TMCC conversion:Trying to make it somthing it's not?

Buy Legacy engines or new Vision line.

Is the Mohawk an AC motor?  Those aren't as responsive as the can motors.  You should also set the stall speed with them to get better throttle response.

I've converted a bunch of stuff to TMCC and PS/2 without those kinds of issues, so it's possible.  Maybe your "professional" isn't as professional as you might think.

 Sounds like your engine is 100 speed step mode. Stall only works in 32 speed step. If and when you get it running setting the stall it should start moving at the first speed step. We are about fifty miles west of Cleveland in Norwalk. If you still have problems, bring it out to us.

Bill

John...here is the exact engine.I have had it new in the box since 1990.thnx.http://www.ebay.com/itm/LIONEL-4-8-2-MOHAWK-L-3-CLASS-LOCO-NEW-YORK-CENTRAL-O-gauge-RAILSOUNDS-6-18009-/160973829908?pt=Model_RR_Trains&hash=item257ac9b714

It is the AC motored unit, that's what it sounded like.  What TMCC package did they use?  The ERR one would be the AC Commander, that's the only thing they have for AC motors.

That engine does have an AC pulmore. John called it. They not very responsive.

Had the engine a DC motor you could have approached Legacy performance with an ERR cruise commander. Don't let the experience with this engine put you off from future upgrades. Just stick with DC motored engines.

Pete

Even with an AC motor your Mowhank should be way more responsive than what your discribing.

Scott

Is it possible that Frank Timko could do a DC can motor that would work with this locomotive? It depends on whether he can install the existing worm gear on one of his motors and match the motor to the mounting.  

Frank Timko does have a variety of conversions he offers, best to just ask him for specifics on the situation.

AC motors are fine and much more responsive than described and some have derided.  It sounds like it isn't programmed correctly, or, you have the wrong board?  How did she run preconversion?

Well, I wouldn't say derided.  While I'll agree his case sounds extreme, an AC motored locomotive will never match a can motor for low speed handling.  With any AC motored standard TMCC locomotive with standard Lionel TMCC, you have to get to speed step 8 or so before you get any movement as a rule.  That's why I mentioned setting the stall speed, that's very useful for AC motored stuff.

As John said, a AC motored engine will not run slow and smooth as a can motor. If your engine are starting around speed 8, I would set the stall. My 2028 pullmor's and my

integral motor trucks start at the first or second speed. I just wish they had cruise.

Bill

Bill, I was mulling over the idea of powering the field of an AC motor with a constant current circuit and wiring it to the ERR Cruise Commander like a DC motor and seeing how it operated.  I'm pretty sure you'd need the field having a constant source of magnetism for the back-EMF sensing to work properly.  It would be an interesting experiment...

I'd like to see how you get an AC motored engine to start on the first TMCC speed step without setting the stall, I've never seen one that would.

If I am not mistaken Jon Z tried something similar. The required current draw (>5 amps??) made it impractical. As for a Timko replacement, I am pretty sure he has them in stock. I think they are designed as a drop in replacement.

Pete

Pete, I suspect you're right.   I was thinking about the current required for the field, and I wasn't sure I could get enough magnetism without excessive current.

TPC's can get an open frame motor to run very well at very low speeds.  I suspect that the modified wave form the TPC uses has a lot to do with this.

I don't know if there is any way to shrink the TPC electronics down to a board that would fit in a loco.

I can't imagine why the ACDR doesn't do a similar thing, it uses triacs just as the TPC, right?

TPC an use 72 or 200 or 400 speed steps.  I suspect that the core technology of pulsed power is the same.  Difference seems to be in the the way it's applied.  

I had a PWC Texas Special that could creep around the track under conventional control with the TPC.  It was terrible under CAB-1 command control.  It behaved better with Legacy using TMCC commands (aka absolute speed step) but it couldn't match the performance using the TPC.  I suspect that the the TPC spikes were well over the 18 volts that the PowerHouse puts out and that may be why the motor performed better with the TPC than under direct TMCC.

Hmm...  I hope the spikes aren't well over 18 volts, that would be a problem for many electronic package.

Pete, John, I have an AC cruise on a loco in my shop, been there for 5 years.  The problem is that the back-EMF is too low at slow speeds and you cannot get good slow speed operation as a result.  Medium speed, high speed, works great.  I used a switching power supply for the field, and you need to turn off the field when not moving or you overheat the motor.   idid that from the firmware in the Cruise Commander, which was not modified in any way other than putting out a control signal for the shutdown of the switching supply.

I could not see a way to make a product from the results, the slow speed was not great, and that was why you want the cruise in the first place.

Under my direction at Lionel, we added a Legacy encoder on the Pullmor.  We had decent success with that approach.  We never decided to implement this on a product however.

Jon, I just guessed on the field current. Do you change the field current with load or is it fixed? If fixed how much is required to drive the field? Just curious.

Pete

Interesting, I wondered how this would work out.  I figured it must have been considered.

Maybe you could put out that signal on the unused RS interface logic pin and we could do some tinkering.

Did you ever determine why the back-EMF was so different than a can motor?  Is the effective strength of the permanent magnet really that much greater than driving the field with DC?

I did not mess with the field current directly, tried various voltages with very little improvement in operation.  If I pushed the voltage too high, the motor warmed up quickly!  I think I had about 3.0 v on the field before it started to get fairly warm; and higher voltages did not seem to get me more backEMF at the slow speeds - but just warmed up the motor.  I did not vary the voltage on the fly, I just concentrated at slow speed operation.  Since that failed to perform, I stopped tinkering.

My guess on the back-EMF being lower on the AC motor was the gap between the armature and the frame(field electromagent).  But it could have been winding turns, never looked deeper because as a retrofit, I was stuck with the motors already in the market.  

Good point about working with existing motors.  The gap is quite a bit wider on the AC motor, that certainly could account for it.  If the gap is twice as wide, you'd only be getting w/4 the back-EMF.

I'd like to see how you get an AC motored engine to start on the first TMCC speed step without setting the stall, I've never seen one that would.  

John

  I said if your engines are starting at speed step 8, you should set the stall. When you have them start at speed step 1, they are very easy to lashup I mean MU

Bill

I realize that Bill, but I don't recall an AC motored locomotive that started to move before about 5-6 at the earliest, and usually that's a pretty anemic move.  Once they get rolling, you have no problem with pulling power, but they just need a "kick in the pants" to get moving at all.

Jon,

I think you should speak with Ernie when you're at April's York next month about his pullmor Santa Fe F3's that have cruise installed in them. Your eyes will pop out of your socket when you see how slow they can creep!! Don't know what the toy train madman did but wow!!! He did say it is almost impossible to put cruise into a steam engine as there is no room to mount the cruise function.

Rockstar,

I converted a 1990 mohawk to command control and it does much smoother with TMCC than with just plain conventional. I used a digital dynamics TMCC board from back then and setting the stall dramatically improves the start up.

Ted, I wonder if some board designs work better with AC motors than others.  So far, I've only used the Lionel, ERR AC Commander, and the AC version of the TAS UCUB.  I know that DD had AC stuff, but I never had occasion to install one of those.  Of those choices, the AC commander seemed to do the best for me.

The question still stands.  How did it run prior to the conversion?  Have you tried setting the stall function?

I will be using the AC commander for my next upgrade of the Scale Chessie T-1 from the late 80's or early 90's. As for how those pullmor engines operated in conventional, they are pullmor motors which did not have the slow start up speed capabilties if you are just using a regular transformer.  But... if you use a cab-1 or a cab-2 with a TPC, that is another story as the TPC has different speed steps available and you can really creep start a pullmor motored engine.

Best bet is to upgrade those older engines to TMCC as most of use TMCC and/or Legacy or use DCS.

Thanks to all of you that responded.The hobby shop made it right for me.I have learned ALOT about conversions from you.I will do another soon.Thank you!Nick

You need to adjust your stall speed (the manual will tell you how).  Then your locomotive will start up right when you move the throttle instead of after you've spun the wheel around a bunch of times.

Get locomotive moving down the tracks at a fairly slow speed.

• Press the SET key, the headlight will start blinking.
• Slowly turn down the throttle until the locomotive just stops.
• Press the SET key again, the stall speed is now set.

Whenever you start that locomotive, it'll start at the point where you set the stall speed, not zero volts.

"the stall speed is NOW set."