Bafang Mid-drive

http://i451.photobucket.com/albums/qq236/d8veh/Bafang%20Crank%20drive/SANY0133.jpg

http://i451.photobucket.com/albums/qq236/d8veh/Bafang%20Crank%20drive/SANY0137.jpg

Finished and tested at last. It gets me (100kg) up our 1 in 4 test hill without pedaling in 1st gear. It rides just like a normal bike except that when the pedaling gets a bit hard, you open the throttle a bit and it then it becomes a lot easier. It has a double free-wheel on the motor, so there's no noticeable drag when pedaling unassisted. The chain is tensioned by sliding the whole assembly up the down-tube. If it's not fairly tight it does the odd jump on the motor sprocket so I'll be fitting a tensioner next week to get more wrap-around the sprocket. I still haven't figured out how to get a pedal sensor, so works on throttle only. I bought the motor kit from EVassemble.com about 6 months ago when they were a bit cheaper. it was about £150 then. The bike was £15 from Facebook ads and I spent about £50 on bits and pieces and the Rockshocks Dart 3 forks were £70. Uses 36v Lipos £104 for 4 packs to give 10.4aH. So that's about £400 total. Now back to my prgramable controller interface - my only outstanding project.

That's great.

So when will you be making the mounting kits and motor freewheel conversion parts available

Cool bit of engineering I like it. Is the freewheel on the motor just a normal bike freewheel like would be used on a bmx?

I have imagined configurations like that a bit myself, one possible issue I thought might happen is the pedal on the lh side might unthread itself - though I sppose you can always just put some threadlock on it if it does this.

Did you have to modify the chainstay on the lh side to make clearance for the chainwheel? or is it a bb with an extended axle?

Thanks for sharing this, I have some radical projects myself in progress, in due time I will post them when I get more done :-)

Hi oigoi/d8aveh, Do you (or anyone else!) know what disc hubs can be taken apart so that I can use the disc brake housing plate? The closest I've come is this:

Problem Solvers Adapter - CTR Lock To Is at JensonUSA.com

Thanks ...

d8aveh - now that is impressive. I wondered what happened to the project! Well done:)

John

Hi oigoi/d8aveh, Do you (or anyone else!) know what disc hubs can be taken apart so that I can use the disc brake housing plate? ...

I'm not sure what you're trying to achieve, so it's difficult to advise. I used a pressed steel BMX non disc rear hub. If you look in the folder in my Photobucket, you can see how I did it. There's also some other photos there.

Bafang Crank drive pictures by d8veh - Photobucket

I had to turn back the bit behind the thread on a centre -lathe to get the sprocket closer to the motor. Everything else is made with hand tools and a mig-welder with bits I had lying around.

I won't be making any kits, unfortunately, because I don't have enough stuff and every bike frame is different.

After more testing I found that the chain jumps on the sprocket if you go uphill in a high gear at WOT, so It definitely needs a tensioner. I've got one now that should do the job. I think it's off a hib-gear bike.

Alan I don't know if this is of any help? it's a website selling sprockets that bolt on to brake disc mounting holes:

VeloSolo Shop - Disc Hub Mount Cogs and Accessories

Also something that may be of help to know is that a lh bottom bracket bearing cup has the same thread as the inside of a single speed freewheel, I have used this on one of my creations to mount a freewheel (a work in progress..... )

Alan I don't know if this is of any help? it's a website selling sprockets that bolt on to brake disc mounting holes:

VeloSolo Shop - Disc Hub Mount Cogs and Accessories

Also something that may be of help to know is that a lh bottom bracket bearing cup has the same thread as the inside of a single speed freewheel, I have used this on one of my creations to mount a freewheel (a work in progress..... )

Thanks. Yes. catsnapper put me onto velosolo when I was trying to id the spockets in one of the photos from the german forum. Later, I found the bolt on sprockets! I placed my order yesterday for sprockets and bolts (30 quid) ...felt good spending money on my project ... went to bed relaxed but am up again with head spinning with thoughts of using a pair of Disc Rotors for my adapter plate. One attached to the inside surface of the spoke hole "rim" and the other lined up about 20 mm down the axle. Just need to get some with enough holes or stays I can make holes in ... may not even have to use the spoke holes (if your following any of this! ..)

Nice job, Nice to see you've got it all up and working.

Its great you've even managed to test it and so far so good. Not real hitches at all.

Has it also made much difference to your top speed given that the motor can now drive through the gears?

Any who very neatly done and about as simple as a hub motor can be with it driving through the gears. Wonder it there will be any long issues with running a sprocket on the disk brake fitments.

regards

Scott

Brilliant tinkering as usual! I guess it's important to match the gearing on the motor side with efficiency while not labouring your legs or spinning them to quickly.

So all the advantages of crank drive while still keeping a low centre of gravity should make for a nice ride.

Really well done it's nice to see another one of your interesting and informative posts!

Just move it down a bit,wrap it round the crank,add some good sensors and software and you have the product that everbody is looking for,put patent applied for and then off to Asia to make your fortune...if only it was that easy!

Dave

KudosCycles

Just sorted the chain tensioner - now it's ok with no jumping on the sprocket.

http://i451.photobucket.com/albums/qq236/d8veh/Bafang%20Crank%20drive/photo2.jpg

You can see a Youtube video of it working here - if you're interested:

Very good, crude chain tension but very functional with the spring giving it an auto adjustment.

Like it!

A cover would also lower the maintenance on a chain system too.

Either way its great.

I applaude anyone who takes the time to put something like that together...

Now back to my prgramable controller interface - my only outstanding project.

But the controller really peaked my interest. Are you building a motor controller from scratch or adding to an existing programmable controller?

I've been playing with the arduino and was thinking it would make a good base for a DIY open source controller...

I'm making an microprocessor-based interface between the throttle/pedal sensor and the controller to give a more sensible and programmable power profile. I may even add a speed sensor.

I see a problem with existing controllers that want to give more power when you pedal harder or faster. To me, that's daft. It should be the other way round, so that you can choose how hard you want to pedal and choose how much power you get, with more power as you pedal less - if you want. You can more or less do this if you have a throttle, but it's almost impossible to hold the throttle constantly in the right position. On two of my bikes I use a potentiometer as a throttle and this is much better as it feeds in more power automatically as I slow down because it works as a speed controller - trying to maintain the speed. I want to trigger the potentiometer throttle only when I pedal for a more natural effect.

So far, I've managed to get an output in the right range (1 to 4v) that comes only when I pedal, which I can set with the pot. I want it to be overridden by the throttle.

The software that comes with this microprocessor is very simple to use but limited in what it can do, so I'm having to be creative when programming.

Does anybody know how much current the pedal sensor 5v line can supply because I want to use it to power my microprocessor?

I see a problem with existing controllers that want to give more power when you pedal harder or faster. To me, that's daft. It should be the other way round, so that you can choose how hard you want to pedal and choose how much power you get, with more power as you pedal less - if you want. You can more or less do this if you have a throttle, but it's almost impossible to hold the throttle constantly in the right position. On two of my bikes I use a potentiometer as a throttle and this is much better as it feeds in more power automatically as I slow down because it works as a speed controller - trying to maintain the speed. I want to trigger the potentiometer throttle only when I pedal for a more natural effect.

So far, I've managed to get an output in the right range (1 to 4v) that comes only when I pedal, which I can set with the pot. I want it to be overridden by the throttle.

I've been thinking the same thing, but I would also like a cruse control of sorts where I can set the required top speed for motor assist. Not to mention built in data logging.

As a matter of course I have always backed off the power when going up a hill so as not to over tax the battery and would be interested to see if it is possible to set a lower power mode for hill climbing that matches the speed I pedal at.