Checking for Tire Heating ©2009 Dr B C Paul Note – 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 l Tires flex and can get hot as a result of working under load l To avoid tire blow-outs we use Ton Miles Per Hour – TMPH l Each tire has a rating l You get the average load * average speed and compare to the TMPH rating

FPC Fussing l 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 and Note the place for TMPH entry When you see the little 3 dot Box it means there is a Subscreen for putting in or Calculating 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 in The Cat handbook This tells me my 789 has 37.00R57 Tires with an E 4 Tread

Checking the Tire Section of the Cat Handbook Most Manufactures also Have similar ratings For each of their tires (which is where Cat Got the info for the Handbook)

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 will Derate 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% of Theoretic potential is tmph on the front tires and on The rear. The numbers are in red because if we run the trucks this way we are Going 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. They Have less weight but the back axle has dual wheels. Of course a front Tire blow out is also more likely to cause loss of control (Murphy strikes Again)

Now What Do You Do? l 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 hour Shift. Typical is 50 minutes/hour or 83%. Lets Change it.

That Got Our Rear Wheels Under Control We will still blow out the front tires.

Limitations and Alternatives l 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 l Impose speed limits on haul roads Its easy to enter But can you enforce it in the field? l 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 l (Remember what ever you do on computer screen you better be able to do in the field)

My Trick My enforced tire Cool break My Results