Quite a number of years ago I was piloting a
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then quite elderly sixwheeler mounted on 14.50-20 giant tyres over Trent Bridge, Nottingham, when there was an explosion and most of the nearside of the cab disappeared. What I subsequently discovered to be responsible for the damage was hard to believe and even more difficult to explain to my employer.
The nearside front tyre had burst and the blast of air released from it had literally blown the cab apart.
I have had quite a job convincing listeners that this is a true story so it is with pleasure that I reproduce some facts issued by the Firestone Tyre and Rubber Co. Ltd. Says Firestone: -A 10.00-20, 12-ply tyre inflated to 75 psi., when it bursts releases 46,510 lb.ft. of energy, sufficient to lift a vehicle weighing 3,0001b, 15ft in the air.
"An 18.00-22.5, 16-ply lowprofile inflated to 75 psi. will release 103,789 lb.ft. which would toss an 83Ib object clean over the New York State Building. One of the 24.00-49 earthmover giants at 75 psi. produces sufficient force to lift a man weighing 134Ib a half-mile into the air, when it bursts releasing some 354,260 lb.ft, of energy.
Nurnerous safety regulations are laid down for the assembling and servicing of tyres and wheels but seldom abided by. Although garages are advised to provide protectors or cages for containing tyres and wheels while they are inflated, very few operators make use of them.
Twelve elementary safety rules laid down in Firestone's latest newsletter are:--- 1 . Before unlocking a rim or ring, make certain all the air is out of the tyre by removing the valve core. First, reduce the pressure by pushing the plunger, then remove the entire core. Keep your eyes away from the valve.
2. Before mounting a tyre and assembling the rim, carefully inspect the rim parts for damage, rust and distortion. Do no use rims, locking rings or flanges which are out of shape, rusted or broken. Never mix rim parts of different brands and never try to mend broken wheel parts. Replace them with new parts of the same size, type and make.
3. When using a jack, block the tyre and wheel on the opposite side of the vehicle before you place the jack in position and, no matter how firm the ground appears, put hardwood blocks under the jack.
4. Before inflating the tyre, make certain the rim ring is seated to the full depth of the groove, fits tightly all around, and is securely locked. With certain types of wheels it is necessary to seat the rings while the tyre is being inflated.
5. Attach a portable safety device, made especially for the purpose, to the assembly. This device can be used with all types of wheels and rims. If the assembly does not require inflation to seat the rings a safety cage can be used.
6. Stand away from the valve. stem as far as possible white inflating. Use a clip-on chuck and extension hose long enough to allow you to stand to one side. When working on any tyre in which there is pressure, avoid a position where the face or body is directly over the work.
7. When changing tyres on drop centre wheels, remove wheels from the truck and place on a wheel holder or tyre changing machine. It is easier and quicker this way than trying to change the wheel on the truck.
8. Always take care when using tyre irons. They can fly with tremendous force, if they slip. Use only standard tyre mounting tools and equipment. Employing makeshift tools, such as screwdrivers or pliers to force tyres on or off wheels or rims, is dangerous.
9. Be careful when pounding rings or rims with a steel hammer. Small bits of steel can break off and fly into your face. Use a rubber-covered hammer whenever possible.
10. ' Tyre spreader arms can be dangerous. Keep them closed when the machine is idle.
11. Always wear goggles or face shields when buffing rims or tyres.
12. Be careful when lifting. Use your legs as well as your body to prevent injury. It makes lifting easier; it Lessens the chances of dropping the assembly on your toe.
Many pieces of garage equipment used every day can be lethal and it is never a bad idea to remind users from time to time that this is so. I number among my haulage friends at least two men permanently crippled by bursting wheels, and the full number of injuries sustained in this way must be quite high. ''Better to be safe than sorryis not a bad slogan to instil into workshop staff, no matter what their task.