Fat bike mid drive with rohloff

benkels · Sep 25, 2016

So I thought I should share my latest bike build, especially as I've been a long time stalker of various threads without actually contributing very much, apologies and thank yous all round.
I actually pretty well finished it last year a part from a bit of fine tuning of the gear ratios. I took a fair few photos along the way thinking that I may at some point actually get my s*it together and post something. I used the belt sprocket from lightning rods and also the jack shaft and go cart sprocket, oh and the motor with the converted shaft and belt output sprocket, can't remember the motor output to large belt sproket reduction. On the other side of the jack shaft though I think it's a 12 tooth down to a 68 tooth on the go cart chain (518 pitch maybe?) Then the bike side is a 48 T out to a 13t on the rohloff in the back wheel. It's using 3x Turnigy flight max 22 volt packs in series, so 3s 1p. Although the cell on one of them just puffed up and so I think I'm going to get 100 x 18650 cells and go 20s 5p. Would love any advice on which cells are the best to go for. It's a Lyen controller and CA (version 3 i think). Just been uploading pics, think I may have hit the limit that I can load. It show's the fettling required to the swing arm to get the 24 x 4 inch tyres to fit. Can't really think what else to add a part from it being a real blast to ride tops out around 40mph and pedals very comfortably pretty well right through the gear range, I can't recommend the rohloffs highly enough. Well that's it, any comments or questions welcome

Justtoby · Sep 26, 2016

Wow, some proper skills there, please keep this updated

macribs · Sep 28, 2016

Really nice work. I liked how you made the swing arm fit the fat bike tire.
That bike looks really stealthy.

The first pic you got a Monitou Dorado fork. Did you machine a new tri clamp for the fork? The front tire seems fatter then what would fit a stock Dorado.

For cells choose look into quality cells, like samsung Q30, sony VTC 4/5/6, Sanyo NCR 18650GA those are 3500 mAh, panasonic's, LG H2, these are top notch cells all of them. Each manufacturer got more then one set of great batteries. Generally you would look for cells that has high discharge rate and high capacity. For instance Sony got a VTC 5a battery @35A - 2600 mAh, they also got the VTC6 @30A 3120 mAh and the VTC5 (no letter a) @30A - 2600 mAh.

Reason I mentioned 3 different cells from just Sony was just to show how some of the manufacturers have various series of cells, regarding discharge and mAh. Even some are fairly close price might vary largely. @nkon.nl prices for those three cells are from 5,25€, 6,45 € and 3.75€. All three are great cells but what are you willing to pay? And what is most important to you? High discharge rate or high capacity? Are you going for max distance and range when e-biking or is performance more important? These are some things to consider when choosing cells.

Then when it comes to picking sometimes it also comes down to what is available at time of purchase. Sometimes a given cell can be hard to track down, or maybe manufacturer has made some changes to the cells and they have not re stocked their warehouses or whatever.

spinningmagnets · Sep 28, 2016

What a fantastic build! Very professional looking.

benkels · Nov 6, 2016

macribs said:
Really nice work. I liked how you made the swing arm fit the fat bike tire.
That bike looks really stealthy.

The first pic you got a Monitou Dorado fork. Did you machine a new tri clamp for the fork? The front tire seems fatter then what would fit a stock Dorado.

For cells choose look into quality cells, like samsung Q30, sony VTC 4/5/6, Sanyo NCR 18650GA those are 3500 mAh, panasonic's, LG H2, these are top notch cells all of them. Each manufacturer got more then one set of great batteries. Generally you would look for cells that has high discharge rate and high capacity. For instance Sony got a VTC 5a battery @35A - 2600 mAh, they also got the VTC6 @30A 3120 mAh and the VTC5 (no letter a) @30A - 2600 mAh.

Reason I mentioned 3 different cells from just Sony was just to show how some of the manufacturers have various series of cells, regarding discharge and mAh. Even some are fairly close price might vary largely. @nkon.nl prices for those three cells are from 5,25€, 6,45 € and 3.75€. All three are great cells but what are you willing to pay? And what is most important to you? High discharge rate or high capacity? Are you going for max distance and range when e-biking or is performance more important? These are some things to consider when choosing cells.

Then when it comes to picking sometimes it also comes down to what is available at time of purchase. Sometimes a given cell can be hard to track down, or maybe manufacturer has made some changes to the cells and they have not re stocked their warehouses or whatever.

Thanks for the advice on the battery front. I'm sort of nervous about making up a 18650 pack myself. I had a play around with repairing a Makita drill battery and it all got a bit smokey, and that was just 10 cells this pack would be around 100. I really like the look of Grin Techs LIGO packs but not sure about their dimmensions or of their availability. I think I only need about a 40 amp output so I guess a higher mAh is preferable. I was hoping I might find a custom battery builder on this forum here in Europe but so far no luck.

Regarding the forks, I started out with some Marzzochi Shiver that I'd picked up on Pink Bike but they turned out to be leaking badly and were deemed unrepairable. I then found the Manitou Dorados. They're narrower between the stantions than the Shiver's, 100mm I think, so yeah it's very tight, around 3-4mm either side but thankfully I didn't have to get into custom fork yolks.....I think that would have pushed me over the edge and the bike would have spent the rest of it's days sitting in the corner gathering dust as an unfinished project. There must be a lot of them out there!

Anyway, thanks again for your interest.

waynebergman · Nov 6, 2016

Wow Benkels! Super nice. Keep us posted on the bikes performance and how it holds up. It sure looks pro. Good going on getting those 4" tires to fit in there.........wayne

Brake · Nov 8, 2016

Nice job! Looks like a blast to ride.

spinningmagnets · Nov 13, 2016

The article is done, Ben...just need a "pretty" picture for the top of the page.

PS, anything you have will work, and if you get a better pic later, I can swap it in at any time...

Mündawg · Nov 18, 2016

so sexy

Fat bike mid drive with rohloff

benkels

100 mW

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