eBike/Art Bike build + some battery questions

zer0zg

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Hello all,

I'm in the design process for an art bike build for burning man. I but I have some questions regarding battery/motor choice that will impact some of the basic bike design decisions I need to make, so I figured I'd ask the experts here.

For background, I'm an aerospace engineer by education, and do quite a bit of fabrication on the side, so I'm not particularly afraid of pretty custom solutions(ie building a pack from scratch.

So the basic idea is I want to build a bit of a lowrider bike with a massive dirt track tire in the back, something like the image below. Tire is 29x15, and will be mounted on 15x12 car wheel. Current plan is for that wheel to mount to a car trailer hub, with a custom frame going to a pretty standard bicycle front end. Speed is definitely not the goal here, but range becomes pretty important given the overall weight of the bike will likely be ~70-80 lbs, and running out of power far from camp will be a long, hot hike. I can't see needing to clear more than 10mph, but 10-15 miles a day would not be unexpected(event is ~1wk). Some decisions to make as follows:

Motor: Leading plan is to keep it simple with 300-500W hub motor in the front. Unfortunately, I can't picture a way this does not preclude me from installing pedals up front, short of mounting a bottom bracket on the fork above the wheel, which somewhat kill the look and likely not be comfortable to use anyway. I'm willing to forego pedal backup, but it does put more pressure on the motor/battery solution being dialed. Curious to get input on wattage tradeoffs given my goals, as well as pack voltage.

Another option would be a chain/sprocket solution on the back wheel, but given the depth of the wheel and the car based nature of it, certainly complicates the rear end fabrication quite a bit. This would allow me to install a unicycle front end, and keep the pedal backup though. Also my suspicion is that the hub motor will be more dust proof(a real concern in this desert)

Battery: Again, leading plan is to go with an off the shelf ebike conversion kit, with a couple of spare batteries, ie buy 2-3 20Ah 36-48v batteries. Keep one on the bike, one spare carried and one charging at all times and call it a day. I do plan on having a solar generator/panels in camp, and could also run a generator/car inverter periodically to charge them.

The other option would be to build a larger pack. Currently leaning against this for a couple of reasons, first, it would make charging trickier, as I would want to be using the bike during daytime hours. Second, I live on the east coast and this whole rig will need to be shipped to Reno, and while I'm comfortable building/using a big battery in an open space, shipping a 30Ah+ lithium battery I built myself is slightly concerning. Happy to be proven wrong by those here though.

Other factors: it would be great to have USB out for lighting on the bike, I know some of the off the shelf batteries have this, and that is super convenient. Of course I could just have a separate battery bank for this, but just one more thing to charge. Durability is also pretty important here for the above mentioned reason, this is a pretty harsh environment.

Thanks guys
 

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Deleted member 4845

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Pedals on the front wheel would be almost completely useless, but then, this is a totally impractical design anyway. Any reason you don't want to make something that would actually be useful, or just paint a picture of the Bike Shaped Object instead?

You could use a fat bike rim and tire, then put a hub motor in it, or use an electric scooter wheel with similar design, or just glue some sticks together and carry a set of handlebars with a bell on it.

I know, ART.
 

zer0zg

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Ha, not the most helpful reply, but the design has crystalized over the past couple of weeks so I'll respond and update.

As far as why? Because I wanna make something silly for a silly event and I find the engineering and problem solving fun. I've already built a 'useful' ebike that I commute on. This is for fun and rolling art is more fun. I mean look how rad the car below is. Sure a golf cart would be more practical than this, but would it bring a smile to anyone's face? I dunno, it's hard to explain why you want to build something just for the sake of it, but suffice to say that building this will make me happier than buying a fat bike or an electric scooter, and that's enough.

valyrien-steel_11749715.jpg


For design, I've landed on taking a front drive recumbent layout, more or less like the image below. In broad strokes, taking the rear triangle off of a bike, flipping it around, attaching it to the steerer, and keeping the bottom bracket. This will allow for an off the shelf rear motor hub motor to be used, while still allowing pedal backup, and generally more reasonable ergonomics.

flow2.jpg


For the rear end I'm building a lot from scratch. I bought a 15x12 wheel barrel and a laser cut wheel center with the BM map on it is in the mail as we speak. I'm using a front hub from a 2000 dodge caravan as it is low profile, bolt on, and accommodates power transmission via splined shaft if I ever decide to power the rear wheel. I'll have some sort of single sided plate mount for the rear wheel attaching to a bit of a tube fender that I can potentially put a second seat pad on. I haven't modeled out exactly what I want the rest of the frame to look like, but at that point it's just connecting the dots between the fender frame and the head tube. It's hard to model myself in cad so I'll likely be doing that on the fly.

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I solve problems for a living, deliberately creating them is just alien to my mindset.

SO, no rear chain drive, you want pedals in the front, that does not leave too many options.

Thought of a friction drive, then how about two electric skateboards installed as running boards that would swing up when not in use, and lever down to ground contact for propulsion.

THEN, how about a removeable mount for the skateboard which uses its drive wheels as a friction drive on the rear wheel? Might need some intermediate rollers to achieve acceptable speed.

You could remove the skateboard and have at least one semi-functional vehicle, like if you actually wanted to get somewhere, and still have the piece of art both by itself and in combination. Two for one.

An artistic interpretation of the car with the ebike in the trunk concept.

OR, you could make the two skateboard running boards both removeable, configure the bike for two people, then BOTH could get off the art, detach the skateboards, and then go somewhere, or, even, two different places at the same time.

But then, you would likely be better off without the bike in the first place.
 

zer0zg

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Interestingly, my contribution to our company values where I work was "Problems are our fuel". You call it creating problems, I call it engineering constraints, haha. I'm also doing a car EV conversion for fun, will it be good as a Tesla or a cost effective solution? Of course not, I used to work there and know how impossible that would be, but that's not the point. Figuring out how to build things no one asked for has served me reasonably well in life, and I enjoy it.

I could absolutely do rear chain drive for pedal power(and electric if I did a mid-drive), but the drivetrain would be pretty ugly. Figure splined shaft in wheel axle with chainring sitting outside the hub mount, down to double chainring behind seat, going forward to a bottom bracket, something like this.

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The friction drive on the rear tire is an interesting idea, ground speed would be identical driving the rear wheel vs driving the ground(minus friction of course), so rollers would not be necessary, and you'd need an axle with two diameters of roller to provide a ratio anyway. Though it might be nice to put smaller wheels on the board to gear it down for slower speed/more torque. That said, the skateboard would have to be one of the off road types to be functional on its own in this environment, I can't see the boosted board type longboard wheels getting much purchase in the dust.

In any case, at this point barring the actual frame dimensions, most of the of the design is locked and parts are ordered, but thanks for the encouragement, haha.

For reference I'm using the following:
Bafang 500W/48V rear hub motor/controller (will be mounted in front)
10AH 48V kettle battery for now, will likely build a bigger pack
18t cassette to single speed converter
Mech disc brake on front
Kent Seachange donor bike to be cut up, keeping downtube/headset, bottom bracket/rear triangle
2000 Dodge caravan front hub for rear wheel
Hoosier 92-15-15 dirt track tire (29" dia)
Bart 15x12 wheel barrel
DIY wheel center
DIY frame

I'll post some progress as parts start to arrive.
 

zer0zg

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So the rear end of this thing is starting to come together while I wait on the actual ebike parts. Got 6x used dirt track tires from a local for free, as long as I promised to send him a pic of the finished product.
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And my test wheel center (simple pattern for checking fit on hub and wheel barrel) arrived and fits pretty much perfect. I'll likely be building a second of of these for my buddy, so I'll go ahead and weld up the wheel, as barrels are surprisingly cheap. Once the ebike kit arrives I'll start cutting up the donor bike to build the front end.

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Saw an article about a guy who built his own Axial flux motor, interesting, artistic, rarely done, looks like you have the skillset. Unfortunately do not remember where, build was fairly straightforward for someone with some tools and some skills.

If interested, I can try and dig it up.
 

zer0zg

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Saw an article about a guy who built his own Axial flux motor, interesting, artistic, rarely done, looks like you have the skillset. Unfortunately do not remember where, build was fairly straightforward for someone with some tools and some skills.

If interested, I can try and dig it up.

Ha, now that is a fun idea. I can't say I'd be confident in my ability to get that built/tuned/tested in time for this year's event, but definitely a cool idea, and the torque density of axial motors is certainly appealing.

Small update otherwise, mounted the smaller (diameter) of the two tire sizes I have on hand just to see how it looks. Ultimately I think I'll go with the larger, but was curious what a 27" vs a 29" diameter tire would look like against the 26" front and it's pretty tough to get a sense of size with these light, thin tires unless they're inflated.

IMG-3010.jpg
 

Seaguy

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Looks like a crazy fun project, full speed ahead! I just installed a 48v Tongsheng conversion that I purchased from Eco E bikes it's in Nashville. I bought it with a 20 amp hour battery that slides into a custom made rear rack. You could buy the battery and it's slide mount without the rack and you could bolt it to anything you wanted. The battery locks in place with a key and is quite powerful. You could buy several of them and have all the power you want. It does have a USB charging port on it and the controller display also has a USB port on it. Don't expect support from eco ebikes and the documentation will be worthless but if it's just the battery no problem.
 

zer0zg

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Despite some distractions finally got a couple of weekends to work on this. Got it running and riding, now just need to make some ergonomic adjustments(like a seat…), install a chain and brakes, paint and light it. Thought I’d share
 

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Snoop

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Despite some distractions finally got a couple of weekends to work on this. Got it running and riding, now just need to make some ergonomic adjustments(like a seat…), install a chain and brakes, paint and light it. Thought I’d share

That is crazy awesome!

Batman would be proud. :)

:devilish: <— (it’s supposed to be Batman)
 

zer0zg

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Yeah, the batpod vibe is real, especially since between the tire and the negative trail of my front end geometry you do need to really crank it over on the edge of the tire to turn, haha. It’s a good thing the playa is wide open and flat.
630
 

Snoop

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Please post pictures from Burning Man if you can. That always sounds like such a cool event to go to.
 
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