Need advice on CityBug Build

Lightweight / Folding / Portable EVs - seats optional
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Garrett76zt   10 µW

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Joined: Jun 13 2018 10:11pm

Need advice on CityBug Build

Post by Garrett76zt » Jun 13 2018 11:07pm

Hey folks, I'm new to the forum and would love to have some advice on my next project.

Quick background: I have several electric scooters but the only one I've modified is a Schwinn S500 (currie). I did a cheapo 36v controller/throttle combo swap and I run it on 36v12ah worth of SLA's. Low-tech I know but it has been cost effective. I get about 20-25mph out of it and 12ah has proven to be enough capacity for the commute I use it for. One of the biggest advantages of the Schwinn is that the handlebars/stalk/(what do I call it?) fold down so I can put it in my trunk. However with it's larger frame and 36v worth of SLA's it isn't the easiest thing to pick up!

Enter my newest acquisition, The CityBug. Originally sold by Sharper Image I guess. I picked this up from a friend and probably overpaid at $50. Common story I'm sure, sitting around a long time, dead battery, etc. But I was intrigued by a couple of things. It had an aluminum frame, belt driven rear wheel and both the bars and the seat fold down. It's also a bit shorter in overall length compared to my Schwinn. Here's what it looks like once you strip off all the cheapo Chinese plastic fairings.
Scoot1.jpg
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Scoot2.jpg
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Scoot3.jpg
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So this is basically ready to ride sans battery supply and a deck which I plan to make out of plastic. As it sits in the pictures total weight is 21lbs which I think is quite good right?

My overall goals are as lightweight as possible, 12ah minimum capacity/range and 20mph minimum.

My initial concerns with this platform is the small wheel/tire combo. They are 8" compared to my schwinn at 12". So I'm expecting a rougher ride unless I change it up.

This scooter is belt driven which I find interesting. I've already riden it around a bit and its certainly quieter than my chain driven setups. But will this hold me back in the long run when trying to squeeze out more performance?

I'd really like guidance in choosing the correct and simple path to LiPo batteries. I have a little experience with them and understand the basic terms associated with them (series and parallel designations, C ratings, etc.) but have no experience purchasing multiple packs and figuring out how to charge them together for an application like this. This platform runs stock on 24v 12ah SLA's. So do I want to try and use the factory controller and go with a 6s pack or more? The battery box size I'm working with is roughly 6.5"x8.5"x2".

Also I'd love to swap the front fork for something beefier and hopefully with suspension. Any advice there? And I think I want a larger wheel/tire combo but will that require me to switch over to chain drive? Is that better anyways?

So many questions. Hopefully you guys can sort me out and guide me, one step at a time, down the right path. Maybe it's crap and I should ditch it all together, haha.

Thanks in advance!

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ElectricGod   10 MW

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Re: Need advice on CityBug Build

Post by ElectricGod » Jun 14 2018 6:41pm

This scooter would be a fun build! First off get rid of the brushed motor and controller. This scooter would do so much better on a decent outrunner. The motor would weigh half as much, be 2/3 the size and deliver 200% more torque to the wheel. The belt will wear faster on more power, but keep it tight so it doesn't pop over the teeth. Also, this is probably a really cheap rubber belt. There's better belts that hold power better. Bigger sprockets will give the belt more bite and less chance of jumping. Depending on how simple you want to keep it, a castle creations ESC would be a great fit in here or better yet use a real 6 or 12 fet EV grade controller. There's no reason why this little machine can't do 40mph and accelerate like a decent car. Brakes will be an issue. Get rid of the band brake in the back and go to a disk brake. Adding a brake to the front wheel will be interesting. You'll need to mod the front forks. They are too narrow to take a brake rotor and caliper. 80% of your stopping power is in the front wheel. You really want front brakes!

I think I would remove that cross beam in the middle of the battery bay. There's better ways to reinforce the front end and to NOT waste 20% of your battery bay. Lose the seat and factory deck. Figure out how to make the entire battery bay sealed up so water and dirt can't get in.

Depending on how vested you are in this little EV, look around on craigslist, ebay and amazon. There's loads of kick scooters out there that will possibly have forks that will work for you and include a front brake. Get one for parts to revamp your front end. You ARE going to drop money into this little EV to make it top notch, but when done, you will also have a fast EV that is really agile and stops on a dime.
ElectricGod...it's a joke...don't take things so seriously folks!

XB-502 Moped:
https://endless-sphere.com/forums/viewt ... 0#p1222730

Currie scooter:
https://endless-sphere.com/forums/viewt ... 7#p1227407

Garrett76zt   10 µW

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Posts: 5
Joined: Jun 13 2018 10:11pm

Re: Need advice on CityBug Build

Post by Garrett76zt » Jun 14 2018 8:11pm

Thanks so much for your response! I was hoping to have your input as I've been reading through a few of your threads.

I do want to keep it simple to start but I hear you saying that I shouldn't even bother with the factory motor and controller. So can you point me in the right direction for a the motor and controller you mentioned? And if I decide to purchase them then what would be a good matching Lipo pack and charger? Do I need to piece these parts together from various sources or is there one site you can link me to? Also the upgraded belt you mentioned? I've only seen a cheapo replacement on ebay I think. Sorry for being such a noob!

Another interesting thing about this scooter is that it has a lever throttle which has a cable going straight into the controller. I've only ever messed with the twist grip throttles in the past. So I assume that replacing the controller will necessitate a twist grip style?

Garrett76zt   10 µW

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Posts: 5
Joined: Jun 13 2018 10:11pm

Re: Need advice on CityBug Build

Post by Garrett76zt » Jun 14 2018 9:52pm

So I'm eyeballing the Multistar 6s 10,000mah packs at Hobbyking. Is it a reasonable course of action to purchase two of those, get the scooter up and running on stock motor and controller and then collect fork/front brake setup and a 48v motor/controller upgrade and then purchase 2 more of these packs at the same time for a 12s 20,000mah total? Are there good motor and controller combos you'd recommend that would be 48v? It seems that my current battery box size will accommodate 4 of these multistar packs just fine.

Am I thinking about this all wrong?

Garrett76zt   10 µW

10 µW
Posts: 5
Joined: Jun 13 2018 10:11pm

Re: Need advice on CityBug Build

Post by Garrett76zt » Jun 17 2018 6:43pm

Would still love some input on my questions above when ya'll have time.

UPDATE: I was able to source a suspended fork and some 12" wheels yesterday. I still need to buy some axles and bearings but this is the rough mock up. Drastically changes the look of it! I'm loving the additional ground clearance and the fact that I'm gaining a free-wheel hub on these wheels.
scoot4.jpg
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So a few things are evident. I will need to commit to a new motor mount location so that I can bring the rear wheel in. That way I don't need to modify the rear frame and tensioning system. Not too big a deal. Also looks like I'm going to lose the belt drive and go chain unless someone knows where I can purchase a belt sprocket I can bolt onto these wheels? The old one was part of the wheel itself so no way to remove it.
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The front is a bit more of an issue. In order to accommodate the increased tire diameter the front fork will need to get moved away from the frame. You can see I have it ziptied in position. So I'll need to extend the top flange about 2" or so.
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Stop me now if its not worth going to larger diameter but I'm thinking it is.

I don't think the wheels and front fork are particularly high quality but will the type of suspension on this front fork be worth the effort? Am I able to find different springs rates to play around with to get it dialed in? I assume its better than having a solid front fork right?

Really appreciate any feedback!

Garrett76zt   10 µW

10 µW
Posts: 5
Joined: Jun 13 2018 10:11pm

Re: Need advice on CityBug Build

Post by Garrett76zt » Jun 26 2018 11:52am

Making some progress. I ended up ordering 4x 6s 10,000mah multistar packs and intend to run 2s2p configuration. I also ordered a 48v motor/controller/throttle combo. We'll see how that works out. The motor claims 4500 rpms and 1800w. All I know is that it's a beast compared to the original.

I tore the scooter down to the frame last night and got rid of the aluminum braces in the front compartment as well as the originial motor mount in the back. So fresh slate for positioning all the components. Pic below with a rough mock up of what I'm thinking. The 4 battery packs fit snugly in the rear compartment.

I'm going to start from the rear and work my way forward. So I need to put fresh bearings in the rear wheel and sort out the axle and brake situation so I can get the wheel in its final placement, centered in the chassis and then I can focus on motor placement.

Open to input as always.
Scoot7.jpg
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