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Old 01-14-2009, 10:13 PM   #571
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I think someone owes me an apology ......
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Old 01-15-2009, 03:53 AM   #572
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Originally Posted by PartTime View Post
Now I just have to bring the car up to weight and see if it still shines. But I do like it light, very little tire wear !

DK
Around here, it seems that a car that's at weight is kind of doggy. Different animal needs different rules. Keep it at 700-720 and it'll be great with a few adjustments.
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Old 01-15-2009, 06:56 AM   #573
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Just got back from my first race with the 13.5/1c setup.

Now I want to state that I am running very light, a little over 700 grams, but this setup rips !!

Now I just have to bring the car up to weight and see if it still shines. But I do like it light, very little tire wear !

DK

Glad your having great success. Don't go crazy adding weight. Being a little over 700 grams is very good considering that I have seen other chassis at about 685 and run close in lap times.

Less wear and keeping up with the rest of the pack is what it's all about.

Enjoy!
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Old 01-15-2009, 06:57 AM   #574
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Keep it at 700-720 and it'll be great with a few adjustments.

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Old 01-15-2009, 07:33 AM   #575
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I'm all for the advantages of the lighter car but at about 700 grams 13.5 LiPo is much faster than a 17.5 4 cell car. Last time I ran light it was about 2 tenths faster than 17.5 4 cell.

The whole weight thing makes me think that it might be a good idea to investigate running both 17.5's together with the big weight difference.
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Old 01-15-2009, 07:35 AM   #576
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730-740 is where its gonna end up being. next years packs are gonna gain 20 to 25 grams with higher c ratings and capacities so that needs to be taken into consideration when we make the rule so we aren't having to be rewriting it every year. the goal is to keep the weight at a number the avg joe can get to without having to spend all kinds of extra money on aluminum this or titanium that.

im sure the next thing everyones gonna say is why higher c ratings and capacities if this one works fine? well because there are many other mfg.'s out there currently working up there own brew of 1c lipo's and of course they have to be higher in capacity and c rating than whats currently on the market.

btw any more than 730-740 will indeed slow the lipo cars down too much atleast rip wise, as well as defeating one of the main purposes of running lipo in the first place: the weight savings to keep wear and tear down.
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Old 01-15-2009, 08:27 AM   #577
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Originally Posted by Fred_B View Post
I'm all for the advantages of the lighter car but at about 700 grams 13.5 LiPo is much faster than a 17.5 4 cell car. Last time I ran light it was about 2 tenths faster than 17.5 4 cell.

The whole weight thing makes me think that it might be a good idea to investigate running both 17.5's together with the big weight difference.
I would have to agree with Fred. I ran with him and another top level stock driver several months ago running lipo. I believe they both ran their cars close to weight and the speeds were very close the entire 8 minutes. Fred woudn't let me breeth or blink but could tell he had enough to get around me. Two NMH and two lipos finished in a freight train.

I also ran with Part time last night and he put on a great performance! His car was absolutely dialed with 700g lipo. I believe it was a touch faster becuause of the fact that at that weight you can gear a 13.5 at 3.2 and make it scream! Lots of fun though.

Jeremy
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Old 01-15-2009, 10:26 AM   #578
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does this Lipo fit into T-bar cars as well?

any pictures?

Thanks.....
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Old 01-15-2009, 11:25 AM   #579
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On the wire qage issue, wire does offer some resistance. In slot cars they run what they call chokes, its really a low ohm resistor made up of X feet of 18 gage wire. The result is a slight voltage reduction under the initial acceleration, which then goes to almost nothing as you reach top speed. Since the Voltage drop = I (current amps)X R (resistance ohms). On super high amp draw motors it also limits the max current to help the motors live.

Here are the acutal resistance of standard wires in Ohms per 1000 ft: 18 ga=6.5, 16 ga= 4, 14ga= 2.5, 12ga=1.6, 10ga=1

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Old 01-15-2009, 11:44 AM   #580
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Donny you will get a 40C+ single cell in February to play with and help figure out the weight rule. Thanks for all the help on this and I think this class will be the way to go next year. I sure hope the class will be 17.5 to slow things down a bit.
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Old 01-15-2009, 12:27 PM   #581
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Why would we want to go slower than 4 cell 17.5?

The class should be lipo and 13.5 at 730 grams, if the lipos are going to get heavier.

I imagine 10.5 with the lipo would be close to 13.5 4 cell so that should be the intermediate class.

Mod should be unlimited as it is now. With a 3.7 volt lipo the speed will drop.

It was a mistake to make the SMC packs only 4000 as everyone is going to be coming out with there own packs. I for one don't want to be worrying about dumping in MOD.

The bumps on the bottom of the packs are useless and need to be removed. If the racer wants to lock them into place they can shoo-goo something on the bottom just like the SMC 4000 packs.

Also the wire coming out of the pack is too heavy for 1/12th scale. Nobody has that gauge coming off of their speed control. We use 14-16 gauge not 12 in 1/12th scale. I personally want barrel connectors they are way cleaner and easier to use.

Just my 2 cents.

I don't want to ever have to buy a NiMh pack again, LIPO's rule.
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Old 01-15-2009, 12:27 PM   #582
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I've just started running 17.5 with it and it's awesome. Hopefully people will give it a fair chance.
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Old 01-15-2009, 03:31 PM   #583
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OK guys, so I did some testing today with a variable voltage lab power supply.

I connected my 1/12th as is with the following setup to it and varried the power from 3.7 down to 1v to see where everything dropped off:

The hardware that was tested:
Novak GTB 4 Cell Spread Spectrum
HobbyKing - Voltage booster connected to the BEC on the ESC feeding:
Airtronics 2.4Ghz rx
MRT PTX
Futaba 9650

Because its tedious to go down .1v and give answers I am just going to put when significant events happened:

At 3.7v:
the GTB worked fine, and the Voltage booster was supplying 5V to everything else.

At 3.2 - 3.3v:
The lights and the BEC on the GTB kept working but the drive components no longer did anything. I could see the lights changing based on what I did on the radio but saw no results from the motor. Any time I crossed the ~3.2 or 3.3v threshold the drive stopped working.

The Voltage Booster was still sending out 5v to everything else.

At 2.3v:
The Voltage booster starts to drop power and the ESC stars visibly freaking out (lights) any time the steering is turned.

At 2.0v:
THe lights on the ESC go dark now and then but the BEC is still operational, the voltage booster is sending out 3.5v at this point and can glitches quite a bit and browns out.

At 1.5v
The Voltage booster turns off. (which is impressive since the mfg site says 3.5 is the cut off for it, and hobby king says 2.7v is the cut off... this one went quite a bit lower)



So from that ... I dont think there is much of a need for a LiPo voltage monitor, since the ESC stops working at 3.3v. Because the ESC was still seeing signals from the radio when the drive stopped working, I dont think it would matter if the BEC was powering the voltage booster or if the battery was directly. This should be a good baseline for GTB users out there on where that battery is going to fall off and stop going.

Another thing I found interesting, is at idle the setup pulled .3Amp I know the voltage booster pulls more to compensate for the voltage bump, but thats more power at idle than I thought it would be.

Also another observation is when the Voltage booster is under load (servo moving or the server straining) the voltage does vary a bit coming from the VB. The voltage dips as much as .10v when the servo does its thing or has to work at it. Not that bad, but just something to realize.
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Last edited by Clegg; 01-15-2009 at 04:11 PM.
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Old 01-15-2009, 06:01 PM   #584
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Originally Posted by Fred_B View Post
I'm all for the advantages of the lighter car but at about 700 grams 13.5 LiPo is much faster than a 17.5 4 cell car. Last time I ran light it was about 2 tenths faster than 17.5 4 cell.

The whole weight thing makes me think that it might be a good idea to investigate running both 17.5's together with the big weight difference.
After last night, I have to agree. The only reason I did good last night was I had motor on Jeremey. If I was running 17.5/4c I might have kept up but NEVER would of reeled him back in.

I suck at trying to find HP so I might have to wait for somone to come up with a roll out for it and then try. Like I did with the 13.5/1c.

BTW, I took .02 inch off the rears....for the whole night !!

DK
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Old 01-15-2009, 06:41 PM   #585
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Originally Posted by fred kellner View Post
Why would we want to go slower than 4 cell 17.5?

The class should be lipo and 13.5 at 730 grams, if the lipos are going to get heavier.

I imagine 10.5 with the lipo would be close to 13.5 4 cell so that should be the intermediate class.

Mod should be unlimited as it is now. With a 3.7 volt lipo the speed will drop.

It was a mistake to make the SMC packs only 4000 as everyone is going to be coming out with there own packs. I for one don't want to be worrying about dumping in MOD.

The bumps on the bottom of the packs are useless and need to be removed. If the racer wants to lock them into place they can shoo-goo something on the bottom just like the SMC 4000 packs.

Also the wire coming out of the pack is too heavy for 1/12th scale. Nobody has that gauge coming off of their speed control. We use 14-16 gauge not 12 in 1/12th scale. I personally want barrel connectors they are way cleaner and easier to use.

Just my 2 cents.

I don't want to ever have to buy a NiMh pack again, LIPO's rule.
Wow. Sounds more like 4 or 5 cents with all those complaints. LOL
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