Building a Helix with PVC Pipe

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beiland

Active Member
#1
I have seen a few discussions of utilizing PVC pipe for sub-roadbed, and this particular one is one of the better ones,...
http://cs.trains.com/mrr/f/88/t/137192.aspx?page=1

photos at that site

Then he made a few modifications....
I will continue thinking outside the box with...

PIPE ROADBED VERSION 2
This is version 2 of the pipe roadbed method.

I used masking tape on the underside of the pipes. Then I added cement between the pipes!!! You don't need to cut all these masonite pieces anymore. Just glue cork roadbed on top of the cement. The cement will not move at all because the round shape of the pipes will no allow it. My cement was not fresh so I got lumps in it. I will try to even out the surface by adding a thin layer of spackle. I think that will be very easy to do because you use the top of the pipes as a support when you even out the spackle. I can asure you that this roadbed will not move in any direction. It must be the strongest roadbed ever... The only thing I need to do is to change the distance between the pipes. It must be a little more when you use cement between the pipes. But I used the same distance in this experiment. Maybe it's possible to join the pipes with smaller pipes instead of wood dowels. Then you can still use the pipes for track power. One cable in each pipe, no visible cables.
photos
So now I'm wondering if portions of this idea are a possibility for constructing a 30" helix structure?.
 
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#2
I have seen a few discussions of utilizing PVC pipe for sub-roadbed, and this particular one is one of the better ones,...
electrolove, Fergie, loathar, tstage, and even Lillen now there are some names that bring back some memories. .... I have electrolove's real e-mail somewhere. If it can find it I'll write and find out how that all ended up. I don't remember what his minimum radius was. I know the original layout was destroyed (in a flood I believe), and don't know if this is the original or a new one.

Just FYI electrolove's layout is one that morphed from a simple idea into an impressive representation of D&RGW through the Colorado mountains. I don't remember if any of his original wants and requirements were left at the end (other than running the California Zephyr train). Each time we did a revision of the plan he liked it better than the first ideas and replaced them with new wants and requirements. Others would comment and we would revise again. As I said the end result was impressive. It makes a good case study on designing a model railroad. If that site wasn't copyrighted to them I would collect all those posts and make it into a book or at least a "how to" article.
 
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beiland

Active Member
#4
Frame Structure for External Helix

A thought occurred to me this morning....

How about a outer hexagonal box frame structure (fabricated out of say 1" or 1.5" square-section alum tubes) into which you would place the coiled up PVC pipe. This frame structure would hold the coiled pipe from expanding outwardly further. And vertical square tubes joining the top and bottom 'hexagons' could be the side supports/attachments for the pvc pipe roadbed at the various levels as it rose in grade.

I'm thinking double pvc tubes for the roadbed as reference above, glued together side by side, with the track laid over the two tubes.

Sure would make a nice open space access to the helix tracks from inside the circular space of the helix structure, since most of the helix support structure is located on the outboard side of the tracks.

??

PS: The frame structure could be fabricated from wood of course, but I chose alum tubes for 2 reasons:
1) I have some already that I salvaged from an old screened in porch structure here in FL
2) I'm looking for materials that are less affected by moisture, humidity, etc ie, alum & pvc
 

NP2626

Active Member
#5
I am pretty mechanically inclined and I really can't grasp what you are describing as made from aluminum square tubing. Do you know how and do you have access to a Heliarc welder for welding up the frame? Being as open as you describe, what's to stop a whole train, loco; or, a few RR cars from falling to the floor in a derailment? I think building a helix from Masonite and/or wood would be far easier to perform. However, if you think your idea has merit, just go for it!
 
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#6
You are saying that all of those fellows experimented with this PVC idea?
No, those are just the old friends and regulars of that board who happen to have contributed to that thread. As far as I know Benny is the only one who actually used the pvc. I did find his e-mail and sent him a note to ask how it came out in the long run.
 

tootnkumin

Well-Known Member
Staff member
#7
Would be interesting to see how, or if this worked out. As only straight sections seemed to have been shown in those forum posts, I wonder how it actually worked on curves, especially on the sort of radii used on layouts. I've got quite a bit of PVC electrical conduit of 1" or less diameter and even that doesn't curve that well without heating. Once you do that the smoothness of the curve becomes problematical. In a helix, you not only have the radius of the curve to contend with, but the twisting of the roadbed as it rises/falls, basically a continuous screwthread shape.
 

beiland

Active Member
#8
electrolove, Fergie, loathar, tstage, and even Lillen now there are some names that bring back some memories. .... I have electrolove's real e-mail somewhere. If it can find it I'll write and find out how that all ended up. I don't remember what his minimum radius was.
It would be interesting to get him involved with this discussion, since he seems to have experimented a lot with some PVC roadbed methods.
It would also be interesting to get some of his photos, and/or permission to use some of his photos of his experiments.
 
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beiland

Active Member
#9
I am pretty mechanically inclined and I really can't grasp what you are describing as made from aluminum square tubing. Do you know how and do you have access to a Heliarc welder for welding up the frame?
I'll give you a little sketch before to long as I work out a few more initial thoughts.

I hope not to have to using welding technics, but rather good old pop-rivet/adhesive joining of the square-tube aluminum extrusions.

Being as open as you describe, what's to stop a whole train, loco; or, a few RR cars from falling to the floor in a derailment?
Haven't worked out those details yet, ...but on many existing helix structures, particularly this built with all-thread rods, what keeps them from letting the trains fall into the opening in the center of the helix? ...just a few all-thread rods?
 
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beiland

Active Member
#10
General Concept

Just to help with visualizing the concept. Lets say you had a 5 foot square by 2 foot deep wooden box that had no top on it.

Now lets coil some 1/2 inch dia PVC pipe into that box without overlapping the pipe upon itself,...the coil will grow in height within the box as we coil an ever-longer piece of PVC tube into that box. The box will force the normally straight tube into a nice 5 foot, (60" diameter circle,...30" radius) within the box. (btw, I have a few sources already that confirm that this PVC tubing could be coiled into as little as 24" radius).

Now lets say we want to keep those coils of PVC tubing from actually lying directly against the wooden inside surface of the box. I think we need to use a few of these spaced evenly around the perimeter of the tubes,....PVC snap saddles
PVC white saddle.jpg
But wait, look at this one, its threaded
sch-40-saddle_1.jpg
We could use this saddle to hold the coiled tube, and bolt the saddle to the side of the wooden box.

Now what if our single PVC tube coil was instead a double tube (two tubes glued together). Its been done before, as a form of spline roadbed.
 
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#11
It would be interesting to get him involved with this discussion, since he seems to have experimented a lot with some PVC roadbed methods.
It would also be interesting to get some of his photos, and/or permission to use some of his photos of his experiments.
I don't think we will get him involved. He doesn't even frequent the other forum anymore so I doubt he would join here. Anyway I did write and asked if this was related to the first layout or the replacement and how the PVC had worked out in the long run. I got a reply, and the answer is he doesn't know yet. :) Years of building bench work and he isn't done. FYI His reply in full follows:
"Hi there, nice to hear from you. Yes i did start over with my layout but that was not because of pvc pipe. It was my benchwork lumber that warped in all directions I have been very busy for a couple of years. I got married and also started my own company. I am still building the benchwork. So i can not tell if pvc pipe is good or bad at this point. But my guess is that it will work with lots of adventages. I am really looking forward to the day my benchwork is finished. Take care."
 

beiland

Active Member
#12
Updated thoughts on Helix Constuction

Has anyone heard of 'flexible plywood'? I was really not very aware of it till a few days ago when a gentleman who had done considerable amount of work on home remodeling and counter-tops showed me a piece of it. It was about 3/8 thick plywood that was constructed in such a manner that it could be bent in an arc, and quite a tight one at that, and then bent back the opposite direction,...quite flexible bending in one plane only.

What if one were to take a 4x8 sheet of this FP and cut it into half, 2 pieces 2'x8'. Place these 2 pieces end to end making a 2'x16' sheet, then bend this into a circle,... 16' x 12”=192”,....that works out to be a circle of diameter 61.14 inches, or a radius on about 30.5”....just what we are looking for our helix track to be.

So this flexible plywood would become our drum housing for the helix structure, and it would be 24' high unless we chose to make it less. In my case this 'cylindrical drum housing' could sit inside my abbreviated alum tube frame that gets attached to the rear exterior wall of my train shed.

Now here is the kind of neat thing. Before this flexible sheet of plywood is rolled up into a cylindrical drum shape, it is laying flat on the floor. At that point a straight line is drawn across its surface to represent the 'grade' of the track of the helix. If we then attach our 'pvc snap saddles' to the plywood backing, along this 'grade-line', and at say 1.5' or 1' intervals along its 16' length, we have then established the supports for the first piece of the pvc tube that will wrap around inside our drum from top to bottom. We have then established a nicely curved (approx 30” radius) roadbed of the exact grade we drew on that flat board.

Coil this flexible plywood up and place it in our alum frame, then coil in that first pvc tube into its saddle supports, let everything line itself up, snug up the fastenings holding the saddles to the drum of plywood, then finally apply the cement to secure the T-shaped saddles to that first 'layer' of pvc tube.

Now we need to make our tubular roadbed a bit wider to accept our HO track. Instead of just 2 tubes wide, I suggest 3 tubes wide. So we lay in two more parallel 'layers' of tube and cement those in. That will allow us to put sideboards on this pvc roadbed to prevent the trains from following off in case of derailment.
 
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beiland

Active Member
#13
There has been an interesting idea suggested on another forum. I felt it needed to be posted here,...along with some additional new thoughts.

WillyP said:
I could envision making the frame of the helix of pvc and I think it would be as easy as wood. Then again, I have zero experience doing such a thing and may not anticipate issues. Of course, that has never stopped me before... ;)

But 1/2" pvc is pretty flexible and I can't imagine it would be difficult to make 3 circles 5' diameter. Use 2" pvc for the vertical legs on the inside of the 5' circles. Maybe 6 or 8 legs to start, easy enough to add more later if needed. A drywall or deck screw through the 1/2" into the 2" should suffice. Put the first 5' circle on the floor and attach legs. Add the second at the lowest track level, and the third at the highest.

Then you can attach roadbed of any kind you want to the inside of the 2" legs. I do know from experience 2" pvc will hold a screw pretty well. If you wanted to use pvc for roadbed maybe use some hose clamps to temporarily position some "L" brackets to lay the 1/2" pvc on then just drive a long deck screw through the 2 pieces of 1/2" into the 2". I think that would be adequate but you could make the "L" brackets permanent if needed.
I like a few of your ideas here WillyP.

The 2" PVC vertical legs would be very strong, and I was already thinking of making it 8 such vertical legs,...an octagon circle. My thoughts drifted to, what might be a squared-shaped alternative to those big round 2" tube-legs, for several reasons:

a) Wouldn't that make it easier to attach those legs to an octagon shaped 'circle structure' at the top and bottom of the helix. In other words those 2 'circle structures' might be build of 8 segments of something like 2x2 wood segments, The square sides of these segments would better mate with square-sided vertical legs.
b) And wouldn't it be a nicer flat-face mate when mounting those L-brackets?

Well I found the PVC square tubes that might be utilized. They exist in the PVC hand-railing business,...
https://azek.com/products/railing
DSCF1162.jpg
DSCF1163.jpg

So there I was pretty satisfied that this just might be a good alternative.

Just for the heck of it I decided to go visit my local metal scrape yard the other day. (to be continued on next posting)
 

beiland

Active Member
#14
Metal Scrapyard goodies

I walked into my local little metal scrap yard, and one of the first things that jumps out at me is they have some alum hand rails that have been scraped. These railings have lots of small box-sectioned 'tubes' that form the multiple uprights. And they appear to be plenty strong to become those up-right legs of the helix structure as mentioned above,....in the place of the 2' dia PVC tube, or the square-tubed PVC.

They are getting ready to put all this scrap alum in a crushing machine,....no please. I grab a bunch of them as could also have other uses for some of them.

I take a few more steps and I discover a big round circular hoop of alum. I suspect it was the outer ring of a glass table at one time. I measure it and its exactly 4 foot in diameter,..(hmm 24" radius). I had been planning on 5 foot dia helix, but perhaps this might do? Here is what I've collected at the moment.
DSCF1153.jpg
DSCF1154.jpg
DSCF1155.jpg
DSCF1152.jpg



Lets see I need to find another one of these circular hoops of alum, or whatever,....or do I ??

I decide to look up where i might find hoops of metal or whatever,...and I run into this greenhouse site. They bend many types to tubes to built their greenhouses.
http://www.hoopbenders.net/home.html
.....there is even a good video of a lady bending these metal tubes
https://www.youtube.com/watch?time_continue=6&v=D2GzR-IOvLw

WOW, now I can built my own metal hoops at the 60" dia I wanted in the first place,...and fabricated from galvanized metal electrical conduit. One hoop for the top, one hoop for the bottom, with the 8 vertical legs attached between the two hoops.
 

beiland

Active Member
#15
Turnout in Helix Track

Is it possible to include a turnout within the helix track structure, without too much concern?

Looking at this diagram I am planning on entering the helix on the lower level from the peninsula area, and then exiting on the upper level along the wall. What I would like to do is insert a turnout at that upper portion such that the train might proceed around the upper deck in either direction. That would provide for a method to have the consist go in a forward direction when both coming up the helix, as well as going down the helix. Just wondering if many have seen turnouts within helix(s)?
Helix Configuration (external).jpg

also
..... I'm also having some heart burn trying to figure out how to enter and exit the helix without doing some sort of crossover or making the layout a really long loop to loop type. Somewhere I remember reading about an offset helix that allowed multiple entries and exits but I can't find the reference, nor did I examine it enough at the time to understand how it worked.
 
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fcwilt

Active Member
#16
It's easy enough to cut 1/4" MDF into arcs of the desired width - 4 (or more) pieces per 360 degrees.

For supports you can use 1x2 (or something similar) and just cut notches to fit the 1/4" MDF (at the appropriate angle). You cut the the needed number of notches at the needed spacing to obtain the desired grade and clearance. Eight pairs of supports, at 45 degree intervals, works well.

I glued all of the MDF pieces together, using small strips of wood spanning the joints, into a "spiral".

Then, with the help of my wife, I fit the supports into place - it was a bit awkward lifting the MDF spiral into place, turn by turn, but it worked out fine.

Frederick
 
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#17
Is it possible to include a turnout within the helix track structure, without too much concern?
I don't know why it wouldn't work. Especially with a curved turnout. I don't see that it would be that much different than putting a turnout coming off any other curve. Just adjust the roadbed under it.
 

beiland

Active Member
#19
Masonite Subroadbed ?

I am still committed to my experiment with the PVC roadbed within the helix structure, BUT...

I have had 2 people on other forums suggest that with my multiple uprights I just might be able to utilize Masonite as the subroadbed material. One fellow says a double layer of Masonite with overlapping circular segments...total thickness 1/4"

Here is another posting I found that I have NOT been able to confirm the actual Masonite construction thickness with,...although it does say "1/8" tempered Masonite laminated together"....
Helix Types
Mon, 2011-01-31 16:52 — Hart Corbett

I have 3 helixes on my HO/HOn3 layout. One is a "standard" one of about 5 turns in HOn3 only. The other two actually are "stacks" of helixes. One stack consists of a 1/2 turn dual gauge helix approached by a long grade. The second multiple turn helix in this stack is HOn3 only, with separate entry and exit points not related to the dual gauge one below. It also is of smaller radius than the one below. The third stack consists of a dual gauge helix twisting downward to a staging yard underneath the main yard, where the main entry is. This main entry also leads to a single twist dual gauge helix on top of the lower one with the exit leading off to a long down grade. This main entry also leads to a third HOn3 only helix of several twists on top of the other two which leads to an HOn3 "high line". All of these helixes are of the same radii.

All the helixes are built of 1/8" tempered Masonite laminated together with carpenter's glue and precut to various diameters. This thinness is needed to minimize the grades. All are supported by threaded rod material using washers and nuts, which allows fine tuning of the grades as needed. To hold the track in place (all track in the helixes is ME flex track), I first tried glue which didn't work because of the plastic ties. I ended up using AMI "Instant Roadbed" which both held the track firmly in place and deadened the sound. The Instant Roadbed is very flexible and the plastic-tied flex track can be pressed into it, usually easily, depending upon e temperature of the room. I have used a low wattage hair blower to soften the Instant Roadbed without softening the ties.

I assembled the roadbed, complete with the track and Instant Roadbed, before putting them in place on the layout. That way, I could drill through the layers of Masonite and thus save time and make sure the holes were all aligned properly for the vertical threaded rods. This helix setup has worked fine for the past ten years or so.

I use Digitraxx DCC and I ran the wiring busses but inside the edges of the helixes, following the turns, so the busses then could enter and exit the helixes at the proper places. I elected to use horizontal power districts on the whole layout, rather than vertical ones, in order to make trouble shooting a lot easier because of the layout's various levels (there are 3) and geography.

AMI went out of the roadbed business in 2007, unfortunately. The material is uncured butyl rubber and I understand that similar material can be gotten at auto supply stores that specialize in air conditioning parts (it's used to wrap a/c piping). I haven't tried since I still have some AMI material left. Somebody also found similar material at:

http://www.trains.com/trccs/forums/1056223/ShowPost.aspx

Someone else has suggested trying plumbing supply stores; the material, or similar stuff, used to wrap pipes.

Hart Corbett
 

tootnkumin

Well-Known Member
Staff member
#20
Sounds to me that he's using at least 2 layers of 1/8th thick, cut to lengths as can be achieved from a sheet, then staggering the joints, so they are never directly one above the other. 3 layers would give much more strength and prevent any chance of kinking where there is a joint. Basically you would be building a continuous masonite ply spiral, but being stronger and thinner than one made from plywood.
 



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