610 TRANSACTIONS OF THE 



By a gear somewhat more complex I have made a cut off varia- 

 ble from nothing to full stroke, with concentrated movements at 

 both ends of the lever. This gives the most perfect power of re- 

 tarding, by admitting steam in reverse for any portion of the 

 stroke, I do not propose this for locomotives, which should not 

 adopt anything that may be of doubtful stability; but for steam 

 carriages, that would suifer but little from a derangement on the 

 road, and that should be made as light as possible. I consider 

 this the one to be ultimately adopted. It moves the valve by two 

 steps, each as quick as is desired; it retains the steam until the 

 last, and yet has the exhaust wide open at the end of the stroke; 

 it admits steam just when the crank has passed the space in which 

 its leverage is insufficient to overcome the friction on the jour- 

 nals; it then opens the port widely in an instant, however short 

 the admission; and it cuts off suddenly, without wire moving. 

 And its movements, with equal fitting of joints, is smoother than 

 those of a common eccentric, because whatever looseness exists is 

 closed up while the motion is too slow to produce concussion. 

 It will cost considerably more than the simpler apparatus; but it 

 will save steam, weight of boiler, water and fuel; and every pound 

 saved is equal to. saving 150 tons carried one mile, equal to ten 

 dollars at least. 



A comparison of the simplest form of this, the half stroke cut 

 off, with the distribution of the link, will show that it is worthy 

 of the attention of locomotive builders. 



Taking the 6th notch of Agers' link motion, in which the ad- 

 mission is about 51 of the stroke, we find the steam released at 

 19.25 inches, or 2.75 inches before the end of the stroke, and the 

 steam expanded to 1.73 times its initial volume. The steam port, 

 wdiich in full gear opens 1| inches, in this notch opens only 

 9.16ths. If I set my slide block in the link so as to give the same 

 proportion of opening, I sliall cut off a little earlier three half 

 strokes; and, as I do not release the steam until very near the end 

 of the stroke, I shall expand the steam to at least double its ini- 

 tial volume. But I deem it better to give a wider opening, 

 three-fourths of the width of the steam port, and this admits steam 

 during .52 of the stroke, and expands it to 1.92 of its initial vol- 

 ume. Now the work done by the steam during its expansion to 

 1.73 is .55 of its initial work; and the work alone during its ex- 

 pansion to 1.92 is .65 of its initial work; or the effect is as 1.55 

 to 1.65, or upwards of 6 per cent greater with my cut-off than with 

 the link at half stroke, besides the advantage of a wider and more 

 sudden opening. ' 



