Downhill 2WD Conversion Project

[campbell1987]

Ok so I'm starting to look at deigning my new e bike and have a few questions first,

This is the bike i am looking at, (Not the actual bike, the one I'm looking at has lots of extras but same colour frame)

http://ep1.pinkbike.org/p4pb6633870/p4pb6633870.jpg

Haven't bought anything yet so if anyone has any other suggestions please post and let me know, I'm in county down but I'm willing to go anywhere in Ireland north or south for a good bike, Was also looking at the nukeproof scalp but they're just a few hundred outside my budget, Most i wanna spend on a bike is arround 800,

I was thinking would it be possible to have RWD / 2WD selectable for when its on flat ground to save battery use and also when its in RWD on flat grounds have the front wheel acting as a dynamo charging the battery or is this not possible?

I was looking at this battery

https://bmsbattery.com/ebike-battery/715-high-power-48v30ah-lipo-battery-pack-battery.html

Is this any good? or am i safer buying hobbyking lipos or even headway lifepo4 cells?

Last question, Is there any benefit to spending the extra 250 quid for the sine wave motors from bmsbattery.com or should i just get the 48v 1000w q11 front and rear?

Sorry for all the questions

 

[Deleted member 4366]

There's lots of problems that you'll have to overcome to implement your plan.

Where will you install a big block battery like the one you suggested?
I can't see if you have through axles. If you do, you can't fit a hub-motor.
If you have conventional axles, you shouldn't fit a motor of more than 350w in the front. I've just taken an over-volted 350w motor out of a pair of forks. I've installed loads of front motors and on this one I used properly anchored double torque arms on it, and the drop-outs themselves looked pretty strong. When I removed the motor, both drop-outs were broken. Only the compression of the washer was holding the broken bits in place. You need steel forks for a powerful front motor.
1000w direct drive motors will spoil your nice suspension. It won't work properly because of the weight in the wheels. The lighter the wheels, the better. You need a high ratio of sprung (you and the frame) to unsprung (wheels) weight for good suspension.

You can use a front motor as a dynamo to charge the battery, but why would you want to use 500w extra in the rear motor to drive the dynamo to produce 250w back in the battery? Try pedalling a 250w dynamo on its own. You can do it for about one minute before you're knackered.

IMHO, if you want a downhill bike, it has to have a mid-drive for your suspension to work. GNG do a nice powerful one if you don't mind the noise of the extra chains.

 

[Martin@e-bikeshop]

Dave's the man for conversions. I was impressed by his 2 wheel drive when I rode it a while back. Strange feeling.. Or you could just bite the bullet


Good luck with the conversion!

 

[campbell1987]

Sorry only getting back to you now, Was away there for a few days and had no laptop with me, Thanks for all that advice Dave, i'll not bother with the hub motors then or that big battery, I bought the kona stab deluxe, Here is a few pics of it to give you some idea what I'm working with,

https://lh3.googleusercontent.com/-c8OdcZAn7TI/VN_gVoHjkjI/AAAAAAAADzE/0a9y97wvYS8/w983-h553-no/20150214_223856.jpg


https://lh3.googleusercontent.com/-2fByOU8epmQ/VN_gZtw08II/AAAAAAAADzQ/1oM8i1rDqXQ/w311-h553-no/20150214_223910.jpg


https://lh6.googleusercontent.com/-Netqh5x8UtA/VN_gd35CQnI/AAAAAAAADzc/l9So1anXNpU/w311-h553-no/20150214_223923.jpg


https://lh5.googleusercontent.com/-3esP0tTs_Uc/VN_gh1s-MQI/AAAAAAAADzo/dC3ktm7fltI/w983-h553-no/20150214_223938.jpg


https://lh5.googleusercontent.com/-yo7e-mnOCAQ/VN_gltytkrI/AAAAAAAADz0/X0YZhqzYBA4/w983-h553-no/20150214_223952.jpg


https://lh5.googleusercontent.com/--vnEPe5ApjE/VN_gnyXu6XI/AAAAAAAAD0A/Qhn7V9EhLmQ/w983-h553-no/20150214_233809.jpg



I was looking on bmsbattery and seen this central motor

https://bmsbattery.com/ebike-kit/646-48v-750w-bbs02-bafang-central-motor-ebike-kit.html#/lcd-c963

Would this fit my bike ok?? And if so would i need to add a stronger chain to transfer power to rear wheel? Also I have hydraulic brakes on the bike and the ones included with the motor kit are for cable brakes. Is it possible to get hydraulic brake levers with switches for cutting out motor,

Lastly what battery would you suggest using?

 

[campbell1987]

Thanks Martin but that's 4 times more than my budget.. ;-)
Am i not getting a faster bike for less with the bafang motor?? bosch 36v 250w vs bafang 48v 750w.... I know which one sounds better.. Nice lookin bike though ;-)

 

[Deleted member 4366]

Without having all the stuff in front of you, it's not possible to give a definitive answer to whether it will fit. It looks like there's a fair chance that it will. It depends on the shape of your frame at the BB. You need to study the various videos that show how it fits. If you have a BB longer than 68mm, it becomes more complicated. You can't use the kit's brake switches. Instead you have to make your own. There's no real answer to the chain. You'll need a good quality one whatever size you use.

 

[Kinninvie]

EM3EV sell Bafang hydraulic brake cutouts designed for the BBS02 http://em3ev.com/store/index.php?route=product/product&product_id=196

I think you will find your bike is fitted with the Kona Saint BB and may be 83mm in which case the BBS will definitely NOT fit!!

 

[campbell1987]

Looks like a 68mm to me....??

https://lh3.googleusercontent.com/-p4NGS8leQYM/VOHBkhyB4NI/AAAAAAAAD0k/ED8F02OIt2w/w287-h510-no/20150216_100808.jpg

 

[campbell1987]

I think 2006 was the year kona switched bb size....

 

[Kinninvie]

Ah,so its an old model then?
I would just get it measured before ordering anything.
There is also a Uk solution for hydraulic brakes http://www.eclipsebikes.com/bafang-bbs01-bbs02-hydraulic-brake-sensors-p-1109.html

 

[Kinninvie]

Just checked that last photo and you may have a problem with clearance between the downtube and motor.
You may have to angle it down quite a bit,compromising ground clearance.
You would also have to get rid of that lump of aluminium behind the chainring.
http://www.alcedoitalia.it/wp-content/uploads/2013/09/bafang-centrale-bbs01.png

 

[Deleted member 4366]

People have fitted the BBS02 to bikes with a 73mm BB. Why do you say it can't be done?

 

[campbell1987]

think those brake sensors are only for 36v bbs01 motors, I was wanting to fit the 48v 750w one, I have a mate who's pretty good at welding as he does alloy wheel repairs so if the part of frame does reduce ground clearance then would grinding the part off and rewelding a flat piece on be an option?

 

[Kinninvie]

People have fitted the BBS02 to bikes with a 73mm BB. Why do you say it can't be done?

Who said it cant be done?
Mine is on a 73mm BB.
It certainly cant be fitted to the new Kona Stab as it has an 83mm BB.

 

[Kinninvie]

think those brake sensors are only for 36v bbs01 motors, I was wanting to fit the 48v 750w one, I have a mate who's pretty good at welding as he does alloy wheel repairs so if the part of frame does reduce ground clearance then would grinding the part off and rewelding a flat piece on be an option?

The brake sensors fit all BBs motors with the latest style plugs,you can also fit them to earlier models but would need to change the plug to suit.
EDIT sensors are only 36 volt. My mistake!!

Altering the frame by welding is a possibility as long as its done without compromising strength.

 

[campbell1987]

Ok so sounds like its all possible then. Just to be clear before i buy all the parts, The link you sent says

"Please note that the brake sensors will currently only work with 36V Bafang BBS01 / BBS02 motor kits. NOT suitable for use with 48V Bafang BBS02 500/750 watt mid drive kits."

So its just a case of splicing wires to make it work,??

Also can you suggest the strongest chain i should buy, And anything else i might need, ;-)

 

[Kinninvie]

OOPs,I didnt see that,It looks like they must use a 36V maximum switch then.
I just use a Wuxing horn switch to disconnect the motor .
http://www.ebay.co.uk/itm/321468618988?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

Best chain for use with 6 to 8 gear rear is a Wipperman 7E8 http://www.ebay.co.uk/itm/300960739859?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT which is designed for e-bikes

 

[danielrlee]

I thought brake cutouts tended to work from a 5v feed on your average brushless controller. Why are BBS controllers any different?

 

[Kinninvie]

I thought brake cutouts tended to work from a 5v feed on your average brushless controller. Why are BBS controllers any different?

Good point and I think you are correct from what I have read elsewhere.
Will have to investigate further.

 

[campbell1987]

What about these?? Would they work with my current calipers or would the lot need replaced?

http://www.tektro.com/_english/01_products/01_prodetail.php?pid=155&sortname=Disc&sort=1&fid=1