Tubes

1. Original Design

Elon originally proposed tubes that are shaped to the path and run the entire span of the 100ft spacing between the pylons and are welded at the junction.

1. My Design

I propose tubes that are manufactured straight and only 50ft long with bolted connections between the tubes. The tubes would have a square faceplate at each end for the bolted connection. Bends in the line will be accomplished during the spacing between the tubes. A rubber-like material will be placed between each tube about 1in thick so the tube can handle earth movements easily without a rigid weld. This rubber material will be wedge shaped on bends so one side could be 1in and the other side would be up to 4in thick for a very tight bend radius, and generally much less for larger bend radii.

Tube would also have locking connections at the top and bottom to connect with additional rows of tubes vertically. These connections would connect to the pylons on the bottom and to the solar panels on the top. The width of the solar panels would have to be increased for each row of tubes added.

Elon estimates tube widths at about 11ft on the outside, which is wider than standard trucks will allow, so the tube would be prefabs in two halfs so no extrawide load permits would be required for transportation and just bolted together onsite.

The tubes can be either:

1. Bolted together on the ground for the entire span between the pylons and then crane lifted up to the pylons

2. Crane lifted one by one by being bolted on to the end of an existing tube already attached to the pylons

Other things to consider in the tube, but not yet shown in my sketch below is the tube should:

1. Be able to host the magnets that will move the train forward.
2. Have a place for sensors for air pressure, etc.
3. _{~Have a place to attach on the top the solar panels}~ (these are now shown on my sketch diagram with the hooks on top)
4. Have a section on the side to host electronic like inverter for the solar panels, battery, wiring etc.
5. Have a cable conduit to be able to transport commands and telemetry for that tube section transport command can control magnets on the tube section, give feedback on how much energy is being gathered by the solar panel.

For most of these, I plan on adding a compartment along the bottom and adding about 4" or so to the height of the tube to accommodate this extra equipment. Also, I need to show the fact that the tube is designed to be split in half and shipped in two parts to avoid oversized width permits.

1. Sketch


The 3D model for this is available in SketchUp 8 format in the repository [here](https://github.com/OpenHyperloop/OpenHyperloop/tree/master/Tubes/Sketches)

1. Advantages

• Single type of tube would allow faster manufacturing

• Easier to assembly line the production of the tubes

• Each tube would be interchangeable, so if one needed to be replaced/repaired, it would be easy to stockpile a few extra tubes without having to remanufacture one at a specific bend radius.

• Easier to transport since standard trucks can already handle 50ft long loads, allowing easier offsite prefab.

• Faster installation since securing a few bolts around the tube would be a lot faster than having to weld it in place.

1. Disadvantages

• Possibly a bumpier ride on the corners since the turn becomes segmented instead of smooth, however, it should be mitigated somewhat because the riders are already on a cushion of air and the bends are very small and very close together.

1. Other thoughts

The original design had no ‘Y’ concept in the tubes allowing turn offs or switching to other tracks. I propose a 500ft straight section with a tube bending off to an opening that is adjacent to the standard opening. This would allow rerouting passengers to other lines if a section of tube needs replacement or repair.

Also, I think the tubes should have some type of basic ladder structure going over the tubes and a scaffolding structure under the tubes to facilitate maintenance and possible evacuation.

Looking at the tube itself, wikipedia states that OpenMDAO estimate a tube width of 4m would be required (probably internal diameter). Wall thickness requirements are hard to guess, as the dynamic load of the high-speed pod moving through the tube combined with the high pressure waves around the pod impacting the walls would pose a risk of fatigue failure. Additionally, on such a large structure without any internal supports one would have to worry about buckling. Whatever thickness is settled on, a large safety factor is a must.

The cross-section of the tube would be (pi*(d+2*t)/2-pi*d/2), where d is the inner diameter and t is wall thickness. Steel has a density of ~8000 kg/m^3 so we can begin to estimate mass.

t=1cm, mass = 252 kg/m
t=3cm, mass = 377 kg/m – 50ft section weighing 5749 kg

It might be possible to guess at material+transport costs based on this calculation.

I am sceptical about splitting the tube into two sections down the middle. It seems structurally difficult to build and difficult to seal.

1. Comments:
   - We should pin down minimum expected bend radius → maximum wedge differential.
   Perhaps on Reference Values page? (jimswen)
   – My calculations are in the min bend radius of about 0.5 miles (OpenHyperloop). It actually depends on the length of the pods to ensure that the bend isn’t so tight that the pod can’t make it through.
   - Very skeptical about a Y-junction in the tube: the levitation airgap is only 1 millimeter or less.
   – So, either:
   – the car always sits in a trough of circular cross-section, and can’t glide across the flat or complex part of a Y, or,
   – the air-bearing legs would need articulation and the feet probably need to adjust to changing curvature, from circular-trough to flat-surface.
   – Also, it sounds so (expletive deleted) risky, running towards the cusp from the lower stem of the Y.
   How can you make absolutely foolproof to go left or right, and never in the middle?
   – So I think any line branching requires stopping at a mid-line station, or at least airlocks and greatly slowing.
   – Thanks for the feedback! I’m not 100% sure about the ‘Y’ design either. It would primarily be for straight sections so the pod wouldn’t be banking and in order to go through the bend section, not the straight section, I was envisioning some type of mechanical mechanism in the ‘Y’ that would guide the pod to the correct area. (OpenHyperloop)
   – I do admit, it’s quite risky, so we may have to stick with transfers at stations, or make ‘mini’ stations where we want to do a ‘Y’ (no unloading or loading of passengers). This would require all traffic to slow down into a ‘station’ that would decide if our pod is destined to route A or route B then move us into the correct output tube. (OpenHyperloop)
   – Splitting the tubes in half for shipping may have structural repercussions. A tube of this length would be very difficult to keep at a low pressure, and additional seams running its length may create too much air leakage. Additionally, the forces imposed on a low pressure tube are huge. Creating a joint that won’t deform under the pressure over time, especially with the changing pressure caused by a fast moving vehicle, may not be possible. I study ECSE, so someone else would need to do the calculation.