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Old 11-28-2006, 09:27 PM   #676
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Originally Posted by XrayFK
RCTech is running on 4 cells right now and does anyone like it?
That's what I thought.
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Old 11-28-2006, 09:30 PM   #677
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So, since the biggest part of this debate I've seen is about SPEED, how about 3 (4) cell classes and 2 (6) cell classes sanctioned to be allowed at "NATIONAL" and REGIONAL" Roar events. For LOCAL racing, as always, it's up to the individual LOCAL program to decide what's best for them.

4 Cell - STOCK
4 Cell - 19t
4 Cell - MOD
6 Cell - Expert 19
6 Cell - Expert Mod

You can NOT cover the field any better than that for speed issues. Require PRE-ENTRY For all major events. The classes w/ NO Pre-Entry by a cut-off date don't get run.

It should not have to be a EITHER/OR situation. If MY track has a 1200 ft HUGE road course track and it can handle 6 cell speeds, it should be able to run them. If YOUR track is only built inside a 20 x 40 box and you don't have a lot of room a 4 cell class may be GReAT. COMPROMISE~


I still say this idea covers MOST of the ground...and gives good options and learning abilities.
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Old 11-28-2006, 10:39 PM   #678
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Default Here we go!

I hope this post spurs some valuable discussion and not just inane flaming.

I want to make sure that you all understand that I appreciate feed back and I have an open mind. Prove me wrong with facts and I will be the first to say I was wrong

The following is a collection of my personal opinions that have been formed over the last couple of years from going to races ranging from club races to IFMAR Worlds, speaking to the most brilliant people in our industry, and hanging out and talking with the worlds best drivers.

Why 4 cell?

A lot of you have asked for a full explanation as to exactly what the problems are with 6 cell racing. I wanted to take a few minutes to cover this and why 4 cell is the best solution.

First of all it is very important to get into the proper mindset when thinking about this issue. Many of you are thinking very short term. You are thinking about 4 cell’s impact on today’s 27T and 19T motors. There are a lot of changes on the horizon. Brushless use will increase. They will be faster than the brushless motors they intend to replace and this will have an effect on racing at all levels.

Some of you are on some conspiracy trip about what the industry wants to accomplish with 4 cell racing. Its pretty simple…we want to insure the health of the sedan class. It’s a lot more important to us than to you that sedans stay popular. To you this is a way to relax on Sunday mornings. To us this is our livelihood. Our opinions are based on A LOT more information than you guys have access to. Remember, we make the stuff you buy. We are working on new cars, motors, speed controls, tires, bodies, etc….constantly. We are developing stuff that you may not see until 2 years from now. We have a 12-24 month head start on knowing where this is all going.

As far as some sort of ROAR, EFRA, BRCA, IFMAR conspiracy; decisions like this have been made by sanctioning bodies for years. This is nothing new. There was no national vote in 1991 when ROAR adopted a 24 deg limit on stock motors. I was racing then. Guys were really mad about that. No one wanted to go slower. From one day to another guys had to toss perfectly good motors but in the end it was a good decision and no one wished they were running 45deg Stock motors (they are actually slower than current 24 deg motors).

There was no vote to make 6 cell 1/12th cars go to 4 cells. Look at them now! There were more 1/12th entries at Cleveland than Sedan entries.

Seven years ago Oval went 4 cells. They was no vote on this change. The leadership of ROAR made the decision. You guys are nothing compared to the uproar that occurred at tracks all over the country when that happened. ROAR was dumbing down Oval racing, no one wanted to go slower, it was going to kill the Oval class. It didn’t happen.

Where did this 4 cell stuff start?

About 2 years ago I was talking to Mike Reedy. He was saying that the quality of racing at the top level Modified races was getting worse every year. The cars were getting faster and faster and as a result the races were getting messier. He had eliminated one ways at the Reedy Race the year before to make tight racing easier (braking with one ways is very hard) and it worked but the cars went even faster with spools than with one ways. He said he thought reducing the cell count was the way to go. It was simple, required no new technology or investment from racers and would slow the cars a bit to make racing tighter and more manageable. He has wanted to run 4 cells at every Reedy race for the last thee years but without support from ROAR and IFMAR he knew it would be a hard sell so he shelved the idea every year.

So what are the problems 6 cells?

With the increase in voltage and reduction in cell IR that has taken place over the last year we are getting to the point where the power systems in our cars have reached their limits. The following are the areas where we are having problems.

1. Open Mod motors are failing due to heat and, or centrifugal forces related to RPM. Motor wires can unsolder themselves from the end bells, the solder connecting the windings to the comm can fail and the epoxy holding the wires in place can soften and allow the windings to shift and unbalance the arm at best or allow a winding to fling out and get jammed between the arm and the magnets.

Our current modified motors are pulling an average of 45A in a 5 minute run. This means that with a 7.2v nominal battery pack. This means our motors are putting out ~324W of energy. This is calculated using Ohm’s law.

Ohm’s Law:

Voltage input x Amperage draw = Wattage output.

Since most mod motors today are about 55% efficient that means 178W go to moving the car and 146W are lost as heat. A soldering iron is 40W. A mod motor has to dissipate 3.5x the heat your soldering iron generates in order to keep running for 5 minutes. This is what you see fans and heat sinks all over the chassis of sedans today.

How can 4 cells help this issue?

On 4 cells motors will be geared up so over all they will still pull 45A. However, on 4.8 volt nominal battery packs the wattage output will be 216W. The motors will still be ~55% efficient so 119W will go towards moving the car forward and 97W had to be dissipated as heat. A 33% reduction in the heat dissipation requirement is huge and will make motors, magnets, brushes….everything last longer.

Some of the engineers out there will say we will draw more amps on 4 cells. While in the perfect world of theory this could be correct the inductance of our motors makes them incapable of drawing significantly higher amperages. Even if future brushless motors can draw 1000A from a 4 cell pack…so what! If you draw more than 45A for 5 min you will dump.

2. Brushless motors are shutting down due to heat and their rotors are fragmenting from high RPM.

These are issues were with the original bonded magnets. As of January 1, 2007 ROAR, the BRCA and EFRA have made sintered magnets legal. Motor thermal shutdowns will no longer be an issue and the new magnets can handle just about any rpm. Unfortunately, all of this will but more loads on the speed controls with I will discuss later.

3. BL motors will become the standard motors soon. The speeds of all cars will go up dramatically. Ever increasing speeds in all classes is making it harder for beginners to get started and ruining the quality of racing at the highest levels.

The convenience of BL motors will make them the standard power plants for electric r/c cars within the next 2 years. However, by their nature they will be faster than the Brushed motors that they replace. On 6 cells a 13.5 BL with a sintered rotor is as fast as or faster than a 19T motor. It looks like this will be the entry level motor. The next generation of racers will learn to drive running something like a 19T motor. How many novice guys do you know that are intimidated by the speed of current stock motors? Do you think they would be better off with a 19T?

A 6 cell stock Sedan on carpet with foam tires is not at all slow. Even on asphalt Stock sedans are by no means slow. Novice racers across the country are having trouble learning to drive at the speeds our entry level class is running at.

Did you guys know that only 5 cars were running at the end of the Mod A-Main at Cleveland? One of the A-Qualifiers only had THREE CARS FINISH! There were only 6 cars running at the end of the Mod A-Main at the IIC. These are the best racers in the world and they could not finish a race either due to motor trouble or crashes and mistake brought on by the absolutely ridiculous speeds they are racing at and they don’t like it. The cars are too fast to race heads up and dice for position. If a driver in front of you makes a mistake you have no time to do anything but drive right through him and half the time you break your own car. This is not my opinion. This is straight from the top drivers on earth, Jilles Groskamp, Teemu Lieno, Atushi Hara, Josh Cyrul, Hupo Honigl, and many more have told me the speeds are just stupid and racing is suffering from it.

How can 4 cells help this?

4 cells will slow the stock class down and return it to the novices where it belongs. Those who want the speed of stock can run 19T and go just as fast as or faster than they are running in 6 cell stock today. Those who want the speed of 19T can run Mod and go just as fast as or faster than they are running in 6 cells 19T today.

More importantly 4 cells will reduce the speed of the upcoming BL motors so the 13.5 BL class can function as a starter class like 27T is today. A 13.5 on 4 cells will be as fast as or faster than a 27T on 6 cells.

So there you have it!
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Old 11-28-2006, 11:14 PM   #679
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Quote:
Originally Posted by AdrianM
I On 6 cells a 13.5 BL with a sintered rotor is as fast as or faster than a 19T motor. It looks like this will be the entry level motor. The next generation of racers will learn to drive running something like a 19T motor.

A 13.5 on 4 cells will be as fast as or faster than a 27T on 6 cells.
I hope you have first hand experience on this because this is not the case with my findings at all. Matter of fact, the ss4300 from novak on 4 cells was a better comparison to a 27 turn stock motor on 6 cells. Tested it the other night. Didnt have the same outcome as you have stated. Not trying to be nitpicky,because I see your arguements and appreciate your opinion but..........
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Old 11-28-2006, 11:31 PM   #680
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Alot of good points. However I have to disagree on one. The 13.5 bl is not as fast as a 19t. I have tested the 13.5 with a sintered rotor and the times I ran were comparable with my co27's (within .2 seconds). Same batteries, same driver, same car.
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Old 11-28-2006, 11:34 PM   #681
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Yup, have seen them run, have a team driver testing for Novak right now and he has confirmed 13.5 with sinterd rotor on 6 cells is about the same speed as a 19T. Keep in mind you can gear WAY up once you use the sintered rotor and that the motor temp sensor can be disabled (blue wire) as the max temp for the sintered rotor is way higher than the max temp on the bonded rotor.

On 4 cells and geared way up is about the same speed as 27T stock.
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Old 11-28-2006, 11:36 PM   #682
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Then I must have some really fast co27's.
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Old 11-28-2006, 11:42 PM   #683
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Quote:
Originally Posted by trilerian
Then I must have some really fast co27's.
You are probably way undergeared in the sintered 13.5. I will find out the gear ratio our driver ran and let you know.
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Old 11-28-2006, 11:43 PM   #684
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12 teeth higher on 64p than my co27, motor comes off at 160f
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Old 11-28-2006, 11:49 PM   #685
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I run a SS4300 with a sintered rotor and LiPo on a weekly basis in a very competitive class (foam, carpet, on-road). Even with the sintered rotor, the cars aren't as fast as a 19T. The right rollout seems to be about 33MM with the sintered rotor, and 28.5-29 with the bonded. Going above 33MM doesn't generate more speed, just more heat with less punch out of the turns. Still, even with this setup, a decent 19T with NiMH will easily pull me on the straights, and the 4300 will outpunch them in the turns. It's close, but the advantage still belongs to a 19T.

I can't see how a 13.5 would have any chance of being faster than a 4300 (10.5).
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Old 11-28-2006, 11:51 PM   #686
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Well here is something I just thought about, get rid of foam tires on carpet. Would this slow down mod cars some? Lack of traction will dictate wind of motor.
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Old 11-28-2006, 11:54 PM   #687
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Quote:
Originally Posted by trilerian
12 teeth higher on 64p than my co27, motor comes off at 160f
You can still gear up. The motor can pull it and with the sintered rotor it safely to run up to 200 deg with no problems.
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Old 11-28-2006, 11:58 PM   #688
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Doesn't the speed control shut down when the motor temp hits 180
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Old 11-28-2006, 11:59 PM   #689
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But I will try it
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Old 11-28-2006, 11:59 PM   #690
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Quote:
Originally Posted by trilerian
Then I must have some really fast co27's.
They are ok

later
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