District Results -- Car slowing way down

General discussions for car and semi-truck racers.
Post Reply
User avatar
Vitamin K
Master Pine Head
Master Pine Head
Posts: 979
Joined: Sat Apr 20, 2013 7:26 pm
Location: Montgomery County, MD
Contact:

District Results -- Car slowing way down

Post by Vitamin K » Mon Mar 16, 2015 8:19 pm

So, my son's car went to Districts this past Saturday. Altogether, it was a good time. He took the top prize for Bears, and then 3rd overall. Interestingly enough, his car was the fastest one in the regular rounds, and then slowed considerably in the later rounds.

The cars ran a total of 8 times (once on each track in the regular round, then once on each track in the finals). It was a 42 foot Aluminum Freedom Track.

Here were his runtimes:

- Regular Round
2.9643 (l3)
2.9845 (l2)
2.9740 (l1)
2.9935 (l4)

- Final Round
2.9938 (l4)
2.9745 (l1)
2.9891 (l2)
3.0194 (l3)

So what's got me scratching my head is trying to figure out what could cause a car to go from a 2.9643 to a 3.0194 in just 8 runs. I did notice the following:

- The track's stop section was rather worn, so the cars tended to skate up it very quickly and thud into the wimpy padding at the end with a pretty good thunk.
- The guy who was in charge of retrieving the cars got some complaints from some of the parents and kids that he was just dropping the cars on top of each other in the box instead of carefully placing them. (I didn't really see, because I had to serve as Emcee for the event, so I was focused on the racing screen).
- I had meant to get the track wiped down before the race, but it didn't happen, so I'm not sure if debris was an issue.

Overall, I'm pretty pleased because, hey, we made a Sub-3 car! But if we'd maintained our original place, we'd have won the whole shebang, so I'm interested in learning what would cause such a drastic drop-off.

One other note: I only used Hob-E-Lube for both burnishing and lubricating, and I've heard that Hob-E-Lube is kind of coarse and works better with a finer Graphite for burnishing. Would that contribute to the rapid fall-off?



User avatar
Vitamin K
Master Pine Head
Master Pine Head
Posts: 979
Joined: Sat Apr 20, 2013 7:26 pm
Location: Montgomery County, MD
Contact:

Re: District Results -- Car slowing way down

Post by Vitamin K » Mon Mar 16, 2015 8:37 pm

Oh, another observation: His car did have a little bit of tail-end waggle to it. Would that have possibly made it more sensitive to traffic? In the regular rounds, his car was usually well in front of the competition, but in the final rounds, the cars ran very close together.



Speedster
Pine Head Legend
Pine Head Legend
Posts: 1331
Joined: Sat Feb 18, 2012 2:48 pm
Location: Toledo, Ohio

Re: District Results -- Car slowing way down

Post by Speedster » Tue Mar 17, 2015 1:57 am

Team Vitamin K, you guys were FLYING !!!!
That track is the second track we race on. Our fastest time was 3.117 and we were 3" in front of the next fastest car. What are your rules? Might we see a picture of the car?
Congratulations to your Team.



User avatar
sporty
Pine Head Legend
Pine Head Legend
Posts: 3355
Joined: Sun Feb 13, 2005 2:00 am
Location: rockfalls, Illinois

Re: District Results -- Car slowing way down

Post by sporty » Tue Mar 17, 2015 5:14 am

Alingnent.

Other then that. Staging.

Could have had ruff stop section that caused a axle to hit.

Uneven lane.

Many things can cause it.



User avatar
Vitamin K
Master Pine Head
Master Pine Head
Posts: 979
Joined: Sat Apr 20, 2013 7:26 pm
Location: Montgomery County, MD
Contact:

Re: District Results -- Car slowing way down

Post by Vitamin K » Tue Mar 17, 2015 5:27 am

Speedster wrote:Team Vitamin K, you guys were FLYING !!!!
That track is the second track we race on. Our fastest time was 3.117 and we were 3" in front of the next fastest car. What are your rules? Might we see a picture of the car?
Congratulations to your Team.
Yeah, the more I think of it, the more I'm wondering if the track was shorter than 42'. I mean, that's a pretty sick time.

Rules were pretty standard. Only BSA wheels and axles. No stipulations against raised wheels or canted axles. Only powdered lubricants. No lathing or lightening of wheels.

My son's car is a 3-wheeled rail rider. Bent axle rears, aligned with Stan's cantilever bias-weight system. Wheels are stock BSA, selected from a few tubes to get the ones with the least runout (we used Fat Sebastian's gauge design to measure.) Axles polished to 2000 grit. Wheel bores polished with Novus 2 and a pipe cleaner, and then burnished with Hob-E-Lube and a polished #43 pin. Steer set to 4" over 4 feet. We ballasted with lead bars, and the CoM was pretty close to .5" when I measured it.

Here's a pic:
Image



Speedster
Pine Head Legend
Pine Head Legend
Posts: 1331
Joined: Sat Feb 18, 2012 2:48 pm
Location: Toledo, Ohio

Re: District Results -- Car slowing way down

Post by Speedster » Tue Mar 17, 2015 7:29 am

Thanks for the info and picture.
How much weight behind the rear axle slot and how much total weight was added to the car? How much out of round were the wheels you used?
Again, Congratulations. I'm glad your Team isn't in my District. Just kidding.
Cheers,
Bill



User avatar
Vitamin K
Master Pine Head
Master Pine Head
Posts: 979
Joined: Sat Apr 20, 2013 7:26 pm
Location: Montgomery County, MD
Contact:

Re: District Results -- Car slowing way down

Post by Vitamin K » Tue Mar 17, 2015 7:48 am

Speedster wrote:Thanks for the info and picture.
How much weight behind the rear axle slot and how much total weight was added to the car? How much out of round were the wheels you used?
Again, Congratulations. I'm glad your Team isn't in my District. Just kidding.
Cheers,
Bill
I don't have numbers for weight in front of and behind the axle, unfortunately. I just added an approximate amount of lead to the car and then removed it from the front-most section of the ballast to get down to 5oz. The chassis itself was less than 1oz, so there's at least 3.5oz of lead in there. When I get home, I can get the actual numbers for weight on the front and rear wheels.

I think the wheels were in the range of .002-.003 for runout. Since you say you're able to shave down to .001 with the Pro Wheel Shaver, I'm seriously considering obtaining one before next Derby Season, if I haven't jigged up some other way of truing wheels.



User avatar
Stan Pope
Pine Head Legend
Pine Head Legend
Posts: 6888
Joined: Sat Jul 05, 2003 7:01 pm
Location: Morton, Illinois
Contact:

Re: District Results -- Car slowing way down

Post by Stan Pope » Tue Mar 17, 2015 9:42 am

Beccause of the alignment procedure that you used, you have the ability to prove the present alignment without altering the alignment in any way. Not only can you detect loss of alignment, but you can identify the specific wheel/axle affected! (Could life get any better?) That will confirm or reject the question of damage during racing.

If alignment is true to your original settings, then inspect, in turn, (1) trash embedded in tread and (2) DFW inner edge for nicks.

Looking at times on specific lanes, it appeared to me that three lanes showed small losses in speed (about 0.004 to 0.006 sec), but one lane showed a large loss in speed. The three losses seemed a bit high for normal graphite wear. The one major loss in speed could, then, be due to poor staging.

The difference in performance between the various lanes seemed to be pretty large. Did anyone do a careful check of the track section interfaces to assure that all were good? My procedure for checking is to slide a sharp edged block along each side of each lane at each section interface, watching for the block to "catch" as it slides forward across the seam. (Since some tracks have a slight fillet at the junction of the rail to the running surface, a comparable champfer of the long edge of the block is usually needed.)


Stan
"If it's not for the boys, it's for the birds!"

User avatar
Vitamin K
Master Pine Head
Master Pine Head
Posts: 979
Joined: Sat Apr 20, 2013 7:26 pm
Location: Montgomery County, MD
Contact:

Re: District Results -- Car slowing way down

Post by Vitamin K » Tue Mar 17, 2015 11:03 am

Yeah, I definitely plan to re-check the alignment and inspect the wheels/tread for any damage.

I wasn't directly involved in track setup, but I did do a spot-check of the track joins. They all seemed pretty smooth, but this was just my unscientific "finger" test.

I do think, if we sent to Mid-America, I'm going to try blowing out the bores, re-burnishing with a different graphite and then using Hob-E-Lube again for the next graphite step. We'll have to see if that happens, though.



User avatar
sporty
Pine Head Legend
Pine Head Legend
Posts: 3355
Joined: Sun Feb 13, 2005 2:00 am
Location: rockfalls, Illinois

Re: District Results -- Car slowing way down

Post by sporty » Tue Mar 17, 2015 3:38 pm

After you check your alignment.
If you find no changes there.

It is also possible. There was not enough weight placed on the lower part of the track. Below the legs for staging section of track.

There's always a few things to look at.

Freedom track has a slightly different arch. The one at one of the packs had poor joint connectionspeed in a few spots. where the section of track ends got banged up. From taking apart and poor handling.


The spring on the freedom track for manual release lever.

Seen the bolt come loose. Seen flexing a few times there also.
I always felt. The spring tension was to tight and stressed the softer aluminum. And caused flex and a hard snap jerk. When the cars left.


So they added more weight to the bottom . And changed the spring. so it did not jerk.

Actually seen wear marks where it released. The track was only 3 years old. At that time.

The pegs . Start gate pegs had to be watched. They would loosen up during the race. I suggested lock tight.


Poor staging is also something that can cause those time differences.

Especially with your style. Rounded nose. I have seen car staging a bit more harder to do. Because of the shape. Does not want to sit where u want it.
might not have been the case.

But always good to factor that in.



ngyoung
Master Pine Head
Master Pine Head
Posts: 234
Joined: Thu Apr 03, 2014 6:36 pm
Location: Eyota, Minnesota

Re: District Results -- Car slowing way down

Post by ngyoung » Tue Mar 17, 2015 9:14 pm

Comparing lane to lane the times were pretty close except lane 3. First time it hit sub 2.97 and the finals had the worse time of 3.01. Too bad the scoring didn't throw out the worst time but I don't think that is done a lot with only 4 lanes. That one bad run could have been many different things from debris on the track, staging, track shift, bad stop in the previous run, etc.



User avatar
davet
Master Pine Head
Master Pine Head
Posts: 503
Joined: Wed Jan 16, 2013 2:33 am
Location: MN

Re: District Results -- Car slowing way down

Post by davet » Wed Mar 18, 2015 11:08 am

I'm not involved in track setup nor am I a great car builder but to what the others guys say about how it could be anything that affected the speeds I have seen the checkered flags that run alongside our track get pushed up too close and they actually have hung over one lane. The kids want to get closer and closer to the track and eventually the flags were contacting the lane. It was parents that saw it because the MC and track starter were up behind the top of the ramp and couldn't see it.



Post Reply