Help With Cab Roof

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ebtfan
Posts: 135
Joined: Mon Jul 02, 2007 12:10 am
Location: Lancaster, PA

Help With Cab Roof

Post by ebtfan »

I am working on the cab for my 1.5" Pennsylvania K-4 and am asking for any techniques any of you have used to make and mount a cab roof. I am planning to use 16 gauge steel. The roof will have an opening to access the throttle, valves, etc on the back head. Do you cut the opening in the cab roof before or after rolling? The roof has multiple radii(tighter radius as it approaches the outside edge). Do you approximate the size before rolling then trim to fit or start with a piece that you have calculated will be the proper close fit with no trimming required? I have been using cardboard templates but have not had luck using them for an exact fit as I am looking for a fit within a few thousands of an inch. I am using 1/16 copper rivets to attach the roof. I have made a 1/4" thick steel plate to use to form the radius in the brass angle that will be used in the cab construction. My main question deals with making the roof to the proper shape with a good fit where it meets the cab sides. Thanks much in advance for any help.
Dan
KarlKobel
Posts: 161
Joined: Sun Mar 31, 2013 9:53 pm

Re: Help With Cab Roof

Post by KarlKobel »

Dan,

I thought I had some pictures, but a search didn't come up with them.

My cab roof is similar (called Gambrel).
I modeled the whole cab in CAD which allowed me to check the fit and then produce a flat drawing.
For the shapes, I underlayed the line drawings of the locomotive I was modeling.
I rolled the whole piece in the major radius and made a crude die set for the bending press for the edges.

The cab parts are all screwed to a frame so I can dismantle any of the parts (very necessary, trust me).
I used round head screws so they 'sort of' match the decorative rivets.

Karl
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Fender
Posts: 3084
Joined: Wed May 02, 2007 8:33 pm
Location: Chattanooga TN

Re: Help With Cab Roof

Post by Fender »

The way I did my cab roof was to roll the main radius in the roller, then put the sharper curves in the edges using an arbor press, pressing the roof between a length of round bar stock and a piece of angle iron. I would leave an extra inch or two of the stock for the roof at each end, because the roller won’t curve the sheet all the way to the edge. Then trim the excess afterwards.
Also, it’s usually easier to cut the holes after the roof is shaped, so you can get the holes in the exact location.
Dan Watson
Chattanooga, TN
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NP317
Posts: 4557
Joined: Tue Jun 24, 2014 2:57 pm
Location: Northern Oregon, USA

Re: Help With Cab Roof

Post by NP317 »

I followed the same procedures as Fender.
Getting the correct outer radii was painstaking, but worth the careful effort.
RussN
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