For you who are always bellyaching that we in 2 rail can't have correct accurate Steam Loco Driver Spacing, I beg to differ.

Below is a shot of one of my locos with on the money driver centers. It was necessary to dress just a few .000" off each flange to do it.

I just wanted to show that with a bit of finesse, all the whining isn't necessary.

I realize that most of you would rather whine about what isn't, but here's a better view of the spacing of the 4 sets of drivers, showing the correct axle spacing!




This view includes owner added details including added Baker valve gear. Notice the correct spacing between the first 2 axles.

Ed R

Eddie,

Who's doing all the belly-aching and whining about driver spacing??



Matt Forsyth

Modeling the D&H Penna. Division/
Erie Jefferson Division, Fall 1951

Ed,
What was the 'before' axle spacing?

Thanks,
Matt

Matt F---------

all the people who are always crying that the axle spacing is incorrect because of either the locos are made for the 3 rail group and the either too small dia. wheels or the extra large flanges, including the NMRA std. flanges.

Matt H--------

On this model, the axle slots are made to scale from the available plans showing axle spacing of the real one. There isn't a before / after. Only as made from the plans.

Yes, the flanges are closer than in real life, but that is because of the standards we follow, as set by NMRA. However, the wheel dia is w/in tolerance, which works for me.

Again, as stated above, I just wanted to show that it can be done.

Ed R

Very nice work, Ed. I take it you scratchbuilt the loco frame?

For those who may not know, NMRA standards call for deeper flanges than prototype dimensions. Therefore, some types of steam loco models using wheels made to those standards may require either a smaller overall driver diameter OR a stretched driver wheelbase to avoid flanges interfering with one another. We know the commercial builders do one or the other, if not a bit of both practices.

Without looking it up, I think prototype flanges are approx 1" deep, or .021" in O scale. One of my 2-8-4s has a lead truck equipped with an old Lobaugh wheelset, originally made with the pre-1955 2R flange dimensions--noticeably deeper than flanges made today. Before the change, 2R flanges were about 1/16" deep; half the depth of tinplate flanges but a long way from being prototypical.

In grinding down the flanges on that wheelset to match our more modern wheels, I overdid it and produced a wheelset with flanges very close to prototype depth. That loco has operated without derailing on four different layouts in addition to my own, which proves the point that a loco made with accurate flange depths can operate on (reasonably well-laid) model RR track.

Now Ed didn't state that above point exactly as I did. But it is one thing to build a model and another thing to build a model that operates well. Some viewers of the various threads may have missed the distinction, which I think arose in discussions regarding models built to P:48 dimensions.

Prototype locomotive designers specify minimum curves for operation. It logically follows that an O Scale model built to prototype dimensions in ALL respects will be limited to the equivalent prototype minimum radius. In most cases, steam road locomotives generally require a 20-degree minimum curve, = to a 6' radius in O scale. So if a modeler wants to operate a model of a large loco on an unrealistically sharp curve, it is obvious that some compromises to prototype dimensions will be necessary.

But as Ed has pointed out to us, flange depth or driver spacing is NOT necessarily involved. I think one appropriate factor to consider is tread WIDTH, wider treads being a prototypical method used on some types of locos for short-radius operation. Another possible compensation is driver sideplay: perhaps narrowing frame width or narrowing the outer thickness of bearing boxes to increase driver sideplay.

On some locos, truck wheelbases, wheel diameters, or clearances around cylinders may need to be altered to achieve reliable operation. As an example, the prototype Pennsy K4 has a "close-coupled" (short wheelbase) lead truck with 36" wheels. Most commercial models of the K4 came equipped with 33" wheels to provide a little more clearance at the cylinders. Some models based on 3R designs (such as Weaver & Williams) extended the overall length of the loco forward of the drivers to provide additional space for the lead truck wheels between drivers & rear face of cylinders and between the front face of the cylinders & the rear of the pilot. Accordingly, the lead truck wheelbase is stretched on such a model as well.

The above are statements of fact. I don't see that anyone is "whining" that some compromises must be made IF one wants to operate models of certain locomotives on curves proportionally sharper than the prototypes could negotiate. If some people are content to operate models of small locos for a more "realistic" layout, more power to them. But I think those of us who want to run big locos on small curves are willing to accept the necessary compromises--without whining.

woody

quote:

Now Ed didn't state that above point exactly as I did. But it is one thing to build a model and another thing to build a model that operates well.

I'd like to thank you for your keyboarding excellence. something which I definitely do not have.

FWIW, the wheels I used to use when building steamers were cast in England, and machined to British fine Scale standards, quite close to our .145" standards.

The frame was not scratch built by me, but was made by a local machine shop for me and used as a master for cast urethane frames. Yup plastic loco frames. "OH Golly, what's the world coming to!! VBG I wanted to do this loco, basic R-T-R but as accurate as possible. the buyer could dress it up to their definite needs. This is definitely NOT a shelf queen, but a regular runner on the layout. I got the boiler shape and axle spacing pretty darned close, and the pilot truck is as close to accurate as possible also, using a very un-orthodox mounting, as described to be by Pecos John Smith some years back. It allows close wheel spacing to the cylinders on our 60" 5 mile an hour trackage [real limits] [and we complain about the "L" operators]

The photo supplied is the work of one purchaser who I believe to be a very discerning modeler. who thought enough of my efforts to purchase one sight unseen, keep it, and add the details to his satisfaction. That in itself makes me feel good. But. again, my original point is that we can have rather accurate models, using a little extra finesse, here and there, and shouldn't break any bank in doing it. Obviously, 3 rail is a totally different story, as there just enough fudge room with their wheel system.

Oh, by the way, the side rods are one piece, not articulated, and the cylinders aren't really over-wide, either.

Ed R