Re: [MV] Tea under armour - sloganeering

From: Nigel Hay -MILWEB (Nigel@milweb.net)
Date: Fri Jul 09 2004 - 00:15:56 PDT


A popular slogan and field painted sign was "When in doubt - Brew up!" I
cant find it but there is a famous pic of Tommies with a Dingo brewing up
with one of these signs.
I guess it was less popular with tank crews........
----- Original Message -----
From: "J. Forster" <jfor@quik.com>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Friday, July 09, 2004 8:48 AM
Subject: Re: [MV] Tea under armour

> Ryan Gill wrote:
>
> > The problem with the ones on the Ferrets was the resistive
> > load could quickly drain the battery so they were
> > all pulled from use. The larger vehicles with
> > more battery power seemed to do ok.
>
> A typical electric 4 to 6 cup coffee pot or tea kettle draws 1250 to 1500
watts for
> 5 to 10 minutes. That's 52 to 63 amps at 24 volts, which is a lot to
expect of any
> battery.
>
> More scientifically: heating water from 20 C to 100 C requires 80 cals/gm
= 80
> cals/cc. The mechanical equivalent of heat is 4.18 J/cal = 4.18
Watt-Seconds/Cal.
> So it takes 80 x 4.18 = 334 W-S/gm The actual power required will be
higher.
>
> So to raise 1 cup, roughly 250 cc, of water to the boiling point, it
takes 250 x
> 334 = 83,500 watt-seconds which is roughly 24 Volts @ 1Amp for 1 hour or
24 Volts @
> 30 Amps for 2 minutes. That's for 1 cup.
>
> > > > Post war you started seeing a boiling
> > >> vessel that would run off vehicle power but was
> > >> portable away from the vehicle.
> > >
> > >I assume this was electric?
> >
> > Initially yes. The US seems to like using fuel
> > fired boiling vessels with all of the associated
> > issues of poisonous gases and such.. I'm not sure
> > what they keep thinking with that...when they add
> > them at all.
>
> Basically, fuel is a lot more efficient way of storing energy than
batteries. I
> posted a comparison some weeks ago and a pint of gasoline has about the
same energy
> content as a car battery a 1/40 or less of the weight.
>
> > Yep! It's less time spent doing comfort/survival
> > things by the troops and if you can make hot food
> > while on the move, it's even better for your
> > crews.
>
> True. Also, the IR signature of a vehicle may be lower than a stove in the
open.
>
> > >If you've got waste heat, it could easily be used to distill water.
> >
> > Give it time. Modern Military engines certainly
> > have lots of waste heat, however, I'm not certain
> > how easy it is to clean such devices...perhaps a
> > disposable distilling element?
>
> If you distill with vacuum at near room temperature, rather than with a
heater, the
> container with the concentrated and dry or nearly dry waste could be
discarded.
> IMO, that's what NASA does.
>
> > When one thinks about it, it seems clear that the
> > brits often have the best ideas when it comes to
> > tanks. After all, they did invent the beasts.
>
> Perhaps it's because they follow the dictum that simple is better than
complicated.
> There are two ways to look at bells and whistles: the optimistic and the
cynical
> (that's something MORE to go wrong). The Brits seem to tend toward the
latter.
>
> -John
>
>
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