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Difficulty with flexible track

Started by donone, November 07, 2008, 03:17:17 PM

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donone

I have placed 4 pieces of Peco SetTrack ST12 as a semicircle (radius 228mm 45 deg each) the end angles are 90 deg.
I wish to emulate this with flex and so placed the flex on top and set the ends to 90 deg and dragged the adjusters at 270 deg to match the half circle. It didn't get rid of the red warnings even though the minimum is set to 220mm.
I further noted that although the curve looked precisely on top of the SetTrack, one end didn't look like 90 deg so I reset it. This rotated the track slightly so that the other end was now out. ad infinitum, I couldn't anchor one end while adjusting the other, which I thought was cured in this issue 3.16.1 (I could be mistaken) or it is due to something else.

It 'appears' as if the length has been set by the other actions and then when changing the angle at the end, the length no longer changes to accommodate (or something like that).
May I have some advice please?

Also please, why am I getting the red warnings (not length)?
You only stop learning when you die.
Sometimes I think I am dead.

David

To create perfect curves, you can use the 'Curve flex' tool, that you can find when you right click the flex to get the pop up menu, select 'Adjust flex', then 'Curve flex'.

Here, you can fill out your values: 90 degrees, radius 22.8.

However, this radius will not be accepted. If you shape the curve manually, you get warnings, just like you said.

The curve is too tight, compared to the default minimum radius of 36 centimeters.

To change this, go to 'Tools/Options' and select the flex tab.
Here, set the minimum radius to 22.8. Next, try to create the curve with the 'Curve flex' tool.

This should do the trick.

NOTE: In case you wonder why there are no warnings when you set the minimum radius to 23: the software tries to find the minimum radius by an approximation algorithm. This algorithm allows for some margin to avoid 'false positives'.

David.
David Hoogvorst. Founder and Owner of DRail Software. Creator of AnyRail.

donone

Thank you David; sorry but this is still not quite clear.
I cannot use the curve flex tool because I am producing a semicircle 180 deg not 90, hence the use of SetTrack half circle as a template.
Yes I could do two 90 deg pieces and join them, but I was trying to avoid that. (As you know from another post in Wish List).
As I said, I did not use the default min radius of 36, I used 22 in order to avoid the radius of 22.8 triggering the warning, but it does.
I did achieve it with 2 x 90 deg using curve flex tool, but that wasn't my aim. However I did expect both methods to produce the same result.
I still don't know why one end of the curve didn't remain fixed while I set the end angle to 90 deg.
You only stop learning when you die.
Sometimes I think I am dead.

David

#3
Sorry, I did not read your post well enough...

Let's try again ;)

Setting the angle at an endpoint simply rotates the existing flex. It does not change the form of the flex. It has always been like that. At least nothing has changed regarding this in 3.16.1.

The angle of an endpoint is defined by the control points.The line that you see appearing when you hover a control point is exactly aligned with the endpoint.

This means, that to create a 180 degrees curve, your control points end up forming a rectangle.

It can be mathematically proved that it is impossible to approximate half a circle very well with a Bezier curve (that we use to represent flexes). It is possible though to approximate a quarter of a circle. Hence the max of 90 degrees in the 'Curve flex' tool.

By the way, I would like to warn you to create tight curves like that on your real layout with flex track. My experience is that it is very difficult to lay them well. The result will be much better with the rigid curved pieces if you need a perfect half circle.

If course, your experience may be different.

David.
David Hoogvorst. Founder and Owner of DRail Software. Creator of AnyRail.

donone

Yes, as I said, that to get 90 deg at the end I needed the adjusters to be at 270 deg i.e. the rectangle, but of course it had to be by eye. I didn't realise that setting the dialog to correct the error would not alter the flex shape to then compensate. Fair enough. I think I now fully understand how it works, thank you.

Thank you for the warning, I have not actually laid flexible track and assumed (obviously wrongly) that if it matched the minimum curve of SetTrack all would be well. I have just tried without fixing in any way, and a lot of track comes out of the end to be discarded and also it is quite tight to hold as well as the sleepers not laying well or evenly. I only wanted to avoid as many joins as possible, assuming that more joins means more stopping of the train (using DCC) due to poor connection etc.
Maybe track could be soldered to overcome this, somebody might have a view on this.
Thank you
You only stop learning when you die.
Sometimes I think I am dead.

David

In my experience, the number of joins is hardly noticeable. The best thing is to wire your track every few meters, and not rely on the track itself too much to reach the far ends of your layout.

My own H0 layout is completely computer controlled, so I need occupancy detection every few meters. This means that I needed to wire the track on a lot of places anyway, and that I needed to cut flex track that was already in place to put the isolations in.

On my layout, the maximum length of a section is maybe 5 meters. In such cases, I feed it in two places about two meters apart. Occupancy detection sections are about 30 cm.

Many people lay cables all around their layout, and feed the track and other equipment from there. Soldering the wires to the track is usually a simple chore.
Personally, I have three main cables that run all around the layout: Brown for mass, Red for 'DCC current', Yellow for 'Ordinary current' to throw switches etc. So the track is connected to Red/Brown (with sometimes an occupancy detector in it), and all switches are connected to Red/Brown for the decoder, and Yellow/Brown for the switch engine.

I really should take a few more recent pictures, but maybe this picture shows the general idea.

Hope this helps a bit.

David.
David Hoogvorst. Founder and Owner of DRail Software. Creator of AnyRail.

donone

Yes thank you David, an excellent set of pictures. I have new faith in SetTrack.
You only stop learning when you die.
Sometimes I think I am dead.