mdt plymoth finally

[mf5117]

I finally got my HO mdt plymoth sante fa #32 back . ok here i go i hope i post this right .

no mods to the chassis . the engine was not dcc ready so the motor had to be insulated . the decoder that was installed was a 1006 tcs m1 decoder .a new wire harness "plug and play . if the decoder goes bad just unplug and put in the new one like the dcc ready locomotives .it is installed inside the body and not the cab like was talked about in the previous thread . this guy does these all the time , like clock work put a sound decoder in a thomas ,more than once , also he put a rotary beacon  in the mdt as well . I was so excited . I got it home and was pushing and pulling 2 40' flats around the layout no problem . he did say they are tuff but it can be done . total cost was $38.00 ,but was well worth it to me . I will use him along with the 70 tonner in the yard moving pulp wood cars and coal cars .

his name is jason at larry's hobbys in houston texas . I also just took a gp 40 I'm having a decoder installed # 5 of the gp 40's now plus a dummy gp-40 #6 so 6 total sante fa's gp-40's                peace to all 

[CNE Runner]

Thanks for the interesting thread. I just bought a Bachmann Plymouth to use on my micro layouts. I haven't done much other than run it back and forth on 6' of straight track. The locomotive runs quietly and well at slow speeds...I'm impressed. My version, being straight from the box, is DC - although the seller said it could be converted to DCC easily (of course 'easily' is a subjective term). I will keep the chap that converted yours in mind should I ever decided to convert mine to DCC. The rotating beacon is a nice touch...adds interest. Check out my thread at:

http://www.bachmanntrains.com/home-usa/board/index.php/topic,10410.0.html

BTW: While Bachmann advertises this little industrial locomotive as an 'MDT Plymouth' it isn't. The MDT model has four wheels whilst the Bachmann version has 6. Plymouth did manufacture a 6-wheel version called [I believe] the WDT. I think our little engines are simply generic industrial locomotives.

Regards,
Ray

I decided to go a'Googling and found an interesting website showing images of various models of engines produced by Plymouth. The 6-wheel versions are of the 'W' class. All MDTs were 4 wheel. Check it out for yourself.

http://www.northeast.railfan.net/diesel81.html

Ray

[jsmvmd]

Dear Ray,

Thanks for the good link.

Best Wishes,

Jack

[Robertj668]

mf5117

Wow for $38 he put it a DCC controller.  That did not include parts or did it? And that is  small engine.

We live in Forth Worth Texas and I go down to Houston about once a month. I may have to go in there now

You mentioned that he put sound in a Thomas as well.  Was it HO.  I have a thomas and want to put in DCC and sound as well but it is a very tight space.

Robert

[mf5117]

yes parts and everything .and was an HO mdt plymoth . they are off I-45 & fm 1960 east ,Larry's Hobby Shop right off the freeway . you can drop it off and pick them up apon completion . He does good work . he installed a plug and play wire harness , I'm at work, but I think I put the decoder info on the thread , insolated the motor can . I'm also having a gp40 done as well . 

[Robertj668]

Wow for that price it's worth it!  I will keep him in mind.

Thanks

Robert

[santafe]

I have the same loco and it runs great!  You can run DC engines with DCC, you just won't have as many features.  If I were you, I'd take out the decoder and insulator and just run DC for that loco.

[CNE Runner]

Santafe, I have the same little switcher as mf5117 and can attest to the fact that the Bachmann Plymouth WDT is a very, very small locomotive. It is amazing that room was found for a DCC decoder! The installer must be a neurosurgeon.

You mention that one can run a DC equipped engine on DCC? I thought a DCC controller provided full power to the rails - relying on the decoder to 'step it down'. I was under the impression that one needed a dual mode decoder to run an engine on both DC or DCC. Are you sure about this? Jim B...any thoughts?

Ray

[BestSnowman]

I think at one time Bachmann did manufacture a four wheel version. My local hobby lobby has one in the locomotive case and it looks like its only a four-wheeler so its possible Bachmann originally made an MDT but switched to the six-wheeler and never updated the name.

The one at my local hobby lobby has dropped from 50 on clearance to only 15. I might have to think about picking it up one of these days.

[Jim Banner]

Ray,
Some DCC systems let you run one analogue locomotive(dc, no decoder).  Most of those systems do this on address 0.  Bachmann's E-Z Command does it on address 10.  You are absolutely correct that DCC puts a constant ac voltage on the rails.  And in decoders, it is converted into dc and then fed to the motor.  But the constant voltage on the tracks is rectangular waves, not sine waves such as come out of your wall outlet.  That is to say, the voltage goes up to 14 volts, stays there for a little while, then reverses, going down to -14 volts, stays there for a little while, then reverses ...  If the length of time that it is positive is the same as the length of time that it is negative, then there is no dc on the rails and a dc locomotive on them will sit still.  However, if the time spent at the positive voltage is longer than the time spent at the negative voltage, then there is a measurable dc voltage on the rails.  The ac voltage has not changed, just the ratio between positive and negative half cycles.  A dc locomotive on the tracks will move because it is receiving that dc voltage.  As we make the positive half cycles longer and longer compared to the negative ones, then the locomotive will go faster and faster.  And what about reverse?  If we lengthen out the time that the voltage stays negative, then the locomotive will go faster in reverse.  This is called zero stretching, for reasons that will become obvious.  If talking about there being a dc voltage present is confusing, we can look at this a different way.  When the voltage is momentarily positive, then the locomotive can take a step forward.  Then when it is negative, the locomotive can take a step backward.  If the forward and backward steps are equal, the locomotive stays in the same place (and make that annoying frying or singing noise.)  But if the positives are longer than the negatives, the locomotive can make two steps forward, one step back, and slowly move along the track.  Making the positives much long and the locomotive can do more than 100 steps forward, one step back, and really boogy along the track. 

Now as it happens, the DCC signal on the tracks is also sending information to all the decoders.  It does this in the form of zeros and ones.  The ones are faster, skinnier pulses than the zeros.  So you cannot lengthen the ones because they might be mistaken for zeros.  But you can lengthen or stretch the zeros without them being mistaken for ones.  Figure 3  shows the difference.  A one has to be a cycle (a + pulse together with a - pulse) that is 100 microseconds or less.  A zero has to be a cycle that is longer than 180 microseconds and can be up to 12,000 microseconds long.  For a one cycle, the + and - halves are normally equal.  But the halves of the zero pulse can be greatly different.  Because we stretch only the zero pulses, the process is called zero stretching.



Figure 4 shows that no matter what you do to the length of the pulses, their heights are the same.  Even more important for the decoder, the dc that results from rectifying these pulses stays the same.  So there you have it - the DCC signal on your tracks can do three things - carry power to decoders at a constant level, carry digital signals to decoders to tell them what to do, and provide a changeable dc voltage to dc locomotives to allow their operation without interfering with the operation of DCC equipment on the tracks.

Although usually stated that you can run one dc analogue locomotive with brand X command system, you are limited to one only in the sense that a conventional dc power pack limits you to one locomotive.  In fact, you can run several dc locomotives at the same time with either a DCC system that allows dc operation just as you can run several locomotives at once on a single dc power pack.  So go ahead, double, triple or quadruple head a train with dc locomotives, as long as your DCC system can supply the power.

One note of caution:  running dc locomotives on DCC can cause them to heat up.  This is particularly true of old, current hog locomotives with old open frame motors.  Modern, high efficiency can motors normally do not have a problem (other than being noisy) on DCC, but check their temperature anyway, particularly after sitting idle on a DCC powered track for 10 minutes or more.  Having said that, I will add that in close to 20 years involvement with DCC, I have only seen one can motor that I knew was good go up in smoke from sitting idle on a DCC track.  And that was in a large scale hand car with a small motor (for the scale) running on full large scale voltage.

Jim

Jim

[CNE Runner]

Jim, thanks for the explanation...gives me warm memories of my physics teaching days. If I read into your post, you are saying that DC is possible on a DCC system - but motor damage (overheating) is possible and probably not recommended. Both of the micro layouts, I am building/have built, run on DC. Reason? The Bachmann Plymouth WDT - I use - is DC only and DC power packs are readily available on the used market. Again, thanks for taking the time to explain the physics.

Bestsnowman - I wasn't aware that Bachmann produced a 4-wheeled Plymouth (MDT or one of its other kin). I know Athearn (and currently Model Power) produced a generic GE 25-tonner. Penn Line produced a little Davenport kit a long time ago as well. I'd like to see someone produce a series of these interesting little locomotives: Plymouth, GE, Mack, Whitcomb, et. al.

I thought you would enjoy this image of a GE 25-tonner...neat little engine.

Ray