[Steam-engine] Belting question?

[Bob Smith]

I always called it "SWAG",  Systematic Wild A..... Guess

but, seriously - - -

There _are_ systematic methods of arriving a an estimate of the length of a
rolled belt -


METHOD 1  --
---------------------

A roll of belting usually takes the form of an annulus i.e., a circle with a
hole in the center (like a donut);

To determine the length of the rolled belting:

1.  Find the area of the annulus.

2.  Divide the area of the annulus by the area per unit length of a sample
of the belt.

For example, I have a roll of belting with an O.D. of  22" and an I.D. of
5".

The area of the annulus formed by the roll is - -  (3.1416 * (22 / 2)^2 ) -
(3.1416 * (5 / 2)^2 ) = 380.133 - 19.635 = 360.50 in sq.

Now the next step depends on determining the _effective_ thickness of the
belt to a reasonable degree of accuracy which, in turn, (as Andy noted)
depends on how tight the belt is rolled, its uniformity, etc., etc., etc.  .
. . .  A reasonable estimate can be made by a) laying the roll on its side
and b) counting the number layers of belting between the I.D. and the O.D.
Now compute the average thickness per layer of belting by dividing the
thickness of the annulus by the number of layers.

In the above example the thickness of the annulus (T) = (O.D - I.D.) / 2 =
8.5 " and I counted 34 layers of belting between the Inside and Outside of
the annulus therefore, the average effective thickness of this belt (t) =
8.5" / 34 = 0.25 "

Finally, I want my result in feet of belting, so  --

The effective area of a foot of belting is length  * thickness = 12 " * 0.25
" = 3 " sq.

So we now have 360.50  " sq.  divided by 3 " sq. giving a length of  120.167
feet or  120' - 2"

Working carefully this method will general produce a result accurate to +/-
10% or better.


METHOD 2 --
-------------------

1.  Cut off a unit length piece of the belting and weigh it accurately.

2.  Weigh the roll of belting.

Now --- weight of the roll divided by the weight of the piece gives a fair
estimate of the total length.

This method over comes errors due to sloppy rolling or poor measurements
but, is more difficult to implement in the field.


    Happy steaming,

        Bob Smith



Andy glines wrote:
> Are you trying to figure out how long a belt is while
> it is still rolled up?  Sounds pretty iffy to me.
> There are variables here.  Belt thickness, how tightly
> its rolled, I.D. , O.D..... You probably better
> stretch it out then measure.   Or, you could use the
> WAG method.
>
> --- Mike Rohrer <wmrohrer at myactv.net> wrote:
>
>> What is the calculation to figure the length of flat
>> belting rolled up?
>>
>> Thanks
>>
>> Mike
>>
>> Mike Rohrer
>>
>> Smithsburg, Maryland USA
>>
>> Collector of Antique Farm Literature
>>
>> Homepage - http://members.myactv.net/~wmrohrer/
>>
>>
> --------------------------------------------------------------------------
--
>> ------------------------------
>>
>> If "ifs" and "buts" were candy and nuts oh what a
>> Christmas we'd have!
>>
>> Willie Rohrer 1917-2000
>>
>>
>
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>
>
> Andy Glines
> Evansville, IN
>
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Robert L. (Bob) Smith
Smith Machine Works, Inc.
9900 Lumlay Road
Richmond, VA 23236   804/745-2608

  bobsmith5 at verizon.net