Compass with knife attachment?

I would  try a compass that allows you to add a knife (or make one). Or check out your local arts and craft stores to see if they have a large enough circle cutter for scrapbooking?

Or find something that has a similar radius and use it as a guide. I've used dinner plates before to create large diameter circles out of stryene.

Take a cheap or free wooden yardstic.

Drill one hole to just fit a nail on the 1 inch mark.  Drill a second hole just big enough to fit a # 11 Exacto blade or a scapel if you prefer.  Anchor your styrene so it can't move.  Anchor the yardstick with the nail exactly 24 inches from the styrene.  Then you have a compass that can move as needed to scribe a circle 24 inches in radius. 

cutting curves

   Styrene is not very brittle so is okay to cut it with a coping saw or you can use a hacksaw if the curve is not too sharp. If you are using a knife it's easier to cut thicker styrene with a sheet rock type utility knife than an exacto knife. The larger handle makes it easier to apply more pressure. If you think your curve cut will be a bit ragged you can cut it a bit oversize and file or sand it smooth to the line......DaveB

Thanks for the suggestions,

Thanks for the suggestions, gentlemen!

Score and snap

Remember you don't have to cut all the way through. So use a Stanley knife as DaveB said, so you can apply decent pressure for a good score line then snap it. Run some sand paper across the edge and done.

What about:

Combine DaveB and Yaron's suggestions. Use a straight edge to score and snap pieces off outside the curve, approximating the curve with a series of straight cord lines outside the desired curve, then sand down to the curve carefully.

Here's another idea: can you bend a thin flat strip of something into a 24" radius without breaking it and make that the vertical edge of the platform? That would give you a nice smooth platform edge, and you could fill in any gaps between the vertical edge and your rough-cut .40 curved platform flat piece with thick plastic cement.

or....

relocate the station to a section of straight track...

How about a hot knife?

Bernd

Broken #11 blade

I find that by using a #11 blade that the tip has broken off square and scoring the styrene with the blade held in reverse, you actually "remove" the material rather than "push it aside" and will make a cleaner cut.  I know MicroMark sells a tool like this but this method seems to work well also.

I find these will cut it

I find these will cut it perfect, just like cutting paper. Not sure what they are called but they work.
 

Brilliant!

The idea of turning a soldering iron into a hot knife is brilliant!

Heavy scissors

Dale, will those cut through .040 styrene?

Yes they do

Yes, those shears cut through .040 like construction paper.

If you would like to see a demonstration I can post a short video later today or tomorrow 

Video

Dale, I'd appreciate that, thanks.  Do you know exactly what they're called?

Trauma Shears

Here you go.

https://www.amazon.com/s?k=trauma+sheers&hvadid=77859219276346&hvbmt=be&hvdev=c&hvqmt=e&tag=mh0b-20&ref=pd_sl_2tlgvt55r4_e

Bernd

DSteckler, I have seen

DSteckler,

I have seen orderlies use them way back in the 80s in the Emergency department to cut off the clothes on patients. I had a pair or two when I worked in an OR. I used to make bets that I could cut a penny in half with them and made a lot of 5 dollar bills because no one believed it could be done; mind you it eventually trashes the scissors. I heard them called many names from bandage to orderly and paramedic scissors. 

Trauma Shear Suggestion

@Bernd- Thank you for the suggestion of using trauma shears. We carried them when I was on a CERT in Arizona and I still keep a couple of pairs in the car first aid kit.  They will cut through just about anything.  I scratch build a lot with styrene and will have to give it a try.

Lou in California

@ Lou

You're welcome Lou. A quick search for medical scissors brought up a picture. 

I think they would make a great addition for metal working too, such as cutting thin brass sheet. I might just get myself a pair.

Bernd

Trauma Shears

Thank you so much!

trauma shears?

For cutting styrene would those have and advantage over tin snips we might already have? ....DaveB 

Trauma shears! Brilliant!

I think they will cut a lot more smoothly than tinsnips, though possibly not better than aircraft snips, but they are really cheap. 
 

I use a plexiglas cutter from the hardware store for straight cuts in heavier styrene. Pull them toward you a couple of times along a straight edge, and snap. They have a hooked end like the broken #11 tool, and it does a great job. 

Trauma shears

I thought of buying aircraft snips but didn't think they would give a fine enough cut.  I ordered trauma shears on Amazon.  Thanks everyone for the assistance!

Trauma shears worked like a charm

Ordered a set on Amazon and they arrived yesterday.  Tried them out and they worked like a charm.  Thanks everyone so much for your advice!