SD70ACE Noise Question

I saw a loaded BNSF coal train rolling south through Denver, CO yesterday, and it was definitely in a high throttle position - maybe run 8. There was a very loud howl coming from the SD70Ace, and I could hear it for a long time as it proceeded down the track.

Any idea what that could have been? Could the sound be coming from the generator?

Just wondering.

Thanks.

turbo ?

DutchRailnut wrote:turbo ?

I could be wrong, but I thought the turbochargers in EMDs made more of a "ying" sound. I know they do at idle.

at Idle you won't hear turbo, only the gear .

To me, it sounds like the dynamic brake fans. These make a loud howl that can be heard from a long distance away, and the engine must be in a high throttle position for the dynamics to work.

wurlitzer153 wrote:To me, it sounds like the dynamic brake fans. These make a loud howl that can be heard from a long distance away, and the engine must be in a high throttle position for the dynamics to work.

Just curious, would they be using dynamics when climbing with a heavy coal train?

I will ask some of the engineers who are on the forum...

It could just be a shot turbo. Usually a loud howl is not a desirable noise.

Perhaps the train had just come down a long descending grade and the dynamic brake resistors were still hot so the fans continued to operate? Much as projector fans do after being shut off until the bulb cools sufficiently?

fans displacing that much air do spin down fast, but original poster said train was climbing, so no dynamic brake.

Just a guess, maybe a bad or going bad traction motor blower.

read original post, he did not say its a bad noise, just that locomotive was loud ...

The entire train might not have made it down the hill yet?

Even tho the head end might be going up hill, the back end of the train might still be going down. The part going down would still be pushing the part thats going up.

Orrrrrrrrr, there is a speed restriction up ahead and even tho the train is going up hill, it still needs more braking to slow down for a curve/town/bridge, whatever.

I suppose it could have been a bad turbo too, the sounds are slightly different, (much more of a higher pitched whine, sounds more like a 747 than anything else, but I guess taht depends on how bad the turbo is shot) but not out of the ballpark, especially if the engine is revved up while in dynamics, the sound of the bad turbo might drown out the sound of the dynamic brake fan.

Thanks everyone. The train was on relatively level ground - not too many hills in central Denver. If anything it was climbing slightly. It was not a high-pitched whine.

Ultimately there's really no way for any of us to diagnose what the sound was without actually hearing it. What one person might describe as a "howl" might sound completely different to someone else. Words like "howl" and "ying" could be interpreted differently by different people. This reminds me of a railroad.net discussion in which someone was asking about a funny sound coming from a GE locomotive. A few other people jumped into the conversation, having heard the exact same sound, and eventually everyone was throwing out words like whoop, yipe, oyp, fleep, and others I can't even remember. It was rather hilarious watching all these folks make up words to describe the same sound.