Convert Coaster cruiser bike to ebike help

[Andrenav03]

Hey guys been having this coaster bike for a while now and I want to convert this bike into an ebike. I’ve converted a mountain bike with a drop out to an hub e-bike, I want to try something new.

I want this cruiser bike to have regen braking and be as light as possible.
I’m not sure if I should put a hub motor in the front wheel or a mid drive motor. I don’t know if I can put a hub motor in the rear dropout because it’s a horizontal dropout ( I’m not an expert)

Also a 750w motor is what I have my eye on but i would like to pedal the bike when battery is low and regen to charge it a little bit. So I don’t mind getting a 250watt motor for the weight.

Lastly for the battery I want pick up a water bottle size battery 52v 10ah maybe if they sell it lol or whatever small battery I can find.

Thank you for your time and feedback

 

[docw009]

Regen braking requires a direct drive hubmotor, Not aware of any mid drive kits with regen,

Looks like you have a normal square taper bottom bracket for the pedals, and the forks are threadless. The later could be swapped out for forks that are disk brake compatible, That gives you a second brake and a possible front motor, The former makes it easier to install a mid drive,

A nice candidate for a mid drive is a coaster brake TSDZ2B, but it's pretty gutless unless you have the smarts to load up third party OSF firmware. It is only about 300-350 watts, so a small bottle battery could power it for a while,.You could probably get it up to 18-20 mph in OSF cadence mode on 48V w/o doing much pedal work. I don't know about stopping though,

Otherwise, keep the rear wheel as is, and install a hub motor on a new fork. I have no experience with direct drives and have no suggestion, I think 750W DD with a small bottle battery is not going to work.

 

[neptronix]

With this kind of frame, the chain holds the wheel in the frame basically.
You could us a direct drive in the rear, given that you rely on regen for braking.

I'd only do that with a 1000w rated motor though, and a big battery ( 20ah ) that can take in 1000w of regen, which would be the equivalent of a medium strong brake. You also need a controller that can be tuned to run a high amount of regen.

But this goes against your quest for lightness. Regen means you need at least a 10lbs motor and probably a 10lbs battery.

If you want light and you're okay with giving up regen, a geared motor is the way to go. Normally i'd say mid drive would be best if you have hills to climb, but you have no gears, so the mid drive offers no advantage other than centralizing the weight. A geared motor will cost less and in most cases weigh less, too.

 

[tomk]

Regen braking requires a direct drive hubmotor, Not aware of any mid drive kits with regen,

Looks like you have a normal square taper bottom bracket for the pedals, and the forks are threadless. The later could be swapped out for forks that are disk brake compatible, That gives you a second brake and a possible front motor, The former makes it easier to install a mid drive,

A nice candidate for a mid drive is a coaster brake TSDZ2B, but it's pretty gutless unless you have the smarts to load up third party OSF firmware. It is only about 300-350 watts, so a small bottle battery could power it for a while,.You could probably get it up to 18-20 mph in OSF cadence mode on 48V w/o doing much pedal work. I don't know about stopping though,

Otherwise, keep the rear wheel as is, and install a hub motor on a new fork. I have no experience with direct drives and have no suggestion, I think 750W DD with a small bottle battery is not going to work.

I built a cruiser with a 500W front hub motor a few years ago, using a $150 Walmart bike, Left side is with a 36V bottle battery and original rim brakes. Right with disk brakes and a 48V downtube battery. Don't care about speed. Just ride it relaxed and slow.
View attachment 378244 View attachment 378242

These types of front wheel hubs are what i am looking for - "just ride it relaxed and slow". Can you provide the vendor/brand and type/name of these drive kits? It would give me a start what to look for.

 

[Acme Anvil Corp]

I have been down this road before. IMO beach cruisers are ideal for ebike conversions, but you have to consider a few things.

First, with a coaster brake cruiser, you have narrow rear dropouts that won't easily fit a rear hub motor. You can either grind the axle or stretch the frame (only if it's steel). When you finally get the hub to fit, you suddenly have a bike with no brakes. Regen will slow you down but not to a complete stop.

Getting a donor cruiser with a rear derailleur solves those issues. A rear hub will bolt right in, and you can decide whether to keep the gears (totally redundant if you have a motor) or switch to a single speed sprocket. The flip side is with those bikes you lose some of the stripped-down cruiser aesthetic, and the satisfaction of a kick brake, which is just plain fun.

If I were you I would put a small geared motor on the front. Change out the front fork for one with a disc brake tab, and run a cheap mechanical front brake. That plus the kick brake will give adequate stopping power. This is a super-easy first build.

A third option is to troll marketplace for purpose-built e-bikes people are unloading. In LA they are a dime a dozen, whether you use them as is or as a platform to start modding. You might want to pick one up for parts -- get a hub motor, controller, fork, brakes and maybe a usable battery for less than the cost of a mail-order kit.

 

[2old]

I've built a few cruisers with front hub system and they were great for errands. One used only the coaster brake for stopping, but that was adequate. You're not going to DIY a light bike by starting with a cruiser since many have steel frames and most heavy components.

 

[HardWaterATX]

I will second the notion of putting in a low power mid drive and throwing a disc brake fork on it.

Here’s one that would fit the bill, match the bike and look kick ass Coaster Cycles Double Crown Fork, 1-1/8" Steerer, Cargo Bike, Pedicab | eBay

 

[MxusMick]

That frame resembles a 79 Cook Bros Racing 26" cruiser, highly valuable, maybe it's just a knock off, but if it is leave it be.