Re: OT: Nitrogen filled tires

On Mon, 15 Oct 2007 17:43:24 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@xxxxxxxxxxxxxxx> wrote:

On Tue, 16 Oct 2007 00:33:57 GMT, Glen Walpert <gwalpert@xxxxxxxxxx>
wrote:

On Mon, 15 Oct 2007 16:30:06 -0700, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On 15 Oct 2007 20:30:16 GMT, Jim Yanik <jyanik@xxxxxxxxx> wrote:

I did some math in my head last night, to lull myself to sleep.

Imagine a reasonable-mass metal ring parallel to the wheel, half the
diameter of the tire, connected by a disk or spokes to the pump shaft
at the center of the wheel, with the pump body fixed to the wheel.

Imagine a car accelerates to, say, 60 k/h and back to zero, maybe 20
times a day. One could get kilojoules of work per day at the pump
shaft, easily enough to keep a tire inflated. If you used a full-size
spinning wheel cover, the increased radius helps even more (squared,
even) and using air drag helps more yet, since that add a continuous
power source that increases greatly with speed.

Do the math... it's easy.

John




You are neglecting how little work you can get from the AIRFLOW that a
sideways fan assembly will get.

It's really not a fan assembly. You'd design it to have a lot of
rotational drag, so it tends to lag behind the wheel speed. The
relative motion could drive the tiny pump. At freeway speeds, the
force would be large. Stop-and-go, it would work in inertia mode.

It would only need a little energy per day to keep a tire topped off.
The pump could be tiny.


Your powerful ram air generator has it's fan blades oriented facing the
airflow.Spinners are sideways to that airflow,and you would need some
ducting to direct the airflow to propel the blades.

It only needs rotational drag, which doesn't benefit from ducting.

you just are not going to get any useful energy transfer from the spinning
auto wheel to your pump gearing.

Gearing?

You evidently have not observed a wheel
spinner in action,or you'd know what I'm talking about.

You evidently haven't done the math.

I have to admit that this silly idea could be done, for example with
the "spinner" weight connected directly to the shaft of a very tiny
single piston compressor similar to a model airplane engine only
smaller, with reed in/out valves in the head and no side ports.
Bearing drag and the compressor shaft torque would spin the weight up
during acceleration, delivering a few strokes of compression, and
deceleration would deliver a few more in the oposite direction
(rotation direction is irrelevant to compressor). You could put all
the air in the tire and let out the excess with a relief valve set at
32 PSIG or whatever is desired.

But I don't like the idea, too cumbersome and delicate, and the
spinners would look lousy on my Yugo. Plus the extra unsprung weight
would spoil its handling.

What is wrong with the usual approach of instaling a compressed air
rotary joint on each axle, connected to the tire through a Schrader
valve in the wheel (so it holds air when removed). The stationary end
of each rotary joint connects to a pressure transducer and fill (from
engine driven compressor) and vent solenoid valves, controlled by the
tire inflation computer. A dashboard control lets the driver adjust
tire inflation from inside, so for instance pressure could be dropped
to 20 PSIG for driving on sand and back to 32 for highway driving, or
upped a bit for driving in rain. This arrangement works pretty well
on my Yugo :-).

Glen

My thought was a diaphragm type pump built into the wheel itself. As
the wheel rotates it passes a magnet attached to the strut.

...Jim Thompson

That's good for OEM, not so good for retrofit.

It makes more sense to me to add auto-fillers, as an alternate to the
upcoming federally-mandated tire pressure sensors, which will
apparently be mems pressure sensors, rf links, and lithium batteries
inside every tire.

John



.

Relevant Pages

  • Re: OT: Nitrogen filled tires
    ... Imagine a reasonable-mass metal ring parallel to the wheel, ... at the center of the wheel, with the pump body fixed to the wheel. ... shaft, easily enough to keep a tire inflated. ...
    (sci.electronics.design)
  • Re: OT: Nitrogen filled tires
    ... Imagine a reasonable-mass metal ring parallel to the wheel, ... at the center of the wheel, with the pump body fixed to the wheel. ... easily enough to keep a tire inflated. ... Bearing drag and the compressor shaft torque would spin the weight up ...
    (sci.electronics.design)
  • Re: Help with coolant leak on 96 SL
    ... definately jacked the car up, removed the wheel, panels took the slack ... First step is to remove right front wheel and 2 plastic fender well ... Next remove A/C compressor. ... Next remove 3 bolts holding the pulley on the pump. ...
    (rec.autos.makers.saturn)
  • Re: Tire gauge off by 7 pounds
    ... I was working on the rent house across the street, I had backed my pickup over there and it had a slow leak tire and the old worn tire was about flat. ... Of course I got busy doing something else and forgot about the little compressor running. ... Later when I remembered I went over to find the little compressor still running but the little pump on it had worn out, the gage on the compressor showed 105 lbs, that was all it could handle before breaking. ...
    (alt.autos.toyota)
  • Re: air compressor redux
    ... The kind of pump you step on, will do a reasonable job. ... have a very old Coleman compressor, ... flat tire. ... NOT A BICYCLE PUMP: Those are for low volume, ...
    (alt.home.repair)