First Build: E-Chopper

[BadMedicine]

Howdy, all! After years of jealousy and sweat, I've decided I'm going to build my own chopper-style e-bike. I'd like to get some input as to my proposed ideas before I start ordering parts.
Here are my parameters: I'm not looking to build a racer, but at least 20 mph would be nice. Longer range is always a plus. I do have a pretty firm price limit of no more than 2000 dollars. I'm basically building a toy; something for cruising paved trails, which abound in my area. I'd like it to be as "Motorcycle-esque" as possible, being capable of reaching decent speeds under throttle alone.
My skills: informed amateur. I've ridden bicycles for decades, and done most repairs and maintenance myself. I have some basic knowledge of electrical engineering, primarily with commercial sound installation. Although I built a functional 24-speed bike out of scavenged parts, I've never build any powered bike. I have access to a retired mechanic and biker.
First, the base: I'm looking at stretch cruiser frames, but wondering if I am better advised to go with a single-speed or basic 7-speed (Micargi Mustang or Seattle, respectively). If anyone is familiar with this type of build, I'd love to know the bottom bracket dimensions on these models. Additionally, I would like to know if coaster brakes are feasible with a powered bike, or if caliper (disc, ideally) are essential.
Second, the motor: I'm looking pretty hard at a Bafang mid-drive motor, either a 48v/750w or 52v/1000w. I imagine that a mid-drive is better suited to the long, heavy frames I'm looking at. However, I may be wrong.
Third, the battery: slightly easier for me; matching voltage output with as much aH as I can afford. Bonus points if I can find a way to mount it to the top tube, so as to mimic the look of a chopper's gas tank.
So, my learned builders, I beseech you to bestow your hard-earned wisdom on this humble novice.
Many thanks in advance.

[73Eldo]

I was first thinking of starting with some sort of cargo bike but I think $2000 will be a tight budget. It takes around $1500 for a decent motor kit and battery. Can you or any of your friends do any frame fabrication?

Also does it need to be reasonable and comfortable to pedal or will the pedals more or less be there to qualify as a bicycle?

[BadMedicine]

Although I like the idea of a cargo frame, my existing unpowered bicycle (a Jamis A3 that my wife lovingly refers to as "The TARDIS") has already been heavily modified for cargo commuting. This, I'm more just looking at as a toy.
I've priced out the motor, battery, and frame, and the parts I'm looking at (all mid-quality; not fantastic, but not bad) come just under 2000 dollars (depending on a few variations of motor, frame, or battery).
As far as pedaling ability, I'm basically looking to build an electric motorcycle; the pedals are strictly vestigial, or at most a backup in case of motor failure.

[73Eldo]

The cargo style I was thinking of was like Xtracycle. Really long back end so all you would have to do is possibly change the head tube angle to get the rest of the chopper look.

[BadMedicine]

So first I must say, this site is fantastic. Although I wasn't able to find any threads about a similar build (although I'm sure I just didn't dig deep enough; I can't be the first person to have this idea), I DID find several facts that have
already answered a couple questions.
Things I learned: Disc brakes are not optional. That's the big one, and that informs a lot going forward. It changes my frame choices to 7-speed models.
Remaining questions: what will changing the tooth count affect, especially given that I'm looking at a 7-speed base? The default frame comes in 40T, and most of the mid-drive motors I'm looking at are 44T or 46T.
Also, what wattage of motor should I be looking at, given that the frame weighs between 60-90 pounds? I'm debating between 750w or 1000w. Again, I'm looking for at least 15 mph without pedaling. 20+ without pedaling is even better.

[Retrorockit]

So it sounds like you're going 7speed and disc brakes.At 20mph a hub motor will work OK.
You can play with gearing at Sheldon Brown gear calculator.

https://www.sheldonbrown.com/gear-calc.html

A lot of 7speed stuff comes with a 13 tooth top gear instead of the 11t that 8 speed and up use, so the bigger cogs should be OK. I would go with 46t. maybe even 48t.
There are some chopper fans in this forum. if you start another thread with Chopper in the title they will probably show up.

[lectrik al]

Not a chopper but a pretty easy "build" for a fun as hell run arounder. start with a Luna Eclipse, pretty awesome 25 mph outta the box. Add as much upgrade as you can afford and you could end up with a bike like this


good luck with your project

[AZguy]

As long as there are no very steep hills a straight forward rear geared hub motor would do the trick economically (far more than a mid which I don't think helps for this) and since mentioning throttle operation as primary control then gears, etc. don't really matter and only reason to keep normal pedals (vs. moto style pegs) would be to stay class II legal (more or less) and also pedaling is practical without power or for whatever reason... for a "chopper look" could go with a 20" fat-tire (4") hub (very common like the picture of the folder above) and a 26" skinnier front... be funny with a springer fork =]

If you don't care about pedaling and legal appearance then moto style pegs and a direct drive rear hub would be very inexpensive and the some money better spent on a bigger battery... I'd likely recommend the former but everyone's different...

[BadMedicine]

Thank you!
I've already found a mostly-complete lowrider frame (perfectly rideable as-is without power), including front
springer forks.
The only two things that give me pause with a rear hub-drive is the fact that the base comes with a front 26"x 4" wheel and the rear is 24" x 4". Having some difficulty finding a 24" fat hub motor, but a 26" should fit just fine.
I am looking pretty hard at the Luna BBSHD mid-drive motor, with the "Hot Rod" firmware. Still well within my budget.
Additionally, I have other hesitations related to my own ignorance. If I were to use a rear hub-drive, would I need to find a way to include the existing rear gears and derailleur, or just remove them? Also, would I need to find a way to fit the included rear disc brakes to the motored wheel, or do most hub motors have an included braking mechanism?
I don't know that I would trust front discs alone to stop a heavy powered bike without bucking me over the handlebars.

[Retrorockit]

These guys have been out of business for a while. But the curved frame tubes and triple tree forks might get you started. Rims were 24" with 2.5" tires. The one I saw around here had 24x2.5" Hookworm street tires on it.. Of course skinny 26" in front should work too.
Proedeco Outlaw SS
Just add some ape hangers.
aka Outlaw SE,Outlaw VE, and Outlaw 1200R. No clue what the difference is.
There's an actual 28mph Ebike there if you don't screw it up.

[stts]

Iwaste of time

[stts]

waste of time

[Retrorockit]

An Indian style rear fender with pannier mounted batteries in fairings would look cool. With disc brakes and 26x4 tiresyou can swap front rim size quite a bit
With a BBSHD at 1500W you don't really need hotrod firmware. They're good for about 35mph as is.I think it will simplify thing if you're going with wide wheels.

[AZguy]

One essential component for this build is a large bluetooth speaker to make very loud "potato-potato-potato" moto sounds while sitting at the stoplights

[Retrorockit]

Since you don't want much pedaling you might look at the Cassette Zip Tie Mod in the DIY thread. It allows shifting derailers with no pedaling.

[Retrorockit]

Since pedaling isn't desired the seat can be low and far back. this will prevent OTB under braking.
I'm thinking 2x water bottle batteries mounted on the chain stays like JATO rockets. They will be low and back also. You can finish them off to look like anything you want. Bombs, rockets, fuel tanks,mufflers with fishtail pipes? End caps for all of the above!

[BadMedicine]

The water bottle battery idea does have its appeal, since the frame I'm looking at doesn't seem to have any straight tubes to mount a sharkfin battery to.
The biker child in me likes the tailpipe idea; the Fallout fan in me want mini-nukes.
Decisions, decisions!

[Retrorockit]

I always liked the idea of motorcycle gas caps on E bike batteries.
There's even the possibility of a steam punk locomotive riff.Telescoping connecting rods to both sides of the crank. Too bad he's not an old rail road guy.

[BadMedicine]

Ok, after more research (here and elsewhere) , Ive discovered that I'll need a 120mm shaft on the motor. Looking at a similar build (posted in '17, I believe), looks like this shouldn't be too difficult. Might be a good case for an inverted mount.
Additionally, it seems like I will need an extension for the speedometer cable.
Preferentially, I think I'll go with the aluminum 52t chainring, maximize speed since I'm not looking at hill-climbing.
Add in the drill-less mounting kit for a sharkfin battery, and I'm pretty close to my original concept.
The motors may be out of stock right now (both Luna and Bafang Direct), so I figure I will not this down as a note while I save up.

[Retrorockit]

More gearing doesn't necessarily equal more speed. You can play around with gearing and power at Grin Technology E bike simulator

https://ebikes.ca/tools/simulator.html?motor=MGRIN2706&cont=C35#HowtoUsetheSimulator

Mid drives are hidden in custom settings. Be sure and pick a battery controller with more Amps than your motor.
Basically I myself have a 36mph bike and I can change the gearing all I want and only make it slower.

[BadMedicine]

Additional notes:
it may honestly be a better idea to get a stock BBSHD with a programming cable, then mod the settings myself. Undecided, will depend on availability. Plenty of resources here if I should decide to do it in-house.
After playing with gearing calculators and such, it may be best to stick with the stock 42t chainring, or at most an aftermarket aluminum chainring in the same size. Maintain moderate torque, due to the weight of the frame. We'll call this a secondary build consideration.
Perhaps most importantly, it would be a good idea to replace the stock nylon primary reduction gear with a steel model, given how I plan to ride it. A relatively cheap upgrade that may save a world of headaches.

[Retrorockit]

There is also a stronger plastic gear, the PEEK. This keeps the BBSHD silent if that's what you want.
The gearing equation changes a lot between pedaling and not pedaling. Longer gears are needed to keep a 90rpm cadence at speed, but as far as throttling goes lower is just as good.
I'm not sure what you have in mind for modding a BBSHD. It should be good for 52V as is, but then an upgraded motor controller is needed for 60V and beyond. (Like 2x 36V bottle batteries for 72V). That's where the real power is, but a lot of bicycle driveline parts are already stretched pretty thin at 1500W. I know because I've stretched a few myself. Somebody else will have to help you with power beyond that. I'm already at twice the legal limit for a street Ebike. I personally don't think bicycle tires and brakes are good for much more than that in urban traffic situations anyway. But Iowa is probably a LOT different.
IDK if this would interest you or not. The old Nuvinci 171 CVT hub. It's strong as hell, heavy as hell too. Standard width.

https://cycles.eco/search?type=product&q=Nuvinci*

Looks like an old Moto drum brake.The colr changes with spoke count I think. Cheap enough I put one in my pile. No idea what I'll use it for.
They show 96# of torque input at the hub. but that's after a 2:1 ratio from the chain, so 190# torque at the motor.

[BadMedicine]

Pardon the thread necromancy, but I wanted to give an update on what this project has become.
After scrimping and saving for almost a year, I have begun ordering parts. I've opted to use a Mongoose Dolomite as my base, with a few modifications to achieve the "Chopper Look".
Namely, backswept beach cruiser handlebars and a (heavily reinforced) layback seat post.
I chose to do this after rummaging through the backlogs here and finding repeated mentions of the Dolomite as an easy and cheap build platform. It's also half the price and weight of the Micargi Vancouver I was originally looking at, with much wider availability of information and purchasing options. Additionally, the shorter length should make it a bit more maneuverable.
Although it seems like the Dolomite has had some QC issues in the past, analysis of review trends seem to indicate improved quality of late. At any rate, it seems to be one of the most cost-effective options with standard disc brakes.
For the motor, I am still going to stick with a BBHSD; if my tax returns come back well (and it is in stock), I will get the Luna Hot Rod version. If not, a basic model from Amazon. In either case, I will be using a 120mm model.
I have also decided to go with a Luna One 36t chainring, a 52v21aH Whale Shark battery, and a top-frame mount for the battery (to achieve the faux gas tank look).
Due to my financial situation (paramedics make peanuts, even at high levels), I am ordering it piecemeal. I plan to have all the parts by the end of April.
I believe that ordering all the parts in a deconstructed state will make the final assembly a bit easier; better to purpose-built it from the get-go than have to disassemble something to modify it.
Once everything arrives, I will post pictures of the various build stages.
It should be noted that even with the addition of some vanity parts (handlebars, battery mount, seat post and saddle), the total cost comes in below my original figure of $2000. Patience (and a bit of lateral thinking) truly is a virtue.

[BadMedicine]

Well, friends, it has begun. Still a month or two off from completion, but new questions keep rising as old ones are answered.
First, as you can see, I'm going with a bit more sportster look than a chopper.
Second, I opted for the Mongoose Malus rather than the Dolomite. Even after a deep dive into their specs, I can't find any difference besides the color and $100 (the Dolomite was more).
I'm having a devil of a time getting the spindle out, but that is a known issue with these models. I'm going to take it to the local bike shop and let them crank on it before I do something I can't undo.
Still going to add some fenders, the motor (Luna Hot Rod BBSHD, it's settled), grips, battery mount (behind the handlebars) and the battery.
Here we come to my newest quandary: I know I'm going with a 52v battery, as much aH as I can swing, and going with a sharkfin-type battery. Mounted behind the handlebars on the top tube, it achieves the faux gas tank look I want. I found a couple from a reputable manufacturer, but they have options I am not familiar with. Should I go with the LG4800 model (20aH, BMS amperage unknown) or the Panasonic 3400 (21aH with 40A BMS). The Panasonic is about $100 more, but since I saved that on the frame I'm willing to shell out a little more, if it is better.

[ncmired]

BadMedicine, you mentioned Mongoose quality issues - have you read of any with the Mongoose Envoy? I've got some local interest in a cargo e-bike build, and the Envoy looks like maybe a good lower-cost starting point. There's a BBSHD build write-up on it too.

For the BMS continuous output rating, although the BBSHD is rated 30 amps continuous, I suspect it can spike more, so I'd go with 40 amps continuous and avoid vendors who don't know or don't bother listing the complete specifications. I'd also only choose a shark battery that has the latest, strengthened tray with the power connector near the end - like this:

On batteries, Electricfy Bikes now sells/stocks a Samsung 50G 21700 52V 25AH 50amp BMS shark you might find interesting. I've got one and it's stout! It's also UN 38.3 certified. No, not UL 2849 tested/listed, but a step in the right direction I hope.

With any of the supersized sharks, I think it's best to anchor the tray down using at least three, better all four mounting holes/bolts.

[Retrorockit]

I agree with the 2700 battery. That one has a better bracket than the 48V. I got. 25Ah at 52V. is sweeet. You said no pedaling for this so you will need every bit of that. Check out the zip tie mod. It's all about shifting w/o pedaling.

https://electricbike.com/forum/forum/main-forum/diy-discussion/156222-mid-drive-cassettte-zip-tie-mod

I'd put a gas cap on the battery.