SD35 dimension between mid axles on trucks ?

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SD35 dimension between mid axles on trucks ?

Postby Scaro » Sun Mar 03, 2019 3:58 am

I read a figure of 35' on most diagrams, but some say that measurement is between the bolsters, others say it is between truck centres.

As these two are not necessarily the same, I wanted to check before hacking up a chassis to build one. (none available in my scale.)

Regards ,

Ben
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Re: SD35 dimension between mid axles on trucks ?

Postby Allen Hazen » Mon Mar 04, 2019 11:19 pm

Here (accessed through the "Fallen Flags" rail image site) is the Pennsylvania Railroad's diagram of what they called an "EF-25a":
http://prr.railfan.net/diagrams/PRRdiag ... z=sm&fr=ge

You are right that the centre of the middle axle does not necessarily coincide with the truck's centre of rotation in C trucks, but EMD's "Flexicoil" truck, used o their domestic CC models from the SD-7 until the introduction of the Dash-2 line in 1972 seems to one case where they do coincide!
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Re: SD35 dimension between mid axles on trucks ?

Postby Scaro » Tue Mar 05, 2019 2:49 am

Thanks Allen, yeah it's looking like they coincide. And at least with the SD35 the drawings align with what broadside images show.

Worth being careful of some of those PRR images tho. Check out the X58 boxcar diagrams ;-)

Ben
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Re: SD35 dimension between mid axles on trucks ?

Postby Allen Hazen » Wed Mar 06, 2019 9:21 pm

Agreed, some of the PRR diagrams are a bit questionable, and many are not very detailed. I think we are o.k. on the SD-35 question, though: several other diagrams seem to agree. (The "Fallen Flags" site also has diagrams from C&O and from L&N.) EMD kept the same underframe dimensions on its SD units from introduction on the SD-7 until they went for a longer frame on the 40-series in 1966. (With, of course, a special lengthening for the SD-35.) Kalmbach's "Our GM Scrapbook" has a number of drawings -- some I think from "Model Railroader," others from EMD sources -- in an appendix, and the SD-9 is shown there with 35 feet between the truck centres / 2nd axle centres.
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Re: SD35 dimension between mid axles on trucks ?

Postby Allen Hazen » Thu Mar 07, 2019 1:36 am

Grrr.... One typo and one real error in my last post.
Typo: When I said "(With, of course, a special lengthening for the SD-35.)," I meant "SDP-35": the version of the SD-35 with a steam generator at the rear of the long hood.
Error: The SDP-35 wasn't actually longer than the plain SD-35. The long hood was extended over the rear walkway, but the overall frame length and the truck spacing was the same!
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