Is leather stronger when laminated with an additional layer of leather?

[thekid77]

9 hours ago, Les No6 said:

Single strap is strongest the strength is in the coarse fibres as referenced in the Hasluck books, not the grain that’s just a brain fart or marketing BS as is over 90% of the internet including this website these days.

Could you be more specific about your reference in the Hasluck book? I found the book but I don't see that info in there...

How about a page number?

Thanks

Edited December 21, 2016 by thekid77

[TinkerTailor]

10 hours ago, Les No6 said:

Single strap is strongest the strength is in the coarse fibres as referenced in the Hasluck books, not the grain that’s just a brain fart or marketing BS as is over 90% of the internet including this website these days.

This is also why the old books say a strap is best from unsplit leather, as mentioned above. These coarse fibres are also long, and intertwined, which is where the strength comes from. Same idea makes cotton fibers strong when woven into denim. Splitting cuts these fibers shorter. Shaving denim thinner and then doubling it up will not be anywhere near the strength of thicker denim.

 

[thekid77]

51 minutes ago, TinkerTailor said:

This is also why the old books say a strap is best from unsplit leather, as mentioned above. These coarse fibres are also long, and intertwined, which is where the strength comes from. Same idea makes cotton fibers strong when woven into denim. Splitting cuts these fibers shorter. Shaving denim thinner and then doubling it up will not be anywhere near the strength of thicker denim.

 

With all due respect, what "old books" are you referring to?

And where does it say this..not trying get to argue just trying to learn......lots of info out there, some bad and some good..

[TinkerTailor]

I have a library of hundreds of pdfs of old leatherworking and tanning textbooks. I have aquired these from many places on the net over the years, some i forgot where and many have disappeared behind paywalls and are not available to view without memberships. This information is in quite a few of them. You can find a few books on archive.org if you look around. I would post the pdfs here but they are all way too huge. Some are 100mb....

From "The manufacture of leather"  by Allen Rogers, PHD , printed in 1922: (sorry for the formatting)

4. Analysis of Skins. — At
first glance, the pelts of
various animals appear to have
little in common. On closer
examination, however, a very close similarity will be observed.
In structure, all animal skin is made up of several readily
defined layers. The skin is not merely a covering for the
animal, but also serves as a container for nerves and secretive
glands, and as a bed, or ground, for the hair, or fur. It is
made up of two principal layers : the epidermis, or cuticle, and
the corium, or tnie skin. These two layers are totally distinct
in structure, origin, and functions.
5. The epidermis is a thin covering of the true skin
and is entirely removed before the tanning operations begin.
In life, the upper, or external, part is being constantly worn
away, falling off in the form of dry scales. The interior part
of the epidermis is made up of numerous living nucleated
cells ; as the surface of this layer is reached, these cells
become flattened and finally dry up and form the exterior part
of the epidermis and ultimately drop off as dead
scales.
These cells, which renew the horny external tissue of the epi-
dermis, are in turn renewed by vessels situated in the corium,
or true skin. The epidermis does not combine with tannin
and is therefore removed, laying bare the true skin, which is
known to the tanner as the grain.

6. The corium, or true skin, is the skin with which the
tanning agents combine to form leather. There is an inter-
mediate albuminous layer between the corium and the epidermis.
Both layers are composed of interlaced bundles of fiber running
across and above one another and parallel to the surface of
the skin. These fibers are surrounded by fluid matter, which
serves to keep the skin in a moist and pliable condition. On
removal of this fluid the fibers alone remain, and if dried by
a gentle heat they assume a horny appearance and become in
substance about one-third of the raw hide.
The corium determines the quality of the leather that can be
made from a hide. Its thickness, flexibility, and strength are
reproduced in the leather. Between the fibers of the corium
is an albuminous substance called coriin: in a dry state this
holds and connects the fibers.
The connective tissue of the corium gives form to the skin,
the intercellular substance, coriin, lying between the fibers.
When boiled with water, these connective tissue fibers form
glue, losing their organized structure, and making a homo-
geneous jelly.
7. The intercellular substance is probably a decomposition
product of the connective tissue. This coriin is soluble in
lime water and other alkaline solutions ; frequent treatment of
the skin with these reagents withdraws fresh quantities of
soluble matter with every treatment. This fact should be
noted in connection with the liming of skins to remove the hair.
Dilute inorganic acids swell the connective tissue. The
swelling of the skin by acids is made use of to facilitate tanning
;
it not only makes the skin more sensitive for the reception
of the tanning material, but also effects the disintegration of
the fiber bundles into individual fibers, thereby increasing the
surface.
8. The under skin is made up of loose connective tissue,
embedded in which are the sweat and fat glands, the blood
vessels, and muscular fiber. Fig. 1 shows an enlarged micro-
scopic transverse section of the skin in which the Malpighian
net, or lower layer of the epidermis, is shown at d ; the corium,
 

Edited December 21, 2016 by TinkerTailor

[TinkerTailor]

7 hours ago, thekid77 said:

Could you be more specific about your reference in the Hasluck book? I found the book but I don't see that info in there...

How about a page number?

Thanks

I could not find it in the Hasluck leatherwork book, but i did see referenced to his harness making book, which i have not seen. I did find this on page 30 of THE HARNESS-MAKERS ILLUSTRATED MANUAL., W.N.Fitzgerald, 1875:

 

So well is this understood by leading harness-
manufacturers who make up full lines, that they
never cut a harness from a single side, but select
the leather carefully and use a specific grade or
weight for each particular strap; while the leading custom manufacturers purchase or cut only
backs of the best quality. The great majority,
however, buy their leather in small quantities, and
by so doing commit the error of not procuring
a proper assortment.As a rule, they select the
weight best adapted to the greater portion of
their work, and when lighter stock is needed they
resort to the splitting-machine, entailing on them-
selves extra labor, and wasting no inconsiderable
amount of leather, besides materially weakening
the straps thus manipulated, as the portion of the
flesh side which is removed is the strongest part
of the stock.

[MADMAX22]

I tried for a little while to search for any test results for leather but didnt find any actual results information. Saw some pretty cool pictures of the old break test machines, alot of test requirements for leather and textiles in general but that was about it. 

Only results I actual found were rub wear test for motorcycle racing suits of various materials, apparently the racing grade leather outfits were the highest rated with exception of some thick Kevlar compound woven material, and that was a specific one other Kevlar compounds didnt fair half as well.  

[TonyRV2]

I came upon an old reference online that was written in the 1880's that involved the use of leather belts being used to drive pulleys.  The article talked about both the tensile strength (stretching forces) and compression forces working on a belt as it drove a pulley system.  The compression forces, the article claimed are negligible and do not harm the leather.  These forces existed on the inside of the belt as the belt turned directly against the pulley.  As the belt travels in between the pulleys it undergoes tensile forces, and this is where the article place most of the emphasis.  The author referred to a test in which the leather was split and then subjected to testing.  The grain side ripped at a force of 468lbs while the flesh side was able to reach around 770lbs.  So it would seem when it comes to tensile strength at least, that the flesh is much stronger than the grain.  I found it noteworthy that the grain side should always be against the pulley since it provided a much better frictional contact against the pulley surface, significantly better than most other materials.  I wonder if this is where the misconception that the grain is stronger than the flesh got started?  

[TinkerTailor]

40 minutes ago, TonyRV2 said:

I came upon an old reference online that was written in the 1880's that involved the use of leather belts being used to drive pulleys.  The article talked about both the tensile strength (stretching forces) and compression forces working on a belt as it drove a pulley system.  The compression forces, the article claimed are negligible and do not harm the leather.  These forces existed on the inside of the belt as the belt turned directly against the pulley.  As the belt travels in between the pulleys it undergoes tensile forces, and this is where the article place most of the emphasis.  The author referred to a test in which the leather was split and then subjected to testing.  The grain side ripped at a force of 468lbs while the flesh side was able to reach around 770lbs.  So it would seem when it comes to tensile strength at least, that the flesh is much stronger than the grain.  I found it noteworthy that the grain side should always be against the pulley since it provided a much better frictional contact against the pulley surface, significantly better than most other materials.  I wonder if this is where the misconception that the grain is stronger than the flesh got started?  

Do you have a link for that reference? i would like to add it to my library./

I looked ain a bunch of books for the section i remembered reading on drive belting, but I could not find it. I have read that they shaved/sanded/buffed the grain off when they layered skived hides to make thicker heavy duty drive belting. They would arrange  them like a deck of spread out playing cards, with the hides half overlapped to get more thickness. The glue joint was not as strong grain to flesh as it was flesh to flesh, hence the removal of the grain.

Also, as to the original question, Leather belting was never stitched only glued. The sections of belt were joined with stitching or clips, but the pieces are way longer than a hide is. The individual hides were glued together. I am sure if glue worked good enough here, it will hold up the that dirty hairy gun on yer belt

I also have a few scientific journals that talk about leather tensile strength from the early 1900s but they are way too dry to read right now......

[JLSleather]

59 minutes ago, TonyRV2 said:

The compression forces, the article claimed are negligible and do not harm the leather.  These forces existed on the inside of the belt as the belt turned directly against the pulley.  

Your conclusion seems backwards.  The compression forces are "negligible" damage to the grain (pulley) side due to the flesh side's lack of resistance to stretch.  In short, the outside stretches more, so there is less compression of the inner radius fibers.  Or, to say the same thing another way, the grain side is less prone to stretch (increasing the compression if you put it on the outside).

We've all known about this for a good while.  Making a belt?  Then most know that you need to moisten the grain of the leather to make the bend.  BUT, the sueded side is bent all the time with no apparent damage -- apparent the key word here.

Basically, the test you quote confirms that the grain layer is "stronger" (less likely to separate willingly).

[TinkerTailor]

3 minutes ago, JLSleather said:

Your conclusion seems backwards.  The compression forces are "negligible" damage to the grain (pulley) side due to the flesh side's lack of resistance to stretch.  In short, the outside stretches more, so there is less compression of the inner radius fibers.  Or, to say the same thing another way, the grain side is less prone to stretch (increasing the compression if you put it on the outside).

We've all known about this for a good while.  Making a belt?  Then most know that you need to moisten the grain of the leather to make the bend.  BUT, the sueded side is bent all the time with no apparent damage -- apparent the key word here.

Basically, the test you quote confirms that the grain layer is "stronger" (less likely to separate willingly).

I think it was more in reference to the forces/damage flexing the belt  when going around the pulley being negligable compared to the forces lengthwise on the belt causing it to stretch. The grain has some effect on the belts longevity going around a pulley, and resisting bending damage, due to it holding the fibers tight while bending. The grain has much less effect on tensile strength because the flesh is the stronger part in this aspect as well it constitutes a greater portion of the thickness of the hide. I would imagine the treatments applied to the belting during tanning and manufacture have a much bigger influence on the ability of the belt to resist stretch and bending damage than the existence of grain.