Model Railroading > SP's "One High Brake Cylinder Per Truck" on SD40/45's

Curious about why SP had one high brake cylinder per truck on some SD40 and SD45 locomotives. They often were the rear engineers side and front conductors side. I've been swapping some sound decoders between untils, from special paint job units that I bought with sound to more run of the mill units I can run in any consist. I replaced the sound board on this unit with a direct wired 9-pin plug. I'n looking at photos for obvious detail upgrades on this already fairly well detailed unit. I already added lift rings, but saw that Athearn failed to duplicate the one high brake cylinder per truck, and the noticeable brake piping. So I set about correcting that. Will also add the spare knuckle to the top of the fuel tank. But I've always been curious as to why have the one high brake cylinder. Similarly painted SD 7399 also had the one high brake cylinder per truck setup.

Ted Curphey
Ontario, OR

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 I'm quite certain the single high brake cylinder was to accommodate the handbrake.

The single brake cylinder, as has been pointed out, was to accommodate the brake lever that gave a place for the hand brake to attach; thus rear engineer or front fireman's side. 

What I'm curious is why this model has an under-slung brake cylinder for that wheel; that would mean 2 brake cylinders for that one wheel. I suspect that if you could find a photo that under-slung brake cylinder either isn't there or is mounted differently.
 

Great job capturing that detail.
It appears looking through photos that there is a bracket/plate with no cylinder on the wheel with the "high" cylinder. As if they left the original attachments in place without the cylinder.

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Railbaron Wrote:
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> What I'm curious is why this model has an
> under-slung brake cylinder for that wheel; that
> would mean 2 brake cylinders for that one wheel. I
> suspect that if you could find a photo that
> under-slung brake cylinder either isn't there or
> is mounted differently.

I hadn't got around to removing it yet. Going to try to carve parts of the cylinder off and leave the mounting bracket and connecting rod. Also need to trim that port on the underside of the cylinder I added.

Ted Curphey
Ontario, OR

Thay have two, one F and R ?

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funnelfan Wrote:
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> Curious about why SP had one high brake cylinder
> per truck on some SD40 and SD45 locomotives.

The quick, and not intended to be curt answer is becaue that's the way EMD built them.  The brake cylinder and brake shoe arrangement on the Flexicoil truck evolved over the years, Don Strack's Utah Rails site has some information:

https://utahrails.net/loconotes/loconotes-trucks.php

None of SP's SD40s were delivered with that style truck, the first order came with the all-low brake cylinder arrangement, the second order with the all-high brake cylinder arrangement.  SP's second order of SD45s and the SDP45s came with the "Hi-lo" arrangement you've replicated on 7342.  Over the years, the trucks were swapped during shopping, clearly 7342 being one such example.  A lot of SP's fifth SD45 order (9069-9103) seemed end up with the Hi-lo trucks from the second order (8845-8935).  I modeled one such example years ago:

https://www.trainorders.com/discussion/read.php?3,1459020,1459453#msg-1459453

Athearn made the correct version of the Hi-lo style on the Genesis SDP45, though the sideframes aren't compatible with the RTR models.  I'm sure Scale Trains will have the correct version when they release the SD45s from that period of EMD production in their Rivet Counter line.

And since I'm not sure I ever posted a photo of 9087 finished, here is a photo of the modified sideframe after painting and weathering.

Elizabeth
 

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Betsy Wrote:
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> And since I'm not sure I ever posted a photo of
> 9087 finished, here is a photo of the modified
> sideframe after painting and weathering.
>
> Elizabeth
>  

First-rate weathering job!
 

The reason for the change was to allow proper application of the hand brake. With the low cylinders, in order to properly apply the hand brake, the air to that truck had to first be cut-out, then the handbrake fully applied, and the air cut back in. Just applying the hand brake without cutting out the air would many times result in the hand brake not being fully applied, which could result in the unit rolling away if the air bled off. 

Chris Toth
NSDash9.com

NSDash9 Wrote:
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> The reason for the change was to allow proper
> application of the hand brake. With the low
> cylinders, in order to properly apply the hand
> brake, the air to that truck had to first be
> cut-out, then the handbrake fully applied, and the
> air cut back in. Just applying the hand brake
> without cutting out the air would many times
> result in the hand brake not being fully applied,
> which could result in the unit rolling away if the
> air bled off. 
>
> Chris Toth
> NSDash9.com

You are correct. On locomotives with underslung brake cylinders there was a valve that, when the handbrake was applied, would vent the brake cylinder and allow proper securement by the handbrake. That valve was not reliable thus as stated above would cause the handbrake to be ineffective. At first, SP had instructions for engineers to physically inspect that the valve did in fact function to insure securement until the trucks were modified by mounting the brake cylinder to the side frame and doing away with the vent valve.

Posted from iPhone

SP wern't the only ones to have this brake arangement. Santa fe and BN and possibly others too.

That underslung brake cylinder "quick release valve" (which didn't always work as intended) was also used on SP's GE U28C, U30C and U33C models as well as the aforementioned EMD SD40's and early SD45's. Proper setting of handbrakes on units equipped with this brake cylinder arrangement was one of the first things that I learned upon entering engine service for the SP (1978 Fixture Hostler, early 1979 Fireman and late 1979 Engineer). Many an unsuspecting engineman received discipline for not properly securing a unit, i.e.,having a unit roll away. If I was on the ground walking up and knew that I was going to tie a hand brake on a unit equipped with the underslung cylinder, I'd reach in and manually bleed the cylinder, before climbing up and setting the hand brake. No risk of the unit moving as you were only bleeding that one cylinder. By manually bleeding the cylinder I was absolutely sure that I had a "good brake"! And I never had one get away!

Tim Dickinson
Locomotive Engineer, SP/UP, retired

Thanks for the responses. I find this really fascinating as I've ran several SD40's and 45's, but never have been close to a unit with a low brake cylinder, not even sure if any are still around in active service. Really makes me wonder how the linkage to the handbrake chain was setup.

Ted Curphey
Ontario, OR



Edited 1 time(s). Last edit at 03/31/20 07:02 by funnelfan.

GNs infamous Hustle Muscle appears to have only one rear truck high cylinder while in service through BN but now has the 2nd on the opposite corner in museum life based on photos. Not sure their site explains the change clearly.

-Benjamin