Checking for Tire Heating

©2009 Dr B C PaulNote – These slides contain material from slides dating back to 2000 and also contains screen shots from the program FPC developed by

Caterpillar Equipment Company

Haul Trucks are Very Large

Tires flex and can get hot as a result of working under load

To avoid tire blow-outs we use• Ton Miles Per Hour – TMPH

Each tire has a rating You get the average load *

average speed and compare to the TMPH rating

FPC Fussing

If you have been doing the things shown in class FPC has been protesting about no TMPH rating and no cost data• (Because up till now we have not

learned about them and have been ignoring the issue)

Go Back to the Fleet Input Screen

Go to the Fleet Input Tab andNote the place for TMPH entry

When you see the little 3 dotBox it means there is aSubscreen for putting in orCalculating more

I’ll click the box

Up Comes the TMPH Screen

Ton Miles Per Hour = (Average load on a tire)*Average Speed

The Program Automatically Gives You Loaded And Empty

weight Distribution

Well How Do I Get That TMPH Limit Number

The tire specs table inThe Cat handbook

This tells me my789 has 37.00R57 Tires with an E 4 Tread

Checking the Tire Section of the Cat Handbook

Most Manufactures alsoHave similar ratingsFor each of their tires(which is where CatGot the info for theHandbook)

Reading the Table

Average Aggressiveness Tread

535 TMPH per tire

Rating is done at 100 F standard – we are in a hot desert so we willDerate by 25% (manufactures have tables for higher non-standard temp)535*0.75 = 401

Input the Data and click Ok

Go to the Production and Cost Tab and the Tire Temp

subtab

Zooming In

The typical cycle time with delays and operators achieving 95% ofTheoretic potential is 602.66 tmph on the front tires and 483.27 onThe rear.

The numbers are in red because if we run the trucks this way we areGoing to have blow outs

If You Thought That was bad look what happens with no

delays

Interesting note – notice it is the front tires that overheat first. TheyHave less weight but the back axle has dual wheels. Of course a frontTire blow out is also more likely to cause loss of control (Murphy strikesAgain)

Now What Do You Do?

Your going to have to slow the trucks down• There are several ways of doing this

Jump Back to the Project Screen

People usually don’t work all 8 hours of an 8 hourShift. Typical is 50 minutes/hour or 83%. LetsChange it.

That Got Our Rear Wheels Under Control

We will still blow out the front tires.

Limitations and Alternatives

We could always impose a lower shift efficiency• How well do you distribute the time not

working• Shift efficiency often counts time in to the

job site and out at the end of the day – that can still leave a block of time for heat to build in the tires.

• You can force TMPH into bounds with a shift efficiency – but in practice you have to remember to keep your time off distributed (or you will only get rid of blowouts on your computer screen)

My Trick

Impose speed limits on haul roads• Its easy to enter• But can you enforce it in the field?

Impose a break at the dump point• Raise your dump time to allow for the truck

to be pulled aside to cool the tires after each dump

(Remember what ever you do on computer screen you better be able to do in the field)

My Trick

My enforced tireCool break

My Results