My FS E-Fatbike (updated 8-29-11 now with video)

[dennyt]

I love this bike! What an amazing first build.

I love the sculptural quality of your frame, especially the swingarm. What diameter and wall thickness is the tube you used for the rear suspension pushrods?

Everything on the rear end is 1/2 inch .049wall. I think it's fine for the suspension pushrods, but I'm wondering if 3/4 inch would be better for the rest. It seems a little flexy, but I haven't got to ride it enough to know.

The swingarm stiffness caught my eye as a potential weak spot, especially with the added weight of batteries. And not just in the vertical plane - the swingarm sees a lot of sideways torque from the tire contact patch, which is on a 13" lever arm. So it needs to be vertically and torsionally stiff. Parallel small tubes are not up to the task. A larger single tube (like your fork blades) or a rectangular tube or small tubes with triangulation would stiffen it up. One of Carroll Smith's books, Tune to Win or Engineer to Win, discusses torsional stiffness. Torsional stiffness vs. weight goes something like:
Circular Tube 100%
Rectangular Tube: ~90%
Angle, flat bar, solid sections: ~10%
Circular Tube with Slit Cut Along Length: 10% (closed sections are 10X as stiff as open sections!)

An extra size up in tubing on the shock struts would improve the margin on buckling here, too. But if it isn't broke...

Looking forward to seeing more pics as you finish it over the winter!

 

[dhmillertime]

great build. I also bought the 1500w motor from superkids. No documentation and that tim guy won't answer my calls either. My motor came with the little black and purple wires clipped almost to the base of the motor. Are those important? Also I bought an infineon 48v 40a controller and am not having any luck getting the right combination of wire connections. If I at least knew which of the hall sensor motors are + and - than that would reduce my possibilites to 36. the hall sensor wires from the motor are brown, green, black, white, and red. The phase wires are black,white, red. I am guessing the brown and green are my + and - but no combinations have worked under that assumption. neither has black to black/ red to red. It sounds like your rolling pretting good so I hope you can help me.

 

[John in CR]

Can you open the motor fairly easily? That may be easiest to figure out your +5v and gnd for the halls, after which it is a piece of cake as long as the controller auto senses 120/90° operation, and the motor is neutrally timed. If it's not neutrally timed, then the motor will be directional, because if advanced, then you flip it around to run essentially in reverse that is now retarded timing.

If you get the motor opened, then you can see the +5 and gnd, because they will go to all 3 hall sensors.

Once you know which are the hall sense wires, forget that 36 combo stuff. EVERY phase combination has 1 valid hall combo of 6, and EVERY hall combination has 1 valid phase combo of 6. ie Change only halls or phases, not both until you find the 1 of 6 that is good. There are 6 valid wiring combos, 3 forward and 3 reverse. If you get a good reverse, simply swap 2, any 2, and only 2 phase wires (or hall wires), and find the right combination of the remaining 5 hall combinations (phase combos if you swapped 2 halls). The stuff spins in a circle and if the correct firing order is A-B-C, since it repeats the motor doesn't care if it's starting with A B or C, which means ABCABCABC is the same as BCABCABC and CABCABCABC for forward. That means C-B-A is reverse so CBACABCBA BACBACBA and ACBACBA are all the same. You just find the right 1 of 6 hall combos to match each.

 

[waynebergman]

Nice video Riverbend. Its is so nice to have a video that does not have background music in it. I like to hear the bike and I want to thank you for that. I don't know why some folks think its important to entertain its viewers with music and there attempts at special effects that more often than not are poorly done and detract from the truth of how there bike or project works. I love the idea of seeing the bike and hearing its story. I want to see it move and hear it move as well. Its is also very nice to have a walk around the bike with your narrative telling us a bit about the bike. Anyways, enough of my ranting............nice bike and thanks for the video!

 

[Riverbend Bicycles]

This project is finally finished so I thought I would show where it ended up. I did ride it quite a bit last fall and it seems to perform quite well. The only thing I might add is some sort of temperature monitor for the motor. If someone has a good solution for that or knows of a topic that deals with temperature monitors, let me know. Here are some pictures and a short video. I hope you like it.

[youtube]http://www.youtube.com/watch?v=AG9qX6U-G-Y[/youtube]

[youtube]AG9qX6U-G-Y[/youtube]

p.s. I can never remember how to embed the youtube videos into my reply on this forum. If someone can help with that I would appreciate it.

 

[TopCat]

The build turned out very nice, thats a smart looking bike :wink:

To put up a youtube link all you need is the letters and numbers after the = sign at the end of the link.

Regards
Tom

[youtube]AG9qX6U-G-Y[/youtube]

 

[The Stig]

I'm a big fan of your eFatbike!

I want to build my own but don't have the welding capabilities...

How is that geared hub working out for you?

Is the crank system pretty much custom fabricated or are there some off the shelf parts?

 

[Riverbend Bicycles]

I'm a big fan of your eFatbike!

I want to build my own but don't have the welding capabilities...

How is that geared hub working out for you?

Is the crank system pretty much custom fabricated or are there some off the shelf parts?

The hub is working great, thought I've only put 100 miles on it. The freewheel crank is from spooky tooth cycles, as are the gears on the jackshaft. I can't remember where I bought the gear on the motor. This build took so long that I've forgotten a lot of it. If you're interested in electric fatbikes you might enjoy my new build. I haven't posted it on this forum, but here are some links that deal with it.
http://forums.mtbr.com/fat-bikes/another-full-suspension-build-2nd-times-charm-hopefully-828973.html

and here's a short video
http://www.youtube.com/watch?v=Yebl93HbLvg

Thanks for the interest

 

[The Stig]

That new bike is Awesome, when will you start selling those frames!

Hows the low speed torque and efficiency of the hub motor in that big wheel? I generally try to put the hubs in small diameter wheels/tires for those reasons...

 

[Riverbend Bicycles]

That new bike is Awesome, when will you start selling those frames!

Hows the low speed torque and efficiency of the hub motor in that big wheel? I generally try to put the hubs in small diameter wheels/tires for those reasons...

I have no plans to sell frames. It's just a hobby for now. The torque of the hub motor is nothing like the previous build, but the technology makes for such a smooth overall experience. I've really enjoyed feeling like a superman as I pedal along. My intentions for this bike were to get myself in shape. This first fatbike (the one is this thread) is so much fun to ride and I've enjoyed it, but I need some exercise.