T. Thomas

John, your running a JRXS, the motor is centered along the center line, the speed controller weighs a lot more than a conventional speed controller, between the controler weighing more and the added wire, that is why you nee to add more weight to the right side of the car.

John Stranahan

iTrader: (27)

T- I am running the JRXS. I agree that the reasons you mentioned add to the problem and that a normal mod's weight is centered. This Novak GTB 6.5 motor is about .5 inch longer than the normal mod. And unlike a mod the left side of the installed motor is all metal as far as I can tell, the right side containing the bearing is a light aluminum part. A mod's installed left end is light plastic, the right side is part of a steel can. The brushed type of motor is what the chassis was probably designed for.
I estimate the balance point is about .25 inch left for the brushless by balancing it.

Here is a pic of one of the sensors in the GTB 6.5 at the lead wire end of the stator inside the can. These sense the rotation of the rotor and helps the speed control improve bottom end torque according to Novak.

T. Thomas

Here is a simple way to find out if the motor is shifting any weight bias from side to side. Remove the speed controller, and measure the cars weight on each corner with just the brushless motor, then replace the brushless motor with a brushed motor(epic shock, trinity cobalt, or orion V2, since they all have aluminum end bells(except the cobalt but it does have those two large heat sinks with breathing holes) and build in circuit boards inside the endbell) and then take the weigh at each corner again and compare the difference. I agree that the motor may have a slight shift, but nothing neirly as noticable as you may think.

AdrianM

iTrader: (4)

You guy do realise that Pro level drivers do not do any of this. 90% of them have an MIP tweak station, an RPM camper gauge and an xacto knife and that is it for setup tools...i'm not kidding!

Just put the stuff where it fits, tweak the car and go race!

John Stranahan

iTrader: (27)

Have to disagree.
Here is a link to a picture of Barry Bakers Race Winning TC3 the last time he raced in Houston. This photo is already on this site.

Barry Baker TC3

The center chassis stiffener has been milled about 1/8 to 1/4 inch, to move the heavier batteries, that came out, closer to the center. Previous to this mod, most racers used to run the transponder outboard of the chassis just to the right of servo. With the mod they changed to over the servo. Now you don't see Barry adjusting weight in his car at a race, but obviously somebody does adjust it. I don't think they used an X-acto knife. If you use the equipment the chassis was designed for the weight will be pretty close with normal placement of components. After you get the weight right you can use an X-acto knife to set tweak at the track or a tweak station.

Here is another picture showing half the center rib removed. There used to be complete x braces in there.

http://www.rctech.net/forum/attachme...chmentid=12110

Don't plan to be a proffesional racer. Running the cars is just a hobby for me. Gadgets are part of the hobby.

John Stranahan

iTrader: (27)

T- no need find the source of the imbalance. I agree with you that there are several sources. My car is within a few tenths ounce side to side now.

AdrianM

iTrader: (4)

Jon - I am not trying to give you a hard time. Its just that novices see this thread and think that they need to have all this stuff to compete. I just wanted to say that the guys that are the best in the world use very simple tools and do very well. I too am a tinkerer but I work with a pro r/c driver and he razzes me when i get too techie...lol!

Re: Barry's TC3...

Curtis Hustings did those mods at AE on a mill. The request from Barry was to get the battery as close to the shaft as possible. He asked for this because the ride height on a stock TC3 was usually .5mm lower on the battery side and he was trying to fix that. He used a ride height gage and eyeballed his shock collars. Thats as scientific as it got...lol!

Milling out the ribs was a common factory driver mod to get more flex into the car for more traction. Usually they milled the ribs out of the chassis for asphalt races. They also milled the bottom of the chassis to make it actually flat, they routerd the bottom sides of the chassis with a 1/4" round over bit then sanded them smooth.

The transponder mount hanging off the right side of the car was abandoned after a few team guys lost transponders due to crashes not for weight distribution.

John Stranahan

iTrader: (27)

Funny we set the weight in Christian Tabush's car (second place) properly, complete with a center rib mod, and it ended up looking pretty close to Barry's when we compared the two during and after the race. There are several ways to the same end.

Same size bits of lead beside the motor too.

btsai

Adrian, thanks for writing this:

"Its just that novices see this thread and think that they need to have all this stuff to compete."

I am an old novice of sorts -- I used to race 1/8 scale gas in the 80's here in AZ. I'm now interested in returning to the hobby in electric touring cars.

With all the manufacturers out there, I have been trying to evaluate which car(s) I should consider -- and specifically, which one(s) may be better from their initial design (for example, I find the center line design of the JRX-S very interesting) as well as which ones might be the easiest for the average hobbiest to set up. It looks as though some of you are way beyond my area of expertise in tech set up -- that level would be something to aspire to if I ever got to that level. In the mean time, I just want to have fun, but be reasonably competitive.

Further thoughts? I know you have some "built-in bias" due to your manufacturer tie-in, but constructive input from you or anyone else would be most welcome.

Thanks.

P.S. -- Sorry -- not trying to hi-jack this thread -- I just find the whole topic very interesting.

AdrianM

iTrader: (4)

I can honestly say they with all the great cars that are out right now you really can't go wrong. Pick one that appeals to you and stick with it. That may not be all that helpful to you but its the truth.

Read a few of the car threads and ask the guys why they like their cars. Get a feel for the support you will get online and from the company.

John Stranahan

iTrader: (27)

LiPo track test

I tested the Scorpion LiPo battery today in a TC3 with a stock motor on an oudoor asphalt track. Ballistic. Having the car light was part of this I am sure. I took the LiPo right off the charger a few minutes before the light would stop blinking fast on the Scorpion Charger. Very high top speed. Very good punch. I think I can gear up one 48 pitch pinion tooth over what I used on the same track with NiMH. I'll test this next time out. I will also have a GP 3600 NiMH assembled by then for a back to back test. Easy to tell when the car slows, so no problem here overdischarging the pack. The Aluminum battery trays are in stock at Stormer Hobbies. I have one in hand which will be essential to run the larger diameter 3600's in the Losi JRXS. It took a very long time to charge that Lipo up.

John Stranahan

iTrader: (27)

Losi JRXS-Nice Features

I have had some time to study the JRXS design features in depth now. I have not driven it yet. I still have some things to do to it and the body.

1 The 4-40 diff nut is a large size and seats in hard plastic. This is a great improvement over the tiny diff nut seated in weak plastic that Losi has used previously on its kit. The plastic T-nut that holds the opposite side outdrive on has a good long bearing area on the threads. It should hold up. It is not nearly as higly stressed as the diff nut which has to be made quite tight to prevent the ball diff from slipping.

2- The outdrive cups are huge, full circle rather than slotted, and beefy. Anyone that uses a one-way or locked diff will appreciate this. The two cups can be purchased together without a lot of other hardware. The fact that they are not slotted probably tripples their strength.

3- The Diff Tubes are large diameter, increasing torsional stiffness. The front and rear pulleys are on opposite sides. Both of these facts should reduce toque steer or the car pulling to one side when you hit the throttle trigger hard. (Give me a torque steer report if you have noticed or not noticed this)

4-The Spur gear will be so easy to change when things get broken in well. Only one C-clip holds it. In stock a spur gear change might be neccesary to fine tune the gear ratio. If you run outside you might want the newly released 48 pitch gears or a handfull of the fine pitch spurs. The little rocks won't so easily destroy the bigger pitch. Having the gears exposed is a detriment in my book though. Nothing beats the XXXS on loose outdoor tracks for the sealed drivetrain and great top speed in stock. The XXXS is not so good in stock, though, on a high grip track.

5-Chassis Stiffness is easily tunable in 3 stages by removing supporting posts. I was enlightened by racers of this thread.

6-Center pulley allows for a center one-way and front one way. Hard to do this on a TC4 or XXXS.

7-The stiffness and strength of a part increases markedly the shorter it is by several powers. I'll look up the exact figure later. These short arms and short drive axles should be much stronger than the longer parts on other chassis especially those on the TC4. You might instead break the Caster blocks, though. (please give me an A-arm breakage report.)

8-When a male threaded fastener breaks it usually breaks at the area right between end of the threads and the smooth shaft of the bolt (or ball stud). On the JRXS, having the ball ends on the shocktowers as female nuts that are fastened on by socket head cap screws, removes this weak junction to a safer place, by the head of the bolt. The head is not stressed by crashes in this application. A standard ball stud here is more likely to break off. I have not had this problem too much on a touring car, but it sure is a problem on the inner rear camber link ballstud on the truck.

9-The pinned chassis plates. This should prevent the chassis from staying twisted after a crash. This really screws up the handling.

10- The starter subject of this thread. The JRXS has true constant velocity drives for the front axles. Lightweight MIP drive axles for the rear.


Don't like
the front mounted motor. I have already had to add a ton of ballast to the back. The new rear motor kit will probably be out at some great cost no doubt.

Do not like the open gears outdoors.

Chassis is not wide enough to protect my GTB controller

Don't care for ball pivots on any heavily loaded suspension point in a 1/10 scale RC vehicle. The inner A-frame pivot mounts on the Losi are nice in that you can adjust antisquat and kickup without a new part, but they will probably develop slop even though they don't really need to move at all. Ball pivots on the uprights that support the axle ends all have increased friction over pins. Fortunately the Losi JRXS does not have these. (Give me a report on wear of the pivot ball area if you have one, it may not be a problem at all.)

Now whats that third body post in the front good for if you don't perforate the body for it. Roll overs are the least of our concerns.

The front airdam on the Skoda II body which I ran on the TC3 split right in the middle on the first impact. It does not really need to be so angled or maybe it was just too cold.

More to come when I run the car.

imjonah

I was trying to come up with an enduro race class (don't ask me why) that would actually require brushless motors and li-pos.

I was thinking about an oval or track with all high speed corners and extended length heats 12+ minutes with no battery changes allowed.

What race length would require the efficiency of brushless and the capacity of a lipo if you wanted to reliably finish.
In other words a race length that NIMH with brushed or burshless would dump or a LiPo with a Brushed would dump.

Also am I correct to assume that if a racer went with brushless and lipo from day one; never bought a brushed motor or a NIMH battery, that they would actually save money in the long run?

Finally, relative to rubber how well do you think Foams last on outdoor asphalt with electric touring cars, I am thinking club level racing where people may use the same rubber tires for 6+ Sundays of racing.

Thanks,

John Stranahan

iTrader: (27)

Not in any order
The foam durability depends a lot on the skill level of the driver. The tire fails when it chunks or loses a bit of foam. At this point the car does not handle as well although there is plenty of tread left. If you rarely crash in a race they hold up pretty well.

The rubber tires hold up very well. Takeoff CS 27 and 32 tires hold up exceptionally well. I am always glad when the temperature is right for CS 27s. 30 runs (battery packs) on a set. Sorex 32's are a bit better than CS 32 traction wise, but they wear out a bit quicker. Note that a rubber tire is fastest brand new in the first race. Don't waste this new rubber on practice. Only take 1 or two tryout laps. The number is the celsius temperature the tires are designed for. When you run mod the tires heat up more and may require a rating higher than the track temperature.

The Lipo battery that I purchased is a Scorpion with 3200 milliampere-hour (mA-h) of capacity. Some NiMH packs have higher capacity. Orion is coming out with a Lipo with 4800 mA-h of capacity. They probably had this cell designed as large as possible to fill the standard battery tray on the touring car. My Scorpion pack is smaller than the tray. I don't like the built in connectors of the Orion pack as they tend to get loose and can come unconnected in a race. I would rather have two solder terminals or two pigtail wires.

Some guys at Reflex which was an indoor asphalt track (high grip) were actually dumping a 3000 mA-h battery in 19 turn class in 5 minutes (well actually just Tommy). A Novak Sportsman brushless would probably give you about another minute if geared to the same performance as the fellows 19 turn (It would give me several more minutes as I gear a little lower) at Reflex. Outdoors with less traction more minutes still. The Orion Lipo would give you two more minutes above this Scorpion pack (again most guys would get a few minutes more), estimate is 9 minutes indoors maybe 10-12 outdoors on a dusty track. It is best, in my opinion, especially for a sportsman class, to time the race short enough so everyone finishes without dumping as this is a frustrating thing to happen to a car that is running pretty well..

A good thing about NiMH packs is you don't need too many. They get faster with each run on a day, so you can just get two. One is charging while the other is running. Some lag time in between for motor cooling and charging.
With a Lipo, it takes forever to charge, they are real expensive right now, They need to be run right after charging for the best voltage. You might need more than two for a pleasurable outing and also two chargers. There is a large decrease in Voltage after only 15 minutes delay from charge to run. Timing the charge during a race is going to be crucial so it peaks at the right time. A NiMH you just repeak if needed. Repeaking is not reccomended for a LiPo and is a very slow process as well. The Lipo characteristics, I have only learned recently after purchasing and testing one. I don't think running LiPos is going to be cost effective. From the construction and material costs they seem to me like they should be cheap to produce. Don't know why they want to charge us a billion dollars for them.
I plan to use my radio's timer to see how long this Scorpion Lipo will run a stock motor before performance falls off. Tomorrow. I'll have some data on a GTB 6.5 and the Lipo later on.

So here is the test plan TC3 stock untill I get back pretty good again. TC3 mod with brush motor and Lipo, TC3 with GTB 6.5 and LiPo, the Losi JRXS GTB 6.5 LiPo. This is going to take some time, but I will enjoy every minute on the track.

The photo is of my favorite wheel. Not so hard that it is brittle, not too soft, so it does not stay bent after a crash like a soft wheel. Looks great. CS tires also come premounted on this wheel, I believe. Could not find a supplier with a photo to verify this. Tires are CS 32's with nine runs. When you run CS tires its important to have a long lasting wheel or the wheel will break before the tire is worn out. I'm getting to the paint on the body. Goofed up the trimming of the sides of the first body. Note the 48 pitch gears for use outdoors.

I have since learned that Takeoff's come on Speedmind wheels. The closest one to this wheel is the mesh wheel. I hope it is equally durable.

imjonah

If I read you right, Lipo is not practical for racing right now?