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RMC1984 - n/a
16-Oct-06, 09:52 AM
Ive been doing a bit of research into plans for an electric powered hovercraft...



I think it is do-able. the limiting factor on the system is batteries.



Ive found an electric motor, the Lynch LC170-127 which will hit a max of 120RPM per volt, and at 48v that will max at 5760RPM, which should be enough. The starting torque will be plenty, and power to weight is amazing at 8.2Kgs.



The batteries, as i said, will be the limiting factor. They are really pricy, a 12v deep cycle battery cost upto 300, and id need at least 4. With a mordern motor controller you can operate regen braking, which when the motor slows, the excess current is returned to the battery, effectively charging it, but to a limited effect.



The initial cost would be much greater than even a 4stroke engine, but it would be nearly silent apart from fan noise, the power to weight would be enormous and the response from an electric motor is almost instant. Taking all into account, its an expensive option, with limited runtime, but would it pay off to be near silent, and economical to run?



There are other power options, such as solar cells which can give upto 50% of the required power, and charge the batts when not in use, you may never have to charge at all.



This has been very successful on boats, so why not?



What are your thoughts?

Jamie Lewendon - n/a
16-Oct-06, 11:53 AM
http://www.lemcoltd.com/lem_170.htm (www.lemcoltd.com/lem_170.htm)



the lynch website gives a power curve indicating only 7Kw (approx 9.5HP)using a current draw of nearly 200Amps at 48V.

2 issues:

1. 9.5Hp isn't even close to being enough power for an integrated craft.

2. 200Amps draw means your batteries aren't gonna last very long.



Jamie

RMC1984 - n/a
16-Oct-06, 01:27 PM
Thats true, but i think with the right investment and knowledge it could by a viable option for the future



By the sound of it you have also look into this?

Jamie Lewendon - n/a
16-Oct-06, 04:42 PM
I had a quick peak at lunchtime.

If you are interested in hovercraft, we have a local social branch that meet for dinner and a chat the 1st Thursday of the Month at the Barley Mow at Selmeston (Between Brighton and Eastbourne) if you are interested.



Jamie

Keith Oakley - n/a
16-Oct-06, 06:55 PM
We did it about 30 years ago for a demo at the Earls Court Boat Show - it took a 10bhp motor on a 3 phase supply just to lift the craft, and the length of the cable was a bit limiting.



But technology moves on.... Suggest you do a quick feasibility check by adding up the weight of your batteries plus craft and payload and dividing by the length times width of your craft. If the resulting cushion pressure is above 10-15 lbs weight for every square foot of cushion area then I'd move on...



It's unlikely to be significantly quieter - for 4 stroke F25 craft (ie roughly the horsepower your talking about) the fan is mostly noisier than the engine. Certainly the biggest advantage of the craft at Earls Court was it was noisy enough to be heard around the main hall thus drawing in a crowd to our side hall whenever it was started up.

machineage - n/a
16-Oct-06, 10:53 PM
Well - on a slight tangent... Things have moved on somewhat to the point where Electric power is now viable - if you can afford the technology that is!

Take a look at the X1 Electric car. This Li-ion powered car has a 0-60 speed of 3 seconds - and has thrashed many super cars in a straight line race. It uses a 3 phase AC induction motor powered through an inverter with a shaft output of around 236 horsepower..

Have a look at the video - quite something!



http://www.wrightspeed.com







Another car using similar technology and smart control electronics is the Tesla Sports car with a 0-60 of 4 seconds. I have to say - I wouldn't mind one of these if I had the pennies!



http://www.teslamotors.com





Chris

RMC1984 - n/a
17-Oct-06, 08:44 AM
Looking at the cost of an electric craft, compared to say a four stroke, its not even close to being a viable option. The motor i mentioned comes in at over 700...thats a seriously decent four stroke!



Batteries are around 300 each, and id need quite a few...



It could be done...with some serious investment...but i dont have it. SO heres to the good ol four stoke!

nickyd - n/a
17-Oct-06, 10:35 AM
Hi mate,



You are ideally situated if you wanted to have a go seriously with electric power. I used to work for a fuel cell company and we used high power high torque electric motors. They could wheel spin a luton truck!



Anyway, we did a lot of research into batteries and battery life and size and power issues. The best thing is they are just down the road from you in Slinfold. I'm sure they might spare you a bit of time to let you know what is out there if you ask nicely!



Nick

Don83000 - n/a
17-Oct-06, 11:16 AM
You never know you may even get them to sponsor you as it should make the TV / media so would be good cheap advertising for them probably would not hurt to take some pics with you of the craft as long as its modern and in nice nick to show them you have the basics and that its not just a pipe dream.

RMC1984 - n/a
17-Oct-06, 05:35 PM
I have not started on the craft yet, i want to explore all the option before building to suit the power plant.



Whats the name of the co you ued to work for?

nickyd - n/a
17-Oct-06, 10:52 PM
Hi,



The company was called Fuel Cell Systems when I worked there. I'm pretty sure it's now called Eneco and it's on Spring Copse Business Park.



Nick

RMC1984 - n/a
27-Oct-06, 02:00 PM
well ive fired off an email to Eneco, just a general "primer" to see if they are interested in the idea...



Hopefully they'll see its a great add oppotunity!

estragier - n/a
20-Nov-06, 03:52 PM
Perhaps it would be possible to work with a generator like Atlas is doing on their big hovercraft.

http://www.atlashovercraft.com/





Just my idee ......... If its feasable for a small aplication hovercraft thats another thing .

But i think a generator would weigh less than batery`s .



Edmond from belgium http://hovercraft.org.uk/images/icons/smiley_icons/icon_cool.gif

Sean Atterbury - n/a
21-Nov-06, 05:13 AM
Yes Yes, like a deasle electric train, the craft would need to be quite big though.



How do you spell deasle, desle, disel, deesle, desale, diesle.



Struck a blank. http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif

Don83000 - n/a
21-Nov-06, 05:39 AM
Diesel http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

Sean Atterbury - n/a
21-Nov-06, 06:15 AM
thanks

mawmaw - n/a
29-Nov-06, 08:36 AM
Hi



I'm no expert, but I had some thoughts on this myself.



The best option, in my opinion, is to have a small efficient engine/generator on board, driving electric motors for lift and drive. Weight of a small generator could be less than a bank of batteries, and a lot more reliable.



1. It does away with belts and drivetrain.



2. The drive fan could freely rotate in any direction, left, right, up or down. Reversal of thrust is also quite possible with the right controller.



3. The engine can be small, and mounted mid-craft, and as low as practical. It could in fact be a small off-the shelf generator. Small enough to sit over. Can you imagine the amount of extra space in the craft!



I'd love to try it myself, but I'm only a beginner, and should learn to walk before I run.



It'll be interesting to hear how you get on.



David

Jamie Lewendon - n/a
29-Nov-06, 11:57 AM
You are all still way off the scale. To make a reasonable hovercraft using a fan, you want in the region of 30HP minimum.

Assuming no losses in generator/motor, that equates to 22KVA.



The biggest generator you can get from machine Mart is a 6.5kva http://www.machinemart.co.uk/product.asp?p=010617115&r=2 (www.machinemart.co.uk/product.asp?p=010617115&r=2098&g=113) 098&g=113 at 1100



This uses a 13Hp engine to produce only 6.5KVA (1KW=1KVA), this gives the loss in the generator alone of 3KW (13HP = 9.7KW.

This means you would need 4 of these generators (weighing 89kg each) weighing a total of 356kg to produce your 22KW/KVA of power.



It would then be debatable whether 30HP would then be enough power in the first place to move such a beast.



Jamie

Mr No Limits - n/a
29-Nov-06, 07:21 PM
Is not toally impossible, its just a big challenge.

The lift would have to be carefully considered, ideally a seperate motor.



http://www.youtube.com/watch?v=iVN_qEtBqjg

Sean Atterbury - n/a
30-Nov-06, 05:25 AM
How about a powered welder, that is mostprob the biggest amount of power you can get out of a generator, you also mount it to a fan for lift on the other end of the drive shaft, the power created then only drives the thrust "PROP" (Big) and being that you are not always on full throttle with the thrust side, the left over power generated can either be stored in a short life battery or not used. What ever. I think these golf cart motors could work well, you get different types of motor too, high speed and lowdown torque slow motors, with some scratching around, could find one just right. Will not be that fastest craft in the land but inovetive for sure. http://hovercraft.org.uk/images/icons/smiley_icons/icon_rolleyes.gif

mawmaw - n/a
30-Nov-06, 04:59 PM
Thanks for the information on power needs and output.



So a generator is out.



What about a standard engine with multiple alternators attached?



Anybody up to the mathematics on that?!



There's a challenge.



David

jar2 - n/a
30-Nov-06, 07:45 PM
The problem is the basic overall efficency.



It goes something like this:



1. Fuel gets converted to mechanical energy - 40% efficent on a good day!



2. Mechanical energy gets converted to electrical energy - 50% efficient.



3. Electrical energy gets converted back to mechanical energy (to drive fans) - 80% efficient (ignoring controller losses, etc).



So.. only around 16% the energy contained in the fuel actually gets used to rotate the fan/prop! If you remove the electrical parts the efficiency rises to 40% - still pretty bad but a lot better than 16%.



A typical alternator can produce about 1kW (about 1.4HP) - you would need about twenty of them to drive a craft (only about 100Kg additional weight http://hovercraft.org.uk/images/icons/smiley_icons/icon_sad.gif ).



There are much more efficient electrical components available but at a serious cost (go buy a Prius and use the drive system and you will get slightly better performance).



A better solution is the all-electric system - if you can afford the high performance battery and motor of course http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif

Jeremy - n/a
30-Nov-06, 08:32 PM
" (go buy a Prius and use the drive system and you will get slightly better performance)"





The Prius motorgenerators are pretty good, they have around 95% - 98% efficiency in both directions, so could be a good choice for an internal combustion/electric drive experiment. They are pretty lightweight and compact too. Rather surprisingly, the biggest source of transmission loss in the Prius are the four gears and the HiVo chain that connect the drive to the wheels, the motorgenerator losses only make up about 21% of the total transmission loss.



The two Prius motorgenerators operating together can give about 50kW between about 1200 and 1540rpm, about 67hp. They are oil/water cooled and quite light and compact, so could form the basis for a reasonable power transmission system. They do run at 500V though and need a pretty sophisticated power control system.



Given their low operating rpm, it would be easy to match one to a big prop, so gaining a very sizeable static and low speed thrust advantage and probably gaining in prop effiency more than would be lost in energy conversion.



It would be a complex bit of engineering, but would definately be do-able, and may well lead to other advantages, such as the ability to place the internal combustion engine anywhere in the craft that was convenient, plus adding the ability to independently control thrust and lift electronically.



Not a project for the faint-hearted, or technically challenged, but certainly a possibility if you came across an accident damaged Prius at the right price (actually, I think you'd need two, as you'd want one set of bits for the motor bit and another for the generator).



BTW, the Prius has a total oil well-to-wheel energy efficiency of around 34%, compared to a conventional petrol engine car's efficiency of perhaps 24% - 26%.



Jeremy

Robert - n/a
1-Dec-06, 03:35 PM
Thanks for mentioning the South Downs Twig meetings but we will all be at the Mongolian BBQ in Brighton on Thursday 7th December. (see posting headed 'Christmas Dinner') Our Twig meetings are all the other first Thursdays, 7.30 at the Barley Mow, Selmeston!

RMC1984 - n/a
3-Dec-06, 04:21 PM
Thanks for all your thoughts. I think the using an engine to generate electricity kind of defeats the point. You still have lots of noise and the need for liquid fuel etc etc.



I was looking at it because as har as i know, its not been done before.

If it could be done well, electric motors have far greater performance in terms of accelleration etc.



If it can be done for that electric super car posted in the links above...surley it can be done for a hovercraft...to great effect.

jon_curtis - n/a
3-Dec-06, 08:09 PM
how much did the super car cost to develope?

RMC1984 - n/a
4-Dec-06, 04:29 PM
A hell of a lot...



But it WAS developed.

Jeremy - n/a
4-Dec-06, 06:59 PM
"If it can be done for that electric super car posted in the links above...surley it can be done for a hovercraft...to great effect."



It certainly could be done, but there is a significant difference in terms of continuous power requirement between a car and a hovercraft.



An electric car will have an average operating duty cycle, in terms of the percentage maximum power used per unit time, of perhaps 15% - 20%. In other words, a 100hp car probably delivers on average no more than about 15 to 20 hp over the course of an hour or two.



A hovercraft runs at a far higher duty cycle, probably around 60% - 80% of maximum power. The result is that the amount of stored energy required would be around 4 to 5 times that needed for a car with a similar maximum power output.



There are several problems that need to be overcome to get an electric power system to work in a hovercraft. Firstly, the high continuous power demand will cause the electric motors, batteries and power control systems to get hotter than they would in a car. Secondly, the battery capacity needed would have to be increased in line with the extra energy storage needed, which will add an enormous amount of weight (a 100hp battery powered electric hovercraft will need about 4 to 5 times the weight of batteries alone, compared to a similarly powered car, plus a heavier duty motor control system). As a consequence, endurance will be severely limited with present battery technology, I doubt that a practical battery powered craft could be made to run for more than a few minutes at most.



To show how big the weight penalty from batteries is, here is a rough comparison in terms of the energy per kg of "fuel", between petrol and the very best battery technology that is presently available:



Petrol will give you around 12,000 - 13,000 Watt/Hours per kg. A 100hp 4 stroke petrol engine, running at an average of 70% max power, will burn around 290 - 300g/kWH, which means that about 15 to 16kg of fuel need to be carried to give an hours endurance. A 2 stroke would need perhaps 25kg to 30kg of fuel to deliver this power for an hour



The very best lithium polymer batteries available at the moment can store about 150 - 160 Watt/Hours per kg. To run a 100hp electric motor at 70% power for one hour would mean carrying about 350kg of batteries.



As you can see, at the moment the sums just don't make a reasonable endurance battery powered hovercraft a practical proposition. Technology will no doubt improve a lot in the next few years, as a 150 W/Hr/kg LiPo battery is a heck of a lot better than the 30 W/Hr/kg lead acid battery in a milk float! Batteries do still have a very long way to go to get anywhere close to the energy storage potential of either gasoline or diesel though.

RMC1984 - n/a
29-Jan-07, 04:15 PM
Thanks for the info...



I will investigate further, even if its just a design idea.