Trapezium Calculator

 

This Trapezium calculator is multi-purpose

This is also a reverse Trapezium calculator

It will calculate any size of dome and display the lengths for each strut, total amount of material required, the weight of your geodesic dome and even the amount of material to cover your geodesic dome. Enter any value in any yellow box and it will calculate all other corresponding values. For example you can specify a 2-foot length for strut “B” and all other struts and related values will be calculated.
Click here to see all calculators on Domerama

NOTE:

If you enter a measure in feet, your results are in feet or, in the case of floor area, square feet. Same goes for meters.

When entering in feet, decimals are fractions of a foot or square foot (for example: 2.75 = 2’9″).

Spherical radius
Spherical diameter
Floor area
Perimeter
feet of pipe / lumber
NOTE: if you are bolting conduit, regardless of dome size, add an extra 32 feet or 10 meters to total above (based on 3″ or 8cm for each strut)
ANGLE
16 X “A” 10.38°
16 X “B” 7.93°
16 X “C” 4.28°
80 X “D” 11.25°
Total number of struts: 128
For conduit, you can round bend angles to the nearest degree. For timber domes, angles should be to the nearest tenth of a degree.
trapezium-4-row-16-sector-E

See assembly diagrams at bottom of this page

Struts are vertex to vertex

That means end to end. But to connect them together with bolts, you need to make them longer to drill holes in them.

 

For more information on cutting, bending and flattening struts, click here

 

Connecting struts

Many types of connectors are available for steel and timber Trapezium. For more information, click here.

If you use hubs

1 X 16-way connectors 48 X 4-way connectors 16 X 3-way connectors
OR
If you bolt struts together
65 bolts
65 nuts
130 washers
For more information on cutting, bending and flattening struts, click here

 

Floor Surface and Capacity

Your calculated floor surface area is
SQUARE FEET/METERS
NOTE: RESULTS IN THIS SECTION ARE BASED ON FEET.

Trapezium floor

Capacity

Concrete Cubic feet Cubic yards
4″ slab
6″ slab
8″ slab
Plywood 1/2″ 4′ X 8′ sheets
Estimated standing capacity
Estimated dining capacity
Estimated conference capacity
For more info on capacity, click here

 

How much will your Trapezium weigh?

Your calculated Trapezium diameter is

NOTE: RESULTS IN THIS SECTION ARE BASED ON FEET.

1/2″ 3/4″ 1″ 1 1/4″ 1 1/2″ 2″
EMT
Wall thickness 0.042″ 0.049″ 0.057″ 0.065″ 0.065″ 0.065″
Lbs.
kgs.
STEEL SCHEDULE 40
Wall thickness 0.109″ 0.113″ 0.133″ 0.140″ 0.140″ 0.154″
Lbs.
kgs.
ALUMINUM SCHEDULE 40
Wall thickness 0.109″ 0.113″ 0.133″ 0.140″ 0.140″ 0.154″
Lbs.
kgs.
LUMBER
2″ X 4″
2″ X 6″
2″ X 8″
Lbs.
Kgs.

 

How much will your Trapezium cost?

The tables show sample costs. Material prices vary with suppliers and area.

Your calculated Trapezium requires
feet (or meters) of pipe / lumber
NOTE: THIS SECTION ONLY ESTIMATES COST IN FEET.
Galvanized pipe – Steel Schedule 40
Your estimated pipe dollar cost is:
1/2″ @ $13 /10′ length
3/4 @ $17/10′ length
1″ @ $25 /10′ length
1 1/4″ @ $34 /10′ length
1 1/2″ @ $42 /10′ length
2″ @ $55 /10′ length
Structure pipe – Aluminum Schedule 40
Your estimated pipe dollar cost is:
1/2″ @ $ /10′ length
3/4 @ $ /10′ length
1″ @ $ /10′ length
1 1/4″ @ $ /10′ length
1 1/2″ @ $ /10′ length
2″ @ $ /10′ length
Structure pipe – EMT
Your estimated pipe dollar cost is:
1/2″ @ $5.50 /10′ length
3/4 @ $ 8.80 /10′ length
1″ @ $18 /10′ length
1 1/4″ @ $19 /10′ length
1 1/2″ @ $22 /10′ length
2″ @ $3 2/10′ length
Cover: approx. s.f.
$ COST
Canvas 20 oz. ($1/s.f.)
Canvas 42 oz ($1.50/s.f.)
Poly 3 mil ($0.05/s.f.)
Poly 6 mil ($0.06/s.f.)
Marine Shrink Wrap 7 mil. ($0.08/s.f.)
Industrial fire-retardant Shrink Wrap 12 mil ($0.23/s.f.)
Aluminet 70% shade cloth ($0.35/s.f.)
Tyvek (housewrap) ($0.41/s.f.)

Plywood 1/2″ ($25/ 4′ X 8′)
Wood struts
Your estimated wood dollar cost is:
2″X4″ @ $0.35 foot (avg.)
2″X6″ @ $0.50 foot (avg.)
2″X8″ @ $0.70 foot (avg.)
Flooring:
Plywood 1/2″ ($25/ 4′ X 8′)
OSB 1/2″ ($9/ 4′ X 8′)

 

 

 

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