Two N Scale Turbo Trains, 50 Years Apart

[wm3798]

Sorry if I missed this, but are you using the stock motor?  Or did you refit it with something more reliable? (5 pole, skew wound etc.)

Lee

[Dwight in Toronto]

G’Day Lee - yes, thus far I have been using the original Bachmann mechanism.  It’s significantly noisier than current motors and drivetrains, but seeing as you are a vintage devotee, you will be familiar with that. 

I completely stripped the entire chassis down to its individual component parts, used contact cleaner on the motor, burnished all wipers and contact surfaces, lightly oiled axle and motor bearings, greased the gear train etc., all of which actually quietened things down appreciably.

I installed an ESU LokPilot decoder a few days ago, and I’m elated at how well the entire train set is performing!  Speed step 1 delivers an impressively  S-L-O-W  and quiet crawl, something that was not even remotely possible on DC.  Accel/decel is smooth, and the set will effortlessly traverse my test loop, which includes a severe, exaggerated ‘S’ curve, on even the slowest speed steps.  I attribute this to the addition of the auxiliary track power pickup from the trailing single axle bogie.

My longer term objective is to try to adapt a more modern mechanism for use in the power cab.  I mentioned that someone had earlier suggested maybe cutting down a Kato or Atlas chassis to fit.  If I can find a suitable candidate at a train show, it will make for an interesting upgrade.

I’m awaiting delivery of some prewired LED’s, in order to add a mars lamp to the nose cone lighting cluster.  When I get that done, I’ll make a short video to demonstrate how nicely this goofy little project is turning out.

And hey, thanks for checking in … I was feeling that Peteski was the only one who was still following along!

[peteski]

Some brands of DCC decoders (with BEMF enabled) can do a really good job masking motor and mechanism deficiencies.

[Dwight in Toronto]

While waiting for prewired LED’s to be delivered, I examined the trailing cab to see if/how I might add a single, “always on” red LED to the rear nose cone as an end-of-train marker.

Here’s the trailing truck assembly - there’s a substantial amount of room in that shell! 
Once again, I’m leaning towards somehow using one of those little ESU wheel wipers to get track power into the cab:




After a bit of trial and error, I think I’m going to try the following arrangement.  It’s simply two pieces of thin brass sheet to which I’ve soldered the copper wheel wipers (salvaged from that ESU gizmo).  These will be epoxied to either side of a thin styrene insulating separator … a “sandwich” of sorts.  The wheel wipers will be bent 90 degrees to squeeze behind the rear wheel faces, and the brass pads will then serve as the main conductor surfaces:




Those little springs in the single axle power pickup bogie seem to be working quite well, so I’ll try a similar approach here.  I’ll drill two vertical holes through the top of the bogie chassis, centred over each of the brass pads.  Then I’ll drop a spring, straight up & down, through each hole.  One end of each spring will rub on a brass pad, and the other end will be soldered to a length of decoder wire.  At least, that’s the theory … what will actually happen in reality is anybody’s guess!

Peter - I’m hoping to illuminate a single red 0402 LED right off of DCC track power, and I think I’ve got one of your wee circuits saved somewhere.  If I get stumped, I’ll give you a holler! 

[Dwight in Toronto]

@peteski - here’s the circuit I was thinking of.  Since I won’t be using a decoder, could that particular wire instead be one of the track power leads?  What resistor might be best?




I do have a small, 4-pin full wave rectifier - would it be better to use that?  In the past, I’ve used a 5V voltage regulator, but you’ve said it’s not necessary.  What about a capacitor for flicker avoidance?  Looking forward to your recommendations. 

[peteski]

No, that circuit is for generating the "blue"voltage for function outputs coming from the decoder.  I suppose it would work, but not optimally.


Better to use a bridge rectifier like shown here.  If you don't have a bridge rectifier and have diodes, you can make a bridge rectifier from 4 discrete diodes.

If you look into my Photo Gallery, you will find bunch of circuit examples.  https://www.therailwire.net/forum/index.php?action=gallery;su=user;cat=681;u=2700

[Dwight in Toronto]

Peter - perfect - thanks much.  I do have a bridge rectifier, so I’ll go with the lower schematic.

Here’s how the “brass sandwich” conductor pads turned out, held in place on top of the truck with double-sided tape:




Also shown are the spring-based commutators, and if one looks closely at either side of the truck-retaining tower, two small pilot holes are visible in the floor of the chassis.  After being drilled out, these are where the springs will pass through.

[peteski]

Your electric pickup scheme is similar to what was used in the ancient German-made Arnold Rapido GP7s, and others from that time period. Some Minitrix locos also used similar wiper system.

[Dwight in Toronto]

Your electric pickup scheme is similar to what was used in the ancient German-made Arnold Rapido GP7s, and others from that time period. Some Minitrix locos also used similar wiper system.

Thanks (I think!).   It IS an ancient model, and one must work with whatever limitations that might impose!

Also, where possible, I try to implement changes that can be readily reversed.  For example, if this particular pickup scheme doesn’t pan out, the simple, non-intrusive alterations ensure that I can easily put that trailing truck right back to the way it was.  And then move on to an alternate approach.

[peteski]

Thanks (I think!).   It IS an ancient model, and one must work with whatever limitations that might impose!

I did not mean that as a negative thing.  I just thought that it was interesting to see you come up with a wire-free pickup system used by "real" model companies.  Actually even some contemporary models from European manufacturers still use this design in their models.

[kiwi_al]

This is a very interesting thread! Dwight have you got a picture of the Bachmann motor? I'm curious to see if it is the usual one.
Does it look like these? The one one the left is the old Bachmann one, the one on the right is a brand new Chinese made motor.

[peteski]

The chassis is painted with black crinkle paint, so it  is a really old model. I suspect it is an even older version than your "old one" in that photo. They used square-shaped brushes and the brush holders were different. It also has straight-wound 3-pole armature where the ones pictured both have 3- and 5-pole skew-wound armatures.

[Dwight in Toronto]

@kiwi_al  … I had removed the motor to give it a few shots with contact cleaner, but I really didn’t pay that much attention to it.  All I can say is that it’s the original Bachmann motor, circa
1974-ish.  Appearance-wise, I can only say that it looked the same, or very similar, to those in your pic.

Peteski’s assessments are usually purdy darn accurate and reliable, so I’d go with that!

[Dwight in Toronto]

Completed installation of the ‘commutator’ springs, as part of the ‘always-on’ rear red marker light sub project.

I first needed to provide two small blocks of styrene inside the bogie shell, into which I could drill two holes (from the bottom-side-up), to serve as retaining “wells” for each spring.  The styrene ‘bridge’ spanning each block acts as a backing plate for the springs, with much smaller holes through which the wires have been inserted:




And here’s a pic of the bottom side - two small black screws are holding the styrene blocks in place, and the commutator springs have been nestled into their retaining wells:




I snapped the two-axle bogie back into the chassis, placed the assembly on a piece of track, and confirmed continuity between the track and each of the wire ends. 

It’s time to make up Peteski’s simple little circuit for illuminating the rear LED.

[Dwight in Toronto]

To illuminate a rear end-of-train marker in the trailling cab, I soldered a bridge rectifier to a small piece of pc board, along with three 1.82K smd resistors (5.46K). 

Connected track-sourced power to the AC side of the rectifier.  Lacking a red LED, I popped a spare 3mm unit that I had onto the DC side just to see if everything works.  I placed it on DCC Kato Unitrack, and  …  voila!




@peteski  - my guess is that there is going to be light flicker.  I have a 1000 UF/25V capacitor that could be squeezed in there somewhere (10x25mm).  What size resistor might that cap need, and where should the cap & resistor be positioned?  Thanks in advance!