Please login in order to download photos in full size
If you are not registered, please register for free: www.Free-Photos.biz/register
Please note to download premium images you also need to join as a free member..
You can also save the photos without the registration - but only in small and average sizes, and some of them will have the site's watermark. Please simply click your right mouse button and save the image.
Please login in order to like photos
If you are not registered, please register for free:
Sorry, non-members can download up to 100 full-size photos per month.
It looks like you have used up your limit.
Free members can download an unlimited number of full-size photos - including the premium free photos.
Join as a member today for FREE! - and download the images without limitations:
You can also save the images without the membership - but only in small and average sizes, and some of them may have the site's watermark. Please simply click your right mouse button and save the image.
English: Lord Kelvin patented this brake in 1858. It consists of a rope or cord wrapped round the circumference of a rotating wheel, to one end of which is applied a regulated force, the other end being fixed to a spring balance. The ropes are spaced laterally by the blocks B, B, B, B, which also serve to prevent them from slipping sideways. When the wheel is turning in the direction indicated, the forces holding the band still are W, and p, the observed pull on the spring balance. Both these forces usually act at the same radius R, the distance from the axis to the centre line of the rope, in which case the torque T is (W ? p)R, and consequently the brake horse-power is [(W ? p)R × 2?N] / 33,000. When ? changes the weight W rises or falls against the action of the spring balance until a stable condition of running is obtained. The ratio W/p is given by e??, where e = 2.718; ? is the coefficient of friction and ? the angle, measured in radians, subtended by the arc of contact between the rope and the wheel. In fig. 2 ? = 2?. The ratio W/p increases very rapidly as ? is increased, and therefore, by making ? sufficiently large, p may conveniently be made a small fraction of W, thereby rendering errors of observation of the spring balance negligible. Thus this kind of brake, though cheap to make, is, when ? is large enough, an exceedingly accurate measuring instrument, readily applied and easily controlled. It has come into very general use in recent years, and had (by 1911) practically superseded the older forms of block brakes.
|Source||Encyclopædia Britannica, 1911|
|Author||Encyclopædia Britannica, Volume 8, Slice 9., available freely at Project Gutenberg|
|This image comes from the 12th edition of the Encyclopædia Britannica or earlier. The copyrights for that book have expired and this image is in the public domain.||
|This image comes from the Project Gutenberg archives. This is an image that has come from a book or document for which the American copyright has expired and this image is in the public domain in the United States and possibly other countries.
Note: Not all works on Project Gutenberg are in the public domain. Some public domain works may have trademark restrictions where all references to the Project Gutenberg must be removed unless the following text is prominently displayed according to The Full Project Gutenberg License in Legalese (normative):
This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.net
All photos in average size can be saved by everyone without registration (by right-clicking) - and all photos can be downloaded in full-size and without the big watermark by members (by left-clicking) (registration and free membership required).
While the copyright and licensing information supplied for each photo is believed to be accurate, Free-Photos.biz does not provide any warranty regarding the copyright status or correctness of licensing terms. If you decide to reuse the images from Free-Photos.biz, you should verify the copyright status of each image just as you would when obtaining images from other sources.
The use of depictions of living or deceased persons may be restricted in some jurisdictions by laws regarding personality rights. Such images are exhibited at Free-Photos.biz as works of art that serve higher artistic interests.