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Old 08-17-2008, 09:19 PM   #1
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Default Novak: 21.5 2s with 2s lipo: the lipo solution for the pan class?

I read this on Novak's website:

http://www.teamnovak.com/products/br...ors/index.html

# SS21.5 Pro Brushless Motor is 21.5 turns and is the slowest motor in the SS Pro Series. It was specifically designed to offer oval and beginning drivers an even slower option, which makes it ideal for extended run times (#3421).When using a 2S Li-Po pack, the SS21.5 Pro brushless motor can match the speed of the Novak SS10.5 Pro (#3410) brushless motor on a 4-cell Ni-MH pack.


I know this would be faster than stock, but perhaps a solution for folks who want to run 2s lipo and 4cell nimh together in the pan car classes (1/10th and 1/12th). Anyone know if ROAR/IFMAR would ever weigh in on this?

It would be great if there were nimh 13.5, and 17.5 equivalents as well.
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Old 08-17-2008, 09:33 PM   #2
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It's almost impossible to gear this motor correctly on a direct drive car. Until someone figures out how to achieve a 1:1 ratio and still run a diff, the 17.5 is about as slow as we're going to go with a brushless motor.

That said, and I've been wondering this. Is there something about the brushless motor that inherently generates so much torque? Would different winds, or rotor diameters, or some combination, or someothersuch give us a slower brushless motor that doesn't have the RPM/torque curves that the current motors all seem to have?
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Old 08-17-2008, 09:36 PM   #3
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you'd def need a different chassis then what's available currently. or at least a different battery casing and format.
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Old 08-17-2008, 09:37 PM   #4
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well i just noticed the single cell lipo thread that SMC has going, perhaps a more workable solution:

http://www.rctech.net/forum/electric...cell-lipo.html
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Old 08-17-2008, 09:48 PM   #5
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I don't remember who mentioned this first, but I think its a great idea; rather than worrying about dropping the voltage to 3.7v and then adding receiver packs into the equation, motor manufactures could build smaller diameter rotors to slow the motors down to useable speeds.

I think in the next few months we'll be getting some more info from different perspectives as to whether 3.7v or 7.4v (or even something different entirely) is a better future.

I have even considered trying a 21.5 with a bonded rotor on a 7.4v lipo to see if it compares to a sintered 17.5 on 4 cells . . . not that I think thats a long term solution, but its the closest I can think of to having a replacemnt rotor that would reduce the motors power output.
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Old 08-17-2008, 09:59 PM   #6
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pan cars .. lol lipo vs ni-mh
or is it crc vs. associated
i have a 10R5 and want to run lipos. round cells suck,,,
what do we do now ???
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Old 08-17-2008, 10:20 PM   #7
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the best solution is for somebody to make a high amp 5v regulator small and light enough for pan cars, so then you can run lipo w/o having to worry about a diffrent voltage
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Old 08-17-2008, 10:46 PM   #8
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Batteries are going to be different either way. How about you keep the same motors for each class, just drop the voltage? Having different batteries and motors from every other class makes no sense. Just change the batteries.
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Old 08-17-2008, 10:58 PM   #9
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so.. single cell pan cars.. im game ! whatever motor is fine .
those wires and where they come out . going to have to tape them in. wires in the way ... there needs to be an industry standard or every one will have to enginere a pack for every car . its getting crazy again.
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Old 08-17-2008, 11:36 PM   #10
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It's not going to happen any time soon. In order for pan cars to handle, they need the weight of NiMh cells. The nearest we have is the BMI DB10R, which will be available with a metal plate that takes the weight of a 7.4v saddle pack up to the same as an NiMh.

Now that LiPo needs balancing, heating and matching before you get a competitive car (that's what's happening here), and the NiMh EnerG cells are so well behaved, there's no advantage with LiPo in pan cars.

LiPo isn't the future, it's just a stepping-stone to the future where ABC cells will transform everything, and have a more suitable voltage (6v( that more closely matches a good NiMh pack, with none of the problems and potential safety issues of LiPo.
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Old 08-17-2008, 11:42 PM   #11
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The 21.5 was built for our OVAL Pan Car series, along with the now DEFUNCT Arcor Oval Organization as a slower brushless/lipo combination.

In testing it was discovered that this combo run virtually identical to the speeds of the 13.5/4 cell class (Pan Car on Oval)

As far as gearing - on our LOCAL Parking Lot type OVAL track I use a 100/62 gear combo, on our 250 meter Bicycle Velodrome we're using a 76/62 (And it runs 10.2 second laps on a 820 ft. track. (Which is 54.8 MPH)

These are powered with the ORION 3200 "Carbon Edition" Lipo.

21.5/LIPO = +/- 13.5 4 cell SPEEDS
17.5/LIPO = +/- 10.5 4 cell SPEEDS
27.5/4 cell = +/- 27t Stock Brushed/4 cell SPEEDS

On the parking lot oval, the track diameter is 110 x 80, and the tire size is 2.20" (so you can do the ROLLOUT Math)

On the VELODROME 820 ft. runline 2.48" tire diam.

The 21.5 NEEDS Gear - but DON'T be afraid to USE IT...you think you are TALL ENOUGH - add another 6-8 teeth.
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Old 08-17-2008, 11:45 PM   #12
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Quote:
I have even considered trying a 21.5 with a bonded rotor on a 7.4v lipo to see if it compares to a sintered 17.5 on 4 cells . . .
Andrew,

We had thought about trying that - but than HEAT and disposable ROTORS become even MORE of an issue. I think the speed would be pretty close w/o the SINTERED rotor...but when we had NOVAK do the 21.5's I recommended them NOT making a NON Pro Version...(Mainly cause I figured they'd get greater sales only building ONE motor.)
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Old 08-18-2008, 06:48 AM   #13
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Quote:
Originally Posted by SWTour View Post
Andrew,

We had thought about trying that - but than HEAT and disposable ROTORS become even MORE of an issue. I think the speed would be pretty close w/o the SINTERED rotor...but when we had NOVAK do the 21.5's I recommended them NOT making a NON Pro Version...(Mainly cause I figured they'd get greater sales only building ONE motor.)
I agree its not a solution, I was just wanting to see where it fell so I could use it for my self. I'd much rather see a motor company develop a smaller/different "pan car" rotor identifiable from the shaft, that dropped the speeds rather tahn building whole new motors. It would keep their costs and our costs down; they only have to reengineer one part, and we only need to replace one aprt and opur motors are good for sedan and pan cars . . .

I'm certainly looking and thinking about other options though. Im curious to see how the 1 cell and a receiver pack works. On the surface it sounds like a hassle, considering having two batteries to charge before each race and different voltages and capacities for them at that, but we'll se. : )
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Old 08-18-2008, 07:10 AM   #14
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Has anyone tried the A123 cells yet? I don't know much about the cell configurations but wouldn't 6.6v be a lot easier to figure out motor/receiver/esc-wise? Also, since it would be a 2 cell pack it would be a little heavier than a single cell LiPo and you could always do what the offroad guys are doing with their LiPo buggies and truck which is add a 14 guage stainless steel plate underneath the pack to get it back to IB4200 weight. Just a thought that ran through my muddled head.......thoughts? Opinions?
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Old 08-18-2008, 07:31 AM   #15
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My personal feeling is that single cell voltage is the way to go. With single cell voltage you can run the same motors that the 4 cell guys run and even run with them in the same class (even with it being slower). No new motors, just a pack and in most cases the ICE/Checkpoint charger that you already have.

Switching to the 2 cell voltage and 21.5's will make the cars faster than what they are currently. From what I've been seeing in 12th is that the slower classes need to be slower. New people are having problems running with 17.5's because of the speed. There are other classes that people can run if they want to go faster than the slowest class.

When I ran single cell LiPo before CEFX closed, the spec classes were slower on single cell voltage (17.5 and 13.5). Mod was just about as fast on single cell voltage if you ran a hot motor (3.5 turn). Runtime wasn't an issue on single cell voltage but it was on 2 cell voltage because you had half the capacity (about 2400 mAh for what I ran).

We all pretty much think of the class that we're running when it comes to the 4 cell LiPo issue but all of the classes need to be consitered. 2 cell mod will bring in a huge number of issues for a lot of people and people will be able to dump in 8 minutes. Dumping in LiPo is hard on the cells.
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