I'm with you Dallas. From what I know of fluid dynamics, you're right. The
loops can provide no damping of pulses, since they are full of fluid. I
seem to remember a while back (on another topic) other folks saying that you
have to bleed the line at the gauge to get accurate readings, or in other
words, make sure there is no air in the line.
The loops can only be there to allow movement, so the lines do not fatigue
too quickly.
Cheers,
Chris
BJ8
----- Original Message -----
From: "Dallas Congleton" <dcong996@earthlink.net>
To: <healeys@autox.team.net>; "jerry adams" <cjerryadams@yahoo.com>
Sent: Wednesday, October 12, 2005 3:22 PM
Subject: Re: Why, oh Why?
> Please explain further for a country boy how the loops "smooth out"
> pulsations in the oil? The system is hydraulic once it is filled with oil
> and no compressibility can take place, except for air trapped in the
> system.
> Trapped air is normally the cause for erratic needle fluctuations because
> of
> its compressibility and requires bleeding to correct.
>
> My understanding is the vertical loops and siphons seen on steam system
> gauges and control devices are there to isolate the bellows and diaphragms
> of the devices from raw steam. They condense water in the top half of
> the
> "pigtail" which remains as a temperature buffer. They are not for
> pulsation
> control. Pulsation control requires one of several different dampening
> devices.
>
> Steam of course is not hydraulic like oil so I don't follow the analogy.
>
> Most horizontal loops on steam systems are for mechanical pipe expansion,
> although I don't remember complete loops
> .
> Also many oil gauge lines are actually steel so the copper work hardening
> theory wouldn't apply?
>
> Dallas Congleton
> 1967 BJ8
> 1953 MG TD
>
> ----- Original Message -----
> From: "jerry adams" <cjerryadams@yahoo.com>
> To: "Brashear, Jack, N" <JNBrashear@garverengineers.com>
> Cc: "Healey list" <healeys@autox.team.net>
> Sent: Wednesday, October 12, 2005 2:48 PM
> Subject: Re: Why, oh Why?
>
>
>> Jack,
>>
>> David Nock hit part of the nail on the head. The loops are there to stop
> pulsations, either fast or slow. The fast pulsations from the oil pump
> can
> be smoothed out also the slow pulsations from the heating and cooling of
> the
> oil temperature will also be "smoothed" out. Actually the heating and
> cooling can be called expansion and contraction. This little engineering
> design was dreamed up back in the 1800s or earlier when steam engines were
> being developed more and being used in more than trains and ships.
>>
>> These loops should be an all Austin-Healeys.
>>
>> Jerry
>> BN2
|