24" BMX Sunday Wave C BBSHD

[nowholeself]

I've been working on this BMX build for a while. The goal was to make something extremely light, fast, and fun for short trips around town, and to and from the path trains. So far, it's exceeded my expectations. It weighs about 38 pounds, and has a 42mph top speed. No PAS. No display. No wiring mess. Just throttle and go.

Most current specs:
Sunday Wave C Frame - all 4130 chromoly
Echo Urban 20" aluminum trials forks
Custom titanium handlebars, 9" rise.
Sun Ringle Envy 24" rims
Sapim race spokes
Profile Mini rear hub with titanium axle
Paul Components Disc FHUB
Goodyear folding tires
Tubolito latex tubes
Lekkie aluminum drive cover (with ano stripped)
Lekkie 170 cranks
Speedline Elite Brake lever
TRP Spyke brake caliper
Swiss Stop ebike pads
Hope lightweight rotor, 180mm
40/16 gear ratio.

Battery pack and electrical:
BBSHD
ASI BAC800 controller, bought from Alan at ERT
2x 7s2p Molicel P42A 21700 packs in series - This allows me to use paired balance chargers, thereby nixxing the extra weight and annoyance of a BMS. It amounts to a 52v 8.4ah pack that offers a continuous discharge of 45 amps. I typically don't lose any speed when climbing hills.

Mods:
Nearly every single bolt on the bike, including those on and inside the BBSHD, has been replaced with titanium.
Almost all the bearings in the BBSHD have been replaced with grade 5 ceramic hybrids. Yes, it makes a difference.
The PAS disc, wiring, and circuitry in the BBSHD have been removed.
The throttle wire is a lighter cable than stock, and is run internally through the bbshd via the bottom bracket.

Potential mods:
I'd like to replace the BBSHD engine case with aluminum. Does anyone have a cad model? If I can't get that done, I'd like to at least grind down the fins and top layer of the BBSHD engine case, and replace it with aluminum heat sinks. It would save weight and lower heat.
It irks me that I can't fit the BBSHD inside the triangle. So my next big investment is to make my own engine casing and system. At the moment I'm looking at the Astro 3220 and the Revolt RV-120. Suggestions welcome. Youtube video soon.

[ncmired]

Very pretty and spartan!

Where did you manage to purchase the Lekkie 40T chainring/cover from, and do you know what chain line measurement it ends up with (with whatever that BB width is)?

[nowholeself]

Thanks! I bought it directly from Lekkie, and used Whink's to remove the ano. The bb width of the frame is 70mm. I used a dremel to carve a notch into the backside of the BBSHD secondary gear housing. This notch accommodated the chainstay so that the BBSHD could fit more snuggly and give a tighter chainline. It also allowed me to get both M33 lock nuts on the other side. That modification, together with the Lekkie chainring/cover and one spacer makes my chainline perfect. It's just slightly under 50mm from center line front to back. I've attached some photos I just took so you can see for yourself just how close I had to get the chainring teeth to the chainstay to get such a straight chainline. I also had to reverse the rear cog so that it came out a bit further. The frame was originally made for microdrive chainrings no bigger than 30t.

[ncmired]

The cover looks much nicer bare metal.

Sadly, chainline is our usual dilemma. If the BBS02 version of that chain ring has a similar line, a 68mm BB/BBS02/Shimano Alfine would be close enough to be made to work (another build I've contemplated - I always need gear range where I ride).

[nowholeself]

I agree inre: bare metal vs. 'bling' ano. A small bottle of Whink Rust Stain Remover is about $8 on Amazon. It removes ano from aluminum in only a few minutes. It's easy. You can watch youtube videos of people using it online. I should note, though, that the delayed neurological effects of the acid in that stuff are terrifying. So be extremely careful to avoid any inhalation or contact with the skin, and only use bowls, cups, etc that you can immediately dispose of safely.

Chainline issues with the BBSHD are frustrating for anyone. But they were absolutely enraging for me, because the rear dropouts on a bmx are only 110mm. So the offset that would normally be a workable annoyance on a bike with 135mm+ dropouts was simply unworkable for me. I literally chewed through a mighty mini in a week trying to just run with a crooked chainline. I've included a picture of the notch I carved into the BBSHD casing. It helped.

[Dan816]

Can you explain how you carved the notch? I could use a few more mm of clearance on my BBSHD build and am considering grinding. Thanks.

[ncmired]

110mm? Oh man ...

I've been hoping for a BBS04 - oomph of a BBSHD, but with the last reduction gear case that fits within a 104BCD somehow. I'd guess it would need to have a face gear as well as another inline reduction gear train.

I doubt Bafang or anyone else is interested, what with the built bike price point coming down as it is.

[nowholeself]

Finally got an accurate scale. 38.0 pounds on the nose, battery and all.

[Maverik]

Hey Brah, I really like what you have going on with your bike. But please, tell me what kind of top speed and power i can get from a mid drive. Can i build a bike that will wheelie like a hub drive? and...why have you not built your own frame???? just asking. you seen to have the skills. im a Mechanical engineer and i would love to have the tools and shop to build the things in my head but, im homeless and i have to settle for drawing my bikes. i would love to have an ebike. i just had surg. on my back and cant get around like i need to just to handle my business so i can survive. i really like the simplicity of your build. Great Job! thats how i would do it. ok...gotta run. take care and hit me up.

[nowholeself]

I've posted a couple youtube videos. Ride video soon.

[ncmired]

Thanks much for the video.

Have you considered cutting some weight off of the BBSHD gears, especially the last reduction gear - in a similar way that people lighten flywheels. The pedal spindle is solid (not hollow) - another, easier weight savings avenue.

[nowholeself]

Thanks much for the video.

Have you considered cutting some weight off of the BBSHD gears, especially the last reduction gear - in a similar way that people lighten flywheels. The pedal spindle is solid (not hollow) - another, easier weight savings avenue.

I have! In fact, I emailed Luna shortly after buying the BBSHD asking if there were any aftermarket versions of the final reduction gear. It just struck me as nuts to keep it a solid hunk of steel. Same for the axle. But I don't have the equipment to properly trim weight from those myself. And I don't think it's worth the cost a machinist would charge me. So at the moment I'm just working on designing a new engine myself.

[joost]

I've been working on this BMX build for a while. The goal was to make something extremely light, fast, and fun for short trips around town, and to and from the path trains. So far, it's exceeded my expectations. It weighs about 38 pounds, and has a 42mph top speed. No PAS. No display. No wiring mess. Just throttle and go.

Most current specs:
Sunday Wave C Frame - all 4130 chromoly
Echo Urban 20" aluminum trials forks
Custom titanium handlebars, 9" rise.
Sun Ringle Envy 24" rims
Sapim race spokes
Profile Mini rear hub with titanium axle
Paul Components Disc FHUB
Goodyear folding tires
Tubolito latex tubes
Lekkie aluminum drive cover (with ano stripped)
Lekkie 170 cranks
Speedline Elite Brake lever
TRP Spyke brake caliper
Swiss Stop ebike pads
Hope lightweight rotor, 180mm
40/16 gear ratio.

Battery pack and electrical:
BBSHD
ASI BAC800 controller, bought from Alan at ERT
2x 7s2p Molicel P42A 21700 packs in series - This allows me to use paired balance chargers, thereby nixxing the extra weight and annoyance of a BMS. It amounts to a 52v 8.4ah pack that offers a continuous discharge of 45 amps. I typically don't lose any speed when climbing hills.

Mods:
Nearly every single bolt on the bike, including those on and inside the BBSHD, has been replaced with titanium.
Almost all the bearings in the BBSHD have been replaced with grade 5 ceramic hybrids. Yes, it makes a difference.
The PAS disc, wiring, and circuitry in the BBSHD have been removed.
The throttle wire is a lighter cable than stock, and is run internally through the bbshd via the bottom bracket.

Potential mods:
I'd like to replace the BBSHD engine case with aluminum. Does anyone have a cad model? If I can't get that done, I'd like to at least grind down the fins and top layer of the BBSHD engine case, and replace it with aluminum heat sinks. It would save weight and lower heat.
It irks me that I can't fit the BBSHD inside the triangle. So my next big investment is to make my own engine casing and system. At the moment I'm looking at the Astro 3220 and the Revolt RV-120. Suggestions welcome. Youtube video soon.

Have you seen the updates to the asi bac

https://electricrt.com/blog/4872v-asi-bac-controller-profiles/

“BBSHD BAC800 kit has been tweaked, and the motor is able to rev to 11,000RPM on 52V.” I am talking with Alan to send my controller in for an upgrade.

[Gizmo350k]

Sweet mary mother of god you guys are geniuses. I'm wondering if you would offer your titanium bolt kit for the BBSHD for sale on ebay? I too wish to lighten up the motor to achieve maximum climbing!!

[nowholeself]

Sweet mary mother of god you guys are geniuses. I'm wondering if you would offer your titanium bolt kit for the BBSHD for sale on ebay? I too wish to lighten up the motor to achieve maximum climbing!!

Thanks! I used Armorbolt.com for most everything. They're fairly affordable and shipped quick from the U.S. All the sizes are M4 through M8 and listed in the BBSHD manual with lengths. Let me know if you run into any snags.

[.Eek]

Nice build! One of the few clean BMX builds that I could find on Youtube.. Working on a similar build, but based on a NS Suburban, with a bigger pack.
Does the extra weight effect bunnyhopping a lot?

Cheers, Kris

[nowholeself]

The weight effects bunny hopping a bit, yes. But it's still light enough to achieve. If you are interested, I have since manufactured a prototype of an electric bmx with a properly integrated engine. It achieves the same performance as my bbshd build, but weighs only 33lbs, and is made out of titanium. I'm aiming to launch this summer. It's called the Chimera, and you can find me showing the prototype off at the Chimera Cycles Instagram.

[.Eek]

Cool, I'll follow on Instagram.