# Leather belt stretching



## Shopsweeper (Jun 26, 2020)

I have been asked to help make up a 3" leather drive belt for a friend (steam egine to power hammer).  I have tanned hides and I am about to start making up a belt.

My Machinery's Handbook (V1, 1914 P704-708) quotes US Navy specifications and states that both the hide and the completed belting should be stretched.  

My question:
*Stretch wet or dry?*
Sub question:
Water or alcohol+water?

My plan is to suspend the belting strips (pre-make up) from my shop rafters with clamps and weights.  After jointing I will streatch the belts in some similar way using 2 bars.


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## benmychree (Jun 26, 2020)

I do not see a lot of success coming out of this project, even new commercially made leather belts stretch, and have to be shortened and re laced several times after being installed; much more practical are canvas/rubber belts, especially in damp locations.  Good leather belts will transmit more power than rubber/canvas belts, but cost a good deal more.  I do know a good deal about belting, having owned my first commercial machine shop driven by line shafting, and also volunteering at a steam powered sawmill that is all belt driven from a 30 HP steam engine;  Google "sturgeon's mill" It is located near Sebastopol Ca. and before the virus, was open to the public in full operation four weekends during the good weather season.


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## Shopsweeper (Jun 26, 2020)

benmeychree, I think you are suggesting that leather is a bad idea - and I appreciate the input.   I have seen lots of people lacing up multiple serpentine (or Poly-V) belts online.  I will say that this project is privatly funded, and at over $5 an INCH, a McMaster Carr's 3" poly belt would be approaching $750.  I am willing to put up with some sweat equity for 7 bills.  Please consider your hard-earned advise carefully listened to and do not be insulted if I go my own way before failure and enlightenment take hold.

This is not my first drive belt, but it would surely be the biggest one I have ever made (by far).  My grandfather taught me how to lace them but I have metal lacing and clamps that I normally use these days instead of rawhide.  I have spliced leather belts with both hide glue and cement and I cannot tell a difference as long as the hide glue was allowed to set hot/warm (hide glue in leather that cools too fast seems to not grip).  My intention is one lacing and several lap-splices (depending on how long of strips I can harvest from the center of my cured hides).  The lacing would allow for take-up as the belt stretches (cut on end, re-lace).  The last belt I did (a blower for a forge in my shop) stretched almost 20% and I "solved" this with a swinging motor mount and good old gravity.  I suspect (based on reading below) that some % of that streatch would have been avoided by a pre-stretch; hence my question above.

I would love to hear form anyone who has pre-streatched a leather drive belt and if they have done so wet or dry.  My reading indicates that when you do not pre-streatch a belt it will require several re-sizings in the first few days of operation.  Some nice old fellow named Fred W. Taylor indicated that you can avoid many of these resizes with a pre-streatch ("A nine years' experiment on belting").  The NS Navy and Machinery's Handbook agree going so far as to cite Mr. Taylor in the case of the later.  The Navy suggests that you streatch both the hide strips AND every manufactured leather belt before installation (or they did in the 1800s).

"All leather is to be stretched 6 inches in the lengthwise direction of the butt, and not exceed 54 inches after stretching."*
later in same paragraph (p704 M. Handbook 1914):
"Belting to be stretched again after manufacture"


I suspect that any mechanic in the 1800s knew how to streatch a belt and could happily answer my question about wet or dry.  I'm just not as smart as a 19th century mechanic so I am looking for experience before moving forward.  I don't want to damage my belting and I don't want to cause unnecessary take-up splices if I avoid it.

* This 54 inches part is logical once you understand that only leather from the center parts of the hide are used, oriented fore to aft.  The idea is that leather from the neck or posterior would result in lesser strength material.  In those days 48" hides stretched to 54 would be have been the norm for commercial beef cattle (yes, they were not in Texas).


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## benmychree (Jun 26, 2020)

Frederic Winslow Taylor is familiar to me, I have his book "On The Art of Cutting Metals", and also "Shop Management", he and his assistant Maunsel White discovered (accidently) the two stage heat treatment that made high speed steel the revolution that it was, they conducted 26 years of experimentation as to how metal could be removed most efficiently, so speeds, feeds, depth of cut, and shapes of tools could be dictated by management to the workforce, it has been said that he and Frank Gilbreth, time and motion study researcher laid the foundation of America's modern industrial revolution.  Gilbreth, was the father of the "cheaper by the dozen" children.  McMaster is the last place that I would consider buying belting from, although I do use them for hard to find items occasionally.


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## Tim9 (Jun 29, 2020)

Go to a shoe repair shop....and ask the shoe shop owner. Not an employee but preferably the owner. My grandfather, brother, and two of my cousins had shoe repair shops and stretching leather shoes was a fairly common service item. They had all of these wooded shoe stretching clamps....and would spray the shoes with some sort of liquid and then tighten the stretching device. I think it’s an alcohol based liquid.
    Anyway, I’m guessing Pre-stretching the leather belts cuts down on the belt stretching while in service. Tandy leather, shoe leather supply houses, and horse tac & leather saddle shops should also have the answer. Anyone making gun holsters....same process. The leather is wetted and molded to fit the form of the handgun.

Kiwi SELECT Universal Shoe Stretch (2) 7oz https://www.amazon.com/dp/B00QQO0QL2/ref=cm_sw_r_cp_tai_xRB-EbZZ3SQVS


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