Bettendorf trucks for Hopper Car

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Re: Bettendorf trucks for Hopper Car

Postby ctxmf74 » Mon May 23, 2016 5:34 pm

Looks good. I wouldn't widen the trucks, just change the inside face and bearing holes so the axles fit right. Many model trucks are too wide and that makes it harder to build a scale proportioned car.....DaveB
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Re: Bettendorf trucks for Hopper Car

Postby Richard-B » Mon May 23, 2016 5:40 pm

ctxmf74 wrote:Looks good. I wouldn't widen the trucks, just change the inside face and bearing holes so the axles fit right. Many model trucks are too wide and that makes it harder to build a scale proportioned car.....DaveB
I 2nd that...
In order to accommodate non-prototypical wheel treads... most model trucks are grossly over-wide.
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Re: Bettendorf trucks for Hopper Car

Postby TTTerrific » Mon May 23, 2016 6:59 pm

I have looked and looked at this "problem" of too-wide trucks for some time. A number of years ago I purchased quite a few Kemtron cast brass ASF type freight trucks in TT. They look great and roll every bit as good as they look. However, the castings on the truck frames are too wide. I measured a series of Grandt Line HO trucks and found them to be eight feet wide at the widest point which is right at the projection of the bearing wheel cover on the bottom of the wheel bearing. The TT scale Kemtrons varied between nine feet nine inches to ten feet wide on the same measurement line. Given the fact that nearly all period freight cars from around 1920-1960 or so ranged between nine and ten feet in width, in TT (except maybe for HP trucks), you lose the 12"-16" each side overhang of the carbody when viewing the car from the end.

I built three scale PFE reefers that turned out very well (9'4" width), but they honestly look stupid due to the over-wide trucks. Yeah, I might have to "scale-up" my carbodies all around by about 5% or so, but then I'm sure I'll have other problems--proportion wise. :(
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Re: Bettendorf trucks for Hopper Car

Postby ConnRiver » Tue May 24, 2016 11:21 am

Dwayne, those aren't Fox Valley C72 wheel sets, are they? If not, perhaps the FV wheels might fit?

What are thoughts here about C72 wheel sets becoming the defacto standard (voting by pocketbook, so to speak) for TT scale? Will it happen, or will variety of widths continue to prevail?

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Re: Bettendorf trucks for Hopper Car

Postby dwyaneward » Tue May 24, 2016 1:56 pm

[quote="ConnRiver"]Dwayne, those aren't Fox Valley C72 wheel sets, are they? If not, perhaps the FV wheels might fit?/quote]

Nope, from Germany. Unknown if Fox wheel would work, no data on their site to determine.

I have push the journal face back as noted above, without widening the overall 106" truck width.

My initial design was based on NMRA data by converting HO journal face to face width to TT scale, since NMRA does not have data for TT scale, that came out to .601" between journal faces. Trucks on the PV box cars have a .637" between journal faces with a lot of axle movement. I readjusted base on converted NMRA N scale dimension for this round for a .625" distance.
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Re: Bettendorf trucks for Hopper Car

Postby MacG » Tue May 24, 2016 3:14 pm

Here is the European norm for the axles and trucks. Please check the dimensions of your axles, but they should fit to 12mm gauge (Spurweite).
http://www.morop.org/de/normes/nem314_d.pdf
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Re: Bettendorf trucks for Hopper Car

Postby Richard-B » Tue May 24, 2016 4:11 pm

MacG wrote:Here is the European norm for the axles and trucks. Please check the dimensions of your axles, but they should fit to 12mm gauge (Spurweite). http://www.morop.org/de/normes/nem314_d.pdf
..and here is an excerpt of the NMRA equivalent.
NMRA TT-scale.pdf
NMRA TT standards excerpt
(82.64 KiB) Downloaded 369 times

Note that there appears to be no NMRA spec for the 'L' dimension... perhaps as NA wheel sets often do not have a protruding hub.

In any case; The NMRA TT back-to-back is 0.415...
plus 2x the wheel 'Code' (width in 1000ths of an inch) would give the nominal (-.002 / +.008) wheelset dimension (over faces) that needs to clear the inside of the truck journals:
Code 100: 0.415 + .100 + .100 = 0.615
Code 95: 0.415 + .095 + .095 = 0.605 (GCR US wheelsets)
Code 88: 0.415 + .088 + .088 = 0.591
Code 79: 0.415 + .079 + .079 = 0.573
Code 72: 0.415 + .072 + .072 = 0.559 (Fox Valley - TT Fine)
Note that the NA prototype wheel thickness is 5-1/2 inches... which would be Code 46 in Proto TT!!!!

Axle length is the next variable!
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Re: Bettendorf trucks for Hopper Car

Postby ctxmf74 » Tue May 24, 2016 6:09 pm

"Code 79: 0.415 + .079 + .079 = 0.573"

That's about the size of the wheelsets in my HP trucks, they are on .720 long axles . Their unique design lets them measure about scale width ( about .77" over the bearing covers). Their inside measurement is about .620 or .022 clearance between wheel face and sideframe per side. .....DaveB
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Re: Bettendorf trucks for Hopper Car

Postby modorney » Thu Jun 02, 2016 10:53 am

Dwayne -

I'm eagerly awaiting the trucks :)

http://www.shapeways.com/shops/kdmodels ... 120%29&s=0
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Re: Bettendorf trucks for Hopper Car

Postby dwyaneward » Thu Jun 02, 2016 6:30 pm

modorney wrote:Dwayne -

I'm eagerly awaiting the trucks :)

http://www.shapeways.com/shops/kdmodels ... 120%29&s=0


Waiting on second run to see how axle fit......
Holiday weekend must have extend production cycle @ shapeways
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