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Old 09-01-2005, 02:46 PM   #91
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Quote:
Originally Posted by andsetinn
Some people seem to think that longer mains make the motor run hotter. Lets do some calculations on heating motors. If you're using 3300 mAh batteries and barely make the main, the motor is using equalent of 285 Watthours in five minutes. It's using equalent of 180 Watthours in 8 minutes. The percentage of power that goes through the motor and is turned into heat is the same. Which is hotter, 300 watt heater (5 minutes) or 200 watt heater (8 minutes)? It seems obvious that the longer the main is, the cooler the motor runs. You just have to adjust the timing and gearing to last 8 minutes.
Good point. I'm starting to like the idea of 7 or 8 minute mains as long as its not outside under the sun in the middle of the summer.

It would be interesting to force the experienced class drivers come up with an actual race strategy (motor and driving), rather than just sprint the whole race.
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Old 09-01-2005, 03:24 PM   #92
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Having just experienced a race with 8minute qualifiers and mains, I'd like to say that it is indeed fun with 23T motors. If you crash, you can make up the time. You can also have awesome battles on track. However, it does feel like you are driving forever while on the stand and marshalling on a 160 degree surface with the sun blazing down for 8 minutes is no picnic. We ran 4 qualifiers and 3 mains with two sets of CS27's and two non-matched 3300 stick packs. With the exception of whipped tires, the equipment didn't take too much of a beating. That being said, I don't think I could do 8 minute races in mod. As it is now, I have a heard enough time not blinking for 5 minutes
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Old 09-01-2005, 06:22 PM   #93
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Quote:
Originally Posted by ChadCapece
It's not that simple
It isn't and yet it is.

It seems that almost everyone can accept longer mains and qualifyings. The main arguments against it are:
Meetings would most likely take longer unless number of racers was limited or some racers restricted to fewer classes.
Some people find it hard to concetrate for more than five minutes, especially in the summer.
Some people find it hard to turn marshal for more than five minutes, especially in the summer.
More time to crash your car and break something expensive.

Arguments with it:
More tracktime.
You can possibly make up for mistakes early in the race.
Some people like the challenge of longer races.
Motors and batteries would heat less and last longer (arguably).
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Old 09-01-2005, 07:31 PM   #94
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I guess this..... If we're not getting more voltage out of the newest batteries, then why bother buying the 3800's. Isn't it all about the runtime?
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Old 09-01-2005, 07:39 PM   #95
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Quote:
Originally Posted by John Warner
I guess this..... If we're not getting more voltage out of the newest batteries, then why bother buying the 3800's. Isn't it all about the runtime?
The batteries don't supply more voltage, it's just that as the capacity increases, you get closer and closer to the beginning of the discharge curve, which results in more voltage at that moment in time. With a 1500mAh pack, wouldn't you have less voltage in that pack than a 3300 at the same amount of discharge time? Yes. The same goes for 3300 vs. 3800.
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Old 09-01-2005, 08:58 PM   #96
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Cells are rated at 1.2v, but non have that average voltage over a discharge curve. They start out at over 1.2v per cell, then drop down and average the number on the label. Then drop below that and down to .9v per cell. I've been told that 3700s are like running and extra cell in a 3300 pack. As in, more powerful, and runs for longer. It might not make a big difference in the first minute, but 3700s should be able to spank any 3300 pack at the 2-5 minute mark.
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Old 09-01-2005, 09:59 PM   #97
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I would like to see ROAR or NORCCA rules develop in 2 directions. I think the current technology cars should, as has been suggested, run for longer "Enduro" length races. However, I think it would be best to start developing rules for new "sprint race" cars based on significantly smaller batteries. My reasons are:

1. Battery maintenance has become far too time consuming for "amateurs" (hobbiests).

For me to test and re-match, say, 5 packs of batteries (1 practice, 3 qualifiers and 1 main), 6 cells each would be bad enough with a CE Turbomatcher (which handles 4 cells each). But I do not even have one of those. Have you any idea how long it would take me using my 1 cell discharger? Consider working a day job and doing this in the evenings. Do you really think people could match that many cells? What could you realistically get done? 2 cells per night would be difficult. This gives too much advantage to people who would spend huge amounts of money.

2. Race prep is also getting out of hand. About 10 years ago when I first raced, our packs were 1200-1500 mAh range. I was able to run my chargers at work. I could actually pre-charge 5 packs during the day (it took about 1/2 hour a pack as I recall) without significant interference with my day. Then I'd take them to the race and re-peak them a couple of minutes before each run. The thing is that when you are working, *work* takes priority. So quite often I would not get to go back to the charger until some time after the charge was done. But since I only had to get about 2.5 hours of charging done, there was a lot of leeway. If I tried this now, I would really want to have 3 chargers going and start them all in the morning. A 2nd batch of charges could be done in the afternoon. It would work, but that's 3 chargers and either a huge power supply, or 2 or 3 power supplies. That's a lot more than what I needed before (not to mention the electrical bill).

3. With all that power, the modified now need fans. We are going to have to have rules about fans. Jim Hall added fans to his Chapparal Can-Am car years ago to suck his car down for more traction. That was banned. I have seen the fan arrangements of some of the pro cars and I think some guys have been working with that trick. So far, no-one is saying anything about it. But I think it is time to ban fans.

I think we need a new battery spec. I would like to see a slim battery, a bit thicker than a current "AA" battery, (because I find "AA" batteries hard to solder) but the same length as current Sub-C. Such batteries were made for laptop computers, so the battery makers would be willing to do this. Alternatively, we could have batteries the current thickness (22 - 23 mm) and the same length as the thickness. I would target about 1/2 the capacity of the current cells as being realistic. So current technology would bring the cells down to about 2000 mAh.

As for the "sprint" car spec. I would similarly reduce the minimum weight by the amount that would represent the difference between the current sub-C packs and the new packs (using 6 cell packs for a baseline).

All this would make new technology chassis possible, allowing for further development.

I would also suggest reducing the motor size for 1/12 scale cars, particularly to free up car designs for further development, but that is another issue.
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Old 09-02-2005, 03:11 AM   #98
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MobileIT. The small battery suggestion is interesting. Run for 5 minutes with smaller batteries and maybe smaller motors. 1200-1300 gram weight limit could be realistic for class like that. And some of the 1/18 brushless motors are very powerful. Then you can run for 8-10 minutes using 3800 batteries. The only minus is that in my opinion we already have too many classes. But it could be lots of fun, and that's what this sport is about, having fun.

We already have 2 versions of smaller batteries. First we have the 1200 mAh used in 1/18 cars. Second we have numerous verions of LiPoly.
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Old 09-02-2005, 08:57 AM   #99
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http://fantasyworldracing.home.att.net/

at this track we have been running 6 minute stock and 19t for two years, we started out with 7 minutes but dropped back to 6, (run time issues for to many) as you can see by the lap times of stock and 19t the motors do not fade with the extra 1 of run time. and like this thread, most like it the extra run time, a few don't. the extra minute of run time will get boring if your just out there driving by your self, but if in a battle it is a blast. and sometimes after losing that battle you wish it would have been a 5 minute race

at our off road track, we have done serveral 10 hour (thats not a typo) enduros with stock trucks. if the correct brushes are used, and you drop a gear or two, the motor will last just fine, i've seen some comms after a enduro that looked like a normal comm after 4-5 races and i have also seen some that were, well, you couldn't cut deep enough to clean them up.

hope the link worked, if not, on the left side click on current season, then race schedule, then scroll the center part of the page until you get to one of the races and click on it, it will give you the print out for that race. btw if you have time, click on the pictures and check out our drivers stand/storage shed/race directors booth.
i just went and doubled checked, the stand is actually on the home, upper left hand corner as well as hidden with the race pictures.

Last edited by Turtlemaster; 09-02-2005 at 09:08 AM.
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Old 09-02-2005, 04:29 PM   #100
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Going OT a bit, but.......

MobileIT, batteries as you describe exist. GP makes a short sub C with 2200 mah, and an A with 2000 mah capacity. A 2200 pack would be nearly 4 ounces lighter than a 3700/3800 pack. The 2000 mah cells are even lighter. Both cells have a great reputation with the electric competition airplane crowd.

I have been toying with getting a 2200 pack to play with, as it would have plenty of run time for off road (which is all I do at the moment). But, since it is common practice to add weight to the cars, it probably wouldn't be much of an advantage, might handle worse. But for on-road, it might work well.....I know 2 ounces makes a dramatic difference on an on-road oval car.

But it might not be such a good idea for 6 minute or longer races....
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Old 09-02-2005, 04:54 PM   #101
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I have used the GP2200s and they are great! But they are not legal in most forms of RC racing. You'd probably get 8 minutes with offroad brushless.

I've also used the full size "A" 2500 mAh cells. It seemed they could not quite keep up with the amp draw (1/10), but in a lighter car they might work.

Also, keep in mind that cars designed with batteries along the side are not going to balance properly.

I've been bitched at for using smaller cells at a club race! Jeez.
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Old 09-07-2005, 10:46 PM   #102
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Quote:
Originally Posted by andsetinn
MobileIT. The small battery suggestion is interesting. Run for 5 minutes with smaller batteries and maybe smaller motors. 1200-1300 gram weight limit could be realistic for class like that. And some of the 1/18 brushless motors are very powerful. Then you can run for 8-10 minutes using 3800 batteries. The only minus is that in my opinion we already have too many classes. But it could be lots of fun, and that's what this sport is about, having fun.

We already have 2 versions of smaller batteries. First we have the 1200 mAh used in 1/18 cars. Second we have numerous verions of LiPoly.
I do not like the 1/18th packs because the cell diameter is "AA". I find these, and "AAA" very hard to solder. That can be dangerous. An accidental "bridge" will short it, and you might not even notice until it vents.

I do not like LiPoly either right now. We are just starting to get a real handle on how dangerous they might be. Have you been tracking the rumours about exploding Cell Phone batteries? The problem with the reports is that we do not have accurate numbers of how often it is happening. I do not know who has reliable figures. Also, since the technology is changing, any current numbers are already "outdated." It is just all too new, and the only thing we know for certain is that there really is a problem.

Consider this: Think about all the people you have met at your local track. I expect you will know some who are level headed, careful and very knowledgeable. You probably know some who simple not very knowledgeable. You might also know some who are knowledgeable, but not careful (people who know that you are not supposed to put acid in water, but do it anyway). And then you might know some generally careful and knowledgeable, but are simply crazy. They really *do* want to blow something up. They all exist to some extent. Now, keep in mind that LiPoly is *very* complicated and touchy technology. It is sort of like gunpowered. And what is it like when you are in a mad rush to rebuild your car before 3rd round qualifying? Now, you are going to have LiPoly batteries being charged in that situation by these guys? Not a good idea.

As for "too many classes", well, I can agree with that, but I think that this will be a slow transition. I expect that in the end, we would end up with mainly "sprint" races, and occasionally some people might try an "enduro". Also, the Pro races might turn into "enduro" class races instead of "3 Mains" races.

I do not think the "sport" can survive in the current situation. As I said, the cost and effort of maintaining batteries is already prohibitive.

Can someone post the charge time requrired for a pack of 3700 mAh, and a pack of 3800 mAh batteries?

Also, what are the discharge times?

Also what were the times for the 2000 and 2200 mAh batteries that have been mentioned?
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Old 09-08-2005, 12:03 AM   #103
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I agree with MobileIT some people just want to blow something up. And as for smaller and lighter cars isn't that what 12th scale is.

P.S you do add acid to water do it the other way round and you're in trouble
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Old 09-08-2005, 03:21 AM   #104
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MobileIT, I think you're too pessimistic. I expect you're pleasantly surprised at every evening to have survived through the day with all limbs intact . I've carried GSM cellphone now constantly for over 10 years, as have most of my friends. None of us personally knows anyone whose cellphone has exploded, none of us knows anyone who personally knows anyone whose cellphone has exploded. I'm thinking it's kind of like the Mark Twain death story ("this report on my death was an exaggeration"), only very few explosions, maybe even just the possibility of explosion. On the other hand, I personally know two people whose disposable lighters exploded.
For the soldering and size issue. That's your problem. I have no difficulties in soldering AAA cells. I expect you wouldn't either if you practiced a bit.
For the cost issue the solution might be more rules. There is already a rule that limits how much motors are allowed to cost. If there were similar rules that limited cost of batteries and ESCs then the cost of racing would most likely decrease. But knowing people I expect those who have money to spend, to spend it on other go faster gadgets.

I think that longer mains would help the sport a lot, letting the drivers face the challenge of longer mains would put the emphasis on driving skills, not equipment and luck. It takes lot of skills to finish longer race with the car intact and still have some charge left in the batteries.

Last edited by andsetinn; 09-08-2005 at 04:06 AM.
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Old 09-08-2005, 08:59 AM   #105
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Quote:
Originally Posted by Superkarter
I agree with MobileIT some people just want to blow something up. And as for smaller and lighter cars isn't that what 12th scale is.

P.S you do add acid to water do it the other way round and you're in trouble
I would like to see even lighter 1/12th. Right now, the motors are so big that you cannot advance the designs. There is no real development anymore. The good thing is that this stagnation does keep it cheap. Last year's car is certainly going to be competitive next year and maybe even the year after (that is a 3 year lifespan). You will probably replace parts, but you will certainly not have to replace a whole car.

Re: Acid in water.

"What wazzat? I can't hear you?"
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