minimum radius for helix

I guess we each develop our own favourite methods of building baseboards. I always seem to move before I complete a layout so I build mine to be rigid enough to be transportable and each section small enough so that I can just move it by myself. The third factor is that I tend to build from whatever timber is available - I gather "offcuts" from other jobs and store them long enough for then to be good and dry. :-) I'll stand by my call for a rigid board with framing under a helix - mine uses threaded rods both inside and outside of the circular track bed to allow for precise height setting and they have to screw into something. The flat board also allowed me to cut out the center for access. That wouldn't have been possible with framing/substructure. My skill at wood-working is about a step above "abysmal" so I plan around achieving what I need within that skill level and in assuring that dimensional errors cancel each other out rather than adding together.

Regards, Greg.P.

In message , Chris Wilson writes

OK, but that's not very solid. You've only got to lean against it, and it lists more than the leaning tower of Pisa!

Err, I would tend to make that baseboard in sections - it would be tough to get out the door in one piece!

Greg.P.

You've already built it? Next time ask for out advice _before_ you start.

I think he was offering rather than asking ...

If it's as unstable as he says it is then he should definitely be asking! :-)

Greg.P.

In message , Gregory Procter writes

Actually, I did make it in sections. The straight bits are 8 feet long by 6 inches wide, braced at the edges by 4 x 1 softwood, and the curved bits are 6 inches wide by whatever radius, by 45 degrees. Everything is twisted appropriately and fixed to the supports by means of 6mm. diameter threaded rods for micro-adjustments. The biggest problem is the curved sections, because rigid supports are very difficult in the limited space available. I'm going to have to rebuild them when the weather gets better.

See and all will be revealed. Curvature, the reciprocal of radius, is used to simplify the job of surveyors who lay out (full-size) railways, stations etc. Curvature is predominantly American in usage - it is not precise but good enough for most practical purposes.

For the gradients involved in railways, the difference between sin and tan is negligible.

Mark Thornton

Not for the San Francisco Municipal Railway or the Mount Washington Cog Railway (note: NOT Railroad), with gradients of 1:4 or steeper!

In article ,

Phil: do you recall that in Physics lessons when dealing with Optics? - It was always used there as a basis for simplifying the situation 8-)

There's always an exception! ;-)

Like another contributor I have a PhD in mathematics.

Mark Thornton