rrinker I always thought the wheel itself could easily touch the frame in a derailment situation where either the opposite rail drops down off the railhead, or the flange of a wheel rides up on the railhead. It might instead be the pickups, or the point where the track power wires solder on to the trucks. The same truck doesn't have to touch the rail AND the frame, the track pickups are wired in parallel so if the rear truck stays ont he raila dn the front truck rides up on somethign and touches the frame - same thing, track power applied ot the frame. Once the isolation is accomplished, there's no problem, even if something does touch the frame, because neither motor wire is in any way connected to the frame. --Randy
I always thought the wheel itself could easily touch the frame in a derailment situation where either the opposite rail drops down off the railhead, or the flange of a wheel rides up on the railhead. It might instead be the pickups, or the point where the track power wires solder on to the trucks. The same truck doesn't have to touch the rail AND the frame, the track pickups are wired in parallel so if the rear truck stays ont he raila dn the front truck rides up on somethign and touches the frame - same thing, track power applied ot the frame.
Once the isolation is accomplished, there's no problem, even if something does touch the frame, because neither motor wire is in any way connected to the frame.
--Randy
Randy,
This all makes perfect sense, and I appreciate the explanation and the time and thought put into it. Most appreciated.
One upshot of all of this is the logical conclusion then that the metal motor mount screw is just fine and should cause no problem since the tab is removed and the brushes are isolated from the frame.
Rich
Alton Junction
Yes, there is that too - the frame IS painted, which is ostensibly insualting, liek painting frog points with nail polish to cure shorts. But it can and does wear off if contact is made. With the tab removed thant he motor taped you should not get any continuity between eithe rmotor wire and the frame, scratch off some paint up inside the shell to get a clean contact spot that won't show when the shell is on
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Two months later, I finally got around to replacing the fried decoder.
I got some Kapton tape and fully insulating the decoder and the motor from the frame. I cut off the metal tab and insulated that area as well. I added a nylon screw to hold the motor to the frame. The orange wire now is soldered to the brush.
So far, so good. This is my second replacement decoder. The first time I fried one when the loco derailed on a open switch. I thought that I took the necessary steps when I replaced the decoder by rerouting the orange wire from the frame to the brush. I made sure that the decoder and motor were fully insulated from the frame. But, at the time, I was unaware of the problem with the metal tab touching the frame.
So, I am keeping my fingers crossed that I have properly addressed the "Proto S-3 Problem".
If I blow any more decoders on this loco, it will be sold on eBay as a DC loco.
davidmbedard Sigh...... As a professional decoder installer, my first and primary goal is to install a decoder into a locomotive only once. Hence, the advice I give on these boards is to reflect this practice. If th OP followed my origional advice, the install would have gone smoothly and would have been worry free. David B
Sigh......
As a professional decoder installer, my first and primary goal is to install a decoder into a locomotive only once. Hence, the advice I give on these boards is to reflect this practice. If th OP followed my origional advice, the install would have gone smoothly and would have been worry free.
David B
Trouble was, David, you weren't around when I first installed the decoder back in 2004. Blame Proto, not me. It was an acknowledged design flaw by Proto. I only found out about it after the decoder got fried and others on this forum advised me how to work around the flaw. That was a few years back.
This time around, the failed workaround was my fault, I guess, since I did not know enough to insulate around that metal tab touching the frame. But, again, I blame Proto, and I think fairly so, for the design flaw.
It wasn't "DCC Ready", contrary to their marketing claims and their label on the box.
I wouldn't consider it a design flaw. It's more DCC Ready than some things are they say thatont he box - since the term is really meaningless. As it comes, even witht he screw grounding of the motor to the frame, the motor IS completely isolated from the track pickups, the key component of being DCC ready. Now, granted, a derailment can knock a wheel against the frame, destroying that separation...
BTW I posted my pics of isolating the motor in an S1 in July 2004. Probably mentioned it here, too, since I was a posting fiend back then, too. And doing a better job of keeping my web site up to date as my construction progressed.
I think this will work: http://community.webshots.com/album/163958178NgaXTy 7th photo, one captioned "motor tape". The complete caption says "Apply a piece of tape to the lower brush cap to insulate the motor from the frame. That's the whole point of this exercise, so don't skip this step!"
rrinker I wouldn't consider it a design flaw. It's more DCC Ready than some things are that say that on the box - since the term is really meaningless. As it comes, even with the screw grounding of the motor to the frame, the motor IS completely isolated from the track pickups, the key component of being DCC ready. Now, granted, a derailment can knock a wheel against the frame, destroying that separation... --Randy
I wouldn't consider it a design flaw. It's more DCC Ready than some things are that say that on the box - since the term is really meaningless. As it comes, even with the screw grounding of the motor to the frame, the motor IS completely isolated from the track pickups, the key component of being DCC ready. Now, granted, a derailment can knock a wheel against the frame, destroying that separation...
OK, how about this? "Almost DCC Ready". To me, and I would bet to most people, DCC Ready means that if you wire in a decoder, you are ready to go and that the decoder will not be fried by excess current reaching the decoder.
One thing that you pointed out earlier in this thread, Randy, is that excess current can reach the decoder even though the motor may be isolated from the track pickups and even if the wheels don't touch the frame. Here is that comment.
"I always thought the wheel itself could easily touch the frame in a derailment situation where either the opposite rail drops down off the railhead, or the flange of a wheel rides up on the railhead. It might instead be the pickups, or the point where the track power wires solder on to the trucks. The same truck doesn't have to touch the rail AND the frame, the track pickups are wired in parallel so if the rear truck stays ont he raila dn the front truck rides up on something and touches the frame - same thing, track power applied ot the frame."
I think that the latter part of your statement is what happened in my situation.
If it is not a design flaw, then, at the very least, the early Proto S3 was not DCC Ready. The orange wire was screwed to the frame and needed to be rerouted to the brush, and the metal tab touching the frame needed to be clipped and insulated so that there was no contact with the frame. Also, there is some debate about whether the metal motor mount screw needed to be replaced with a nylon screw.