Comment, criticize my build. But be nice I’m new!

[Drubieg]

Hello everyone, Andrew here. New to the forum today and my first post. I recently decided I needed an ebike to commute through San Francisico with. And of course, I wanted to build one cus I like building things. I’ve never built anything like this before, and I think I did alright but also have a couple questions.

First, here is my bike.

It is a converted 26” Stranger Creeper Big Bmx. I am using a 72v 3000w MY1020 motor with a MiniKVD Kelly controller. Both I got from Electro & Company with the controller being pre-tuned and the motor upgraded with 10awg wire. I also put together 4 “R5 Shorty” packs from Jag35. They are 36v 13ah packs that I paralleled for 26ah then put in series for 72v. I figured I would charge each parallel 36v pair individually so I can balance them. The motor sprocket is 9t and rear sprocket is 75t. The 3 motor mounts are custom and the batteries I fit in that orange harbor freight pack. New brakes are coming in tomorrow. Bar controls are simply 3 speed throttle and a voltmeter.

Any comments and constructive criticisms are welcome. And my main question concerns the relationship between the controller and batteries. The controller is technically 200Amp capable but is pre-tuned to 33% max battery output. So it won’t draw more than 66amps? My individual 36v packs are capable of 23amps continuous, so 46amps in series? I know I won’t draw that much continuously but do I need to set the max draw lower? Maybe something else? Any advice appreciated and thanks in advance.

 

[ZeroEm]

You don't double the Amps in series just the Volts. Why did you take the peddles off?

 

[Drubieg]

Sorry I meant to write parallel, wouldn’t the amps in parallel be the sum of each? I took the pedals off cus I couldn’t fit the motor and still have room for them. Really the geometry of the bike is not good for this application but it’s what I had and made it work

 

[Papa]

1.) I'm not sure about California e-bike Statutes, but suspect you need, at least, pedals to be legal "bicycle e-assist".
2.) The bike shown should NOT be ridden without a front brake - period.

MY1020 motor

3.) That motor is rated for 6800 RPM @ 72V, so your 9x75 ratio is much too high driving a 26" wheel. I suspect you'll need a 2-stage drive at a minimum.

Really the geometry of the bike is not good for this application....

4.) Got that right

 

[Drubieg]

1.) I'm not sure about California e-bike Statutes, but suspect you need, at least, pedals to be legal "bicycle e-assist".
2.) The bike shown should NOT be ridden without a front brake - period.

3.) That motor is rated for 6800 RPM @ 72V, so your 9x75 ratio is much too high driving a 26" wheel. I suspect you'll need a 2-stage drive at a minimum.

4.) Got that right

I think I read on Reddit that anything over 750w in ca needs to be licensed and registered. I knew from the get go this bike wasn’t going to be “legal”. After seeing for years what people ride there and how they ride them, I’m not too worried about getting stopped.

I do have a new set of front and rear brakes coming today.

What is a 2 stage drive? Can you expand on this so I can make the changes?

Any recommendation on my battery amp output situation?

 

[E-HP]

I do have a new set of front and rear brakes coming today.

So youre changing the forks?

 

[Zambam]

I’d be concerned with the weight and location of the 4 batteries. What’s their total weight?

How is the HF toolbox mounted? Does not look secure as is. Rack does not look strong enough.

 

[Drubieg]

So youre changing the forks?

Negative, there is a mounting hole for c type brakes

 

[Drubieg]

I’d be concerned with the weight and location of the 4 batteries. What’s their total weight?

How is the HF toolbox mounted? Does not look secure as is. Rack does not look strong enough.

I’m not sure actual weight, they are relatively heavy but the rack is rated for 50lbs and the batteries are under that. The box has 4 3/8” bolts securing it so should be alright.

 

[ZeroEm]

Sorry I meant to write parallel, wouldn’t the amps in parallel be the sum of each? I took the pedals off cus I couldn’t fit the motor and still have room for them. Really the geometry of the bike is not good for this application but it’s what I had and made it work

Yes your right., I miss the parallel. The first ebike you learn on. Mine now is my fourth build and have ridden it for 6 yrs.

Drubieg: I think I read on Reddit that anything over 750w in ca needs to be licensed and registered. I knew from the get go this bike wasn’t going to be “legal”. After seeing for years what people ride there and how they ride them, I’m not too worried about getting stopped. I do have a new set of front and rear brakes coming today. What is a 2 stage drive? Can you expand on this so I can make the changes? Any recommendation on my battery amp output situation?

My trike is not legal but you try not to draw unwanted attention. Act like your peddling (I do peddle, jut not very hard.) Don't ride to fast around people.

 

[PaPaSteve]

Your commute around SF must be on the flats ?
Very much doubt the rim brakes, especially when wet, will be enough stopping power on the steep downhills.
Curious ... if your living in Petaluma is the bike for commuting to the Larkspur ferry and into the city ?

 

[Drubieg]

My trike is not legal but you try not to draw unwanted attention. Act like your peddling (I do peddle, jut not very hard.) Don't ride to fast around people.

Yea for sure that’s good advice, I definitely try to ride according to context

 

[Drubieg]

Your commute around SF must be on the flats ?
Very much doubt the rim brakes, especially when wet, will be enough stopping power on the steep downhills.
Curious ... if your living in Petaluma is the bike for commuting to the Larkspur ferry and into the city ?

Flats only, I drive and park near marina and all work is in financial district. All bike lanes to and from are for the most part straight and flat

 

[PaPaSteve]

Very busy part of the city.
I commuted 10 years by motorcycle down from Santa Rosa to work at 3 different machine shops, maker spaces.
One at Pier 9, or another shop at 5th and Howard, or the shop at 20th and Alabama.
Co-workers had all sorts of e-power transportation to get around the city.
Hopefully you have secure places to lock it up.
Cheers

 

[Drubieg]

Very busy part of the city.
I commuted 10 years by motorcycle down from Santa Rosa to work at 3 different machine shops, maker spaces.
One at Pier 9, or another shop at 5th and Howard, or the shop at 20th and Alabama.
Co-workers had all sorts of e-power transportation to get around the city.
Hopefully you have secure places to lock it up.
Cheers

Yes it is, sounds like you know that very well! Luckily every building I’ve been in so far either has a bike locker or I can bring It up on the floor with me

 

[2old]

Nice job fitting everything. The caliper brakes you're ordering will be very weak (FME) because the arms are necessarily long. I had a rear hub bike that I mounted the battery on a front or rear rack or the down tube at various times and it handled best on the rear, so if yours handles fine, go with it.

 

[Drubieg]

Nice job fitting everything. The caliper brakes you're ordering will be very weak (FME) because the arms are necessarily long. I had a rear hub bike that I mounted the battery on a front or rear rack or the down tube at various times and it handled best on the rear, so if yours handles fine, go with it.

Yea, I’m realizing my brake choice isn’t the best but I’m not sure I can even mount disc brakes with my setup. I’ll look more into it I guess.

 

[Drubieg]

Anybody have a suggestion for how to lower my gear ratio? Do I simply need a larger front sprocket and smaller rear one?

 

[Zambam]

I’m not sure actual weight, they are relatively heavy but the rack is rated for 50lbs and the batteries are under that. The box has 4 3/8” bolts securing it so should be alright.

Have you ridden the bike much? How does it handle? The battery (probably at least 25 lbs) looks like it's sitting behind the rear axle. That'd make the front end light. Does it do wheelies easily?

 

[Drubieg]

Have you ridden the bike much? How does it handle? The battery (probably at least 25 lbs) looks like it's sitting behind the rear axle. That'd make the front end light. Does it do wheelies easily?

I rode it around a blacktop a bit and yes the front end wants to pick up when I throttle it hard. But handles fine and as long as I start slower I keep it down.

 

[Zambam]

I rode it around a blacktop a bit and yes the front end wants to pick up when I throttle it hard. But handles fine and as long as I start slower I keep it down.

Get a banana seat + handlebar stem to move sitting position forward. This will allow you to also move battery forward for better weight distribution.

 

[Drubieg]

Get a banana seat + handlebar stem to move sitting position forward. This will allow you to also move battery forward for better weight distribution.

Ok thanks I’ll look into that

 

[PaPaSteve]

Anybody have a suggestion for how to lower my gear ratio? Do I simply need a larger front sprocket and smaller rear one?

To lower the gear ratio implies to have less top speed.
A larger rear sprocket is the correct direction to accomplish that.
Expect more "wheelies".

 

[Hummina Shadeeba]

The small motor sprocket will be loud but because the motor is so fast u really need an even bigger gear ratio. I’d get a different motor with a slower winding. As it is now it’s inefficient and low torque.

Tire Size, RPM, Speed, and Differential Ratio Calculator

Describes the process for converting a gasoline powered car to electric power

www.advanced-ev.com

 

[Hummina Shadeeba]

To lower the gear ratio implies to have less top speed.
A larger rear sprocket is the correct direction to accomplish that.
Expect more "wheelies".

I thought “lowering” gear ratio is reducing the ratio. He needs to increase the ratio with a bigger rear sprocket as you say. It’s pretty huge as is though and wonder if possible. It’s also a tiny sprocket on the motor already and noisy.