My Grin Giant

[dialing_wand]

Origin bike: Giant ATX 870 '97.

Origin story: I'd been using this bike as my winter commuter while I lived in Montréal. It came with me out east when we moved here. After an LBS failed to let me know that an e-bike I'd had on order (with a supposed "we can absolutely get this for you") wasn't going to be available, my partner suggested I look into repurposing this old thing. I'm glad she did.

The biggest challenge of the whole build was finding new chain rings for the 94/56 BCD triple crankset I've had on it since '98.

Build basics:
- GMAC 8T
- Phaserunner V6
- 52V 23Ah battery

I designed and printed some custom parts including the fairing behind the Phaserunner to hide all the bulk of the cabling. I also used a short 3.5mm TRRS extension to improve ease of access when connecting to the Phaserunner for adjustments.

I made an out-front mount for the CA3 because I didn't like the off-the shelf options. Printed in PAHT-CF. The current design is made to fit perfectly around my stem, and so it might not work on other setups without some changes, however, I'd be more than happy to clean up the model and put the Fusion 360 file on Printables. The 3MF files are already there for the brave: https://www.printables.com/model/495466-ca3-cycle-analyst-out-front-mount-for-e-bikes

Finally, I designed and printed a small mount so I could use the throttle (for controlling regen braking) without it interfering with my old XT trigger shifter. The one downside to this DIY e-bike project was just how many extraneous controls/cables there are to manage. I'll probably ditch the throttle altogether as I've found little use in modulating regen and I don't use the bike without pedalling. Happy to share this model too if anyone wants it.

I've been riding it for a month and while I'm having some minor issues (minor I hope), it's been a pretty great grocery-getter and a fun way to keep this bike alive.

 

[Jeremy McCreary]

Sounds like it could have gone either way — "Grin Giant" or "Giant Grin".

 

[mclewis1]

52v, Phaserunner, and a GMAC ... I'll bet it moves really well. I hope you keep those V brakes and pads in good condition. I like the CA mount out in front of the stem. I did much the same for my builds, only I used a minimal setup with a U shaped strip of metal and one pair of bolts on the stem.

 

[Deacon Blues]

A very nice build.
I'm contemplating using a small Grin motor and bottle battery on a build this winter. My goal is light weight, rather than power and range.
I'd like to keep the weight at or under 30 pounds, but that may be a pipe dream.

 

[mclewis1]

A very nice build.
I'm contemplating using a small Grin motor and bottle battery on a build this winter. My goal is light weight, rather than power and range.
I'd like to keep the weight at or under 30 pounds, but that may be a pipe dream.

30lbs might be possible ... but it will obviously depend on the starting point. Grin's new 340w bottle battery, Bafang 3xx hub motor (front or rear), BaseRunner controller a CA with MFS, PAS disc/sensor and some wiring is going to be 12-13lbs. You'll also need to get creative in the mounting/housing of the BaseRunner. The driven wheel itself will be slightly heavier, you'll recover some weight without the unpowered hub but the spokes (36) and a heavier rim will likely add some weight over a stock light weight road bike wheel ... for a slight net increase.

I think if your donor bike is starting out in the 17lb range you could likely get in at 30-31lbs. You could also easily build an even lighter configuration if you went with only a throttle and no PAS or CA but that likely wouldn't be a very satisfying ride.

 

[JRA]

if you went with only a throttle and no PAS but that likely wouldn't be a very satisfying ride.

Actually that is my preference for my road bike builds. As much as I like a good torque sensing PAS on my eMTB for the more consistent cadence level I use on the road it bugs me there. With the CA3, as well as other controllers, you can set the throttle to any watt output you desire, effectively a cruise control function, and pedal away with no electronic input to the cranks in any gear ratio that gives you the resistance and cadence you desire and can shift away also as you always have on a conventional bicycle. It is easy to up or down the assist via the throttle but in practice I find that it doesn't need to be messed with much. Taking off is really easy with a blip of the throttle also as well as short bursts if necessary.

But I also prefer a front hub motor so there is that plus I use a Schlumph High Speed bb drive which gives me the range of gear ratios that works for me which means I can't use a torque sensing bb anyway........The beauty of DIY is that any option is on the table.