Atlas O GP9 Pickups

Would you now consider trying this loco on battery radio control.  If you are curious please contact me using the  email address listed in my profile.  Don

Contact Atlas regarding a replacement spring?

Personally I'd be surprised if just one pick-up is causing all that trouble. And shorting out as well? How, as the spring is inside the plastic housing, & simply means the plunger isn't contacting the wheel? With three other wheels picking up the same side current - &  only one of those via a similar plunger - I wouldn't have expected stalling at all.

Maybe there's another problem somewhere? Is a pick-up wire touching the chassis intermittently, shorting that way, for instance?

the design of the Atlas plunger pickup has the electric current running through the spring. over time the spring heats up and anneals, losing its ability to spring back, losing contact with the wheel. this is common to most Atlas engines with this style of pickup.

I've been told by Atlas service they have redesigned the plunger pickup but the newly engineered pieces have not yet been delivered.

there is a fix for this, if John Sethian notices this thread perhaps he can help with his detailed solution.

I converted my Atlas RS-1 from those spring loaded contacts to wipers against the inside surface of the wheels. The engine runs reliably, but is quite sensitive to dirty wheels so before I operate this particular loco I clean the wheels on a alcohol soaked paper towel. I've had some of the plating come off the wheels, but never replaced them.

Bob

PRR Man posted:

the design of the Atlas plunger pickup has the electric current running through the spring. over time the spring heats up and anneals, losing its ability to spring back, losing contact with the wheel. this is common to most Atlas engines with this style of pickup.

I've been told by Atlas service they have redesigned the plunger pickup but the newly engineered pieces have not yet been delivered.

there is a fix for this, if John Sethian notices this thread perhaps he can help with his detailed solution.

Thank you for that bit of info. I have been working converting to wipers, but this task has become beyond my knowledge and ability. I would very much like to know what the fix is. Any idea on when the re-designed plungers will be delivered? 

Atlas says you have to reuse the plungers,fabricate your own springs (some ball point pen springs will work) but they do sell the plastic holder sets if needed. The repair i did pickups shorted,melted the housings and collapsed the springs. Plungers were reused.

vonhammer87 posted:

PRR Man posted:

the design of the Atlas plunger pickup has the electric current running through the spring. over time the spring heats up and anneals, losing its ability to spring back, losing contact with the wheel. this is common to most Atlas engines with this style of pickup.

I've been told by Atlas service they have redesigned the plunger pickup but the newly engineered pieces have not yet been delivered.

there is a fix for this, if John Sethian notices this thread perhaps he can help with his detailed solution.

Thank you for that bit of info. I have been working converting to wipers, but this task has become beyond my knowledge and ability. I would very much like to know what the fix is. Any idea on when the re-designed plungers will be delivered? 

I guess john Sethian noticed this.  See the following:

Atlas has a rather poor design for the pickups.  Here are the first clues:

Note the melted cover:

It turns out that Atlas chose to configure the pickups as shown:

A small lug is soldered to the end of that wire.  That lug presses against a steel compression spring, which in turn presses against a plunger.  There are so many things wrong with this arrangement and on so many levels that I don’t have the energy to list them all. Let's just start with two edge on contacts and an unguided spring made out of a poor electrical conductor that is being asked to carry all the current.  

But I do have a solution:

On the left is a standard size K&S brass tube with the pickup wire soldered to it.  On the right is the next smaller size K&S tubing, with a brass escutcheon pin soldered in the end. I used a phosphor bronze NWSL spring, but most any type of spring will do.  Because in this design the spring is not carrying the current.  

Thank you for posting this, I will give this a try tonight. 

But I do have a solution:

On the left is a standard size K&S brass tube with the pickup wire soldered to it.  On the right is the next smaller size K&S tubing, with a brass escutcheon pin soldered in the end. I used a phosphor bronze NWSL spring, but most any type of spring will do.  Because in this design the spring is not carrying the current.  

 

Nicely done!  The spring rate just needs to be the right compromise between maintaining constant contact and adding too much drag on the wheel sets. 

VONH: You might find a suitable spring in a "clickable" ballpoint pen that can be cut into 2 or more pieces for this application. [EDIT: Oops, already suggested above, sorry]. I can confirm it works!    

If the install is for DCC, I'd also recommend adding a Keep Alive to the decoder if none present.   

Pete

An alternative to John's method, if you have skills and tools is the reverse.  Drill a hole in the back of the existing contact that a piece of brass rod can fit into and solder the connector to the rod and let it slide inside the existing contact and spring.  In either case use a conductive lubricant, which is something Atlas should do.

Pete M posted:

But I do have a solution:

On the left is a standard size K&S brass tube with the pickup wire soldered to it.  On the right is the next smaller size K&S tubing, with a brass escutcheon pin soldered in the end. I used a phosphor bronze NWSL spring, but most any type of spring will do.  Because in this design the spring is not carrying the current.  

 

Nicely done!  The spring rate just needs to be the right compromise between maintaining constant contact and adding too much drag on the wheel sets. 

VONH: You might find a suitable spring in a "clickable" ballpoint pen that can be cut into 2 or more pieces for this application. [EDIT: Oops, already suggested above, sorry]. I can confirm it works!    

If the install is for DCC, I'd also recommend adding a Keep Alive to the decoder if none present.   

Pete

Pete - Thanks, I was planning on going that route, but i was wondering would a coupler spring work as well?

EDIT: also what diameter tubing would be used? 

I have the Gold series of this engine with the QSI sound.  My pickups are the brass wiper type, not the plunger.  I am having problems with the engine stopping all the time due to bad pickups.  The brass wiper seems to have a small dimple on them which provides a very small pickup area.  I clean and clean and still it stops over and over again.  Can I fix this problem or is there perhaps a loose connection between the wiper and the decoder board wiring?

Really getting tired of pushing the engine by hand, it then moves a couple of inches and stops again.

Check the online diagrams for this engine from Atlas and they don't even show the wipers.

Hopefully someone has some insight on this subject.

Thanks, Jay Beckham

Jay,  You need to look into RC Battery control. All physical contact setups will have problems sooner or later. You might want to speak with Tom Thorpe (Curved Bench Work) who posts here on the forum.

Simon

PS: Great looking scenery on your pike, some of the best I've seen!