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Old 08-02-2008, 03:11 PM   #1951
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I have a concern on the FDR for 21.5 / Lipo that comes from the following facts:

a)When USVTA allowed the 4 cell / 17.5 power combination, there was a final drive ratio minimum rule of 4.0 on 1/12/08.
"Next, anyone who thinks that the 17.5 on 4-cells is slower than a stock brushed motor seriously missed the gear ratios. This motor can easily be made to be faster than a brushed stocker, even on a small and tight track." (ApexSpeed)

Also on 01-28-2008 "One, not a single person racing or watching can tell what car had brushed or brushless. And the best point to make was that the two fast laps in the A-main last night were a 13.131 (brushless) and a 13.159 (brushed, and A-main winner). Both cars wheeled by fairly accomplished racers." (ApexSpeed)

b)The spec was later revised again on 02-27-2008 to NO final drive min ratio because the stock motors were still faster. (or were the brushless guys not happy getting beaten with their motor choice?)
"After much deliberating and taking feedback from many tracks and racers around the country, the 17.5 brushless motor final drive ratio limit of 4.00 has been officially removed from the USVTA rules. This includes the Nationals in April. It will allow brushless racers to be able to adapt to different sized tracks without feeling like they have no chance to keep up with well-tuned brushed motors." (ApexSpeed)

Also, on 01-23-2008, 01:57 PM Doug said "Don't bother with calculating rollout—the tires are all the same for everyone." (ApexSpeed)


Anyone who has run this class as long as I have knows the tires "break in" and expand over time, and a FDR limit will result in a very different top speed between new and "broken in" tires.

My questions are:

1) Does USVTA recognize the difference in tire diameter between new and "broken in" tires?

2) If the 17.5 needed a gear limit to even the speed at first, what changed to have the FDR eliminated for 17.5? (just more options? Optiona are good.)

3) How long will the USVTA FDR for 21.5 last, and was it established with new (small dia) or broken in (large dia) tires to compare speeds/times with the other power options?

I can only hope as we enter the new indoor season that the USVTA has gained much knowledge and experience in the past 6 months before they established the 21.5 / lipo FDR.

Marty
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Old 08-02-2008, 03:29 PM   #1952
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Marty we just had a parking lot race in chicago and some very good drivers including some National A main foam tire regulars ....

Here is the low down on all the motor and cell combos......

4 cell brushed motor was the TQ ( chris goetz ) over rob king (21.5 / lipo) and a guy from Indy named Kris( 4 cell brushed)

The winner of the 8 minute main was the 4 Cell BRUSHED motor.

I believe the FDR limit was removed from the 17.5/4 cell combo because that combo is almost identical to a 4 cell brushed motor ( freshly cut ) .. The former FDR limit of the 17.5 is still the best place to gear that motor for The Track at Harbor hobbys(IL) and Trackside as well... gearing up will give you a tad more straight away speed but you will suffer from no infield rip and same goes for gearing down ... better rip but not enough on the straight.

The 21.5 / lipo has a FDR cause it is a Lipo ( 7.4v) I am not sure it will be removed anytime soon cause the 21.5 /lipo combo was right there with the rest of the motor/battery combos.

I personally believe the 21.5 / lipo combo is the best for club racing.. i know its a little more money for the speedo, but you can use the lipo in your regular touring cars, offroad stuff , so you dont have to buy 4 cell packs just for this class. And at the parking lot race i did run the same lipo all day and it just got better through out the day as the cells got warm from the charge and then discharge( race) .

And even with all the talent in the race the club level racers at this event ( guys running all different motor/battery combos) were all very close to the higher talent level guys.
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Old 08-02-2008, 03:34 PM   #1953
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Man, I didn't realize there was a $100,000 prize now! Doug, when was the $100,000 prize announced? How come no one told me about the $100,000 prize?????
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Old 08-02-2008, 05:47 PM   #1954
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I ran at the Chicago race and ran a 21.5/lipo. Thinking about why I didn't do better (was about 1 lap off TQ), was that my speed was a bit too fast for my setup. I was running as close as I could to the 4.2 limit, but my car was pushing at different places. In hindsight, I think I would have been better to gear to be slower to drive the infield better than worry about the straight - which was very long. All the cars looked about the same speed on the straight.

I normally run on a very small carpet track in Indy. The ozite isn't the rubber backed "good" stuff so bite is an issue. Last night I geared my TC3 to the max FDR for 21.5 and really only ended up heating up my motor because I was over-driving the corners. I slowed the car down by dropping a few teeth and the handling and motor temp was much better. I'm beginning to think that unless I have the setup perfect, that I'm not always going to benefit from using max FDR.

Last week I ran a 4-cell/stock combo on the same car. My car was just as competitive as any of the 21.5 lipo cars. The ONLY thing that was killing me was exit speed as my car was bogging down in the corners. Other than that I was able to out-drive the lipo cars into the corners.
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Old 08-02-2008, 06:21 PM   #1955
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Quote:
Originally Posted by 414MPH View Post
My questions are:

1) Does USVTA recognize the difference in tire diameter between new and "broken in" tires? Marty, I ran both tires that were literally about to rip themselves apart, due to age, and fresh tires. I honestly couldn't tell a *straightaway* speed difference. The car was different in the turns, but I don't remember a top speed difference. I actually blew out the tires practicing, and had to put new tires on, so it was almost back to back.

2) If the 17.5 needed a gear limit to even the speed at first, what changed to have the FDR eliminated for 17.5? (just more options? Optiona are good.)

3) How long will the USVTA FDR for 21.5 last, and was it established with new (small dia) or broken in (large dia) tires to compare speeds/times with the other power options? From what I know, a couple tracks were testing this out for Doug, including Mimi's The Track in MD. The tracks both came to the conclusion that 4.2 -4.3 was the right gear. Doug would have to come up with exactly how things went down, but I know these guys were racing the 21.5 for a while. I can't imagine they were slapping fresh tires on constantly.

I can only hope as we enter the new indoor season that the USVTA has gained much knowledge and experience in the past 6 months before they established the 21.5 / lipo FDR.

Marty
Having run 21.5 for the 2 day event last weekend, I'm not quite sure if brushed motors are not faster on larger tracks due to the gear rule. Certainly Chris Goetz and Kris Polonczak (hope that's right Kris) were very fast with brushed motors. I thought that the 21.5 was just as fast, and may have been better out of the corner vs. down the straight, but the racing was very tight and average laps were very close.

ave. lap
1st Round Chris Goetz 16.672 Rob King 16.876
2nd round Kris P. 16.965 Rob King 17.032
Main Kris P 16.627 Chris Goetz 16.747 Rob King 16.634

I tried to use clean runs vs. the ones where there were multi 20 second laps, but you get the idea.
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Old 08-02-2008, 07:26 PM   #1956
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Quote:
Originally Posted by IndyRC_Racer View Post
I ran at the Chicago race and ran a 21.5/lipo. Thinking about why I didn't do better (was about 1 lap off TQ), was that my speed was a bit too fast for my setup. I was running as close as I could to the 4.2 limit, but my car was pushing at different places. In hindsight, I think I would have been better to gear to be slower to drive the infield better than worry about the straight - which was very long. All the cars looked about the same speed on the straight.

I normally run on a very small carpet track in Indy. The ozite isn't the rubber backed "good" stuff so bite is an issue. Last night I geared my TC3 to the max FDR for 21.5 and really only ended up heating up my motor because I was over-driving the corners. I slowed the car down by dropping a few teeth and the handling and motor temp was much better. I'm beginning to think that unless I have the setup perfect, that I'm not always going to benefit from using max FDR.

Last week I ran a 4-cell/stock combo on the same car. My car was just as competitive as any of the 21.5 lipo cars. The ONLY thing that was killing me was exit speed as my car was bogging down in the corners. Other than that I was able to out-drive the lipo cars into the corners.


If you are running on a smaller track you will always wanna gear down no matter what setup your running for power...
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Old 08-03-2008, 10:52 AM   #1957
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Thank you to all that have replied.

From what I read, it sounds like natural motor tendencies regarding gearing are dictating final drive ratios for the various tracks as I would have expected.

I don't have a problem with the 21.5 FDR, just had a few questions. The Lipo / 21.5 has allways been on the horizon and is deffinatly good for the class.

Any feedback on the tia dia question?

Marty
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Old 08-03-2008, 12:22 PM   #1958
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Originally Posted by 414MPH View Post
Thank you to all that have replied.

From what I read, it sounds like natural motor tendencies regarding gearing are dictating final drive ratios for the various tracks as I would have expected.

I don't have a problem with the 21.5 FDR, just had a few questions. The Lipo / 21.5 has allways been on the horizon and is deffinatly good for the class.

Any feedback on the tia dia question?

Marty

How much difference is there between new/worn tires? 1-2mm at best? The FDR is sort of irrelevant because track size and driving style are what counts when selecting your FDR. To think you can just put the minimum FDR on and be competetive on every track is kind of crazy, so don't worry about the few cat hairs difference in rollout. Getting the car through the corners as cleanly and efficiently as possible matters the most.
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Old 08-03-2008, 03:39 PM   #1959
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Originally Posted by 414MPH View Post
Any feedback on the tia dia question?

Marty
I don't know how "typical" my results are, but here are the diameters of mine...

a Brand New, just opened and mounted set are:

64.38mm front
64.58mm rear

very, very, very used rears on asphalt -and roughly 40 mins of runtime yesterday (saturday) alone:

64.28mm front (my fronts are almost bald in a couple of places)
64.5mm rear

so hardly any wear - so tire diameter shouldn't play a part in any roll-out calculation...tire diameter is normaly ONLY for foam tires because so much wears off them run-by-run...
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Old 08-03-2008, 04:59 PM   #1960
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Those are about the same numbers i have seen on fresh tires to old tires..

Not really enough for a pinion change especially since most cases you will actually be able to work under the fdr cause of the different track sizes.... people may find out that they cant run the fdr of 4.2 cause there track is just not big enough so then if you are down a few from the 4.2 you can make an adjustment in pinion size to go along with the very small change in tire size. I think the 4.3 might not be the best gearing for the cars indoors... remember its the max limit that doesnt mean its going to be the fastest for your track.
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Old 08-03-2008, 05:13 PM   #1961
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That's interesting on the tire diameters. I'll have to check mine because my used tires are noticeably bigger. Maybe an optical illusion!
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Old 08-03-2008, 09:57 PM   #1962
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we are recomending a 6.0 for brushless and 9.0 for brushed...when running our club combo of 27t/17.5 and 6cell/lipo....I tried it on both my cars and my speeds were great....and very close as a result of a heat in todays race with 5-6 guys all on the same lap...its not a rule for us but seems to be the right combo for what we are running on a club level.......

ps...I would hope in the near future the USVTA changes the rules on 4cell setup and lipo....a FDR works great IMO and helps keep everyone equal without the 4cell....even running a "FASTER" setup will slow you down with the FDR...we have had awsome results with attendance and FUN factor with what we are running...you dont get this many ppl to show up if you are not doing something right...just hate going against the grain, but it is whats best for our racers and tracks...

our race director said it best......"FUN,FAIR,CHEAP"

this is just my $0.02....and hope it helps some of you get your class built-up to your liking...its a wonderful class to race in and if you get setup right..its limitless to what you can do with it...cya and thanks for listen...
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Old 08-04-2008, 05:18 AM   #1963
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we are recomending a 6.0 for brushless and 9.0 for brushed...when running our club combo of 27t/17.5 and 6cell/lipo....I tried it on both my cars and my speeds were great....and very close as a result of a heat in todays race with 5-6 guys all on the same lap...its not a rule for us but seems to be the right combo for what we are running on a club level.......

ps...I would hope in the near future the USVTA changes the rules on 4cell setup and lipo....a FDR works great IMO and helps keep everyone equal without the 4cell....even running a "FASTER" setup will slow you down with the FDR...we have had awsome results with attendance and FUN factor with what we are running...you dont get this many ppl to show up if you are not doing something right...just hate going against the grain, but it is whats best for our racers and tracks...

our race director said it best......"FUN,FAIR,CHEAP"

this is just my $0.02....and hope it helps some of you get your class built-up to your liking...its a wonderful class to race in and if you get setup right..its limitless to what you can do with it...cya and thanks for listen...
but you are running nothing more than Stock TC with a restricted gearing - oh yeah, and vintage bodies and tires...its missing the point of this class...

We just run a demo on Saturday with EVERYONE running the 27/17.5/4cell combo - and we got at least 12 - 15 mins of run time from the packs...why do you need more?? I cannot think of the number of people that came out to watch that walk into the hobby shop and asked about one of the cars were running outside, I saw at least 2 people leave with kits under their arms...

Are you (or anyone) policing the the gear ratios every run to make sure EVERYONE is sitting at 6 or 9 FDR? What do you do when a chassis does not exactly make a 6.0 or 9.0 FDR?? I think from personal experience (ran/moderated a spec class at my local track for 2 years), that not every chassis get even number FDR - they are usually a little under or WAY over...and right there, you don't have equal cars - and allow room for "massaging"
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Old 08-04-2008, 07:34 AM   #1964
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but you are running nothing more than Stock TC with a restricted gearing - oh yeah, and vintage bodies and tires...its missing the point of this class...
OK. Doesnt Darkside run with us in Calhoun? Where we follow the VTA rules? Even if he is running somewhere that runs six cells and lipo, or stock powerplant. Thats not the same as running stock TC. The shell and tires make that much difference.
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Old 08-04-2008, 07:47 AM   #1965
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somewhere that runs six cells and lipo, or stock powerplant. Thats not the same as running stock TC. The shell and tires make that much difference.
Hey, however people have fun they have fun. It's close enough to Stock TC, though, to be a virtually indistinguishable driving experience. That will, over time (how much remains to be seen) doom the class there to being yet another novelty class. What will give Vintage Trans Am legs is if it provides a distinct driving experience which is exactly what the 4-cell origins of the class created.
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