I expect he will be starting his own thread to show the results.

 

[CoachMark]

By the way I meant to ask what happens if the speed sensor on the wheel came off; does the motor stop?

 

[shemozzle999]

By the way I meant to ask what happens if the speed sensor on the wheel came off; does the motor stop?

The speed sensor is required only for the speedometer on the display.

I believe it is only required to be fitted on initial setup when the system performs a POST check and will report an error code if not installed.

Once all the parameters have be set and saved subsequent startups will proceed normally whether fitted or not but you will not have any read out of speed on the display, it will remain on zero.

If the your purpose of the question is regarding de-restricting the motor then you will be disappointed but if you are just worried about a sensor malfunction then no problem it will still drive the motor.

 

[Deleted member 4366]

If you buy your kit from these people, they can remove any speed limits for you. You have to ask for it. I don't know if that means that you can still set an optional limit, you'll have to ask.
48v 500w 8fun/bafang/bafun motor BBS 02 Center/mid drive /Crank Motor eletric bicycles conversion kits-in Electric Bicycle Motor from Sports & Entertainment on Aliexpress.com

 

[shemozzle999]

If you buy your kit from these people, they can remove any speed limits for you. You have to ask for it. I don't know if that means that you can still set an optional limit, you'll have to ask.
48v 500w 8fun/bafang/bafun motor BBS 02 Center/mid drive /Crank Motor eletric bicycles conversion kits-in Electric Bicycle Motor from Sports & Entertainment on Aliexpress.com

Excellent information, apart from the reference to BBS02, shame you posted it on the wrong thread.

 

[CoachMark]

The speed sensor is required only for the speedometer on the display.....

If the your purpose of the question is regarding de-restricting the motor then you will be disappointed but if you are just worried about a sensor malfunction then no problem it will still drive the motor.

How does it know the speed of the bike then - Does it simply limit it's rpm based on the assumption that the hardest gearing will be 46:11? If that was the case, apart from re-restricting the motor, could you increase the bike's speed by fitting a larger chain ring?

 

[Geebee]

From reports on here and endless sphere, if you input a smaller wheel size the speed till cut of will increase but it will obviously show the wrong speed as well.

 

[shemozzle999]

It monitors the crank speed with an internal sensor.

For the 36v motor:

Maximum torque occurs @ 53.5rpm

Maximum efficiency occurs @ 77.8rpm

http://www.pedelecs.co.uk/forum/electric-bicycles/14590-8fun-crank-drive-kit-13.html#post182146

Knowing your wheel circumference and gear ratios you can calculate the optimum bike speeds that will be obtained in each gear to either get the best hill climbing (torque) or best battery life (efficiency) from your motor by using the appropriate rpm figures from above.

If you feel the speeds are too low or high for your particular riding style then yes you will need to change the crank wheel but unfortunately it is bespoke to the motor and alternative sizes are not due for release from Bafang yet, although others are being made - see :

http://www.pedelecs.co.uk/forum/electric-bicycles/14590-8fun-crank-drive-kit-22.html#post197700

I am sure ways will be found to tinker with the motor but the graphs above would change.

As far as I know no bike manufacturer bothers to include this useful information in their users guides.

 

[CoachMark]

Thanks to both shemozzle999 and GeeBee for the last two posts.

I normally aim for a 80 rpm cadence so that should suit the motor perfectly for the flatter bits. I hope that most of the time I'll be able to pedal without assist; just need it for the times when I'm struggling to keep up with my 12 yr old son (especially if I can get it to help up to 20mph) and up the hills of course.

 

[shemozzle999]

Hi CoachMark,

I hope it helps you understand how the motor can perform and how by changing gear at the right times you can maximize motor performance.

No doubt in the future the displays will be programmed to show torque, efficiency and power level bar graphs plus gear change up/down prompt arrows.

 

[CoachMark]

Hi CoachMark,

I hope it helps you understand how the motor can perform and how by changing gear at the right times you can maximize motor performance.

It does in terms of changing gear, but I'm still unclear as to how exactly it knows when the stop providing power, i.e. when the bike reaches 15mph.

 

[trex]

you set the maximum assist speed on the LCD - the default setting is 25kph. Hold the + and - button down for a few seconds, the 25kph will flash. Press + or - to adjust if you want to. Press on/off to confirm. The wheel diameter can now be set.
The default setting is 26". Press on/off to move to next if you don't need to change
Hold the on/off (middle) button down for two seconds, you exit the setting menu.
The magnet is tied to a spoke, the speed sensor counts the wheel RPM, multiplied by the wheel diameter, the LCD knows your speed and cuts power when you reach the set maximum speed.
200 rpm on a 26" wheel corresponds roughly to 25kph.
If you turn away your magnet, the speedo does not work, your bike will continue to receive assistance whenever you pedal or use the throttle, you have in effect derestricted your bike.
The maximum speed on a BBS01 is about 22mph on 26" wheels. You get a little more with 700C wheels.

 

[mat27777777]

Hi, i'm from Australia and have just completed an 8 Fun Crank kit installation. It is a 350W 48V kit.

This kit is simply awesome! Installation was a absolute breeze. The hardest part was finding tools to take the existing crank off and a tool to tighten the nuts on the new crank.

I've paired it with a 48V 10ah Lifepo4 battery pack and this thing goes amazingly well! The motor is so smooth and quiet and changing gears as you go along is no drama at all.

Pedal assist works flawlessly and there is great difference in assistance between 1, 2 & 3 levels.

Speed is set by hold the Mode + Light button down for 3 seconds, then when it goes to the settings screen, press Mode button once for wheel size, then 2 times for speed limit. Press the Light button adjust speed. Mine ranges from 20 - 35kph. Press the Mode button again and it goes to the Backlight setting for the screen. Make sure to exit the settings you again Hold down Mode + Light button until it returns to normal screen or the settings won't save.

I've found that the speed limit seems to only apply to the pedal assist mode. With the settings on 30kph, pedal assist cuts out on 30. But with the throttle it will go as fast as the gearing on your bike allows. This varies by what Pedal assist level you have set. I was doing 45kph in the 3rd level and still climbing.

Did I mention I weigh 100kgs and this will push me unassisted up reasonably steep hills at a steady 20kph.

I'm not sure how much difference the 250W/36V model would make, but i'm sure its likely to operate the same with the settings and I can imagine the power would still be satisfying.

I'm happy to post pics of my install if anyone is keen to see them.

Mat.