Best Of The TP56/TP70 Kitbash thread N scale

[mmagliaro]

Glad you had that drawing.   I was thinking side by side and reversed.  Your drawing helps.

So let me make sure I understand what is being argued.

This is a pager motor.
Limited to 6 volts.

But the decoder will send out 12 v pulses just like a throttle-- regardless of what I set Vmin and Vmax.

So adding these will protect the tiny motor better.

And after they are installed, adjust Vmin, Vmax etc.

Right?   

That is exactly right.  I know you made measurements of the current draw on this motor under load in a train.
And as I recall, it was never as high as 80 mA.  Was that right?  If so, then my assumption that 1/2 watt zeners should be fine is correct.

If you are not familiar with zener diodes.. the normal lead style (not surface mount) will be about the size of small 1 amp diodes - smaller than a 1/2 watt resistor, and shorter.  I would look for somewhere they won't touch any plastic to mount them.  Even a 1/2 watt device can get pretty warm if it's pushed hard.

IF YOU HAVE ROOM - by all means, get 1 watt zeners instead of 1/2 watt.  They are still not very big, still smaller than a 1/2 watt resistor.

[Philip H]

Gotta love three spotting phases in three successive locomotives!

[u18b]

That is exactly right.  I know you made measurements of the current draw on this motor under load in a train.
And as I recall, it was never as high as 80 mA.  Was that right?  If so, then my assumption that 1/2 watt zeners should be fine is correct.

If you are not familiar with zener diodes.. the normal lead style (not surface mount) will be about the size of small 1 amp diodes - smaller than a 1/2 watt resistor, and shorter.  I would look for somewhere they won't touch any plastic to mount them.  Even a 1/2 watt device can get pretty warm if it's pushed hard.

IF YOU HAVE ROOM - by all means, get 1 watt zeners instead of 1/2 watt.  They are still not very big, still smaller than a 1/2 watt resistor.

sooooo......

These?

http://www.ebay.com/itm/ZENER-DIODE-Mini-MELF-ZMM5231B-500mW-5-1V-5-DO-213AC-SMD-NEW-25-PKG-/191538165712?hash=item2c989077d0:g:a0IAAOxyuaFSMIpY

[chicken45]

ok, that's it - if you people don't stop doing such fine work, I'm throwing @chicken45 in a vat of Nutella and taking up basket weaving.

Seriously @u18b - thats really fabulous work.  @Ed Kapuscinski - did we mark this Best Of?

Only if it's the European stuff. The Nutella they sell in the states tastes like cardboard sludge compared to its superior European glass jarred hazelnut god.

[peteski]

Seriously @u18b - thats really fabulous work.  @Ed Kapuscinski - did we mark this Best Of?

I second that motion.

The only way this thread could be made better would be if the photos were hosted on TRW.  But I guess Google is a pretty stable photo host (for  now).   

[dcutting]

As the designer of this thing, I can third that motion. Ron's work with my parts has been exquisite.

David

[JanesCustomTrain]

Has this one been sold to India ?   

Jane

[u18b]

The Kato A/C unit has an awfully large mounting nub.



Instead of drilling/cutting a big hole in the roof of the TP70, I trimmed the nub back.
Drilled a hole, and inserted a 10 mil guitar string.




Once glued in place..... I'm done with the construction phase.

Time to move to painting.


 

[up1950s]

I can see starter train sets under Christmas trees . What about B units , or slugs for added pickup . You can make an industry city wing to you layout , where the Main Road drops off and picks up cars in a small yard or siding . The Industry owned railroad " pick a name " , whose only equipment is this TP-56 is charged with shunting the industry and setting up cuts of cars for the Main Road to pickup . Ops that pop ! Probably wouldn't hear the real one from a birds eye view distance , so no sound is the right sound . But if sound could be put in it I would put in a Screaming Goat .

[mmagliaro]

sooooo......

These?

http://www.ebay.com/itm/ZENER-DIODE-Mini-MELF-ZMM5231B-500mW-5-1V-5-DO-213AC-SMD-NEW-25-PKG-/191538165712?hash=item2c989077d0:g:a0IAAOxyuaFSMIpY

Yep, those should work.     I did notice that these have a maximum forward voltage drop of 1.5, not the typical 0.7 of a silicon diode.  What that means is that your maximum will be 12 - 5.1 - 1.5 = 5.4 volts, not 6.   That is probably not a problem at all, as this engine probably runs faster than you want at 5.4 volts anyway.  But if it bothers you, you could go to, say, a 4.7v zener instead of a 5.1.  That would get you 0.4v more at the motor, or 5.8.

By the way, I went back through all 28 pages of this thread, and I cannot find if you measured the current draw of this motor under heavy load  (under stall would be even better).  That's important.  Over 100 mA, that 5.1 zener is going to be hit with 510mW of power and it will burn out.  I'd play it safe and keep the current under 80 mA.  If your motor draws more than that, you'll just have to go with 1-watt zeners.  You can still probably fit them in there.  They are surprisingly small.  Just don't mount them up against anything plastic.

[nkalanaga]

Peteski:  Thank you.  I wasn't thinking about using the speed table to reverse the locomotive, or much of anything at all, just curious.  But today I did think of a possible practical use for a high starting voltage.  Many older motors will run very nicely at lower voltages than it takes to start them.  So, my thought was to set step 1 to maximum voltage, then step 2 to the minimum the motor will run smoothly on.  With a little practice it should be possible to to go from stopped to step 1 and on to step 2 at the right rate for a smooth start, but not a big lurch.

Of course, those who actually USE DCC have probably been doing that for years!

[peteski]

Peteski:  Thank you.  I wasn't thinking about using the speed table to reverse the locomotive, or much of anything at all, just curious.  But today I did think of a possible practical use for a high starting voltage.  Many older motors will run very nicely at lower voltages than it takes to start them.  So, my thought was to set step 1 to maximum voltage, then step 2 to the minimum the motor will run smoothly on.  With a little practice it should be possible to to go from stopped to step 1 and on to step 2 at the right rate for a smooth start, but not a big lurch.

Of course, those who actually USE DCC have probably been doing that for years!

Some decoder already feature a "kickstart" function to do just exactly what you're proposing. No messing around with speed step table. Here is more info: http://www.dccwiki.com/Kick_Start

[u18b]

I made measurements and a drawing of the frame.

My drawing fills in a spot that is not present in my frame (because I pieced mine together).

So if I was going to make another, these are the dimensions I would use.

Holes are 00-90.

[randgust]

Got to run mine a lot at Altoona.
Also talked to the guy that actually runs real one!
Let's just say that the concept appears likely to stop at 3 units.

[dcutting]

Got to run mine a lot at Altoona.
Also talked to the guy that actually runs real one!
Let's just say that the concept appears likely to stop at 3 units.

Thanks Randy for getting some publicity on these. That's interesting to know... too bad it didn't work out.

David