Pulleys

All these data were compiled from information provided by PETZL (world leader in acrobatic work) and WICHARD (world leader in Nautical).
-The Size bearings:
The larger the sheave of the pulley, the greater the distance traveled by the rope on the latter is important, and thus the less movement at the pulley axis is large compared to the distance traveled rope.
 
A sheave 60 mm have a circumference of 3.14 x 60 =  188.4 mm .
A sheave 32 mm in circumference will 3,14x 32 =  100.48 mm.
 
So in a tower  block  with a sheave is 32mm has covered 53% (100.48 / 188.4) of distance traveled in a tower  block  with a sheave 60 mm
Warning: this means to map it takes to turn the  pulley  a little more  to get the same level with the same force applied.
The size of  the axis is also important.
An axis of 12 mm will have a circumference of 3.14 x 12 =  37.68 mm
an axis of 15 mm will have a circumference of 3.14 x 15 =  47.1 mm
A  pulley  32 mm with a 15 mm axis will have a ratio of 100.48 / 47.1 =  2.13 
While a  pulley  32 mm with a 12 mm axis will have a ratio of 100.48 / 37.68 =  2.67 
The  pulley  of  32 mm  with pin  12 mm  rope move  2.67 mm   to 1 mm on  the axis, while the  pulley  of  32 mm  with an axis of  15 mm  will move the rope  2.13 mm  to 1 mm on  the spindle.
So it's not just the size of the sheave that counts but the ratio of the size of the sheave on the size of  the central axis of the  pulley
And if  the one compares with  pulley  of  60 mm  with a 12 mm axis is obtained: 188.4 / 4.98 = 37.68 more than double that with a 32 mm sheave and an axis of 15 mm 
The rotation of  the central axis generating friction we must minimize it for better performance. Hence  the interest of having a better ratio:
The  pulley  of  60 mm  with an axis  12 mm  rope move  4.98 mm   to 1 mm from  the axis, while the  pulley  of  32 mm  with an axis of  15 mm  move the rope  2.13 mm  to 1 mm on  the ' axis.

The rope: 

Of the friction on the rope sheave as it generates losses

On a  pulley , the best ratio is to have a rope with a diameter  between   1 / 6th and 1 / 8th the size of the sheave, (beyond the rope does not have enough friction to rotate the sheave the  pulley  and slips it directly, it no longer serves in having a sheave that rotates).  The  ropes are strong and flexible and thus deformable under pressure. Over the line will end more friction and  the crushing of the rope will be reduced  and therefore the yield increase (in the limit of 1/8 of the size of the sheave, otherwise the yield is reduced).Cordage

On a  pulley , the best ratio is to have a rope with a diameter  between   1 / 6th and 1 / 8th the size of the sheave (in addition, the cord has enough friction to rotate the sheave the  pulley  and slips it directly, it no longer serves in having a sheave that rotates).  The  ropes are strong and flexible and thus deformable under pressure.  Over the line will end more friction and  the crushing of the rope will be reduced  and therefore the yield increase (in the limit of 1/8 of the size of the sheave, otherwise the yield is reduced).
If the rope is higher than 1/6 the yield will be reduced.
A sheave 60 so it would take a rope from 10 mm to 8 mm (60/8 = 7.5 does not exist in current rope).
On a sheave 32 mm would require a string of 5 mm to 4 mm (32/6 = 5.3 does not exist).
Small additional point:  the  ropes and  the  sheave will perform better over the throat of the  pulley  will be adapted to the diameter of the rope between a  pulley  grooves to 60 mm with a rope and a 10mm  pulley  60 without grooves (flat) on performance  decrease  of approximately 5% (due to  thecrushing of the rope thus increasing friction.)
The  ball bearings:
There is something for all  the  prices and  the  quality.  The  "best bearings" are  the  SKF, the world leader in working.
The nomenclature of the bearings is always the same whatever the brand
    • the  figures show  the  dimensions
    • If nothing is indicated after  the  figures indicates that  the  bearings are in  the open air
    • ZZ: turnover has anti-dust covers
    • RS: the bearing is sealed
    • C3: High speed bearing
The  ball bearings are made ​​to average speeds of 1,000 to 20,000 revolutions / minute depending on  the  Brooch explosio them .
The  bearings will be more effective than  the  self-lubricating bushings to the usage limit charge. Above the CMU  the  ball will tend to deform. The working principle is to reduce  the  friction by reducing the contact point through the ball (instead of some cm² area is reduced to approximately mm²).
As against a small area of ​​about mm² suffers any charge and will be a limit before deformation reached faster.
The  self-lubricating bushings:
Made of bronze, copper, brass, they have the property not to join (seize) other metals (steel, aluminum).
They will yield reduced compared to ball bearings, but the limits of use of the ball bearing  the  rings will go much higher expense.
(Eg  the  cars are on ball bearings for  the  truck load is too great and the system goes on self-lubricated bushings because the load is too high for balls (except to have balls quadruple volume but this would be more interesting)).

Different performance simulation table  rollers  can be used in slackline.

The following calculations represent a theoretical value, in reality supplied forces vary and are not regular in time.
Please note the total sums of the sheave blocker and is only valid with a referral. Without reference that total is divided by the yield of the blocker.
Taking no competing brand in reference we will base on  the  returns provided by Petzl and Wichard. Please note all  the  brands do not have the same output quality.

Pulley  Petzl ball bearings used as reference:

pulley  sheave minder 51mm 97% yield

pulley  sheave rescue of 38 mm 95% yield

pulley  sheave Prussik 25 mm (axis of 10) 91% yield

Rope blockers as reference:

Protraxion Petzl sheave 38 mm (or  pulley  minder with Machard) yield 95%

Petzl Micro traxion 28 mm (or  pulley  rescue with Machard) 91% yield

Kong Robot 35mm 69% yield

Grigri 2 Petzl 52% yield

Gigi plate 48%

For four pulleys, we take the example of two double blocks put together a multiplier Mooring, additional performance loss is added because of the strings rubbing them on the Equalization of the system for the pulleys remain straight. 


Accept

Slack Mountain uses cookies to offer you an optimal browsing experience, we suggest you to accept their use by clicking on "I agree". More.