Koga F3 3.0 eccentric bottom bracket

[Battbuild]

I have a 2019 Koga F3 3.0. I am thinking about making this bike electric using a mid-drive. It uses an eccentric bottom bracket to tension the chain that is connected to a nexus 8 IGH.

In this youtube video you can see what type of bracket I'm talking about. It says it uses a shimano Sealed cartridge JIS as a bottom bracket inside the eccentric bracket?

Would it be possible to fit for exemple a bbs02 in this eccentric bracket and how would I go about doing that?

 

[BicycleJoe]

Provided that the width of the (eccentric) bottom bracket shell is 68-73mm, a BBS02 should fit right in there.

Before you order one go to:

https://cdn.shopify.com/s/files/1/0537/7176/3911/files/Bafang_BBS02_750w_Template_Printout_Ebike_Essentials.pdf?v=1619116147

Print this template at full size, cut out the form and insert into your empty BB-shell...

 

[PaPaSteve]

Chances are low it would work.
Look how close the motor housing is to the frame.
Picture comes from this thread :

San Francisco Cargo bike

In your situation with the rear brakes a mid drive might be the easiest way out. If it can fit with the interference from the bottom bracket that I read about ? the mid drive (bafang bbs02) will fit if you cut away some of the metal near the pedals. a number of people in a facebook group...

endless-sphere.com

 

[dgc]

If you look for a "eccentric bottom bracket insert" to suit your frame you will should find one that will accept a mid drive, but be careful as I fitted one to NOS UK Carrera Subway 8 frame which was fine but it was an insert as ebb.jpg what you will need is something like in ebb1.jpg I assume. But my problem was two fold in that with the TSDZ2 mid drive there was not enough clearance between the motor casing and the chain-wheel axle housing of the drive to allow the bottom bracket to pass thro' and secondly the bottom bracket housing on this frame is a split type which clamps over the "eccentric bottom bracket insert" using a pair of clamping flanges low on the front. So ended up fitting Bafang rear hub motor as per image where you can just make out the shiny heads of the cap head screws.

 

[dgc]

Forgot to say if you have a friend with a 3D printer you may be able to get an adapter sleeve printed. One guy did that on YouTube and I have printed quite a few bits for my bikes including battery and controller housings etc.

 

[dgc]

Just looked at your video again, they looked like screw in external bearings on the BB which you should be able to unscrew, remove and fit the mid-drive straight in as I can see the direct arrow and the tightening torque figures.

 

[Battbuild]

Thanks everyone for the replies. I have been doing some more research and think I will be going with a hub motor in the back. My nexus hub has recently started to make weird noises, and I think it needs servicing, however it might be a better idea if I go for a single speed with a hub motor. This will make sure I don't break the Nexus 8 speed, because I know someone who broke his in a week after putting on a mid drive. It'll also give me regenerative braking, so my rim brakes will be enough to stop me.

 

[2old]

You might consider a cassette hub in order to space the gear for a straight chainline, since this could be challenging with a SS gear on a freewheel hub.

 

[Battbuild]

That's actually a really good idea, but isn't it possible to place the single speed gear where ever I want? Or does it need to be a snug fit with the hub?

 

[Chalo]

That's actually a really good idea, but isn't it possible to place the single speed gear where ever I want? Or does it need to be a snug fit with the hub?

A threaded hub with a single freewheel has limited options for changing chainline. You can move the freewheel outwards by up to about 2mm by placing a spacer behind the freewheel. Or you can trade axle spacing from one side to the other to get more change than that, but you'll have to re-dish the wheel to bring the rim back to center.

You could use a 3 speed freewheel that's pretty much like a single freewheel with a sprocket added to each outer edge, but commit to only whichever sprocket has the best chainline. Or you could use one of the 14 tooth or 12 tooth single freewheels that hangs the sprocket off to the right of the freewheel thread.

It's probably easier to use a cassette hub with a single sprocket and spacers that allow you to locate the sprocket anywhere along the freehub splines, but this has the disadvantage of using a highly dished, weaker wheel to do the job of a more symmetrical, stronger wheel.

All of this begs the question, why would you use a mid drive with only one gear ratio? If you do that, you would have all the disadvantages of mid drive without the only thing that might make those disadvantages worthwhile.

 

[Battbuild]

All of this begs the question, why would you use a mid drive with only one gear ratio? If you do that, you would have all the disadvantages of mid drive without the only thing that might make those disadvantages worthwhile.

i'm doing a hub motor in the back, and by your recommendations probably with a 3 speed freewheel in the back.

or would it be possible to use the single sporcket with spacers on both sides to get a nice chainline?

In addition, I wil be using the makerbase VESC 75100, but I need a way to make it sort of waterproof so I can use it in the rain. How would I go about doing that?

 

[lnanek]

FWIW, I never found chain line super important on my 1 x Nexus IGH bike. You can use a 7 speed chain instead of a single speed so the chain can bend more, use a chain that comes with a half link on the end so you can size it tighter than a chain with all full links, add a chain tensioner - to the chain stay if no derailleur hanger, use a narrow-wide tooth profile front cog (if not using half links), etc.. You are getting rid of the Nexus, but it also has a dished cog you can flip to move the chain line around as well.

Chain line is important for multi-speed bikes because they shift to different size cogs and can't keep their chain super tight on all of them and they use ramped tooth profiles intended to let the chain fall off on to nearby cogs. For single speed bikes you can just get the chain super tight without those concerns, so extra side to side deflection not super harmful. You no longer care about shifting, just keeping the chain from falling off.

 

[Chalo]

FWIW, I never found chain line super important on my 1 x Nexus IGH bike. You can use a 7 speed chain instead of a single speed so the chain can bend more, use a chain that comes with a half link on the end so you can size it tighter than a chain with all full links, add a chain tensioner - to the seat stay if no derailleur hanger, use a narrow-wide tooth profile front cog (if not using half links), etc.. You are getting rid of the Nexus, but it also has a dished cog you can flip to move the chain line around as well.

With a single speed chain tensioner or or a derailleur used in the same role, I tend to agree. But for a simple single speed chain run with two sprockets and some method of tightening the chain without a takeup device, bad chainline is noisy and destructive. "Close enough" is close enough, but derailleur bikes are much more tolerant of bad chaining, by design.