Kato E8/9 practical minimum radius?

S t e f a n Sep 19, 2020

  1. S t e f a n

    S t e f a n TrainBoard Member

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    Kato specifies 9 3/4" as their standard test or development radius for their N scale models, unless mentioned otherwise in the description of specific models. I don't see anything in their E8/9 web page, but my models are ~10 years old, so maybe something changed.

    The problem:
    I finally got around to correctly seating the MRC decoder in my E9 A unit, which now allows the shell to click into place at the correct height. When running around a 13" radius turning loop of code 55 Micro Engineering flex track, it seems the front stairs on the A unit limit the swivel travel of the front truck, and derail the A unit.
    The B unit is fine. This didn't happen before, i think because the shell was sitting too high due to incorrect decoder mounting. (I bought the A/B set used from eBay; the way the decoder-truck contact springs were seated I'm suspecting it never ran reliably before).
    The track radius might be a little (1"?) smaller than 13", since the 26" total diameter includes a bit of easement. The derailment of the front truck happens with both units fully into the curve, at the point where the baggage car leaves the easement and gets onto the constant radius part of the curve.

    Question:
    What are other modelers here seeing as practical minimum radius for their E8/9 units on this type of track?
    Am i overlooking something? Should 13" radius work for this engine if correctly assembled, and you think I must have some other problem?


    i think right now I see the following options:
    a) rip up the (ballasted) track, increase benchwork width, increase radius to 15"?
    b) increase ladder-truck clearance, by thinning (sanding down) ladder, or bending ladder slightly outwards?
    c) install bridge track; i think I might still have some loose code 40 rail that i could add as guard rail to the existing track?

    I need to raise the layout height in any case, so rebuilding part of the turning loop would fit in with that work (but i would like to avoid ripping up the track if I can).

    A few pictures of the situation before and after derailment, and of the track itself. Sorry about the bad depth of field in some pics.
     
  2. OlyPen

    OlyPen TrainBoard Member

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    The front ladder is the likely culprit here. It's interfering with the front truck's swing.

    Sounds as if you're using a practical minimum radius for N scale. I'd try filing away some of the back of the ladder, thinning its profile, to accommodate the truck swing. You'll need a good set of sharp needle files. Or you can replace the cast-on step with a brass etching.

    Although Kato designs for 9.75" radius, we N scalers typically have space for much broader curves, and good on you for going that direction. The 9.75" is an archaic throwback to N scale's early days in the 1960s, when Arnold-Rapido, Atlas, et al were trying to gain a beachhead for N scale in the model railroad market by any means possible. 1:160 is 54 percent of 1:87.1. So the bog standard 18" minimum radius curve in HO became 9.75" in N scale. Ergo, what you can build in HO, you could build in N with 25 percent of the area: See, our curves can be just as ridiculously tight as HO.
     
  3. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

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    A 10yr old Kato E unit should not have this problem. Are the trucks fully assembled properly? Make sure the plastic parts of the truck are all seated nestled into each other, nothing pushing outward, and that the axles are all seated in the metal contact strip pockets.

    sure, thinning the ladder will help, but there is something else causing this interference.
     
  4. S t e f a n

    S t e f a n TrainBoard Member

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    Oly, Rick, thanks for your input. It sounds like the consensus is that 13" should be large enough, and something else is wrong. Maybe I should disassemble that front truck, although (see below) right now I'm still waiting for the next derailment. I tried the full realistic speed range.

    I'm still unhappy though with the fit of the MRC decoders. I spent a few hours iterating on the speaker in the B unit, thinking it was the high point on the decoder preventing the shell from seating properly. But even with the foam ring below the speaker removed (which makes it sound significantly worse) the shell is still pivoting on something in that area; maybe the diodes (?) right next to the speaker? The front of the shell wants to sit higher than the rear (although looking at it right now it seems fine - maybe the last tweak worked). But at least the unit runs fine.

    The A unit runs without problem without the shell. I replaced the A unit decoder-mounted LED with a 0603 (I think that means 0.6 x 0.3mm; it's really tiny) LED, and now the shell clicks into place with less pressure, and so far the unit still has to derail again. But something about the front truck seems fishy. There is almost zero pivoting freedom left-right on that truck, so the decoder is 'rebooting' a lot. I know my trackwork could be improved, but the B unit doesn't do that.

    What are good sound decoders for these N scale Kato E8/9 units? I saw a video of a decoder installation on this forum, but there it seemed the shells were sitting uniformly high.

     
    Last edited: Sep 20, 2020
  5. MK

    MK TrainBoard Member

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    I have two Kato E8A in Alaska Railroad livery (don't have the B units yet). Both have Digitrax decoders in them and they run fine on my small layout where half my curves are Atlas Code 80 9-3/4 radius. Like Rick said, something is not right.

    I'm not familiar with the MRC sound decoder and whether you need to do any frame milling. But can you remove the decoder and put back the original LED light board? Then run the loco on the same tracks with DC power and see if you get an derailment. Maybe the installation of the MRC messed something up.
     
    OlyPen likes this.
  6. S t e f a n

    S t e f a n TrainBoard Member

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    Thanks, MK. It's good to have actual confirmation that these Kato units have no problem with 9 3/4" radius.

    I bought the units used, with the decoders installed. According to the MRC instructions the decoders are supposed to be drop in, except for some cutting away of plastic nubs where I assume the original Kato lighting board has holes or notches, and the MRC decoder does not.
     
  7. OlyPen

    OlyPen TrainBoard Member

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    Yes, give this a try, Stefan. At least remove the MRC board and see if the swing of the front truck improves.
     
  8. nickelplate759

    nickelplate759 TrainBoard Member

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    I'd take a look at the contact stripsnover the front truck. Might be misaligned
     
  9. S t e f a n

    S t e f a n TrainBoard Member

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    I did clean up the contact springs on the underside of the decoder that make contact with the strips coming up from the trucks. I have not yet had the trucks out. I do not have the original lighting boards for these units. I think somewhere in my box of trains there could be a BN E8A+B set, which is DC. But before I dig that out, I have to fix a minor mishap with my benchwork which made the layout inoperable for now. As I said - or tried to say - in my previous post, after my last round of fiddling the shells sat ok on both units, and the A unit did not derail anymore.
     
  10. Massey

    Massey TrainBoard Member

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    I have had an issue from time to time with Kato engines where the brass strip the trucks slide on slips down below the tops of the contacts for the trucks. This only happens on older units and the newer ones have a clip on bracket that prevents this from happening. Pull the shell and make sure the truck contacts are under and not beside the strips, and make sure they stay that way when the shell is installed.
     
  11. Massey

    Massey TrainBoard Member

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    OH one more thing. I have had to remove the cab interior in the past on some engines as the decoder's LED gets in the way and causes the interior to bind the trucks. Just another thought that could be an issue.
     
  12. S t e f a n

    S t e f a n TrainBoard Member

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    Thanks, Massey! The spring contacts on the decoder had not been bent downwards when I received the units, that's why I think they never really ran. After every shell removal and reseating I do check that both trucks make contact.

    I did remove the interior (really more a light shield) on the B unit, since it collided with the decoder board itself. On the A unit the shield/interior had already been modified to avoid collision with the LED, but I replaced the LED with a much smaller (0603 size) one anyway.
     

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