Rubber hose is built on a mandrel by wrapping sheet around it or dipping it in rubber cement, with layers of cotton or linen fabric between the rubber layers if it must hold pressure, then vulcanised wrapped tightly in wet cloth and slid off the mandrel. A 25 mm hose at 3-10 bar tries to push itself off its fitting with 147-491 N, so the clamp matters as much as the rubber. Rubber cement uses a flammable solvent, so make it outdoors, away from any flame.
Part of Rubber Processing
Making flexible rubber hose and tubing for fluid systems.
A Hose Is Rubber, Fabric And A Clamp Working Together
The carrier builds hose by wrapping rubber sheet around a steel rod or tube, alternating rubber layers with fabric wraps for a reinforced hose, vulcanising the assembly wrapped tightly in wet cloth to apply pressure during the cure, and pulling the mandrel out. The corpus’s Hoses and Tubing article builds the wall by dipping, and the Rubber Products article wraps strips spirally with half overlap. This article connects the three.
| Hose type | Pressure limit | Source |
|---|---|---|
| Plain dipped tube | 0.5-1 bar | Hoses and Tubing |
| Single-braid fabric hose | 3-10 bar | Hoses and Tubing |
| Suction hose | Needs a wire helix of 1-2 mm wire at 10-15 mm pitch | Hoses and Tubing |
What You Need
- A mandrel, a steel rod or tube, dusted with chalk or talc so the hose slides off.
- Rubber sheet of 1-2 mm, or rubber cement made from rubber dissolved in turpentine at a 1:4 ratio (rubber-products article) or 1:3-4 (hoses article).
- Cotton or linen cloth for reinforcement.
- Wet cloth to wrap the assembly for the cure.
- A heat source for the cure; see Curing Temperature and Time.
- Hose clamps or wired joints.
Method: A Reinforced Hose
Step 1: Dust the mandrel with chalk.
Step 2: Wrap an inner rubber layer with half-overlap and cement the layers together.
Step 3: Wrap a fabric layer.
Step 4: Wrap an outer rubber layer.
Step 5: Wrap tightly in wet cloth and vulcanise. The rubber-products article boils the assembled mandrel for 2-4 hours; the hoses article cures at 140-150 °C for 45-60 minutes with 5-8% sulfur.
Step 6: Unwrap and pull the mandrel out.
Step 7: Test with water at working pressure before use.
Worked Example
Wall by dipping: 10-20 coats of 0.3-0.5 mm each give 10 × 0.3 = 3 mm to 20 × 0.5 = 10 mm of wall.
Pull on the clamp. Pressure acts on the end area of a hose, trying to eject it. For a 25 mm inside diameter the area is π ÷ 4 × 25² = 491 mm². Pressure of 3 bar is 0.3 MPa = 0.3 N/mm², so the force is 0.3 × 491 = 147 N. At 10 bar it is 1.0 N/mm² × 491 = 491 N. That is about 15 kgf to 50 kgf (dividing by 9.81), which is the load the clamp and the barb must hold, in addition to hose-end vibration and shock.
Common Mistakes
- Clamp too weak. The hose blows off its fitting before it bursts.
- Not taping or wrapping tight for the cure. The layers blister.
- Using natural rubber for fuel or oil lines, which swells in oils.
Safety
Solvent vapour from rubber cement
Rubber cement is rubber dissolved in turpentine, and the vapour is flammable and harmful to breathe. The vapour of turpentine and similar solvents is heavier than air (recalled, not from the corpus) and collects low, so ventilate at floor level. Make and use cement outdoors or in a draughty open shed, keep every flame, spark and hot bath away, keep the container sealed and the quantity small. Do not test for vapour with a flame; if you can smell it, ventilate. The corpus’s Ventilation article is about petroleum vapour, which is a different hazard.
A pressurised hose whips
A hose that comes off a fitting under pressure whips violently and sprays its contents. Depressurise before disconnecting, secure long runs and test at working pressure with the line staked down and everyone clear.
What’s Next
- Learn next: Tire Basics — fabric and rubber in a bigger form
- Combine with: Hydraulic Systems — where reinforced hose is used