K 27

[ironlake]

To run standard dc to track how much voltage will be required for the k 27 and how much current capacity.  Will a lionel transformer with a bridge rectifier and filter cap be workable, or will I need a special unit.  Hope you guys are not getting tired of my questions.  again thanks in advance

[Chuck N]

You will want between 10 and 18 volts.  The engine will draw about 1 amp.  Long trains, tight curves and grades will increase the amps.  Adding sound, smoke units and lighted cars quickly increase the power needed.

Most of us have and recommend power supplies that have minimum of up to 20 volts and 10 amps. 

Your Lionel transformer with a bridge rectifier should work, depending upon the power out put of the Lionel unit.  Their larger units should be OK, but if you have a smaller (starter) unit you will probably need to start over.

You would probably be better off to get a DC unit with power to spare.

Chuck

[armorsmith]

Ironlake,

The K27 is a DC motor, most Lionel 3 rail stuff is AC.  Not compatible.  You can run the K27 on an AristoCraft model ART-5400.  They can be picked up on eBay for a reasonable price.  The K27 has a Pittman can motor rated for 19 volts.  Most DC motors will tolerate higher voltages for short periods of time.  The K27 is geared a bit on the high side for most people, myself included.  The K27 running at a prototype speed of around 25 scale MPH will be at about 14.0 volts and pulling a train of 15-20 cars on a 1.5% grade I have not seen above 1.7 amps, this is on a permanent outdoor layout (you can see a Google Earth view on our home page at www.ecgrc.com).  Overall I am very pleased with mine.

Hope this helps.

Bob C.

[Chuck N]

Bob C:

Adding a bridge rectifier will convert the AC to DC.  My dad and I used a Lionel Transformer with a Bridge Rectifier for many years on an HO layout.  I have no idea what the effect of the rectifier has on the voltage and amp output.  It will work, but I don't know how well!  Which is why I suggested that he get a DC power supply.

Chuck

[ironlake]

I would be using an old model Z with 25 volts and 15 amps of current.  I would just make a little box with a 15 amp bridge.  Do I need a capacitor to get smooth dc or is pullsating dc ok?

[ironlake]

Pulsating dc is rectiied dc with 60 cycle ripple on top of the dc line as seen on an ocilliscope.  The cap will filter out the ripple as long as the cap is large enough so it is always charging under load.  Is the same as a battery load  and is called filered dc.

[armorsmith]

@Chuck N

Sorry for the delay in a response, and yea I do realize that.  I missed that he was going to use a rectifier with the Lionel power pack.  I believe he stated that he was getting 25 VAC, which rectified would be approximately 17.7 volts DC.

@Ironlake

I would definitely use a filter capacitor.  I am not sure, but I would suspect that the electronics board in the tender of the K27 would not be very appreciative of stray spikes of voltage running around.  If we were running the old days back in the '70s, before all the high tech electronics, I would think you would be OK, but I personally would not do what you are thinking.

I understand being a bit cash strapped (if that is the case), but a better quality unit will be well worth the wait.  It took me two years to finally purchase a quality Meanwell 24VDC switching power supply and a 27MHz TE used from a fellow club member.

My tuppence worth.

Bob C.

[ironlake]

All diodes that I know of that are silicon have a 7/10 of a volt drop to turn on.  When the + cycle goes through your loose 7/10 and when the - pulse goes through another 7/10 is lost.  The total loss is 1.4 volts or 25 volts - 1.4 volts = 23.6 volts which is good enough.   Put on a 5000 uf 35 volt electrolitic and it will jump back up to 25 or more.  This  is what I use on my ho layout all the time and my scope shows me a pure straight line unless I get a fantastic load some ripple will show.