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Old 10-01-2013, 02:26 PM   #1
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Default How come TCs haven't gone to short packs yet?

With all of the new off-road cars coming out that are capable of or designed to run short packs, it makes me wonder why TCs haven't moved in this direction as well. I would think that a short pack car could be better balanced than a full pack car. Is the problem meeting minimum weight?
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Old 10-01-2013, 02:28 PM   #2
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You nailed it. You can by all means run a shorty, but then packing on all the lead weight? No thanks.
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Old 10-01-2013, 02:42 PM   #3
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Shorty packs tend to have less capacity and higher internal resistance than full-sized batteries.
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Old 10-01-2013, 02:43 PM   #4
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I have run shorty packs in a TC but I believe they run out of steam/ punch, before the end of the main If the main was longer then 5 minutes for instance I would TQ the heats and lose a 7 min main in the last 2 or 3 laps sometimes with a 1/2 lap lead. TC put a lot of pressure on the batteries more then a off road car does. IMHO
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Old 10-01-2013, 03:23 PM   #5
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But I think at least worth in blinky class, in fact i am also looking for running with a car modified to using short packs in next year, not in 5min but in 8min.
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Old 10-01-2013, 03:30 PM   #6
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I run shorties in my 17.5 TC5. I moved the speedo over to the right side of the chassis. I was able to put the extra weight, in the middle of the chassis, under the belt. It made balancing the L/R weight much easier.
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Old 10-01-2013, 03:38 PM   #7
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Several Mi5 drivers are using shorties. I tried it briefly but liked how the car worked with the full battery and went back instead of pursuing it further. I don't know that there is a lot to gain since the cars are fairly well balanced already and around minimum weight.
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Old 10-01-2013, 04:25 PM   #8
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Originally Posted by kawi650 View Post
With all of the new off-road cars coming out that are capable of or designed to run short packs, it makes me wonder why TCs haven't moved in this direction as well. I would think that a short pack car could be better balanced than a full pack car. Is the problem meeting minimum weight?
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Old 10-01-2013, 04:53 PM   #9
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I think in the future we may see cars designed just for shorties. Battery density is going higher. A few years ago, it was just 3800mah shorty packs. Now we have them up to 5000mah. Some 1/10th 4WD offroad cars are being designed to use shorties as well.

But I have to agree that onroad is much more tough on batteries than offroad, even in blinky as well in current 6 minute mains.
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Old 10-01-2013, 05:41 PM   #10
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Current ROAR rules for electric racing require that the battery tray/area be designed to accomodate a full sized battery. I also believe that you cannot put anything other than the battery in the battery tray/area, with the exception of foam spacers to secure the battery.

According to http://www.roarracing.com/downloads/..._Rule_Book.pdf (electric class rules start on page 37), here is the rule about 2S lipo dimensions:
The maximum 2s brick/stick case:
Length: 139mm
Width: 47mm
Height: 25.1mm


Most major R/C car manufacturers design their top touring cars to be legal to compete at major events by ROAR, IFMAR, etc. It is unlikely that you will see cars specifically designed for short packs until the rules change.

Also the rule was implemented to prevent chassis manufacturers from designing battery trays/areas with unique dimensions. The reasoning was to prevent having to use a specific battery for a specific car (to help keep competition open between manufacturer).


As others have stated, you can use shorty lipo packs. In slower classes (USVTA/USGT) quality shorty packs are not a disadvantage. But any weight savings in faster classes are offset by less performance when compared to full length 2s lipos.
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Old 10-01-2013, 06:24 PM   #11
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What would be the gain if standard size packs work very well now?
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Old 10-01-2013, 07:05 PM   #12
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wow, that may be a real rule but that to me is total horse crap. sure mandate a design that fits a full size industry standard battery, fair, but telling the user what he is and isnt allowed to put there is total horse crap lol....

nice thing about shorty packs though, you can add weight in more desireable places on the chassis and modify the forward/rearward bias without having to move the heaviest components on the chassis.
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Old 10-01-2013, 07:22 PM   #13
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I believe IFMAR doesn't have that rule as there were many cars running shorty's, either 2wd or 4wd. If you wanted to run a full size pack or saddles you had to reconfigure the chassis.
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Old 10-01-2013, 07:24 PM   #14
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Pretty easy to get around the ROAR rule with a TC design. If you wanted to do one of these designs where the motor is mounted centered with a shorty pack in front of it also centered, all you need to do to pass the rule is have tape slots or mounts to mount a full size pack transverse (side to side instead of the normal front to back) right through the middle of the car.

Would that be an ideal arrangement for a full size pack? No of course not but who cares? It's just there as an option to conform to the rules, not for actual use.
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Old 10-01-2013, 09:05 PM   #15
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you misunderstood the roar rule.
It states that the chassis need to be designed that you can use a standard batterie.
This doesn't mean you can not configure it your self to accomiate a shorty lipo.
This rule is only made to prevent that a company invent a chassis is only useable with there special lipo. That's it nothing else.
BTW this rule came out as Losi brought us the 22 and the first shorty lipo.
From my point of view this rule is now worthless, because you can buy a shorty lipo from the most rc company's.

Last edited by silden; 10-01-2013 at 09:08 PM. Reason: Typo
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