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

rustywalmartbike

rustywalmartbike

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As the title suggests, I've got some parts I think I could use. Reposting this from a thread on motoredbikes.com, as I felt this would fit here better.

What I have:
-A 1.2 amp 120v universal motor from a vacuum cleaner
-Two 7ah 12v batteries from a UPS
-A 12v to 120v inverter rated at 150 watts
-An old 24" bicycle sitting in my shed
-No regards for how it looks

I'm thinking I could maybe use a dimmer switch to adjust the speed of the bicycle, don't currently have one on hand.

I weigh 120 pounds, do you think the ~140 watt motor would be capable of maintaining at least 10 mph? How should I mount everything without welding, duct tape? zip ties? screwing into the frame?

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Thanks! I see one of them shows multiple lead acid batteries connected to a vacuum motor which is rotating the bike chain. Seems like I would be able to run my motor with the batteries, however the motor in the video appears much stronger.

Another video shows someone drilling a hole into the frame of the bike to mount it, which seems like a good solution. Slightly worried about drilling though, since as my username implies, the bike's rusted. The same video also shows using a drill trigger switch to vary the speed. I have a drill trigger switch, which should work too.

The only other problems are securing the batteries and fitting a gear to the motor. The second video suggests simply tying the batteries in using a fabric strap, but he's using a single lithium battery, which is much smaller and lighter.
Not quite sure about attaching the gear, most people hammer on a gear to the motor shaft. My motor is pretty small, and I'd worry about damaging it.



 
Black100 said:
You gotta be f***ing joking I would not want to be seen riding an ebike like that lol. But if you can pull it off, knock yourself out man.
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lol yeah, it's meant to be awful looking.
I just want something that I can legally drive on the road for about 3 miles that doesn't require as much effort to use. Plus it'll get me positive attention which is always nice
 
Also, someone reminded me the motor won't have enough torque to start with my weight on it and will stall out. Somehow I need to add a clutch to this monstrosity.
 
Black100 said:
Where you at with this Frankenstien ebike.?
May I suggest a cordless chainsaw motor for your bike.
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Currently, not much further unfortunately. A cordless chainsaw motor will probably work much better but I think the idea of a vacuum motor is funnier. I'll probably have to use something like a chainsaw motor though, since the vacuum motor really isn't that powerful.
 
I’m also looking to make an e-bike using a 3-horsepower Eureka vacuum motor. Need some advice building this badboy. Should haulass, since it’s two to three more horsepower than most real e-bikes!!!
 
AdrienEspinoza said:
I’m also looking to make an e-bike using a 3-horsepower Eureka vacuum motor. Need some advice building this badboy. Should haulass, since it’s two to three more horsepower than most real e-bikes!!!
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Welcome to the forums! :cool:
 
You are bumping up against a number of engineering realities.
The first one is torque. You are talking about using high speed low torque motors to power a low speed high torque application. You will need some form of rpm reducer (torque multiplier) to make this work. I would suggest you look at a planetary reduction gearbox because of the space and weight limitations.
Horsepower is a constant and will be the same before and after the torque multiplier.
The other big issue is batteries. Watthours is watt hours and that is what does the work. Call it volt*amp*hours if that makes it easier to understand.
You are going to find that by the time you calculate the volt*amp*hours any combination of batteries you decide on will be approximately the same cost, regardless of chemistry.
Six 12v 20ah ( or 12 12v 10ah) lead acid batteries are going to end up being the same cost (or more) as one 72v 20ah lithium battery but with more weight and no battery management system. They will both supply the same 1440 watt hours of energy.
You are also going to use a significant part of your energy budget hauling those lead acid batteries around.
 
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