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A common topic that comes up in this section is something along the lines of : "How strong does a certain part need to be for a horsepower level or weight?"
One of the many things I do at Roush is test and analyze part durabilty. I often use strain gauges, tensile testers and examine broken parts.
Part breakage is a very common problem in the racing industry but it also happens in other fields as well. Because of our experience in material science we often get asked to consult on engineering problems.
The LV monorail recently had some unfortunate part failures that lead to grounding the fleet until the root cause was found and addressed. The locals are perplexed why a 60 million dollar piece of equipment isn't more durable. The answer is as complex as the machinery.
On the way back from Las Vegas I picked up a book by Henry Petroski to read on the plane.
'To Engineer is Human'
He teaches mechanical engineering at U of T Austin. He has an interesting demonstration for new students showing the problem of predicting part failure.
He hands out paper clips to all the students and asks them to bend them until they break, while keeping track of the number of bends. He records the numbers on the board and does a graph of the data.
The results show a classic bell curve with most breaking at a certain number but some lasting longer and some breaking sooner. All the paper clips came from the same box.
There are many reasons why one part breaks sooner or lasts longer but it's difficult to predict EXACTLY when a part will fail.
A part that is designed to last a long time may be very heavy and rob horsepower. A lightweight part may spin faster but need regular maintenance and or replacement.
A strong and light part is probably also very expensive.
There are many tradeoffs and decisions but there isn't one finite answer to how long a part will last, just statistics. Keep that in mind when a part is claimed to be good a certain horsepower level. Just like the paper clip experiment, some level of stress applied over certain number of cycles is what breaks parts. Horsepower is one factor to stress but as RPM increases so do the number of stress cycles.
The statistical bell curve may say that an axle is good for 400hp but in the field it may break with only 300 or it may hold up to 450.
Choosing the largest margin of durabilty is safest. Choosing the average has it's pro's and cons, but running a part at the extreme is very risky and ultimately expensive and potentially dangerous.
One of the many things I do at Roush is test and analyze part durabilty. I often use strain gauges, tensile testers and examine broken parts.
Part breakage is a very common problem in the racing industry but it also happens in other fields as well. Because of our experience in material science we often get asked to consult on engineering problems.
The LV monorail recently had some unfortunate part failures that lead to grounding the fleet until the root cause was found and addressed. The locals are perplexed why a 60 million dollar piece of equipment isn't more durable. The answer is as complex as the machinery.
On the way back from Las Vegas I picked up a book by Henry Petroski to read on the plane.
'To Engineer is Human'
He teaches mechanical engineering at U of T Austin. He has an interesting demonstration for new students showing the problem of predicting part failure.
He hands out paper clips to all the students and asks them to bend them until they break, while keeping track of the number of bends. He records the numbers on the board and does a graph of the data.
The results show a classic bell curve with most breaking at a certain number but some lasting longer and some breaking sooner. All the paper clips came from the same box.
There are many reasons why one part breaks sooner or lasts longer but it's difficult to predict EXACTLY when a part will fail.
A part that is designed to last a long time may be very heavy and rob horsepower. A lightweight part may spin faster but need regular maintenance and or replacement.
A strong and light part is probably also very expensive.
There are many tradeoffs and decisions but there isn't one finite answer to how long a part will last, just statistics. Keep that in mind when a part is claimed to be good a certain horsepower level. Just like the paper clip experiment, some level of stress applied over certain number of cycles is what breaks parts. Horsepower is one factor to stress but as RPM increases so do the number of stress cycles.
The statistical bell curve may say that an axle is good for 400hp but in the field it may break with only 300 or it may hold up to 450.
Choosing the largest margin of durabilty is safest. Choosing the average has it's pro's and cons, but running a part at the extreme is very risky and ultimately expensive and potentially dangerous.
