R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 08-26-2005, 08:25 AM   #31
Tech Regular
 
Join Date: Aug 2005
Posts: 308
Trader Rating: 1 (100%+)
Default

Quote:
Even 30 seconds into a run, a 3300 is going to have MUCH higher voltage than a 1900 or 2000 or 2400 for that matter. I have done extensive testing on this. Its a fact.

More voltage = faster car.
In my experience that is true, but the diference between rc2000 and GP3300 isnt as big as between RC2000 and 1900 sportpacks.

Besides, RC2000 seem more reliable then nimh cells. I have 5 year old nicads that still work fine. Nimh cells seem to loose punch even when u dont use them.

I donno what kind of testing you have done, but may i sugest you post them here? Im sure it will make the post much more interesting
Itchy is offline   Reply With Quote
Old 08-26-2005, 12:59 PM   #32
Tech Elite
 
PitCrew's Avatar
 
Join Date: Sep 2003
Location: Seattle Indoor Raceway
Posts: 2,129
Default

I soldered leads to the packs, charged them, and repeatedly touched the leads to my toung, after eating sunflower seeds. The 1900 lost its "Punch" very soon off. But the 3300 maintained it punch MUCH MUCH longer.
PitCrew is offline   Reply With Quote
Old 08-26-2005, 01:11 PM   #33
Company Representative
 
Danny/SMC's Avatar
 
Join Date: Oct 2001
Location: Elkton, VA
Posts: 3,097
Trader Rating: 2 (100%+)
Default

A very good RC2400 has a 1.13 average voltage per cell. A mid grade IB3800 has 1.18 at 30 amps. The lower IR of the NiMh cells will mean under load the difference will be even more. To have your motor run a .30 volts more for the entire discharge curve will make a difference.
Danny/SMC is offline   Reply With Quote
Old 08-26-2005, 02:39 PM   #34
Tech Master
 
Soviet's Avatar
 
Join Date: May 2004
Location: Littleton, CO - USA
Posts: 1,708
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by Hawk6
I'm not trying to be a smart a$$, just trying to learn. What is the performance gain?

I don't have hard data, so I'm just going to make up some facts here for discussion. Again, I'm talking a Tamiya with a silver can motor.

If I run a 1900 mAh battery for a 5 minute race, I'll use 80% of the power in the pack.

If I run a 3800 mAh battery for 5 minutes, I'll use about 40% of the power in the pack. What do I gain from carrying that extra power around?

Is it that the last minute will be just as strong as the first, or will the first minute of a 3800 be faster than the first minute of a 1900?

Thanks again.

Dude...

There is little to no difference in weight betwen a 3300 and a 2400 and lower. The sheer amount of capacity that you gain would allow you to gear the motor MUCH more aggressively than you would with a lower capacity battery.

Use better batts and gear higher...thats what we've been doing in this hobby for years now.

Shoot...arguing that the weight gain may not be worth it would be like saying that a V6 in a car is the same as a V8 because the V8s additional weight nullifies it's power gain...which it obviously doesn't.
__________________
"You don't get hurt racing little cars..."

-Me
Soviet is offline   Reply With Quote
Old 08-26-2005, 03:48 PM   #35
Tech Champion
 
Jon Kerr's Avatar
 
Join Date: Jul 2002
Location: San Diego
Posts: 9,658
Trader Rating: 17 (100%+)
Default

Quote:
Originally Posted by imjonah
"GP3700s, for instance, are still the choice of most pro racers"

1. "pro racers", In what major events are they legal?
They're legal in pretty much all the biggest events (none of which are ROAR events therefor ROAR not making them legal doesn't mean much.) Reedy allowed them in the Invite class, which is where most of the "pros" are racing, The IIC in Vegas is allowing them, I'm sure they'll be legal for the Snowbirds, Cleveland, The Novak Race at Trackside, etc... Even though not one of these is a sanctioned event, they are the biggies here in the US.
Jon Kerr is offline   Reply With Quote
Old 09-01-2005, 11:34 AM   #36
Tech Master
 
Hawk6's Avatar
 
Join Date: Nov 2004
Location: Freeport, IL
Posts: 1,549
Trader Rating: 50 (100%+)
Default

Just read this on the Tamiya website. The winner of the GT-2 class disclosed his speed "secret" was using lighter batteries. So, maybe I was on the right track after all

Here's a portion of the article from tamiyausa.com:

"...but it would not be enough as Houda had an edge in motor and a slight edge in corner speed. Houda would take the win as he later disclosed his secret in agility. Houda as it turned out used older Panasonic NHMH 3000 batteries that by today’s standards are a very light cell compared to the more favored GP 3700’s. It seems that most drivers opted to buy high voltage 3700’s, but Houda’s gamble in having a light car paid off. Since the Johnson motor can only pull so much the extra voltage would not be enough as we clearly saw".

This is dealing specifically with silver can motors, so it may not apply to all situations, but for users of the can motors, this is something to think about.
Hawk6 is offline   Reply With Quote
Old 09-01-2005, 11:43 AM   #37
Tech Champion
 
Jon Kerr's Avatar
 
Join Date: Jul 2002
Location: San Diego
Posts: 9,658
Trader Rating: 17 (100%+)
Default

Do they not have a minimum weight limit for this class?
Jon Kerr is offline   Reply With Quote
Old 09-01-2005, 04:28 PM   #38
Tech Master
 
Hawk6's Avatar
 
Join Date: Nov 2004
Location: Freeport, IL
Posts: 1,549
Trader Rating: 50 (100%+)
Default

The Tamiya Championship Series has all sorts of rules and classes - see their website if you are interested. For this particular class they define which Tamiya chassis' are allowable, and which hop-ups are allowable, and forbid lightening the chassis (by drilling holes in the chassis, etc.). But, as far as I know, there is not a minimum weight rule.
Hawk6 is offline   Reply With Quote
Old 09-02-2005, 07:45 AM   #39
Tech Regular
 
Join Date: Aug 2005
Posts: 272
Default

Quote:
Originally Posted by Jon Kerr
Do they not have a minimum weight limit for this class?

mini tcs rules is 1300GRAMS... mine comes in at 1380... with body and transponder.

i measured a 1800mah and a 3300mah battery and it is about 100grams difference....
noobie is offline   Reply With Quote
Old 09-02-2005, 07:47 AM   #40
Tech Regular
 
Join Date: Aug 2005
Posts: 272
Default

Quote:
Originally Posted by Hawk6
Just read this on the Tamiya website. The winner of the GT-2 class disclosed his speed "secret" was using lighter batteries. So, maybe I was on the right track after all

Here's a portion of the article from tamiyausa.com:

"...but it would not be enough as Houda had an edge in motor and a slight edge in corner speed. Houda would take the win as he later disclosed his secret in agility. Houda as it turned out used older Panasonic NHMH 3000 batteries that by today’s standards are a very light cell compared to the more favored GP 3700’s. It seems that most drivers opted to buy high voltage 3700’s, but Houda’s gamble in having a light car paid off. Since the Johnson motor can only pull so much the extra voltage would not be enough as we clearly saw".

This is dealing specifically with silver can motors, so it may not apply to all situations, but for users of the can motors, this is something to think about.

very interesting... but a 540 sports motor may be able to use that extra from a 3300?!? need some testing...
noobie is offline   Reply With Quote
Old 09-02-2005, 08:33 AM   #41
Tech Regular
 
Paladin's Avatar
 
Join Date: Mar 2005
Location: Australia
Posts: 275
Default

Quote:
Originally Posted by Hawk6
Thanks Itchy. I'm in this hobby with my 10 year old son - we each have our own cars. We're having a great time, I'm just trying to keep an eye on expenses since they are basically doubled. For a race day I need 8 battery packs, not just four.

Thanks.
Expenses, nargh they are the same as a budget, they just make this wooosshing noise as they go flying past.

I feel for you, I have 3 lads and myself racing, now they are all talking about getting another car each!

I am with you, LOVE this sport!
Paladin is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Change gearing when using higher powered batteries? Keith_Rogers Electric Off-Road 1 06-26-2007 02:59 AM
Method to run-in stock to higher turm motor? or a stock tune to a higher turns? micro80 Malaysian R/C Racers 0 06-16-2007 12:40 PM
Motors,batteries,Trinity Dyna Pulse,Team Orion Advantage Charger,Turbo30 5 button FST WisRacr1 R/C Items: For Sale/Trade 38 03-20-2006 05:50 PM
Higher end radios brushless Electric On-Road 17 05-16-2005 04:47 PM
Disadvantage of stick type battery packs? Blackwrench™ Electric On-Road 1 10-18-2004 12:15 AM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 08:33 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net