Young Hoosiers showing chords - Looking for input

[Goody]

Goody,

"I couldn't imagine going through 6 or 7 sets of tires for testing, our team would have been broke a long time ago at that rate!" I know this is provocative but this is the truth: find the money! It is there! As far as I remember the US is still part of the G7 , no?

..."nor do we have a means to log vehicle mileage easily"Oh come on: track length multiplied by number of laps? Is that difficult?

See you in Lincoln? With you mileage record notebook?

Claude

Claude,

Financially, our team has scratched together everything we have, including personal dollars into this year's car [into the thousands combined]. It is what it is and we have given it our all with what we have, and can say that without a guilty conscience. Unfortunately we cannot fund our team like others can, however we are very proud of what we have earned and put together, even though it seems to be viewed as sub-par.


Yes, we will be at Lincoln. I could provide a mileage book from this point on. It never crossed our mind to record mileage on the car, I am still unsure how that would improve the team/car with a car that has such a short life-span.

[Rex]

18 to 20 hours is a good long run for those tyres!
They are worn out. The dimples just show you how your going, not what you have got left in some cases.
Pete

This seems like a nice response - provides useful information that directly addresses your concern. Also the suggestion about the harder compound isn't bad either but the lower forces on the hard compound mean any borderline parts won't break until you slap on the sticky tires. Trust me, I've experienced this firsthand.

Claude, can you please explain the value of the mileage logbook you mention? In particular, why miles is a better measure than hours (assuming hours is done right), and also how the mileage logbook helps the car go faster? It sounds like interesting information to have and study, but either I'm missing something major (certainly possible), or logging mileage should be pretty low on the priority list for a team that can only afford one set of test tires, in a series where the entire event can be run on a single set of tires.

On a related note, I have a set of used R25 tires in my barn that you (i.e. UNT) are welcome to have for free if you come and get them. I think they're the 7" width (but I'm not 100% sure), and I estimate they have 50% life left (give or take - I didn't keep a mileage logbook either) and they're one year old. We just took them off the wheels to replace with new tires. Located about halfway between Dallas and Houston, roughly 3hrs from you guys. Might let you get in a bit more testing before you mount up your competition tires. PM me ASAP if interested so we can coordinate logistics.

Also, for what it's worth, the guys at Hoosier who handle their FSAE program have been there a very long time, are very knowledgeable, and are very helpful. Calling them with questions has always been a pleasant experience for me. I realize this is an exception in the modern world so your assumption makes perfect sense, but the Hoosier guys in particular deserve credit for being cool.

[Claude Rouelle]

Rex,

Any good engineer keep records of his actions and his team actions. Remember what the first goal of FSAE is; learn by doing and if possible learn well and right and quick. The #1 goal is not your vehicle speed; a crappy car could be compensate by a talented driver but that is waht design judges will evaluate you and your car on

It is useful to log
- the time the car leaves the pits
- each lap number and each lap time
- the time at which the car comes back to the pits
- the ambient conditions (air and track temperature, the atmospheric pressure, the humidity the wind direction and speed) . There ar cheap device (300 $) doing that job for you automatically
- the tire pressure and temperature
- the driver subjective comments
- any result of visual inspection (tire graining for example) or observed issue (something broken, a leak etc...)
- etc...


In order to
- compare your drivers speed and consistency
- compare the mileage and the failure and establish the need of maintenance
- observe the influence of the track conditions on the lap times
- car performance and consistency vs tire wear and race simulation covered distance
- basically make notes how what happened when and understand why
-.....

Also 1 hour at 30 mph average speed in cold conditions is not the same distance nor the same tire wear as 1 hour at 40 mph on a hot summer track.

I am surprised you ask. When you did some lab exercises at your school you didn't make any notes?

I hope this helps

[RiNaZ]

LOL ... this is too good !!!

yes i seldom make notes, and when i had to write reports, it sort of felt like my mom telling me to clean up my room.

now im paying for it after 10 years in the aerospace industry

[Rex]

Claude, thanks for the response, but I don't think that really answers my question. I've asked you to please explain why logging mileage is of such paramount importance that logging hours is, in your opinion, insufficient. You've responded with a list of other non-mileage items that merit logging - a list that anyone would agree is valid. In fact, it's these items I had in mind as being higher on the priority list than logging mileage. Did something in my response imply that I don't think ANYTHING is worth logging? I'm certainly not going to argue that your list doesn't make sense, because it's a great list - but I wonder how "Any good engineer keeps records...it is useful to log lap times and tire pressures" explains why a mileage log is more valuable than an hours log.

On a more relevant note, true enough that 1 hour at 30mph is different than 1 hour at 40mph because more distance is covered. I agree! Conversely, I could point out that 2 hours at 50mph is different than 4 hours at 25mph despite similar distances, assuming both runs are on demanding courses (an assumption which is inherent in your point also I think?). So I still wonder, why is mileage better than hours, assuming both figures are measured correctly?

To answer your question, when I did some lab exercises in college courses I made plenty of notes, most of which were along the lines of "I wish I didn't have to do this lab work so I could spend more time on the race car." When we tested our cars, we prepared blank data-taking pages for tire pressures and temps, lap times, ambient conditions, etc. (more or less all of the things from your list above). By the end of each test day those blank data-taking pages generally ended up with hastily-written notes along the lines of "I am sick and tired of this car breaking down every time we run it before we can gather any meaningful test data - we need more build time to improve the car's reliability - perhaps I should start skipping labwork..." For the record, this skipping lab work plan is NOT the path to academic success OR good FSAE results. Older and wiser now, our old FSAE car runs reliably most of the time - and with the benefit of additional financial resources (due to the aforementioned older and wiser situation) we have a nice ECU and/or DAQ systems which log all kinds of good data, including about half the items from your list, plus both hours run and distance traveled.

I'm not trying to have some grand debate over the internet, nor to imply that your expertise isn't valuable. But you've told a kid who is relatively new to FSAE that he should be "ashamed" of himself for not logging the mileage on his tires when he provided an hours-run figure, and I'm just struggling to understand why.

[JulianH]

Rex,
Claude says "log mileage and log when the car leaves and returns".
So you have both the mileage and the hours, and that's what you need.
Just a side note: When you look at the dashboard of your road car, can you read the miles or the hours?

When I think back, on a incredible hot day in the summer of 2012, we "killed" a set of tires (Hoosier 10" LC0) on one test-day with and winged electric car. So about 50km or something and the tires were worn out.
In my experience, it is more difficult to clock the hours correctly compared to the mileage. With our cars we often had to abort runs after a short period (maybe 1 minute or so) but still in that minute you cover 1km, it adds up.

Coming back to the topic:
Yes, the tires are gone, you need a new set.
I think in 2012 we bought over 10 sets of tires from Hoosier. Used some for non-performance tests in 2013 but still.
We log everything important in the car (all of our "cycles" to change parts is done with mileage) and it helps. Without documentation you don't rememeber what happened and even worse, why it happened.
Even with a car that runs only 1000miles, you have to change some parts in between and without data, you don't know when. That's why you need it.

[Rex]

I'm not generally arguing that folks SHOULDN'T measure miles. I think folks should measure just about everything their time/personnel/resources/experience allow them to, although miles seems like a relatively low priority item if hours is already being recorded. I'm also pointing out that it seems like a jerk move to tell someone they should be "ashamed" of themselves for not logging tire mileage as a new and relatively inexperienced team, when you can't/won't articulate in one simple sentence how/why logging miles is mission-critical for tires, especially given the fact that tire wear in general is a nonissue in this series. That's really what compelled me to post, and spurred my curiosity of why tire mileage is of such paramount importance. When someone speaks in absolute terms, I can't help but take interest.

Julian, thanks for responding, and to your specific points:
"...both the mileage and the hours, and that's what you need." OK, but why? Please explain why these two items are both NEEDED to make the car go faster. What does mileage do that hours doesn't, and/or vice versa? Has your measurement of miles run on a set of tires changed either a design aspect of your car, or your FSAE event procedures, to produce an advantage? If so, I'm certainly willing to listen and learn if you're willing to share the details. My knowledge of the details of tire behavior is limited, and I'm always up for learning something new. If there is a way I can use this mileage data with respect to tires to make my car go faster over the course of a single event not limited by tire wear, I'm all ears.

"When you look at the dashboard of your road car, can you read the miles or the hours?" Miles of course, or sometimes when I travel abroad, kilometers (which of course mean absolutely nothing to me). Although I would caution that this isn't 100% true as I know I've driven a couple of road vehicles that did in fact log hours as well as miles. But in any case, what does this Q&A prove or demonstrate? My point is that measuring hours run (without accompanying mileage figures) is probably good enough to warrant not being "ashamed" for a second year FSAE car. If that's not the case, please articulate clearly why. If we're making comparisons to road car tires in particular, I typically judge road tire wear by the tread depth rather than the odometer; sometimes even by the wear bars, which I believe is probably what led to the question/confusion about the wear dots on slicks that started this thread.

"In my experience, it is more difficult to clock the hours correctly compared to the mileage. With our cars we often had to abort runs after a short period (maybe 1 minute or so) but still in that minute you cover 1km, it adds up." Fair enough - and this does indeed address my question which is appreciated. If you find it easier to log miles, then it seems like it would definitely make sense to use miles as your guide for part cycles and whatnot. Makes perfect sense to me. I certainly wouldn't say you should be "ashamed" because you logged miles instead of hours, but maybe that's among the many reasons I am not a design judge. However, even with mileage records well under control, finding it difficult to accurately clock hours would be a concern right? After all, per above and for reasons I'll admit I don't fully understand yet, you NEED both miles and hours?

[JulianH]

Rex,
I don't know if I can answer better but I will try:

"Why do you need both?": As Claude said, the car is in different "stress levels" when running slow or fast.
I try an example: Some test days, we just ran SkidPad, over and over again. So in one day we use less than one accumulator charge (<22km) but still spent like 8 hours on the track (adjustments on the suspension and wings take time, some problems, and so on). On other days when you run AutoX, you cover about three times the mileage in the same time. Just because you have much higher speeds.
The stresses on all parts is much higher for the same "hours".

I think it is therefore better to log mileage. The hours help if you want to know at which speed levels you were at that time.
In my opinion, it is sufficient to log mileage (and a nice-to-have to log hours) but not sufficient to only log hours. You just don't know what happened to your car.
At best you know how many miles your car spent on each discipline.

When it comes to make it "faster": Well, some parts make problems (like rod-ends or bearings) after some time. If you know when to replace them before it is too late, you have a big advantage. Also a DNF at the event is never a good feeling...

Nobody needs to be ashamed though. It is a learning process and the team will probably learn to start logging everything they can (maybe don't start with wind speeds and humidity...). As we all know: "The difference between screwing around and science, is writting it down".

The comparison with the road car:
Well it is not all about tire wear. (We also changed tires after they were worn or after the performance dropped massively and not after a certain travelled distance).
Usually the repair cycles are in miles/kilometers, so that you change your oil and other fluids when it's necessary. Of course we could do that in hours too but 250kph on the German Autobahn is different than 80kph in Switzerland

[Rex]

"Why do you need both?": As Claude said, the car is in different "stress levels" when running slow or fast. I try an example: Some test days, we just ran SkidPad, over and over again. So in one day we use less than one accumulator charge (<22km) but still spent like 8 hours on the track (adjustments on the suspension and wings take time, some problems, and so on). On other days when you run AutoX, you cover about three times the mileage in the same time. Just because you have much higher speeds.
The stresses on all parts is much higher for the same "hours".

Are you saying that you experienced higher tire wear per hour running an auto-x course than you experienced running sustained skidpad? That seems somewhat counterintuitive to me, but I'll admit I've never run skidpad for that length of time, as all I do now is auto-x.

When it comes to make it "faster": Well, some parts make problems (like rod-ends or bearings) after some time. If you know when to replace them before it is too late, you have a big advantage. Also a DNF at the event is never a good feeling...

This is true that some parts have a limited lifespan (although I'll admit I have yet to find the limits of my rod-ends after many years of use, even the ones in bending). But we're primarily talking about tires here. A team which can only afford one set of test tires is unlikely to find the lifespan limits of any other parts. On a different note, it would be fascinating if anyone had data showing part failures vs. mileage and vs. hours, but that assumes they ran enough miles to establish a failure pattern, and were happy enough with that pattern to not make any component changes.

Nobody needs to be ashamed though.

I certainly agree with you here!! If I saw forum posts from competition officials consistently reflecting this sentiment, I would stop posting and go back to quietly lurking.

The comparison with the road car:
Well it is not all about tire wear. (We also changed tires after they were worn or after the performance dropped massively and not after a certain travelled distance).
Usually the repair cycles are in miles/kilometers, so that you change your oil and other fluids when it's necessary.

But tire wear is what we're discussing here per the original question, thus is my primary focus. I wonder a racing-use motorcycle engine's oil change interval might be better measured in hours, like many dirt bikes and offroad vehicles are. But again, I'm really just talking about tires here (or trying to keep it just to tires anyway).

Of course we could do that in hours too but 250kph on the German Autobahn is different than 80kph in Switzerland

I'll have to take your word for it, as I don't speak kilometers. Sounds fun either way though!

[Claude Rouelle]

Rex,

The tire grip is a function of many things and two of them is its wear and its number of heath cycles. All other things being equal (and that is a lot of things), the lap time will not be the same with tires of 10 laps "old" or 100 laps "old".

Similarly, if you have two set of tires with both 100 driven kilometers on the same track and ambient conditions by the same driver you will get more grip loss from the one which have 10 heat cycles (10 x 10 km) than the one which made 100 km in just one stint. That is one of the reasons racing team mechanics which use tire blankets (when allowed by rules) cover the tires when the car comes back to the pits; by decreasing the heat variation they decrease the rubber "fatigue".

Look Rex, the whole thing here is barely about tire grip Vs distance; it is to encourage students to be disciplined and rigorous about keeping data of what is done when by who, how and in which conditions.

That you do not know that tire performance is distance dependant that can be acceptable. You now know; that is fine, you need to start somewhere and I am glad you asked.

But making notes of test runs and conditions is a basic principle that you should have been taught or deducted on your own.

As far of the initial "ashamed" you will have noticed that there was a near it. Just have a life and/or ask your shrink to slightly increase your amount of Prozac (again)

It will be nice to meet in person if you come to Lincoln, NE. I will sure be happy to have a chat with you and have a look at your ....test logging book.