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Old 12-01-2005, 07:09 AM   #31
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John - I noted that your Turbo 35 cut off was 5.5v. That is a bit too low. You should never take LiPo's below 3.0v per cell or 6.0v for a 7.4v pack.

LiPo's do not have memory and they last a VERY long time as long as you follow the care instructions.

There is a LiPo FAQ on www.teamorion.com that covers pretty mush all the details. Note that the cells Orion uses in thier LiPo's are the state of the art and are diffrent from any other LiPo cell on the market today. They can handle more mistreatment than currently available cells.
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Old 12-01-2005, 07:22 AM   #32
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Adrian-Thanks for the tip. I'll adjust my cutoff Voltage to 6. The voltage is droping like a rock at this point.

I chose 5.5 because the built in internal voltage cutoff of the cell is 5.5 with some speed controls. Apparently the cells have been tested at this voltage. I doubt choosing 6.0 V will affect the capacity measurement. I'm retesting the cell by charging and immediately discharging. Plan to get an Orion cell, but did not find them readily available yet.
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Old 12-01-2005, 11:58 AM   #33
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Heres the fourth LiPo discharge test, this time with a 6.0 Volt cuttoff and a discharge right after charge.

7.20 V average (nice, the cell is not dead)
568 seconds at 20 A discharge 3155 mA-h
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Old 12-01-2005, 05:54 PM   #34
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I confess, I did not know what a Skoda was, the body on our JRXS. Here is a link to pictures of the full size Skoda car.
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Old 12-01-2005, 05:58 PM   #35
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Quote:
Originally Posted by John Stranahan
I confess, I did not know what a Skoda was, the body on our JRXS. Here is a link to pictures of the full size Skoda car.
Sounds like you need to get out more instead of getting so high tech on toy cars!!
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Old 12-02-2005, 12:37 PM   #36
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Rewiring and ReShrink Wrap the LiPo Battery

I was curious what was under the shrink wrap of the Scorpion Lipo Cell. As expected there is quite a bit of extra lead wire. The batterry is actually composed of two long thin cells stacked on top of each other. All the lead wire connection are on one end. Now I'll have to warn you that a slip of the Xacto knife on these cells will weaken the case and may let them explode in your ceramic mortar tube. I used a pair of scissors with a ball end to remove the shrink wrap. I found a piece of !.5 inch thick shrink wrap at Frey's Electonics in Houston. It is made by Tech-Tron and comes in basic white or black and four other colors, yellow, light blue, pink, light green. (The blue pink and green are pastels. I'll post another picture here on this post when I get the cell put back together. Be careful and save the decal.
On the photo you can see the little printed circuit board that contains the low voltage shutoff. A clever enthusiast could probably install this permanently in the car to save hassle. Both positive and negative discharge leads initiate on the same side and then go to the far end to exit the shrink wrap. The PCB to which the leads are soldered was covered by a separate piece of shrink wrap to insure coverage.

It seems that this battery has the best voltage right after charge. Even a 15 minute wait deteriorates the average voltage of the discharge quite a bit. If you have tests to confirm this please tell me.


Photo 4, This is plan B. the first plan I posted was a little snug in the car and rubbed the rear drive pulley.
The blue shrink wrap went on OK. I wrapped the PCB contacts and first half inch of the sides of the battery with with some rubber electricians tape, not the thin vinyl, but thick soft stuff (Scotch 2242 from Home Depot). I covered this with Scotch vinyl electricians tape. Then I cinched it down around the short circumference of the battery with tape. I cut a notch in the long shrink wrap for the wires. This allowed some more flexibility in the lead wires over cutting a hole there. This shrink wrap is good thick stuff and works easily. It should cushion the battery well. The fit was snug but easy to install in the car. See the last photo. Now I don't recommend that you tinker with your battery, but if you plan to anyway, this is what I did. The leads will exit the Losi JRXS at the rear as there is no interference with the center shaft this way. The battery weighs 7.1 oz or 200 grams now. It lost some weight (about a half ounce). This compares to a 13 ounce NiMH of similar capacity.
Caution]
If you modify your LiPo like this you must stop when the car slows. You cannot wait till the car stops. You may kill the cell if it stops. If you leave your speed control connected over night this will deep discharge the cell and kill it, even with the little electronic circuit onboard the battery.

Yeti35- I tinker with the big ones too. Here is a link (Cold Air Intake Airbox on a Ford Focus ST) Have not come up against a Skoda yet.
Attached Thumbnails
Losi Constant Velocity Drive (LCD) vs MIP CVD-scorpion-3200-ma-h-lipo-pack-stock-022.jpg   Losi Constant Velocity Drive (LCD) vs MIP CVD-scorpion-3200-ma-h-pack-003-cropped-70%25.jpg   Losi Constant Velocity Drive (LCD) vs MIP CVD-scorpion-3200-ma-h-lipo-pack-car.jpg  

Last edited by John Stranahan; 01-21-2006 at 06:35 PM. Reason: Rewiring the LiPo Battery
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Old 12-02-2005, 07:06 PM   #37
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Battery Modification: Results Up .050 Volts (50 mV)

I retested the dishcharge with 1 foot of lead wire removed from the battery. the discharge voltage was .050 Volts higher at 7.25 volts for 20A discharge and went 574 seconds for 3188 mA-h.

The two photos show the finished wiring in the Losi JRXS with two types of battery. I have used homade Dean Half Plugs on the Speed control so that I can use my old batteries without modification. The installation looks very neat though, I would probably have used them anyway.

The other photo is with the Lipo Battery.

More Losi JRXS specs with this Lipo Battery

Front to Back balance with Scorpion Lipo
Total weight 48.6 oz
Front weight 25.1 oz
Rear weight 23.4 oz

I'll probably have to increase the rear weight to run this battery.

I know a lot of guys run light cars for club racing. This setup should be ballistic in stock if the informal rules allow LiPo batteries.

Front to Back Balance with NiMH
I have some NiMH packs that weigh about 12.4 ounces. The Sanyo HV weigh 13 ounces.
with 12. 4 ounce pack
Total weight 53.8 ounces (no transponder)
Front weight 26.6 ounces
Rear weight 27.2 ounces

Left to Right Balance
left side 27.7 ounces
right side 26.1 ounces

With a transponder in the back on the right side, the balance would be good.


The Sanyo HV batteries in the photo did not fit the stock battery tray. The Aluminum tray should work with them, but I hear it's not available yet.
Attached Thumbnails
Losi Constant Velocity Drive (LCD) vs MIP CVD-losi-jrsx-dean-half-plugs-lipo.jpg   Losi Constant Velocity Drive (LCD) vs MIP CVD-losi-jrsx-dean-half-plugs-002-cropped.jpg  

Last edited by John Stranahan; 03-22-2006 at 12:28 PM.
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Old 12-02-2005, 09:39 PM   #38
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the aluminum battery tray has been available for awhile....it's just hard to find places that have them in stock
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Old 12-03-2005, 10:07 PM   #39
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Default CORNER WEIGHTS

RCanonymous- Thanks. I'll keep an eye out for one.

The Losi passed the smoke test. Setup of the GTB was easy like the other Novak speed controls. Full speed is reached almost instantly on the bench with rubber tires and a little over geared. Top speed seems a little slower on the bench than a brushed mod, but this is probably irrelevant.

Corner Weights

Weight the car and decide how much weight to add. I added enough so that with transponder and a light NiMH the car weighs 54.1 ounces.


Side to Side Balance
I have two inexpensive postal balances. I put a 1 foot by 3/4 inch square thin wall aluminum extruded square tubing on each balance. Put the left side tires or or setup wheels on one bar and balance, and the right side bar and wheels on the second balance. The difference is the ammount of weight you need to add to balance the car side to side. This may be more that the weight that will get you up to minimum weight. For mod you might use this heavier weight to heat the tires evenly. For stock you may want to use the weight above and live with a little unbalance as the tires are not stressed as much.


Front to back Balance

Weight the front and the back and decide where to put the weight longitudinally in the car to get the weights you want. I like the rear about 1-3 ounces heavier. In a corner, weight transfers to the front from deceleration and a more even tire loading is achieved with the rear a little heavy.

I put a 1 foot by 3/4 inch square thin wall aluminum extruded square tubing on each balance. Put the front tires or setup wheels on one bar and balance, and the rear bar and setup wheels on the second balance. Now experiment placing the weight at different points along the length of the car until you get the rear excess that you want.

Corner Weights
As a final step, you want both front wheels to have the same load and both rear wheels to have the same load. Because the GTB motor's can is a little long and the GTB's controller is a little heavy, the right side of the car is light. I know already that I need my ballast as far back as possible and to the right if possible. Put the rear wheels on a stack of bars that equals the height of the balance. I used a couple of pieces of 3/8 square keyway stock (Hardware store or Home Depot) under my two 3/4 inch pieces of square stock. Deburr all the ends. See the photo.
Put the two front wheels on the balances and adjust the front spring length until the balances read within .2 ounces or so. This test is done with your ballast in the place you think it should go. Bounce the front and back of the car several times to relieve shock friction. Now turn the car around. If the weight was placed properly in the car then the balances would still be equal. I put the transponder on the right rear corner and added a chunk of lead on the right side behind the rear diff tube. Weights were within .2 ounces. This is about as close as you can do it with shock friction, and as close as you need to do it for use on the track. You only need to do this once when you build the car. Recheck your work.

A car on rubber tires on pavement will produce the best cornering power when the tires are evenly loaded.


From now on set tweak at the track using a tweak station.

Note-I used a long flat head screw on the pivot block coming up from the bottom to secure the front transponder mount screw with a nut. The rear screw shares the hole with the pin on the pivot block. I used a short screw here. It will only serve as a pin to prevent rotation. Your transponder may need to be further forward in the car with different equipment.

I remounted the transponder practice weight 1/2 inch farther forward than in the photo and put it above the support to better tuck it under the rear of the body. It looked better there with the body on.
Attached Thumbnails
Losi Constant Velocity Drive (LCD) vs MIP CVD-corner-weights-cropped-70%25.jpg  

Last edited by John Stranahan; 02-05-2006 at 09:31 AM.
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Old 12-04-2005, 08:27 AM   #40
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John,

I think you bring up a point when discussing weight balance. Many racers either just don't think about or simply forget to do it. A blanced car is just easier to drive and responds better to changes.

I found my left rear a bit light with "normal" electronics by about .5 oz when using a V2 motor, GT-7 Speed controller, 12 guage wireing, and a mini-Airtronics reciever. I added the balist just behind the reciever. I would imagine I could almost eliminate all my balist weight if I got a new GTX speedo or something similar.

With your transponder mounted in that position it makes it more vunerable to damage. Most tracks around my area would not allow the transponder to be mounted there.
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Old 12-04-2005, 08:36 AM   #41
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Weliin- Thanks for the post. An alternate position for the transponder in my case would be the right rear deck lid on the body. This would keep it out of harms way. Personally, I would like to see personal transponders become the norm. It would make racing much more streamlined. Then you can put this ballast where it needs to be. It is tucked much more out of the way with the new position above the mount and 1/2 inch forward.
Also note that for a close finish it would be better to have the transponder in the front, but for most races that I see, this is never a problem.

Now what do you guys do for a locked front diff on this car. I'm thinking of making one.

Last edited by John Stranahan; 02-05-2006 at 09:33 AM.
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Old 12-04-2005, 08:43 AM   #42
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Personal transponders are the norm everywhere ive went
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Old 12-04-2005, 02:36 PM   #43
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For locked diff I think most people create the spool using the spool pads from the XXXS. I might be wrong but I think that's how they are doing it.

I've never ran the spool. I'm forced to run carpet with foams, I think a spool would take away to much steering going into the turns for the track I run on. I might be wrong but someone else would have to prove that to me.
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Old 12-04-2005, 07:04 PM   #44
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weliin-Thanks.

Here is a picture of the finished corner weight ballasts. I ended up using 2 strips of lead totaling 1.7 ounces on either side of the diff support on the right rear side + the transponder weight. This makes the car a little overweight, but should work better in Mod by being balanced. Rear corner weights are within .2 ounces now. Fronts are the same. Rear is 2 ounces more that the front. Ready to run it, but waiting on some gears.
Attached Thumbnails
Losi Constant Velocity Drive (LCD) vs MIP CVD-6-touring-car-setup-finished-003.jpg  

Last edited by John Stranahan; 12-04-2005 at 07:17 PM.
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Old 12-04-2005, 10:40 PM   #45
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Default Novak GTB 6.5 Motor Guts

Had to see the insides. You probably have heard the brushless motors described as a regular brushed motor inside out. The photo shows the various parts. The rotor is a permanent magnet that is quite strong (Neodynium). The stator, or can, contains the windings. There are three windings. Looks like more than 6.5 per coil. Now I imagine that in order to save on the already numerous wires that the motor has one end of each winding on a shared wire. This is probably why we can't use shottky diodes with it. I would imagine the current is still pulsed like a regular speed control. If there were six wires then three shottky diode would improve the efficiency still more. I don't know this for a fact. If you do, please report on this particular aspect. I do suspect the coils are switched on sequentially creating a rotating magnetic field which the permanent magnet follows.
Found one thread protruding from the lead wire side of the rotor. I nipped it off flush. Don't know what it does. It could be the rotor is wrapped somehow to increase strength or to hold it together.

The motor weighs about an ounce more than a regular mod which explains partly my need to add more weight to the right side of the car.
Attached Thumbnails
Losi Constant Velocity Drive (LCD) vs MIP CVD-novak-gtb-6.5-guts.jpg  
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