|
|
| Re: NYC Minimum Curve Radius (148586) | |||
 |
|||
| Home > SubChat | |||
|
[ Read Responses | Post a New Response | Return to the Index ] |
|
||
|
Re: NYC Minimum Curve Radius |
|
|
Posted by Rail Blue on Sat Oct 1 09:18:59 2005, in response to Re: NYC Minimum Curve Radius, posted by JayZeeBMT on Sat Oct 1 07:52:24 2005. Plus I really did think 89 deg. was decreasing, but I stand corrected...Curve radii are measured in feet (') not degrees (°) - and yes, the symbols are horrendously small superscript blurs to me too! They're radii in the normal sense of the word - the distance from the centre of a cricle or arc to any point on the circumference of that circle or arc. If you can picture the circle and imagine what happens to the tightness of the curvature as you increase or decrease the radius, you've got the concept! OK. But how does truck play and car overhang figure into this? The car body is rigid and effectively a straight line. The trucks are two points along which the entire straight car body pivots as it goes round a curve. Let's take two really absurd examples: 1) 60' car, trucks centred exactly at either end. 2) 60' car, single truck at centre point. In case 1, there is no overhang at beyond the ends of the trucks. Instead, there is a very large overhang in between them. As the car goes round the curve, the middle overhangs the inside of the curve. In case 2, there is no overhang in the middle, but (almost) a 30' overhang at either end. as th car corners, the inside of the curve isn't overhung at all, but the ends wildly overhang the outside of the curve. On a normal transit car, the trucks are usually centred somewhere between the extreme cases, with the ends moving out on curves and the "belly" moving in. Of course, moving the trucks alters how much the overhang is on the inside or on the outside (which can have huge implications on clearances). Generally speaking, if you want to minimise the amount the ends sweep out (to make it easier to walk between cars), you put the trucks nearer the car ends than if you are merely working to weight distributions and clearance envelopes. |
|
|
|