Eric's Project #002

[deecanio]

Hi Beagle,

cant help with the electronics im afraid but just wanted to say nice work!!!
bike is looking cool and im loving the new front end, good forks make the ride sooooo much better.
Im surprised your not more impressed with the avid's - i know my hayes 200mm hydraulics leave my cable 160mm brakes for dead when it comes to stopping power to the point that i have to feather the front as not to lock it up?


cheers


D

 

[MitchJi]

Thanks you guys. To answer your questions:

The Nuvinci hub really works well. The best thing about is that it is really strong. I have a 1200W motor directly pulling on a big 80 tooth sprocket (lots of torque) and it doesn't flinch. It seems much stronger than my gear hub (Shimano Nexus). I don't know the efficiency I'm getting but it seems fine.

Actually, I was thinking that electric motors don't need much gearing. I tend to put the shifter in the middle and just drive. If I'm in stop-and-go, I'll leave it in a slightly lower gear. However, I've come to the conclusion that the best solution for an ebike is having a 2 speed transmission. I have two different gear hubs and all that gearing is totally unnecessary. On my shimano, I switch between 2nd and 4th gear. I don't bother with any others. Optimally, I'd have one gear that maxes out at 20mph and another that maxes at about 32mph. That would be perfect.

Hi Eric,

Nice job!

Would either or both of these work better?:
http://www.greenspeed.com.au/dualdrive.html

The SRAM Dual Drive (DD) is the evolution of the previous Sachs 3x7. Both hubs feature an internally geared hub with a Shimano compatible cassette driver to accept regular Shimano cassette sprockets. The internal hub offers a 36 percent increase in gearing in overdrive and a reduction by the same amount in low. This enables you to achieve higher and lower gears than a plain rear hub with multiple chainrings.

http://www.greenspeed.com.au/schlumpf.html

Made in Switzerland to watch like precision, is the Schlumpf Innovations range of geared bottom brackets. Instead of running multiple chainrings up front with much overlap in gears, a planetary gear system is employed to provide a unique gearing between the the crank arms and the chainring. This means with the Mountain Drive your chainring spins at 1:1 in direct drive and your cranks rotate 2.5 times for every single revolution in low range. Using a 60 tooth up front in direct, drops down to the equivalent of a 24 tooth in low!
Mountain Drive; high 1:1, low 2.5:1
Speed Drive; high 1:1.65, low 1:1
High Speed Drive; high 1:2.5, low 1:1

 

[Miles]

An interesting bit of news is that Schlumpf are changing to a new symmetrical clutch system for their drives. This is primarily to satisfy the needs of fixed gear users but it will also make them more useful for us.....

 

[Beagle123]

Rebuilding my Back Swing Arm

After riding my scooter, I found that I usually just drove in the middle gear. The fastest gear was basicly useless because it doesn't have enough torque to go 40 mph, and the lowest gear was too slow. So switching to a single-speed system would make sense.

My scooter uses a NuVinci gear hub on the back wheel for its gears, and I think I'm losing effeciency because some of the motor's power is lost due to friction in the hub.

Also, I'm not convinced that the cheap Unite 1000w motor is very effecient either.

I've noticed that others like Doctorbass and xyster have great results using 5304, or 5303 hub motors. These make good sense to me because if I'm going to use a single-speed system, you can't do better than a hub motor. They have zero effeciency losses due to chains or gears--all the power goes directly to the wheel.

However, my current back end is made from aluminum, and I don't beleive that I can simply insert a hub motor. I think a better plan is to rebuild my back-end using steel so it will fit the hub motor perfectly. Also, its good to have a steel dropout and a strong torque-arm to secure the hub motor. These hub motors are strong and can bend steel dropouts.




If you look at my current swing arm below, you can see that it pivots on a 1/2 inch bolt:




I'd like to build a back end that looks like this:




I'd like to replace the back end with one that uses ball-bearing to pivot instead of just friction. I bought these ball bearings at mcmastercarr.com:



The fit the bolt perfectly:



Then I bought a steel tube from my metal shop:



Lucliky, the ball bearings fit perfectly inside the tube. They have a flange so they don't slide into the tube.

 

[Beagle123]

I bought some 2X1 steel tubing for the arms that extend back to the wheel, and some 1/8th inch X 2in steel bar to make the dropouts. I don't know if 1/8th inch is thick enough. I'm using ideas from dirty_d's build for the swing arm:

 

[docnjoj]

Thats some real purty welding! Are U doing your own, Beagle???
otherDoc
Duh! Just saw the faceshield and table

 

[Beagle123]

That's dirty_d's work. It does look great.

 

[D-Man]

Wouldn't you think the efficiency would come out the same? Since the hub motor has no gears, you would think it would suck more amps to get going. So by the time you get up to speed, any gain of eff. at cruising speed would be lost due to no gears or pedal power on take off.

 

[Miles]

For this case, without knowing what the efficiency of the NuVinci hub is, it's difficult to judge...

 

[Beagle123]

The hub motors have good efficiency numbers in the lower RPM zones. Also there are no losses due to the gearing on the motor, or the gearing on the chain, the chain itself, and the gearing in the hub. I think it will work well. In fact I usually just ride the bike in one gear now. The motor operates well at 1/2 speed with the motor at the maximum torque.