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Old 11-29-2006, 12:00 AM   #691
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not sure how this got to be a Brushless topic, but they ARE all related.

I've been arguing w/ a few guys about the fact that a 13.5 and a 4300 B/L motor shouldn't be too far apart speed wise once you learn either one.

NoVAK rates the 13.5 at 165 Watts and the 4300 at 175 Watts.

The 4300 is rated at 4300 RPM unloaded x (1.23x6) = 31700 rpm (6 cell unloaded)
The 13.5 is rated at 3300 RPM unloaded x (1.23x6) = 24300 rpm (6 cell unloaded)

The 13.5 would require nearly a 23-24% increase in gearing to run close speeds, but should have enough power to be really close.

What's the average WATT output from a Komodo Dragon 19t good Stock motor?
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Old 11-29-2006, 12:01 AM   #692
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What up Dayton, why you gettin rid of you t2007
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Old 11-29-2006, 12:05 AM   #693
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Quote:
Originally Posted by AdrianM
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.
i really cracks me up when people say that dropping the voltage will reduce run time by increasing current draw of the motor. think back to when we ran 7 cells... run time was less than with 6 cells. that's because motors draw more current at higher voltage, less current at lower voltage. ohms law would only apply if the motor generates the same power at 4.8v as it would at 7.2v, which it wont. if it did, the whole 4cell vs. 6cell debate would be a moot point because the cars would be equally as powerful, with 4 cell weighing less.

if you don't believe me, try it with your motor break-in machine / turbo 30 / dyno sometime.
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Old 11-29-2006, 12:07 AM   #694
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Quote:
Originally Posted by AdrianM
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!
Thanks for your input. Very insightful from an industry insider.
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Old 11-29-2006, 12:17 AM   #695
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I'd be curious to compare the wattage/RPM numbers on the BL motors with all of them running the sintered rotor. It changes the power band quite a bit. I wonder if the increase in performance is consistent between motors, or if the more powerful motors have more to gain from the sintered rotor. Sorry, this isn't exactly the right thread for this, but it's a discussion I find very interesting. Feel free to stop by our 4300 racing thread to chat about it more. Bob Novak stopped by last week and provided some excellent technical information about the sintered rotor.
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Old 11-29-2006, 12:27 AM   #696
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Quote:
Originally Posted by trilerian
Doesn't the speed control shut down when the motor temp hits 180
Disable the motor temp sensor by pulling the blue wire from the sensor plug that goes into the speedo. 180 was the limit for the bonded rotor. The sintered rotor is safe to use at temps beyond waht the motor is capable of generating.
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Old 11-29-2006, 12:30 AM   #697
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[QUOTE=AdrianM]
So what are the problems 6 cells?

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.
QUOTE]

Thanks Adrian for the insite and bit of reality concerning the topic. Makes sense when presented with numbers and facts!
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Old 11-29-2006, 12:50 AM   #698
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regardless of the parts used to "slow down" things a touch. I think we need to keep in mind there needs to be a good seperation of the classes. When lap times are so close that it's hard to tell what class you watched, as in Cleveland where 26 laps would be stock, 27 would be 19t and 28 woud be mod. 1 lap seperation per class is to close. If in the end, we would have race results that were spread by 2-3 laps per class (at the best races with the best racers), you'd see complete different people winning and racing would be tighter in each class.

People don't have the commitment of time to put into mod, and I talked to several pro drivers this week that feel they are just "hanging on", not really driving. Which means us weekend warriors are going to have a tougher go of it, and this takes away close racing at the club level. And it's obvious that stock is to fast for the noobs.
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Old 11-29-2006, 12:50 AM   #699
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Mind you, I also talked to a pro driver that said, yea, that's true, the cars are VERY hard to drive fast. But what ever happened to finesse and driving talent and setup talent to get your car around the track? Setting up your car better so it would turn in on it's own instead of loading in wads of drag brake (which would reduce heat). Using your finger to conserve the tires. Using your head and your talent to make run time and not "use up" the tires, and not get the motor hot. "Everybody today just hammers the throttle". Very few real drivers left. (don't kill the messenger, that's what i was told.)
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Old 11-29-2006, 12:55 AM   #700
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I'm wondering if Adrian is aware of certain team drivers that have a knack for burning up and wearing out parts, and some that don't. As an example of people that hammer it, and those that finesse it.
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Old 11-29-2006, 01:02 AM   #701
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I was thinking about what Adrian said about Reedy. Reedy once told me he felt pan car died because it got so insane fast (even back then, IMAGINE NOW) that only 5-6 people in the world were capable of driving them to there potential.

Maybe that's kind of where we are now. Only a rare handful of people can really drive them to their potential. Granted, I will still stand by my statement that I'm glad we finally have all the horsepower 99% of us will EVER be able to use. But is that good or bad for the sport? I suspect that is what is up for debate here.

Reedy also mentioned some race where the corner marshals had to stand behind a metal grate of some kind to protect themselves from flying pan cars at ridculous speeds. I wonder if anybody remembers what race that was?
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Old 11-29-2006, 01:04 AM   #702
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Quote:
Originally Posted by Bob-Stormer
Mind you, I also talked to a pro driver that said, yea, that's true, the cars are VERY hard to drive fast. But what ever happened to finesse and driving talent and setup talent to get your car around the track? Setting up your car better so it would turn in on it's own instead of loading in wads of drag brake (which would reduce heat). Using your finger to conserve the tires. Using your head and your talent to make run time and not "use up" the tires, and not get the motor hot. "Everybody today just hammers the throttle". Very few real drivers left. (don't kill the messenger, that's what i was told.)
This is why I like 12th scale. Throttle heads give up quick when they can't get the car to run well. Gotta learn to squeeze it.... But sorta' to go back on topic the response of 4CM has been favorable at my track by those that tried it. Bottom line tires last, less weight=better cornering, less squirming around and the top-end speed is very, very close. And, oh yeah nice to share packs if you run 12th.
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Old 11-29-2006, 01:09 AM   #703
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Quote:
Originally Posted by nf_ekt
Bottom line tires last, less weight=better cornering, less squirming around and the top-end speed is very, very close.
That sounds whole lot like LiPo with a slower brushless motor, except without the NiMH curse.
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Old 11-29-2006, 01:20 AM   #704
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Ok fine... how about this...

Since you want 4 cells... and 4 cell mod is about as fast a 6 cell 19turn. This means the mod guys would be happy to run at this reduced speed. Cars wouldn't be too fast to drive and wont burn ESC and motors... well so you say.

SO
Why don't we just eliminate the mod class and keep 6 cell for everyone?

Make 19t 6 cell the premiere class? (remember it will be about as fast as 4 cell mod anyway)

No other classes will be affected... the most popular class (stock) wont have to change.

And

To make a (slower) class for the newbies make a silver can Johnson/Mabuchi motor rule. This is slower than a stock motor.... needs only minimum maintanace... no lathes etc and is cheap.

Of course this would never happen... but is it any dumber than making everyone change for the sake of a few

Last edited by ottoman; 11-29-2006 at 01:39 AM.
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Old 11-29-2006, 01:24 AM   #705
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Quote:
Originally Posted by syndr0me
That sounds whole lot like LiPo with a slower brushless motor, except without the NiMH curse.
Yeah, true. Nimh are important to this industry so don't expect them to go anywhere. At least they are priced right nowadays. I walked into a HS not too long ago (one that caters to planes,ect, way out of the loop on electric racing) and they had near-ancient 3000 packs that were priced at almost 85 bucks. You can get them for far better deals now, and with better than 1.14 volts (which ofcourse, helps lead us into this conversation concerning voltage increases and cell reduction as a result )
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