2018 Crust Evasion step-thru, BBS02, Shimano Nexus INTER-3 IGH

[ncmired]

Next up is a Crust Evasion step through frame. Budget demands that this build proceed at a snails pace, and through a few iterations.

Initial Specs: 68mm motor, 73mm bottom bracket

This bike will be primarily for guest riders and will be my third build, with the following ever-changing goals, desires, or components:

• The Shimano Nexus INTER-3 IGH, to simplify the chain line and bike ride
• Fattish tire clearance with a narrowish Q. 2-2.4" wide, 26 inch tires, such as the Schwabe Big Ben Plus on Halo SAS disc rims to reduce standover height
• TRP Spyre cable brake calipers
• BBS02 mid drive
• short reach bars / stems
• Adjustable, replaceable rear dropouts with an inboard (within the frame triangle) disk caliper mount
• 1/8 inch chain
• Capacity for a temporary chain tensioner
• Steel frame tubes

The frame has a relatively high top tube and big main triangle for a battery, and triple bottle mounts on the down tube:

[Jim Keller]

Ncrkd,
congrats on getting this build going! Super interested as I am looking to build BBSHD/Alfine-8/Gates on a Specialized AWOL. Staying tuned...

[ncmired]

Ncrkd,
congrats on getting this build going! Super interested as I am looking to build BBSHD/Alfine-8/Gates on a Specialized AWOL. Staying tuned...

Welcome to the group - Bonny Doon, very pretty area!

Likely bad news on the desire for a BBSHD/Alfine-8/Gates belt pairing - consensus is it can't be done. BBS02, possibly yes. Reaching the very tight Alfine beltline with the very broad BBSHD case is the issue.

[ncmired]

Calculated gear-inches - not very wide and not a very low low, but hopefully good enough:

[ncmired]

I finally finished this build and will have some "done" pictures up in a little while. There were a few minor build nuisances. The first was with the Hailong version one Shark battery case clearance with the chain ring, solved with a Wolf Tooth Components B-RAD Mounting Base (available with 2, 3 or 4 holes):

The next was with the Shimano Nexus inter-3 bellcrank and the rocker dropout - if you run into this problem on a build, buy the all-metal version of the bellcrank, from which a fair amount of material can be ground off.

I don't like the Nexus bellcrank - it's big, clunky, and blocks use of a chain tensioner. I'm going to experiment on adapting the old, vintage Shimano 3-speed screw-on bellcrank.

A big positive - every one of the frame cable anchor points were exactly where they needed to be, and none went unused.

[ncmired]

Full view - probably too much dark color in this build - oh well:

BBS02 with Lekkie 42 tooth chainring, 160mm arms:

Rear Nexus 3-speed IGH with a Sturmey-Archer 1/8" thick 24 tooth Dished Cog, along with a TRP Spyre mechanical caliper and 160mm rotor:

Thru-axle, TRP Spyre mechanical caliper and 180mm rotor:

Simple cockpit with a 500C display, grip throttle and shifter:

Bi-directional mermaid badge:

[Rider]

Very nice! How’s your top speed with reasonable cadence?

[ncmired]

Thanks! I took me quite a while to get it finished.

I've got it geared way low to start (42x24), and I loaded the 18amp soft throttle motor config and set the max speed to 23mph. Per Sheldon's (RIP) calculator 90rpm cadence is worth 17mph in third gear.

The Lekkie 42t (minimum) is pretty much a must to hit the chain line, but I do have a pile of rear cogs to play with. A 23t cog will probably be next.

[ncmired]

Spring maintenance & upgrade time - the step-thru Evasion gets an upgrade from 3 to 8 speeds via a new 26 inch wheelset (Schwalbe Fat Frank tires, Alfine 8, Sapim spokes, and Velocity Blunt rims) and a Lekkie 40 tooth chainring. The former Shimano 3-speed operated just fine, but more gear range was desired. The colors were updated, taking cues from the Harley Davidson prototype e-bike and the Bluejay Premiere.

[Mike_V]

Hi
Please write more about the Nexus 3 disk that you had used compared to the 8 & perhaps some other IGHs Thanks !
( for example Nexus 8 or 7 with if only with drum brake enough stopping power? )

Is the Nexus 3 disk with well chosen sprocket a good all around choice ? I hope yeah?

[ncmired]

Hi Mike, here's what I can muster - kind of stumbled together loose thoughts so bear with me.

Your terrain is similar to mine, though I think you've got longer climbs from the low ground to the high ground - probably twice what I have in elevation change.

Sheldon Brown's 3-speed IGH gearing advise was to rethink the gearing for the typical 3-speed setup - from the typical old English bike way of having the 2nd gear as the go to gear, to instead setting the 3rd gear ratio to the flat land gear, lowering the 1st gear as much as the 186% ratio allows (though slightly more ratio than the SA hubs). When I had good legs 186% was good enough, as long as the hills weren't too long or nasty. I don't have good legs anymore.

If you are familiar and used to using gear inches to end up with gear ratios you're used to (and know how hard or easy they are for your terrain), here's a chart for the easiest gearing obtainable with the Nexus 3, in a 26" wheel, with the smallest possible BBS chainring (40T / chain line limited) and the biggest rear cog made (24T):

So, 32 gear inches is as low as you can get. High compared to most MTB or touring bike drivetrain standards. For an e-beach cruiser, good enough. With a BBS02 and a heavy load, barely good enough for short steep climbs (though at a worrisome full wattage) - not good enough for long, steep bastard hills (motor overheating). Worse with 700C / 28" wheels, but much better with 20" wheels (but top end suffers).

The strongest, most efficient gear on most 3-speed hubs is the 2nd / 1:1 ratio gear, when the hub internals are locked to the hub shell.

In contrast, the Shimano Nexus / Alfine 8-speed hubs, at 308% give just that little bit more needed (two more gears on the bottom and one more on top):

A few negatives for the 8-speed - the hub doesn't mechanically shell lock in the 1:1 / 5th gear, and the ratio steps are uneven. The Rohloff and Kindernay hubs offer all that much more range (mostly bottom), and do it with very even steps:

I've no experience with the Shimano 7-speed (other than hearsay that it's a weak hub).

For rear brakes, I don't like the idea of hub integrated brakes where either the braking heat or the brake pad material ends up inside the hub shell - just doesn't seem like a good idea, especially with higher speed ebikes.

You asked, "Is the Nexus 3 disk with well chosen sprocket a good all around choice ? I hope yeah?" - depends on your legs, motor, and terrain. It's a nice hub, and for the longest time could easily be had (with shifter) for $100. Its chainline is also 6mm wider than the Alfine 8-speed, and easier to deal with in some build cases. A negative is that it can't be used on bikes with extra thick dropouts, due to the bellcrank design.

I gear my bikes very low, so that:

• hopefully I have a chance in hell of riding the oinker (bike, load, and me) all of the way back home under my own power, if the motor system dies
• other people I loan my bikes to (some who haven't ridden a bicycle in decades) can ride, manage, and enjoy themselves
• the motor can easily self-power the bike up the longest, steepest hill I (have yet to) encounter, staying under the rated watts
• I still have lots of top end, especially on my Ludi V2 bikes, because of the uber-high motor cadence

Just like for 18-wheelers, gears matter (more and wider the better) - depending on the terrain and the unpredictable wind.

I probably didn't get to or answer what you really want to know - got question(s), ask.

P.S. Here's a vintage Luna build, using a Cyclone and the Nexus 3-speed - I have wondered how it faired:

[Mike_V]

Thanks again because I am enjoying studying these IGH mechanical marvels and didn't want to waste time and money, but then again why make the $ if you can't spend it? I have studied, searched and planned then 'pulled the trigger' on a NOS IGH found on flea bay. I have learned how to recreate your example chart for myself with a 24T sprocket ( 18T is my option ) I have a 36H rim on the way and will order the details to teach myself how to build what should be a nice wheel.

[Mike_V]

Thank you, that's a great summary and nice work because I can follow your design style in your eBike builds.

I do depend upon lots of torque for short steep hills 50# eBike & 200# rider with strong winds and my current build is working fine.
https://electricbike.com/forum/forum...wolfpack-bbs02
I am going to install the 42T chainring, as you have used, to improve chain line.
My new transmission, pictures from the advertisment. MV
Next:

[Mike_V]

My Lucky Super Seven Sachs "Top Technik im Zweirad"

[ncmired]

Thanks!

That's quite a build you've got. Long ago (1990ish) and far away I had one of the early hardtail Cannondale Delta-Vs.