Building a Helix with PVC Pipe

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beiland

Active Member
#21
Does sound like that doesn't it. 2 o3 layers with the joints staggered does sound interesting.
I'm trying to contact that poster to see what he has to say in addition to his posting.
 
#22
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
I wouldn't recommend MDF. It generally not used as a structural material. It is a filler material. You should be using plywood or hardboard.

I think the PVC pipe idea is interesting because plastic is more dimensionally stable than wood. I would not waste wire trying to put the wire bus in the pipe. You want the least resistance in your layout wiring.

Modeling the roaring 20's
President of the Lancaster Central Railroad
President of the Western Maryland Railway
 

tootnkumin

Well-Known Member
Staff member
#23
Does sound like that doesn't it. 2 o3 layers with the joints staggered does sound interesting.
I'm trying to contact that poster to see what he has to say in addition to his posting.
Been having a think about the practical problems of building a continuous spiral of road bed using plies of material (whatever they may be of) since Frederick's post. It would be a difficult challenge. It would have to be done within the helix's frame to keep it in shape and each full layer of plies would probably need some barrier (greaseproof paper or similar) between, to prevent glue seeping and sticking the lot together, because they'll all be resting on the layer beneath as you build upwards. 3 plies, I think would be the minimum needed to hold it all together and each 2nd and 3rd ply would have to finish a foot (preferably) before the end of it's predecessor to create a good strength laminate at those joints. Clamping as you went would be essential. Sliding clamps would be best, so as to adapt to the increasing thickness. Having a"tail" extending out of the helix would provide good leads, top and bottom (and in between if required).
 

NP2626

Active Member
#24
Toot, when I was reading this idea a few months ago, I dismissed the idea. I have no doubt it could be made to work; but, feel that it is far more complicated than a Helix made from the common materials they have been made from. Since the idea is to keep the helix layers as close together as possible, thus reducing the grade,using 1/2, 1/4th; or, what ever diameter PVC tubing is thicker that 1/8th inch hard board/Masonite. Also, i don't see an easy way of attaching track to PVC tubing.
 

tootnkumin

Well-Known Member
Staff member
#25
Mark, I think the plywood base will be around a lot longer as the most practical method. Just splint the joints between pieces. There are higher strength plywoods available to reduce the thickness if that's a problem. Boatbuilding plywood is much stronger for any thickness and has the added advantage of moisture resistance.
 

beiland

Active Member
#26
My thoughts at the moment,...
I would use the double layer of 1/8 Masonite with large overlap circular segments,...just much stronger and minimal extra height to helix.

I believe you could fabricate these Masonite semi circles as one entire circle (4 segments?) each time, and then place then in the helix structure. RR track would also be set in place and tack glued down as each full level went up. Then final gluing of the track after assurances of smooth track transitions thru out the whole helix.

The helix structure would look something like this pic I posted...
DSCF1154.jpg

...and the Masonite roadbed would be supported by the metal corner brackets like these...
DSCF1152.jpg

Some sort of guard sheet could be attached to the outer sides those upright post after all of the levels are finished, and this would keep trains from falling to the outside of the helix. The helix track is then readily accessible to a person on the inside of the helix structure as the tracks and roadbed are 'cantilevered' out from those upright supports by the steel brackets.
 
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beiland

Active Member
#27
Wiring the Helix for DCC

I saw this posting and wanted to make note of it here so I remember

Also if dcc is your plan run a bus around the base level then run vertically to connect to your tracks you will save lots of wire, you may desire to have two or more vertical runs.
 

beiland

Active Member
#28
Radius(s) of Double Helix ?

Neal M

Mine is a two track helix. Inside radius 29.75 outside radius 32.00. It has a 2% grade with a height of 12" This was the biggest I could have due to space restrictions. I'm sure a wider helix with a lesser degree of grade would be better. I've run 2 diesel engines, both 4 and 6 axle engines and anywhere from 20-28 cars with no issue. However, with my 89' auto racks, I usually have 2 6 axle engines with 12 auto racks. I don't see any type of drag or issue running them up the helix.
I'm assuming those radius quotes are dimensions to the center of the tracks?

So on your double track helix you have 2 1/4" between the tracks.
1) Can you run your long auto racks up the outer track while running another train passing it on the inner track?
2) What sort of minimum clearance do you find necessary for those auto racks to clear any fixed obstacles (structures) outboard of the outboard radius.

I am planning a double track helix in as big of a diameter helix as possible, but I am limited to probably a 31" outer radius. I also want to run those long auto racks and long passenger cars (and sometimes possible a passing situation on the helix). So my concerns are, the clearances needed for the ends of those cars around the outer helix structure components,....and the minimum distance I might allow between the inner and outer helix tacks to allow for those 'inadvertent' passing situations that might occur when running multiple trains.
 
#29
I saw this posting and wanted to make note of it here so I remember
Also if dcc is your plan run a bus around the base level then run vertically to connect to your tracks you will save lots of wire, you may desire to have to or more vertical runs.
Missed this way back when it was posted. However I would not run a bus wire all around the base. Just 1/2 way around the base at most.
Here is a photo of this idea in practice. Note the wire going vertically up right next to the business car at the rear of the train. If one squints the matching wire can be seen on the other side of the train too.
 
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beiland

Active Member
#30
What are your two radius(s) ?

And what distance between the center of the outer track and those all threads??

And just for info, what height railhead to railhead?
 

NP2626

Active Member
#31
With the "Threaded Rod Idea", why not use the threaded rods as wires going up the helix? Simply trap the wire under the washers and there is your connections. However, I understand threaded rod is not the method your using, Beiland!
 
#32
What are your two radius(s) ?

And what distance between the center of the outer track and those all threads??

And just for info, what height railhead to railhead?
That would be 34" and 36". Without going and measuring it, it is about an inch and a half to the screws. At this radius, there isn't much of anything that leans out over the outside edge of the tracks that much. And I don't know rail head to rail head, but from rail head to the plywood over it is 3.5" - tall enough for double stacks and fingers.
 
#33
With the "Threaded Rod Idea", why not use the threaded rods as wires going up the helix?
That would probably work, but compared to copper, steel is a horrible conductor. I wonder if brass threaded rods are strong enough? But then that would probably be way more expensive than the "free" scrap wire that was used here.
 

beiland

Active Member
#34
I wish I could make use of 2 radius like that dimension, but I had a post out back of my shed that has my main electricity coming in. I don't think they want me to screw around with this....ha...ha

So the maximum outer diameter I can use is 65",....32 radius. And that's pushing it. So i thought 31" max. I saw one helix that had the threaded rods come up thru the center of the roadbed for the double tracks (instead of threaded rods on both sides of the helix roadbed,...something to consider.
 
#35
I saw one helix that had the threaded rods come up thru the center of the roadbed for the double tracks (instead of threaded rods on both sides of the helix roadbed,...something to consider.
I can think of another consideration for that. To put the rod through the center, the distance between the two tracks would have to be greater than (in HO) 2". That means the inside track would have to be that much tighter. In this case, probably 33" rather than 34". If one is already pushing minimum radius on that inside track it could be an issue.
 



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