Propeller vs Direct drive
 

Off the wall question;
What is the difference in efficiency between propulsion from a propeller vs a direct traction drive (wheels, including drivetrain losses)?

My research lead me to some odd vehicles, and more questions as usual.
http://i.kinja-img.com/gawker-media/...c10kqfhjpg.jpg
http://i.kinja-img.com/gawker-media/...ha1ou1bjpg.jpg
http://i.kinja-img.com/gawker-media/...o2hnwkojpg.jpg
http://i.kinja-img.com/gawker-media/...a05nnvejpg.jpg

More fun
https://www.youtube.com/watch?v=6j_W...j6Ck6Rs-wXjf36
http://1.bp.blogspot.com/_SqhhJb_P3K...pellor+car.jpg
http://www.dailymotion.com/video/xfn...ler-car_travel
http://www.helica.info/192001.jpg
http://blog.modernmechanix.com/mags/...d_prop_car.jpg
http://theoldmotor.com/wp-content/up...pV-600x400.jpg
http://gajitz.com/wp-content/uploads...er-train-1.jpg
http://gajitz.com/wp-content/uploads...er-train-2.jpg
http://socialmediatweet.com/wp-conte...arin-jones.jpg

http://images.gizmag.com/inline/skyrunner-2.jpg
http://images.gizmag.com/gallery_lrg/skyrunner-0.jpg

https://www.youtube.com/watch?v=L_CnvRufT7c

Prob fun for its own thread
http://www.techvert.com/wind-powered...than-the-wind/
http://www.techvert.com/wp-content/u...poweredcar.jpg

True, I'm thinking around 45-70% of direct depending on pitch. Not sure though.
Using
ηp=T∗u/Pshaft

A bad amount for mpg. The project places too much priority on weight though.

http://hizone.info/data/2005/09/08/images/03.jpg

http://i.kinja-img.com/gawker-media/...csnvbyljpg.jpg
http://lh4.googleusercontent.com/-VJ...4/s900/p12.jpg

http://www.curbsideclassic.com/wp-co...wagen-prop.jpg
http://lh4.googleusercontent.com/-X4...-4/s900/p5.jpg
http://lh3.googleusercontent.com/-MZ...U/s900/p20.jpg

Lotus
http://www.wired.com/images_blogs/au...otus_ice05.jpg

http://db2.stb.s-msn.com/i/C4/C3E0EF...A9F145A7C8.jpg

http://blog.modernmechanix.com/mags/..._drive_car.jpg

http://www.team-bhp.com/forum/attach..._propeller.jpg

http://blog.modernmechanix.com/mags/...p_tricycle.jpg

http://blog.modernmechanix.com/mags/...ed_fan_car.jpg
https://www.youtube.com/watch?v=xRV7RmTk2yA

http://riordanco.com/jimsblog/wp-con...cycle02jpg.jpg
http://riordanco.com/jimsblog/wp-con...ropcycle01.jpg

http://www.sonicwind.com/image/aeroliner-1.jpg

http://www.sonicwind.com/image/dragprop.JPG

https://www.youtube.com/watch?v=4LJuGftUFbI

http://www.petersen.org/uploads/imag...Driven-Car.jpg

http://www.strangecosmos.com/images/content/144192.jpg

More fun
http://www.treehugger.com/bikes/the-...ith-video.html
http://media.treehugger.com/assets/i.../prop-bike.jpg

Screw the cars, now an air train, thats front page news. :thumbup: Trains doesnt have much traction, thats why they are soo efficient. They use sand to air in starting off and braking as traction is soo limited due to what little contact all that weight makes with the rails and wheels.

http://gajitz.com/wp-content/uploads...er-train-1.jpg

I don't see it coming to a mass-production car, maybe a turbine-propelled one would make more sense nowadays.


I wonder if the propeller could even help to improve braking, let's say, if it could be easily reversed in order to act as an aerodynamic brake.

Is there any gyroscopic effect?

As for efficiency, I expect it's much less efficient than a direct drive in stop and start driving, and I wonder what it would be like to drive behind a propellor driven vehicle in traffic!

With enough back wind a propeller is better.

From what I remember about propellers, I think it was around 59% energy transfer before it was easier for the air to move around the propeller.

The big advantage is not relying on the wheels for traction, like has been stated, and in the old magazine clippings that is what was stated as well, ideal for low traction areas like mud, grass, ice.

When I've driven an air boat, that is a boat with a flat bottom and a large prop in the back, it was very much a fluid drive, like driving a vehicle with a very loose automatic transmission.

It would at least discourage tailgating :-)

Then you take your propeller driven car to a restaurant on a sunny warm autumn day.
You find a vacated but narrow parking slot under the trees close to the tables where people dine. It takes some manoevring back and forth to fit nicely in that slot.

You'd better leave a big tip.

Im sure small in wheel electric motors could be used to move the car in an dout of parking places, drive ways, parking garages, then once you are on the main road you fire it up. :thumbup:

Of course the real question is why? Not only are propellers much less efficient than a conventional drivetrain, they have all sorts of problems that are familiar to those of us who fly small planes, particularly off rough fields.

First, the throttle response is very non-linear. Get a wheel stuck behind a bump or similar, and you have to give lots of throttle to get over it, then you immediately start accelerating. Meanwhile, you're sand-blasting everything behind you. Oh, and that sand-blasting is also eroding the tips of your expensive prop...

Nor can we forget about the interesting effects of driving in snow or freezing rain, which causes your prop to ice up & lose efficiency, and probably shed chunks of ice outwards at high speeds. (Prop tips move at a significant fraction of the speed of sound.)

Then add the negatives of high noise levels and the effect of bird (and possibly larger animals,pedestrians, etc.) strikes on the prop and what happens when plastic bags and other road debris kicked up by traffic encounters the prop and, as a minimum, throws off the balance of the prop. Aircraft ground operations occur in the fairly controlled environment of an airport, very different (for example) from that experienced by a car following a semi in the rain or snow.

We built this for some power tool drag racing :D

It was very very noisy & very very slow

https://www.youtube.com/watch?featur...-bBFLWTKkvf5Zw

I always thought it would be neat to put a bicycle in an aero envelope and add a 50cc 4 stroke engine and one of the larger model airplane ducted fans. Pedal to get up to a speed then engage the ducted fan when conditions allowed.

regards
Mech

I wonder if that is under acceleration or at constant speed, and fixed or variable pitch. A conventional drive will lose between 10-25% from friction and pumping (auto), so that's not too terrible.

FAR 103, and not wanting to be limited to location.

A ducted fan or shrouded prop would help the stop and go, allow or a low prop (CG), and make shielding easy. With pitch control the drag losses might be comparable to a unshrouded/ducted, fixed prop at speed. Both of those add weight though. Maybe some emergency floats could offset that.

Did some research, oddly enough there is no law against driving with a prop, so long as your wheels don't kick up rocks.

There's also the possibility of hydrostatic, but that's heavy and inefficient too.

Not so, at least per ORNL research, which puts drivetrain losses at 4-7% Where the Energy Goes: Gasoline Vehicles Meanwhile, the BEST you can get from a prop is about 80%.


So you're going to drive your ultralight around on the roads? But I'm still confused about the why part - unless of course you're planning to take the traditional meaining of IFR (I Follow Roads*) to its logical extreme.

Off topic, but I once worked for a guy who claimed he was following California Hwy 99 north of Bakersfield in the fog, and wound up flying under a freeway overpass.

That's a good point. I have already seen some propellers damaged by collision with birds, so you can guess what would happen in case of collision with a bigger animal...

That 59% is in ideal conditions as I understand it, the mathematical max that you can get before air just moves around the prop.

With a regular drive-line you can get 98% with a well designed gear box or chain drive, the rest of it, tires and bearings are going to be the same because you have to have those to have wheels on the ground.

Or chop-suey :D

I wasn't going to post these so the idea wouldn't distract the technical discussion. Looks like that's been fairly well covered, so now some fun:

http://http://pal-v.com/
http://www.blessthisstuff.com/imagens/stuff/pal-v.jpg

Super Sky Cycle, The Flying Motorcycle | motorcycle News @ Top Speed
http://i.telegraph.co.uk/multimedia/...r_2050487i.jpg

Meet Dezsö Molnár and His Flying GyroCycle - Tested
http://www.reaa.ru/yabbfiles/Attachm...585_331_90.jpg

But I want to do it under 103. The prop idea was to reduce weigt to allow a 4 stroke.

Hmm, interesting. Thanks.

Now that's an even bigger why. I can, barely, see the point of a fixed-wing roadable ultralight - you might not have room to take of/land close to your destination - but with a helicopter? And with an autogyro, you still have to have a takeoff run.

And if you want it under FAR 103, remember you'll have to add weight for things that make it road legal, like head & tail lights, turn signals, etc.

2 strokes are just temperamental and more prone to failure. They're also less efficient overall, but very light in hp/lb.

And having it roadable allows me to find a spot to use for takeoff and landing. At home its not a problem the driveway alone 800 feet. Destinations are a problem. A Pre-rotor would help, and may provide a method of propulsion tying into that system (if hydraulic).

No turn signals here. Will need a headlight, horn, tail/brake light, and one mirror. A gryo seems like the best option. A helicopter would be hard to make light enough, and a plane too bulky. If a 60 year old square tube Bensen can be under 254, an updated design with emergency gear allowances, some propulsion system and street gear should be doable.

So how far are you looking to travel on road at your destination?

My solution (with a Piper Cherokee) was to just take out the rear seat so I had room for the mountain bike. And would land on dry lakes, or the occasional stretch of deserted highway.


I honestly wouldn't think that would be at all practical, with the large rotor hanging out there where it can bang into things, or be hit by people not seeing it. Even if you could secure it fore and aft, it'd still be like carrying long pieces of material sticking out the back of your pickup. You really have to give some thought to Murphy's Law, you know :-)

But I do understand about not wanting 2-stroke power.

Bumped into this on the web:

An Aerosani (Aerosani - Wikipedia, the free encyclopedia)
https://i.chzbgr.com/maxW500/2980350720/h9211431A/

which linked to The Propellor-Driven Sleigh. like this NKL-26 Russian military aerosled:
http://www.aqpl43.dsl.pipex.com/MUSE...gh/nkl26_1.gif

1932 Helicron (The Helica.):
http://www.aqpl43.dsl.pipex.com/MUSE...201932%20a.jpg

Those last 2 and wagonloads more eye candy can be found in the Museum of Retro Technology

for example the Cyclogyro (http://www.aqpl43.dsl.pipex.com/MUSE.../cyclogyro.htm):
http://www.aqpl43.dsl.pipex.com/MUSE...yclogyre1a.jpg

PS. saw Old Mechanic found that site first: http://ecomodder.com/forum/showthrea...gns-30553.html
But it is much more than just engine designs :)

I still like the idea of a 30-06 spitzer bullet shaped ducted fan. Very light weight and then you use the fan for higher speeds. Plenty of bikes engineered for higher speeds and relatively lightweight

If my 50 year old scooter can go 43 MPH and get easily over a hundred mpg then A bike with a modern engine would be interesting, just a small 4 stroke 50cc so it falls under scooter laws.

What appeals to me is at higher speeds where you can't pedal a normal bike the ducted fan would give you thrust assist, which could be supplemented with pedalling to get to a higher speed or climb a grade' the use the fan to maintain ahigher average speed than you could ever do pedalling.

Carrying an extra source of thrust also would reduce the aero drag, pulling air from high pressure areas and blasting it out in the rear in the normal low pressure area.

regards
mech

If you pardon the obvious PUN, some of those propellor-driven car ideas SUCK and others BLOW (wink,wink)!

Either way has its fandom...

Well, that's a new twist on the situation...

It looks like the engineers thought of everything on this design. They have smartly located the fuel tank in front so that when the aircraft crashes, killing everyone, they can be cremated on spot.

http://www.aqpl43.dsl.pipex.com/MUSE...yclogyre1a.jpg

prop efficiency
 

I think Hoerner gave props a maximum of around 87% mechanical efficiency for applying power to the air.
A NASCAR micro-finished driveline with 1:1 output Gear Vendors (Doug Nash Racing) transmission would be looking at around 94% overall efficiency,from flywheel to tire/road interface.