Engineering a Steam Engine for Automotive Use. A top down approach.

Why not at least work on the steam Wankel while waiting for the Mk6? That way, you might have an excellent "Plan B" backup idea ready to go in case the Mk6 doesn't work out for some reason? Just a thought.

Peter



Edited 3 time(s). Last edit at 04/30/2013 03:33PM by Peter Brow.

The main problem with the Wankel as a steam engine is heat. Yes you can wrap the engine. but what about the rotor and crank. There is going to be heat conduction to the rotor and on to the crank. lubrication will be a problem.

Andy

Peter,
I am, don't worry. Just cannot leave it alone, just so logical and intriguing, with too many features on the plus side to ignore the Wankel; but with some serious questions on the negative side that have to be answered.
OK, I found the notebook from when George and I looked at it.
1) Supposing that the oil less seals can be used, then the question arises if they will work with water
present? Seals have always been a problem with the Wankel, unless high cost custom seals were used.
2) The compression ratio is limited and possibly not as high as one can get with a piston engine. So the
desired high compression steam expander in one stage may not be possible.
3) The Wankel is a very high speed engine, it is a very short stroke engine.
4) The Wankel's expansion ratio is not anywhere as high as you can get with a piston engine, possibly
meaning two or three stage expansion to get a low water rate.
5) Making the correct housings and rotors will be very expensive, because you have to depend on small
companies to do it for you unless you want to invest in some very expensive tooling.
All of which means that the Wankel will be a very high cost engine to develop.
The long view is that going for a piston engine might just be the wiser course. In which case the opposed piston engine offers very good mechanical and thermodynamic advantages two crankshafts notwithstanding. The F-M and Junkers engines were very high quality and well proved the advantages.

Andy,
Water lubed roller-ball bearings and a dry sump system to remove heat. The new side seals totally prevent oil from getting into the combustion chambers anyhow. Much has been done in continuing seal development and now there are seals that are very happy without any oii at all. But with steam?

As an IC engine, the heat into the rotor and then on into the bearing would dwarf what would happen as a steam engine.
Once you see what the eventual temperature will be with steam, then you can establish the running clearance between the rotor tips and the housing, unlike as an IC engine, they will stay constant and not constantly keep climbing up. Cooling and maintaining running clearances was one big development headache with the Wankel as an IC engine.

Had to find my notebook. OK, the rotor flanks do not touch the housing so good heat barrier coatings work on the rotor flanks and also inside the hollow rotor. The reduced metal content inside the rotor greatly reduces the heat transfer by conduction.
Best learning tool is to go to a wrecking yard and pick up one of the Mazda 13-B engines and tear it apart and see what goes on. Great way to understand the Wankel engine, it's fascinating; but there are considerations that must be put to rest. The list above is where George and I stopped our research.

I await the Cyclone Mk-6.

Jim



Edited 4 time(s). Last edit at 05/05/2013 12:39PM by Jim Crank.

Huh!?!

Wonder how well one of those wrecking yard Mazda engines would do in pressurizing a boiler housing...

>OK.....lit fuse.....tossed dynamite......creeping away.....<



Edited 1 time(s). Last edit at 05/03/2013 11:04AM by frustrated.

Hi Ken,

I suspect that the thru-put with the 13-B engine would be way too small for anything except a very small steam generator. NSU did set some motorcycle speed records using the Wankel as a supercharger. The pressure is there; but not the big flow rate for firing a steam generator.
George did a chart once showing the flow rate vs. gph, cannot find it now.
My fantasy GT needs some 600-800 cfm, so really for high pressure firing the compressor section of a medium sized gas turbine or a big turbocharger would be a more likely candidate.
The one pacing thing that concerns me with high pressure firing is how you would drive the blower, that takes some serious power.

Jim

Jim, I posted on some electric powered turbos a while back. With your experience on the Doble turbo bosted boiler I am wondering what you think of using them full time. They could be powered by an electric motor-generator and exhaust steam. At start up the electric motor would power them and once up to pressure the motor would be switched to generator mode and power would be from a steam turbine. Though finding a motor-generator these days may be a bit of a problem.

The last time I saw a motor-generator was on a friends small tractor.

Andy,
I don't know the specific electric turbos you are referring to.
If they are the ones for regular vehicle engines, the output is way too small for any steam generator use, not the 400-800 cfm a steamer wants.
Jim

It would be the air mass rate lbs/sec that is important. If it were a P-fired boiler the cuft/sec rate could be lower.

I was more interested in what you thought about using a motor/generator unit.

Andy,

I know what the air flow rate needs to be to fire steam generators, just cannot find George's chart of cfm vs. gallons per hour to verify some numbers.

My experience is that with the exception of the E Doble motor-generator, Doble used a Bosch custom made generator-motor in the Series E auxiliary unit, the present ones are too slow and do not have enough power for any good sized blower and are of short duty cycle as a motor unless you want a sautéed armature, only if the steamer is a really small one. Think 3/4 hp and 3600+ rpm to be of any useful size.

The old generator-motor unit was made by Delco and widely used. Lincoln Model L, a friends six cylinder 1918 Buick, etc, etc.
I seriously doubt that anything like those are made anymore, what with the huge electrical load to power all the stupid play toys they festoon cars with today, 100 amp alternators are the norm and going to 150-200 amps. I have read of thinking turning to 48 volt systems to cut down on the big cables cars have, less weight and the cost of copper.
The problem being that blower motors can take 40-80 amps at 12 volts, so my fantasy car would have a 24 volt system. The long suffering battery takes the load until the alternator gets up to speed.
Seriously and considering the loads and when they appear, I would keep the alternator and blower motor separate.
The other thing to consider is if there is an exhaust driven draft booster and what flow rate and pressure it is supposed to deliver and when does the booster take up the full load of the blower motor? Just some of the nasty but interesting things that one must know when designing a new steam car.
Firing up, I would not think you want or need any high pressure or enlarged flow rate.

Jim



Edited 2 time(s). Last edit at 05/04/2013 02:15PM by Jim Crank.

Jim,

Your last sentence is exactly what I was thinking. You wouldn't need a lot of blower output starting up. You wont to avoid thermal shock, I saw somewhere the same thing about motor-generators. That they were low power as motors.. It's true they are hard to find anymore. Search the web and all I found were gas motor generators.

Andy

All DC brushed motors are essentially generators, they are truly a "generator" when they have some sort of current regulating circuitry either built in or attached. If the motor is plated for 100 volts @ 4000 RPM. Spin it 4000 RPM and it will put out close to 100 volts. The output is almost the exact inverse as the input as a motor. Put a load across the windings and the amperage increases plus it takes more horsepower to spin it - the inverse of the input.

On my Steam Tug I'm using a 60 volt Nema 23 DC motor as a generator, at full speed (1200 ~ RPM at the generator shaft) it puts out about 5 amps, the 12 volt battery keeps the voltage constant - anything above 12 volts for the RPM input, current can be generated. To keep it from acting as a DC motor at idle, I used a diode (full wave bridge) in one lead that only allows current to travel in one direction i.e. to the battery. Of course, I wired it so at the flip of a switch I can bypass the Diode (use it as a motor) to pick up an extra half horsepower when racing, but my steamboat buddies don't know that. (they do now)

As many things are, as a generator they will not put out as much as the required voltage/current when acting as a motor for the same shaft torque (losses - resistance in windings etc).

-Ron



Edited 3 time(s). Last edit at 05/08/2013 11:48AM by IronChief.

Hi Jim,

I always had doubts about the Wankel engine for steam use, but then I thought that maybe you and George had found ways to solve the problems with it. Thanks for the additional information.

Peter



Edited 4 time(s). Last edit at 05/08/2013 03:10PM by Peter Brow.

Peter,

No, the Wankel is most certainly not abandoned. Technically it remains most fascinating.
The problem areas have received attention and are solvable. The question is one of high cost and how much time it would take to work things out to make a commercial engine.
Then even if done, so what? Doing that does not make the Wankel any more accepted along with steam cars in general and spending that much for one engine just to prove a point is just not reasonable, there has to be a market. Couple that with the general scorn and ignorance about steam cars in general does not inspire confidence. The ignorance is appalling; but definitely there.

The Cyclone is not in production and when and even if that will happen is of concern. It also means abandoning the idea that one version is the universal "fits all". That is like taking a small car engine and jamming more and more boost into it until the crankshaft blows out the bottom, when a larger version is what is called for. All that takes capital.

Otherwise keep the steam car as something to have a great deal of fun with.

Jim



Edited 1 time(s). Last edit at 05/09/2013 01:42PM by Jim Crank.

HI Guys
I seldom post unless asked a question, however the issue of the chemistry of and engine is seldom discussed. What I like about a theoretical cartoon engine is it always works. We have tested and tested so many systems and materials to make an engine work. Then all the testing for durability has to be done that takes time. To build something that will run around the block just to work on it is not the answer. That is OK for a toy but not a serious real engine to be reliable and drive something. Rusty engines with oil dripping out and spewing smoke....
Just wanted to bring this up. Stir the pot.
Harry

Good input Harry. Getting all the requirements is what this thread is about. Durability is a main one. Maintaince is also important. Modern cars go 200,000 miles with vary little maintance.

But you need to get with the modern age of design engineering.

cartoon engineering in the UK

VR cartoon design at ford.

Ford engineering center

More cartoon engine design

If it is good enough for NASA why not a steam automobile design

Jim.

In this vid the Wankel timing of an IC "four stroke" engine is described. However a steam engine is like a two stroke engine. In that vid you see a power stroke starts once on each revolution, 360 degrees, of the crank shaft. But with a steam engine you wont a power stroke starting every 180 degrees, half revolution. If you use inlet and exhaust ports you would have double the ports of an IC engine. I think using port timing would be a problem as exhaust and inlet would be overlapped. In my Wankel steam engine design I used valves. It was reversible by switching inlet and exhaust with additional valves. The port valves were rotary slide valves similar to Corliss valves. Also note that a steam Wankel would complete it's power and exhaust in only 1 1/2 revolution of the crank shaft. Not 3 like the IC version.

That description in the vid isn't quite right. In the video the demonstrator said that there is one combustion cycle per revolution. That is in a way true if you look at all chambers. A single rotor face takes 3 revolution to complete a full intake, compression, power, exhaust cycle. You have a rotor surface starting a cycle on every revolution. A steam engine having only power and exhaust would get two cycles starting every revolution. Or it should if designed right.

Andy



Edited 1 time(s). Last edit at 05/12/2013 01:53PM by steamerandy.

Hi Andy
We also use this but a real run has to run a lot of hours not until the computer crashes.... been there done that.
When I have time I will make a list of the hundreds of parts that have to be designed made and tested. It starts with making a fire ..heat.
The engine is the easy part.
Harry

Andy,

The only way to accurately know for sure how the Wankel works is to go to a wrecking yard and buy a 13-B from a Mazda, take it apart and save the side plate with the gear, the eccentric shaft and one rotor.
Now remove the original rotor seals and place it on the bench and mark one rotor tip and one point on the eccentric shaft. Now you can rotate the shaft and see for real how the engine works and where the steam ports need to be located. Funny book descriptions by people who don't know what they are looking at do not help one bit. We are not looking at the Wankel as an IC engine or wanting to use the original housing or ports.

1) The eccentric shaft turns three times for each revolution of the rotor. A two rotor Wankel is more than enough. Three rotors would be nice; but not needed.
2) Trying to get two power impulses from each flank of the rotor per revolution is not the way to go. The overlap seriously limits the expansion ratio. I would never give any consideration to that.
3) Now, place one flank of the rotor equidistant from both ends opposite the spark plug location, in other words at TDC.
4) Now rotate the rotor flank to where the displacement is at maximum. You will see it can go further than where the original exhaust port was located, more than 180 degrees opposite from the spark plug location.
The volume ratio from TDC to BDC is more than as an IC engine.
5) As an IC engine each rotor flank has a depression for combustion control. As a steam engine these are not wanted to give the highest possible compression ratio, like 14-1.
6) Obviously the poppet inlet valve gear and valves are mounted on the side of each housing right where the spark plug was located. Inlet only, exhaust is via ports. Very short inlet ports too. The inlet valves can perhaps open directly into the housings depending on the lift.
7) The new housings are cast iron and hard surfaced. No water jackets are used.
8) The rotor tips do not touch the housings, only the seals do that at each tip. There are now seals that are quite happy without oil, they run dry. The side seals can be water lubed or run dry. They never were a problem anyhow, it was the tip corner seals that failed. At least mine did at 11,000 rpm. this speed is needed as an IC engine to develop the horsepower; but not as a steam engine. Remember, as a steam engine you have total control of the BMEP by means of the inlet pressure with the throttle and with the cutoff percentage. This provides the enormous torque the steam engine will inherently give, you don't need high rpm to develop horsepower. Use the wide power band the positive displacement steam engine has.
9) The original Gleason grinders are no longer needed. The new high resolution servos available for use with vertical milling machines or with CNC machining centers can machine the housings and rotors.
10) The rotor sides do not touch the housings, so they are heat barrier coated. The entire engine is well insulated to prevent radiation losses and case distortion.
11) The shaft roller or ball bearings are water lubed and cooled with water and not oil. A dry sump system is used to dissipate the heat from the eccentric shaft bearings.

The problem is cost of having the parts machined by firms who still do Wankel work, or equipping a heavy duty mill with precision servos. Then there needs to be a reason to do this, not to just prove a point. Nothing wrong with pistons and crankshafts either. The basic thought is the the Wankel has a lot of "piston" area for its size and weight and runs as smooth as anyone could want, like an electric motor.

OK, more than enough on this Wankel business.

Jim

Ok Jim. I do know the Wankel quite well.

I can not understand why you would throw away half the power potential. Why are you wasting a power stroke.

I'm going to describe this using the IC ports and spark plug for timing only. Starting with the rotor face on the port side. The crank throw is also pointing at that side. We have min displacement. Now instead of IC ports we have the inlet port But it would be closer to center and have a valve. Following that rotor face thru 90 degrees of rotation. The crank has rotated 270 degrees and the face's chamber is at max displacement. On the spark plug side we have an exhaust port. It also is valved and offset so as to be uncovered by the rotor. at least partially. At that point the rotor has completed one power "stroke". Following the crank thru an additional 270 degrees of rotation. The rotor has rotated another 90 degrees and is again at minim displacement on the spark plug side. That face's chamber has now completed a power and exhaust "stroke in 540 degrees 1 1/2 revolutions.. At that point an inlet port on the spark plug side opens and that rotor face begins another power stroke. Rotation of 540 degrees and that rotor face is back were it started and has completed another power and exhaust stroke. Looking at the rotor face ahead of the one we followed above. Call it face A. And the one ahead face B. When face A is at the start of a power stroke, face B is in an exhaust stroke. 180 degrees of crank rotation will have face B at min displacement starting a power stroke while the rotor has rotated 60 degrees. Face A has completed 2/3 of it's power stroke. With only one rotor we have power strokes overlapping and are getting 2 power strokes starting every revolution of the crank. You really only need one rotor to have over lapping power strokes. Why on earth would anyone waste that power. When you could get twice the power out of a single rotor. Especially when power density is so vary important.

If you are going to have two rotors. Rotate the chambers 90 degrees. Crank throws at 180. Now you would have a power stroke starting every 90 degrees of crank rotation. Make it a compound and it could operate like a steeple compound.

In a Wankel we have min and max displacement at 90 degree points of crank rotation. I know this may be a bit hard to visualize. Starting with the crank pointing at the ports side. That face is at min displacement. Call this face A. The next face in the direction B and the next C. Rotation of 90 degrees, the crank throw pointing at the widest point of the chamber. The rotor has rotated 30 degrees, face A's leading rotor apex is pointing also at the widest point of the chamber. Face C is at max displacement starting it's exhaust stroke. Looking at a rotor in a second chamber. The crank throw of that chamber at 180 degrees. The chamber at 90 degrees. The rotors of both chambers are oriented the same. The face of the second rotor is at min displacement and aligned with the first rotor face at max displacement. With the chamber at 90 degrees the exhaust of the first stage is coincident with second stage inlet. And that is true in forward or reverse direction.

Also having inlet and exhaust valves lets you control expansion and compression ratios. Having compression also creates a symmetrical heat distribution. With compression to inlet pressure we have the min displacement surface exposed to higher temperatures while the max displacement surfaces are exposed to cooler steam.

Jim, What are you doing with that unused 1 1/2 revolutions? It still is going to go through a min to max to min displacement. You admit steam on the spark plug side and power stroke 3/4 of a revolution the face is at max displacement. Another 3/4 revolution exhaust. ! 1/2 revolutions of the crank. What's happing for the other 1 1/2 revolution returning that face to the spark plug side? sucking exhaust and compressing it or what. Just dead time drag?

Andy

I think the scroll expander would be a better choice.
Rolly

Andy,

It's simple. I can get all the expansion I want without having seal leakage mess up the cycle by trying to get two power strokes per rotor flank per one rotor rotation. It means moving the unaflow exhaust peripheral port.
If you read Felix Wankel's book on rotary engines, the one he assembled when he developed his version, you will see that the chamber shape that Mazda used is certainly not the only one, there are an almost infinite variety. A high compression ratio like 20-1, if you want it that high, is available and has been done. The Wankel was successfully made and run as a Diesel engine, that ought to be high enough compression for anyone.
Read Wankel's book and the big one that Jan P Noybe wrote, the variations are all spelled out.

The power density is there depending on the inlet pressure available, throttle position and cutoff percentage. Two rotors will do the job nicely as far as power impulses are concerned, although three would be frosting on the cake. Remember what the three variables do to the PV diagram and THAT combined with the BMEP are what counts. Steam engine PV diagrams are light years different than from the same engine as an IC engine.
The BMEP combined with the big "piston" area available in the Wankel give all the torque and horsepower needed for any high performance car.
The engine remains as a unaflow, no separate exhaust valve.
Cutoff controls the actual expansion from a given inlet pressure to exhaust vacuum just like any steam engine. One was so made some years ago and nicely instrumented on a dyno, the PV diagrams provided all the design criteria one would want.

That is why I suggest that anyone wishing to understand the Wankel engine go buy one from a wrecking yard and dismantle it and study the rotor and eccentric rotations and varying angles and volumes. Not to depend on a vivid imagination or waving of hand, with the information derived from faulty impressions; but from real working hardware.

OK, the subject is closed, no more debate.

Jim



Edited 1 time(s). Last edit at 05/14/2013 04:52PM by Jim Crank.

Jim I do not think you are understanding this. Take the basic automotive Mazda Wankel. It is a four cycle IC engine having inlet (270 degrees of crank rotation), compression (270 degrees), Power(270 degrees) and exhaust (270) degrees. That is 3 revolutions of the crank. That is the basic Mazda engine you suggest one looks at to understand the Wankel. What I am talking about is the inlet of the Mazda type Wankel would become a power stroke. Compression an exhaust. Power another power and exhaust an exhaust. What you seem to be proposing is that we ignore the inlet and compression of the original engine. That's like taking a piston steam engine that only admits steam every other revolution of the crank. The Mazda type Wankel naturally has two power - exhaust strokes per revolution of the rotor per face. You would have a power stroke starting every 180 degrees of crank rotation and they would overlap 90 degrees. It isn't complicated to operate a Steam Wankel this way. The valve timing is simple, one to one with the crank shaft. You would have two inlet and two exhaust. The valves are positioned 180 from each other around the case so a single eccentric or cam on the crank shaft would drive both sets of valves. This is not a debate or an argument. I am just trying to get a explanation why you are, as in the analogy to a piston engine, would run half the power exhaust cycles. It's hard to explain this in test. Maybe in table form you can see what I am talking about. All this talk of timing is confusing the question. In the table below I am showing the relation of an IC engine (piston or Wankel) cycle to a steam engine. The volume change column applies to 180 degrees of crank rotation in a piston engine and 270 degrees of crank rotation in a Wankel.

    IC        Steam    Jim's steam     Volume
              Engine      Wankel        Change
 
  intake      power     not utilized  min to max
compression  exhaust    not utilized  max to min
   power      power        Power      min to max
  exhaust    exhaust      Exhaust     max to min

Why would you not utilize the inlet and compression volume changes as power and exhaust in a steam Wankel?
That seams akin to running a Doble single acting having sealed up the ports on one end.

Andy



Edited 2 time(s). Last edit at 05/15/2013 04:00AM by steamerandy.

Andy,

When I said I was finished debating the Wankel engine I meant it.
I understand what you were talking about perfectly well, it's just that there are two killer reasons why we chose not to go with two power pulses per flank per revolution.
You need to see REAL hardware, a Mazda 13-B engine and not computer delusions. There are two very good reasons why trying to get two power impulses per flank per revolution is bad engineering. We most certainly thought of this before I got that engine and actually SAW what really goes on.

OK, drop the subject.

Jim



Edited 3 time(s). Last edit at 05/15/2013 06:00PM by Jim Crank.

"Rotary Piston Machines" Classification of Design Principles for Engines, Pumps and Compressors by Felix Wankel 1963, English edition 1965 Here is the first sentence in the Preface: "Many years of work on sealing problems and rotating piston machine layouts, including rotary internal combustion engines, has focused attention on the need to classify this type of mechanism." Later on we get this gem: "Because there is such a bewildering variety of rotary piston machines, few of which have been appraised in any detail, it was thought opportune to subject them to closer analysis, scrutinize their movements, bearing and drive arrangements, including the sealing systems of many already known and new designs." This book is just great. The last 16 pages are color schematics of every possible rotary anything known to man followed by a page of "Special Terms and Expressions Used in Conjunction with Rotary Piston Machines." One leaves after a few minutes leafing through this book with a new appreciation for the ingenuity and eternal optimism of man. It reminds me of "Valve Gears for Steam Engines" by Peabody and "Valve Gears" by Fessenden as expressions of the human creative mind. For some reason every new, and apparently some old, steam person thinks that what we need is a highly creative expander design. I suggest that sealing is difficult enough with five piston rings on a piston, as written up in the SPS/Dutcher Industries Final Report, in attempting to seal a high pressure steam engine. Also I suggest that basic geometry with a cylinder having the greatest volume to surface area of any other geometric shape that can have two parts sliding be taken into account when thinking about steam. Modern steam will progress more if we can convince the new steam people to figure out how to get a good fire going and then to modulate it instead of trying to come up with a new geometric design. Enough of them have already been invented. Tom Kimmel

I am usually smart enough to not attempt to correct Jim Crank. I must be off my feed today. The correct spelling is "Jan P. Norbye" The Wankel Engine. It is quite reasonably priced on the used book market but probably not as much fun as Wankel's book. Tom Kimmel

Hi Tom,

Right again, I misspelled his name.
About $38.00 for the hard copy on Amazon for Norbye's big book.
Wankel's book, I haven't seen a copy for sale in decades here or in England.
Talk about someone thoroughly examining every possible rotary engine known to the mind of man, there they are in spades. Possibly T.E. Warth Automotive Books, if you are lucky.

Nothing wrong with good old piston rings on pistons, always a good way to go. Just that the Wankel is so damned intriguing, that big "piston" area in such a light weight, ultra smooth and small package.
Just remember when dreaming about a steam Wankel, the rotor seal strips on Mazda's LeMans winning car cost $1200.00 for each X 6 for each rotor and then times 4 for the whole engine. Now they are not so bad; but the oil less ones are still worth their weight in gold.
By the way, found the box with those Mazda parts. Statements remain as said above earlier.
I still await the Cyclone Mk-6, I don't need another expensive engine project to just prove a point.

Hey, what do I do with the Besler steam airplane negative and good high quality print? That rotten one on U-Tube ought to be burned, someone copied the equally bad VHS copy long ago.

Jim



Edited 2 time(s). Last edit at 05/15/2013 08:29PM by Jim Crank.

Good Morning,

A number of copies of Felix Wankel's book in both English and German editions are listed as available on abebooks.com starting at $94.00 US.

Sincerely,
Jim

Correct Andy
Only you did not complete the formula for wind rersistance. It is V<2 X .004 = psfoot. For a car or a boat there are other factors such as the rolling resistance or in the case of a boat the drive train and the hull type resistance that have to be added. I have used it many times over the years and it works. This formula dies at the speed of sound as at that speed it is = 14.7 #. I am sure you have used something that you have built to prove your formulas. This formula is the same as gauge pressure. Of course it has to be multiplied X streamlining factor.
An air speedo could read this as speed@pressure. Do not blow on an air speedo as you will break it. A boat water speedo is the same only the formula for water is V<2 X.0147= psi. I think you may have over complicated this. Newton,Tesla are my heros. What is this beat up Harry. day..

This is years ago towing models of boats and ground effect machines. You had to have the right speed for the GFM or it would not fly as it operated not with an airfoil wing but on speed=pressure. I patented it and flew it over twenty years ago formulas worked then, maybe physics changed.
Have a great day

Hi Harry

Rolling resistance is typically 0.7% to 1.4% of the vehicles weight. That means it would take 0.7 lbs to 1.4 lbs to move a 1000 lb vehicle. And is the highest from the start, decreasing with speed. This mostly comes from tire deformation. The formula:

Power = a * speed³

does not include rolling resistance. Using the 1.4% a 1000 lb vehicle would need 2.24 HP over coming rolling resistance at 60 MPH. Considering a aerodynamic sports car takes around 12 HP to run at that speed. then 9.76 is over coming wind resistance and drive train losses.. Say there is 10% loss through the drive train. Then we would have 8.784 HP over coming wind resistance. Then at 120 we would have 4.48 = (2.24 * 2) to rolling resistance, 70.272 need to over come wind resistance. At 180 MPH we need 237.168 HP to over come wind resistance.

I used the highest value for street tire rolling resistance figures. Pneumatic tires which would have significant higher losses then the hard tires on a speed record car. I figured 10% mechanical friction losses to the drive train. Which should also be high.

The 0.7% to 1.4% tire rolling resistance is for common street tires. Racing tires can gave even lower. Engineering books I have figure only 3% losses to direct drive engines. Right angle drives do suffer higher losses.

Andy



Edited 1 time(s). Last edit at 05/20/2013 12:26PM by steamerandy.

Hi Andy
That is close. We do it a little closer. Using each gear, belt, and tire. Then we actually towed the vehicle. What happens is the force is a constant and the hp is increased with the rpm. We have an alternate system design that we can reduce the RR by as much as 30%. The rolling resistance is largest at low speed, as the speed increases WR becomes a much larger number. I have all of this graphed along with the amount of cutoff for the balance of water rate to the torque / RPM required.Only a few people have this information for obvious reasons. That is why there was wind tunnel testing done on the body, draw bar pull on the loaded car and complete dyno testing. This is done to make sure that all is on target.
Your numbers are pretty close. Our car is well over a thousand lbs and the RR is 3.5 hp at 60 mph. At 150 mph RR is 9 hp. The WR is the bigger number after 80 mph using our tested aero dynamics.
Thanks Andy need all the help we can get, and you were close, always good to get a second opinion even without all the information to work with.
Harry

Hi Rolly, that scroll expander thing could be amazing. A bit like an infinitipple-compound with hypnotic abilities.

Hi Andy, there are lots of motor/generators. What rpm, volt, amp do you need?
Are you going to connect the turbine gen to a crankshaft motor?

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