Well, I have reached another milestone with the completion of the helix. When I say “completion”, it’s not 100% complete as I plan to put some ‘guard sides’ up on each of the layers to afford some protection to prevent trains from taking a plunge if they derail, but I plan to do this later on. But otherwise, the main structure is finished.
Following on from the last post, the next stage was to set the height of the first (bottom) layer to the correct height as this would then set the grade for the whole helix.
My initial attempt at this didn’t go so well, as I think I miscalculated the height of each sequential riser, eight in all. The reason I say this, is when the rest of the layers were lifted up into position, something didn’t look right. Some segments of the helix looked steeper than others.
The picture above shows the helix layers lifted up and spaced with temporary blocks at the correct height. This picture was taken with the first layer risers that were incorrect. To lift each layer up, it was just a matter of carefully lifting the whole thing and placing the temporary blocks in place at each of the eight support locations around the circumference. This was repeated for each layer.
After some later discussion with my consultant (Andrew), and after some more measurements and calculations, we came to the conclusion that I had indeed stuffed up the initial height calculations.
Some new risers were then cut, and fixed in position.
The pictures above shows the new first layer risers all cut and installed. These were glued to the L girders as well as the ply roadbed. After these were fitted, the whole helix looked much better and with even grades.
I had originally planned to make notched risers to support the helix at the eight points, but could not work out a way to accurately cut these notches. After some discussion again with Andrew, I decided to still use the 2×1 as the risers on the inside and outside, but just glue blocks in place to support the roadbed layers. See the pictures below.
The blocks were cut from some of the timber I had used to make the temporary spacer blocks. They were cut to about 15mm thick so as to not encroach too much onto the track and to allow enough room for the longest piece of rollingstock to pass through with clearance. The blocks are only glued to the risers and not the plywood. This should allow for any slight expansion and contraction in the timber.
Just to finish off, below are a couple of shots of the finished structure. I have also fitted the transition piece of ply roadbed from the top layer to where the spline will be attached at the 70 inch level. I am surprised at how rigid the whole structure is now.
Where you can see the red clamp, I have placed a temporary riser to support the transition section where the spline will attach.
At some stage, I want to temporarily connect a throttle of some sort to test run a loco up the helix.
Cheers for now.
Well, I completed the first stage of the helix today. All five layers are complete with track. The topmost layer of track has been left a bit short from the end of the roadbed as I will complete this part when I come to merge the helix with the upper deck roadbed at a later date.
The picture above shows the helix at about the halfway stage which was on 13 May.
The picture above shows the helix layers complete with track ready to have the final temporary spacer blocks fitted and then the notched risers. I hope to be able to have this all done by this time next week.
I was amazed at just how quickly it all went all together. I got into a rhythm of gluing the ply sections together, clamping then leaving for three hours. Whilst these were drying, I could lay track on a previously completed roadbed section up to the clamped section. I could lay three sections of 914mm track during this time and by the time I was finished, the glue had set on the next roadbed section, and the process started all over again. Each new roadbed layer was supported on temporary blocks to allow access for clamps. These can be seen in the photos.
Cheers for now.
Since the last post, there’s been more movement on the helix build.
My package of PECO Code 75 flex-track from the UK arrived on Monday (30th). Before anyone starts on about why I didn’t buy it locally, I’ll tell you why. I got fifty 914mm (3ft) lengths delivered from the UK for $173.75. A quote I got from Brunel Hobbies in Melbourne was $176.60 (posted to Port Macquarie) for 25 lengths – double the price!! Why should I buy locally? If importers in this country feel the need to put such huge mark-ups on items sourced from overseas, is it any wonder they are complaining about internet sales taking away their business. I won’t say any more on the subject.
Anyway, back to the topic at hand.
Before track laying could commence, I had to build part of the first section of spline that would exit from the helix and continue on towards the storage yards. So, I did the usual thing of marking out where it would go using measurements from the 3rd Planit drawing. I also made a short transition piece of helix roadbed for the spline to attach to. I decided to only make a short section of spline so I could later remove it to rebate the top where it meets the helix.
Whilst the spline was being made, I mulled over how to start laying the flex-track. It’s funny to think that I have never really laid any flex-track in all my years of modelling. Anyway, first step was to mark a centreline on the helix roadbed. I then spent some time thinking of the best way to lay the track. As I would require joins on curves, I didn’t really want to just ‘butt’ join the sections as this generally does not allow for a smooth curve through the join. So I decided to stagger the joins. With PECO track, both rails are able to slide through the moulded chairs, so I pulled one rail back about nine sleepers, and cut away a couple of sleepers where the join would be. As I didn’t have any PECO rail joiners, I did the next best thing – a short piece of 30 thou brass wire soldered to the outside of each rail. Two lengths of track were joined together whilst straight.
Some more time was spent deciding on the best adhesive to use to fix the track down. I wanted to find something that would glue the plastic sleepers OK, be a strong bond, be fast setting but allow time to finalise placement. I didn’t want to be waiting around for hours whilst glue dried. After heading to Bunnings and looking in their adhesive section, I finally decided on a Selleys product called Aquadhere Quickset. It sets in about 5 minutes but fully cures in around 30 mins, is water-based and dries clear.
I also had to think about how I was going to hold the track in position in the curve whilst the glue dried. I decided to use small panel pins. This PECO track does not have any holes in the sleepers, so I drilled every tenth sleeper to make a neat fit for the panel pins.
Next, the track was placed on the helix roadbed and formed roughly into the correct curve. I managed to find a Tracksetta 36 inch radius template which will do the job nicely.
So basically, it was just a matter of placing the Tracksetta between the rails, ensuring the track was on the centreline and using the same small drill as before, drill a hole into the roadbed. The small panel pins were then pushed through the sleepers into the roadbed.
I also found out that my plan of using two lengths of track pre-soldered together was not the best move, as there was a bit too much pulling of the rail through the sleepers to adjust things on the curve as I went. For the next and subsequent layers, I’ll lay just the three foot lengths in turn. It’s much easier to pull the rail through the chairs in three feet rather than six feet.
The section of spline was removed from the benchwork and set up in a jig to allow for the rebate to be made to allow for splicing to the helix roadbed ply.
The picture below shows the spline now back in situ and glued to the helix roadbed. The spline was also set at the correct grade which at around 1.8%, is slightly steeper than the visible section of the layout but should still be OK. This is the same grade as the helix.
I decided to only fix in place a short section of track on the spline merging with the helix track, so I cut a strip of the foam tape roadbed and glued it to the spline. The foam was cut to the width of the spline, but to allow it to follow the curve, some cuts were made about 75% of the width to allow it to curve and remain flat. The cuts are just visible in the image below.
Another length of track was cut to splice into the section already tacked down on the helix. Some extra support for the spline was also installed here.
Today (6th) I glued the first layer of flex track down on the helix and the spline. For the spline section, I used some black caulking compound as a trial, as I was unsure how the Aquadhere Quickset would fix the plastic sleepers to the foam. A lot of articles I have seen about laying the Central Valley tie strips to foam roadbed mentions using caulk. The Aquahere Quickset was used on the helix sections though. Using a thin metal spatula, I carefully levered up the track a small amount, still making sure it was held by the nails. The glue was then dribbled over the sleepers, and using the spatula again, smeared underneath the sleepers and over the timber. The track was then pushed back down firmly. No weights were used to keep the track down as the nails were a firm fit in the holes in the sleepers, and seemed to hold OK.
Within half an hour, the glue had set enough for me to be confident the track was held in position. I then decided to start the next layer of helix roadbed. Some small blocks were cut to hold the new layer above the first whilst being glued and clamped.
With the number of clamps I have, I can only do about three segments at a time, but it should proceed reasonably quickly. Once another roadbed layer is complete, the tracklaying process starts again for that layer and so on until I end up with five layers of helix roadbed with track attached sitting on top of one another. The next stage will be to notch out the support risers, fix these in place, and lift the levels to the correct positions but that will be described in a later post.
I did also think about soldering the track feeder wires on prior to fixing the track down, but I think I can do this later.
Cheers for now.
As mentioned in the previous helix post, I am basically following the design and construction techniques from this article in Model Railroad Hobbyist. It starts on page 61.
Rather than repeating what the article says, I will just explain what I have done, as things have gone a little differently.
Firstly, a template was made from 3mm ply for the helix segments. As my helix is only single track compared to double track in the article, I made my segments 90mm wide. I also made my segments as one-eighth of a circle to maximise what I could fit on an 8’ x 4’ sheet of 6mm ply with minimum waste. The helix requires 80 of these segments, 16 per level. As mentioned in the article, these get laminated together to form a roadbed of 12mm thickness which should be very strong and not require any splice plates. Splice plates have the disadvantage of reducing the clearance between levels.
The picture above shows eleven segments laid out on a piece of the 6mm ply. Three 8’ x 4’ sheets were purchased. As I could fit 33 segments on each sheet, these would give me plenty of room for the 80 required with some ply left over for possible entry and exit segments.
Once all the segments were cut out with a jigsaw, they were cleaned up with some sandpaper.
A lot of thought went into the next stage which was how to assemble the first helix layer. My situation differed from the article in that I could not just lay the segments out on the benchwork and go from there. There were obstacles in the way, namely the steel post and the already built benchwork.
So, it was decided to lay the segments out on the floor and glue them together.
Once the first layer was laid out, the next layer was glued to the top, with the segments overlapping by 50%. Using clamps to hold the segments whilst the glue dried was not an option, as I didn’t really want to disturb the segments in lifting them to install clamps. Small screws were used instead. These would be removed once the glue dried. During the process, measurements across the diameter were checked to see that I was in fact making a circle!
As mentioned in the article, the last overlapping segment was omitted at this stage. This was done, in my case at least, to enable this first level to be manipulated into the layout around the steel post etc.
During this time of cutting out helix segments, I also commenced work on the next section of benchwork to support the helix and the next section of spline heading towards Ardglen.
Another two I-beams were utilised again for the main supports with another L-girder wall constructed on top.
Now came time for locating the first helix layer in place. With Andrew’s assistance, we managed to get it in and around the steel post, but could not manipulate it around the wall ‘studs’ on the main peninsula. Three of these had to be removed to allow the helix to be moved into place. These were replaced later.
The final position of the helix was checked against the drawings and numerous measurements taken to get in in the right spot. It was then temporarily clamped in position.
The next stage was to construct ‘footings’ for the vertical risers which would support the helix structure. Referring to the article, this will be made from 2×1 DAR with notches cut about 12mm into the edge, spaced at the required separation distance.
Simple L-girders were made from scrap 3×1 and 2×1 in eight locations around the circumference, spaced evenly.
The above shots show the helix in position and the riser supports. There will be a 2×1 notched riser each side of the helix and they will be screwed to the 2×1 on which the helix is resting at the moment. Note that this first layer will be about seven inches higher that it is now. The bottom layer is around 49 inches elevation. Where it sits now gives me a solid base to construct the remaining four layers and to lay the track as I go. I am currently waiting on a shipment of PECO code 75 flex track from the UK before I can proceed any further. Flex track seemed to me to be the easiest method of laying track in the helix rather than using my handbuilt track method. The plan is to lay track on the first level, then construct the next level from the segments, lay the track on that level and so on. More on this later.
Cheers for now.
It’s been a while between posts. The main reason for this is since the last bit of spline was done, I soon realised that I needed to think about the construction of the helix before I went any further with benchwork or spline construction. I didn’t want to have spline in place around the next peninsula and then realise that things would be in the way when I came to build the helix.
So, things had come to a halt.
For a while now, I have been gathering information on helix construction. There are certainly many ways of going about it, but which method to choose?
I eventually settled on an all timber design, based on an article in the online magazine Model Railroad Hobbyist. In the July 2011 issue, Art Houston presents a 13 page article on how he built his 10 turn helix. What a monster!! The article starts on page 61.
But first, a bit of background on my helix requirements.
The basis of the the whole layout’s design, was to have a rising grade against UP (loaded) trains so as to enable the working of bank engines and to take advantage of features of modern DCC sound decoders that can simulate ‘load’ on a locomotive ie, to have the loco sound as if it’s working hard but just crawling along.
The ruling grade on the layout is 1 in 84 from the bridge at Chilcotts Creek right through to a point midway through Ardglen tunnel where it levels out at an elevation of 70 inches. The line from the tunnel right through Pangela to the helix remains at 70 inches. In the real world, it is a falling grade of 1 in 40. I had to keep this section level to obtain deck clearance at the crossover point just near the helix. I have ended up with 12 inches between roadbeds which should give enough clearance for things like lighting etc.
The details of the helix as shown in 3rd PlanIt can be seen in the right hand side panel of the screenshot above. The helix has a radius of 36 inches, which is less than the minimum specified for the layout, but since it will be hidden trackage, I wasn’t too concerned. This radius also was a factor in determining the size of the helix structure as it had to fit in behind any future backscenes.
3rd PlanIt makes it easy to design a helix. Once the radius is set, and the top and bottom elevations, it automatically calculates the grade, clearance between levels and how many levels there will be. Any of these values can be changed to suit and the others changes respectively.
This helix has 5 levels with a clearance between levels of 4 & 1/8 inches. My original design had the bottom level of the helix at 42 inches which gave a level run back to the storage yards. But this design had seven levels, so Andrew came up with the idea of setting a grade from the storage yards up to and continuing through the helix, which could reduce the number of levels and hence the length of run and hence the amount of track required. The first design required 129 feet of track in the helix alone. I managed to reduce it back to the 5 levels and ended up with a new track length of 92 feet – a saving of 38 feet of track.
Well, that’s a bit of background to the need for the helix and to how it was designed on paper. The next instalment will detail on how it will be constructed.
Cheers for now.