Date: Thu Aug 13 13:22:12 2009 Back to Contents ------------------------------------------------------------------------

Author: Bill Alexander

Subject: Re: Ruben's Tube Question

Post:

I believe it comes down to the ratio of the tube diameter and the holes. As long as the pressure is able to remain approximately equal down the entire length, it won't matter. I believe 1/8 inch holes are too large for that size pipe and gas supply. I doubt (but am not sure) that the pipe thickness is a factor, since you are really concerned with the pressure at the site of the hole inside the pipe. If the holes are too large or the tube too small, there will be a significant pressure drop down the length of the pipe. Ours is around 10 feet long, 3 inch down spout pipe, 1/16 inch holes every half inch. If I were doing it over, I would try using a slightly smaller number drill bit, and maybe putting the holes a little closer together. Ours will not self-light down the length. We are burning natural gas. As an aside, in one of our lab rooms, for some reason, there is slightly less gas flow out of the jet, and the only way I can get it to work satisfactorily is to use two jets teed into the one inlet on the end of the tube.

Bill A.

----- Original Message -----
From: "David Maiullo"
To: tap-l@lists.ncsu.edu
Sent: Thursday, August 13, 2009 9:40:31 AM GMT -08:00 US/Canada Pacific
Subject: Re: [tap-l] Ruben's Tube Question

I agree with Adam and his excellent explanation...my Ruben's Tube has
only one gas input and it's on the opposite end from the speaker. Once
lit and filled with propane (one-two minutes), there is no difference in
flame height from one side to another during use.

Dave/RU

> Pati Sievert wrote:
>> Did any of you notice in his description that he has the gas entering
>> through the end? I would think that besides the uneven gas supply he
>> mentions that the interruptions would interfere with the reflection
>> of the wave at that end (opposite the speaker). I notice all of
>> yours have gas inlets somewhere along the length of the pipe and not
>> in the end, but none of you commented on that.
>
> I noticed. The tube that lives at my workplace has the gas inlet on
> one end and the speaker on the other. I rarely notice uneven gas flow
> out of the holes. If I ever get higher flames, it is on the end with
> the speaker, NOT the end with the gas inlet. My understanding is that
> once the tube is filled and comes to some equilibrium condition during
> operation, the incoming gas just keeps the tube from running out.
> Without any sound waves going in, the pressure is roughly the same
> everywhere inside the tube (Pascal's principle, especially with small
> holes). The sound waves just cause variations in that base pressure.
> Any additional incoming gas simply maintains that base pressure. Now
> granted, you can find unstable conditions based on how fast you let
> the gas rush in, how high the volume is on your speaker, which
> frequencies are being produced, and how big your holes are, but for
> the most part, I have never noticed a problem with uneven gas supply
> even though my inlet is at an end.
>
>

--
Bill Alexander
Humboldt State University
Arcata, CA 95521
707-826-3212

Any job worth doing is worth buying a new tool.

From tap-l-owner@lists.ncsu.edu Thu Aug 13 13:22:12 2009

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