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Cool Old Twin 6-71 DC Generator

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
So I transferred to a different ship, all kinds of cool new old equipment! This was used to power her DC winches and accessories. It’s still functional but there is a BIG AZZ rektumfrier installed so the old generator is back up only. Can’t wait to run a work out session on her:crazy::D
 

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RobW

Subscriber
Last Subscription Date
06/11/2019
Re: Cool old twin 6-71 DC generator

How are they tied together, gear drive, sprocket and chain?
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
Re: Cool old twin 6-71 DC generator

Looks like a gear drive. It has an oil sump but could be a wet chain also. I just got here yesterday haven’t worked on it yet. Name plate shows 1.33:1 ratio. Each engine has a clutch.
 

Vanman

Subscriber
Last Subscription Date
06/10/2020
Re: Cool old twin 6-71 DC generator

GM also built quad 671 power units. :cool:

That generator is SWEET! I couldn't quite make out all of the nameplate. Could you post the data? :D
 

Power

Registered
Re: Cool old twin 6-71 DC generator

Tell us about the antique ship you are now on - when built, current power plant, AC gens...., or give name so we can look it up.
 

K-Tron

Registered
Re: Cool old twin 6-71 DC generator

Three of my older Detroit Diesel friends had worked at Great Lakes Diesel way back when. Lowell was one of the best Detroit Diesel mechanics they had. Lowell has since passed on, but Dan R. and Ed W. are still alive and might remember this twin pack when it was new. Thank you for sharing. I hope you can post a video when it is time to run those old girls. A Twin and Quad pack are so on my want list when I have my own building to store stuff.

Chris
 

Vanman

Subscriber
Last Subscription Date
06/10/2020
Re: Cool old twin 6-71 DC generator

It's a shame the original steam equipment was scrapped, but I suppose it reached a point where it was not economical to repair, or the heavy oil had caught up to diesel in price?

Interestingly those GE engines seem to be practically identical to the ones in the locomotives I used to ride around on. They were also V-16, and 1050 rpm, but 4400 hp. Actually, 4400 hp at the wheels, I believe around 4500 hp at the flywheel. Wonder why the marine ones would be lower? Maybe longer hours at full power? Locomotives usually get a breather sooner or later due to curves or lessening grades. But they hammer away at ~15 mph on Cajon Pass for quite a good long time to get to Summit. :D
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
Re: Cool old twin 6-71 DC generator

I’m not sure about the lower rating. This is my first GE powered ship. It is a locomotive engine though.

Steam Went the way of the dodo due to fuel economy. This shop likely burned about 60 ton per day of heavy fuel when she was a steamer, probably 20 ton per day to maintain steam in port. If I had to guess this GE likely uses a little over 10 ton per day at full away and nothing in port. Pretty big difference in fuel consumption... not may steam ticketed engineers left either. I bet Power could explain a lot better, he’s a steam engineer!
 

The Diesel Doctor

Subscriber
Last Subscription Date
12/28/2019
Re: Cool old twin 6-71 DC generator

WOW, nice looking unit. Noticed in your pic#3 that they have limiting speed governors with the normal and battle speed control covers. In pic#4 looks like there is a electronic governor that controls the linkage to the L/S governors that maintains the required RPM for the generator as a hydraulic one would. AL
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
Re: Cool old twin 6-71 DC generator

WOW, nice looking unit. Noticed in your pic#3 that they have limiting speed governors with the normal and battle speed control covers. In pic#4 looks like there is a electronic governor that controls the linkage to the L/S governors that maintains the required RPM for the generator as a hydraulic one would. AL
Yes, that’s a Woodward UG-8 I believe, mechanical/hydraulic governor. It is just controlling the two Detroit governors via a bell crank arrangements. It looks like you can engage one, both or either Detroit governor to be controlled by the Woodward. I really haven’t looked at this in any detail other than “WOW NEAT-O”. I’ll snap a couple more pics tomorrow and have a better look.

Being DC I’m not sure why they installed a Woodward governor though. Close on the rpm should be good enough as there’s no frequency to be concerned about. Seems like they would be set to run about 1600 rpm as the generator lists 1200 rpm and gear box is 1.33:1... seems low for 6-71 no? I thought their torque peaked higher...


Power, thanks! Are you referring to the Co2 cylinders in the pic of the engine? There is a hose reel you can’t see. Pull the pin and take the nozzle where you need it. Those bottle are damn big and I’m not lifting one! Edit: it does seem to be one of the nicer engine rooms I’ve seen. It’s bright and clean, lots of space around all the machinery. You could toss a ball around or pass a hockey puck from shipside to shipside forward of the ballast manifold where I’m sure the old boiler room would have been... also has something I’m not used too... TOOLS!!! TOOLS ON EVERY DECK:crazy:
 

The Diesel Doctor

Subscriber
Last Subscription Date
12/28/2019
A limiting speed GOV can only control idle and the no load speed.There is no GOV control between them, other than you moving the throttle lever up and down to hold a desired speed. Your UG-8 does that for you through the linkage. AL
 

AngrySailor

Subscriber
Last Subscription Date
01/31/2020
Ahhh. I ran into something similar when looking for a 6v53 for a pick up truck conversion I’m (slowly) working on... there were differences between stationary applications, over the road and marine governors.
 

Power

Registered
Re: Cool old twin 6-71 DC generator

I know don't REALLY need it up on the lakes, but curious. Did retrofit include air conditioning crew quarters?

Angry, Something to perhaps watch- I do not have significant fresh water time, but on ocean going vessels of that age, it is common for welds at hull penetrations to rot out.

"Joe, go to the galley and get me a couple of #10 cans while I pound in some wood wedges and dig out the hydraulic cement."
 

Vanman

Subscriber
Last Subscription Date
06/10/2020
Neat! I'm guessing it has two commutators, but it may well have one commutator and (unlikely) two or (most likely) three collector rings and a transformer to derive the neutral. The transformer method would be favored where the neutral need not be capable of full load current, as it saves the need for one of the large and expensive commutators and the attendant brushes, which must carry the full output current.

The three collector rings are tapped off the armature windings and connected to a three phase WYE transformer. The WYE point becomes the neutral, exactly half way between the main two dc outputs.

From what I have seen, the naturally aspirated 71 series Detroits are mated to generators at 10 kW per cylinder when run at 1200 rpm, and 15 kW per cylinder when run at 1800 rpm. By this measure, your 12V71 equivalent would only be ~160 kW. But those were always AC generators though. Starting most AC motors requires considerably more hp from the engine.

With an adequate number of resistance steps in the starter, a DC motor can be started and accelerated up to speed, developing more or less full load torque, and taking around full load current. In other words, it may have been typical to oversize the engine for AC generators, but this is not necessary for a DC generator.
 
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AngrySailor

Subscriber
Last Subscription Date
01/31/2020
Power, yes we have air conditioning installed thankfully. It does get pretty hot and humid on the lakes in the summer months. I can’t imagine back in the day putting in an engine room watch on a steamer then retiring to a sweltering cabin:uhoh: I never was crew on a steamer but I sailed a couple days as a contractor on the s/s Canadian Leader which was a turbine ship. It was very interesting, quiet, clean and HOT! The boiler room was noisy with all the draft fans and a good number of nozzles open! Near silent while canalling. Edit: oh yeah, forgot about the wood plugs... been there a few times. Nothing too crazy, worst was a sea chest vent valve broke off. 2” line so not too bad but what a pile of water comes in with ~26’ head pressure:eek:

Vanman, thanks for the info. Maybe I’ll have time to pull the rear inspection cover and snap a few pics soon. We’re tied up for about two weeks and my work list is awful short:D
 

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