Capt.Brigg Randy, let's be complete with your information.
Randy, let's be complete with your information.
Rich
Alton Junction
rrinkerThat's why reverse loops are so easy with DCC - you can change the 'polarity' of the DCC track power under a moving loco and it won't miss a beat, and continue on in the same physical direction.
Randy, let's be complete with your information. With DCC you do have to have an electrical gap at each end of the reversing loop to prevent a short, and if an engine crosses that gap without some sort of electronic polarity reversal component, the engine can cause a short circuit at the command station.
Thank you all for following this thread and my journey of re-discovery.Capt. Brigg; CEO Pacific Cascade Railway in HO gauge.
Darn magnets....
I think it was explained well above, but the polarity on the rails is meaningless for DCC. Say you had the red wire on the righ rail, and the black wire on the left rail. Flip the direction switch one way on the DC power pack and turn it on. The loco will move one direction. Touch NOTHING else, but move the red wire to the LEFT rail and the balc wire to the RIGHT rail - the loco will run the other direction. Now repeat with DCC instead of a DC power pack (and a decoder in the loco). No matter which rail you connect the red wire to and which you connect the black wire to, the loco always moves the same way as long as you don't touch the direction switch on the throttle.
That's why reverse loops are so easy with DCC - you can change the 'polarity' of the DCC track power under a moving loco and it won't miss a beat, and continue on in the same physical direction.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
The final solution is at hand.
This afternoon I solved the puzzle of why my 40 year old PCRy engine motor turned counter-clockwise while all the other Athearn motors turned clockwise, with the same polarity DC power applied to the motors. Somewhere back in forgotten time, I took the motor apart and then reassembled it with the center magnet reversed. So, today I again took it apart, turned the tubular magnet, reassembled it and it now turns clockwise like it is suppose to do.
When dissembling the engine you will need to twist the weights to pry them off the ends of the motor shaft. Other than that be very careful when you take the brass straps off the top and bottom or you will loose the small spring and brushes under each one.Capt. Brigg; A little smarter today.
zstripeWayne, Don't have a clue as to what happened to My post above..it also timed out....
Not a problem, Frank.
All I know is that when I re-trucked my four Athearn switchers, I didn't pay attention to which truck went on which end, with the result that two ran in the opposite direction of the other two, and opposite to all of my other locomotives, too. Of course, I run DC, so am not all that familiar with the niceties of DCC, although I've heard that it makes wiring simpler.
Wayne
DoughlessBut the controller doesn't know which way the loco is pointed.
The DCC controller does not need to know which way the engine is pointed, it just knows if the engine should go forward or backward, at your command from the throttle. The engineer (you), need to know which way the engine is pointed.Capt. Brigg
woodoneThe trucks will NOT make any difference. The wiring on the motor would..
Ok thanks. I get it. I was thinking of a standard PC Board without the decoder.
- Douglas
Capt.Brigg From one old guy to several others, I will share with you that while Direct Current (DC) has track polarity, Digital Command Control (DCC) does not. DCC is essentially Alternating Current (AC) with a control signal on the power. The decoder then converts the AC to DC and sends it to the motor with the polarity set depending on which way the controller is telling it to go. There is no + or - on the rails and the wheels or trucks or truck towers do not see a polarity and can point in any direction with no change to the DCC controller or the power to the motor. Capt. Brigg, CEO Pacific Cascade Railway in HO gauge.
From one old guy to several others, I will share with you that while Direct Current (DC) has track polarity, Digital Command Control (DCC) does not. DCC is essentially Alternating Current (AC) with a control signal on the power. The decoder then converts the AC to DC and sends it to the motor with the polarity set depending on which way the controller is telling it to go. There is no + or - on the rails and the wheels or trucks or truck towers do not see a polarity and can point in any direction with no change to the DCC controller or the power to the motor.
Capt. Brigg, CEO Pacific Cascade Railway in HO gauge.
But the controller doesn't know which way the loco is pointed.
If you install a decoder that's set at factory default, and reverse the motor leads or install the truck leads opposite of how you install them in another loco, it will in fact run backwards relative to the other loco, right?
Frank, that is a great link. Very informative tutorial.
What is the difference between this type of DC motor and a "can" motor"?
In case anyone would care to read about how a DC motor like We are using in our engines whether it be DC/DCC.....Athearn and all the others I have experienced follow the Right Hand Rule when it comes to wiring the N & S poles of a DC motor:
http://web.mit.edu/cmse/educational/motor_lp_kristy.pdf
I actually built one similar to the above, way back in the 50's when going to school. They also had cheap kits back then to make Your own DC motor. I'm sure Randy has played with one at one time or another.
Take Care!
Frank
Capt.Brigg Going on an earlier suggestion that the internal motor magnets may have been reversed, and wondering if 40 years ago I may have disassembled the motor and reassembled it in reverse and then forgot; after Thanksgiving I am going to disassemble the motor (again?) and see if I can identify how it could be reassembled in the proper direction. I did buy this engine new, so if someone changed the motor, it must have been me. Stay tuned for the results of my little learning exploration.
Going on an earlier suggestion that the internal motor magnets may have been reversed, and wondering if 40 years ago I may have disassembled the motor and reassembled it in reverse and then forgot; after Thanksgiving I am going to disassemble the motor (again?) and see if I can identify how it could be reassembled in the proper direction. I did buy this engine new, so if someone changed the motor, it must have been me. Stay tuned for the results of my little learning exploration.
Capt.BriggGoing on an earlier suggestion that the internal motor magnets may have been reversed, and wondering if 40 years ago I may have disassembled the motor and reassembled it in reverse and then forgot; after Thanksgiving I am going to disassemble the motor (again?) and see if I can identify how it could be reassembled in the proper direction. I did buy this engine new, so if someone changed the motor, it must have been me. Stay tuned for the results of my little learning exploration.
It could have been a what we call a Monday morning motor or a Friday afternoon motor, all the way from the factory.
Yes the lights could be directionally changed using a CV in the decoder to match the engine direction, but that is just putting a patch on a sore, and not healing the wound. I want the coding in all the engines to start out the same. Capt. Brigg, CEO Pacific Cascade Railway in HO gauge.
I get it now. Thanks
Henry
COB Potomac & Northern
Shenandoah Valley
BigDaddy Doughless IIRC, Athearn BB locos could run backwards if the front and rear trucks were switched. So if the wiring looks the same from the top, maybe the leads of one loco is getting current opposite of the other because the trucks have been installed on the wrong ends. So if I took my DCC loco that is running forwards picked it up and spun it 180 degrees and put it back on the track, it would run backwards?
Doughless IIRC, Athearn BB locos could run backwards if the front and rear trucks were switched. So if the wiring looks the same from the top, maybe the leads of one loco is getting current opposite of the other because the trucks have been installed on the wrong ends.
So if I took my DCC loco that is running forwards picked it up and spun it 180 degrees and put it back on the track, it would run backwards?
What I'm saying is that the tall metal truck tower conducts current from one side of the truck, either + or - depending upon how its installed in the loco. The other side of the truck conducts the opposite current to the frame. If you switch the front truck to the back and the back truck to the front, the loco will run in the opposite direction then it did before you switched them. It happens sometimes when you remove the trucks to hard wire them, or take them apart to clean them, tune them up, etc. They can get reinstalled opposite if you dont pay attention.
So if the wiring looks the same on both locos (especially the color wires going to the motor leads), then maybe the trucks are switched on one loco relative to the other.
But if the motors themselves spin in opposite directions when powered only by wires, then its not obvioulsy the trucks. Either the magnets are reversed or the motor is upside down.
I suppose you could set the CV to reverse polarity to the motor, but that's sort of solving the problem without knowing what the problem really is.
Wayne,
Don't have a clue as to what happened to My post above..it also timed out.
A couple of pic's of the two I had. Did not come with fly-wheels in 1966:
doctorwayne Wayne, If You look at the OP's pic's of the two engines......the top metal plates that are on the right side of the truck and cannot be removed and pick-up positive.....if the front/rear trucks were reversed.....the metal plates would be on the opposite side of the truck. That means that the left side of the truck which gets its pick-up from the frame would now be getting negative from the right rail moving forward. That is assuming that the BUS is wired with the top rail positive looking at the track in a horizontal plane......which btw, is the way I was taught how to wire the track in 1950. Looking at the track in a horizontal plane...top rail was N for positive and S for negative. Like a compass, which never changes. I still wire all My track the same way. I had a couple Athearn engines..two SDP 40's/45 that had the same motor as the OP's that I got in 1966......and they ran right rail pick-up positive front plated side of truck and negative from truck bolster on frame. I sent them to My friend in the UK 4 months ago. The instructions had a 1966 date on them. I would just reverse the motor leads and be done with it.........and throw the decoder away....LOL DC die-hard..... Take Care! Frank Doughless IIRC, Athearn BB locos could run backwards if the front and rear trucks were switched. ... As far as I'm concerned, Douglas has answered your question. When I bought Athearn's newer style Flexicoil switcher trucks with the plastic sideframes to replace the old older ones that had cast metal sideframes (I'd already replaced those with cast metal Flexicoil sideframes from Juneco, but the detail on the new plastic ones was too good to ignore), I was initially surprised to learn that there were different part numbers for the front and rear trucks. If you think about, though, one truck is always running forward or backward, while the other is running backward or forward, respectively. Switching the trucks from end-to-end in the frame will solve the problem. Wayne
If You look at the OP's pic's of the two engines......the top metal plates that are on the right side of the truck and cannot be removed and pick-up positive.....if the front/rear trucks were reversed.....the metal plates would be on the opposite side of the truck. That means that the left side of the truck which gets its pick-up from the frame would now be getting negative from the right rail moving forward. That is assuming that the BUS is wired with the top rail positive looking at the track in a horizontal plane......which btw, is the way I was taught how to wire the track in 1950. Looking at the track in a horizontal plane...top rail was N for positive and S for negative. Like a compass, which never changes. I still wire all My track the same way.
I had a couple Athearn engines..two SDP 40's/45 that had the same motor as the OP's that I got in 1966......and they ran right rail pick-up positive front plated side of truck and negative from truck bolster on frame. I sent them to My friend in the UK 4 months ago. The instructions had a 1966 date on them.
I would just reverse the motor leads and be done with it.........and throw the decoder away....LOL DC die-hard.....
Doughless IIRC, Athearn BB locos could run backwards if the front and rear trucks were switched. ...
IIRC, Athearn BB locos could run backwards if the front and rear trucks were switched. ...
Capt.Brigg The reason I don't leave one of the engines running in reverse of what it should, is that the headlight and rear light don't match the running direction.
The reason I don't leave one of the engines running in reverse of what it should, is that the headlight and rear light don't match the running direction.
Well...I have to admit I haven't used NCE decoders, but unless this is a very old (like 1990's - early 2000's) decoder, you should be able to set the lights however you want by changing the CVs that control the lights. Not sure why one would want to do this, but as an example, if you wanted the rear headlight of an engine to be on when the engine was going forward, and the front headlight on when the engine is backing up, you can do that. Remember, some railroads ran diesels short hood forward, and some ran them long hood forward, so decoders are designed to let you pick which is the 'front'.
Or you could just set the CVs so both headlights turn on when you press F0....
Though it's now an academic issue, I think turning the motor over would be VERY difficult. The black end plates are very different top to bottom with the housing for the plastic mounting pins only on the bottom. The electrical brush assembly is also part of the plastic end plates. Also if you just rotate the metal center housing I don't see how that would reverse the spin of the armature. I admit I have never taken an Athearn motor completely apart, but why would you? If someone out there has actually taken a motor apart and had it reverse, please speak up and tell us how you did it, with pictures.Capt. Brigg; CEO Pacific Cascade Railway in HO gauge
BMMECNYCI know that that someone is incorrect, or at least partially. CV 29 does automatically swap the lights. But if direction of travel is wrong for the lights, it will swap the lights when you change NDOT. Lights will still be wrong.
You can say it was me, BMMECNYC. My statement was made with the front headlights being on in the forward position. When the locomotive is flipped 180 degrees, it would still be the same. Sorry if that wasn't clear.
BMMECNYCSwapping motor leads is easier, and less confusing later.
I agree with you wholeheartedly about that. While I do think it would be quicker changing CVs to change the direction of the lighting, I like to swap motor wires to make CVs consistent between all my decoders.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
That's true only for DC......the OP is running DCC....
rrinker Well now it COULD have been simply that the motor in the backwards unit was installed upside down. Sans the clips, the 'top' and 'bottom' of the Athearn motors is exactly the same - so if in a previous life the motor had been fully removed, the mounts pulled off, etc - and then put back together upside down, the commutator would still be on the right end, but the motor would be flipped in polarity. That's even more likely than the magnets having been put in backwards. --Randy
Well now it COULD have been simply that the motor in the backwards unit was installed upside down. Sans the clips, the 'top' and 'bottom' of the Athearn motors is exactly the same - so if in a previous life the motor had been fully removed, the mounts pulled off, etc - and then put back together upside down, the commutator would still be on the right end, but the motor would be flipped in polarity.
That's even more likely than the magnets having been put in backwards.
Now that makes the most sense out of all the replys. What I am wondering about. Is why the OP is using the frame for the positive + side of the motor pick-up. All the Athearns I have and all the others prior, had the positive pick-up from the band on the top of the trucks, which is the right side of the truck, going forward. Unless I read His post wrong.
BigDaddy Capt.Brigg The reason I don't leave one of the engines running in reverse of what it should, is that the headlight and rear light don't match the running direction. Someone posted earlier that shouldn't be the case. Does anyone have an explanation on why it does happen, just the backwards magnets?
Someone posted earlier that shouldn't be the case. Does anyone have an explanation on why it does happen, just the backwards magnets?
I know that that someone is incorrect, or at least partially. CV 29 does automatically swap the lights. But if direction of travel is wrong for the lights, it will swap the lights when you change NDOT. Lights will still be wrong.
I know because Ive been there, done that, and have the "I installed the drop in decoder upsided down T-shirt".
You would have to reprogram the appropriate lighting CVs to correct the lighting.
Swapping motor leads is easier, and less confusing later.
Read please some history from May/June 2015.
http://cs.trains.com/mrr/f/744/t/247652.aspx
My error was that I installed the drop in decoder upside down. This had the effect of swapping the motor leads. Flipping it over fixed it.
Edited, and I still cant seem to link internal posts properly.
Edit again, thank you to tstage and cuyama for explaining the fix.
Capt.BriggThe reason I don't leave one of the engines running in reverse of what it should, is that the headlight and rear light don't match the running direction.
Allright so here is where I am at. I pulled both of the engine's motors and hooked up a good DC throttle with the + and - wires on the same side of the motors and the newer motor turned clockwise and older motor turned counter-clockwise eliminating all other causes. Then to satisfy my curosity, I pulled the shell off two other "newer" Blue Box Athearn engines with the same motors and they both turned clockwise like the "newer" NP engine. Some how my older PCRy engine which I aquired about 40 years ago is the odd motor. Now I have to decide which motor to change. Since I use brass clips on all the decoder wires changing wires is much easier than soldering. You can see the clips in the attached picture.
The reason I don't leave one of the engines running in reverse of what it should, is that the headlight and rear light don't match the running direction. Also, when using DCC the engine can be pointing in either direction and will still move in the same direction as both trucks are exactly the same. With NCE decoders when you consist engines they will respond to both the consist number and either of the lead or last engine numbers. The NCE controller remembers what engines are associated with the consist number. Time for me to move on. Attached is a picture of the motors out of the engines. Click the picture and it will take you to a larger image on my PCRy web site.Capt. Brigg, CEO Pacific Cascade Railway in HO gauge
Exactly, tho' I confess I did almost propose the same solution until I thought about it. I did test out my theory before I went into print