R/C Tech Forums

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

Reply
 
Thread Tools Search this Thread
Old 11-29-2005, 07:57 PM   #16
Tech Elite
 
POOKYT's Avatar
 
Join Date: Oct 2002
Location: Cabot, AR
Posts: 3,584
Default

Quote:
Originally Posted by John Stranahan
Adrian M-here is the new number
The bigger the number the more stiff the chassis is.

Losi JRXS (Top plate Posts Removed)=1.2 Newton-Meter/degree (N-m/deg)
Losi JRXS (Complete)=4.3 N-m/deg

Removing the posts cut the torsional rigidity by almost a factor of 4

Losi XXXS (Complete) 1.8 N-m/deg
Very close to the new chassis with the posts removed.
John--Not to confuse this issue but I at some times this past year ran my car with the two front posts out and the rear two in place. I did this at the end of race day in the mains as it helped to free my car up when the traction really started to climb. Can you test it with two posts in place? Thanks

Brant
__________________
EA Motorsports--B-Main Motorsports--Blizzard Concepts--Loose Nuts Racing--BigDog Graphics

My Carbon Footprint is Larger than Yours! :p
POOKYT is offline   Reply With Quote
Old 11-29-2005, 08:45 PM   #17
Tech Champion
 
ROBORAT's Avatar
 
Join Date: Nov 2001
Location: JP Raceway
Posts: 5,360
Trader Rating: 7 (100%+)
Send a message via Yahoo to ROBORAT
Default

John: nice to see you active in rctech again. i've always found your topics a one of the best resources for rc tuning. i'm definitely gonna follow this thread closely.
__________________
[YOKOMO BD7][REEDY RACING][TEAM ORION]
[Sanwa][LRP][Protoform]

http://www.hobbyhaven.com.my/
ROBORAT is offline   Reply With Quote
Old 11-29-2005, 09:44 PM   #18
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Brant- Sorry I just put the sucker all back together. Anyway, I too did think this would be a good intermediate stiffness available to the JRXS. You beat me to it with your post. Thanks for the post. I think you could safely guess that the chassis stiffness would be between the two figures that I posted. Offhand I think it would be close to 2 N-m/deg which would be less than half of the original stiffness as only one third of the center box tube (perforated) is brought back in line. The reason this car is so stiff is this center box is very wide and rather tall compared to the XXXS. The lack of stiffness with these post removed leads me to believe the material is not that much better than molded graphite impregnated plastic.

Now you guys that tinker with this chassis flex, I'm curious why you don't move a spring out one hole or something similar when the traction comes up rather than tinker with chassis stiffness?

Roborat- Thanks.
John Stranahan is offline   Reply With Quote
Old 11-29-2005, 10:07 PM   #19
Tech Master
 
Fatboy Joe's Avatar
 
Join Date: Apr 2002
Location: Coming soooooon
Posts: 1,052
Default

John Stranahan:Thank you for the info on the Losi posts. I also drive a JRXS and your infos are very helpful.
Fatboy Joe is offline   Reply With Quote
Old 11-29-2005, 10:21 PM   #20
Tech Elite
 
POOKYT's Avatar
 
Join Date: Oct 2002
Location: Cabot, AR
Posts: 3,584
Default

Quote:
Originally Posted by John Stranahan
Brant- Sorry I just put the sucker all back together. Anyway, I too did think this would be a good intermediate stiffness available to the JRXS. You beat me to it with your post. Thanks for the post. I think you could safely guess that the chassis stiffness would be between the two figures that I posted. Offhand I think it would be close to 2 N-m/deg which would be less than half of the original stiffness as only one third of the center box tube (perforated) is brought back in line. The reason this car is so stiff is this center box is very wide and rather tall compared to the XXXS. The lack of stiffness with these post removed leads me to believe the material is not that much better than molded graphite impregnated plastic.

Now you guys that tinker with this chassis flex, I'm curious why you don't move a spring out one hole or something similar when the traction comes up rather than tinker with chassis stiffness?

Roborat- Thanks.
John--For me it makes a bigger change in feel by removing or adding the posts than just leaning in or out the shocks. I would almost compare it to changing about 1/2 of a spring rate. Plus at my track I knew in the first part of the day I needed the flex untill the traction and rubber built up on the surface. It made it very nice to slightly tune the chassis through the day and then simply put the posts back on for the mains. I am a little lazy also. LOL

Brant
__________________
EA Motorsports--B-Main Motorsports--Blizzard Concepts--Loose Nuts Racing--BigDog Graphics

My Carbon Footprint is Larger than Yours! :p
POOKYT is offline   Reply With Quote
Old 11-30-2005, 12:04 PM   #21
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Brant-Thanks. If anybody else can also describe their luck tuning with chassis stiffness, please make a post. Fatboy Joe-Thanks.

New Toys. Lithium Polymer Battery (LiPo, LiPoly) Scorpion Charger

I just received my new 3200 mA-h Lithium Polymer Battery from FMAdirect.com. Here are some basic observations.

The pack consists of two 3200 mA-h cells connected in series and laying one on top of the other. This type of battery requires special Handling and wiring. If you look at the attached photo you can see some of the special wiring. At the right rear of the car is a standard Deans Ultra Plug. This is for Discharge Only not for Charging.

Also at the right rear is a 3 pin connector that goes to the battery. This is used to charge each cell separately so that no overcharge occurs to one cell.

The battery has a harness that connects to the speed control input of the receiver. The speed control then connects to the battery female plug. This circuit is use to prevent over discharge of the battery. The speed control is cutoff before overdischarge can occur. The Orion LiPo cell will probably not come with this feature but will have a better case and higher capacity (4800mA-h).

The battery requires a special charger, of those available at this time the scorpion 1-10 amp charger seems the best for RC due to the ability to fast charge the pack at slightly more than 5 amps.

Generally if you screw up charging with the wrong type of charger or charging mode, the battery explodes and catches fire. I saw a nice picture of this on the Web along with about 30 incident reports. The flame engulfed the entire pit space. For this reason a dedicated charger that can only charge this type of battery is recommended.

This battery is different from Nicads and NiMH in that the two electrodes are laminated together with a polymer film. This means that the battery requires no thick metal cylindrical case to hold the eloctrodes in intimate contact with the conductive film. The battery is thus very light for its capacity. This 3,200 mA-h battery should come in a few ounces lighter than a NiMh. I'll weigh it later.

I will probably remove a foot or so of lead wire from the battery in the future. I need to get some of this big black shrink wrap first. The battery just fits the Losi JRXS tray but it does not slide in easy due to a big bulge from lead wires on the back end of the battery. The case is supposed to be somewhat delicate, so this is not the ideal situation.

Note that I don't actually run these tires and also they are on the wrong side due to recent R&R. Also the four posts that we discussed above are under the four button heads screws attached to the little side ears on the top plate. You can see one of the posts by the receiver.
Attached Thumbnails
Losi Constant Velocity Drive (LCD) vs MIP CVD-lipo-battery-cropped-70%25.jpg  

Last edited by John Stranahan; 12-19-2005 at 07:59 AM.
John Stranahan is offline   Reply With Quote
Old 11-30-2005, 06:55 PM   #22
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Here is some more data on the Scorpion Lipo 1P2S pack(2 cells in series, only 1 in parallel). The pack weighs only 7.6 oz (216 grams) even with all the extra wires. My NiMh packs weigh about 15 oz.

I put the pack in a ceramic coffee cup/mortar tube (just a little humor) for charging. It is reccomended that packs not be charged on a flamable surface or table top. The Scorpion charger is easily worked. Just plug in the pack. A yellow light indicates fast charging which is adjustable with a simple knob. I like this. This fast charge is supposed to take about 20 minutes to give you 90% capacity. Mine only tookabout 5 minutes as it held considerable charge from the factory. Then a green light blinks indicating slow charge. This took 40 minutes. Then a green light when fully charged.

I discharged the pack on the turbo 30 and set the cutoff voltage to 5.5 which is the internal cuttoff voltage of the pack with some speed controls.
I discharged at 20 amps for 579 seconds. This gave slightly more than the rated capacity. The packs capacity was 3216 mA-h. So far so good. The pack was warm when discharged but not hot.

Voltage
The pack averaged 7.19 volt over the full 579 seconds. The voltage at 5 minutes was 7.15 volt. The starting voltage was over 7.87 volt
Wish my motor was in the back so I would not have to add so much weight back there for this light battery to achieve a good front to back weight balance.
Attached Thumbnails
Losi Constant Velocity Drive (LCD) vs MIP CVD-scorpion-charger-80%25.jpg  

Last edited by John Stranahan; 11-30-2005 at 10:38 PM.
John Stranahan is offline   Reply With Quote
Old 11-30-2005, 07:16 PM   #23
Tech Elite
 
Mike Haynes's Avatar
 
Join Date: Sep 2003
Location: Area 51
Posts: 3,699
Trader Rating: 2 (100%+)
Default

I have run this pack in my car also, and the lighter weight dosn't reall affect the car too much, just throw the maount of lead you need to make up for it in the sopace behind the rear diff and your set.

I did however move my wires, and reshrink it. Pic attacthed...to make it fit more easily.
Attached Thumbnails
Losi Constant Velocity Drive (LCD) vs MIP CVD-p1010121.jpg  
__________________
Team Associated - Reedy Power - Sweep - Protoform - TQ Wire - Lacher paint
Mike Haynes is offline   Reply With Quote
Old 11-30-2005, 07:26 PM   #24
Tech Champion
 
AdrianM's Avatar
 
Join Date: Aug 2001
Location: Tampa, FL
Posts: 5,914
Trader Rating: 4 (100%+)
Default

Quote:
Originally Posted by John Stranahan
Wish my motor was in the back so I would not have to add so much weight back there for this light battery to achieve a good front to back weight balance.
From the looks of all the Losi Prototypes running around you will get your wish soon.
__________________
Adrian Martinez
What I run: Schumacher Mi5/Associated RC10R5.1/Associated RC12R5.2/Futaba/HobbyWing/Team EA Motorsports/BSR Racing
Where I run: Florida Indoor R/C Complex/Thunder Racing/Florida On Road State Series
AdrianM is offline   Reply With Quote
Old 11-30-2005, 07:56 PM   #25
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

RCracingkid-Thanks for the pic. That's a good plan to reshrink it. Nice. I know that I can add weight to balance the car, but since most of this stuff is not legal for racing yet anyway, I would rather run a light car when using this battery and motor. I seem to need at least a couple of extra ounces in the back over the weight of the front for good front to back balance.

Adrian-I had heard on one of the Losi sites that a new kit will become available to convert to rear motor drive, but it probably will include a new chassis (OUCH). My kit is brand new. So it goes.
John Stranahan is offline   Reply With Quote
Old 11-30-2005, 08:44 PM   #26
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

.

Last edited by John Stranahan; 02-05-2006 at 09:27 AM.
John Stranahan is offline   Reply With Quote
Old 11-30-2005, 10:34 PM   #27
Tech Apprentice
 
weliin's Avatar
 
Join Date: Oct 2005
Location: Gnomeregan
Posts: 86
Default

Hi John I always enjoyed reading your posts on the TC3 back in the day. I'm sure I'll enjoy this thread equally as much and I can maybe contribut now because I've been running the Losi products for some time.

Question for you. Is the LiPo batteries any good in stock racing at the club level? Or is the NiHm still much better performance?

Also I'll be interested in if you experience the front end suspension of the car developing alot of play just after a few weekend's of racing/practicing.
weliin is offline   Reply With Quote
Old 11-30-2005, 10:42 PM   #28
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Weliin- The higher the voltage the better the battery for stock. The LiPo batterries have considerably higher voltage curve than my old batteries. I have not run them in the car to check the feel of the battery yet. They may not be allowed for club racing at your track though. Check before you buy. Did you have a different screen name previously?

I have not run the car yet. I have some photos to take of it yet for a project.

BTW the TC3 assembly tips thread is still here.

Last edited by John Stranahan; 02-05-2006 at 09:29 AM.
John Stranahan is offline   Reply With Quote
Old 12-01-2005, 01:33 AM   #29
Tech Adept
 
Pembalap's Avatar
 
Join Date: Aug 2001
Location: Indonesia
Posts: 207
Default

By the way, how many cycles (Charge-Discharge) for Li-Po? At least the Li-Po in PDAs will have more than 300 cycles. I charge my PDA everyday and it still hold pretty well after more than 1.5 years.

Moreover, PDA and Cell phone users never have to discharge the battery, and the Capacity is not really degraded. So, these kind of Li-Po need to be discharge everytime or not?

Thanks
Pembalap is offline   Reply With Quote
Old 12-01-2005, 06:51 AM   #30
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Pembalap-The LiPocell is supposed to have no memory. It will never need to be discharged on a tray to prevent memory effects. The charger and cells that I use, are balanced on charging so they will not need to be trayed on a discharger to balance cells either. The lifetime number of cycles reported by manufactures vary, but is very high 300 to 500 cycles. One reports 15,000 cycles.
One drawback for RC use is the cells cannot be peaked as the voltage never drops. This means that charging slows to a crawl as the cells become charged. The Charger needs to limit the voltage to a preset voltage to limit the charge. This limits the current flow as the cell charges up.

I charged my cell and let it sit overnight to see how long it would take to top it off (I would say repeak, but this is innacurate with this cell). The charger went into its blinking mode, it took 15 minutes to top off. The discharge time was only 4 seconds less, but the voltage is much reduced from 7.19 V average charging just before use to 6.89 average after sitting over night, topping it off, and then a discharge.

Last edited by John Stranahan; 12-01-2005 at 07:12 AM.
John Stranahan is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
ORION CRF Constant Pressure Device CPD RC MARKET Nitro On-Road 3 10-06-2007 09:21 AM
Loaded Kyosho ZX-5 4WD, Novak GTB/Velocity 5.5, Losi MF1 jsmax R/C Items: For Sale/Trade 7 07-31-2006 08:05 PM
Help: Transmitter constant glitching rbridd Electric On-Road 5 09-01-2005 02:13 PM
WTB:Losi XXT hop ups,bodies,Pro-Line Velocity Dish's, and Novak XXL fm 75mhz dennyboy424 R/C Items: Wanted to Buy 1 01-21-2004 11:05 AM
Gear Ratio Constant? trey Nitro On-Road 2 11-02-2003 05:28 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 06:57 AM.


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