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making radius bend with flextrack

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making radius bend with flextrack
Posted by robdmarch on Monday, October 03, 2011 2:41 PM

Hi everyone, This is going to be my first time laying flextrack (H.O. ) and I was wondering what method is the best and most used for making radius bends whether it is  18" ,22" , 24" , or better. the only thing I could think of was a piece  of string attached to a pencil and nail and measure the string half of whatever the desired measurement and mark the radius that way? I wanted to see if there was a better method out there, jig, or tool before I start.Youre help will be greatly appreciated. Thanks guys !

ROB

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Posted by rrinker on Monday, October 03, 2011 2:57 PM

 String and pencil, or a thin strip of wood with a pivot hole at one end and holes for the pencil at the various radii. A wooden yardstick works well for this. Just rememebr if you drill the pivot hole at the 1" mark, you have to put the pencil at 19" for an 18" radius curve. I used a scrap piece of 1x2 and drilled a hole for it to pivot ont he mounting screw of my tripod, sinc emy layotu is around the walls and most curve centers are in the middle of the floor somewhere. The tripod allows me to place the pivot at the currect location and get it up to a height where the stick pivots smoothly at table level.

 Depending on which brand of track you use, smooth curves following your centerline are pretty eacy - Atlas track is fairly springy and will form smooth curves very easily, while ME needs to be 'walked' into position. Something that can help are products like the Ribbonrail gauges, avaiilable in varios radii. They fit between the rails of the flex track and hold a set curve. If you have easy access to look down from above, standing on a ladder ot something, you might not need them, as you can generally eyeball the curve and make sure you are following your centerlien with no bulges in or out. Likewise for straight areas, if you can get down at the edge and sight along the straight it's pretty obvious to see if you have the track straight or if it wiggles back and forth.

                              --Randy

 


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Posted by selector on Monday, October 03, 2011 2:59 PM

Rob, as long as you keep your central pivot from moving, just decide earlier what radius you want, pinch the string between your fingers and a pencil at that distance, and draw an arc longer on each end so that it goes past the point where the tangents (straights) start again.   Let the flex track form natural easements at the point of tangency as they naturally will, slowly going from curved to straight.

It would help to have this all figured out in a plan so that you won't be faced with a really tight curve when you try to close up your loop, if you are going to have a looped main.

I have what is called a trammel.  I cut a length of cedar lath, or stapping, and drilled a small hole near one end into which I drove a screw.  That is my pivot.  Then starting at 18". and in inch increments from there outward, I drilled countersunk holes into which I could insert the tip of a pencil.   Note that you could make the pivot hole large enough to fit over the mounting screw on a camera tripod head for times when you need both hands free and when your curve is on a table top already supported by legs of a height.  Just find your place for the curve, situate the tripod so that the head is near the eventual center of the circle for that radius, and then fiddle with the tripod's location until you can draw an arc that fits nicely with your plan.

Note that you are the one who must answer your question about which curve is better.   Obviously, if your engines are long, or you have long autoracks or heavyweight passenger cars, curves much under 25" are likely to leave you with problems.  Many HO items are fine with 18" curves, and maybe they're all you have room to make.  What is the situation with you...do you have room for 26" curves? 

Crandell

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Posted by BroadwayLion on Monday, October 03, 2011 3:32 PM

LION of course has his own way of doing things. Since him does not bother with roadbed (it costs money, you know) him uses whatever material he can find in the barn to make a table top. Him cuts the board to a minimum 24" diameter inside curve, and uses a small block of wood to measure an offset to the ties.

In theory each track (LION has a four track mane line) should be of larger diameters. I have found that this is not always the case, so a good case can be made for scribing the curves as described above. The LION tried that, but his pivot moved on him, and so he came up with some weird lines on his table. Mostly the LION just slaps the tracks down so that they will fit, and then tests his biggest cars or locomotives on them to see if they work. If they work, fine, who cares what the radius is. If they do not work pull them up again and rebuild the curves until it will both work AND fit on the table. If that does not work then you have to rebuild the table.

Some say planning is the key to success. LION says: slap down the tracks and eat the planners for lunch.

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Posted by HoosierLine on Monday, October 03, 2011 3:57 PM

Your approach will work fine Rob.  Although not necessary, MicroMark makes a specific tool called a "Rotape" which is a modified tape measure that basically replaces the string.  It's sort of handy to have.

Also, if you are laying flex track you need to plan how you'll handle the joints.  Laid loosely, you'll have a kink in the curve which will cause derailments.  To avoid that, take two pieces of track, connect them in a straight line, solder the joints and THEN bend them.  These are the only railjoiners that I solder.

Lance

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Posted by IRONROOSTER on Monday, October 03, 2011 4:49 PM

Skip the string method.  I always had trouble with getting consistent curves.  The trammel works a lot better.

In addition to making your own you can buy trammel points that fit a yard stick.  You can also make templates.  I use these where the inside of the curve is to the wall and I can't use a trammel.

Enjoy

Paul

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Posted by Doughless on Monday, October 03, 2011 7:01 PM

When trying to lay track with radius that sharp, I think it is easier to just use sectional track.  Its a lot easier to get a consistent curve with flex track when the radius is broader than what you're trying.  However, if you want broad easements between your tight radius and a straight section, you'll probably want to use flex track and use one of the methods suggested.

It also easier or more difficult depending on the brand of flex track you use.  Atlas wants to snap back straight, so you'll be kind of fighting with it to make curves that sharp.  Other brands (I think Micro Engineering) tend to stay put when bent, so it may be easier to use ME for sharper curves.

There is no shame in using sectional track for curves that sharp, but go for flex if you want.

- Douglas

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Posted by CTValleyRR on Monday, October 03, 2011 9:15 PM

I don't know that sectional track is any easier.  Unless you're very careful, you will get kinks in the track.

Personally, I use a cheap yardstick with holes drilled at the 18", 22", and 24" points.  I drill them 1/4", so that they'll take a #2 pencil.  Stick a nail through the "hanger" hole at the end and pound or push it gently into your layout surface, put a pencil in the appropriate hole, and trace your curve.

I have found that, by using latex caulk for an adhesive and scrap lumber and patio pavers to weight the track down while it sets, I don't have problems with things springing back on me.

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Posted by rrinker on Tuesday, October 04, 2011 6:28 PM

 See I think it is EXACTLY the opposite. It is far easier to get a smooth curve with Atlas then with ME, because the Atlas naturally creates a smooth bend. Fasten the beginnign of the curve, maybe a few inched straight, then bend it around at the far end, automatic smooth curve. To get a kink-free curve witht he stiffer track liek ME takes some practice, you have to 'walk' along the curve adjusting the ties so that the curve is smooth and even without havign alternating spots of sharper and genetler radius.

                       --Randy

 


Modeling the Reading Railroad in the 1950's

 

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Posted by Doughless on Tuesday, October 04, 2011 9:19 PM

Randy,

Good point about working with ME track.  I never have used ME and was making an assumption.  I think bending Atlas flex into a sharp radius is a pain, which is why I use sectional track for long 90 degree curves, or 180 degree or longer turnback loops; without easements.  I assume his question was intended for laying a long span.  I just solder 3 or 4 pieces of sectional track together to form a large section to work with, then trim to fit if needed before installing it on the layout.  Fewer joints to kink when installing. and 3 or 4 pieces of sectional track equals 1 piece of flex, but pre-curved consistently.

- Douglas

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Posted by dknelson on Wednesday, October 05, 2011 8:26 AM

I use a trammel to mark the center lines on the subroadbed, and when laying very easily flexed track such as Atlas, that is really about all you need, with special attention where it meets the tangent (I introduce easement curves but that is a bit OT).

As a rule I use adhesive caulk to lay my flex track so I like to "get it right" as (not after) it is being placed on the subroadbed.

For tougher to bend flex track such as Micro Engineering, as well as the P.S.C. brand superelevation flex track, I use the radius templates sold by Ribbonrail (there are actually a number of brands of very similar products)  These are pieces of aluminum milled to HO width and a fixed radius curve.  You run the template through the flex track repeatedly and after a while it "takes" the curve.  But it isn't super precise so for example you may need a 30" radius curve template to end up with a 32 inch radius curve, and so on.  that is why I bought a rather complete set of the Ribbonrail templates.  it also came with several lengths of tangents.  Those tangents are also useful because just as certain brands of flex track are very hard to curve, so are they very hard to make perfectly straight without help.   And the tangent tracks are also useful for Atlas flex track because while it has a natural tendency to straighten out, it is not perfectly straight.

Again the goal with curves is for the track to be flexed and curved just the way I want it BEFORE placing it on the adhesive caulk that secures the track.  But sometimes I need track nails or pins to help out during the track laying process -- once the caulk sets those can be removed.  Sometimes it is a slow process of using the template to create a curve, using a track nail to secure the track in place and continuing down the line.  You have a little time to work the caulk but not alot so you learn to pace yourself and not put down caulk when you won't be getting to the track.

Again this OT but the brands of track that are very hard to flex -- if you use the Ribbonrail curve templates to create a "hard" curve I find I can take the track outside for painting and weathering before laying the track.  That avoids getting paint around the actual layout area except for small touch up areas.

Dave Nelson

 

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Posted by St Francis Consolidated RR on Tuesday, October 11, 2011 11:55 AM

    I'm not trying to be a smart-aleck, but isn't the point of using flex track that you DON'T have to follow exactly geometrical radii? That way you can make curves look more like most real railroads, which I think adapt to the lay of the land and not to geometrical design.

   I could be wrong about real railroads, but I think curves on model railroads are more interesting if they aren't geometrically perfect. (And, by the way, I'm not sure if figuring radii is a form of math, geometry, trigonometry or what, but I hope you get what I'm saying!!)

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Posted by richhotrain on Tuesday, October 11, 2011 2:53 PM

A company called Ribbonrail makes metal templates in 5 inch and 10 inch lengths that fit between the rails to shape the curves.  These templates come in various radii from 15" to 48".

Rich

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Posted by fender777 on Tuesday, October 11, 2011 3:08 PM

Also when using flex track.Solder 2 36in section togeather by cutting out the ties where the 2 meet enough so the ties to not hamper the bending.Then replace ties after laying.This is if your making large curves.Bob

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Posted by dknelson on Tuesday, October 11, 2011 8:39 PM

St Francis Consolidated RR

    I'm not trying to be a smart-aleck, but isn't the point of using flex track that you DON'T have to follow exactly geometrical radii? That way you can make curves look more like most real railroads, which I think adapt to the lay of the land and not to geometrical design.   

To a certain extent I agree.  For a meandering short line dodging water and rock and the like, for sure.  Ditto for certain spurs.  But on my mainline class 1 prototype, the area I model was in fact mostly a tangent -- and thus my curves are reluctant concessions to the fact that my house is not infinitely long or wide.  For the two primary curves therefore it made the most sense, and was most efficent in terms of preserving tangents to the highest extent, to settle on a fixed radius curve.  Again as my prior post mentions I do use spiral easement curves where the curve meets the tangent, and again that is a topic in and of itself.  Suffice to say that prototype roads were very mindful of the proper degree of curve for equipment, maximum speed, geographic features and the like, because timetable instructions to crewmen needed to be exact about this  -- and other than easement curves many prototype railroad engineering staffs would in fact use more or less exact degree curvatures. 

Dave Nelson

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Posted by St Francis Consolidated RR on Wednesday, October 12, 2011 7:07 AM

dknelson

 

 St Francis Consolidated RR:

 

    I'm not trying to be a smart-aleck, but isn't the point of using flex track that you DON'T have to follow exactly geometrical radii? That way you can make curves look more like most real railroads, which I think adapt to the lay of the land and not to geometrical design.   

 

 

To a certain extent I agree.  For a meandering short line dodging water and rock and the like, for sure.  Ditto for certain spurs.  But on my mainline class 1 prototype, the area I model was in fact mostly a tangent -- and thus my curves are reluctant concessions to the fact that my house is not infinitely long or wide.  For the two primary curves therefore it made the most sense, and was most efficent in terms of preserving tangents to the highest extent, to settle on a fixed radius curve.  Again as my prior post mentions I do use spiral easement curves where the curve meets the tangent, and again that is a topic in and of itself.  Suffice to say that prototype roads were very mindful of the proper degree of curve for equipment, maximum speed, geographic features and the like, because timetable instructions to crewmen needed to be exact about this  -- and other than easement curves many prototype railroad engineering staffs would in fact use more or less exact degree curvatures. 

Dave Nelson

   Thanks for the insight, Dave. Makes a lot of sense.....my limited personal observations are with our mountains in Colorado here and in the city, where blowing up mountainsides to make life easier on railroads isn't always feasible, and in the city where you have buildings and other people's property to deal with. I guess I need to get out more! I've never seen a great big curve out where there's a lot of room.

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Posted by Doughless on Wednesday, October 12, 2011 6:41 PM

St Francis Consolidated RR

    I'm not trying to be a smart-aleck, but isn't the point of using flex track that you DON'T have to follow exactly geometrical radii?

That was sort of my observation about the original post, especially as it pertains to the sharp radii he was talking about, 18, 22, or 24 (he did offer "or better").  If you want exactly geometrical (sharp) radii, there are ways to accomplish that other than using flex track.  He could even combine sectional track of incrementally sharper radii like a 24, 22, 18, 18, 18, 22, and a 24 combination to make it less geometrically consistent and kind of achieve a poor man's spiral easement thingy. 

Beyond (or better) a 24 inch radii, he will need to use flex track, in which case the methods suggested for laying it become more relevant, IMO.

- Douglas

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Posted by richhotrain on Thursday, October 13, 2011 5:35 AM

Doughless

Beyond (or better) a 24 inch radii, he will need to use flex track, in which case the methods suggested for laying it become more relevant, IMO.

Not necessarily.  The Walthers web site shows Shinohara Track in curved sections up to 36" radius in Code 100.

Rich

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Posted by CharlieM90 on Thursday, October 13, 2011 9:03 AM

robdmarch

Hi everyone, This is going to be my first time laying flextrack (H.O. ) and I was wondering what method is the best and most used for making radius bends whether it is  18" ,22" , 24" , or better. the only thing I could think of was a piece  of string attached to a pencil and nail and measure the string half of whatever the desired measurement and mark the radius that way?

 

Just a caveat. That method will work. But when you're tensioning the string while drawing, it will tend to stretch and throw your radius off.

Try using something more solid (like a small chain?). Won't stretch and will give you consistent results.

 

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Posted by Phoebe Vet on Thursday, October 13, 2011 9:14 AM

I second the motion about using a chain or a yardstick with holes.

String is too flexible.

Dave

Lackawanna Route of the Phoebe Snow

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Posted by Doughless on Thursday, October 13, 2011 7:58 PM

richhotrain

 Doughless:

Beyond (or better) a 24 inch radii, he will need to use flex track, in which case the methods suggested for laying it become more relevant, IMO.

 

Not necessarily.  The Walthers web site shows Shinohara Track in curved sections up to 36" radius in Code 100.

Rich

Yippie!  Now I can make broad geometrically consistent curves as easily as I make sharp ones.

- Douglas

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Posted by Steven Otte on Friday, October 14, 2011 11:26 AM

Hi, Rob,

To help me plot curves on my home layout, I used the string method to mark four semicircles on cardboard at four different radii. I then cut them out along those curves to make two templates. The innermost curve on the first template is 16" radius plus half the width of track gauge, so I can snug the curve up against the outside of the flextrack to get the 16" curve I want. The outside curve is 20" minus half gauge, so I can get a 20" curve by snugging the template up against the inside of the track. The other template is likewise sized for 18" and 22" curves. I tend to curve my easements by eye, but having these templates handy lets me make sure that my track doesn't exceed my minimum radii, and it also helps me eyeball where a curve will or won't fit.

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Posted by nearboston on Monday, March 28, 2016 2:40 PM
Flex Track has one stationary rail and one that slides, allowing it to bend easily. When bending the Flex Track into the desired shape, you must keep in mind that the sliding rail must always be on the inside of the curve (closest to the center of your layout plan).
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Posted by riogrande5761 on Tuesday, March 29, 2016 10:40 AM

Steven Otte

Hi, Rob,

To help me plot curves on my home layout, I used the string method to mark four semicircles on cardboard at four different radii. I then cut them out along those curves to make two templates. The innermost curve on the first template is 16" radius plus half the width of track gauge, so I can snug the curve up against the outside of the flextrack to get the 16" curve I want. The outside curve is 20" minus half gauge, so I can get a 20" curve by snugging the template up against the inside of the track. The other template is likewise sized for 18" and 22" curves. I tend to curve my easements by eye, but having these templates handy lets me make sure that my track doesn't exceed my minimum radii, and it also helps me eyeball where a curve will or won't fit.

String or trammel (I use a home made trammel), both require a fixed point to attach to - which is the trick.  In many cases I have to fix a board to the layout temporarily and strategically so I can attach my trammel (or your string) to make to plot the curve center line.

As for easements, draw my curve centerlines so that they intersect the tangent with an offset of about a half inch (using John Armstrongs table in Track Planning for Realistic Operation on Easements); then I make marks into the curve and the tangent at the distance recommended my John A.  I like the springy Atlas flex because it will naturally "spring" and bend to the easement by tacking it down on the centerline of the tangent and then "spring away through the mark on the offset and then gradually into and onto the curve centerline at the mark where it should be "on the curve centerline".  Works great for me.

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Posted by carl425 on Tuesday, March 29, 2016 2:06 PM

riogrande5761
both require a fixed point to attach to - which is the trick.

Got a tripod for your camera?  That's what I use.

But... after 5 years since the question was asked, my bet is that he's figured it out of no longer cares. Smile

I have the right to remain silent.  By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.

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Posted by Lone Wolf and Santa Fe on Tuesday, March 29, 2016 2:08 PM

Sometimes I use sectional track for curves to make sure I don’t cheat and make them to tight. However if you only use sectional track your layout will be too symmetrical. I use flex track as easements which allow the line to flow more naturally. Sometimes I use sectional track as a guide and use a pencil to trace the track onto the roadbed, then replace it with flex track.

The guides which fit between the rails seem like a great idea but I have never tried them.

The string/ruler method only works if you have the room and something to attach it to.

j.......

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Posted by peahrens on Tuesday, March 29, 2016 4:57 PM

I used a yardstick trammel.  Plus curve templates 22-36" that I cut from a brown paper roll.  I used variable curves in several areas.  And included simple easements, not worrying about precision as they are always better than an immediate transition.

Paul

Modeling HO with a transition era UP bent

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Posted by Doughless on Tuesday, March 29, 2016 6:58 PM

They make sectional track in 18, 22, and 24 inch radius curves, and each piece is uniform from one to the next.  If I was to make a perfect half circle of track in one of these tight radii, I wouldn't use flex track, since I don't think its really meant to be bent into tight radii anyway.

I use flex track to make broader curves, or to do what it was designed to do, make a straight line of track unstraight. 

 In making broader continuous curves, the methods discussed work well.

- Douglas

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Posted by sfcouple on Tuesday, March 29, 2016 7:44 PM
I'll second the others who use Ribbon Rail. I use these products whenever I lay flex track and they work extremely well, coming in numerous different radii plus different lengths of straight pieces. Wayne

Modeling HO Freelance Logging Railroad.

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Posted by Doughless on Wednesday, March 30, 2016 3:23 PM

Wow.  I din't notice that I was responding to a five year old thread.  Its nice to see my opinion hasn't changed much in those years.

Its pretty easy to align sectional track.  Then solder the joints.  Perfectly consistent curve all the way through to the very end.

- Douglas

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