loco curves

[Terry Toenges]

Trainman - I've got an O27 General. It would give you a heart attack if you ever saw that.

[Trainman203]

O27 is a different and very cool game.  I had the Santa Fe Hudson when I was a kid . A scale 100 mph around a 13" radius curve! And it stayed on the track!!!!  We'd pile Lincoln logs on the track and plow that baby right through them. We were running the Mexican Border!!! I don't think I've hsd as much fun with my Serious Model Railroad as we did with that indestructible Lionel stuff!!!

[ACY]

If I remember right the Bachmann Catalogue does give minimum radius curves for each locomotive.  Since in a given scale a locomotive is a locomotive it should work on the other brands of the same locomotive.

This is generally not the case as often some manufacturers alter their locomotives to run on tighter radius curves, such as the Bachmann 4-8-4 N&W J class which has a ton of "play" (side to side) to allow it to make sharper curves than any other manufacturer's model of the J can negotiate.

[ebtnut]

We have to make compromises and trade-offs in the hobby all the time.  Dealing with curves is perhaps one of the biggest trade-offs.  The prototype describes curves in degrees.  A ten degree curve is considered sharp for main line operations.  Most main line steam locos could negotiate a 20 degree curve at very low speed (such as a turning wye).  The conversion formula for degrees to radius is:  5,730 divided by the degrees of the curve.  Therefor a 20 degree curve has a radius of 286.5 feet.  In HO this equates to 39.5 inches radius.  Most of us don't have the space to build a layout using that as a minimum radius.  So, models are compromised in design to handle much tighter curves so we can build a practical layout.  I would note that a lot of the brass imports of larger steam locos had minimum radii of 24 to 30 inch radius.  There were compromises in mechanism design such as longer wheelbase lead trucks, blind drivers, open space above the trailing truck where any ash pan should be, etc.  You work at your own comfort level.  Oh, by the way, that 10 degree main line curve equates to a 79 inch radius curve.

[Terry Toenges]

I used to do barricades and put autos across the track and crash into them too when I was a kid with O27.

[bbmiroku]

ebtnut...
about the 'compromises' we as modelers make...

Blind drivers are a prototype thing.
I have a few books on steam engines (not just trains but actual engines as well) and I came across a picture of I think it was a 2-6-2.  The middle pair of drivers was blind.

[Trainman203]

There were blind drivers on a few prototype long wheelbase steam engines.  I'm not going to research a thesis, but my aging memory seems to recall the UP 4-12-2 as one example.

[Trainman203]

The otherwise nice new 2-8-2 and 4-6-2 are compromised for train set level operation in a few ways.  The pilot is well over a scale foot above the railhead to accommodate crummy unlevel track.  The closest possible cab/tender coupling is a good bit further apart than the former realistic Spectrum close coupling to stop complaints about engines unable to negotiate near 90 degree corners, and the trailing truck has so much unprototypical see-through clear air space around it, you could drive a car through..... all to allow toy train level trackwork.

I mostly like both of these engines, their operation is flawless, the motor control CVs are near perfect from the factory, compared to Spectrum models which should have been better.  The sound Value chuff is well timed compared to before.  But these clearance compromises to work on toy train track drive me quite nuts. I find myself avoiding viewing  these models from certain angles to not see the compromises.

[ebtnut]

Agree that blind drivers are relatively common in the prototype, especially for locos intended for branch lines, narrow gauge, and other instances where sharp curves are common.  Even the Pennsylvania RR's big 2-10-0 decapods were originally built with the 3 center driver sets blind.  Many were later modified to only have the center driver blind.  But many models have been made where the prototype did not have blind drivers but the model does in order to negotiate our super-sharp curves.  It's a trade-off and that's OK.  I would note that in almost all cases the tires on those blind drivers were about an inch and a half wider than the flanged ones in order that the wheel wouldn't drop behind the railhead on a minimum radius curve.   

[jward]

Personally, I understand the compromises that have to be made. And i'm glad for it. The choice often comes down to having sharp curves or not having a layout at all. As long as the locomotive operates well and doesn't derail itself or whatever is coupled to it, I can deal with the overhang. it's better than having 30 feet of straight track along the back wall and being bored to tears.