Tent Rings

Diffusion

Stress points

Traditionally, several approaches have been used to combat this - most of which aim at either increasing the area over which the force is distributed, or increasing the strength of the fabric where the force is greatest.

The main approaches are:

• Use a metal ring - instead of allowing the fabric to continue up to the tent pole.
• Use an internal "pressure diffuser" to increase the area over which the pressure is distributed.

• Reinforce the fabric at the point near the pole.
• Use ridge poles - or ridge cables.

Tent rings

Eden project - tent ring

Wildwalk - tent ring

A tent ring is traditionally known as a "Bale Ringe".

Conventionally, these are used on large tents where the erection process involves erecting the tent pole first, and then lifting the fabric over it using a rope passing through a pulley system near the top of the pole. For this to work, the fabric has to have a hole in it larger than the widest diameter of the tent pole - thus the metal ring.

The metal ring also serves the purpose of diffusing the pressure applied to the fabric over a wide area.

Diffusion rings have been used on a large scale - for example in the Haj Terminal:

Haj Terminal

I note that an ordinary bicycle wheel would often be quite a good match for this application:

Bicycle wheel

BMX bikes often seem to have rather small wheels with lots of strong spokes - perhaps they would be best of all.

Reinforcement

Reinforcing fabric

Internal diffusers

Hassaniya tent diffuser

This photograph shows the inside of an African desert tent.

It is one of a numer of pole pairs that typically run down the middle of the tent.

Montreal pole tops

To give an exterior view, the above photograph shows the tops of some poles in the Montreal olympic stadium showing through the membrane roof.

Ridge pole

Ridge pole

Instead of reinforcing the fabric, additional support can be provided in the form of struts or cables.

The photograph above shows the use of a rigde pole to provide additional support to the fabric.

In larger tents, this pole is also used when lifting the fabric into place.

A ridge pole elevated this far tends to destroy the anticlastic shape of the surface of the tent - making its covers more prone to flapping in the wind and the associated frictional damage.

Ridge cable

As an alternative to using straight struts for additional support, reinforcing cables may be used - as illustrated above.

If taken further, the idea of using additional poles or cables to support the fabric can ultimately lead in the direction of frame tents - which use many poles to support the membrane. These tend not to have so many "sharp" pressure points as conventional ridge tents.

Frame tent

Frame tents dispense with poles in the middle of the tent.

However the weight and cost of the poles can get substantial - and the ideal of using a doubly-curved anticlastic fabric surface often seems to get lost in the process.

Misc photos

Ring

Ring

Ring

Diffuser

Diffuser