Draftsmen and engineers layout the first trestle for the LRRR
Hello,
I have had an interesting several days figuring out the first trestle for the LRRR. I had to compute the degree of grade of this gradually ascending trestle and bridge where it will be able to cross at 12" (best clearance for !:20.3 rolling stock) above the line below which is coming off the mountain as a descending line.
This trestle is on a gradual curve which puts additional stresses on the locomotive and wheel sets (The internet gurus say multiply percent grade X2 for the actual workout a curved grade puts on a locomotive's mechanism. A 2% curved grade is equivalent to a 4% straight line.) The Bachmann Shay can easily pull a 5% grade according to other Internet gurus.
I chose a 1.5% grade as an easy pull( equivalent to about a 3% grade on the straight) that will get me about 13-14 inches of clearance when it crosses the lower line about 300 inches from the cribbing take off.
So here it is in mock up fashion levelled, plumbed and with a 1.5% curved grade. I will take measurements from this mock up to determine the height of the bents on this sloped hill side.
Hope you do not have a headache with all the math.
Doc tom
Hello,
I have had an interesting several days figuring out the first trestle for the LRRR. I had to compute the degree of grade of this gradually ascending trestle and bridge where it will be able to cross at 12" (best clearance for !:20.3 rolling stock) above the line below which is coming off the mountain as a descending line.
This trestle is on a gradual curve which puts additional stresses on the locomotive and wheel sets (The internet gurus say multiply percent grade X2 for the actual workout a curved grade puts on a locomotive's mechanism. A 2% curved grade is equivalent to a 4% straight line.) The Bachmann Shay can easily pull a 5% grade according to other Internet gurus.
I chose a 1.5% grade as an easy pull( equivalent to about a 3% grade on the straight) that will get me about 13-14 inches of clearance when it crosses the lower line about 300 inches from the cribbing take off.
So here it is in mock up fashion levelled, plumbed and with a 1.5% curved grade. I will take measurements from this mock up to determine the height of the bents on this sloped hill side.
Hope you do not have a headache with all the math.
Doc tom
