i would advise against common rail wiring if you ever intend to convert to dcc. if you insulate both rails when you lay the track, you can daisy chain the connections to one of the rails. this acts like common rail wiring, but the gaps are already in place when you convert to dcc. you simply unchain all the wiring to that one rail and connect it to the associated power supply.

in dcc, blocks are known as "power districts" and often powered by sseperate "booster" power supplies, thus the need to insulate both rails. to be more specific, dcc uses an ac signal, generatedindividually by each power supply. this ac signal may not be in phase with that of other boosters, causing short circuits. and with dcc power supplies of up to 8 amps or more, you can actually weld wheels to the rail.

interesting that you should bring up the lack of a dcc onboard f9.....
is there a reason that the ft chassis  is dcc equipped but not the f9? is the ft shorter? if not, it should be possible to swap the shells to get your dcc f9.

Quote from: pdlethbridge on March 19, 2009, 03:40:25 AM
The polarity of the loop doesn't get changed, it's everything else. If you changed the loop polarity, the engine would stop and reverse in DC

that's the beauty of using the switch motor contacts, it will work for both dc and dcc. in dc, you merely stop the train once in the loop clear of the switches, throw the switch and the reverse on the power pack, then continue on your way. in dcc you don't have to stop. an auto reverser is incompatable with dc.

my friend and i have been using just this system on loops and wye tail tracks for years without any problems, on both dc and dcc.

sid,
that one reversing loop in the lower left can only be entered or exited through the same switch. so it doesn't need an auto reverser. a much more cost effective solution would be to wire the contacts on the switch motor to change the polarity on the loop. it works every bit as well as the auto reverser at a fraction of the cost.

Re: dc locomotives on dcc.
i have yet to do any damage to a dc locomotive by leaving it on a live dcc track. the "singing" noise the dc locomotive makes while sitting there can be annoying though. i have had my dcc system up and running for about 4 or 5 years now.

not only is it possible to do what you want, it was standard practice for many years. AND, with the simple addition of an electrical switch, it is possibel to have EITHER of your power packs power any section of track. this is what is commonly known as block wiring.

plastic insulating rail joiners are readily available in any hobby shop, as are wiring components by atlas. the selector is the component you'd most likely want to use. atlas also offers a book on wiring your layout.

i would give you a basic diagram showing how to do this wiring, but do not have a graphics program to make the diagram. simply describing it without the diagram is confusing., but the wiring itself is easy.

i think what he's referring to is the bottom of the truck gearbox being very low and hanging up. early atlas diesels had this problem. uncoupler magnets would cause these units to hang up as they bottomed out. the solution would be to carefully file away the bottom of the gearbox. on my proto s1, which i assume is similar to your unit, the bottom of the gearbox and truck sideframes appear to come off together. remove these pieces before you do any filing, to keep the dust out of your gearbox. i would stay away from a dremel tool for this task, and use a mill file instead.

did you know you can run dc locomotives on dcc? i know that the bachmann ez command and digitrax zephyr support this feature....

that said, if the f9 has the split frame design most later bachmann locomotives seem to use, adding a decoder is relatively easy. this link shows how:
http://members.shaw.ca/sask.rail/dcc/tmaster/tmaster.html

if it is the old bachmann where the motor and power truck are one unit, i wouldn't bother trying to convert it, especially when you can get dcc onboard locomotives for $50 or less.......

Has anybody tried using the AAR type B truck sideframes used on the RF16 sharks to model the GP30s and GP35s that used them? are they compatable? what modifications if any would be needed to use these on a GP30 or GP35?

yes, ribbed back wheels were used back during the steam era. the purpose of the ribs was to dissipate the heat generated by using the air brakes on the cars. they were phased out because the improved braking power of diesels made them obsolete.

on split frame locomotives, the frame halves must be insulated from each other. on bachmann units this is accomplished by a metal screw thascrews into a plastic housing which is seated in the frame. there is also a plastic washer which fits between the frame halves. if you are shorting, then one of the plastic pieces is probably missing. if it is the washer, you may be able to use fibre washers from kadee as an easily available substitute. if the plastic housing is missing, you'd have to go to bachmann for parts.

if neither of these is missing, then i'd try taking the locomotive apart, and checking the frame halves assembled without any other parts, then each truck. in each case, you shouls read infinite ohms between the sides. not that on a truck you willl read a between the wheels on the same side, as they are normalls in contact with the same rail.
if none of these reads a short, you probably have a bad motor.

Quote from: the Bach-man on March 11, 2009, 10:19:12 PM
Dear Mark,
I've never seen a Bachmann SW, but I hope the airhose tip works!
Have fun!
the Bach-man

would there be ANY chance of a sw900 or sw1200 from bachmann in the future?

say you have 12 volts applied to the track. using a voltmeter you can measure and prove for yourself that the voltage difference between the two rails is 12 volts. the wheel pickups transmit this voltage to the two halves of the frame, with minimal losses. you can thus place the locmotive on the track, and using the same voltmeter, read approximately 12 volts between the two halves of the frame. this is more than enough to light the headlight. the headlight is in parallel with the motor, and we know the voltage difference between the two rails is what causes the motor to spin and move the locomotive.

Quote from: SteamGene on March 14, 2009, 09:40:01 AM
If you're using dissimilar rail type, I would caution soldering them together at the rail joints, but that is for another thread.

Does this mean different code rails - 70 to 83  or does it mean nickle silver to brass for examples? In addition, do you advocate soldering them together or NOT soldering them together?
Gene

no, there is no problem soldering different sizes of rail together that are made of the same metal. just make sure that the tops and inner edges of the rails are aligned.

as for different types of metal, i haven't had any problems with soldering them together brass (which i have used for sidings) and nickle silver. the brass requires cleaning and flux for the solder to work. steel is VERY difficult to solder to, and using flux tends to rust the rail. btw, i only use rosin type flux. the acid flux used to solder pipes is no good for model railroad use.

i have heard that different metals joined together can cause corrosion due to a small electric current between the metals, but this is getting into chemistry and physics here. aluminum was notorious for corrosion when joined to another metal, and aluminum wiring which was used in houses and some diesel locomotives was a known source of fires.

if you do decide to install a sound decoder, the one you are looking for would have sounds for an EMD 567engine with turbo. while not exactly prototype, an EMD 645 with turbo, sometimes called "EMD second generation" is a passable substitute.