First e-bike build: GNG Gen2 36V 350W Conversion

New member, been lurking awhile, gathering intel.
Just wanted to put a quick post up announcing a my first e-bike project. I hope to post a detailed account of the build.

Context:
I have a mechanical engineering degree, and think anything that requires an imaginary number to perform calculations is probably dark magic. That said, I have enough knowledge of electricity to know when to ask questions and when I am out of my depth. My 13 year old son approached me with wanting to do an e-bike conversion as a summer project together. He wants something he can run down to the local towncenter on, have some fun, and have an easier time with the local hills. I had already been considering some ideas for my own projects. And thought his bike frame would be a good learning process for us both. So I started doing some serious online research and ended up here. After many articles, blogs, posts, links, online catalogs, etc, this is what I I've decided on:

I'm not a bike nut, but I used to commute with a hybrid (mountain bike frame, road tires and gearing) a few times a week, about 8 to 10 miles round trip. But got too tired of lugging my laptop backpack, and a sore butt.

Bike:
mid to low-end? specialized "Hot Rock" with front suspension (~$free. Available)

Motor Kit:
GNG Gen2 36V 350W mid-drive BB mount. (~$400. Didn't think my son needed more power than this. He's responsible and cautious, but no need to go crazy. Not trying to break speed records. Also the 36V batteries are generally cheaper than 48V.)

Immediate upgrade:
Mounting plates from lightingrod AKA Mike.

Battery:
36V 12aH LifePO4 headways pack from EV-Assemble. (~$400. While heavier and more expensive than LiPo, they are better than SLA, and safer than LiPo. I have some experience with various rechargeable chemistries from time in the RC car hobby, but nothing this large. My son has very little experience with this kind of thing, and I wanted something safe.)

The motor kit came today, unpacked it a bit and it looks great. The battery is in transit.

For various reasons, I won't be able to start the project for about 2 more weeks. I'll try to get some pictures of the components together before then.

Thanks to all that have unwittingly provided me a starting point. More to come.

This is the bike I'm planning to convert and the motor kit. Mounting the controller and battery are going to be tricky. I'm thinking I'll just get a seat post cargo rack and a waterproof bag. Or maybe fab a custom container box out of some sheet aluminum?

Other upgrades in consideration:
Adding disc brakes to the bike. Do people think this is a critical safety feature?
Adding an on/off switch.
Adding a brake activated kill switch.

Have not received the battery yet. And still waiting on the upgraded mounting plates from lightningrods. But had my son this evening so decided to use the stock mount for now and get some build time together.

Getting the old BB off was a bit of work. One of the rings was really on tight (also didn't realize it was a LH thread at first. Oops).

Like many others, the stock mounting plate was bent on arrival, but easily readjusted.

Also like some others have posted, it was difficult,to get the new bottom bracket rings threaded on correctly and not cross threaded. After about 20 minutes of careful fiddling, final got the right side, only to have my son point out that we should have put the motor on first. Oops. Pull it back out, line up the mounting plate for the motor and try again.

There is just some slight play left and right in the spindle. We could not get the left side tightened all the way to the bearing. I read someone else had a similar issue, and was able to shim it up. Might have to try and find some shims.

Got the new crank installed and the arms and pedals. Broke the little clip on the motor chain, trying to get it off. Need to go to the LBS.

When we turn the crank, it feels smooth, and seems pretty true.

I don't wanna be a downer but the motor is going to be really low on that frame....enough to scrape a curb if you ride off of it. I put the motor frame strap on the outer (front) bolt to get more room under it. You can do it and it will be fun, but it would be more peace of mind to have it higher.

I'm a pretty frugal and knowledgeable bike enthusiast and this frame would be a good starting point.

http://www.pricepoint.com/Brand/Sette/Sette-Reken-Alloy-Hardtail-Frame.axd

You can get a decent bike build up for 400-500 that will handle all the bumps in the world as well as have disk brakes.

Thanks for the suggestion, but one of the points was to convert his existing bike. We pedaled it around with the motor off a bit and the clearance seems ok for the intended purpose. We can always scavenge garage sales and thrift shops for more suitable frames at a later point.

Electric Junk said:

I don't wanna be a downer but the motor is going to be really low on that frame....enough to scrape a curb if you ride off of it. I put the motor frame strap on the outer (front) bolt to get more room under it. You can do it and it will be fun, but it would be more peace of mind to have it higher.

I'm a pretty frugal and knowledgeable bike enthusiast and this frame would be a good starting point.

http://www.pricepoint.com/Brand/Sette/Sette-Reken-Alloy-Hardtail-Frame.axd

You can get a decent bike build up for 400-500 that will handle all the bumps in the world as well as have disk brakes.

Click to expand...

Nice find! You could swap out everything from the existing bike to this frame! Headset spacers would be the only thing extra, looks like. As far as brakes go, average V-brakes are as good as middle grade disc so you should be fine. May need red pads for higher speed/loads, but you'll soon learn to coast up to stop signs and traffic lights.

If you go with this existing frame, you may want to "clock" the motor to move the input wire to a top location where it will be safe from damage. Don't know why they left it hanging out the bottom, or have they changed that yet? My kit is from the first batch last year...

Been awhile since we have gotten to work on the project. Other things going on. Need to connect up the wiring, and the motor chain and that's about it. Hopefully will finish today.

Some photo updates

The battery came with different connectors than the motor kit. hmmm,....Need to run to my local hobby shop and pick up some connectors. I was thinking the Traxxass ones?

Got the wiring figured out no worries. But then the motor chain was almost too short to get on. Tried to extend it by a couple links but then it too long and the tensioner wouldn't take up the slack. Finally got some wire around a couple links and my son pulled while I was able to get the master link in place. Went for a first easy test ride. Very smooth, no problems!

Video on youtube:
[youtube]qizR379x1qY[/youtube]

What city/state are you in? I have plenty of XT-60's and XT-90's

http://www.hobbyking.com/hobbyking/...tors_Male_Female_5_pairs_.html?strSearch=xt90

very good, not much footage around of gen2s running. Couldnt you put the motor inside the triangle of the frame so it doesnt hang down so low? or are you still wanting to put the battery in there?

to embed youtube links just use the last of the link you have which from http://youtu.be/qizR379x1qY is ......qizR379x1qY

[youtube]qizR379x1qY[/youtube]

Thanks for the YouTube post tip. Tried it inside the triangle but not enough room. The bike frame is actually too small for my son. Will probably replace it this summer, with a more standard frame without the swoop that causes it to ride low. Not really planning on any offroad action so not too worried about the low clearance. We just have a couple size able hills so this kit would be good for that. I forgot to specify the battery config that would have fit in the triangle, so we just got a bike rack bag to stuff the battery and controller in.

What happened? He's about 16 now. I wish id gotten a powered bike back then. 48 volts. With the Li-iron why not.