Idea for a supercheap ebike made from a repurposed vacuum cleaner motor, UPS batteries, rusted walmart bike, and electrical junk from home depot.

Mossy

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jetpackjbf

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Well, I have a "4000w" power inverter. To even get close to 4000w out, one would need a minimum of 170amps in. Most car batteries are ~50amp/hr. You would need three car batteries to make that 4000w, and it would last less than an hr at peak power. You are talking about taking two 7amp batteries, far too little. For 1000w, you will need ~40amp/hr.
That's true, but my motor is only 140 watts, or around 11.7 amps from the battery. I have succesfully run the vacuum off of an inverter connected to a single battery before, so I'm not too concerned.
 

Urban Fatbiker

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That's true, but my motor is only 140 watts, or around 11.7 amps from the battery. I have succesfully run the vacuum off of an inverter connected to a single battery before, so I'm not too concerned.
You'll never get even a fraction of that 140W power delivered to the road. A bench test isn't realistic as there's no applied load. Locked-rotor amps will rapidly deplete batteries, and windings of that motor are way too small, it was made for high RPM not torque.

Honestly I don't see that motor pulling its weight in batteries and inverter.

I do see it letting out lots of smoke trying, or the inverter will simply overload.
Or both!

Test in well-ventilated area away from hazards, wear PPE. AND...take video! It'll be cool.
The vid...not the motor, it'll be smoking!
 

jetpackjbf

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You'll never get even a fraction of that 140W power delivered to the road. A bench test isn't realistic as there's no applied load. Locked-rotor amps will rapidly deplete batteries, and windings of that motor are way too small, it was made for high RPM not torque.

Honestly I don't see that motor pulling its weight in batteries and inverter.

I do see it letting out lots of smoke trying, or the inverter will simply overload.
Or both!

Test in well-ventilated area away from hazards, wear PPE. AND...take video! It'll be cool.
The vid...not the motor, it'll be smoking!
Haha, yeah I expect some smoke on my attempts. I hope to achieve at least 75w of actual power output? I mean if people are able to go ~5mph using a cheap coordless drill, I would hope my setup would be a bit more powerfull.

You mentioned locked-rotor amps, which I didn't account for. The inverter is rated at almost exactly what the motor is supposed to draw, but I doubt it can deliver enough starting current. I have a UPS which has a pretty beefy inverter, I've managed to run the vacuum off just the inverter and a single battery. Problem is that it got partially fried when I accidentally connected it in reverse polarity...

This leaves me with two options:
1. Attempt to fix the UPS inverter (my soldering skills are terrible)
OR
2. Pull start the motor to get it spinning before applying power

1652101232944.png

Is it unrealistic to achieve higher torque with heavy gear reduction? Or is that going to end with the motor stalling upon even trying to drive gears..
 

jetpackjbf

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I forgot to add this here, I plan on adding a simple clutch to the motor, to allow it to gain speed before engaging the gears
 

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rusty.western.flyer

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A hand drill motor and vacuum motor are nothing alike. Would you try to run your air compressor with a vacuum cleaner motor, or vice versa? Also, the drill motor as a transmission and planetary gears built in. DeWalt used to have a pit bike that ran on an 18v drill. https://www.asme.org/topics-resources/content/make-way-for-drillpowered-bikes A couple friend at the track had them back in the day. They were quite expensive IIRC.

Simple bench test to display. Take the batteries, inverter, and vacuum motor and hook them up. Shove a pencil in the fan, flip the switch and watch the magic smoke leave the motor. Alternatively, start the motor, then shove a pencil in the fan and watch it self destruct.

Another engineering standpoint to think about: What is the diameter of the armature shaft in the vacuum motor? You add a clutch, get the motor going, engage, and the motor will be playing "divided and conquered". How do you plan on transferring the rotation of the armature to the bicycle?

I'm almost hoping you will do this just for the entertainment factor.
 

jetpackjbf

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A hand drill motor and vacuum motor are nothing alike. Would you try to run your air compressor with a vacuum cleaner motor, or vice versa? Also, the drill motor as a transmission and planetary gears built in. DeWalt used to have a pit bike that ran on an 18v drill. https://www.asme.org/topics-resources/content/make-way-for-drillpowered-bikes A couple friend at the track had them back in the day. They were quite expensive IIRC.

Simple bench test to display. Take the batteries, inverter, and vacuum motor and hook them up. Shove a pencil in the fan, flip the switch and watch the magic smoke leave the motor. Alternatively, start the motor, then shove a pencil in the fan and watch it self destruct.

Another engineering standpoint to think about: What is the diameter of the armature shaft in the vacuum motor? You add a clutch, get the motor going, engage, and the motor will be playing "divided and conquered". How do you plan on transferring the rotation of the armature to the bicycle?

I'm almost hoping you will do this just for the entertainment factor.
I think it's around 1cm in diameter, but I'll measure it when I need to install a gear/wheel.

I already have some wheels and a belt from a lawnmower transmission that I could reuse, but I worry the belt may slip too much and won't be able to move the bike. Plus I would need to attach a wheel to the bike wheels (if that makes sense), which could be hard as there is limited space.

My uncle has tons of bikes and scraps, and I might be able to get some gears from him (or just buy some online). From what I know, adjusting a chain's length can be a pain, but it might be worth it if gears will work better.

The bike would be for entertainment mainly, but my goal is to make it to the gas station ~1.5 miles from my house. That's really pushing it, but it'd be nice.
 

Urban Fatbiker

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Methinks any gearing or drivetrain added to it loads it down too much. Actually pretty sure. Unlike air, it'll be loaded trying to get to speed, that speed either 1800 or 3600 RPM depending on motor winding.
Any less than that, heat and amps begin eating your power, making UPS shut down in overload.

Wear PPE, I'd add a cup, and fire pants if ya gonna try to ride it first.
Me, I'd flip the switch from a distance.
Behind a wall.
(thats fearmongering...I expect smoke and UPS shutdown)
 

rusty.western.flyer

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Definitely fear mongering. I have created several k BTU waste oil burners, raced cars for years (145mph twice every lap Daytona Rolex circuit), been in crashes as fast at 135mph, pop the strut tops off car strut with my heels and an impact (let them fly across the shop floor), crashed my first full size motorcycle (enduro in the sand) at 9yrs old, crashed who knows how many since, been on fire a couple times (usually a shirt catching when welding/grinding), been shocked by 200amps DC on the TIG machine, got stuck to a 110v circuit until someone knocked me away, use ether to bead stretched tires, had my hand wrapped in a drill press, bones sticking out the fingernail, saw cuts and many more. For approaching 50yrs, probably have 100yrs+ worth of mileage on this chassis.

Just be safe, but honestly that motor will be not much more than some smelly smoke and popped breaker/fuse.
 
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