rrsc mikado leading truck problem?

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hoppercar
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rrsc mikado leading truck problem?

Post by hoppercar » Mon Jul 01, 2019 8:07 pm

wanted to see if anyone else has had a problem with the rrsc mikado leading truck, and what the culprit might be?...when going into a turn, the wheel on the outside of the curve stays in contact with the rail, while the wheel on the curves inside rail, raises high up off the rail... a half inch or more???...never seen anything like that before ?..both axle boxes are the same distance up from the pedestal binder, it's like that whole frame somehow gets in a bind, and is twisted?...

ERIE S-1 BERKSHIRES
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Re: rrsc mikado leading truck problem?

Post by ERIE S-1 BERKSHIRES » Mon Jul 01, 2019 9:06 pm

Me and a friend redesigned the swing link for more movement how tight is the Curve where you trying to go around foot radius is that is the radius of the curve may be too tight

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Fender
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Re: rrsc mikado leading truck problem?

Post by Fender » Mon Jul 01, 2019 9:19 pm

Suspect that the distance between the pivot points at the top and bottom of the swing links is not the same. In other words, if the right and left swing links are closer together (or further apart) at the top than at the bottom, when the truck swings to one side, a wheel will lift on one side. Another live steamer friend had exactly this same problem: one wheel would raise up when entering a curve.
Dan Watson

hoppercar
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Re: rrsc mikado leading truck problem?

Post by hoppercar » Mon Jul 01, 2019 9:43 pm

our track radius is pretty generous...50 to 60 foot radii

765nkp
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Re: rrsc mikado leading truck problem?

Post by 765nkp » Mon Jul 01, 2019 9:45 pm

Had the same problem, fixed it. I have built 2 of these. One of them is well tested for about 10yrs now. Need to machine down the swing bolster a 1/8" step to clear the pilot truck frame. Here's a picture of what I did.

Tim
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ccvstmr
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Re: rrsc mikado leading truck problem?

Post by ccvstmr » Mon Jul 01, 2019 9:58 pm

Hoppercar...will 2nd other comments here. Ran into the same problem with a 10-wheeler pilot truck years ago. The builder tried to shim a turnout guardrail to fix...but the pilot truck was still picking the frog. Laying down on the ground an pulling the loco thru the turnout...I could see the inside radius wheels lifting off the rail BEFORE the frog. The culprit...not enough swing movement on the center. Since the center was an alum casting...the quick repair was to get in there with a Dremel and a burr to provide the necessary swing link clearance.

btw...for proper operation of a swing center...the upper pivot points should be closer together than the lower pivot points. Parallel is "okay". If the upper pivot points are farther apart than the lower...you're not going to get the desired swing action. Carl B.
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hoppercar
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Re: rrsc mikado leading truck problem?

Post by hoppercar » Mon Jul 01, 2019 10:03 pm

if I remember on these rrsc drawings, the swing links, have arcs cut in them

Mikadoguy
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Re: rrsc mikado leading truck problem?

Post by Mikadoguy » Wed Jul 03, 2019 12:59 pm

I will look into the problem. I do know that my dad has redone all of the RRSC Mikado prints. We have made some minor adjustments when we made our new pattern boards. The radius for the Mikado at minimum is 40 on curves.

Steve

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