N Scale Intermountain AC-12

[carlso]

 Have any of you guys had an occasion to change out drivers on an AC-12 ?  I have one from the original production (10 years old ?) that is showing signs of the GS-4 driver syndrome. The two geared drivers are wobbling so bad that it is causing rods, valve gear and anything else possible to jam up. I pulled the plate off the bottom and checked all the drivers and they all seem to be seated properly, however the one, in each engine, with the gear wobbles so bad that it looks to me like the axle has ridden at an angle and egg shaped the bearing. I also noticed that part of an rectangle gadget in the valve gear is missing so that has contributed to the jamming. I was able to carefully bend a couple of the pieces and have stopped the jamming, temporarily at best.

I sent IM a note regarding parts and received a notice today that they are sending me new rods, valve gear, and pins for both engines, but alas no mention of drivers. If they do not come in later does anyone have a suggestion on what drivers to attempt to use? Find a basket case AC-12 ?

Carl

[peteski]

I'm not sure what you are asking.  If you are replacing drivers, they have to be from another IM AC-somethign loco.  You can't replace them with let's say Athearn Big-Boy drivers.

[victor miranda]

well... the gear didn't come loose or it would not run.

the side rods are prone to wear because of where they live.

the wobble has my curiosity.

off to find pictures....

one from a while back...
http://i30.photobucket.com/albums/c301/kv-ironworks/shopped/cab-forward/PICT0284.jpg

the atlas thread  http://forum.atlasrr.com/forum/topic.asp?ARCHIVE=true&TOPIC_ID=58826

victor

[carlso]

Victor,

thanks for the two links, very informative.

I need to clarify my statement regarding the wobble. I said the two geared drivers were the culprits but I was wrong. I should have said the drivers on each engine that have the eccentric crank and rod on them are extremely loose and tend to have an extreme amount of vertical play that allows one side to "play" more than the other side and vice versa. Maybe that is by design ? ? Actually the drivers act like they are not balanced well enough to offset the crank pin rotation. With plastic centers I suppose it is a lost cause to worry about it. I may use the new parts and just run it 'till it farts and falls by the wayside.

Carl

[victor miranda]

can you take and post a photo?

at first, I had thought something had melted and now I am thinking a bearing may have gotten loose.
... and I can't imagine that is not obvious.
worn bearings are possible.  seems loke a lot however.


so I puzzle.

are the siderods slack? ( that is they have a lot of play)

[peteski]

Carl,
let me tell you a story. 

I have 3 AC-12s: 1 from the initial run and 2 from the later run.  I haven't put much mileage on any of them.

All the drivers in the 1st run loco are mounted with very little vertical play.  To me that is as they should be.  When I bought the 2 newer locos I noticed that in both of them all the drivers had lots of vertical play. I also took the bottom cover plates off but I didn't see anything out of place.   Without doing any measurements or comparison with the 1st run loco I can't be sure but I suspect that the problem is that the openings for the bearings are machined too deep (which gives the bearings extra vertical play).

Few years back I took one of those locos the the Springfield show and I showed it to Richard at the Intermountain booth.  He examined the loco and agreed that, while it seemed to run ok, the drivers did have way too much vertical play.  He told me to send both locos to IM and he would take care of the problem.

I sent both locos to IM. I included a long letter explaining the problem in detail and the fact that Richard told me to send them in for repair. They kept them for a very long time (several months).  When I finally received them back, the enclosed receipt stated that they were repaired.  But upon examination, they both still had excessive vertical play in the drivers. So much for them being repaired.    Maybe they did replace some parts which could have made a minimal difference in the excessive play, but I couldn't tell - to me the drivers still exhibited excessive vertical play.  The locos are put away now, but I recall that the vertical play was not identical on all the drivers and on each of the engines.  Some axles on some engines had more play than others.

The reason I questioned and tried to get this excessive play repaired in the first place was that I thought it might cause excessive wear of the siderods in heavy use. I haven't put much wear on those locos, but it seems that you loco is from the same batch and that in the long run it was in fact affected by the excessive vertical play in the drivers.

EDIT: I should add that in the past, my experience with IM costumer service was excellent. They always went above and beyond my expectations (mostly with some issues with my FT sets, but also helped me out on couple of other things).  But this last experience has really soured my view of IM.  It wouldn't be so bad if they sent the locos back without saying that they were "repaired".  But to keep them for several months seemingly without fixing anything, then clearly state that they were repaired (especially since Richard personally saw them and acknowledged that there was something wrong) is just not cool.  Needles to say, I didn't contact them again, and I will probably sell those 2 locos with excessive play in the drivers.

[carlso]

Peteski,

thanks for the comments, I appreciate them. I am not real sure about what I am looking for here but IM is sending me new side rods, valve gear, and pins. I was hoping for new driver set, but most likely will not see any. I have attached a video of the AC running on my test stand and it has revealed  way more than I had been able to see.

Victor,

I decided to make a video rather than stills. I now have studied it many times and am surprised at what I see. first off, there is something wrong with the eccentric crank rod, front engine, as it does not move anywhere close to the one on the rear engine. I see some binding, or something, in the valve gear and it looks like a part is missing pieces.

I know that both Peter and victor are way more knowledgeable than I but as a reminder :

The front engine, listing from head end of loco towards the rear and steam chest;

#1 driver = TT and gear and is pinned
#2 driver = eccentric crank and pinned
#3&4 driver = pinned

The rear engine listing from front towards the steam chest:

#1 driver = TT and pinned
#2 driver = gear and eccentric crank and pinned
#3&4 driver = pinned

The video came out longer than I intended but if you have time to watch 3-4 minutes of it you will get a good idea about how the drivers look. I think I see some slop in the rod crank pin holes that look to be elongated ? ? ? Note how the #3 driver, rear engine, acts. It is being lifted off of the test stand roller as the eccentric crank to the right of it goes up in its rotation. I do need to add that this loco is/was one of my favorites and has been run very heavily. It is from their initial production back 10 year ago ? ? ?
The vid may be interesting to you. I am not real sure how this loco ran so well. Sorry about the decoder noise but I was adjusting it at the same time. One thing to note is that when you see the drivers start turning, in all cases, that was on speed step #1 with a 128 set up in the decoder. Actually pretty darn smooth.

Thanks for all help and hope we can learn something from the vid. Watch it a full screen for better close up.

Carl

[victor miranda]

from the vido.
yes long and helpful.

your eccentric crank on the second engine is too far out. It should be closer to the center.

If that were my loco I'd check the quartering.  that is how the 7 driver looks.

the most likely axle to be wrong is the one with the gear.

see if intermountain will sell you new axle bearings.
(they may sell the drivers to get the new bearings...
you have the same problem in the first engine.
it is hard to tell if the quartering is a little less off or if the bearing is tighter.

this loco has a higher than normal torque motor in it
(normal for n-scale)  so the slight quartering issues that often cause a hitch
will not be easliy seen

victor

[carlso]

Victor,

as I stated above I asked for new drivers but either they do not have them at all or maybe they are just out of stock. when I receive the other parts maybe there will be a note regarding drivers ? ? ? My guess, they do not have replacement sets.

Now teach me please. How can the drivers be out of quarter when there is only one geared axle per engine. I thought that would not be a problem with only one geared axle. I am trying to learn. As far as the cranks on all four drivers goes they are factory installs so if one or all of them have a problem, they were made that way.

My guess would be that the side rods or part of them are either too long or short that has caused the lifting of drivers and also the stretching of pin holes. But as I said I am trying to learn. After 5 or 6 years of running in that manner I would believe that the bearings which are round sleeves have probably been worn egg shaped .

The video really shows the operation well ? ? ?

carl

[peteski]

Carl,
properly quartered does not have anything to do with properly adjusted gears in locos where multiple driver axles are geared.  Quartering is an adjustment purely related to the location of the crank pins in the drivers.    If multiple axles are driven then that has to be considered in addition to quartering of the drivers. In that case the drivers need to be quartered properly AND the gears have to be properly adjusted to have the crank pins at the same position on all the drivers.

Quartering on any steam loco is simply aligning the crank pin location to be identical on all the drivers.  Whatever angle that happens to be (usually 90 degrees but in models, not always).  If they are not then that will cause binding of the siderods (even on non gear driven axles).

[Loren Perry]

from the vido.
yes long and helpful.

your eccentric crank on the second engine is too far out. It should be closer to the center.


Victor is correct.  With each forward stroke, the valve gear rod linkage is actually striking the plastic crosshead guide hanger and bending it forward slightly. This causes an unwanted thrust to the main driver. Moving the crank closer to the center will stop this. Look at the forward engine's arrangement and try to match it.

[peteski]

I agree with Victor's and Loren's assessments.

[carlso]

Hey guys, I am going to wear you out. Thanks for all the input. I mentioned above somewhere that I thought there was something wrong on the front engine as the eccentric rod was not working as much as the rear.

Loren, after your comment I watched it run again and did see the crosshead guide being hit, with a pretty severe thud. I picked at the eccentric crank and find that it is loose and can be moved into a more centered position . When I did this the eccentric rod did not hit the crosshead guide and the driver is not lifting as before.

Now my question is should the crank be able to rotate forward or backward on the crank pin? I did not think they should. Am I right ?

 Also, another question about the quartering. Looking at them as they are, they look to be OK but wouldn't quartering also depend on the driver, with I think a plastic center, staying in place and not having any slippage on the metal axle that could throw one or more just slightly off?

Carl

[victor miranda]

I drew this up



If your quartering has moved....
the most likely axle to have slipped is the one with the gear.
then the one with the traction tire.

to tell.
set the cranks to point down on one side of the loco and then look the other side.
without touching the dravers.

all the other side should be horizontal and exactly the same amount of horizontal.

here is a thread about it....
http://forum.atlasrr.com/forum/topic.asp?TOPIC_ID=61165

victor

[carlso]

Victor,

I looked at your Atlas link and your diagram. I do understand the 908 quartering idea, I may not be able to accomplish it but I am going to try when I get my new rods, pins, and valve gear. It may become a park display on the club layout but I will have tried to do the repair.

As I said the eccentric crank on the rear engine is loose and the crank can rotate a tad on the crank pin. Is that correct or should the crank be fixed with no rotation on the pin or should it rotate 360* on the pin?

Carl