NASA 25 Hours of Thunderhill Race Report

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PostPosted: Tue Dec 05, 2017 10:52 am
Well, first off, we did it! We survived the 25 as they say. Race started at 1100 Saturday and ended at noon Sunday.

611 Laps, about 1800 miles, 111 gallons of fuel, 2 sets of Toyo 888 tires, one set of brake pads. We had very little down time. Down time was refueling and changing drivers roughly every 90 minutes, replacing a thrown alternator belt once, replacing the alternator belt a second time and this time fixing the broken alternator bracket, swapping the day nose for the night nose with lights, and changing to a fresh set of tires at about 18 hours. That’s it, the rest of the time we were circulating running an out 2:00 laps. The fast guys was doing 1:40s and the slow guys were doing 2:30’s so we were passing and getting passed almost every lap. We ended up finishing about 30th (haven’t seen final final results yet), but the goal was to finish and top 600 laps and we did that!

This is an interesting race. 55 total entries this year, several Pro or semi-Pro teams (Flying Lizard, Fall Line) that use this race to practice for those shorter races at Daytona and LeMans 
The tire budget for the Pro teams was north of $100K alone, they swapped out all 4 tires every pit stop. Our little team had a total budget of $16K split between the 4 drivers. Our drivers, me, Bob Breton, Mike Boyle, Steve Zadig are all current or ex SRF/SRF3 drivers.

Each driver got 4 stints. I have to say that the second night stint for me (0230-0400) was the hardest. It’s late enough with no sleep you are tired already from 2 previous stints in the car, it’s cold and dark (wore an extra top layer of nomex). And when you get out on track about ½ the reflective markers you were using for brake, turn in and apex) have disappeared from the previous night stint and it’s like learning some corners all over again! Seeing morning come was almost cause for a Druid ceremony. You survived till sunrise, now only 4 ½ hours to go.

Overall I was once again very impressed with the quality of the driving. The fast guys (Audi R8 wth Flying Lizard, the Fall Line and other Porsche Cup cars, the Ginetta’s and Radicals) did a very nice job of not dive bombing when we were committed to a corner and (during the day when they could see a point by) did a nice job side-by-side in the corners when we pointed and left room.

For those interested, the car (pic attached with day nose for start of race) was a slightly modified Gen 3 SRF. Drive train was stock sealed SRF3. Nose was lengthened to fair in headlights, a splitter added, tail lengthened and wing added. Brakes, suspension, drive train stock SRF/SRF3. The aero really did help, you could noticeably feel the front end washing out in a corner when closely following somebody, if we’d run the SRF spec Hoosier tires, I’d guess the car would be 4-5 seconds faster than a stock SRF3, but then we would have gone thru 5-6 sets of Hoosiers compared to only 2 sets of Toyos. Slight correction on the suspension. We were using aftermarket Penske shocks not the sealed Enterprises Penske, and slightly stiffer springs.

NASA Press release is here: (and no we are not mentioned in the press release )
https://nasaspeed.news/race-coverage/to ... rformance/

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Todd Butler
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PostPosted: Tue Dec 05, 2017 11:04 am
Awesome! Stock fuel cell or something bigger? IIRC you guys have a fuel opening cut in the tail?
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PostPosted: Tue Dec 05, 2017 11:12 am
pmiranda wrote:Awesome! Stock fuel cell or something bigger? IIRC you guys have a fuel opening cut in the tail?


Ya forgot to add, 12 gallon fuel cell installed, so the fiberglass seat was moved forward about 3 inches. And we did have a fuel flap in the tail. 90 minute +- stints worked out about right, some we streched to 100+ minutes. Typically it took slightly less than 10 gallons at each refueling stop.
Todd Butler
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PostPosted: Tue Dec 05, 2017 12:52 pm
Thanks, Todd, for the report. As Todd noted, we had very few issues and excellent pit stops (scheduled more or less every 90-95 minutes, and most under 5 minutes with most time getting drivers out and into the car). I managed to be the driver for two of the lost alternator belt stops, the first happening, fortunately, just as I coming into the last corner, so I was able to dive into the pits before water temps came up. The lower alternator bolt had loosened up so belt came off. Fortunately, Ric implemented the alternator belt "retention system" after the first loss (tie wraps between the frame and alternator mount ;-) so we didn't lose the belt on the second loss. The second lost belt turned out to be caused by a broken alternator bracket (a common Gen3 theme), but Ric was able to weld it together and it held up for the remainder of the race.

My only big adventure came in the post-midnight stint. I wasn't feeling great by the middle of the stint (deja vu from last year) but thought I could make it to the end. Then, the we lost the right front headlight (and I lost my <fill in the blank>...) Fortunately, it turned out to be a connector that required a bit of surgery on the nose to fix, but eventually we got going again (and, fortunately, it was time for the driver change, thankfully!)

My favorite stint came just before dawn, with just enough light to avoid the issues I had in early morning stint, catching a beautiful (but a bit blinding) sunrise and still a very strong field of cars to pass (and be passed) pretty much several times a lap. Some very interesting "hardware" out there, including a 50's? vintage Studebaker with some 600+ hp. Never saw a car pitch-and-roll this much in a corner! Scary fast in a straight line (just plain scary to follow through the corners!)

We were definitely the "tortoise" in a "hare" field of scare fast ESR's capable of running sub-1:40's to our best time in the high 1:59's. We did exceed our personal milestone of 601 laps by about 10 laps, even with the additiojnal 4-5 stops for alternator and light issues, plus a 10 minute penalty at the end for an accidentaly pass under waving yellow. Also, though, it didn't show in the placement, we did take the checkered flag at the end, while some of the faster ESRs had been sidelined for many hours with mechanical failures and accidents (one involving the aforementioned Studebaker).

This was our first time running the Toyo R888R's (last year we ran the R888). I was impressed with the stability and feel of the tire compared to the R888 as it had great grip and stability even at full tread depth. I set nearly identical lap times on my first session (with less than an hour on the tires) and my last session (about 6 hours on the tires.) Though we changed tires mid-race, looking at the tires at the end of the race, I suspect we could have easily gone the distance on the fronts and pretty close to the end on the rears. Quite an improvement over Hoosier life expectancy which we estimated at 4-6 hours, at best, based on prior testing at Thunderhill. If we ever decided to look for another tires, I would definitely put the R888R's high on the list.

Congratulations to Ric Heer for getting the car put together as this was a major ground up rebuild since last year, with the chassis stretch 3 inches to accomodate taller drivers, adding the AIM EVO4S and Steering Wheel 3 to the car (made for a great dash setup and warning lights came in particularly well to catch the alternator belt failures), and the new Butler Head Restraint (a welcome addition that my head and neck are quite thankful for to help survive the 90 minute stints). And, Mike and Joe, the pit crew that stayed up all 25 hours with flawless and fast stops, and jumping in to fix all the minor emergencies that came up.

Finally, a great drive with Steve Zadig taking the opening stint (starting mid-pack in a 55+ car field and surviving the first few laps is a major accomplishment!), with Todd 3rd and Mike Boyle the 4th stint (and the honor of taking the checkered flag). All the lap times were impressively fast and consistent (Mike's night lap times were amazingly fast!)

All-in-all, a great adventure getting there, and a great feeling to see the checkered flag after 25 hours!
Bob Breton - SRF 51 - San Francisco Region
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PostPosted: Sat Dec 09, 2017 5:39 pm
Great job guys! I know SRF's have done this race in the past with modifications and good to see you carrying on the tradition. I would love to know more about the mods you did the car, specifically the bodywork. Was it all just take a best guess with the design of the additional pieces or was there real data gathered?

Always be fascinated with the design of cars, have probably read all of the mulsane corner webpage a dozen times. I am really curious how much an improvement the trailing front fender pieces would do just themselves over the standard car bodywork? cleaning up flow and aiding in air extraction and such.
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PostPosted: Sat Dec 09, 2017 8:52 pm
Congrats guys, well done! It was good to see you on grid.

We also had 3 SRF drivers in a Norma (myself, John Black and Steve Fogg) owned by Phil Fogg Jr., who was our lead driver. We had a good run, and led the race heading into hour 4, but penalties and a 1-hour repair due to contact set us back to 15th or so. We finished 4th overall, only a lap down from 3rd, and 2nd in class (ESR). Not bad for the first attempt by the car, kudos to Jason/Chris @ Bulldog for prepping a great car, and Vic & the flatout team for running a tight ship.

I have to say that driving an SRF is orders of magnitude more comfortable, the Norma beat the hell out of us :-)
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PostPosted: Sun Dec 10, 2017 1:49 pm
Chris,

There were a number of mods on the car that aren't externally visible. Front the photo you can see a bit of the splitter that replaces the standard aluminum nose pan under the radiator, molded out of fiberglass, with some carbon fiber reinforcement. There's quite a bit of downforce generated by that component. In early testing a few seasons back, with just the front splitter, the car was almost undrivable there was so much downforce on the nose (which is why we ended up with the wing on the back and substantial spring/shock changes).

One of the strange lessons in trying to get more rear grip was in trying different rear spring rates. Normally, you'd expect that softening the rear springs would help; in our case it didn't. Finally, just for fun, we tried stiffer springs, and suddenly the car became more driveable (this was before we added the wing.)

There's a completely different shock/spring setup on the car. Shocks are adjustable in both compression and rebound. Don't recall the brand, but the advantage is that there's more suspension travel and ability to use more readily available after-market springs vs the standard SRF package. I don't recall the spring rates, but they were substantially higher than the stock SRF setup. Overall, we didn't spend too much time trying to fine tune the settings, but the feel was a bit more compliant than the Penske's but still effective in damping. If Enterprises ever considers a change in the shock package, I would certainly recommend this option (though I don't have information on cost I expect they would be competitive to the Penske's).

The rear wing is pretty obvious, and it does help to balance the car, especially, with the added downforce of the front splitter. T8 at Thunderhill is a very fast kink (and where aero imbalance really shows up as I discovered in the initial non-wing setup without the wing) and was very neutral and could be taken without a lift (except at 2am for me when it was pretty tough to see the apex marked by a single reflector!)

Ric Here custom-built the tail and nose sections and are extremely light since we don't have a weight rule. I can say that the extended tail does work to reduce rear lift in the standard bodywork. We did a side-by-side comparison in pre-wing days, and a flat tail with a slight wickerbill had very dramatic impact on high speed stability due to reduction in lift/increase in rear downforce. This is an area that is likely to go through future iterations as we look to reduce to overall profile and drag. While I haven't looked at back-to-back numbers, I suspect, based on terminal velocity into T1, that were giving away a bit of top end for the increased downforce. Plus, there's an opportunity to "modernize" the look.

Other than thicker after-market rotors (which we've been using since before the introduction of the current rotors), the rest of the drive system is stock.

In the cockpit, we had the new Butler head restraint, which saved a lot of neck pain as it was in the perfect position to relax the head in the long, high G corners like T2. At first it felt a bit hard, but once I learned to lean into and not bounce my helmet against it, it was actually quite comfortable to drive with and more supportive than the "wings" I've been using for years. Highly recommended upgrade for everyone. Only complaint is it can complicate getting in-and-out of the car, though I eventually was able to get in and out fully helmeted. The AIM Steering Wheel 3 was removeable to help the taller drivers, but I was able to get in and out with it in place. I really liked having everything on the steering wheel, with the custom dash having only the switches and Gen3 lights, and a big, bright alternator light, in addition to the warning lights on the steering wheel (which I highly recommend in place of the wimpy, standard alternator light to catch those inevitable alternator belt failures!)

Where we are looking for future improvements are in the alternator output (insufficient run a second set of lights in the car), and the alternator belt/water pump drive system. IMHO, these are the weakest points of the Gen3 package. I'd like to see a separate drive for the water pump, or some other option that would avoid an alternator belt failure leading to a potential fatal engine failure. A couple of areas that we saw that could use a short term fix were the lower alternator bolt, and the upper alternator bracket. The lower bolt has too much play (I suspect it was a compromise to fit the Gen3 bracket to the existing alternator.) One option considered is to "sleeve" the alternator bolt hole to match the Gen3 bracket bolt size, with a different material that's less susceptible to getting "hogged" out or loosening. The upper bracket also broke in half (something that's happened to my Gen3 as well). While I believe a thicker material is now available, my thought is to go to something more like the old Gen2 design with rod ends that won't be susceptible to loosening like the slip fitting of the current bracket.

We looked at potential alternator options, but were, unfortunately, unable to find a suitable component that would fit into the existing location. This is more of an "enduro" consideration as the stock alternator is adequate (though expensive). I can certain attest to the need to have more lighting, especially peripherally, as it was nearly impossible to see the apexes at T10 and T14, so eventually I was using "muscle memory" and other reference markers more than vision to make the turns.

As noted earlier, we have a 12 gallon fuel cell (though we discovered it had shrunk a bit over time) with quick fill attachment and filler flap in the tail section. We ran conservative session lengths (90 minutes) but could have likely run a bit longer. Based on our fuel consumption calculations, we estimate that our average for the 25 hours was ~17mpg and we ran nearly 1800 miles, based on our lap count.
Bob Breton - SRF 51 - San Francisco Region
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PostPosted: Sun Dec 10, 2017 6:28 pm
Many thanks for that! Now to add a few thousand words - any pictures of chassis extension, "night-nose," etc?

Is the splitter cored?

Maybe Todd - or Ric H. could add some - as time is available. I'd even sign an NDA for a PM of details if you'd like! These are all areas on my list of "things to explore" in SPU in SEDiv.

TIA and Cheers - Jim
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PostPosted: Mon Dec 11, 2017 4:17 pm
Thanks for the details! I am not sure where you are based out of, but one thing I would say is maybe get some FSAE students involved and bam you have access to all those resources they have, especially computer related. I am sure it be a long long drive but keep in mind about some Enduros we are doing here in Cend-Div next season.

As for the front splitter only and no rear wing I could see how that would be terrible to drive. All that pressure is in the forward part of the car. By adding the wing I would assume it moved the center of pressure back. Great way of understanding this is read on the changes to the indycars for next year. The problem with the past body kits is that the center of pressure was really far back due to the bumpers and all the aero fins they had. In regards to the splitter is the floor completely flat under thecar from splitter back or do you have cuts after the front splitter thus having it also act like a front diffusor?

As for the alternator issue, to run extra lights...have you thought about using the old style bicycle generators that just rub against the wheel? :lol:
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