Speaking of DC...

[strummer]

I have what I think is a nice little selection of DC power; a couple of Troller "Autopulse" units, an MRC "Controlmaster Vl" and the Heathkit RP 1045.

The MRC is a very nice unit; it works well with everything I have.

The Troller units are good; I do find the pulse to be a bit "harsh", so I use those rather sparingly.

The Heathkit is just phenomenal; it runs everything beautifully, regardless of scale; except...

I recently picked up a "OO" Hornby 4-6-2, just for a bit of variety; it has what I guess is a fairly typical "vertical pancake" (they call it a "Ringfield") 3 pole motor in the tender. It runs "ok"; only as well as one would expect. But the thing is, it runs MUCH better off the MRC unit, as opposed to the Heathkit, and certainly better than the Trollers.

I think it hates the Trollers due to that harsh pulse, so I get that. But again, the Heathkit makes everything else I have run so much better...except this Hornby.

Any theories as to why this is so?

Mark in Oregon

[peteski]

Does that motor use permanent magnets, or is the magnetic field generated by a field coil (wired in series with the rotor)?

I'm also not familiar with the RP1045 technical details.

Is the slow speed a problem?  Top speed different? Or just overall operation? Can you describe exactly how the motor behaves when operated by the Heathkit throttle as compared to the others?

[strummer]

Hello Peteski. I thought you'd be the first to chime in; thanks!

As far as I can tell, it is a permanent magnet design; there is no field coil, as in a Marklin or Lionel loco.

I won't include the "Troller" units here; as I say, the pulse is just too harsh, and this loco responds to them with jerky movements and a slight "buzz".

I would say the over all speed range is pretty much the same, regardless of which power pack I use. The initial start-up speed is a bit high; (it reminds me of 1970s vintage N scale!). I'm guessing that probably comes from being a 3-pole motor(?) It takes about 6 volts before it starts to move. I can't comment on the "top speed", as I never go that high. It just seems more "in tune" (responsive) to the MRC unit...

Does any of that help? 

Mark in Oregon

PS: I should probably add here that I've checked some Hornby and other British forums, and the over-all performance of this example seems more or less in line with what one would expect from this model; I'm mostly curious as to the "harmony" between the MRC unit and this loco.

[peteski]

So the poor performance seems to be more perceived than anything specific (other than higher starting voltage)?

I don't have a specific answers, but as I see it, it could be several possibilities.  Maybe the motor's impedance is markedly different than other motors which shifts the minimum starting voltage. Or its magnets are weaker, again requiring stronger magnetic field at the rotor to start it.  Or the mechanism has more friction than others, needing a higher starting voltage and apparent sluggishness?

 I also do not subscribe to the opinion that 3-pole motors are universally "crappy".  There are 3-pole motors out there (especially with skew-wound armatures) which are "smooth" and have low starting voltage and plenty of torque.

[strummer]

You do as usual, make some very valid observations. Thanks. Question: can a motor of this type of design have a skew-wound armature?

As I mentioned, this motor has a reputation for rather marginal performance. I understand there is a 5-pole replacement kit available; since it is a "drop in" type, maybe I'll try one of those sometime, if I get the urge.

I'm hoping Max will see this topic, and put in his two cents, too. After I purchased my Heathkit, I contacted him to get his opinion: I remembered that he had mentioned at one time owning one. He had a very high regard for it...

Mark in Oregon

[peteski]

Hmm... I guess I didn't have a full picture in my mind of what this motor looks like.  Now I do:



Yes, the armature is too shallow to skew it, There is also a large distance between the poles (on the outside diameter of the armature.  I don't have any experience with that motor but I would say that due to its design, it will be rather "coggy" (if that is even a word). It likely isn't very efficient either.

[strummer]

..."coggy"...yes, I think that a good description.

Peteski, I will let you know if I ever do the 5-pole conversion; in the meantime, I guess we should let the good people of "Railwire" get back to the interesting topics at hand...

Mark in Oregon

[mmagliaro]

Here's my "chime in".  The Heathkit throttle is essentially a Linn Westcott TAT V.

It has a pulse generator that lets you set the pulse width and frequency, and as such, it is about the most versatile pulse power there is, except that you cannot control the pulse SHAPE.  I think that's going to be the big factor here.  More on that later.

The Heathkit also lets you set the starting voltage (so that the throttle pot can be used over its entire range without having to, say, turn it up halfway before the engine starts to move.  It also uses what Heathkit called an "AC Compensation" circuit to adjust the track voltage in response to motor speed fluctuations.  My experiences with it tell me that whatever it is, it's not a back EMF detection circuit, because it never seemed to make huge differences in the uniform motion of motors at lower speeds.  But it did help even out the speed.

So one would think this thing could make a motor run better than the MRC.  I suspect the key is the pulse shape.  It could be that one of these throttles is using a square wave vs clipped sine half waves.

Does the MRC do a better job on this loco at the expense of a lot more noise or heat?

[mmagliaro]

And shouldn't this be in the DCC/Electronics forum?

[strummer]

Thank you Max, for that wonderful "chime in".   

No, like I say, this (I think rather crude) 3 pole motor just seems to respond better to the MRC unit. I do not know if it (the MRC) always has the pulse going at lower speeds, or not. All I know is I can get the LMS loco to run slowly with the Troller units (but it then has a slight "buzz") and with the Heathkit it will run "ok", but it just runs smoother (and quieter) over all with the MRC "ControlMaster".

I know my observations are strictly that: "observations", and you fellows like data, but that's all I can give you. Not that any of this matters: I was merely curious... 

Thanks.

Mark in Oregon

[mmagliaro]

Thank you Max, for that wonderful "chime in".   

No, like I say, this (I think rather crude) 3 pole motor just seems to respond better to the MRC unit. I do not know if it (the MRC) always has the pulse going at lower speeds, or not. All I know is I can get the LMS loco to run slowly with the Troller units (but it then has a slight "buzz") and with the Heathkit it will run "ok", but it just runs smoother (and quieter) over all with the MRC "ControlMaster".

I know my observations are strictly that: "observations", and you fellows like data, but that's all I can give you. Not that any of this matters: I was merely curious... 

Thanks.

Mark in Oregon

Hmmmm... I bet you have already tried this, but did you experiment with varying the pulse width and frequency on the Heathkit to see what settings give you the best performance?