Locomotive mounted 1003's -- Massive Discovery

[Allertor113]

Hey guys. I really think yall will like this one. Time to update the wiki!

I am not much of a railfan, but an old post got me thinking, and suddenly I found myself on a 5 hour search for these. Then came across some awesome information.
AFAIK, the siren community has only known of the 2 UP Locomotives that had the 1003's installed for Testing - UP 6918, and UP 6924.
Turns out, this program consisted of 6* total Locomotives.

All these are Union Pacific engines:

#3049 SD40 Is noted to be an electronic siren capable of Wail, Hi-Low-Yelp. ~No photos exist to my knowledge. Installed 8/75 ~ Removed 1/79
#1400 SDP35 Installed 4/78, Removed 3/79. 1003
#1402 SDP35 Installed 4/78. Removed 3/79 1003
#1408 SDP35 Installed 6/78 Removal unknown.. Multiple Air horn arrangement.
#6924 DDA40X 4/79 Siren removed from 1402 installed on 6924. 1003
#6918 DDA40X 3/79 Siren removed from 1400 installed on 6918. 1003

Siren remained on unit #6918 and #6924 until unit retired(per a document- photos don't match the statement).

The idea behind the Siren implementation was to warn track maintenance and repair crews of incoming trains.
I believe these are the first time the siren community has seen these 1003's in such quality.

Thank you to Raymond D Woods Jr for originally posting the picture of the UP 615 with a visible horn behind it in a picture from Yermo,Ca from 1983.


*Excerpt from UP timetable*

October 26, 1980
The following comes from Union Pacific System Timetable No. 4, October 26, 1980, Special Rule 1092, page 149:
Siren installed on unit 1400 operated by a single throw toggle switch, siren on unit 1402 operated by a single push button and sirens on units 6918 and 6924 operated by a single slide pole switch. On all units so installed switches are on the instrument panel in front of the engineer labeled "Siren."
It is intended this siren be sounded for an emergency only when approaching and passing gangs or workmen who have not noticed or heard regular horn warning. Sirens are not intended to be used in cities, towns, municipalities or at grade crossings, except in emergencies.
When sirens are used in an emergency situation, radio report of the incident should be made by engineer to dispatcher giving all necessary details.
(This rule first appeared in System Timetable No. 3, dated March 9, 1980, and remained in System Timetable No. 7, dated July 17, 1983. The siren rule was *not* in System Timetable No. 8, dated November 20, 1983.)

Here is the site I was able to get the technical information from https://utahrails.net/up/up-loco-features.php.
Pictures came from old forums, defunct websites, fb groups, etc.
Hope you guys enjoy this, spent 4-5 hours this morning digging through literally probably 5000 pictures. My head hurts.
Cross posting to FB.
-Rhett

[uncommonsense]

Well what a find. This is freaking amazing. Thank you. Those pictures, especially, are special.

My question about these has always been what is powering the chopper and solenoids? Some kind of a generator I’d presume. And I presume these are minus blower. A blower wouldn’t make much sense given the application.

[Allertor113]

My question about these has always been what is powering the chopper and solenoids? Some kind of a generator I’d presume. And I presume these are minus blower. A blower wouldn’t make much sense given the application.

I have limited rail knowledge, but I would be very surprised to find out that these did NOT have a blower. The air required to feed the chopper would drain the air system very rapidly, even in short bursts I imagine. There is the possibility they were using one of the already onboard roots blowers(Big blowers to provide air to cool the traction motors), but my feeling is they probably had a regular blower rigged somewhere.


***EDIT***
Misread your reply, but going to leave my reply up for debate.

[Model L]

Well what a find. This is freaking amazing. Thank you. Those pictures, especially, are special.

My question about these has always been what is powering the chopper and solenoids? Some kind of a generator I’d presume. And I presume these are minus blower. A blower wouldn’t make much sense given the application.

since these are diesel electric locomotives, they presumably used the main generator and likely a step down transformer.

[HDN]

I've seen some of these pictures around. UPRR was always pushing the envelope with their motive power, this being no exception!

I imagine the sirens ran off the locomotive's electricity. These units typically have 600 volt systems. This is doubled up on the DDA40X locomotives since they had twin 16-cylinder diesels (they were effectively two GP40 locomotives on one chassis). Probably used the locomotive's compressed air system or some air from the traction motor cooling blowers to amplify sound output. Just speculating, though.

I don't think using the compressed air system is out of the question - they had big enough air compressors to work the brakes of entire trains and then some. Perhaps there was a separate air receiver tank fitted for the siren.