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Trains surging when descending inclines


Mutley

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Hi all, I wonder if somebody might be able to help with a problem I'm having? 

 

My layout is a folded figure of 8 using Kato Unitrack, with double track inclines using the additional 'gradual incline' piers set, so a nice gentle slope to get trains up and down again - see the attached plan.

 

I've got feeders all over the place, track is nice and clean but I'm having real problems with a few trains when they are descending the inclines.

 

As soon as the train is fully on the downward slope, running at about half throttle, it will almost stop and then increase in speed again and this repeats until almost all of the train is off of the incline.  

 

I had this with a previous incarnation of my layout (Kato E2 Asama in particular) and the problem now only happens for a few trains, all of which run very smoothly on the flat.

 

In particular, my new Kato E351 12-car and E257 Odoriko 9-car sets do this, as well as my Series 800 6-car set and Nambu 6-car Series 205.

 

I've carried out some tests and found that increasing to 75-80% throttle makes the effect less noticeable but the trains are running way too fast for my liking at that point.  I've tried reducing the number of cars in the set to see if there is any relation between the paritcular model and the number of cars and I brought the E351 down to 6 cars with no noticable improvement.

 

I have feeders top and bottom of the inclines and tried disconnecting each in turn to see if it that was having any impact and no change.

 

I wondered if there was some common factor in the mechanisms and whether the PWM (or whatever it is!) in the Kato SX is doing something to try to compensate with the natural speed-up as the train starts to descend.  Unfortunately, I don't have any other controllers to try.

 

As you will see on the plan, the incline at the top of the plan is completely straight and the affect is much more pronounced there than on the other behind Station B.

 

My Kato E233's, E231's, E259, E353, E261 and Tomix Revalty, Spacia are not afflicted by this.

 

Any thoughts on what might be causing this would be very welcome as I've finally come up with a layout plan that really works for me.

 

Thanks in advance
Mike

Kato Layout V48.2.bmp

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gavino200

I've had trouble with this before using the "gradual incline" pier set. The gradual incline is still a fairly steep incline. Some locos handle it better than others. Many speed up a lot on the way down. Some slow down quite a bit on the way up. There are a few fairly feeble locos that couldn't make the incline at all. It's a pity, because inclines like yours look great and facilitate some very nice track plans.

 

I eventually just got tired of this issue. My current layout is going to have tracks that are level, but a ground level that will vary in height.

 

I think the only other way to alleviate the problem is to get more piers and sand them down to custom heights so that you can make the incline more gradual.

 

Yes, it's frustrating that Kato sell a gradual incline set that is still not gradual enough for many locos. And many people aren't bothered by the speed alterations. But alas it is a fact.

Edited by gavino200
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Most likely due to play in the mechanism. (The amount of movement the gears and wheels will turn without the motor moving) When going up, the extra movement is taken up as the weight of the train is trying to slow it down. (The motor and gears have a constant bite.) When going down, the train weight is trying to speed it up. This pushes the mechanism to the other end of the slop until the motor catches up and the gears bite again. The motor catches up, and creates the slop again. It repeats so you get the lurching effect.

 

Update

 

It seems a common problem with the worm gear in the trucks having a lot of back and forth movement on the drive shaft. Some suggest adding thin nylon "thrust washers" to each end of the worm gear to fill out the space in the housing. I would also say that the trains you are having issue with are all relatively old tooling. (moulds designed a while ago) Even though the E257 Odoriko is a new release, the chassis is quite an old design, along with the other models you have mentioned. Many commented on its lack of DCC friendly design like all newly tooled models.  All have had subtle updates to light units or liveries but the mechanisms have been left relatively unchanged.

Edited by Kamome
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Thanks for your replies.

 

I did actually try changing one of the inclines so that it was steeper by eliminating the 'in-between' piers from the gradual set, the theory being that the whole train would not be on the incline, just to see what happened.

 

The E351, no difference, but the E257, sailed down it without a problem! 

 

I've also got a 7 car E257 Azusa that didn't have the problem on the gradual incline, so that probably does point to an issue with the individual mechanisms and I might look into the washer solution you mentioned @Kamome, but suspect it will be a bit too fiddly for me!

 

I might try stretching the incline along the whole of the back of the layout as I do have room by cutting a few temporary wooden supports, just to see if it makes any difference.  I could, I suppose, put the whole 'back straight' behind a backscene so that I don't have to watch the trains lurching down there!

 

Failing all of that, I expect I'll end up with your approach @gavino200 and eliminate the inclines altogether, which would be a shame.

 

Thanks again

Mike

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Takahama Trainwatcher

Have you tried running 2 trains simultaneously off the same Kato SX to eliminate the controller as doing something weird? (If your problematic train slows on the descent, while another train elsewhere continues on as normal, I guess that would exclude your hypothesis about the controller compensating.)

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Most likely your layout is way too large for the SX. There is a possibility that the voltage drop (due to distance from the SX) is marginal and the load from the

train is causing the Back EMF to fight with the motor.

 

To verify is this is the issue. Disconnect your SX and position it by the incline and use alligator clips to supply the power to the rails there.

It should resolve the issue as the distance from the Sx and the incline is reduced.

 

Inobu

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Thanks again for all of your suggestions.

 

I tested @inobu's idea first and connected the SX to an isolated section of track starting before and finishing after the incline and no change in behaviour, so I concluded my problem is probably not being caused by any size limitation with the SX.

 

I then tested @Takahama Trainwatcher's suggestion of running a second train under control of the same SX, to prove or disprove the theory that the SX might be doing something peculiar.  The second train continued to run without any change in behaviour, whilst the E351 lurched down the incline, so that says to me, not the SX.

 

I then made alterations to the incline to see if inserting additional piers in between the normal and gradual incline pier sets would make a difference.  The E257 descended the incline without a stutter and interestingly, went around to the other side of the layout and descended the (unaltered) ‘back straight’ incline cleanly as well! 

 

The E351 as a 12-car train still lurched, although taking off the 4-car add-on set, sorted the problem, so I think this gives weight to @Kamome's theory regarding the mechanism and movement in the worm gear.

 

After putting everything back to the way it was before I started experimenting, the E257 ran up and down both inclines without issue – very odd!

 

I have decided to follow @gavino200's example and spent some time today taking out most of the viaducts (new plan attached) and have ordered some additional track pieces to carry a single-track viaduct over the main lines to connect up the container terminal branch again and to give a pair of dedicated platforms at the main station.  This will be mainly for the 6-car Nambu Series 205 and E233, as well as freight trains, all of which I’ve tested will negotiate this steeper incline comfortably.

 

The E351 will not take this route, or if it does, I will close my eyes whilst it whizzes up and over, at least it won’t be lurching on every circuit now!

 

I timed the E257 at 46 seconds around the circuit at medium throttle, which is a really decent run, and everything is running very smoothly.  The layout feels much more open without the viaducts everywhere and I think this may have been a blessing in disguise!

 

Thanks very much for your input, I’ll start a thread in the Layout Building section shortly if people would be interested to see how the new layout goes.

 

Mike

Kato Layout V48.6.jpg

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Yavianice
On 4/22/2022 at 5:59 AM, inobu said:

There is a possibility that the voltage drop (due to distance from the SX) is marginal and the load from the

train is causing the Back EMF to fight with the motor.

 

quite interesting hypothesis. Would you suggest running feeders to separate isolated sections instead of just having one track with multiple feeders?

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1 hour ago, Yavianice said:

 

quite interesting hypothesis. Would you suggest running feeders to separate isolated sections instead of just having one track with multiple feeders?

Yes, when you isolate the layout into sections then the power can be relegated to each section as the train transverses the layout.

 

Inobu

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