What you'll need to build a helix

Deck and sub-roadbed

The structural ring the track sits on. Plywood is most common because it accepts screws cleanly and stays flat over long curved spans.

• 3/8 in or 1/2 in cabinet-grade plywood

  Cut into rings. Half-inch is more rigid but eats more clearance per turn.

  Search: 3/8 birch cabinet grade plywood 4x8 sheet

• Hardboard for thinner decks

  Tempered hardboard saves clearance but requires more support to stay flat.

  Search: 1/4 inch tempered hardboard sheet

• Cork or foam roadbed

  Sits between deck and track. Damps sound and gives flange clearance below railhead.

  Search: HO scale cork roadbed bulk roll

Supports and risers

How the helix decks stack vertically. The pattern you pick determines how easy it is to reach in for derailments.

• Threaded rod risers

  1/4 in or 5/16 in threaded rod through each deck, with nuts and fender washers. Lets you fine-tune rise per turn after the fact.

  Search: 1/4-20 threaded rod 36 inch with fender washers and nuts

• Vertical wood risers

  Cut to length blocks of 2x2 or 1x2 hardwood. Rigid, cheap, and not adjustable.

  Search: poplar 1x2 by 36 inch hardwood square

• Cleats and corner blocks

  For attaching deck rings to risers. Glue and screw, not just screw.

  Search: small hardwood corner cleats woodworking

Track and electrical

What goes on top of the deck. Helix track gets a lot of running so quality matters more here than on a yard ladder.

• Flex track

  Code 83 for HO, code 55 for N. Buy enough for your full track length plus 10 percent.

  Search: HO code 83 flex track bulk

• Rail joiners

  Standard joiners on most joints, insulated joiners where you need block boundaries.

  Search: HO rail joiners metal and insulated

• Bus and feeder wire

  14 AWG bus, 20 to 22 AWG feeders to every section of flex. Voltage drop matters more on a helix than on a flat run.

  Search: 14 AWG stranded bus wire DCC

The boring stuff that holds the whole structure together.

• 1-1/4 in coarse drywall or wood screws

  For deck-to-cleat and cleat-to-riser joints.

  Search: number 8 by 1-1/4 inch coarse wood screws bulk

• Yellow wood glue

  Every screwed joint should also be glued. Helix benchwork twists otherwise.

  Search: Titebond II wood glue

• Track nails or caulk

  Latex caulk to bed flex track to roadbed is cleaner than nails and easier to lift if you need to.

  Search: DAP Alex Plus white painters caulk

Layout and measurement

Tools that pay for themselves before the first cut.

• Trammel point or compass jig

  For drawing the deck-ring radii. A pencil and a string is not accurate enough.

  Search: trammel points woodworking pair

• Digital angle gauge

  Verify rise per turn at multiple points around the deck. A consistent grade is the whole game.

  Search: digital angle gauge inclinometer 0.1 degree

• Long level

  48 inch minimum. Use it to verify each deck is flat before stacking the next.

  Search: 48 inch box-beam aluminum level

• Adjustable bar clamps

  For dry-fitting deck rings against cleats before glue and screws go in.

  Search: 24 inch quick-release bar clamps pair

The single most useful thing you can do before committing plywood.

• A workbench grade jig

  Two scrap pieces of plywood, a hinge at one end, and a stack of books under the other. Set it to your planned grade and run your worst-case train and weakest locomotive over it. If they fail there, they will fail in the helix.

  Search: no purchase — built from scrap