[RACING LINE]

I have done a search on this forum and found that most of the topics about stuttering cars are regarding digital layouts. My layout is analogue Sport and certain cars seem to stutter in the same places.

The rails look perfect, the voltage is perfect and conductivity is spot on (tested with a meter). I have tried Inox MX3 and electrical contact cleaner on the rails with no change. I have changed the braids with little effect.

The only other thing I can think of is that the front wheels are lifting the braids from the track in certain places. Any other ideas?

 

[Kellerkind]

ZITAT(RacingSnake @ 1 Jun 2012, 16:16) <{POST_SNAPBACK}>...The only other thing I can think of is that the front wheels are lifting the braids from the track in certain places. Any other ideas?

...you might check this by removing the frontaxle off the car and try to drive without for some laps. Regards Jens

 

[RACING LINE]

I was trying this as you were typing, no difference.

My next guess is that is is a combination of the poorest track location and the poorest conducting cars i.e. the weakness in each brings out the weakness in the other.

 

[matthew77]

Hi,

If the track is fine, check the cars. The motors may be on their way out (this can be checked simply by watching the red light on the sport powerbase as the light will dim or go out altogether if the motor is defective). Also the wiring may be loose either on the motor or where they attach to the guide.

Hope you sort the problem soon!

Thanks

Matthew

 

[300SLR]

Sounds like you've tried the obvious things and it is something else. Here's some ideas about what the obscure fault could be.

If the problem is only happening in particular parts of the track, its quite unlikely to be motors on the way out. If a motor was defective, it would be expected to be defective all the way round the track.

Are the cars driven with the tail out where you have the problem? Just possible the conductors in the lead wires are cracked inside the insulation and this only shows up when the guide is turned.

Are there changes of gradient or banking where the cars are stuttering? This can cause pick up problems.

When you say you have tested the conductivity with a meter, exactly what have you measured?
Simply measuring the voltage with no load applied doesn't detect poor conductivity at track joints.
Measuring the voltage when the track is passing a current will show poor conductivity at track joints.

 

[RACING LINE]

300SLR

Thanks that sounds like an area worth investigating.

The key factor is that a few of my cars stutter at exactly the same places so it has to be a track problem which some cars are more sensitive to than others.

Regarding the electrical tests, I have tested the voltage with a volt meter, throttle fully depressed, no car on track and the reading is the same as all other parts of the circuit 15.64 volts. For connectivity I set my meter to ohms(?) and just checked either side of the joints in each rail but again this is done with no car on track and no throttle.

The stuttering can be more pronounced when using full throttle which suggests that there is a problem that my tests are not identifying due to my lack of knowledge about the relationship between volts/amps/connectivity.

 

[RichD]

Open circuit voltage readings taken on a track with poor connections are actually almost meaningless. The reason for that is that poor connections act like resistors and the voltage drop across a resistor is proportional to the current flowing through the circuit. The method that you used would only find a problem if something was completely open and even then there would have to be several opens on the same rail. With Sport track the rails can be a little lower than the track surface, so you may need to fiddle with the car's braids to make sure that they are not just riding on the track surface. In order to troubleshoot the track you need to disconnect the last track section from the section with the powerbase. Put a car on that last section with sometrhing under the back of the chassis to get the rear wheels off of the track. Strap down the trigger of the controller for that lane, hopefully the motor will run, if not you will have to move the car backwards around the track until it does. Now you can start at the connected end of the track and locate the bad joints. You can take voltage readings across the joints on the same rail, if the joint is bad you will read the voltage drop, if the joint is good there will be no reading. Rail to rail readings will find the section that has lower voltage, but it won't tell you which joint is defective.

 

[RACING LINE]

QUOTE (RichD @ 2 Jun 2012, 15:18) <{POST_SNAPBACK}>poor connections act like resistors and the voltage drop across a resistor is proportional to the current flowing through the circuit.

Does this explain the fact that the stuttering seems worse with a full throttle?

I have noticed that the rails often sit lower in the track compared to Classic, but my test removing the front wheels suggests this is not the source of the problem unless the guide plate itself is riding on the black plastic.

Are you saying that I need to check the voltage with a car on track (but supported) with the throttle full? So far I have only measured the voltage for each section with throttle full but no car on track. Testing Classic track seemed easier, it was simply a case of checking to see which joint had an open connection on the track section where the car stopped.

Thanks for the suggestions, you clearly have a better understanding of electrics than me.

 

[RACING LINE]

This looks similar to what you are suggesting

http://www.slotcar.org.uk/trackbuild/maintpower.htm

I will get busy.

 

[RichD]

If you leave the track sections connected all the way around then power can get to the car from two directions, making it more difficult to find bad connections. Connections that are completly open are easier to find, but for a car to actually stop running there has to be a break on both sides of the part of the track that is giving you trouble. With the track disconnected at one end you eliminate the confusion of having two paths for the electricity to take. If there are indeed some poor connections the problem would be worse with cars that use more power. More powerful cars use more current, the more current the bigger the voltage drops across the bad joints will be and the voltage that the car sees will be lower.
I am still not certain that the braids are making good contact. If the braids get splayed out they can ride on the plastic and not make good contact with the rails. It is helpful to put a little twist in the braids so that they make a shallow V.

 

[RACING LINE]

Your point about breaking the circuit so that the current can only go one way is very important. It can't hurt to twist the braids a little too.

I will report back here with the results for future reference.

 

[beneke]

Greetings,

My ten cents worth of input!
I have two half straights of Sport track in my Classic layout( converter pieces required for the Scaley lapcounter),and experiencied stuttering problems only on this section.

What I discovered is that the braids on the cars sit too far apart to make contact with the slightly narrower and lower rail of the Sport track.I cure the problem every time by pushing each braid sideways closer to the guide blade .

I was totally baffled at first almost pulling out my hair.. trying contact cleaner,new braids, measuring for bad connectons etc.
I just could not understand it until I removed the track piece and looked between the rails and the braids of the car and saw the gremlin.

Hope this helps as stutttering can really drive one crazyl

Best regards
bryan

 

[RACING LINE]

Looks like the stuttering was braid/rail depth related.

Some (but not all) of my recently purchased Sport straights have rails sitting below the black plastic so certain cars were prone to losing connection on these track pieces.

Drift cars were especially bad as the guide plate is particularly wide and the braids are fixed at both ends and do not trail.

Thanks to all those who made suggestions.

 

[beneke]

Hi,
Glad you sorted the problem
I am not a Sport track fan. Classic track rules!, better grip, better contact.Pity they don't make Classic anymore.
SCX classic track provides good grip but the rails are of a much thinner metal than Scaley and therefore bend and warp very easily.I suppose the way to go is Ninco. Will work out very expensive though as it will also mean having to replace the borders as Ninco track sections are not of the same dimensions

Regards
Bryan