Compressed Air Engine Inquiry

As a fellow student I commend your thesis topic as an area that could use more research and development. I read your post on the CR4 website and look forward to learning more about your plans for compressed air engines.

I am not an expert by any means but I have an Idea of my own that could benefit from an efficient compressed air engine. The only information I have to offer you is to look into steam powered engines. They use steam, which as you know is simply compressed water vapor. Some small steam engines are tested and ran on compressed air. For your application there are many types of steam engines, from turbines to rotary vane or piston engines to choose from, each with individual benefits and faults.

Good luck, I look forward to following your work. Please continue to post your progress on the CR4 website as I am positive there are many intelligent experienced individuals who can help.

Drew

Just info for everyone. There is such a car been trialled for more than a year or so and the company now is producing more than 100 in Italian fibreglass bodied cars here in Australia. A company, Universal Bearings Pty Ltd in Wetherill Park, in Sydney has helped R&D the project.

I suggest the search of the net will show the state of progress of the project.

my search is a bust

tell us more

Hi Eric,

Great project - keep us updated!

This probably isn't news to you, but just in case, have a look at http://www.mdi.lu/english/

It's a company in Europe that has been developing compressed air engines for cars for a few years.. not sure whether they are going to get into full production - they seem to have hit a few snags along the way.

I think their basic premise was that very highly compressed air was injected cold into a piston, then a blast of hot air injected into the piston chamber at top dead centre, which simulated the effect of an internal combustion engine without all the CO and CO2 etc and gave much more grunt than standard compressed air models. (I think they were talking about compressing the air using river flows and that sort of thing at one stage too).

But I am sure you would get some good advice and direction from them if you managed to get in contact with their engineers.

Anyway - their site will give you more useful info than me blabbing on about it.

Best of luck - Robert

Search all of CR4 for "Air Motor." You'll get a lot of hits.

Thanks everyone for the advice. Come Sunday I will give an update on my blog with some new sketch developments. With this bike I am using the least amount of parts needed to operate this motorcycle. That means no brakes! I want to keep this concept as true as it was back in the 20's.

Thanks Robert Oz! I have been trying to contact these companies for information regarding their engines but have come up empty handed. Either they are not willing to release information or no response.

If anyone who has any engineering qualifications regarding compressed air engines and is interested in answering a few questions regarding my thesis it would be appreciated.

Feel free to follow my blog as I will try and make weekly updates on my thesis and other ongoing projects.

Thanks again

Eric Stafford

Wow, I missed the sketches of the bike. I love the single sided swing arm, but the hub mounted single swing arm on the front might add too much weight. You could keep it simple and since you will be riding it on a flat track go with a minimal suspension. On the other hand, if it is the innovation of the hub mounted steering, look into the 2009 BMW K 1300R. Here is a link to their hub mounted steering front suspension.

Drew

The perfect air engine in this case may be a Tesla Disc Turbine. In last year's engineering competition at Cornell, one group of students used a Tesla Turbine to power their Mars/Moon Rover experimental platform. They used CD's as the discs and a worm gear reduction drive. It was pitted against the piston-type air motors that the other student groups built, and it placed highly.

The Tesla Turbine was also the lightest and simplest of the engines tested, and least expensive to build.

Perhaps Tesla called his disc turbine, "the greatest of my inventions", for good reason.

Here's a video playlist of their turbine in action.

http://www.youtube.com/view_play_list?p=7962DEE71EE2B4E8

Hi Blink,

I was interested in your coal to road efficiency figures.

You say the grid in the US is only about 38% efficient in transferring power. However, I understood that it is very hard - here in the UK - to get the actual power station efficiency above 35% since the steam is recycled by dumping the heat into the sea or cooling towers. Follow that with the transformer and cable losses across the nation and I cannot see 38%.

Any thoughts anyone?

Hi,

The 38% I used is the average grid efficiency, including coal, natural gas, oil, (and even hydro, etc., I believe). The figure is from the GREET (Argonne Lab) spreadsheets, which are used in as part of the process to measure the well-to-wheels efficiency of vehicles. (The well-to-wheels concept can be a little nebulous in terms of the specifics of what is included, especially at the "well" end of things [fuel used in exploration?], but I think the figures are pretty close.) The overall figure is pulled up by modern gas turbines in cogeneration, which can be close to 60% efficient, at the plant, and of course by hydro.

Even modern fluidized bed coal plants are about 33% efficient (I've read and heard from power plant operators), and lines losses are apt to be 7 percent, so half of our power (the part coming from coal) is produced at about 30% well-to-plug.

Of all the alternatives to conventional cars, electric vehicles (and range extender plug-in hybrids, like the prototype in my garage) can make sense because they allow us to use many sources for power (even though some are dirty and inefficient) and because the efficiency from plug to wheels can be very high. It is the latter which leads people to call them "zero emission," but of course they are not. Here, especially in California, the same person can decry the use of a 100-watt incandescent bulb (because it increases one's carbon footprint) but think they are being pristenely green when driving their 150,000 watt Tesla electron guzzler. (The decade-old GM EV1 consumed 190 wH per mile, whereas the Tesla consumes 310, which has to be taken as a stunningly unimpressive achievement.)

The result of "California Think" (and the fact that the Tesla CEO is on the X Prize board) has lead to the Progressive Insurance Automotive X Prize having rules rigged to make electrics like the Tesla appear far more efficient than they are, with the Tesla being rated at over 100 MPGe.

Hi Blink,

Thank you for that. I accept that the 38% may be possible if you may include the non fossil content, but this is also a bit of a deceit as the hydro and nuclear are not really part of the problem. The CHP gas - do you have much, because here in the UK it is basically only private company systems which have invested thus - is a good interim solution, since, as you say, the efficiency is a better 60%. However, we still have a good way to go to improve the efficiencies, and until fossil fuel and electricity prices can be increased to reasonable levels, then little effort will be made.

Read your own post.

You sound like a politician; don't trully inform and don't explain the sources of the little information you give (which is biased).

why do you say that little effort is being done? Have you closely followed any serious study ? Give us some numbers.

If nuclear and hydro were a major power generator there wouldn't be so much greed and envy around the world for petrol.

About your wishes of prices increase, I'm happy with that, if you pay my bills.

Yahlasit

What do you sound like

Drive by guest?

Hydro is limited & changes the local ecosystems in more than profound ways than coal.

If we can store the spent fuel, other assorted waste in your backyard & you will be working at the plant I'm all for Nukes

Ummmm, there I was doing something else and suddenly the sub-conscious reported, "you've stuffed up!!" My advice above is largely correct EXCEPT that the volume I used in the equation for a 1 ft3 compressed "box" IS NOT 1 ft3 because we should have used the uncompressed volume at the start as the volume quantity in the equation. So call 1 atmosphere 15 psi then starting volume (iso thermal compression assumed) is 1000psi/15 = 60

so previous

1.44 HP for 60 seconds is 1.44 * 60 = 90HP for 60 seconds

or say 40HP for 2.5 minutes....which is still pretty ordinary but at least potentially useful.

embarassingly yours....lucky I did not sign in first time around!

http://video.google.com/videoplay?docid=4852772472368255496#

http://www.youtube.com/watch?v=Ffl1LJ5EmiM

http://forum.xcitefun.net/airpod-prototype-2010-for-a-spin-air-powered-car-t32962.html

http://www.youtube.com/watch?v=_HE8SpDPl78&feature=related

Instead of using compressed air, why not use liquid CO₂. It is a pretty dense state of air. You might be able to get some lightweight fire extinguishers to use, but ideally you could integrate the CO₂ storage into the frame as well as the tank. I know CO₂ is a greenhouse gas so this may not be a production project, but if you get decent results with it liquid nitrogen would be the next step. But it is a great deal colder and builds up incredible pressure when trapped. I used to maintain the 2000 gallon storage tanks and we kept it liquid by keeping it cold with vacuum insulated cryotainers.

Drew

Hi Blink, nice to see you like my bike. Well actually mine is an 850 with interstate tank, dating from the change over from the combat engine. It go's "where I think". Should I find a modern one near it I'd change, but I haven't yet.

As for the top shot I have sculpture similar but call it "ART" not Design!!!!!!!!

I wish you well.

I doubt if you will have much competition if successful because nobody is going to bother with the design and development of something so inefficient unless there is a compelling reason to do so - town centre pollution being a strong one I guess.

Compressed air motors have a very good power output to weight ratio - that makes the popular for hand held air tools. But when you have to take the air supply device with you the weight of the engine/air compressor/fuel tank have to be added to the vehicle.

Or if omitted - the weight of the air storage device -obviously getting heavier for more capacity - either by an increase in size - or with thicker walls for an increase in storage pressure.

Or if to be avoided - the frequent stops to refill. Which in turn requires an infrastructure to support it - which might never come considering the lack of charging stations yet to be provided for electric vehicles by comparison being many years ahead in development - but of course here you can plug them in at home.

This analogy compares to filling your own air tank at home - which in ecological terms is highly inefficient - noisy and anti-social.

Anyway, I am sure you must have considered all this during the previous three years.

But if you proceed with your idea, you are right in getting the air engine sorted out at first - because the spin-off from a highly efficient air engine could have enormous application elsewhere. That might make a network of windfarm type air compressors a viable proposition with each home being supplied with compressed air.

Good luck.

Drop it boy, but not just because everybody says so, use your common sense, you surely know how unefficient a combustion system is (any), and you know about power losses in electric distribution, the conversion from one form of energy into another and then another will take almost all of the original potential energy and will contaminate our environment badly.

Something so robust as your bike won't run for too long on a load of air.

Even if you compressed the air to the liquefaction point, the high density of air wouldn't give you much expansion when released; and all that everybody will hear from your lips is: EUR... !!!!! because you'll run out of air before you finish the word EUREKA !!!

Yahlasit

I acknowledge that there are people who I should class as 'Knockers' but my experience is that these people, because of their educational mindset upbringing, can't "Look Outside the Square". Where would the world be if all our great scientists and innovative people held the same view of 'It Can't be Done' or being knocked down and into submission of not trying, by everyone because these creative innovators held a different belief of "I can do it"?

Below is a website where the motor is powering market forklifts and transporters in an upgraded form from the Golf Buggies that have performed successfully for many years. This motor has been fitted I believe to approximately 30 Micro Cars and a further 80 are being constructed using Italian fibre-glass shells.

Lets All be positive in our thinking and the World will be a better place.

http://www.engineair.com.au/development.htm

http://www.engineair.com.au/

Proper link Air Motor

Blink as usual comes up with reasonable calculations.

He expanded on my points about racing class structures & form/function.

In every disipline of design there are technical constraints.

You also run into budgetary issues

Just because something can be done, doesn't make it a good idea...

Ok, you are correct. Perhaps we should not encourage someone to follow a path to a dead end. But this is not for us to decide. This guy is a student doing a thesis. If done critically the result will be either the data supports the thesis or disproves it. Either way, our understanding is increased.

Now, if the thesis is along a path many have trod before caution should be given, but like I said even if the data disproves the thesis the student will come out ahead for the knowledge gained in the process.

Drew

I agree completely.

Thank you. i strongly agree. using board track racing as an example is to develop a story. Something that will draw people into the design language of how the motorcycle functions and looks. Conceptual thinking may not be the most practical way of thinking but its the only way to develop past the normal everyday functions.

Thank you to all who have responded and have given advice.

First and foremost I am a designer. So my engineering knowledge is limited. Looking at engine types like the Di Pietro motor http://www.engineair.com.au/ I was under the impression that this could be a feasible application. Unfortunately they are working out patent info at the moment and are unwilling to provide information about efficiency.

Is it even possible to use compressed air technology to generate propulsion? If so what length and speeds are we looking at?

Remember this is for a sport application. My intention is to apply this technology into racing in the hopes that it can evolve into something much bigger.

If anyone is willing to help with one on one thesis guidance it would be much appreciated.

Thank you all again

Have you done the searches?

There have been many past discussions here.

How would your designs fit into the existing racing class structure?

The links to your stuff is neat. Graphic design, more than anything.

In good design form follows function.

If you want to learn the technical aspects, it's going to take time, there is no magic bullet.

Are you saying that the speed would compress air to such a degree that it would be enough to drive your vehicle???

Be careful somebody might object the idea and reject it as nonsense, but I believe you could manage that by riding you bike as an experimental prove is better than 1000 pages of words.

If you allow me I would develop a theory of such an engine driven by airflow that could fit your bike, so you could ride and without stopping to buy gas.

Good luck!

Stan

Like you all have mentioned. The likeness of having a vehicle that can perform numerous laps at a constant speed is almost impossible. The sport would have to be minimized to like you had mentioned, 2 laps.

Again most of this is conceptual and theoretical. My hopes for this project is to design for the future hoping that technology will improve to a more usable form. the main task for us as designers is to push ideas and theory's beyond what they are capable of. Engineers step in to develop these concepts into something that is functional. In a basic sense most of our design thesis's are conceptual and not be feasible in present day. But if provided with information that supports your theory then we have the possibility of working ahead.

Stan if your willing, i would like to further discuss this with you to develop a theory that could potentially work. Please email me at stafforddesign@gmail.com

If anyone is willing to help me out as a thesis adviser that would be greatly appreciated. Again my email is stafforddesign@gmail.com

thanks for everyone's contribution!

Ive updated my blog with some more sketches and other projects i'm currently working on. http://stafforddesign.blogspot.com/

http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/comprair/comprair.htm

This is just so the thread shows up in my email, but air power will work if you charge the system for little or nothing and ideally use a liquid store.

But mechanical compression is hugely energy expensive - explore Linde columns and 'cheaper' gasses.

http://en.wikipedia.org/wiki/The_Linde_Group

http://en.wikipedia.org/wiki/Carl_von_Linde

http://en.wikipedia.org/wiki/Liquefaction_of_gases

http://en.wikipedia.org/wiki/Fractional_distillation

This will point you at the most practical gas for your "propulsion" - the dreaded CO2 (speedometer , not heart of climate change) so a PR exercise, along with the "just divert photovoltaic to less efficient use and hope no one sees the logic flaw" these things rely on.

For everyone else have a look at this and see if you can see the interesting logic.

http://www.youtube.com/watch?v=GICYKU80SQA&sns=em

I'd like your thoughts.

For everyone else have a look at this and see if you can see the interesting logic.

http://www.youtube.com/watch?v=GICYKU80SQA&sns=em

John Kanzius has died (from pneumonia, a complication of chemo treatments) so I am reluctant to speculate on his motives re the "salt water as a fuel" episode.

Back in 2007, it was (and had been) reported like this:

"Through sheer serendipity, Kanzius, a former broadcast engineer, found out something incredible -- under the right conditions, salt water can burn at incredible temperatures. With a little bit of tinkering, it might even serve as an alternative fuel for our cars in the future."

We can blame the bad reporting on clueless reporters, but Kanzius seems to have strongly supported the notion that salt water was a fuel, rather than simply saying that the energy involved was coming from his RF generator (and in turn from the wall socket, and therefore mainly coal). A reasonable person, with reasonable education, would want to find a reasonable explanation for his observations -- rather than first promote an incredible misrepresentation. A reasonable and honest person would make it clear to reporters that the energy source is the RF generator, not the salt water.

Sadly, most reporters would not "get" the fundamental and glaring distinction. Even if the energy source were more obvious, the reporting would very well be the same:

"Inventor Unlocks Secret to Running Cars on Salt Water:

Kansas City, 11/11/2209: Joe Tricki, an inventor from just outside Kansas city, has demonstrated that salt water burns. His apparatus, which uses a few metal plates submerged into this new fuel (which has been around us for so long, unrecognized!) simply "conditions or tickles" the water, he says, allowing it to release its energy. These plates are connected, amazingly, to AN ORDINARY BATTERY!!! In the true spirit of American invention, Joe has assembled a few ordinary bits of hardware into an extraordinary invention that will change the face of transportation. While Joe's main interest is simply to get this secret out to the public, he is seeking investment to do further research and to refine the process. Talks are underway with an undisclosed major car manufacturer."

In an earlier thread, I mentioned that by 6/2007:

"The inventor (?) has claimed at various times, that

1. this is something other than electrolysis

2. this is electrolysis at about 76% efficiency

3. this is electrolysis at "over unity" efficiency

4. that someone had to tell him that it might be hydrogen that is burning.

The single fact that he claims "over unity" (a term only used by perpetual motion machine promoters) makes me very very skeptical."

Here is a Wikipedia article about Kanzius. The article makes Kanzius seem like more of a straight shooter than one would think from reports like the video you linked, and presents his invention as just another electrolysis method -- just what it appeared to be in 2007. But if he were a straight shooter, why would he allow the "burning salt water" reporting? Why not make clear the fact that the energy in is less than the energy out, and that the salt water was not burning in the sense that the reports led the general population to believe.

All this would be off topic re the current discussion, except that a lot of the same thinking applies. Compressed air power is anything but inherently "green", just as making H2 from salt water is not inherently green. (Kanzius's process delivers less energy in H2 than the input energy.) Fundamentally, we need to use less energy, not more -- and compressed air uses more energy, not less. Compressed air vehicles are no longer used in mines, for good reasons.

No amount of "developing a story" or "drawing people into the design language of how the motorcycle functions" will change the physics of energy conversions.

Well, It seems that you are not the only one working on compression engines. Look into this french research to see if they have anything you can use.

Drew

A couric load

Well, it is french.

But this guy is a student and this might help his project. Like I said above when doing a thesis project even if you prove yourself wrong you have completed the project and learning something. Perhaps the project will inspire another student in another direction.

I do think there might be some merit to the French's idea. If that whole car weighs 200 some odd kilos the power plant must weigh much less. If the engine and drive could be installed as a regenerative system in a city bus it could be used as some additional hp during acceleration.

Drew

I know there is a compressed air bike operating in Vancouver [North van?]. it was on TV recently. I thought I had a bookmark or write up on it. can't find right now. i don't believe it ran continously on comp air, just used as a booster for the hills. [pedal bike with small electric compressor?] will try to find and forward.here are some air vehicles.

http://www.inhabitat.com/2009/10/01/top-five-air-powered-vehicles-coming-to-the-us/

sounds like fun, good luck on your project/studies

Three of the 5 "air" powered cars (in the linked article) are MDI concepts, and they have never been demonstrated to work as claimed, nor have their production schedules every been remotely close to realistic. (If they were, we would have seen thousands of taxis in Mexico City in 2002.) Tata has no plans to produce an air car.

The Magnet Air car site reads like Peswiki (the over-unit promotion site). No legitimate electric motor vendor refers to "magnet motors". All electric motors operate on magnetic principals, but "magnet motor" has a special meaning used by the over-unity (perpetual motion) community. (These motors ostensibly run without an external power source, but not one has been demonstrated to work, despite many decades of "experimentation" by promoters. They are perpetual motion machines, which simply do not work.)

The final PHEV could get to the point of being produced, but it is not air powered in any meaningful sense -- it is a plug-in hybrid... an electric car. Air is used for regen and launch assist, but these are both areas in which electric drives are far more efficient and remarkably simple to implement. My PHEV prototype has very effective regen capability, which required no real engineering or development on my part. In ordinary, somewhat conservative driving, the friction breaks never come into play.

However, for all of these and for all "air" cars, the term "air powered" is misleading (deliberately so, it would appear by some vendors). An internal combustion engine is "air powered" in the same sense that an "air car" is air powered: a fuel burns to increase air pressure, and the air pressure pushes a piston down. The fuel consumed is gasoline, typically. An "air car" also burns fuel (typically coal) to pressurize air (via a long process of energy conversions [coal to hot air, to mechanical motion, to electricity, through line losses, through voltage transforming, to mechanical, to very lossy air compression, to air storage and heat loss]) but the process is far less efficient, because of all the lossy conversions. A very tiny fraction of the original coal energy shows up at the wheels of the car.

Environmentally, "air cars" are evil incarnate (from both a resource depletion and pollution standpoint). But an "air powered" dragster would be fun, at least.

So it appears that you dismiss the usability of a strictly air propelled vehicle. Can you suggest an assist that will increase efficiency within an air powered motor? (i.e. Nitrogen, some kind of heating or cooling process?)

I have been talking to my thesis teacher and he is fully aware of the inefficiencies of air motors but has told me not to scrap the idea. Does anyone know of any assist that may give the motor added horsepower for a short sprint race (similar to a drag race) ??

Also i am still looking for a thesis adviser who will comment on my thesis. If interested please contact me at stafforddesign@gmail.com

Thank you

Hi Eric, if I just wanted to win a drag race using "air", which is a different goal altogether than 'sustainable' transport - I'd cheat.

A principal loss in expanding a gas for mechanical use, is the temperature drop. This reduces the usable pressure, so force available. (And freezes the motor)

I'd heat the "air" entering the motor - say by a wee bit of hydrogen burning.

Quite hard to spot - which also makes it quite dangerous to play with.

A lesser - not actually a cheat - is to not let the heat escape from the air during or after compression. (This loss has been extensively explored above by many.)

Insulate everything and compress (with a compressor - not by recharging from another cylinder) direct to bike storage - then go!

This way you recover nearer to the energy that the compressor used.

You will not get the same charge mass, so allow for a bigger reservoir in the design or a much higher pressure.

Insulate the pressure vessel; build the compressor into the vessel with an intake tube open to the atmosphere. ???

Never let reality stand in the way of good design

"build the compressor into the vessel" You can; and avoid heat loss in a connecting line - (and you'd have a 'plug-in' - the current rage among tunnel vision academics - bike ) - but it's more weight and you want maximum volume in the vessel (including lines at pressure).

If you want to win - every gram counts! Every milliliter counts!

"Insulate the pressure vessel" - Explore carbon fiber wound pressure vessels. AKA accumulators (less the bladder).

Carbon fiber vessels are lighter, poorer conductors of heat than alloy or steel and less thermal mass (to heat up). But be aware the max temp for the resin is low by comparison to steel.

"an intake tube open to the atmosphere. ???" - yes, a way for air to get into the compressor would be advantageous.

But if this is asking "should I heat the compressor intake air" No.

Your PV/T target here is; ambient T air in and ambient T air out.

Inevitably your 'exhaust' will be below ambient from the charge heating the hardware and radiation/conduction losses. But if you preheat the intake air you just reduce the charge volume - so stored energy capacity.

It's time for a bit of math, physics and an Excel session - yes?

"Design" is not just "styling"

Wasn't really 'asking' anything -- really a tongue-in-cheek comment. Regenerative braking can also be used to slow vehicle, but that's another problem to solve if the compressor is located inside a high-pressure vessel.

There's plenty of problems with making air-powered vehicles practical and efficient.

My inclination would be to accept the losses and go for a 1/4 mile drag bike, in which a compressed air bike could do well.

I attended a "green" motorsports conference not long ago. While such efforts (e.g., using ethanol as a fuel) are worthwhile, they skirt the issue that racing is fundamentally wasteful -- but in my view, at least, that is OK. I've spent plenty of time racing, flying aerobatics, etc, fun pursuits that consume large amounts of fuel while going nowhere... but in the overall scheme of things, the waste is small -- not remotely close to driving a Suburban everywhere, for example. The key thing, I think, is to be intellectually honest about it -- some of the conference attendees and presenters tried to sound as if they were out to save the planet -- which they are not. Mainly, they are racing either to have fun or to provide exposure for sponsors.

"racing is fundamentally wasteful" I guess on the face value of the activity. But aside from War, 'racing' of one kind or another is a major mover in technology evolution.

Schneider Trophy to Space race. Do not feel guilty - I don't.

I the forums advice and decided to make the sport a 1/4 mile race bike. I'm detailing my project at the moment and i'm having trouble identifying and figuring out some of the math involved. I have located the motor within the rear hub for direct energy transfer. I plan on heating the air tanks and insulating them to retain heat. I was planning on using two standard 3000psi scuba tank that are about 7.5 inches wide by 17 long. Now that i'm trying to design an exterior shell for these tanks i'm finding the tank to wide. i would preferably like to use two smaller tanks if possible. Is it possible to use smaller tanks? What size?

My intentions with this bike is to make it go as fast as it can down a quarter mile track. The bike will be constructed of all aluminum and carbon fiber materials. so weight shouldn't be a problem.

I was wondering if you could direct me in how i could crunch some of these numbers. Thanks again for all of your held so far. i can be contacted at stafforddesign@gmail.com

stafforddesign.blogspot.com is my blog website the first image is an updated sketch of the bike

Cheers

Eric Stafford

I don't see a tank in the sketch

Is this the right one?

yes thats the sketch. The tanks are encased within a protective casing as seen in the sketch. To help visualize the tank arrangement i have constructed a quick model to get a sense of dimension.

Given most bikes are quite thick between the knees 12 - 16+", 7.5" should fit easily. 17" high sounds like a 40 cf, Y/N ?

Numbers wise, less tanks is less manifolding, less pipe length, less line loss = better mass flow = better power transfer = better system output = speed.

I'd be inclined to go for a 80 cf, and re-look at the riser to the yoke and the steering geometry, and the rear swing-arm length/pivot relation ship whilst there.

You need to have a hard look at weight distribution and line of drive (vector to the rear wheel tyre contact patch) including the rider mass and C of G (you can take this as 3 - 4" in front of the belly button in a lay on the tank drag racing posture)

You want a line of drive 45⁰ max to 30⁰ min (mounted). Or less than 30 for the naked bike. I.e. the tank/s are the major weight = engine, so forward and 'not too high'

Use the space to the front wheel (closing the gap will improve aerodynamics - see Moto GP bike fairing approach)

The fork lead you have will make the bike un-steerable at speed - good I guess in a straight line - presuming it's on the right line. See if you can get the lead and headstock numbers for say a Honda 996 then go a degree or two 'flatter'.

Do not go for the Moto GP or Super bike numbers - they are steeper (nearer unstable design) for snappy turning.

Shorten the trailing arm. Twist in this is fatal to handling and stability.

Or the form you have is arguing with the function you have now chosen.

There is an elegance in good functional approach - don't let 'styling' fight it.

Patently you dislike doing "sums" - but if you want this to succeed and to live: Do them!

(I'd go 2 x 80 cf)

(I'd go 'hot fill' - not heating - can't lose too much in 25 seconds go to woe.)

A very good answer and very good advice. Also consider the profile of the mounted tires when thinking of handling. You want a smooth curve without a sharp corner in the center. The sharper profile leads to faster turn in and a less predictable/control-able cornering. You don't want fast turn in on a quarter mile bike.

Thank the OP for keeping this thread going by updating with your progress!

I look forward to further devlopments.

Drew

If you suggest a hot fill, approximately what temperatures are we looking at? and approximately what speeds could this potentially achieve?

I guess from that you are being told big hot numbers on compression alone.

Time is a factor here, so you will have losses. You may desperately need losses.

As if you exceed the temperature the vessel can tolerate by quickly filling to a high pressure it will fail in spectacular fashion. You need to know this temp and monitor the vessel temp.

On compression alone anywhere from not much to 5,000 degrees C

Or you have asked me a question without the data needed to answer you.

Your temperature is P₁*V₁/T₁ = P₂*V₂/T₂

P1 = ambient at compressor intake ~ 1atm

V1 = however cubic whatever's of free air you intend to compress or intend to exhaust.

T1 = degrees Kelvin of that air at the compressor intake

P2 = the end pressure in your cylinder/s

V2 = the volume of said cylinders (and any piping or manifolding vols at system charge pressure)

T2 = is how hot (in Kelvin) the air in the cylinder would be assuming a fully adiabatic process.

I like to call the above Charlie Boyle's Law, as Mr Charles did one bit and Mr Boyle did the other - but the real name is The Universal Law of Gasses

Best to see someone in Physics and Mech Eng, ask them to look at the gear you intend to use and for advice on temperature and which type/size of compressor.

Good practice for a job in design situation too.

Looking at your concept drawings, it appears that you are using a chain type drive to the rear wheel. It would be prudent to eliminate all types of power sapping transmission, Driven Sprocket, Chain, Drive Sprocket and its shaft bearings and the bearing of the motor would also act as the rear axle if you place the drive motor within the rear wheel which would also reduce mass of framework to control the axle of the rear wheel. Just a thought as air motors produce high torque at lower rpm.

This is the latest concept. i have taken everyones advice and located the motor within the rear wheel.

Hi Eric,

Sorry to be so slow in getting back to you.

Your design looks nice, but appears to have the wrong steering geometry for stability. The two factors you should look into are rake and trail. There's loads of info on the web re the effect of these, but as a start you would want rake (angle from vertical of the steering axis) of about 28 degrees, and trail of about 4". This will give you handling slower than the typical sport bike. Just search for "rake and trail" and you will find zillions of articles.

You should be able to get the weight down to 250 lb, if your tanks are light, and if there is no battery, lights etc, etc. Total weight with 170 lb rider would then be 420 lb. With that weight, you'd need about 100 hp for a reasonably fast run (10 secondish).

Thus your air storage requirement would be 1000 hp-seconds (or about 750 kilowatt seconds). Look at 100 hp pneumatic motors for air consumption at various pressures to determine tank size. With a transmission-less motor, you will have very high torque at first and then less and less at you move down the track. You will therefore want a means for regulating pressure to keep torque at a level that is controllable at the beginning and to leave air for the end.

As you design this you may find that your tank needs to be larger, and that therefore the bike is heavier... and that therefore you need more air... making the tank bigger yet, etc. A certain amount of iteration is required.

Finding a lightweight 100 hp pneumatic motor may be tricky -- but that's what GlobalSpec is for.

Incidentally, within the mechanical limits of the motor, hp is proportional to the product of pressure and flow, with pressure translating to torque and flow translating to rpm. Look at the specs of several motors to get the feel for these trade-offs. If we assume your motor is 10" effective diameter at a piston or vane, and has 2 square inches of net surface to which air pressure is applied, then the force on that surface would be 1000# at 500 psi. That would be 2500 lb-in or about 200 lb-ft. If the wheel is 24" outside diameter, that translates to 200 lb tractive force. You can do the math, but that is in the ball park to accelerate your vehicle at the rate required at first, but not once aero drag starts to hold you back. But I picked numbers out of the "air". A larger reaction area or a higher pressure (and consequent faster air consumption) would change the calculation.

Here's a link to spec sheet for a 9.5 hp air motor. It is 72 lb -- far too heavy for a rear wheel, and only 1/10 the power required. It consumes loads of air. The charts will give you an idea of pressure and volume required for a motor of 1/10 the size you need. Obviously , the motor could be made lighter but the efficiency cannot be improved dramatically. This spec sheet is from Ferguson engineering, who sell air motors. Interestingly, they have a link at the bottom of their air motor page which takes you here.

Hello Everyone!

I just completed my thesis two days ago. I wanted to thank everyone for contributing to this thread. You can see the final design and model on my blog.

http://stafforddesign.blogspot.com/

comments are welcome. thanks again!

cheers

Eric stafford