Looking for other idea’s that I haven’t thought of. Purchased two of these loco"s at a local show, used. Excellent condition cosmetically but the truck wheels were worn well. Ordered replacement trucks from Atlas and slapped in two TCS decoders. Also cleaned, lubed and adjusted frame half screws. One engine ran real well with no trouble both forward and backward. I always test this way going slow and then increasing up to about speed step 20. Ok it’s done.
The other engine is another matter as it will spin the wheels at times with no grab. I have completely taken it apart and checked everything for fit and smooth running. The motor is great and all contacts great. I have adjusted the frame half screws to be sure the trucks are free turning. I get no flicker with the lights and smooth running is good as far as the motor is concerned but is goes some and gets wheel spin but not always movement.
As I mentioned these are brand new trucks, the other engine is great and I really don’t want to use Bullfrog Snott on the wheels. I of course think of weight but the other identical model runs perfect. I have had a flashlight on the wheels and they spin fine, are touching the track but won’t grab all the time. The engine goes some, slows, goes again, stops even though the wheels are turning ok and it just grinds on the track. I’ve never had an engine run this way before. Any suggestions? Doug
Without having it in my paws or seeing it…My guess would be that the suspension and or driveline is too stiff. No rocking type movement in the trucks or enough fore and aft movement , which would be vertical up/down in the trucks or driveline, for the weight involved. Think Indy car racer trying to get traction, out of the pits, after a fuel or tire stop, spinning its wheels. In most part due to high horse power, light weight and stiff suspension. Most outlaw circle track race cars are also like that…mine was.
If Your track work is not perfectly level, no dips, rises, it will make it react what you are describing. Hits a dip or rise and loses traction.
Thanks for reply both Gary and Frank. Both trucks are spinning when the engine looses traction. The engine will do this whether on level track or entering a grade. I lay track very carefully concerning starting into a grade and all of my engines have no problem anywhere on the new build and the track has been ballasted for over a year now. In adjusting the tightness of the frame half screws just a little the trucks will be flexable in all directions with no hang ups.
As I mentioned in the beginning the first of these two engines is just fine but this one really has me puzzled. I have disassembled it completely, checked the frame for straightness, checked the truck pockets etc. The engine sits on the track with all wheels touching the track. This engine can be anywhere on the layout and it will go and then spin the wheels with no traction and go some more.
I realize that this could be the reason this person at the show sold me the engines (cheap) but I usually can find a problem and repair it. I really thought replacing the trucks with new ones would work but on this engine it hasen’t helped. So unless I figure it out this engine may be a long time fixture in the repair shop. Thanks to all with any ideas. Doug
Like I said, without seeing it, I’m just pulling at straws. My gut feeling still is either driveline or trucks are too rigid. Do both of them have some up/down movement at all in the trucks, like front of truck can move up at the same time rear of same truck goes down. That’s what I mean by rigid…not swivel.
Yes Frank, both trucks have free movement independent of each other. With wheels spinning on both trucks all wheels are touching the track and no light blinking, so solid track conductivity. Doug
Just a wild guess, but are the pilots on both ends so low that they’re touching the track and holding the loco slightly off the track? What about the fuel tank – is there adequate clearance between it and the rail? A coupler trip pin so low that it’s catching on a crosstie?
Since this problem started I took off the body shell and cat walk way so no couplers are involved. So the pilots are not touching anywhere and I also took off the fuel tank cover. I did all of this for visability using my flash light and special optics. I fail to understand why the one identical engine is a good runner and this one is totally unreliable. It’s a real hair puller. Doug
Yeah, that sure would be a hair puller/head scracther.
And You think they feel about the same weight?
Do You have any place on it to temporary put more weight on it to test? I would be interested to hear if that made a big differance. But it still don’t make sense, why one works.
Good Luck, Again.
Frank
EDIT: Idea. I wonder somehow, if one of the trucks, stops pulling, like a main gear loose on a shaft, then starts to spin again when it grips. If you can. Try powering the engine running in one hand and with your other hand, hold one of each trucks wheel. If you can and the other truck continues to spin, you may have found your problem. (fingers crossed)
About three weeks ago, I spent a week inside an Atlas SD-9 (N scale) in one afternoon. You might want to check to make sure the male universal is inside the flywheel. That is the tiny part that fits inside the flywheel and attaches to the universal (drve) shaft to make sure it turns with the flywheel.
Part of my woe was the male universal was not seated, so the motor would turn fine, as would the flywheel. But the driveshaft would only turn if there was friction because the male universal was doing nothing. Funny thing is it does not secure into the flywheel all that well. Let’s just say that discovering that factoid produced great annoyance and displeasure.
I invented some new words that afternoon. I suspect you may have invented a few new ones by now, too.
That’s what I have been thinking also something in the driveline is not making good contact and sometimes works then stops. The other truck spins it’s wheels trying to pull/push the dead one.
Since the SD-7 is a six axle loco and you say all the wheels are turning but having no traction makes me think that not all the wheels are in positive contast with the rails when the loco stalls. Can you remove the center axle and wheels to see if the center set of wheels is keeping the other wheels from providing traction? Try running it this way. Seen this before on a cheap Tyco loco I had.
There are several very small parts that can dislodge or fall out in the chain between the flywheel and the wheels. I guess it is even possible for the flywheel on one side to be slipping on the axle. If that is happening, fixing it would be possible if one has the concentration and steady hands of a jeweler.
The male universal is the first component on the actual drive train. But I have also seen gears inside the truck be slighly out of position, which would cause that truck to bind up or just not transfer the spinning from the drive train to the wheels. I have also seen burrs on a gear in a new truck cause oddball problems. Any of those is possible.
The other thing that can cause strange problems is if the metal wiper can get out of position, and since the tips of the axles are supposed to fit into it, either create a lot of drag by not allowing the axles to spin freely or putting pressure on them to be out of alignment. I just looked at a spare SD9 truck I have and it should be possible to see if the wiper is in place without taking the sideframe off the truck (a lighted Optivisor is a handy tool for this!). Since there are two wipers on each side, one not being stellar electrically would not interfere with the flow of electricity but could wreak havoc with the transmission of power from the motor to the wheels.
As far as removing the center wheel, that will require disassembling the entire truck with several small gears. I’d be more inclined to try another truck, even one of the old ones with the worn wheels before I went through that. The problem may not go away
In reply to everyone; Yes all wheels turn under power. The old trucks did and so do the new trucks. I noticed that, (at least it seems like it) when the loco starts in either direction the front of the truck for that direction will slightly lunge forward. So I have ordered a new body and drive train from Atlas that will take about a week again but what the heck, I am out of options.
The other Identical engine runs perfect with new trucks and it’s trucks do not lunge forward when it starts so right now my thought is that this one has to much slop in the truck pockets. Keep in mind that the motor with its new TCS decoder is fine in all use. I have checked the new and old trucks both to see if all wheels touch the track and they do. All wheel flanges are level with each other in each truck. Also yes, this SD7 has three axel trucks.
I am going to wait for the second order of parts, install them and see what happens. If that doesn’t work I might bite the bullet and send it to Atlas just to see what their tech’s can figure out. Hate to spend the money for that on one of two used engines I bought at a local show but this is so off the chart I want to find out.
I do appreciate all the input from all of you on this, " maybe a Lemon of an engine". Doug
