Hoverboard Product Manager Position

[HoverBoarder]

This would be a great position working for Coke Zero marketing for someone who has over 5 years of experience as a Product Manager or advanced dual degree in Marketing and Engineering.

Experience working with hoverboards is not needed. As long as you have the marketing and engineering experience that is needed for this position, you could take any of the dozen or so successful hoverboard models and plans that have been made thus far, make a few modifications to increase efficiency and reduce noise, slap a Coke Zero label on it, and that’s it.

Designing a hoverboard that works will not be the issue. There are already a number of companies out there that sell working hoverboards today. The problem is that these models are too noisy, and impractical for everyday use. The key to producing a profitable consumer ready project will be how they address these critical design issues.

I have however been working on hoverboard designs for over the last five years, and I am hoping to be involved as a contributing designer. I have come up with a number of practical real world models that focus on high efficiency, reduced noise, structural resiliency, and strong light weight materials. With the help of other potential engineers on this project we could identify a few key models and get a product ready for production within the next 1-2 years.

Click on the link below for more information on this position:

http://thehoverboardprogram.com/



Job Description
The Product Manager is responsible for the product planning and execution throughout the Hoverboard product lifecycle, including:
• Gathering and prioritizing product.
• Stakeholder and customer requirements.
• Defining a clear product vision.
• Working closely with partnered firms to ensure functional design and customer satisfaction goals are met.

Required experience and knowledge:
1. Minimum of 5 years experience as a Product Manager or advanced dual degree in Marketing and Engineering.
2. Strong enthusiasm in defining and launching excellent products.
3. Design-thinking approach.
4. Excellent written and verbal communication skills.
5. Bachelor's degree (MBA preferred).
6. Technical and marketing entrepreneurial background, with experience developing consumer products.
7. Excellent teamwork skills and ability to sled manage.
8. Proven ability to influence cross-functional teams without formal authority.
9. Must be able to travel 20% of the time.
10. Strong IT skills, particular in team distance collaborative technology.

Additional information:

The Hoverboard Program is part of the virtual start-up NFSF.
NFSF was founded by Stafford Green, head of the Coca-Cola Content Factory (Paris, France) and Andy Sandoz, Creative Director for the Work Club agency (London, England) in 2010.
The Hoverboard Program is angel-funded by a start-up grant from Coca-Cola Zero.

This is a 12 month contract part-time position.
Building the Hoverboard is a lead responsibility; assignment also includes additional roles for content creation for Coca-Cola Content Factory Team. This includes documentary of Hoverboard development as well as other engineer-centric marketing responsibilities.

Salary: $40'000 - $70'000 (USD) depending on experience.

[neptronix]

is this a joke?

[Jeremy Harris]

I'm not sure.

I remember going through the basic power calculations for a project like this some time ago and concluding that the weight of the batteries was going to make an electric hoverboard impractical, at least for anything over a few minutes run time.

Hovercraft are really fun machines, but incredibly power-hungry for the performance they give, which is a real issue if you want to build an electric one.

Jeremy

[liveforphysics]

is this a joke?

No. You do the imaginary work, and you get paid with monopoly money.

I'm not sure.

I remember going through the basic power calculations for a project like this some time ago and concluding that the weight of the batteries was going to make an electric hoverboard impractical, at least for anything over a few minutes run time.

Hovercraft are really fun machines, but incredibly power-hungry for the performance they give, which is a real issue if you want to build an electric one.

Jeremy

Silly Jeremy and your energy concerns, task #1 for the project manager is to create this perpetual motion device he proposed:

viewtopic.php?f=41&t=25305

Then your energy needs are solved! Along with the rest of the worlds energy needs, but you don't want to waste it on a little thing like that, you want to use it to help sell diet coke.

[liveforphysics]

You can get plans for them on the same page with plans for making your own jetpack, flying saucers, perpetual motion energy, and starwars lightsaber props.


http://www.futurehorizons.net/hoverboard.htm



As far as making real hovercrafts (as in a machine riding on a ground-conforming bag of air to conform to the ground close enough to leave even space for an air-bearing gap), we actually have a hovercraft racing expert on this board. And his hovercraft hauls ass. If I'm remembering correctly, he said it uses a pair (or maybe 3? or just 1?) of very lightweight 40bhp rotax engines.

[Hillhater]

Coke must be one of the least ethical companies to take a dollar from !

[HoverBoarder]

is this a joke?

Not joking at all.

You are not going to ever have a hoverboard that looks anything like the science fiction models shown in the movies, but personal hovercraft type hoverboard models have been around for awhile.

The two working hovercraft type hoverboards on the market today both use gas powered engines. However, the "Airboard" from Arbortech is the only serious hovercraft type hoverboard on the market right now:



http://www.arbortech.com.au/view/airboard/

Here are the specs from the site:

Easy to Ride
The Airboard has an electric start. Simply start it up, hop on board, adjust the throttle and away you go. By using varying degrees of weight transfer, the Airboard can be made to respond in different ways - sharp or slow turns, 360º turns and sliding turns are all possible. As your skills increase so does the range of exciting manoeuvres you can perform.
The Airboard accelerates quickly to a top speed of 25 kph (15 mph).

Easy to Control
There are two levers on the handle bar - One for lift (engine speed) and one for thrust. By leaning back a small thrust wheel at the rear of the vehicle can be brought into contact with the ground to assist acceleration. When flying the rider simply leans to the left to turn to the left, leans to the right to turn to the right. Stopping is attained by either a sharp turn or letting go of the controls.

Easy to Maintain
The four stroke petrol engine is manufacture by one of the world's largest manufacturers and needs only periodic maintenance. All wearing components, such as filters and friction pads, are easily serviced by the user.

The Airboard can be used any firm reasonably level surface such as mown grass, asphalt, pavement etc., or any packed dense surface that is free of stones and litter. The Airboard is not suitable for use on water!

Ideal for beginners & skilled riders (OVER 14 YEARS OF AGE)

SPECIFICATIONS
Dimensions:
Diameter:___________________________1650 mm (5 ft 4ins)
Height incl.handle:___________________1200 mm (4 ft 0 ins)
Deck height:_________________________300 mm (1ft 0 ins)
Weight approximately :________________70kg (152 lb)
Control & Performance
Top speed:___________________________25km/h (15mph) subject to conditions
Incline/ascent:_______________________30 degrees
Steering:____________________________weight shift
Braking:_____________________________Brake lever- cuts throttle and expels air
Hand Controls:_______________________Brake, clutch
Lift Controls:________________________Throttle lever
Emergency Cut-off:__________________safety lanyard to engine kill switch
Maximum obstacle height:____________40mm (1-1/2 ins)
Stopping distance approximately:_____6m at 25km/h
Operating Surfaces:_________________Firm mowed grass, hard asphalt, concrete
General:
Total payload, incl. rider:____________120kg (260Ib)
Operating time:____________________1.5 hours on full tank of fuel
Construction:______________________Roto-moulded Metallocine LDPE square tubular chassis
Finish colour:______________________Variable- most primary colours
Starting:__________________________Electric key-start, Battery included
Engine:___________________________Briggs & Stratton 4-stroke
Fuel tank capacity:_________________5 litre (1.3 US gal)
Fuel type:_________________________Use clean, lead-free gasoline with a minimum of 85 Octane
Approx. shipping weight:___________150kg (330 lb) incl. shipping package

Approx. shipping package size 740mm H x 1800mm W x 1800mm L (30 ins H x 6 ft W x 6ft L)


The Airboard is a pretty good model. It has made a lot of advances as a pioneer of the field and it's leaps and bounds ahead of the competitors.

Still, it does have some weaknesses in noise levels, limited control, and limited areas of use.
http://www.youtube.com/watch?v=P_-PQdrgw2A&feature=fvwrel


The other board is the "hoverboard" from Future Horizons. It seems to be the only actually functioning item on the site. Although incredibly loud and funky looking, it is lighter than the airboard.
http://www.futurehorizons.net/hoverboard.htm



For hovercrafts this small, efficiency is the primary factor. Basically governed by fan efficiency, skirt performance which could also be called air leakage, fuel levels or battery operating time, and weight.

One of the things I have been working on is a drastically different kind of skirt design that could majorly reduce air leakage, and would also work best on the small platform size of a hoverboard. This could reduce the fuel usage, required motor power, weight, and cost of the board. I have also been looking into calculating the ideal fan type for this application with the best resource by far being the Fan Handbook: Selection, application, and design by Frank P. Bleier.

A centrifugal fan may not be the ideal fan choice for this application. In addition to the high level of static pressure that is needed to lift a board this size, there is also the system resistance which can act the same as static pressure, and "turbulent" air flow which is also a key factor of major losses of efficiency in high air volume fans. Two stage axial fans have a unique design that can actually mostly counteract turbulent air flow without guiding vanes and withstand static pressure ranges of 4WC to 18WC compared to 0-1 for propeller fans, 1-2 for tubeaxial fans, and 1-9 for single stage vaneaxial fans. If a two-stage axial fan was combined with a S-tipped airfoil fan blade, than this fan could have a high performance at the ideal static pressure ranges of the hoverboard with a large reduction in the noise levels due to the S-shaped blade.

My current design would use electric motors and LiPo batteries (possibly A123) with a battery life of about 1 to 1.5 hours. This calculation is based on the "Hovercraft lift calculator" from HoverHawk.com http://www.hoverhawk.com/lcalc.html

My design is much more in line with the model made by Eddie Edward’s shown below.


http://www.designnews.com/article/12790-Eddie_s_Big_Challenge_Ground_Effect_Turbulence.php

Here are the design notes for Eddie's "Hovaboard"

Hovaboard – Construction Guide
Attach the spacer boards to the top board; this will form a plenum chamber.
The fan, motor controller and batteries are mounted to the bottom board, so that the fan system can be wired up and tested before assembly.
Once the fan system is tested the top board and bottom board can be brought together to form the hovercraft plenum chamber.
The segmented skirt attaches between the top and bottom board, to channel the air from the chamber under the board. And there you have it, as simple as that!!!???
It is a good idea to build an in emergency cut-out to the motor controller to stop the fan if the rider falls off the board.
Hovaboard – Parts List
1 x Top board Aluminium honeycomb composite
1 x Base board Aluminium honeycomb composite
4 x Spacer boards Aluminium honeycomb composite
1 x Centrifugal fan – Similar to -
Mfr.'s Part #:
R2E225-BE51-09
Allied Stock #:
600-2225
Manufacturer:
EBM, INDUSTRIES
Description:
Backward Curve AC Impeller CFM710
1 x 48V power system (Lithium Ion)
1 x Motor controller
1 x Segmented hovercraft skirt (rubberised nylon)
Assorted nuts, bolts, cables and connectors.

[Jeremy Harris]

I wish you the best of luck, but still feel that it will be a heck of a struggle to get a useful operating time from an electric hovercraft, of any type

As I'm sure you know, there is a "sweet spot" when it comes to lift efficiency, governed by mass, peripheral length and area. Round hovercraft have least peripheral length for air leakage per unit area, large areas make for low cushion pressure and so lower air escape velocity from the periphery and this leads to lower cushion mass flow rates.

Small hovercraft like these are inherently inefficient, as they always have to operate at much higher cushion pressures, and so accept much greater peripheral flow rates, than larger craft.

The biggest challenge comes from a simple comparison of energy requirements though. Take the Arbortech machine as an example. It carries 5 litres of fuel and operates for a claimed 1.5 hours. It's a relatively well optimised design for a small hovercraft, being round and having a very small peripheral air gap. 5 litres of petrol (gasoline) stores around 170MJ of energy. The Briggs and Stratton engine it uses can convert around 25% of that into useful work, so we know that 1.5 hours of operation requires around 43MJ of energy delivered by the motor.

An electric motor and controller will be around 85% efficient, so for the same 1.5 hours operating time the battery pack would need to store around 50MJ of energy. The very best lithium batteries available have an energy density of less than 1MJ per kilogram, but for longevity you can only use around 80% of their theoretical capacity, so the usable energy density comes down to around 0.8MJ per kg or less. This means that to get 1.5 hours run time from a hovercraft with the same sort of performance and efficiency as the Arbortech one you need around 62kg of lithium batteries, plus the weight of the motor, battery management system and controller. You're probably looking at around 70kg plus for the power system weight.

The B&S motor, complete with full fuel tank, weighs around 22 to 25kg, so the electric propulsion system is going to be over three times that weight. The increase in weight will substantially increase the cushion power requirement, so driving the weight of the battery pack up further, which will then increase the cushion power even more, etc, etc.

It looks like you could get a run time of around 20 to 30 minutes from an electrically powered hovercraft of this size, but any longer is going to quickly push you into the law of diminishing returns. Increasing the hull area would allow an increase in weight with only a small impact on cushion power, but the optimum hull area, in terms of lift power requirement, for a single person hovercraft is probably at least three to four times the size of that Arbortech product, which gets away from the compact design you seem to be aiming for.

The laws of physics can be damned inconvenient when you're trying to do something like this.

Jeremy

[Hillhater]

not exactly new news this.
Those Airboard personal hovercraft we used for the opening ceremony of the Sydney Olympics in 2000 ...11 yrs ago. !

[katou]

I built a hovercraft back in highschool. Full size for one person, lift only.

Massive problems with hovercraft:

huge power requirements to get ANY maneuverability, and those motors have to be super light. ($$$)
roads are CROWNED, so you slide off (downhill) towards the curb constantly.
Can't turn on a dime. Can't turn on a swimming pool for the most part.
zero traction for hills
high tendency to "dig in" if the skirt contacts the ground in a fast turn.

In the right situation, they are fun, no doubt. But as a reliable, sensible transportation option, you'd be better off with pretty much anything else.

Just my opinion. I wish you luck though, it would be awesome if you could get a real 3ft hoverheight and bank for turns.

[HoverBoarder]

not exactly new news this.
Those Airboard personal hovercraft we used for the opening ceremony of the Sydney Olympics in 2000 ...11 yrs ago. !

Sure, the Arbortech Airboard is not new news, but this is:

Hoverboard Product Manager Position...
The Hoverboard Program is angel-funded by a start-up grant from Coca-Cola Zero.

I put in the information from Arbortech as an example that you wouldn't have to reinvent the wheel for this position. There are plenty of designs that work, and some key improvements could produce a far better product. This could be fairly easy for someone who has the qualifications.

I am still going to continue to work on my designs whether I help as a contributing designer with this project or not, but it does sound like a good opportunity to collaborate with other designers to improve my designs as well as the capital to properly build and test various models.

[jimw1960]

Although not practical as a transportation mode, I could see maketing them as sort of a novelty carnival ride attraction. Kind of like the racing go-cart rentals at the Malibu Grand Prix that we have here in Texas. You could charge by the ride at amusement parts, fairgrounds, rodeos, carnivals, and similar special events. Fun for the whole family. Crash them into eachother like bumper cars--that sort of thing. That would also be a great place for displaying the coke zero logo and maybe giving out free samples. Do I get the job?

[Jeremy Harris]

There are plenty of designs that work, and some key improvements could produce a far better product. This could be fairly easy for someone who has the qualifications.

I admire your enthusiasm and wish you luck, but have to question the last sentence above. From my reasonable knowledge of hovercraft (I built one when I was still at school), the mathematics that describe the power required to generate lift and the current state of the art of battery technology I really do think this is going to be a hell of a tough project to pull off.

You may be able to build a hovercraft that works for around 20 - 30 mins or so on a charge, but I'd guess that even then the price of the required battery pack is going to give you marketing problems. Even for 20 to 30 minutes or so run time you're looking at a battery pack of around 5 to 6kWh as a minimum, which is going to cost a lot of money (probably around $3000 to $3500) and need replacing fairly often if the craft is used a lot, as the cycle life will likely be only a few hundred cycles at the fairly continuous 3C discharge rate. This will make ownership cost high and present another marketing stumbling block to overcome.

Switching to a larger platform size would increase efficiency a great deal and would make the project more viable, but I guess the attraction comes, in part, from the small size.

Jeremy

[HoverBoarder]

I'm not sure.

I remember going through the basic power calculations for a project like this some time ago and concluding that the weight of the batteries was going to make an electric hoverboard impractical, at least for anything over a few minutes run time.

Hovercraft are really fun machines, but incredibly power-hungry for the performance they give, which is a real issue if you want to build an electric one.

Jeremy

An electric motor and controller will be around 85% efficient, so for the same 1.5 hours operating time the battery pack would need to store around 50MJ of energy. The very best lithium batteries available have an energy density of less than 1MJ per kilogram, but for longevity you can only use around 80% of their theoretical capacity, so the usable energy density comes down to around 0.8MJ per kg or less. This means that to get 1.5 hours run time from a hovercraft with the same sort of performance and efficiency as the Arbortech one you need around 62kg of lithium batteries, plus the weight of the motor, battery management system and controller. You're probably looking at around 70kg plus for the power system weight.

The B&S motor, complete with full fuel tank, weighs around 22 to 25kg, so the electric propulsion system is going to be over three times that weight. The increase in weight will substantially increase the cushion power requirement, so driving the weight of the battery pack up further, which will then increase the cushion power even more, etc, etc.

It looks like you could get a run time of around 20 to 30 minutes from an electrically powered hovercraft of this size, but any longer is going to quickly push you into the law of diminishing returns. Increasing the hull area would allow an increase in weight with only a small impact on cushion power, but the optimum hull area, in terms of lift power requirement, for a single person hovercraft is probably at least three to four times the size of that Arbortech product, which gets away from the compact design you seem to be aiming for.

Hi Jeremy,

I appreciate your post, and especially your detail on electric motors. Your posts a while back were very helpful, and caused me to do a lot more research on fan selection, which could turn out to help provide a large boost to efficiency. However, I don't think you are correct on your calculation that an electric hoverboard would "run a few minutes."

I also think you may not be correct on your assumption of a 20-30 minute runtime for an electric model as shown above (although I very much appreciate you taking the time to calculate this out). A standard 200AH 14.8v battery would weigh 18.66 kg, and a 400AH 14.8v battery would weigh 37.32 kg, but my calculations did not come anywhere close to needing a 74.64 kg 800AH 14.8v battery as you described above. http://www.all-battery.com/148volt-20ahheavydutyli-polypackwithpcbcustomize.aspx

I started to base my calcs off of the Hoverhawk "Hovercraft Lift Calculator," but I have found some more detailed calcs in the Theory and Design of Air Cushion Vehicles.

You have some good comments on the efficiency of air loss using a round platform. I would like to look more into this later.

I very much appreciate your response, and will post more after I get out of work.

Take care.

[Jeremy Harris]

Be aware that the lift calculator on the Hoverhawk site makes some assumptions that are based on "normal" sized recreational craft with cushion pressures that are much lower than those that would apply to a very small area, high mass craft. When trying to use on line resources it's worth remembering that these may all have been optimised for the typical cushion pressure found on recreational and commercial hovercraft, typically around 10lbs/ft². Once you get to around 15lbs/ft² you start to run into axial fan blade loading problems and if you go higher than around 20lbs/ft² you may well have to switch to a centrifugal fan in order to get the required pressure rise without encountering blade stall. Your craft looks as if it may well be over 20lbs/ft² cushion pressure, which is going to cause considerable loss of efficiency and high mass flow rates through the hover gap no matter what you do. As the skirt deforms over small obstacles a cushion that is running at this high a pressure will leak more air than one running at a more conventional pressure, as any skirt will become less flexible as cushion pressure increases, just like a tyre.

Another issue associated with high cushion pressure that you may need to look at carefully is skirt bounce. This plagued early bag skirt hovercraft that were operating at high'ish skirt pressures and was only really ameliorated by adding fingers. The problem with finger skirts is that although they are nice and stable and will pass over obstacles well they leak more air so need more lift power. The most successful bag skirt craft around are probably the Sevtec range. They get good stability and a low lift power requirement from running at a very low cushion pressure, but this isn't an option for a small area craft.

You really need to go back to first principles to calculate mass flow rate and pressure, then look at the complex interaction of varying flow rates on fan performance curves to try and get a feel for the power requirement with different fan types over the range of anticipated operating conditions (fans have a tough time with variable loading in a hovercraft). This will then give you a realistic estimate of power required and hence battery size. What you'll find, I'm sure, is that the true power requirement will be much, much higher than the simple on line calculators might suggest. An acquaintance of mine, Ian Brooks, wrote the attached paper that may help you. It applies to the sort of craft you're looking at, an integrated one where lift and thrust are provided by the same power source, except he looks in more detail at a separate thrust duct system, which you may or may not wish to consider:

estimating thrust and lift performance Rev D.pdf

(737.39 KiB) Downloaded 75 times

.

Jeremy

[Ypedal]

All-Battery = Fail...

try www.hobbyking.com and go with high C rate lipo, an Agni95 motor on 72v, and a high quality helmet !

( would spring loaded roller arms tucked under the deck to help push up and prevent skirt dig-in be against the spirit of this machine ? it would still rely on air for propulsion, but save alot of energy with lift from tensioned arms pushing up on the deck and rolling on the ground )

[katou]

How about hidden wheels? I can guarantee a working prototype if we can make this small change.

Katou

[Lessss]

Might be interesting for lake usage.

[HAL9000v2.0]

Hi, HoverBorder,
At first this sonds like a dream job, IMHO hoverboard form "back to future" is the ultimate transport device. but then I start thinking...
Who is your target buyers? I think todays technology coldn't do more then working prototype.
I don't see any feasible product in near future therfore no profit for the investers.
"grant by Coke Zero..." sonds like moneyloundry to me. Or they just waste their money to increase tax deductions.
What I have missed?


Neodyum roads?

[Hillhater]

no profit for the investers.
"grant by Coke Zero..." sonds like moneyloundry to me.
What I have missed?

Promotional /advertising exercise ??

[Tiberius]

How about hidden wheels? I can guarantee a working prototype if we can make this small change.

Katou

I think the hoverboard spec says it has a wheel underneath for propulsion. You lean in the right way and it contacts the ground.

Actually, the real test for many of these things would be to see them operate over water. Not only does it mean hidden wheels won't work, but there are interesting effects on water, especially with high cushion pressures. It could be quite entertaining.

Jeremy posted the paper by Ian Brooks, which I would recommend too. Ian is writing about integrated craft, where one fan is used for lift and propulsion. Even if you concentrate on the lift only, it's difficult to get below about 4 hp on a practical craft.
There's more at http://www.hovercraft.org.uk including useful resources and papers in the "links and downloads" section.

I am in fact currently working on an electric lift system for a hovercraft, but I'm intending it as a hybrid, with a gas engine as the primary power source.

Nick

[HoverBoarder]

Jeremy posted the paper by Ian Brooks, which I would recommend too. Ian is writing about integrated craft, where one fan is used for lift and propulsion. Even if you concentrate on the lift only, it's difficult to get below about 4 hp on a practical craft.
There's more at http://www.hovercraft.org.uk including useful resources and papers in the "links and downloads" section.

I am in fact currently working on an electric lift system for a hovercraft, but I'm intending it as a hybrid, with a gas engine as the primary power source.

Nick

Be aware that the lift calculator on the Hoverhawk site makes some assumptions that are based on "normal" sized recreational craft with cushion pressures that are much lower than those that would apply to a very small area, high mass craft. When trying to use on line resources it's worth remembering that these may all have been optimised for the typical cushion pressure found on recreational and commercial hovercraft, typically around 10lbs/ft². Once you get to around 15lbs/ft² you start to run into axial fan blade loading problems and if you go higher than around 20lbs/ft² you may well have to switch to a centrifugal fan in order to get the required pressure rise without encountering blade stall. Your craft looks as if it may well be over 20lbs/ft² cushion pressure, which is going to cause considerable loss of efficiency and high mass flow rates through the hover gap no matter what you do. As the skirt deforms over small obstacles a cushion that is running at this high a pressure will leak more air than one running at a more conventional pressure, as any skirt will become less flexible as cushion pressure increases, just like a tyre.

Another issue associated with high cushion pressure that you may need to look at carefully is skirt bounce. This plagued early bag skirt hovercraft that were operating at high'ish skirt pressures and was only really ameliorated by adding fingers. The problem with finger skirts is that although they are nice and stable and will pass over obstacles well they leak more air so need more lift power. The most successful bag skirt craft around are probably the Sevtec range. They get good stability and a low lift power requirement from running at a very low cushion pressure, but this isn't an option for a small area craft.

You really need to go back to first principles to calculate mass flow rate and pressure, then look at the complex interaction of varying flow rates on fan performance curves to try and get a feel for the power requirement with different fan types over the range of anticipated operating conditions (fans have a tough time with variable loading in a hovercraft). This will then give you a realistic estimate of power required and hence battery size. What you'll find, I'm sure, is that the true power requirement will be much, much higher than the simple on line calculators might suggest. An acquaintance of mine, Ian Brooks, wrote the attached paper that may help you. It applies to the sort of craft you're looking at, an integrated one where lift and thrust are provided by the same power source, except he looks in more detail at a separate thrust duct system, which you may or may not wish to consider:

estimating thrust and lift performance Rev D.pdf

.

Jeremy

Hi Jeremy and Tiberius,

Thank you for your response. That was a very good paper, and I very much enjoyed reading it, although I would have to make some modifications to the calculations to fit my design. Especially with regards to the plenum chamber holes and removal of the splitter height component. Still, the main factor in all of these calculations that determines the type and power of fan that is needed is the air leakage.

That is why I think the design of a hoverboard is going to first and foremost primarily need a redesigned skirt. The design I am looking into right now would use two skirts to form two plenum chambers underneath the craft. These skirts would both be made out made out of carbon fiber panels that are approximately 3 inches wide with spring or miniature shocks on each of the panels and a flexible rope like carbon fiber bottom (perhaps made of rolled up carbon fiber twill) that would hold all of the panels together. The skirt would include the segmented panels to allow for part of the craft to go over obstacles such as rocks or curbs with reduced pressure losses.

The internal skirt would allow air in by air flaps installed on the top of the chamber which would be located under the main lift fans, and would allow for a high pressure area needed for the small size of a hoverboard. Air escaping the internal higher pressure skirt would flow into the the outer skirt area before escaping. This could possibly reduce the power needed to lift the craft, reducing the noise levels, battery capacity, and weight.

A VERY rough sketch


The main difference between a small standing one person hovercraft and the modeling of a "typical hovercraft," is the fan sizes and type of plenum chambers. Typical modern hovercraft plenum chambers look like the models shown below from with side plenum holes and a design that is well suited for large seaworthy crafts:

http://www.hovercollege.com/Industrial/Hovercraft_Body/index.htm




I think we need to give up on getting a seaworthy hoverboard, and focus on increasing the performance of a land based hovercraft type hoverboard. The worst problem with the common hovercraft plenum chamber above is that the highest pressure areas are not used for lifting the craft, they are contained in the plenum chamber inside the craft.

Thanks again for all of your posts and ideas.

[Jeremy Harris]

The French persisted with separate internal skirt systems for a few years, take a look at the Bertin Jupe skirt system, as an example (here's a video with some images of the jupes: http://www.dailymotion.com/swf/xbwted&related=0 ). The idea was that by breaking up the plenum into smaller areas, partially sealed from each other, they could gain stability and help resist bounce. The system works fairly well, but tends to eat up valuable hull area, as most of the cushion pressure is retained by the jupes, with a lower pressure in the interstitial spaces between them that doesn't significantly contribute to lift.

Rigid hinged skirt systems have been tried and are extremely wasteful of lift power, as when passing over a pebble, for example, a whole section lifts and allows air to escape rather than just the part of a flexible skirt that deforms over it. All designs moved away from rigid structures like this back in the very early days of hovercraft development, primarily for this reason.

Best stability would almost certainly come from a a segmented skirt. This would be at the cost of increased lift power though.

I think you'd be well-advised to do some reading up on the basic physics of air flow, dynamic and static pressure and the way that these interact in an open system like a hovercraft. For example, your comment "The worst problem with the common hovercraft plenum chamber above is that the highest pressure areas are not used for lifting the craft, they are contained in the plenum chamber inside the craft" reveals that you're not quite clear about the relationships that have to exist because of the laws of physics, or specifically the laws that govern the behaviour of incompressible fluids (and air is normally incompressible at the working pressures and flow rates in a hovercraft lift system).

The Australian device looks as if it uses a fairly small hover gap and so will only operate on smooth ground, with few if any irregularities or obstacles, like pebbles, gravel or even just small bumps in the surface. This will be quite limiting, as I found with my first ever attempt at getting hover-borne on an under-powered craft. We took it across the school playing field and as we crossed a small dip where a trench had been dug and filled in poorly the craft dropped to the ground, due to excessive air leakage through the gap where the old trench had been. This was with a bag skirt, but the effect with a rigid skirt would have been worse. The fix was to fit a bigger lift engine.

As Nick has already pointed out, the practical lower limit for lift power is around 4hp for normal recreational craft, or just under 3kW, but this is for a craft with a modest cushion pressure, so one that will have a much larger area than the one you're looking at building. As I've already mentioned, even a slight increase in cushion pressure will have a marked increase in the lift power required, as the relationship isn't linear.

Jeremy

[vanilla ice]

What is the purpose of this if it can't do water? Don't mean to sound negative, but honestly I'm left here wondering this.. Just for the fun of the hover feeling? A hybrid design with a wheel/wheels to help may not hurt it if that is the only goal.

[liveforphysics]

Thinking about the relationships at work, it seems the power needed will have to increase at the inverse square of board area.
On paper you could simply say you doubled the pressure ratio and cut the gap leakage in half, and now you're not using anymore power. But in practice, those things in practice don't worth that way.

If say 4m^2 board area can hover at 4kw, to go to 2m^2, the pressure has to double (a single doubling of power needs), and the leakage rate for a given gap size increases (by the root of the pressure increase, or 1/2 in this case). Once the skirt area is reduced, any surface irregularity induced gap volume causes you to leak air at a greatly accelerated rate. This should cause a resultant pressure drop, lowering the board height, in theory until it seals enough to lift again, but depending on the irregularity, it may not have the gap effected at all, and the system crashes. This means you need to scale power up to overcome the worst surface irregularity or combination of irregularities you expect to encounter and be able to safely handle. In practice, I think this means to cut platform size in half, it's going to end up needing the power to be squared. But there would be a huge number of surface and material factors that would effect this of course.

Carbon fiber flaps = ultra fail.

You want something extremely supple and light. This enables maximum surface conformity and high acceleration rates back towards the surface when pressure venting or surface flaws cause the edge to lift. I would think something like oiled or silicone impregnated silk would be a good choice for the bag material itself. But the lower edge needs to be abrasion resistant, so perhaps something like a Kevlar edge? But it would need to be woven in a way to be as minimal and flexible as possible, or it's going to cause it's own series of issues.


But still, since you're not going to go across water with it, and you're limited to smooth terrain, wouldn't the same efforts/power/energy applied to a wheeled system simply dominate it in all respects?

Is the sole purpose just to be different, even if it's worse in all respect?