# Gradual Acceleration



## Grandcheapskate (Jan 5, 2006)

Hi Guys,
As I work on this early JL chassis, I have it to a point where it runs very fast and quiet. It stalls a lot, but that question is posted in another thread.

I have an original 20v Aurora "brick" power pack, one per lane. I have two contollers wired to one of the lanes; one is a standard Russkit 60 ohm and the other is a converted Russkit controller with a 100 ohm resistor from Radio Shack.

Here's the thing which is confusing me. Now that I have it running like a rocket (all stock), the JL car has no gradual acceleration even when using the 100 ohm controller. I can understand when using the 60 Ohm controller, but not the 100 ohm. When using the 100 ohm controller, I depress the trigger and get partially onto the resistor wires before the car moves - and then it is going too fast to completely control.

In other words, the car doesn't seem to move at all even though I am depressing the trigger. Then I get to a certain point and the car shoots out like a rocket.

I am going to check the controller with a voltmeter to insure I am getting a gradual decrease in the ohm reading as I depress the trigger. 

Any other thoughts?

Thanks...Joe


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## slotcardan (Jun 9, 2012)

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## kriket (Feb 15, 2013)

Grandcheapskate said:


> Hi Guys,
> As I work on this early JL chassis, I have it to a point where it runs very fast and quiet. It stalls a lot, but that question is posted in another thread.
> 
> I have an original 20v Aurora "brick" power pack, one per lane. I have two contollers wired to one of the lanes; one is a standard Russkit 60 ohm and the other is a converted Russkit controller with a 100 ohm resistor from Radio Shack.
> ...


 i had the same problem when i had my 20v transformer hooked up to my track. these jl/aw cars i think are not designed to run on 20 volts, they blast off like rockets as soon as you pullthe trigger, at least thats the problem i had with all my jl/aw cars. I run them at 9 volts now, and they run much smoother and they are still super fast, and had full (slow to fast} speed range on my controller. i even use a 45 ohm parma contoller


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## Grandcheapskate (Jan 5, 2006)

The stalling issue is something I am dealing with in this thread and I believe it is completely related to the pickup shoes...

http://www.hobbytalk.com/bbs1/showthread.php?t=413829

To answer Dan's questions, the entire chassis is completely stock including the armature. The gears have not been lapped but seem to be very smooth. The chassis is probably from JL release 2 through 4. The brushes are stock "V" brushes and I have them set pretty loose. The stock magnets are much stronger than original Aurora so may that be why more volts are needed to get the armature turning?

The 60 Ohm controllers are definitely an on/off switch at 20v. The 100 ohm usually works well but I guess as I get a chassis better and better, eventually the chassis gets "too good" to run at 20v with any controller.

As Kriket points out, 20v may just be too much for the older JL cars. I did hook up my Router Speed Control (RSC) and lowered the voltage to between 3.5 and 5 volts (depending on whether I checked with my digital or analog meter) and held the controller wide open with a rubber band. This allowed the car to go around the track unattended, occasionally spinning out.

So the car will work with as little as 5 volts. I may just have to use the RSC and lower the voltage when I get these JL cars running really well. I just need to find a good voltage for them.

Thanks...Joe


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## slotking (May 27, 2008)

> The 60 Ohm controllers are definitely an on/off switch at 20v. The 100 ohm usually works well but I guess as I get a chassis better and better, eventually the chassis gets "too good" to run at 20v with any controller.


I would test the car with a little more amps
maybe 2 bricks to power the lane at 100ohm and see if that makes it better


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## pshoe64 (Jun 10, 2008)

I think Slotking is on the right track (bad pun) with the low Amp diagnosis. I recently upped the amperage to my track, but stayed with 20 Volts (20.8 to be exact). Once I upped the amperage (10A per lane, separate dual power packs wired in parallel per lane) the gradual acceleration and road manners improved for all of my cars. The pancake chassis really smoothed out with the amps pushing that initial start up of the arm. Does the armature "twitch" from a dead stop, but reacts better once it's moving? That was the symptom I was seeing and the amp increase fixed the twitchiness. I run 60 and 90 Ohm Parma economy controllers. I have black boxes with coast and braking adjustable resisters, but I left those turned off until I got the cars to run smooth with power and controller only.

If you just have a missile for a chassis, slap it under a drag car. You could gear in down with a 18 or 19 tooth crown for a closed circuit. I have a couple of 1st Gen Xtraction chassis that I just put in the drag stable. Great for straight line, but way too unruly for a curve. Kinda like a 426 Max Wedge in a '64 Dodge 330. Great for point A to B racing!

-Paul


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## slotcarman12078 (Oct 3, 2008)

The rear end gearing can also cause the chassis to be on the twitchy side. That big pinion gear is too much. A 9 tooth conversion makes these chassis smoother running. JL's tri-lam 16 Ohm arm is like a Hemi, and the magnets are like Nitrous Oxide. Put the two together with a nice loose chassis and a low gear ratio you'll have a rocket. 

P.S. I know you're trying to stay in the "what came with the chassis stays with the chassis" mode, but when Bud's sells T Jet crown gears, he's selling the newer higher tooth count gear, and will tame your beasts a little bit.


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## Grandcheapskate (Jan 5, 2006)

Increasing the amps for these cars sounds like a good, easy place to start. To hook up the power packs in parallel, I connect positive to positive and negative to negative, correct? This increases the amps but keeps the voltage stable.

If it turns out I don't have another 20v pack, but have an 18 or 22 instead, I can still hook them together and get the increased amps, correct?

Paul is also correct in that it seems I have a little more control once the car is going. But just a little.

Replacing gears isn't something I want to do and hopefully will not need to do.

Thanks...Joe


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## slotking (May 27, 2008)

> Increasing the amps for these cars sounds like a good, easy place to start. To hook up the power packs in parallel, I connect positive to positive and negative to negative, correct? This increases the amps but keeps the voltage stable.


Yes, I think that is right!

because hooking neg to pos increases the voltage


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## slotcardan (Jun 9, 2012)

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## pshoe64 (Jun 10, 2008)

Wiring the DC sources in parallel doubles your amps and takes the lower voltage of the 2 sources. Wired in series adds the volts and takes the highest amp source.

Example:

2-20 Volt sources, 1 is 1 Amp the other is 2 Amp - in series = 40 Volts at 2 Amps.

Same scenario in parallel = 20 volts at 3 Amps.

It is best to use sources that match amperage and volts. You also need to keep resistance between the sources at a minimum, so be sure to use a suitable gauge wire to prevent resistance/heat.

I use two matching 20.8 Volt power supplies at 4.5 Amps each. They yield 20.8 Volts at 9 Amps per lane. I use 14 gauge copper wire to bridge the connection between the power sources and the driver station/track connection.
I have circuit breakers between the power and controller/track connection (8.5 Amp breaker) in the event of a screwdriver or other conductive object (maybe a brass pan) hitting the track rails. I've never popped a breaker yet from normal use and the power sources run cool, even after several hours of racing, tuning or just turning laps.

-Paul


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## LDThomas (Nov 30, 1999)

Failure to get the amps to the motor can also be because of wiring that is too small. It does not matter how many amps the power supply has if the wiring won't let the amps thru...


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## slotcardan (Jun 9, 2012)

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## Grandcheapskate (Jan 5, 2006)

I took out my Router Speed Control (RSC) and started varying the voltage on the 20v Aurora pack. Seems when I got in the 12 volt range, I had real good control of the car using the 60 ohm controller. Smooth acceleration and power all through the resistor band.

While this was a good setting for the well tuned (for me) car, when I put a non-tuned JL car on the track it struggled at 12 volts. But tuning that car is on my to-do list.

Seems using the RSC can allow me to set a good voltage for each car. And since each lane has it's own power source, I could put one on each lane and let the driver dial in their desired voltage.

Thanks...Joe


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## slotcardan (Jun 9, 2012)

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## Grandcheapskate (Jan 5, 2006)

Since at this time I am the only one using the track and all four power packs are plugged into a power strip, I just plug the power strip into the RSC and then I can set the voltage for all four lanes at one time. After all, I am only using one lane at a time.

Joe


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