W.E.D.Jim

iTrader: (17)

The 12th scale racers are using 4 cells and are getting all their laps and no more radio problems then normal...I think?

One thing is for sure, some testing is in order, since speculation is useless, except for entertainment.



Side subject; I wouldn't blame the RS200 for spectator deaths in Rally, maybe standing next to the track is a factor? I wonder how many deaths there would be in US racing organizations if people could stand at the edge of the track during the races, regardless of the technology in the cars?

Kind of like saying meat grinders should be safer because people keep sticking their hands in them and having them mutalated due to their poor design.

LOL, Jim

WheelNut

iTrader: (5)

Also consider the future with technologies like this in your TC. http://forums.radiocontrolzone.com/s...d.php?t=222362

Faiz

IMO the concern is not to reduce speed instead simply how to avoid the overgrowth of battery progress overtaken esc+motor combo progress and simply killed them,

sorry, slightly off topic,
1. I believe rs200 is not underdeveloped, its overdeveloped like others group B.. if you remember those big upfront and rear spoiler of group B beast, that tell you how difficult getting traction with such power
2. the reason of group B banning is after several fatal accident related to other group B cars not only due to rs200 accident alone > 1st. rs200 in portugal that you mention, 2. toivoinen (Lancia S4), 3. attilio bettegea (lancia 037), those all fatal accident..

Jeff Brown

Actually, this was tested several years ago with Reedy. The debate was what it is today about cells and the speeds.

Mike Reedy had some Team Drivers test Touring Cars with 4 cells on foam tires. Even back then we were still running 7 or 8 turns with 6 cells, probably around 2002 or 2003. So some tested and dropped to 6 turns with 4 cell packs. They were about .3 to .5 tenths of a second slower a lap. Not a major drop. The motors finished better, the cars were easier to manage and drive for the race.

If you think that dropping from 6 cells to 4 cells decreases runtime you are mistaken. It is easier to make runtime with fewer cells which was the driving force of 12th scale switching to 4 cell only worldwide.

Jeff

Jeff Brown

Interesting. When I run a motor at 2 volts it pulls say 4 amps. Then I run the same motor at 5 volts and it pulls 12 amps. Please explain.

Jeff

ttso

iTrader: (1)

I don't have number but this is what I can tell you by seeing my friend's car.

Runtime, no problem for 5mins
Laptime, about 0.3~0.5sec slower per lap in 13sec track
Motor, 6x2T
Brush life, make it at least 2times longer if you compare with 6T in 6cells, maybe 3times longer
Temp: wayyyy cooler than 6cells
Batt: IB4200
RX batt is needed for safty, as I dont know if it's ok to run without RX batt
Car weight: 1340~1350g

I'm going to test 4cells 19T vs 6cells 23T once I have time, so I might able to give you more number. But like I said, you need to drive/see the car in person to understand 4cells touring.

tones

iTrader: (55)

a little more information...
equipment used was ko 302f, ko vfs-1 comp, ko 2413.
no rx pack was used.
amb personal didn't miss any laps in any of my runs.
dont recall experiencing any problems with the servo.

camera doesn't seem to like the close ups so cant post photos, but the brushes from the motor used for the 4 cell runs have only a very slight change in color towards the face of the brush. quite impressed with that after 8 or so runs on it without a rebuild, some of which in practice well exceeded 5 minutes.

plan to continue testing on different tracks as soon as possible.

2-Bad

iTrader: (24)

Jeff,
No explanation needed... you are right.... more Voltage to a motor = more RPM, more current, more temp, more brush burn....

eforer

Power (Watts) = Volts X Amps

to achieve the same power with less voltage:

Shebango! Amps go up.

I guess thats the argument for why more current is consumed with 4 cells. That said, if one uses the same motor in a comparison between 4 and 6 cell, less voltage will result in less power and less current.

Terry_S

iTrader: (3)

Yes but 1/12 are lighter cars and they race for 8 minutes, so there is less volt drop under hard acceleration and less load. Problems will show up more often with 4 cell TC especially with Mod motors. Some ESC's may have problems with 'power-fail' voltages (ie won't work well on 4 cells) and running without a RX batt means servos will operate slower. Also lap counting problems with PT's will happen more often. These are all things to consider, as ttso says it will be safer to run with a RX batt, without one you may have more trouble.

Terry_S

iTrader: (3)

Hi Ed, glad you're going well even in the 50C's heat!

Recycle

The motor that ttso’s friend used was special designed for 4cells running, not the typical 6T motor with 6cells on market.
So just as eforer said,
Power (Watts) = Volts X Amps
to achieve the same power with less voltage:
The 4cells motor we are using is draw more Amp. than a 6cells motor. Typical figure is 10-15Amp. @ 2V, 6Tx2.
The speed, may not fast but at least equal when compared to those 6cells modified touring with 8/9T motor in 8 mins racing.
The running time sure no problem for 5 mins, even 7+mins without Rx battery.
One thing I want to mention is: people using 6cells 6T or 7T 5mins compare to 4cell 6T even 5T, the speed of 6cells sure to WIN, it is no doubt.
BUT please be noted that in Japan or Hong Kong. We are talking about 4 cells modified compare to 6ells modified in 8mins racing; it is no doubt both of them are in same speed.

tonyv

iTrader: (1)

I am not an electronics expert, but I think you've got that backwards. Power is indeed a formula of the Volts times the Amp draw. But the Amp draw is defined by another formula, namely Volts = Amps x Resistance. If the volts go down and resistance stays the same then Amps go down too. The result is less power (volts x amps).

As someone argued when you remove two cells you remove some resistance and as can be seem from the formula, if volts stay the same and resistance is reduced the amps go up. This is actually already part of todays problems as the current crop of cells have half the resistance we had about three years ago...

Josh - Point well made. I think laptimes would be no more than 0.2s a lap slower if that on most tracks.

Oscar, that is the direction I am leaning towards too. We will need multiple changes to address the heat related issues. And then there are other problems such as the driveability aspect. Sure, it should become too easy, but it shouldn't become so hard that there are only 20 or 30 people in the world that can control the cars either. Combining a cell reduction with an increased race length will help with that too. However even then I think there also needs to be a discussion on the technologies that will be allowed such as for instance the types of magnet allowed. 4 cell + 6 mins is something I would be ok with but do you think that it will be enough to make a long term impression on these problems?

Switching to the driveability considerations for a second, one of the reasons it is more difficult now than in the past is the sheer torque we run with. This results in major abrupt weight transfers in the car when going on and off throttle. The top drivers are able to control that, but most of us have trouble with that. This is especially the case in today's point and shoot style of driving caused by the fact that we don't have any runtime problems anymore and therefore basically are running 5 minute sprint races.

Reducing the voltage will reduce the torque and increasing the race length will, as Josh pointed out, result in running less timing and softer springs when running brushed motors. All this reduces the torque and thus the torque effects.

Sanabria

Actually, eforer is correct. The ammount of current that the motor draws is a function of load, which is predicated by the cars weight and the final gear ratio. Current is load, which is what the motor demands to move the weight. This is something that some seem not to understand.
For example, lets say 100W are required to move X ammount of weight and you have a 10V source. (For simplicities sake, lets pretend that the motors efficiency is 100%) That motor will demand 10A. Lets now reduce the source to 5V. It still takes 100W to move the weight, so now the motor will demand 20A. When you factor in the efficiency (or lack of) of permanent magnet DC motors, it starts going down hill.

Smoking motor..

Yeah I know First off all the rs200 had a massive turbolag problem and a floppy chassis i know this from talking to guy that raced them in rally cross. This made them really hard to drive and the turbolag would catch you out that why 8 spectators bore the brunt off it the other cars went past the spectator no problem. The Lancia the went down the cliff killing the drivers let just say the the fuel the were using init wasn't 85 octane petrol it was a blend of avgas and some other combustant it was reffered to as rocket fuel and aluminium tank weren't exactly safe for storing it in, in the event of an accident compare to mordern kevlar fia approved tanks. There are a lot a thing about the cars run that unless you know people that have race and delveloped them since '86 you won't know about. Like the 6r4 4wd system was nowhere near developed to cope with 500 bhp of the 3.2 v6. A mate had to spend 30 grand on getting thing like that sorted out to race it. Shame he sold he said it scared the s*** out of him going down brands hatch straight it was doing 140 mph and had more to go and this is a rally car .