[GSBN] Calibration of Balemaster probe

Sun Nov 8 20:41:02 UTC 2009

 Maybe it's the approach of Thanksgiving here in the US of A, or maybe just because it struck such a deep chord in me - I want to point out and acknowledge my gratitude for this exchange...for the reflection of the beauty of this community of people as much as for the content. 

What prevails here, in abundance, is a generosity of spirit, civility, concern for each other, and others beyond this circle, as well as for ourselves. And a willingness for dialogue rather than domination of a single point of view. And, though not present in this particular exchange (yet), good humor (or, for those of you of Canadian or British or some other persuasions, humour).

Derek's concerns, expressed as always with integrity and respect for the views of others, are for the larger good and take into consideration a number of higher level, or perhaps deeper, aspects of the exchange of information here. Jim responds from a place of both recognition of Derek's specific concerns and for the value of the free flow of information in this forum and in general. 

Derek's concerns are real and can be serious - both the ability to safeguard certain kinds of academic and research work until published, for example, and the free flowing, open discussion of things that might be problematic for some in a variety of other ways. The challenge is not unique to this community, but the willingness to share so openly seems to be pretty rare. 

This makes me wonder if there might be a way to automate a kind of differentiation of posts - some of which would not automatically be archived in the public sphere - perhaps using a key word in the subject line of posts that contain info not intended for wider distribution. I don't know how feasible that might be, but I would hope we might find a way to preserve both the openness of the flow of information and exchange and also preserve something of a more private/tighter community sharing when that is appropriate. On the other hand, I don't want to see more burden placed on Bill C for additional work.

Either way, I just want to say how much I have appreciated and continue to value the existence of this list, the archives, and especially the members and their contributions. Kudos to Bill for all his work to keep this list functioning and for making the wealth of information that has been generated and shared here available to so many people. 

Warmest regards to you all,

David

-----Original Message-----
From: Jim Carfrae <jim.carfrae at plymouth.ac.uk>
To: (private, with public archives) Global Straw Building Network <GSBN at greenbuilder.com>
Sent: Sun, Nov 8, 2009 11:12 am
Subject: Re: [GSBN] Calibration of Balemaster probe

Hi Derek

You're right in that the figures I gave for each density are an average across 
the bale. In fact I inserted the Balemaster through six different holes in the 
box and measured at 50mm intervals, giving 36 readings at each density.
Because I'd prepared the bale fairly carefully, there wasn't too much variation 
- but in each case you could tell whether the reading was going to be higher or 
lower by the resistance to the Balemaster.

The spread of measurements at each density where as follows:
Density 95Kg/m3. Lowest 13.6, highest 15.1, average 14.7
Density 108Kg/m3. Lowest 14.5, highest 16.2, average 15.8
Density 118Kg/m3. Lowest 14.6, highest 16.4, average 16.0
Density 129Kg/m3. Lowest 14.7, highest 17.1, average 16.3
Density 142Kg/m3. Lowest 15.0, highest 17.6, average 16.6

This is slightly misleading, as the majority of the readings were more 
consistent - the highs and lows were down to variations in the packing of the 
straw at the edges.
I think it would be fair to say that in this experiment the variations were all 
be due to density, but in the field (so to speak) the variations as you say can 
be higher, and moisture could be a factor as well.
Also as you say, this gives more confidence to the readings from a Balemaster 
and I don't think a straw bale professional should be without one (certainly in 
the variable climate we enjoy in the UK!)

As far as far as my request for the information to be kept within the GSBN - yes 
I'd forgotten that Google will find it (which is how I found the GSBN myself 
before Tom Woolley nominated me).
But I couldn't have built my first straw bale house without information freely 
shared, and I would rather the data was out there on a widely read forum than an 
academic paper read by two men and a dog. I just have to be careful that the 
data isn't quoted by someone else before I publish!
The problem with information being read beyond the forum is perhaps more to do 
with misunderstandings and mistakes being made by people who don't have the 
depth of knowledge found within the forum.

Cheers

Jim

Jim Carfrae
PhD Research Student

Room 119, Reynolds Building
University of Plymouth
Drake Circus
Plymouth
PL4 8AA

jim.carfrae at plymouth.ac.uk
07880 551922
01803 862369
________________________________________
From: GSBN-bounces at greenbuilder.com [GSBN-bounces at greenbuilder.com] On Behalf Of 
Derek Roff [derek at unm.edu]
Sent: 08 November 2009 14:33
To: (private, with public archives) Global Straw Building Network
Subject: Re: [GSBN] Calibration of Balemaster probe

Thanks for sharing this wonderful data, Jim.  Your figures brought up
a question for me about variation between measurements of the same
straw at the same density and moisture content.  I'm guessing that
the figures that you show are averages of some sort.  I'd like to
hear more about that.  I'm thinking that you probably didn't insert
the probe one time at each density, and move on to other densities.

I have observed that it is normal to get some variation in the
Protimeter readings, when inserting the probe into the same bale at
about the same spot in the bale, to similar depth.  I haven't done
careful recording of this variation, but when I want to test a bale,
I insert the probe three or four times and do a quick mental
averaging.  I haven't tested that many bales, but I remember seeing a
variation of two or three percent, sometimes more, between the
different Protimeter readings.  Some of that variation could come
from actual variation in the moisture levels at slightly different
spots in the bale.  But I think most of it is from differences in how
the straw interfaces with the probe.

What variations did you see, Jim, between one measurement and
another, in your test bale at the same density?  Can anyone else on
this list indicate the variations you have seen, in probing nearby
spots in the same bale?

Your figures indicate that we can be pretty confident about the
values that we get from a moisture probe.  That is good news.  Thanks
again for sharing this information.

Derelict

PS.  One concern that I have about GSBN is highlighted by your
request at the end of your message.  You ask that we keep the results
to ourselves, since you are considering academic publication of this
information.  That's an explicit, valid, and valuable statement ,that
you are not yet ready to share this information with the entire
world.  It tells me that you are not aware, or not remembering, that
any message sent to GSBN is already available on Google to anyone,
anywhere, even before it hits my mailbox.

I think there is a danger in the fact that our GSBN archives are set
up that way.  It means that either people like Jim will be hesitant
to share valuable preliminary work, or that they will forget that
GSBN is not in any way private, except in who can post, and will
share their research, and regret the consequences.  (Often, there
will be no negative consequences, but the more research that we
discuss here, the more likely that there will be negative fallout.)

Either way, I think the current archiving approach does more harm
than good.  I think there is value in GSBN being a safe sandbox, in
which to discuss ideas that we aren't ready to share with the world.
The last time that this was discussed, my viewpoint was in the
minority.  Jim, I would appreciate it if you would comment on how our
instantly-open archives will affect your willingness to post
information.

I deeply respect the  people who have expressed a different viewpoint
on this archiving question, and I am not arguing for closing the
archives forever.  I don't have a specific proposal for how the
archiving should be structured.  I would just like to honor a request
like Jim's, that we all exercise a little human discretion with his
experimental data.  It bothers me that, even before any of us read
it, his request has been violated via our automation.

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu

--On Sunday, November 8, 2009 11:58 AM +0000 Jim Carfrae
<jim.carfrae at plymouth.ac.uk> wrote:

> Hello All
>
> There have been a couple of threads here about the accuracy of
> straw bale moisture probes like the Protimeter 'Balemaster'. The
> big question on probes of this sort (that measure the electrical
> resistance of the straw at the tip, and translate this into a
> figure for moisture content) is how far the accuracy is affected by
> the density of the straw. David Eisenberg has described how, if you
> take a handful of straw and wrap it around the tip of the probe,
> the moisture reading goes up and down as you press the straw
> against the probe, which indicates a potential problem! I decided
> to set up an experiment to try and find out how much of a problem
> this actually is, and here is the methodology (for those who care
> to know).
>
> First I built a box with a lid that could be pressed into it.
> I then measured the internal volume of the box, and weighed out
> some straw that if compressed to the density of a typical bale
> (110Kg/m3) would fill the box exactly. The straw was taken from a
> bale that had been at the back of my garage for some time, in a
> reasonably stable environment, with wood stored next to the bale
> measuring (with a Protimeter 'Timbermaster') 16.1% moisture content
> The straw weighed out to go in the box was loosely restrung from
> the bigger bale, and before I placed it in the box I calculated the
> volume, then measured it with the Balemaster. I then placed the
> straw in the box and gradually screwed the lid down, stopping at
> pre-determined intervals to probe the straw through holes drilled
> in all sides of the box. After the lid had been screwed down as
> tight as it would go (at which point the straw was too dense to
> easily insert the Balemaster), I took the straw out, re-weighed it,
> and then dried it in a fan oven until it had lost all it's moisture.
>
> Results.
> Loosely retied straw; density 68.5Kg/m3, Balemaster reading 12.2%
> Straw in box; density 95Kg/m3, Balemaster reading 14.7%
> Straw in box; density 108Kg/m3, Balemaster reading 15.8%
> Straw in box; density 118Kg/m3, Balemaster reading 16.0%
> Straw in box; density 129Kg/m3, Balemaster reading 16.3%
> Straw in box; density 142Kg/m3, Balemaster reading 16.6%
>
> Actual moisture content of straw, determined by  gravimetric
> analysis (weighing, drying, weighing again) 16.2%
>
> This was a very encouraging result; wood next to the straw was
> 16.1%, Balemaster readings at the sort of densities found in a
> typical wall ranged from 15.8 to 16.3%, and the straw was actually
> 16.2%
>
> An observation: I've surveyed many straw buildings with a
> Balemaster, and the Balemaster will give you an impression of how
> dense the bales in the wall are according to the resistance as you
> insert it. This was borne out when using the Balemaster to probe
> the straw in the box, with the straw at 95Kg/m3 feeling slightly
> loose, and the resistance gradually increasing with 129Kg/m3
> feeling as tight as almost any building in my experience, and at
> 142Kg/m3 it was almost impossible to insert the Balemaster.
>
> I hope this will be of interest, but I would ask you to keep these
> results to yourselves, as I hope to publish them as part of an
> academic article soon.
>
> Regards
>
> Jim
>
> Jim Carfrae
> PhD Research Student
>
> Room 119, Reynolds Building
> University of Plymouth
> Drake Circus
> Plymouth
> PL4 8AA
>
> jim.carfrae at plymouth.ac.uk
> 07880 551922
> 01803 862369
> ________________________________________
> _______________________________________________
> GSBN mailing list
> GSBN at greenbuilder.com
> http://greenbuilder.com/mailman/listinfo/GSBN

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu

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