Wow

It is hard to believe that is to scale. The turn out angles and radius curves of the wye seem very sharp.  If you were to model this with commercial turnouts then I would look for a Peco short radius or #4 or sharper handlaid point as tight as the loco can handle. 9”-15” radius might work with a 0-4-0 or 44 toner.

Try some tests! Looks like fun. 

The drawing

looks like an insurance or other infrastructure map and not an engineering map so the turnouts are not drawn to scale. Forty foot freight cars have no problem going around 90 foot curves ( about 12 inch radius in HO so I'd start there and see if that would work for a model. Instead of a frog number I'd just use a 12 inch radius for the diverging route and make the whole turnout a curve( like they did with trolley tracks in cities.. These curved spurs into industries were quite common in city industrial areas in the old days. Even Lodi which as a pretty small town back in the day had a couple of tight spurs on the CCT trackage. I'm using 24 inch to model them on my S scale layout which translates to about 128 feet......DaveB

Sanborn Maps

Be careful when using the maps for track placement. I have several for the B&M on disk and while they are very handy for building dimensions/construction info, they often show just a general placement of trackage. I've found that industry sidings (next to structures) are fairly accurate. Nearby yard or mainline tracks are often just shown as reference points with some tracks omitted or turnouts in different positions that they actually were.

Duane Goodman

Peco pointwork options

Hi Greg,

I've pinched this from another post of mine elsewhere on here 

Your Peco pointwork options and part #'s are:

For Code 100 rail 

Set track radius #2 (ST240-ST242) 438mm (17 1/4")  Insulfrog only. 22 1/2 degrees - Parallel track spacing 67mm  (2.6")

Short radius (SL91/SLE91-SL92/SLE92) 610mm (24") 12 degrees - Parallel track spacing 50mm (2')

Medium radius SL95/SLE95-SL96/SLE96 914mm (36") 12 degrees - Parallel track spacing 50mm (2')

Long radius (SL88/SLE88-SL89/SLE89 1584mm (60") 12 degrees -- Parallel track spacing 50mm (2')

Peco Set Track Curve Radius

R1 - 371mm (14 5/8")

R2 - 438mm (17 1/4")

R3 - 505mm (19 7/8")

R4 - 571mm (22 1/2")

For Code 83 (US profile)

#5 - (SL8351/SLE8351/SL8352/SLE8352) 660mm 26"  11.4 degrees 

#6 - (SL8361/SLE8361-SL8362/SLE8362) 1092 (43") 9.5 degrees

#8 -  (SL8381/SLE8381-SL8382/SLE8382) 1702mm (67") 7.15 degrees 

For your street curves I'd recommend the Peco SetTrack turnouts. This will get you swung 90 degrees in just over 17" / 438mm. A saving of 6" less than any other option.

And before anyone gets bent out shape by the SetTrack turnouts being Insulfrog only, may I draw your attention to the following photo of a Peco small radius crossover with the left-hand turnout as an Insulfrog and the right-hand turnout is an Electrofrog.

 Note just how little of the upper turnout is black leading up to and around the frog area. The current Peco design is a long way from the older deadfrog designs where all the check rails and most of the frog were a plastic blob.. Provided your track work is clean and you have multiple pickup points for your locomotive, then you are reasonably unlikely to have trouble at the frog. I'm running small 4-wheel locomotives over them currently without problems.

There is some European tramway track by Tillig that just might get you there tighter 

Their outer radius is given at 250 mm (10") and their inner radius is given at 204 mm (8") 

But this tight a radius might not be capable for unmodified US-based rolling stock. Bogies fouling truss rods/undergear and coupler swing of body mounted couplers on curves may be show stoppers.

Over to you,.  

Thanks for the replies. I am

Thanks for the replies. I am hand laying turnouts so that doesn't matter to me, I can make anything. 12" radius sounds about right. I'll do some experiments.

On the prototype would they use some kind of idler cars so the locomotive didn't have to traverse the sharp curve?

Not just the curve

An idler car was likely used so a loco would not enter a structure. There is a great excuse to build a couple short idler flats!

"On the prototype would they

  It depends on the engines used. The Harlem transfer used  an 0-4-0 steam switcher,a boxcab diesel and a GE 44 ton diesel to switch their 90 foot radius track. The CCT used GE 44 and 70 tonners and Alco S2,S4 switchers on their sharp radius street tracks. In general if a crew had a few cars with them they'd likely use them as a handle if the radius was marginal for their engine....DaveB

,

double jointed

For a time, the B&O in Baltimore used an Alco S1 to handle the train, and had an elderly 44 Tonner (too sickly to pull the train alone anymore) along to actually shove into the tight spurs. Many of these spurs were laid out for 36' cars or smaller, and working with two 40' or 50' cars coupled was not wise.
In the last years of the Pratt Street line, that Alco S1 was equipped with the double jointed coupler. The standard coupler was replaced with what looked like a link and pin coupler; mounted in that was the regular knuckle coupler which now extended further out than usual, but you could stay coupled up as the drawbar swung around hairpin curves from the 1890's. I believe the double joint was originally on the steam (that would be Varney's "Little Joe") and later on the 44 T's that replaced them. I would think there are photos of that arrangement around.