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How do I select my helix from the table below?
The table below lists PMR helix solutions which have the vertical rise shown at the top of each column.
- Find the column with your desired vertical rise in the heading row.
- In that column, review the grade options for each radius. Don't go past the maximum radius for your helix footprint. (see Space Required column)
- Click your preferred grade for details of your helix.
What do the blank cells mean?
Blank cells means there is no mathematical solution for a helix with that rise and radius (if there was, PMR would offer it!). This is because of one or more reasons:
- The grade to achieve this rise would be too steep for model railroads.
- The vertical clearance between the rail head and the lower surface of the next loop of the helix would be too low.
Helix Kits - N, 1 track
Helix kits with 16" to 18" of rise, and even number of turns between entry and exit:
Vertical Rise | 16" 406mm | 16 1/4" 413mm | 16 1/2" 419mm | 16 3/4" 425mm | 17" 432mm | 17 1/4" 438mm | 17 1/2" 445mm | 17 3/4" 451mm | 18" 457mm | Space Required (l x w) | ||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Radius | 13.5" 343mm | 3.0% | 30" x 30" | 76cm x 76cm | ||||||||
14.0" 356mm | 2.9% | 31" x 31" | 79cm x 79cm | |||||||||
14.5" 368mm | 3.0% | 2.8% | 32" x 32" | 81cm x 81cm | ||||||||
15.0" 381mm | 2.9% | 3.0% | 2.7% | 33" x 33" | 84cm x 84cm | |||||||
15.5" 394mm | 2.8% | 2.9% | 3.0% | 34" x 34" | 86cm x 86cm | |||||||
16.0" 406mm | 2.7% | 2.8% | 2.9% | 3.0% | 35" x 35" | 89cm x 89cm | ||||||
16.5" 419mm | 2.6% | 2.7% | 2.8% | 2.9% | 36" x 36" | 91cm x 91cm | ||||||
17.0" 432mm | 2.5% | 2.6% | 2.7% | 2.4% | 37" x 37" | 94cm x 94cm | ||||||
17.5" 445mm | 2.9% | 2.5% | 2.6% | 2.7% | 38" x 38" | 97cm x 97cm | ||||||
18.0" 457mm | 2.4% | 2.9% | 2.5% | 2.6% | 39" x 39" | 99cm x 99cm | ||||||
18.5" 470mm | 2.3% | 2.8% | 2.4% | 2.5% | 2.2% | 40" x 40" | 102cm x 102cm | |||||
19.0" 483mm | 2.7% | 2.3% | 2.8% | 2.4% | 2.5% | 41" x 41" | 104cm x 104cm | |||||
19.5" 495mm | 2.6% | 2.2% | 2.7% | 2.3% | 2.8% | 2.4% | 2.1% | 42" x 42" | 107cm x 107cm | |||
20.0" 508mm | 2.6% | 2.2% | 2.7% | 2.3% | 2.8% | 2.4% | 43" x 43" | 109cm x 109cm | ||||
20.5" 521mm | 2.5% | 2.1% | 2.6% | 2.2% | 2.7% | 2.3% | 2.0% | 44" x 44" | 112cm x 112cm | |||
21.0" 533mm | 2.5% | 2.1% | 2.6% | 2.2% | 2.7% | 45" x 45" | 114cm x 114cm | |||||
21.5" 546mm | 2.0% | 2.1% | 2.6% | 2.2% | 1.9% | 46" x 46" | 117cm x 117cm | |||||
22.0" 559mm | 2.3% | 2.0% | 2.5% | 2.1% | 2.6% | 47" x 47" | 119cm x 119cm | |||||
22.5" 572mm | 1.9% | 2.3% | 2.9% | 2.0% | 1.8% | 48" x 48" | 122cm x 122cm | |||||
23.0" 584mm | 2.2% | 2.8% | 1.9% | 2.9% | 2.0% | 2.5% | 49" x 49" | 124cm x 124cm | ||||
23.5" 597mm | 1.8% | 2.2% | 2.8% | 1.9% | 2.3% | 2.9% | 2.0% | 50" x 50" | 127cm x 127cm | |||
24.0" 610mm | 1.8% | 2.2% | 2.8% | 1.9% | 2.9% | 1.7% | 51" x 51" | 130cm x 130cm |