Hoverboard prototype help

levitri

New member
Hi, I need help with some calculations for a budget hoverboard project I'm attempting. What I'm envisioning is really an oversized, remote controlled drone that can lift a person. I want to make it as compact as possible while still being usable. I am trying to calculate a formula to find the minimum diameter the EDFs could be based on the require pounds of thrust by the number of fans (4). I may be way off. Please let me know what I can do.
possibly helpful notes: I weigh about 54 kgs and the board will have edfs, (not possible to calculate their weight obviously) a wooden skateboard deck (about 2kg), a bike battery (about 10kg probably) and possibly a gyroscope for stability and remote control technology. (total maybe 16kg give or take, total weight excluding fans is around 70 kg will need 75kg for good lift)
 

JasonK

Participation Award Recipient
IIRC EDFs aren't the best for static thrust, but high speeds. given that your trying to hover, you need static thrust. It isn't going to be a pure "how big" measurement to get the needed static thrust, as blade pitch, number of blades, etc will all play into the amount of static thrust you will get from the motor.

As to how much thrust you need, you need to figure out your total weight (including fans), then divide that by the number of motors/fans and then each one would need to do some % more then that.

That said, some sort of hoverboard (IE with a "bag") is going to take way less power then something that can just raw lift you off the ground.

hacksmith did a hoverboard, but that used magnetic levitation, not thrust.

There are also some flight suits out there - very much prototype things - and your basically talking about something similar to a flight suit in capabilities, but that you can stand on vs wear.

The only thing you have going for you over a flight suit with a hover board, is that you may get some level of ground effect help with "floating" (there is some additional lift that you can get when very close to the ground from the interplay of the airflow with the ground itself - but for a hover board, your probably talking inches.)
 

Brian B

Elite member
Maybe try a skirted hoverboard (hovercraft) first? Work your way up to skirt-less board later? To pressurize the plennum, look at Flite Test Star Wars speeder project. But a big prop in a properly designed nozzle (self-designed EDF) would likely be better than any off the shelf EDF.
 

levitri

New member
IIRC EDFs aren't the best for static thrust, but high speeds. given that your trying to hover, you need static thrust. It isn't going to be a pure "how big" measurement to get the needed static thrust, as blade pitch, number of blades, etc will all play into the amount of static thrust you will get from the motor.

As to how much thrust you need, you need to figure out your total weight (including fans), then divide that by the number of motors/fans and then each one would need to do some % more then that.

That said, some sort of hoverboard (IE with a "bag") is going to take way less power then something that can just raw lift you off the ground.

hacksmith did a hoverboard, but that used magnetic levitation, not thrust.

There are also some flight suits out there - very much prototype things - and your basically talking about something similar to a flight suit in capabilities, but that you can stand on vs wear.

The only thing you have going for you over a flight suit with a hover board, is that you may get some level of ground effect help with "floating" (there is some additional lift that you can get when very close to the ground from the interplay of the airflow with the ground itself - but for a hover board, your probably talking inches.)
would any motorboat (hovercraft) propellors work? Just searched up "40-50 lbs thrust propeller" and they're all for boats but I'm not sure if they're several use kinds of things.
 

JasonK

Participation Award Recipient
would any motorboat (hovercraft) propellors work? Just searched up "40-50 lbs thrust propeller" and they're all for boats but I'm not sure if they're several use kinds of things.
props for use in water are going to be useless in the air.
 

JasonK

Participation Award Recipient
here this might help frame your research:

Converted into funny units this is 0.05 HP per pound of mass. 1 HP can hold 20 lbs in the air, but that will not be enough to even spin up the propeller unless it can adjust blade pitch. For practical usability I recommend to double that number. If the propeller diameter shrinks and disk loading increases, efficiency will drop and the power required will rise.

Which would mean to hold up 200lb, you would need a 5 HP motor (well really more then that)
or around 7.5KW of power

based on the efficiently above if you wanted your craft to work for 10 minutes, you would need a ~10 kg lipo battery
lipo Specific energy: 100–265 W·h/kg
7.5kw * 10 / 60 = 1250 wh or around 10kg (22lb) of battery

Then you need electric motors that can run that power level (this is just one drone type motor that I have found.. math said you need something 3x as efficient as this to get the above efficiencies):
https://www.brotherhobbystore.com/tornado-t5-3115-pro-motor-p0088-p0088.html (116g each)
the best "full throttle" results they have there is about 5 g/w at About 725w in and 3400g static thrust out

your 200lb would need around 91kg of static thrust or about 30 of those motors [so the aviation calculation got 3x as good of a power in to thrust out as this motor - so using this motor you would need 3x the battery calculation above]

30 of those motors would be about 3.4kg or 7.7lb of motor to account for in your over all weight.

I suspect your would need to use a more static thrust efficient prop then that motor is setup with for that test [which was already using a 13" diameter prop]

oh, and we are ignoring the need for more then 1:1 thrust to weight ratio as you need some extra, so that the flight controller has "room" to adjust thrust across the different motors to keep it stable.
 

JasonK

Participation Award Recipient
if you search youtube for hovercraft diy, your going to find all stuff that is much bigger then a skateboard, and those all have skirts, which allows it to only clear the ground by a very small amount... and they make very major use of the ground effect to make that happen.

I honestly don't think a "hover board" like your thinking about is in the realm of working, due to limitations of the materials/power density of batteries/etc we have to work with [outside of things that have almost zero clearance and only work on perfectly smooth surfaces or work via magnets over a metal surface, etc]

edit: here is an example hover craft, notice in this video on the flat surface, a clipboard didn't make it between the skirt and floor
 
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telnar1236

Elite member
I hate to be the bearer of bad news, but the battery/EDF technology we have today just isn't up to building a practical hover board. As others have mentioned, you would end up with something extremely heavy and with barely any flight time. A bike battery is absolutely incapable of outputting the enormous power needed to lift a person for more than about a second, and, while it would most likely just kill the battery, it could light on fire or explode if this was attempted. Stability would also be an issue. The power system needs to be able to produce a large enough moment to counteract destabilizing forces like gusts of wind or the pilot leaning a bit to one side. In a skateboard sized frame, the EDFs simply are not far enough from the center line to do this effectively, so you would need a design more like the quadcopter formats others have posted.
A hoverboard would probably also be extremely dangerous for its pilot if something went wrong since it cannot glide or autorotate or similar, and I would not personally be willing to trust my life to the reliability of RC grade EDFs.
 

L Edge

Master member
Only way to do the hover board is by using 4 RC jet turbines where the fuel provides the input source of enough energy for the project and set to like a helicopter FC where you can hover(fixed altitude) and then have a transition and forward flight standing on the board. This would be done by tilting the jets. Also, would need to use software to fly and land if one turbine conks out.

With 4 turbines costing $25,000 and $75,000 for the rest, anybody spot the cash?
 

Morgan G

New member
Hi, I need help with some calculations for a budget hoverboard project I'm attempting. What I'm envisioning is really an oversized, remote controlled drone that can lift a person. I want to make it as compact as possible while still being usable. I am trying to calculate a formula to find the minimum diameter the EDFs could be based on the require pounds of thrust by the number of fans (4). I may be way off. Please let me know what I can do.
possibly helpful notes: I weigh about 54 kgs and the board will have edfs, (not possible to calculate their weight obviously) a wooden skateboard deck (about 2kg), a bike battery (about 10kg probably) and possibly a gyroscope for stability and remote control technology. (total maybe 16kg give or take, total weight excluding fans is around 70 kg will need 75kg for good lift)
I’d say divide your total lift by four and then look into EDFs from there. I wish I could help more but I just am not aware of people being able to do something like this with EDFs as they aren’t optimised for static thrust. One thing you could try is what Jlaser video did with his iron man suit where he used many EDFs clumped together rather than two.
 

Piotrsko

Master member
I think edfs spool up too slow to react fast. Perhaps doubling for overpower is the solution. This is an upside down pendulum so it's inherently unstable. You'll need to either predict the thrust requirements or react with major thrust variations bigger than the moment arms, although momentary. Thought someone somewhere was trying this, and successful (ish) but my google foo is weak lately.