‘Vacuum-Rocket’ Car Sets Style for Dirigible (May, 1936)

‘Vacuum-Rocket’ Car Sets Style for Dirigible
Looking as though it might be as much at home in the air as on the ground, a motor truck propelled by air sucked through a wind tunnel is testing principles that may revolutionize the building of dirigibles. Air is drawn into its concave, funnel-shaped front by a small propeller and is forced out at the rear with tremendous velocity, sending the car rocketing across the earth. Testing it on the Kansas City airport, its inventor, Thomas M. Finley of St. Louis, said he attained a speed of forty-seven miles an hour from a standing start in a half mile. If this propulsion principle were applied to dirigibles, propellers would suck air into a hollow nose and thrust it back through a tunnel in the middle of the bag, creating a vacuum at the front instead of pushing against air pressure.

  1. Kosher Ham says: January 19, 201111:43 am

    It must be a very noisy machine.

  2. Mcubstead says: January 19, 201112:18 pm

    At first glance, it seems totally stupid, but then if you compare the basic shape / concept, a ducted fan, driven by a motor, to a modern turbo fan (fanjet) conceptionally this is actually the same principle, just using a piston and blade. I wonder what this guy could have built today?

  3. Firebrand38 says: January 19, 201112:50 pm

    Mr Finley worked on this for a while

  4. Stephen Edwards says: January 19, 20112:29 pm

    Like an air boat without the boat part. To me, the big question is, why?

    Anybody know the relative efficiencies of air propellers versus water propellers versus wheels on asphalt?

  5. Myles says: January 19, 20113:27 pm

    Stephen – I think the point is he is testing a design for dirigible propulsion, not land propulsion. What I like is the magazine is showing someone testing something, rather than the magazine’s usual MO of having someone draw a prototype, and then boldy proclaiming how it will change the world.

  6. Stephen Edwards says: January 19, 20113:42 pm

    Myles: You’re right — the article is slanted more in the direction of dirigible propulsion than I first thought. However, I’m still left asking, why? Wouldn’t a mounted engine in a wind tunnel be a better test bed. This looks more like an opportunity to show off.

    Also, the last sentence seems rather naive: doesn’t every propeller work on the principle of creating a pressure differential? Doesn’t pushing against air pressure imply there’s a vacuum in front?

  7. Mcubstead says: January 19, 20114:29 pm

    Stephen- He does not appear to be testing the propeller, but rather the performance improvement of a “ducted” propeller. As to the last sentence, the “Right Brothers” propeller works by combining the effect of a wind and the effect of a paddler. The Ducted Fan works kind of like a turbine, in that it uses the decreasing diameter of the tube to accelerate air flow, much like the speed of a river current increases in a narrow canyon. Try this artical it kind shows a latter generation of the concept

  8. Mcubstead says: January 19, 20114:31 pm

    Opps spell check got me, that was “wing” not “wind” in the comment above.

    it should read
    the “Right Brothers” propeller works by combining the effect of a wing and the effect of a paddle.


  9. jayessell says: January 19, 20118:07 pm

    I wonder if it sucked up more air than it passed through while in motion,
    but that would need engine powered wheels also.

    “Right” is wrong, “Wright” is right.

  10. Daniel Rutter says: January 19, 201111:57 pm

    I think the fallacy here was comparing a dirigible with engines in conventional nacelles to a dirigible with the same exterior dimensions, but a bloody great tunnel through it. Yes, the latter airship will have less air resistance, but that’s because it’s now got less frontal area. You’d get the same effect by just putting an empty tunnel through the airship and leaving the engines where they are.

    If you require the airship to contain the same volume of gas bags, crew/passenger areas and so on, then putting a tunnel through it will require you to make the exterior dimensions larger, increasing the frontal area and giving you no net gain at all.

    There was actually fair bit of wasted space inside the giant airships, so it may have been possible for a relatively small tunnel to be shot through the middle without increasing the vessel’s size or complexity very much. But I think that by 1936, aeronauticists had figured out that ducted fans are considerably less efficient than unducted, conventional propellors. The outrageously long ducts required for this airship idea would, particularly, be an efficiency disaster.

    Remove the whole duct assembly from the test vehicle so the prop’s bare, and it’d probably go quite a bit faster.

  11. Mcubstead says: January 20, 20116:20 am

    I started wondering if any one had tried it in flight, and I found a flying blimp prototype and a company moving forward to bring ducted blimps to market.


  12. Toronto says: January 20, 201111:28 am

    The “Porsche blimps” also use ducted fans, do they not?

  13. Charlie says: January 22, 20112:23 am

    Mcubstead: I think those are just ducted to reduce noise.

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