Nexus 3 on a BIkes Direct singlespeed fat bike w/BBSHD

[WoodlandHills]

I installed the Nexus 3 that I had laced into the stock 80mm rim that came with my single speed Bikes Direct Deadeye Monster fat bike last night. It was a very easy and direct bolt-on with no need to alter the bike or the hub except where I had to use a file to remove a bit of plastic from the twist shifter. This was due to the Bafang brake levers being a bit thick/clunky: YMMV......

The IGH came with a 19t sprocket which results in a slightly lower first gear for hill climbing. The street I live on has a 32 degree slope and with the stock gearing of 46/22 (BBSHD/SS freewheel) I could climb it but had to stand on the pedals. Now with 46/19 (BBSHD/Nexus3) gearing and in the lowest Nexus gear I can make the climb while staying seated. I have a 23t Nexus sprocket in transit as well as a LunaCycle 42t chainwheel for the Bafang, so I hope to be able to set up 1st gear for singletrack, 2nd for fire roads and 3rd for pavement with the right combination.

The chaninline seems to be pretty good with all stock parts, but there is still room between the 4" rear tire and the chain for the Luna Cycle chainwheel to move the front sprocket inboard a bit. Only a good thrash will tell if it will jump off of the sprockets under a heavy load although a 32 degree hill is a decent load and it was fine!

 

[2old]

Not trying to be rude, but do you mean 32 degrees or 32%; there's a big difference?

 

[WoodlandHills]

I used the level app on my phone, they just paved the street so it's smooth and it shows 32 degrees. I always joke that it's a 45* angle, but obviously I am wrong......

 

[Alan B]

The steepest streets in USA are less than 35% which is about 19 degrees.

http://www.huffingtonpost.com/2014/02/28/steepest-streets-america_n_4871559.html

 

[Alan B]

And a 19 tooth rear sprocket produces less torque than a 22 tooth sprocket, for hill climbing you want 30+ teeth on the rear. (Large on rear, small on front for torque).

 

[Drunkskunk]

Switching from a 22 rear gear to a 19 tooth rear gear is 14% harder to pedal and get up a hill.
Its likely imposable for a human to pedal a fat bike up a 32% grade with a 44/22 gearing, and even worse with 44/19. My fat tires measure ~ 90 inches in circumference. So with a single revolution of the pedals at 44/19 gearing, you would move the bike 208.5 inches, or 17.37 feet forward.
A 32% grade has a rise over run of 1 in 3.125 Ratio calc
17.37 feet / 3.125 gives an elevation change of 5.56 feet. 2 pedal strokes per revolution (one per leg) means each time you push down on the pedal with a 44/19 gearing on a 32% hill you would have to go up 2.78 feet. the down stroke on a standard 175mm crank is 13.78 inches, 1.15 feet.

Nope.

 

[WoodlandHills]

Gosh, I dont know who to believe: you guys or my lying eyes.

All I know is that using the level app on my phone the hill I live on is between 30 and 34.5 DEGREES. I just checked it again by setting the phone down flat on the street and it is again between 30 and 35 degrees. Does anyone else here seriously consider the HuffPo an authoritative source on anything?

Using the Bafang 46t and the Bikes Direct 22t SS cog I could climb the hill by using full throttle and standing on the pedals with a running start.

Using the Bafang 46t and the Nexus 19t cog I could climb the hill by using full throttle and pedaling while seated in first gear (1.35% underdrive) with a running start.

Using the Bafang 46t and the Nexus 23t cog I could climb the hill by using 1/2 throttle and not pedaling at all while in first gear (1.35% underdrive) from a standing start.

Switching from a 22 rear gear to a 19 tooth rear gear is 14% harder to pedal and get up a hill.
Its likely imposable for a human to pedal a fat bike up a 32% grade with a 44/22 gearing, and even worse with 44/19. My fat tires measure ~ 90 inches in circumference. So with a single revolution of the pedals at 44/19 gearing, you would move the bike 208.5 inches, or 17.37 feet forward.
A 32% grade has a rise over run of 1 in 3.125 Ratio calc
17.37 feet / 3.125 gives an elevation change of 5.56 feet. 2 pedal strokes per revolution (one per leg) means each time you push down on the pedal with a 44/19 gearing on a 32% hill you would have to go up 2.78 feet. the down stroke on a standard 175mm crank is 13.78 inches, 1.15 feet.

Nope.

You ARE aware that the Nexus3 is an internally geared hub? That it has 3 speeds and that I used the lowest of the 3?

What happens if you run the numbers for the actual gearing that I use? The Nexus 3 has a direct 2nd gear for which your numbers would be almost correct (if I used a 22t instead of the 23t I actually did use). First gear is a 1.35% underdrive and third gear is a 1.35% overdrive.

BTW, I have never pedaled this or any other fat bike w/o a motor, nor do I ever intend to.

 

[Alan B]

If your phone is right, then your street will be the steepest street in the USA. I wonder if this is really the case. Is your street listed in the various articles on steep streets (Google for steepest streets)? Clearly you have a steep street to climb, but the 35 degree number is a bit questionable. For example laying the phone on the ground creates a baseline of less than a foot which produces a very low accuracy measurement. Better to use a baseline of many tens of feet, and an optical sighting. And check the accuracy of the phone app.

Your implication that changing from 22 to 19 teeth on the rear increased your torque was just misleading, since the IGH is additional gearing that you did not have with the 22 cog. Changing from 22 to 19 teeth on the rear cog reduces torque, the IGH gearing needs to compensate for that and more to get a net torque increase. You could calculate the effective cog teeth by combining the IGH ratio and the tooth count of your cog.

I agree with you that pedaling fatbikes without motors is quite difficult. I like the look of a fatbike but they're not very practical or efficient unless the extreme tire flotation is needed for sand or snow. They also get flat tires easily and frequently with all that thin rubber on the pavement. But they look cool and are fun in sand, loose dirt and snow.

I'd prefer to see all the info about your bike project in one thread, instead of fragmented all over the place. Then it makes a story that others can follow, and learn from.

 

[WoodlandHills]

I don't understand how I was misleading, the title of the post sort of indicates that I am referring to an IGH. If the assumption was made that I was trying to climb a very steep hill in any gear other than the lowest, then that is not very reasonable, is it?

I just re measured the angle of the street using my 48" level, with the tip of the level on the pavement and with the level dead level as per the bubble and the iPhone the distance to the street is 9". Can anyone do the math? With the level attached to the 48" base it still indicates damn near 36 degrees..... Curious isnt it?

 

[Alan B]

Your right, I just reread the first post, it was not as misleading as when I read it the first time, however the 32 degree slope claim is not credible. Not being familiar with the Nexus, it wasn't clear initially, and it appeared to be backwards in the torque sense.

Your threads would be much more interesting if you added some photos, and even better if you combined them into a story about your project. Fatbikes are a hot topic lately, and the BBSHD is a new drive so people like to see what the bits look like. So there is interest in this area. Most folks on here make threads about their builds and generate some continuity.

Also more comments about the Bikesdirect experience would be interesting, perhaps you made them in another thread. I have considered them for bikes but haven't tried them as of yet.

Good luck on your project.

 

[spinningmagnets]

If the level is 48-inches out, and the drop is 9-inches from the bottom of the level to the road...lets double the numbers...96 inches out and 18-inches down.

If it was 100 inches, it would be a direct conversion of inches of drop to % of grade, so...18% sounds realistic for an extremely steep road.

 

[Rassy]

The grade percentage is calculated by dividing the rise over run and by multiplying the result by 100

So if the slope you were checking had a 9" rise over a run of 48" the grade percentage would be (9/48) X 100, or a grade of 18.75%, which is a reasonable but steep grade.

 

[WoodlandHills]

Thanks for the help with the math. I don't doubt that you are correct about the angle of the hill. I am going to look into to this app and see how it is off 10 degrees or more. Anyway, it's quite a steep hill and IMHO a very good test of an eBike.

The Bikes Direct experience was a totally positive one from start to finish and my newest arrived this afternoon, a day early! I will take pictures of this build from start to finish, if I can follow the picture posting protocol here! I have a dormant photobucket account that I can use. If you want to get the recipe from the inventor, go to electric-fat bike.com and look for the cheapest fat bike! Honestly, I just used the links and tips there and everything has been a direct bolt-on.

Using a BBSHD and the stock Nexus 3 sprockets, the chain is misaligned by about 7/16"! Any chainwheel that corrected for that offset at the motor would contact the chainstay unless it had fewer teeth. Even if it did the misalignment is too large to be completely corrected at the chainwheel. But there is a lot of room to move the Nexus cog outboard, perhaps even 3/8", I have 4 23t sprockets coming to experiment with and I am sure I can sacrifice one cog to use as a hub and another as the sprocket with a spacer between. On the Deadeye Monster frame there is close to 1/2" between the Nexus cog and the dropout, so there is room to make a decent correction.