chuff rate - BLI Mikado

[altohorn25]

Hi everyone,

Has anyone figured out what CV adjusts the cuff rate for the new BLI Mikado?  I've looked through the manuals and can't find anything.  Thanks in advance.

[jdcolombo]

I haven't tried it yet, but I think this is what you do:

Set CV246 to 64; then use CV220 to adjust the chuff timing.  Take a look at these two CV's in the Paragon 3 Steam Technical Reference Manual available on their web site.

I'm going to try this soon.  My chuffs aren't too terribly mismatched, but I'm looking for improvement before I make a decision to stick a LokSound 5 in the tender.

John C.

[jdcolombo]

I just verified that it works - set CV246 = 64, then play with the setting in CV220.  I found that a value of between 28-32 gave me the best slow-speed chuff match.

Unfortunately, I can't get the chuffs to match well across the speed range.  If I get them near perfect at slow speed (e.g., <25/128), then in the mid and upper range they are way off.  If I get them right at mid-throttle (say, 60/128), then they are off at slow speed.  Since I notice the match more at slow speed than at mid- or high- speed, I've opted to fix it for slow speed, and live with the mis-match at higher speeds.

I suspect that in a few months this will aggravate me enough that I'll pull the Paragon 3 decoder and substitute an ESU 5.  But not today.

John C.

[wazzou]

I tend to think that mis-matched chuffs are much more noticeable at lower speeds than when running at higher speeds anyway, IMO.

[mmagliaro]

Just curious...
Without any sort of timing cam on an axle, how do the chuff rates *ever* really match in these decoders?  Is the decoder relying on back emf to tell the speed of the motor and then compute the chuff rate from that?  Or is it just winging it based on its output voltage to the motor?

[jdcolombo]

Just curious...
Without any sort of timing cam on an axle, how do the chuff rates *ever* really match in these decoders?  Is the decoder relying on back emf to tell the speed of the motor and then compute the chuff rate from that?  Or is it just winging it based on its output voltage to the motor?

Hi Max.

They use BEMF to calculate motor speed and chuff rate.  If you press down on the engine to make it stall, the chuffs stop.  So it's not just a voltage calculation.  But some decoders are better at this than others.  The ESU LokSound has two CV's, 57 and 58 that you set to tell the decoder how to match chuffs.  CV57 is set at speed step 1, and tells the decoder how to calculate chuffs at the minimum motor rotation.  Then you open the throttle to about 1/5, and set CV58 to match chuffs.  This tells the decoder how to calculate chuffs as motor speed increases - essentially telling it about the gearing of the loco.

But the Paragon (and the Econami decoder from Soundtraxx) only use a single CV to do chuff timing.  And they aren't as good.  You can get well-matched chuffs at lower speeds, but then things go haywire at higher speeds.  I'm not exactly sure why this is so.  I would assume driver rotation should be linear through the motor speed range, so that if you match the chuffs correctly at any particular speed, the decoder should be able to properly calculate chuff rate for any other speed.  But apparently that's not the case.  Maybe given all your experience with steam locos and motors you can shed some light on this for me.  All I know is that I can use ESU's system to get near-perfect chuff timing (without a cam) up to the speed at which you can't really observe the chuff timing anymore.  And I can't do that with the Econami or Paragon 3.

John C.

[peteski]

Yes, this BEMF chuff synchronization was what made me fall in love with the QSI Revolution sound decoder factory installed in the Life-Like/Walthers Mallet.  It was amazing.  The other features (such as rod clank and different exhaust volume based on the locos workload) were also very well done. And that was probably 10 years ago now.  Like John, I could press down on the loco to slow it down (or even stop the wheels from spinning) and the chuffs woudl follow suit.

I suspect that they actually don't depend on the BEMF voltage itself, but rather count the voltage spikes or interruptions produced by the commutator (sort of a tachometer for the motor). However they do it, the results are excellent.

[CRL]

Just teach the dog how to speed up or slow down his panting. But watch out for the blow down... really smells bad.

[altohorn25]

I just verified that it works - set CV246 = 64, then play with the setting in CV220.  I found that a value of between 28-32 gave me the best slow-speed chuff match.

Unfortunately, I can't get the chuffs to match well across the speed range.  If I get them near perfect at slow speed (e.g., <25/128), then in the mid and upper range they are way off.  If I get them right at mid-throttle (say, 60/128), then they are off at slow speed.  Since I notice the match more at slow speed than at mid- or high- speed, I've opted to fix it for slow speed, and live with the mis-match at higher speeds.

I suspect that in a few months this will aggravate me enough that I'll pull the Paragon 3 decoder and substitute an ESU 5.  But not today.

John C.

I'll try playing with it tomorrow morning.  As has been stated, I think it bothers me more at the slower speeds than at road speed.  Thanks for the help everyone.

[Cajonpassfan]

Well, maybe I’m just lucky, but my mike chuff rate is just about perfect out of the box. Of course, I did drop the top speed to 30 mph (CV5=50, CV6=20) so there’s a limited speed range. This is more than adequate for my mountain rr. I also put in very substantial acc/dec momentum (100). The only other adjustment I made was CV196=1, steam cock chuffs which I find more realistic. These settings may not work for everyone, but overall, I’m very pleased with the loco and the decoder so far...

(I also made a bunch of sound adjustments, and I’m still not quite done, but that’s another topic. I wonder whether the Paragon 3 steam decoder tuning deserves its own thread?)

Otto K.