I am new to the hobby and am currently running 2 ovals (O-72 & O - 63 curve) on an 8 x 12 area. I currently don't have any turnouts on my layout. Over the next year I am planning on upgrading my layout space and have been playing around with layout ideas for this new space. I had a few questions about turnouts. What does a #5 and #7.5 turnout mean and when would you use them in a layout? Also if you were running two main lines on your layout and you wanted to have a cross over between them which type of turnout would you commonly use? I currently use Atlas O track. Thank you in advance for your reply.
Without getting too specific, the difference between a #5 and a #7.5 is in how long (in distance) it takes to transition from one route to another. Higher numbers take longer to transition. As a direct result, the higher number switch is actually much larger (in length) than the lower number.
Whether you choose a #5 or a #7.5 to make a crossover between your two loops depends on what type of equipment you run and how slow (or fast) you want to run through the crossover. If you run long equipment (engines and/or cars) and you want to perform high-speed crossovers, the #7.5 is almost mandatory. If you run all short equipment, high-speed crossovers would probably work with #5 switches.
Hope this helps.