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Old 11-29-2006, 02:53 AM
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Again what this boils down to is the technology has advantanced to the point again where the 1/10th mod pan cars were before the dissappeared.If the new racers can't handle the speed you won't have any new racers coming to the tracks.How long do you think thefre are going to play with the cars on there street?Brushless motors are here and the brushed are going bye-bye. Reducing the cells and making the cars more drivable helps the overall picture.
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Old 11-29-2006, 05:11 AM
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Why doesn't the ExComm lift some of the restrictions that are holding brushed motors back, to help them also improve their efficiency and durability...similar to how they are spoon-feeding brushless? This would at least give the brushed manufacturers an opportunity to adapt to this changing landscape and racers an alternative to replacing their high end electronics and support equipment with BL...
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Old 11-29-2006, 05:41 AM
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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!

Unfortunately you don't realize the problem the 4-cell creates. Post lost is expressed in term of current squared times resistance. Resistance is in the batteries, ESC's, wires, and motors. The power out of the motors is as stated above VxI=P. So... you reduce the voltage to 2/3 of its original value so current must jump by 3/2 to keep the same output power. Since power lost (i.e. heat) goes as current squared, the losses are now 9/4 of what they used to be. This means more heat in the batteries, ESC's, and yes even the motors. This is helped a tiny bit by 1 or two fewer turns in the motor, but that is only a 10% effect at most. The batteries don't change resistance and will infact get higher resistance as they get hotter. The cars will be slightly lighter, but this will also not help as much as the power lost will hurt. This is true since F=m*a Force is mass times acceleration. to keep the same acceleration the force over mass equation must remain constant. a reduction of two cells is about 5.3 ounces on a 52 ounce car. This translates to a car that is 90% of its original mass with 2/3 (67%) of its original voltage. So in theory you need 90% of the 6 cell power. .9/.6667 = 135% or the original current. Square that to get power lost and you get 182% of the orignal 6cell losses. So you see even the weight reduction argument doesn't work.

By the way did anyone watch that Japanese race? It was pathetic. maybe 19 turn speed and dumped before the end. Do we really want that kind of junk?
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Old 11-29-2006, 05:59 AM
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Adrian, you keep bringing up the failure to finish by some racers at the US Indoor Champs.

Having been there to watch the race in person, I can attest (and others can confirm) that the track layout and boards were unforgiving with exposed corners, sharp edges and gaps that could turn what should be a harmless touch into a race-ending break.

This was not only in the high speed areas of the track, but also on the left-hand side (from driver's perspective) which was the 'more technical' area of the layout and happened in ALL classes, not just mod touring.

(Breakage happened in the LOW SPEED areas too)
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Old 11-29-2006, 06:07 AM
  #710  
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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.)
its 4wd, all 4wd classes on and off-road that i can remember are the same. but then there's still 2wd for us gentlemen we are still... civilised. lol
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Old 11-29-2006, 06:20 AM
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IMO 4 cell is stupid. AT first, when the higher voltage, lower IR batteries came around. We had our heat issues. OUr motors were running 250-270 degree's in temp, which was really bad. Since then, I have done alot of testing and now we have no heat issue. I can run a 7x1 in a touring car and the motor wont reach 200 degree's. Our brushes no longer burn up, our motors no longer slow down, and we have no more failures. As batteries get better, I will make the changes needed to make the motors run. 4 cell is not the anwser.
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Old 11-29-2006, 06:29 AM
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Originally Posted by Bob-Stormer
Not a valid argument. Why would the average club racer come to a site that has no affiliation with ROAR to read up on ROAR decisions? How would they even know to do that in the first place?

I'm here a LOT, and I didn't even notice Eddie-o's thing until after the election.

Had ballots been collected at the track, WHERE THE RACERS ARE, would have been a good start and would have changed things considerably. To late to change that now though. Although I think for a fair check of the system, perhaps there should be a box you could check that says, "I have no idea who these people are", and did not pick one.

Different debate for a different thread.
I agreee this is a different debate for a different thread.
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Old 11-29-2006, 06:59 AM
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QUOTE - kufman: Unfortunately you don't realize the problem the 4-cell creates. Post lost is expressed in term of current squared times resistance. Resistance is in the batteries, ESC's, wires, and motors. The power out of the motors is as stated above VxI=P. So... you reduce the voltage to 2/3 of its original value so current must jump by 3/2 to keep the same output power.

I understand what you are saing. I dealt with this in my post. The power output will never be the same. The motors we run today are incapable of pulling the ~75A average 4 cells required to acheive the same wattage output we have today on 6 cells. We talked about this a year ago in the old thead. I have confirmed this with 3 diffrent DC motor engineers that work for 3 diffrent motors companies.

If in the future motors are developed that can draw this current you still have to make run time. A motor than can pull 75A is useless if the most you can pull out of a battery and make tun time is ~45A. You would need a 8100mah battery to make 5 minutes at 75A. I dont' see that being released any time soon.


Since power lost (i.e. heat) goes as current squared, the losses are now 9/4 of what they used to be. This means more heat in the batteries, ESC's, and yes even the motors. This is helped a tiny bit by 1 or two fewer turns in the motor, but that is only a 10% effect at most. The batteries don't change resistance and will infact get higher resistance as they get hotter.

Since in testing we are pulling the same amps on 4 cells as on 6 cells. The batteries will run no hotter. This has been proven in testing.

The cars will be slightly lighter, but this will also not help as much as the power lost will hurt. This is true since F=m*a Force is mass times acceleration. to keep the same acceleration the force over mass equation must remain constant. a reduction of two cells is about 5.3 ounces on a 52 ounce car. This translates to a car that is 90% of its original mass with 2/3 (67%) of its original voltage. So in theory you need 90% of the 6 cell power. .9/.6667 = 135% or the original current. Square that to get power lost and you get 182% of the orignal 6cell losses. So you see even the weight reduction argument doesn't work.

Once again you math skill and grasp of theory is impeccable. Accelleration is the main thing effected by a reduction in voltage. You have no argumet from me there. However, I have alredy dealt with the fact that the current will not go up on 4 cells

By the way did anyone watch that Japanese race? It was pathetic. maybe 19 turn speed and dumped before the end. Do we really want that kind of junk?

[b]Unfortunatly you were not that and you do not understand how big Yatabe Arena is. Even the 6 cell cars look slow there. I talked to guys that were there. The cars were not at all slow. The only place where you could feel a difference as a driver was a reduction in punch in the infield. On the straight the cars topped out at pretty much the same speed as the 6 cell cars. The lap time diffrence between the JRMCA ants and the last club race where the same guys ran 6 cells was on 1-2/10th.
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Old 11-29-2006, 07:05 AM
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Originally Posted by ottoman
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
You are think in the present...not the future. Look ahead a little. Guys are going to change motor anyways. Brushed motors are going to die out and be replaced by BL. BL will be faster than the current BR motors. Our entry level classes will be too fast to allow new racers to have a sucessful start and the calss will slowly die.

4 cell is an investment in the future. Your argment is based entirely on the fear of change.

In the short term the 27t guys that want more speed can run 19t. The 19t guys can run mod.

In the long term they are all going to change motors to BL eventually and 4 cell will help regulate the speeds in the entry level classes.
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Old 11-29-2006, 07:14 AM
  #715  
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Adrian, my biggest worry is by making TC 4 cells you are going to draw a much bigger line between it and other forms of RC cars. Every other 10th scale RC vehicle (leave pan cars out) is 6 cells.
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Old 11-29-2006, 07:28 AM
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Adrian,
Since some of your guys and some others did testing on 4 cells down there, maybe you can answer this. How much weight needed to be re-distributed on the chassis to get the car back to a balance? Speedo relocated to the right? Speedo and receiver? I know the other organizations are looking at 1350 gram minimum weight...is that realistic?
I know no one (including myself) wants to have to start thinking of buying a new car designed for 4 cell touring. Which is why I'm asking.
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Old 11-29-2006, 07:31 AM
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Originally Posted by AdrianM
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.
So based on this, sounds like the EXCOM will be making this decision without a membership vote. So is this currently beeing voted on by the EXCOM or just beeing talked about? If it is beeing voted on, when is this going to become effective? i.e. will it be effective 01/2007 and be applicable to all the 2007 events, is it sometime later in 2007 is it for 2008?
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Old 11-29-2006, 07:33 AM
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If 6 cell 19turn isn't too fast and 6 cell mod is, and 4 cell mod is about the same speed as 6 cell 19 turn, why not just drop mod? or leave it to the factory sponsored drivers who get their equipment for free? Seems to me the argument that this is a change for the top 20 guys in the country yet effects all of us is pretty valid.
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Old 11-29-2006, 07:39 AM
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Originally Posted by vtl1180ny
Adrian, my biggest worry is by making TC 4 cells you are going to draw a much bigger line between it and other forms of RC cars. Every other 10th scale RC vehicle (leave pan cars out) is 6 cells.
I hear you.

Off road is the real problem. 90% of off road track have zero traction compared on road. As a result they are not having the same issues we are. Only 4WD Mod buggies on blue groove tracks are running into motor and speedo trouble. In 2wd Mod Buggy and Truck many drivers are running 5 cells on their own because it faster and easier to drive.

As far as RTR. The companies I have talked to have no problems with 4 cell. They say all they need to do is spec a lower wind motor. From a maintanance point of view 4 cell RTR is way better because brush and comm wear is drastically reduced. Production costs for the companies that include packs with the RTR kits are also lower.
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Old 11-29-2006, 07:43 AM
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I have been following this and have a simple question. If we change to 4 cell and everyone has to change brushes, batteries, wieght distribution for setups and such why not just change the motor?

Why cant a stock motor be redefined with more turns or timing changes to slow them back down?

I would think changing a motor is not a super hard thing. Most people who are hard core racers will replace them every so often anyway. If you changed the motor then it gives progression for people to move up without changing to 6 cell.
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