Tyres Flashcards
Creep - wheels
Unwanted movement of the tyre
Rotate too much - tear the inflation valve out
Monitored by the use of creep marks - does not prevent creep
Tyres up to 24 inch outside diameter - 1 inch of creep
24 inch and above - 1 and a half inch of creep
3 types of wheel
Well based
Loose and detachable flange - facilitates tyre replacement
Divided or split
Loose or detachable flange wheel
Made with 1 flange as part of the wheel and the other loose
Facilitates tyre replacement
Prevention of creep - tyres
Maintaining the correct pressure in the tyre
Knurled flange - inner face is milled with a pattern - creates more friction - enables the bead of the tyre to lock onto the wheel flange
Tapered bead set - gives a greater area
Common wheel materials
Aluminium alloy - anodised
Magnesium alloy - chromate treatment - not very common due to corrosion
Wheels for tubeless tyres
Have an “O” ring seal between the wheel parts to prevent leakage
Unlike tubed wheels the valve is built into the wheel itself and is thus not effected by creep
Fusible plugs and when is it most likely going to be used
Fusible insert melts at a pre-set temp to allow for a controlled deflation of the tyre before a blow out
Will probably melt following a max weight RTO
Fitted on the wheel rim
Different types of tyre
Tubed
Tubeless
Cross ply and radial - down to the construction
Type of tyres fitted to a/c and they are inflated by
Pneumatic tyres inflated with nitrogen
Nitrogen is intert
The tyres flexible casing is made of
Rubber coated rayon, cotton or nylon ply cords
Wrapped around beads at the ends of the tyres
The bead is made from
Steel wires
Which direction should you aprch the tyre from
Anywhere but abeam - sidewall is the weakest part of the tyre
Purpose of the “vulcanised” layer
For tubeless tyres - coating on the inside layer of the tyre
Makes the tyre permeable - provides a gastight seal
Ply rating
An indication of the tyre strength
Tread
Made from rubber - transport a/c generally have ribbed tyres
Tubeless tyre and adv over tubed
No inner tube contain the gas
Gas pressure is maintenance over a longer period
Penetration cover - no rapid loss of pressure
More resistant to blows and rough handling
No valve damage due to creep
7.5% weight saving
Bias and cross ply
Plies are laid in pairs with cords placed at 90* deg to each other
Radial
Plies are laid from bead to bead
Retread
New tread heat bonded onto old caucus
Remould
Brush off the excess rubber to the caucus then remould the tyre
Cost efficient
How many times can you retread/remould the tyre
As many times
If caucus is damaged - tyre needs to be replaced
Schrader valve
Operates as a non return valve for inflating the tube
Valve is not a perfect seal and has to be fitted with a metal cap
Metal with a rubber insert
Weight of the a/c will cause a pressure increase of the tyres by
4%
This will increase by a further 10% in service
Types of tyre tread
Ribbed - most common
Blocked - for rough surfaces
Chinned tyre
Indented on the shoulder
Fitted to the nosewheels of a/c with fuselage mounted engines to prevent water ingestion from wet r/y
Anti shimmy tyre
A maarstrand type
Speed ratings for tyres are measured in
Mph
The letters DDR and reinforced tread indicate
The tyre has a layer of fabric woven into the tread which may become visible during normal use
These are not casing chords
Red spot/ triangle on a tyre
Indicates the lightest area of the tyre - put against heaviest area for balancing
Grey/green spots on the tyres
Gas bui;cs up between the layers during construction - awl holes are drilled to let out gas and are signified by this colour
Ways to reduce tyre wear
Taxi speeds kept to a max of 25mph
Over inflation will cause excessive wear on the crown
Under inflation will cause excessive shoulder wear
