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Old 01-16-2008, 10:13 PM   #1
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Default 12th Scale (and oval) and Lipo - Making it work soon.

Yes, you knew it was going to happen after LiPoly and Brushless were approved by ROAR in 6 cell applications..

Now its time to look at getting some loving for the 12th scale and oval guys.

Your mission, should you choose to accept it, is to figure out what capacity you can get in an area of 23mm H X 92mm L x 49mm W. This is the total area of my "link style" 12th scale 4cell side by side battery area. You could also use the 44mm dimension to keep the adjustability in the car.

T Bar cars.. T bars are 22mm wide so you'd need a jumper to clear that. 43mm W X 46mm L for saddle packs but most current tbar cars have part of the battery sliding under the mid-deck where the center post mounts to so some shifting would need to be designed into them.

I figure there's some math to get a rough idea on capacity..

Thats the first thing.

7.4v or 3.7v.. lets compare
1) somebody was saying it took an 8.5turn to = stock speeds?? any clarification on that?
2) Some of us could use that motor elsewhere but definitely not the majority.
3) Still need a rx pack - more stuff to balance in the car and things to go wrong, replace, etc.
4) do servos even work at this low voltage??? or is some great new servo redesign needed thats going to toss all those other servos i have out to pasture?
5) needs an LVC???
6) both weigh less

1) don't need that rx pack, less glitch related issues or drop outs.
2) escs already exist with lvc to handle these
3) both weigh less
4) anything else i'm missing??

Second thing is brushless motors.

Where do we go on winds. Use 17.5?? do we go 21.5, lets get some input from the guys doing the testing with pan cars. with 3.7 the rumor was you had to motor way up and I can't see any joe blow using it elsewhere. Some guys are discussing going to smaller motors like a 380. I have no use for them elsewhere. I don't need a redesigned 12th scale in the next year to "take advantage of the smaller size" nor do i want the 12th scale of the month syndrome. We have to ask ourselves, at what point does 12th scale not actually measure up to 12th scale?? 12th scale of what?

I'm for keeping with 05 or 540 size brushless motors
a) i use them across the board with my other cars
b) goes with a.. back up motors are the same..
c) parts between the motors would in theory be the same
d) roar will be approving some of those that we will use shortly lol
e) I think changing the size will severely segment 12th off from the potential growth to be had.

So let's get some constructive banter going like the BL/LIPO thread.
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Old 01-16-2008, 10:43 PM   #2
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Originally Posted by Mason View Post
We have to ask ourselves, at what point does 12th scale not actually measure up to 12th scale??
If you do race 1/12 scale, I apologize now, but NONE of the actual 1/12 racers that I know are in any hurry to run LiPo. Those of us that do want to run brushless are already doing so.

I don't subscribe to the "NIMH of the month" club, I buy race packs once a season, and I've never vented or exploded a cell. I'm in no hurry to run LiPO in my cars. I've had plenty of experience with them in airplanes and helis so I'm in no way anti-LiPo, I just don't see a need to tamper with a successful formula.

I'm sure that sometime soon we'll see a new battery chemistry come along that has the weight, size and voltage to replace NIMH directly. I say let's wait it out.

If I've come off as bashing your post, then I apologize again. It's not my intent.
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Old 01-16-2008, 10:57 PM   #3
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We are going to be at a cross roads here with 1/12th in the next few years probably. With LiPo getting very popular and now legal under ROAR rules the hobby seems to be heading in a direction away from Nickel based batteries. This poses a problem for 4 cell classes in that there really is no voltage equivalent to a 4 cell pack and in 1/12th scale there are space issues to be concerned with. Even if new LiPo packs get to the point where they can be mounted to the same area as our current NiMh packs, the reduction in weight of the batteries is likely to trigger new designs to rebalance the cars. This has caused some people (myself included) thinking that it might be time to reinvent the class and maybe move to a smaller motor. It might not be either but it's a good time to look into it at the very least.

Personally I like the idea of going to a smaller motor like a 380 (360?) because of the possibilities it opens up in body design, additional chassis space, and things I can't even fathom yet.

It would be interesting to hear from some of the manufacturers on this. Perhaps there is even a cell of comparable voltage and size in the near future that we are unaware of.
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Old 01-16-2008, 11:22 PM   #4
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up here in the north I have seen some 1/12th racers running a three cell single voltage in their on road car.

I believe it was a 1300 mah x 3 cells = 3900 mah. The gentleman had a receiver pack using a LRP brushless speedo. I have no lap times to tell you how the speed was but at the club they were using 13.5 novaks. I believe the gentleman ran a 10.5 for his runs. Seemed faster than the 13.5's.

He said he has run without receiver pack with no problems. He ran a Genx so it fit just like a regular pack. He also said he needs to add weight but overall was just fine.

There are some pictures. I will post later. The Lipo was in a lexan hard case shrink wraped.

I think single voltage would be just fine and plan to run the same thing in my 1/12th car.

Heck this would also be a way to slow cars down.

Roar should of included 4 cell as well. Rule for 4 cell lipo replacement could of been as follows. Hard case, same size, single cell voltage 3.7v-4.2 v. Use as many cells as you like as long as you keep same dimensions.

Oh well it will just take some more information to show Roar that it can work.

Why not be out front instead of catch up. Oh well all in time.
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Old 01-17-2008, 12:05 PM   #5
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Some radios may be able to work with a voltage that low but for sure the Spektrum system will not. Sounds like they were using 3 cell 1/18th scale packs. I wonder how well those smaller packs will hold up to the amp draw of a 540 sized motor over the long term.
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Old 01-17-2008, 01:51 PM   #6
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yeah I posted something about this in the lipo thread with no response...

I was thinking 2 in parallel and 3.7v but then I really wasn't thinking about personal transponder issues and receiver issues.

good point.

I know 12th uses more battery than touring etc. due to increased run times so we need to make sure that it will make run time especially for 19 and mod classes... we are pushing the limit as is with 4200 and 4600's...

I think 7.4 is really WAY too much back in the 90's stock 6 cell ran with 4 cell mod and even back then 6 cell stock was faster than 4 cell mod it just didn't handle as well. I'm sure that not the case now as mod is stupid fast now, but the problem will still be there..

we'd probably have to run 21.5's to even get close to what stock is now and I'm not sure that's slow enough...
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Old 01-17-2008, 01:59 PM   #7
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Originally Posted by Tempest2000 View Post
I was thinking 2 in parallel and 3.7v but then I really wasn't thinking about personal transponder issues and receiver issues.
This will work but you will NEED a receiver pack. But many drivers use a receiver pack with 4-cell.

3.7V is not slow. It will not be as fast as the same set-up with 4.8V, but you will be able to carry much more cpacity with a 3.7V LiPo so you can gain back soe of the lost speed with faster motors or a step up in class. OIr make 1/12 races longer.
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Old 01-17-2008, 02:07 PM   #8
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You don't need a rxr pack as such but rewire using a single aaa battery or even smaller size in line will allow you to run your 3.7 volt pack even with spectrum.
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Old 01-17-2008, 02:17 PM   #9
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Most of the 1/12 guys I see are more "racer" types-people who are not upset with current Nimh batteries. They probably even like them.

That's why i think it may be worth it for everyone to wait a bit for batteries to catch up with us. A friend of mine who races, and is in the electronics industry, says there are batteries that would be much better suited to 1/12 than what is out there now, but they are just not available, yet.
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Old 01-17-2008, 02:22 PM   #10
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I've run both voltages in 12th and either one is fine with me. With the 3.7v stuff you have to add a receiver pack. One advantage of having all of the cells parallel is that they can handle the higher currents.

A single cell pack that is 5400 mAh will only handle 54 amps at 10C or 81 amps at 15C. This is enough for pretty much all of the motors that we can throw at it even in mod.

If you go with 2 cell voltage, the capacity goes way down (about 2700 mAh) and you'll have problems with dumping. The capacity will be what limits the speed here, not so much the motors. Haven't tried a 17.5 on 2 cells but I'd bet that you could dump with it.

Even though I would prefer 2 cell voltage in mod, the pack wouldn't handle the current (27A at 10C and 40A at 15C). We'll be spiking the pack above this in mod and it will probably hurt the cells. The cool part is that 12th would be oldschool again and you'd actually have to use strategy along with driving the car. That would be a good thing if you ask me.
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Old 01-17-2008, 02:32 PM   #11
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I agree I like the idea of 3.7 better I guess we'll all just have to run a lipo receiver pack too...

3.7 will be plenty fast... mod will still be ballistic 19 turn now is almost as fast lap time wise as mod at the national races

stock is stock its not supposed to be fast but 13.5's at 4.8 volts is way faster than a brushed stock so maybe in 12th we stick with the 13.5 and the 3.7 volts and it will work itself out...
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Old 01-17-2008, 02:49 PM   #12
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For me, this isn't a 12th debate. We are already running BL. The issue with LiPo is weight. IF you change the weight distribution in a 12th scale, it will require new chassis' to get the cars to handle. For 12th, it isn't as simple as 'going LiPo' it then means we have to design new cars.

The other thing to consider is that batteries are only really an issue at the very top level. 12th is the drivers class, and any good driver will beat the average Joe (me!) with cells out of a power drill! I regularly get beaten by other drivers with 19T motors, when I am driving Mod, and they are using old cells.

12th is on the up, and the thought of changing everything in one go, in an uncontrolled way, fills me with dread. Let's start an Open class, where those that want to experiment can do so. Once a consensus is reached, let's propose a Rule change to our Associations. But please, spare 12th the nightmare that has been TC for the last two years - it didn't work for them allowing anyone to do anything, it hurt numbers of drivers, shops and manufacturers - we don't want to do that again, surely?
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Old 01-17-2008, 03:09 PM   #13
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The first thing that has to happen is more then a couple people need to try and have hard data. When "there was this guy that did and he said it kicks ass" stories, it feels like a urban legend kind of thing. If I had a 12th scale laying around, I would tinker with it. That is where this has to start. 12th scale racers tend, in my experience, to be very die hard and "passionate". Expect a lot of resistance and negative banter.
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Old 01-17-2008, 03:35 PM   #14
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12th scale drivers tend to be purists that like the way racing should be. This is why the evolution of 12th scale seems to most to be slow, only the best designs stick around for the long haul. Every few years a design that was tried comes back, people try it, and then it disappears again. Until a person that wants to affect change to 12th scale that comes along and truly understands the cars (I.E. what moving which components to where will effect everything within the whole scope of the car), the changing of the rules regarding these cars should be left to a consortium of the current industry leaders in the manufacturing of the chassis, and the industry experts that lead the way with power and electronics.

12th scale currently has a winning formula that the majority of people that race them don't mind (and possibly prefer) sticking to. People that don't know or understand the intricacies of the chassis' should not be affecting the rules changes for these cars. I started racing 12th scale in '91 and don't feel that I am the expert on chassis design. I am sure that there are others out there that want to affect change just because they feel that 12th scale shouldn't be 'left behind', that shouldn't be messing with it until they understand how the cars really work.

Does this sound like a lot of resistance? I am sure that I am not the only one that passionately feels this way. I am not against alternate power sources for 12th scale. I think that with such a seemingly simple formula that we have now, we shouldn't mess it up just because a few people that don't race the class want a particular technology to disappear from RC all together.
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Old 01-17-2008, 04:22 PM   #15
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No one here is calling for a change NOW. We are looking to the future to try and figure out a way 1/12th can continue as a class with the changes in battery technology. Most industries outside of RC are moving or have allready moved away from Nickel based batteries and with ROAR and Tamiya's acceptance of LiPo is only going to help RC move in that direction as well. Right now we can see what is happening in other classes and have an opportunity now to be looking at what to do with 1/12th in the future as Nickel batteries start to go away and be ready for that rather then caught off guard.
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