Shay 'surge' on incline

 Jarrell,

I am not an expert, but I had that with a DCC run loco. Everytime it went down a grade, it began to lurch. It stopped when I switched off the back EMF. I assume it was the cars "pushing" the loco down the grade. Just try it with out this feature.

I get that all the time with my Proto 2000 diesels on my 4% grade with 10 cars in tow... Only Atlas units work fine. I don't think my units have BEMF though... I'll be watching this thread carefully to see if I can benefit from the fix!

   I suspect that ther is too much end play in the worm shafts and that is what is causing the 'surging' when decending a grade.  Wht is happening is that the worm moves and locks up against the drive gear, then 'kicks' back.  Adding 'thrust' washers to the worm shaft will resolve the problem.  This happens a lot with diesels as well when decending a grade with a heavy train pushing from behind.

   If you have a DCC decoder that is using BEMF, that might do it as well.  Turning off BEMF will confirm if the BEMF setting is too strong.

Jim

DCC or DC doesn't matter, you have a problem in the drivetrain of the loco.  When the shay is going uphill and pulling a string of cars its fine because the play or slop in the drive mechanism is 'out'.  When the train goes down hill, the play in the drive train is causing the train to change speeds, then when the mechanism catches up, the loco speeds up until the you reach the other end of the play in the drive and the process repeats.

 I'm not familiar with the Bachmann shay drive mechanism, but usually the place to look is the worm gear at the top of the gear tower.  If the worm gear can move back and forth between the thrust washers and bearing on each end of the worm gear, that's the culprit.  The fix usually involves adding some KD washers between the worm gear and the bearing until there is no more horizontal movement.  This should be done on both gear towers.

Get rid of the play and you will have solved the problem.  Remember that DCC and BEMF can't make a bad running engine run good, it maybe able to mask some things, but if there's a mechincal problem it needs to be fixed first.

You are indeed, Sir, "smarter than the average bear!"

jrbernier

   I suspect that ther is too much end play in the worm shafts and that is what is causing the 'surging' when decending a grade.  Wht is happening is that the worm moves and locks up against the drive gear, then 'kicks' back.  Adding 'thrust' washers to the worm shaft will resolve the problem.  This happens a lot with diesels as well when decending a grade with a heavy train pushing from behind.

Jim

 As ol' Gary Cooper used to say, "Yep!"

I have used thin brass washers from NWSL to eliminate end play. With a pair of small wire cutters, I snip one side of the washer and slip it into place between the worm and motor.

The gear on the motor is a worm. The worm drives a worm gear. Check with NWSL gear information.

Also, watch out for cracked plastic gears on the Shay. Some people have seen this happen to their Spectrum Shays after running for a while.

Your mileage may vary.

You did not mention if the loco is running with a DCC decoder, under DCC control or DC control, DC and no decoder?

Rich

 Sorry 'bout that.  Yes, the engine has a dcc soundtraxx decoder.

The previous explanations involving washers and the worm gear sound very plausible to me, though I have no experience in this area.  I appreciate all those who have responded.  I went back and took more careful measurements of the incline height and length and it works out to more like a 5%.  That is getting pretty steep.  I also tried several other engines, both diesel and steam, P2k, Bachmann etc. and the shay is the only one that exhibits this behavior.

Thanks again for the answers!

Jarrell

richg1998

You did not mention if the loco is running with a DCC decoder, under DCC control or DC control, DC and no decoder?

This is very common for Bachmann Shays.  Lots of them do this, sometimes right out of the box.  It may be a sign of trouble coming later for the drivetrain gears.  There are replacements available if you eventually need them.

A 5% grade is pretty steep.  I have a grade about that steep and my Bachmann Shays can only pull about 7-9 cars.  Watch out for vertical kinks ... changes in grade at the top or bottom of a grade.  The Bachmann Shays do not like vertical kinks one bit.  You need to smoothly transition from 0% grade to 5% grade over a bit of distance and avoid doing it all at once (a kink).

Marty    www.oakhurstrailroad.com 

Oakhurst Railroad Engineer

A 5% grade is pretty steep.  I have a grade about that steep and my Bachmann Shays can only pull about 7-9 cars.

Five percent wasn't very steep for a prototype Shay--or any kind of a geared locomotive for that matter--and if your B'mann loke is lugging 7-9 cars up your 5% grade it seems to me that you are getting good service from that particular locomotive.

Oakhurst Railroad Engineer

This is very common for Bachmann Shays.  Lots of them do this, sometimes right out of the box.  It may be a sign of trouble coming later for the drivetrain gears.  There are replacements available if you eventually need them.

A 5% grade is pretty steep.  I have a grade about that steep and my Bachmann Shays can only pull about 7-9 cars.  Watch out for vertical kinks ... changes in grade at the top or bottom of a grade.  The Bachmann Shays do not like vertical kinks one bit.  You need to smoothly transition from 0% grade to 5% grade over a bit of distance and avoid doing it all at once (a kink).

Marty    www.oakhurstrailroad.com 

 

Thanks Marty.  I'm already thinking of ways to bring that 5% grade down to 2 or 3%.  I'll lose some of my interchange track below, but that's a price I'm willing to pay.  5% is just too steep.  BTW, that is one beautiful layout you've got!  Anyone who hasn't seen it should go to oakhurstrailroad.com.

Jarrell

 

 

Jarrell, I would not want to rob the nice Shay of a chance to show off its unique design capabilities if I had one.   Instead, even if the model, itself, had to struggle a bit with three or four cars, I would keep the intended path as steep as practicable so that the Shay could be seen, and used, doing what it was designed to do.  Note that they often worked tracks, nasty undulating and weaving tracks that were temporary in nature in the woods, and that would rise up on grades as steep as 9-12% in some extreme cases.  So, I would urge you to find a way to fix the engine so that it runs smoothly, but still on a very typical 5% grade.

Just my thoughts.

-Crandell

selector

Jarrell, I would not want to rob the nice Shay of a chance to show off its unique design capabilities if I had one.   Instead, even if the model, itself, had to struggle a bit with three or four cars, I would keep the intended path as steep as practicable so that the Shay could be seen, and used, doing what it was designed to do.  Note that they often worked tracks, nasty undulating and weaving tracks that were temporary in nature in the woods, and that would rise up on grades as steep as 9-12% in some extreme cases.  So, I would urge you to find a way to fix the engine so that it runs smoothly, but still on a very typical 5% grade.

Just my thoughts.

-Crandell

Crandell, the area that the shay is intended to work in the 'woods' is directly over my hidden staging/interchange track, thus I have to have at least a 3 inch clearance.  Luckily, the staging track is dropped down below 'normal' grade on the layout about an inch so the present height of my woods gives me the right amount of clearance.  That's why I'm reluctant to drop the area that contains the 'woods' track down anymore.  I know I must have sat there an hour looking at the area, thinking of a way around it but don't see one...     I know also, that I'm not good at getting into engines and making modifications.  I usually manage to break more than I fix     BUT... I have a friend that IS good at that type work.  He's installed decoders and speakers in his Shay....... so maybeeeeee........  

Thanks for your input.  As usual you're most thoughtful and helpful.

Jarrell

Jarrell

I have 3 of those Shays, they all have done the surging out of the box, I've had them 3 years with no problems, so what you are experiencing is not necessarily a symptom of a future mechanical breakdown. I operate a proto speeds, usually with 3 - 4 ore cars (Tichy and MDC chip cars). This "surging" does occur but not in a way that bothers me (loaded cars seem to keep the surging down to a minimum) and my visitors have not commented on it. I read of fixes on other forums but they didn't seem to me to be viable.

I hope it works out for you, does this have factory sound? If so, how is it?

GS 

He mentioned it had a sountraxx  installed which is what bachmann uses for sound.  I have one and love the sound.  It only has an hour or so on it since it doesn't match my layout.

R. T. POTEET

--and if your B'mann loke is lugging 7-9 cars up your 5% grade it seems to me that you are getting good service from that particular locomotive.

7-9 cars is just right for me, so I'm happy with the pulling power. 

However, I have two Bachmann 3-T Shays and over the last several years I've had to replace 4 of the trucks due to cracked gears on the side shafts. I suspect that the heavy loading due to the steep grades makes the gears more likely to crack.  You can order replacement trucks from Bachmann (if they are in stock), or the new gears from NWSL, if this happens to you ...

Jarrel,

Model railroader made a point of advising against dis-assembly of the shay in their review of the loco on its initial release. Bachmann does not recommend taking the shays apart either. I have corresponded with B'man about other shay issues and was given this advice directly from them.

It seems they are very hard to get back together correctly.  I have heard stories from other modelers that tried dis-assembly and the universal sentiment was that they "don't run as well as they did before I took them apart"  Whale the skill of the modeler is always an issue with anecdotal evidence, might still give you pause...Perhaps there are others who have had more sucess.....I have removed the trucks on mine to install sound but haven't ventured farther into dis-assembly.  Would still like to know how to oil the internal gearbox......

 I have three shays (five years of moderate use on 2% grades) and they still run well.  As for pulling, we once had a showdown between a shay and a BLI NW 2-8-8-2 (no traction tires) to see which loco could out pull the other.  The shay lost by two cars.....(my money was on the shay).  Judging from what others are saying, sounds like I should be watching out for cracked gears (none yet)....

 My two cents,

 Guy