C19 a bit too much slack in the drive

[grippa]

I have a new C19 and have pugged in a QSI Quantum board. I have noticed that the very slow speed is a little jerky. I have set the CVs to allow for the locos motor type etc. But the problem seems to be to do with the slack in the drive chain. There is about 5-10% slack, in that you can rock the loco back and forth about 5-10% of the wheel revolution. If the loco is pushed so that the slack is taken up before any advance is set on the controller, then the slow speed take up is nice and smooth (same with reverse). It looks like the slack is the problem as the QSI board gauges BEMF etc fro the actual motor revolution
My question is....should there be this much slack in the drive chain? If not is there a simple way of tightening it up (I know that there will always be a little 'play' but this does seem excessive).

[Kevin Strong]

Not much you can do about the gearing in the C-19. That's a function of how the teeth in the gear mesh, and without all new gears, that's not going to get tighter. Mine is a bit loose compared to other locos as well, so yours isn't an anomaly. But it's probably one of the smoothest-running locos I have on the roster, too, so I couldn't really classify them as a hindrance to smooth operation.

You could try adjusting the PID values for slow speed a bit. I changed the PID values in the QSI board that's in my 45-tonner, and it made a big difference, though it's still jerky at the very start and stop. I used values which were recommended to me, I haven't a clue what each value is actually adjusting to know which way to "experiment" to get even smoother operation. I tried "playing" once, and no matter what I did it got worse and worse. (And I have yet to meet anyone who can adequately explain it to me, either--even QSI guys are quiet on this when asked on their forum. Open invite for anyone who can--e-mail me!)

But failing that, I'd probably just switch to STC (CV 56.4=0). Despite the "new" PID values with my 45-tonner, STC with even as little as 10% momentum) is still smoother than RTC. No, it won't crawl at a scale 1 mile per hour for miles on end, but it will start and stop very smoothly, and craw at around 3 - 4 miles per hour, which is about as slow as I've ever seen a prototype loco crawl as well. (The 1mph thing is a cool parlor trick, IMO, but no one runs their trains that slowly in normal operation.)

Hope that helps a bit.

Later,

K

[grippa]

Hi Kevin
Many thanks for your input. It is good to know that my loco is as others. I agree about the QSI complexity!
I was wondering about the STC throttle option being the way to go as I have read that RTC does have problems with 'loose' motor/gear setups like locos using Pittmans. Unfortunately I have heavy gradients on my line so the RTC, which incorporates comprehensive BEMF is a useful thing to have whereas STC, although acting in a very linear fashion especially at slow speeds, does not have the benefit of BEMF. I will experiment with that anyway.

I do not want the very very slow speed (I agree that the 'creep' speed is a 'demonstration' attribute) but I do want the acceleration through slow speeds to be smooth.
Are you using a DCC board in your C19
M

[Kevin Strong]

Depending on how steep your grades are, STC will probably work fairly well for you. Comparing the C-19 to my other locos on my 2.5% grade, it is more consistent in terms of maintaining speed. I haven't had a chance to run it on a railroad with 4% or greater grades to see how it performs there. Having said that, with the QSI, you can hit F9, which turns on the "sound of power" feature, which is essentially cruise control. Even in STC, it keeps the speed more-or-less constant. I did a 40-ton center cab for my dad's railroad with a QSI throttle, and with dad's 4% up and down grades, it was pretty steady. It's set to STC. (For the benefit of other readers, the "sound of power" feature on the QSI control--the older Quantum and new Titan--basically locks in the speed at whatever you have it set at, then you can use the speed knob to increase/decrease the volume of the chuff or the revs of the diesel motor. Kinda cool when drifting down 100' of 5% grade. The speed is held constant, but the motor is at idle as you'd hear on the prototype.)

I've got the Aristo Revolution currently in my C-19. I was going to put a QSI board in it, but I've been having too much fun doubleheading it with my scratchbuilt C-19 at train shows, so I think it will keep the Aristo board in it for that.

BTW, have you tried the new Titan, with its prototypical braking feature yet? Boy does that add a new dimension to operations. I've got one in a 45-tonner, and when I get my other one back from QSI (repair), I'll put it in my Climax. That's a kick on my workshop switching layout. Haven't broken a coupler yet, but it's a good thing I'm not shipping eggs. It does take some getting used to.

Later,

K

[grippa]

Hi Kevin
Good to have our input again.
It is good to hear that the 'sound power' or 'heavy load' option with STC still maintains speed, although, unlike RTC, it has to be applied manually via the controller button.

My main incline, due the garden topography having to stay the way it is, ..... is very steep..........in fact over 10%! (there is no way to compensate for this geography without digging a long deep trench or building a trestle that blocks off entry to the lawn). So I have to multiple head to have half decent length trains surmounting the gradient. I have built motorised rolling-stock to act as helpers if I have a consist of less than two three locos etc. I wonder if STC will be able to handle going down that steep a hill as well as RTC could. I have to say here that this is all happening with DC control as DCC is a new option for my main line.

In my dealings with the Quantum Programmer  I am sure that function 5 is the 'sound of power' or 'heavy load'. Function 9 is shut down...but I could easily be wrong...will check.