22 inch and 20 inch radius curves and flex track...


L

ledzeppelinfan1

Member
Building a 4x8 next year and I've done so much research that its crazy...I feel like I know how to do almost anything outside of wiring.

I had planned on doing my curves by soldering flex track together straight (about 2ish pieces) and forming the long track around the curve. That was until I just read (suprisingly after all my research) that flex track might have kinking issues on 22 inch radius turns and less. Is this an overblown problem or should I really consider using sectional track for my curves? Is there something else I should know that would make flex track work fine in those tight turns?
 
Flex track can kink on ANY curve...but it depends on how the joint is fashioned. If you are only using a metal joiner, and it's the right one for the job, your kinks will be minimal for really broad curves, say 50"-plus. Below 50" radius, you will see more and more kinking.

So, we, many of us, do solder our flex track lengths when they are laid flat and aligned nicely end-to-end, and many of us use metal joiners soldered to make the strong mechanical joint. However, when you go to fashion the radius, the metal joiner will bind and not go past your first pair of spike-head details on the first tie when the sliding rail tries to do that.

I get around the problem by sliding the sliding end deep into the other length of track. When you bend to the curve, one rail moves one direction. Follow it with the end of rail from the other length of flex, and go about six ties deep. I'll go further often. Now your curve is laid down the centreline, and you can block the track using screws or track nails, or do what I do...track nails near the joints, but just use acrylic latex caulk smeared thinly below the ties and use weight to keep them in place...stacks of magazines, pop cans on their sides laid directly on the rails, soup tins, light bricks....whatever. I even use scrap lengths of 1X2 and set my cordless tools on them for weight.

Once the caulk is set, I press nails or drive a screw tight against the open joint that slides so that the rails are forced nicely to gauge and still touch or very close to touching. I sometimes place a half joiner there, but often I just solder the joint. I remove the holders and see if the gauge holds over the next few days.

Here is a photo showing a quarter joiner on just such a joint. This is a wide curve, 36" to be honest, but there's no reason you can't achieve the same effect on tighter curves. It's now buried deep in my helix, so it's gotta work!!

DSCF1751crres.png
 
So Crandell...essentially...you offset the joints (relieving tension) keeping in mind that any unevenness after the curve is made, can then be cut and evened up as the line continues? Seems like its best to work with the track and improvise as you go...so to speak...working with the track and not against it.
 
Personally I'd go with sectional track for those radius's, just because they're far less work and readily available.
I used it on my last layout for tight curves, it was Atlas track with the end ties replaced for appearances.
I'm seriously considering sectional track for my next helix too.
I have seen flex done much tighter also as Stoker pointed out, if you want to use it try a piece out.
And Crandell that is one spiffy looking joint!
 
Thanks, Rico. Yes, LedZ, one should always be open-minded in this hobby. If you think of it, try it. Don't go by the first attempt, either, if it flops. Try a modification. I work that way, and persistence, intelligence, and some patience pay off. That joint pictured required me to use a jeweler's jig saw with the hair-thin filament blade to saw a joiner in half, sliding it onto two rails first and making the rail ends almost touch. Then, taking a half-joiner and doing the same thing once more. Then, sliding that itty-bitty piece of joiner on one rail end in situ and trying to slide the oncoming end into the other end of that bit of joiner. It took some doing for me, now 61 years old.

One other tip for you, since you are reading, and like all such tips I learned it from another old-timer who makes all his turnouts custom-made to fit where he needs them, it is probably only evident in the photo above once you are alerted to it and can see what I mean. At both rail joints, inner and outer rails, you should get in the habit of using a small mill file to file a bevel (champher in UK) in the inner flange face and on the top tire running surface. Especially on tighter radii will it matter most, and especially on the outer rail because poorly aligned joints will snag the flanges on one or more flanges passing over them due to the axles being forced well outward on the tightest of curves. To help reduce the probability greatly, file the bevels on those two adjacent surfaces. Nothing huge, just enough that you know they'll act as cams to keep the wheels inside the gauge.

Do this also for any turnouts you insert into your trackwork. That means filing six ends of rails, but you get used to it, it doesn't really take all that long, a minute, and you'll have much more reliable track...and playing with the trains.
 
Atlas flex..

G'day all....I'm relatively new to flex track but I love it...It achieves realism like no other sectional track does but.....geez you have to be ready to do a good join.
I ballsed up a couple of times...until I pretty much got it right but I think a good investment are those tracksetter tools..I know Peco make them especially so you can get the track set to the proper curve...even down to 18" I believe.. Until I start on my new layout I've just made a temporary two track layout using some real old Bachmann EZYTRACK...which is a mix of 18" 22" and 26" radius.. My SD40s SD70s , ES44s , Dash 8s and 9s etc seem to handle even 18" okay.
If you're doing a 4x8 though...and if you can squeeze a minimum 22" curves into it....it'd be really handy for sure...As others have said...Good joins not flexing and kinking , even on wide curves is the key...Cheers Rod..
 
Thought I'd go and have a look at Tooter's thread and followed your link. On the 1st page, post#5 is a little yellow 4 wheel trolley (or tram as they're called down under) and as is said, there's a prototype for everything. When I was about 11-12, we went for a couple of Christmas hols (In NZ) to a town on the west coast of the north island called new Plymouth. That model of Tooter's is virtually exact replica of some of the trams that ran on the small system there. We camped at a beach to the north of the town and regularly used them to go in and back. Ran on a single track with passing sidings in a couple of places. I've copied that pic into my pictures folder.
 
ledzeppelinfan1 said:
Is there something else I should know that would make flex track work fine in those tight turns?
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Like Selector I offset the joints so there is always 1 solid rail on one side or the other. I NEVER cut away ties on the ends but cut the "spikes" and put a grove under them. Nothing holds the rail in gauge better than the original ties. As a prior poster noted work with the natural flex/bend of the track rather than fighting it.

Also as Selector said this is much larger than 22" but the same principle applies. I have done curves down to 15" using this method with no kinks. I am acutally a little ashamed of this photo as on the side of the lower joint one can see the solder. For shame. This was on a modular unit is why I didn't worry about it. People who visit train shows never seem to look that close.
flextrackjointcurve.JPG
 
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If you are still thinking of the same sort of layout you were looking at in the other thread, note that concentric 20" and 22" radius curves may cause problems with trains side-swiping. That's why the HO 4X8 layout you referenced earlier is designed with concentric end curves of 19.5" and 22". That track-to-track separation is needed with tight curves.

If you offset the centers of the curves so that you have at least 2.5" track-center-to-track-center at every point, then you can use 20" and 22" radius curves one inside the other.
 
cuyama said:
If you are still thinking of the same sort of layout you were looking at in the other thread, note that concentric 20" and 22" radius curves may cause problems with trains side-swiping. That's why the HO 4X8 layout you referenced earlier is designed with concentric end curves of 19.5" and 22". That track-to-track separation is needed with tight curves.

If you offset the centers of the curves so that you have at least 2.5" track-center-to-track-center at every point, then you can use 20" and 22" radius curves one inside the other.
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Thanks for all the replies guys. After further review, I think I'm going to use sectional on the curves because its so damn easy and flex everywhere else on the layout.

Byron, I was going to go with 22 on the outside and actually run with 18 on the inners. On the left side of the track plan, it wont matter as the two lines do not run parallel to one another, but how is that going to work on the right side?
 
Yes! You CAN use flex track for tight (22" and smaller) radius curves, just as others have said. BUT...I found it much easier to use sectional track. Because of space limitations (the need for aisles between legs of my around-the-wall layout and a center peninsula), I decided that I could not always use 22" radius curves, and for inner tracks, I needed to go tighter. I elected to use Shinohara 20" R sectional Code 100 track in certain return loops. A bit more expensive than Atlas, but Atlas doesn't make 20"R. Where I can, I intermix 22" Atlas, 20" Shino and where necessary 18" and even down to 15". Good luck!
 
ledzeppelinfan1 said:
Byron, I was going to go with 22 on the outside and actually run with 18 on the inners. On the left side of the track plan, it wont matter as the two lines do not run parallel to one another, but how is that going to work on the right side?
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If you keep everything else roughly the same, you'll need a short straight length of track at the apex of the 18" radius curve at the right-hand side. It will look a little odd, since the "double-track" curves will have a different appearance, but it will certainly work. Just be sure to keep at least 2.5" track-center-to-track-center spacing through the curves.
 
cuyama said:
If you keep everything else roughly the same, you'll need a short straight length of track at the apex of the 18" radius curve at the right-hand side. It will look a little odd, since the "double-track" curves will have a different appearance, but it will certainly work. Just be sure to keep at least 2.5" track-center-to-track-center spacing through the curves.
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I certainly dont like the idea of that at all. Would getting some of the Shinohara 20" work better for that inner curve? I certainly dont want it to look even a little strange. What did you mean by 'offsetting' the centers of the curves in your earlier response?
 
Stoker said:
If you want to avoid funky transitions in concentric curves when using sectional track the obvious solution is to use flex track and bend it to the exact radius you need and be done with it. I have done both recently and I can tell you that it is definitely easier to get a smooth curve with flex than sections. With sections the tiniest bit of mis-alignment between each piece causes a tiny bump. This means both vertically and horizontally along the curve. These tiny bumps add up. If you pre-solder flex and then bend it to fit the desired radius it should be 100% smooth every time.
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And just like that you've swung me back towards the flex track. I will use sectional for the outside curve and flex for the inner curves. So I'm going with a combo...lol...or is that bad too!?!?!
 
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