Kadee Bracket Grab Iron Hole Locations

Dennis Storzek
 

As Promised, I have surveyed the mounting holes on a Kadee PS-1 body and have uploaded dimensioned sketches to the FILES section at:

http://groups.yahoo.com/group/STMFC/files/Kadee_PS-1_Grab_Iron_Holes/

All dimensions are decimal inches, to four places where necessary. The ordinate dimensions are relative to the center of the grab iron; it is up to whoever develops a drilling jig to properly relate them to other features on the car body.

The first sheet also shows the typical condition at the mounting pin / hole interface. Whoever devised the old joke about putting a square peg in a round hole obviously didn't design plastic parts, because that is exactly what Kadee has done. The mounting pegs are .017" squares with a long tapered lead; they are designed to be pressed into .020" diameter holes. A look at the drawing shows that this combination yields appx. .002" of interference at the corners of the peg, while the unfilled portions of the hole provide a place for the displaced material.This is good design practice, but it does point out that the grabs must be properly oriented before they are pressed in place; ones the corners dig into the circumference of the hole, it will be either difficult or impossible to twist them straight. If this is a problem, the holes can be increased to .024" diameter, and CA used to fill the gaps and lock the mounting peg in place.

Those who were hoping to use the really fine Kadee boxcar ladders on other projects are going to be disappointed, unless they have a drill that drills rectangular holes. Kadee has chosen, wisely, as far as I'm concerned, to make the mounting pegs rectangular, .024" x .044". This allows a much stronger mounting than round pegs could provide, and ensures that the ladders remain straight, but the difficulty of generating the rectangular slots in a model that wasn't molded with them in place is going to preclude using these ladders on other projects. Because of this, I haven't bothered to post the slot dimensions.

These are indeed wonderful parts. The grab irons and ladder rungs measure just .010" in diameter, smaller than the .012" wire that is commonly used in HO scale for these parts. The minimum diameter for these parts on the prototype is 5/8", which scales to .007", but some prototype parts are made from larger stock. The Kadee rung scale to just a bit larger than 7/8", not far from the mark.

Dennis Storzek

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