3-truck MDC Shay tender close-coupling

Discussion in 'Scratchin' & Bashin'' started by FrankBlunt, Feb 20, 2004.

  1. FrankBlunt

    FrankBlunt New Member

    I am looking for information regarding close-coupling the MDC Shay 3-truck tender. That is to say, using a shorter drawbar to move the tender closer to the locomotive. The MDC Shay Handbook shows examples of Shays with the modification, but doesn't have any details. So I am wondering if any of you have performed this and can make me aware of any pitfalls. BTW, this is an HOn3 model. Also, I won't be carving it though any 18"-radius curves. The minimum will be about 30-36" radius.

    Here are my assumptions thus far:
    1) In addition to making up a new shorter drawbar, I need to use shorter line shaft universal sliding couplings. Also, shorten the power shaft to the tender power truck.
    2) I need to shorten these shafts in such a way that they remain more or less parallel to each other as the engine moves through curves.
    3) The new drawbar should pivot both at the locomotive and tender ends - unlike the standard MDC setup which pivots at the locomotive end only.

    As to the drawbar itself, I am curious as to what sort of arrangement the prototype used.

    Thanks in advance for any help, advice, sympathy or condolences you have to offer.
  2. Matthyro

    Matthyro Will always be re-membered

    Welcome to the Gauge Frank. Hope some of our logging community can be of help to you re: the drawbar modification.
  3. Ray Marinaccio

    Ray Marinaccio Active Member

    Hi Frank,
    I built a 3 truck Shay years ago for a Friend. Had to stop and think how the original drawbar was.
    I haven't done the modification you want to make, but you got me thinking of how to do it.
    The biggest concern I would have is whether the tender would track right with a drawbar with two pivot points. It may tend to twist sideways or woddle back and forth. To remedy that you could install centering springs on the drawbar.
    I've heard that some people don't install the center driveline to the tender and use the outer lineshaft to power the tender.
  4. neilmunck

    neilmunck Member

    I don't think there will be a problem using a draw bar with 2 pivots. The bachmann three truck shay uses a drawbar with a pivot at each end and doesn't have a problem waddleing (mine is 5 months old).

    I would be suprised if using just the lineshaft to the back truck would work. On my 2 truck MDC loco they don't work very well. Because the gears aren't bevelled like they should be (mechanically speaking) they have a tendancy to jump. Having said that - some of the problems are because the line shaft and the drive shaft are working against each other.

  5. fifer

    fifer Active Member

    Neil is correct the problem with MDC is getting the bevel gears syncronized.
    On all the ones I did i removed all the shaft bevel gears but one ,to turn the shafts and just used the inner drive to power the loco.
    This makes the engine much more reliable and user friendly.
    You should not have a problem shortening up the 3rd truck.
    PS I would also recommend making phospher bronze electrical pickups for each wheel set and hard wire them to the motor ,as MDC's electrical pickup system stinks.
  6. FrankBlunt

    FrankBlunt New Member

    Thanks for your input, guys.

    Regarding the "bevel" lineshaft gears, MDC recommends drilling out one of the gears on each truck so it merely spins on the shaft, which should resolve the backlash timing problem.

    neilmunck, a question about your Bachmann Shay. Looking at photos, it appears that it is driven by the lineshafts, like the prototype, instead of separate driveshafts like the MDC. Have you encountered any problem with the sliding shafts binding up under torque, like negotiating an uphill sharp curve whilst pulling a heavy load? I have heard that the prototype tended to plow straight on instead of turning, because the shafts didn't slide.
  7. neilmunck

    neilmunck Member

    My bachamnn shay performs absolutely beautifully. You are correct in saying thet it is powered by the line shafts and that there are no other mechanical parts under the loco. It looks fantastic and makes the MDC shay look a bit silly.:(

    Wiith regards to what you were saying about shays nosing in I have never noticed this happening. One thing that did happen was that when the loco went from level to a downhill grade whilst turning left (as happens at one point on my layout) then the loco always derailed.

    At first I thought it was because the coupler box cover was preventing the front truck from tilting downwards but when I trimmed the coupler box to get round this it still derailed.

    I found that the bolster on the front truck was twisted so that the front right wheel didn't touch the track. I dismattled the truck and tried ot twist it level but that didn't work as the plastic is very springy. In the end I enlarged the mounting pin hole for teh side frame on one side of the truck. The pin is round on the gear side and square on the non grea side so I enlarged the round hole as that was easiest.

    This allowed the truck to sit level and not derail. I found that all the trucks on my model had the same problem but no badly enough to cause problems.

    Did anyone else have this?

    Anyway, it goes like a swiss watch now.

    I agree with mike - I replaced trimmed the MDC contact pads and soldered on phosphour-bronze wires with electrical wires soldered to the motor. It made the model much more reliable.

    I am interested to hear about drilling out some of the gears on the MDC lineshaft to stop the gear clash. It sounds a great idea but how do you stop the loose gears from wandering along the shaft on the side of the trucks?


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