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Generators & Motors General Discussion Antique Generators, Light Plants and Old Electric Motors: Questions and answers about restoring and showing old power generation systems.

Generators & Motors General Discussion

Gear up for generator head


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  #1  
Old 11-21-2012, 05:47 PM
plym49 plym49 is offline
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Default Gear up for generator head

All of the value-priced 'little' generators have two poles, so they need to spin at 3600 rpm to produce 60 cycle alternating current.

Four-pole heads can run at 1800 rpm, but that costs more, so the 'value' units only have two poles.

Personally, I hate the sound of a one-lung engine screaming along at 3600 rpm. It sure would be nice to run a small gen-set at 1800 rpm.

Benefits would be:

1 - Not as loud
2 - Less wear and tear on the engine
3 - Fewer windage losses inside the engine
4 - Higher volumetric efficiency while running, since a larger throttle opening would be required to produce the same amount of shaft horsepower
5 - Slight reduction in GPH due to 3 and 4 above (with the extended outages seen these days, every increase in fuel efficiency can be worth going after)

Issues would include:

1 - Need to reset the governor to 1800 rpm
2 - Not sure if these motors can produce the same HP at 1800 rpm as they can at 3600 rpm (even with the throttle open more) --- if not, then you would see a reduction in the number of watts you could generate
3 - Remounting the engine and gen head to include a 1:2 drive

I imagine that there are several ways of setting up a 1:2 drive. The easiest might be to use an automotive timing belt. They are plentiful and cheap, and some can run dry. They can easily handle 8 or 10 HP, and if that is a concern, just double them up - they are cheap enough - that would provide backup, too. Another approach might be to use go-kart parts, with a 40 toothe sprocket on the genset and an 80 tooth on the motor. Chain would be noisy, though, and requires lubrication.

I have this old Coleman screamer (pictures below) that is the backup to the backup. I wonder if this might not be a good science project. What do you all think?

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  #2  
Old 11-21-2012, 06:15 PM
Wayne 440 Wayne 440 is offline
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Default Re: Gear up for generator head

Your engine at 1800rpm will produce roughly 1/2 of the power it does at 3600rpm.

Making an end plate/bearing/shaft extension for the generator and a device to adapt the tapered engine shaft to a standard pulley will be a more than trivial job.

To me, it is almost certainly not worth the time and expense. But if you enjoy such projects and are looking for a way to spend some time, it could be done.

---------- Post added at 04:15 PM ---------- Previous post was at 04:11 PM ----------

And the losses in the belt drive will probably offset any gain in engine efficiency. My experience has been that engines are more economical when run at or just slightly above their peak torque point. I guess that would be around 2700 RPM for your engine.
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  #3  
Old 11-21-2012, 06:21 PM
plym49 plym49 is offline
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Default Re: Gear up for generator head

Quote:
Originally Posted by Wayne 440 View Post
Your engine at 1800rpm will produce roughly 1/2 of the power it does at 3600rpm.

Making an end plate/bearing/shaft extension for the generator and a device to adapt the tapered engine shaft to a standard pulley will be a more than trivial job.

To me, it is almost certainly not worth the time and expense. But if you enjoy such projects and are looking for a way to spend some time, it could be done.
Half the engine power? That is probably OK. When I use this unit I only load it about half way. I will lose a little in the gear train, but I can deal with that.

I have a second, scrap unit like this as well as a good supply of parts and materials, so not really any expense and it should not be too hard to fabricate the gear train and so on.

Time, yep that is always an issue. Was hoping that someone here has tried it already; if not, I might just have to try and find time as the curiosity has gotten into me. And I do enjoy projects like this.
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  #4  
Old 11-21-2012, 06:59 PM
RSCurtis RSCurtis is offline
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Default Re: Gear up for generator head

Most engines designed to run 3600 RPM will lose governor sensitivity at 1800 RPM, unless it's an old Onan or Wisconsin. If you could gear the generator to run the engine at 26-2800 RPM, everyone would be happy.
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  #5  
Old 11-21-2012, 07:26 PM
plym49 plym49 is offline
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Default Re: Gear up for generator head

Quote:
Originally Posted by RSCurtis View Post
Most engines designed to run 3600 RPM will lose governor sensitivity at 1800 RPM, unless it's an old Onan or Wisconsin. If you could gear the generator to run the engine at 26-2800 RPM, everyone would be happy.
Interesting thought.

I had been wondering how to get the engine speed down. I wonder if Briggs has an 1800 rpm governor. If not, I would have either fool the governor that it was seeing 3600 rpm, or switch to an external governor. I might have an external Gravely belt drive governor kicking around, now that I think of it.

But if none of that pans out, your idea is a good one.
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  #6  
Old 11-21-2012, 07:44 PM
DriverR DriverR is offline
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Default Re: Gear up for generator head

A serpentine or V belt drive would be the simplest to implement with readily available parts but problematic with regard to the end carrier bearing of the OEM design of the Coleman. The torsional force on the rotor of tightening such a belt would quickly destroy the bearing.

A cogged belt would more or less have to be used as they need not be stretched too tight for positive engagement.
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  #7  
Old 11-21-2012, 07:57 PM
plym49 plym49 is offline
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Default Re: Gear up for generator head

Quote:
Originally Posted by DriverR View Post
A serpentine or V belt drive would be the simplest to implement with readily available parts but problematic with regard to the end carrier bearing of the OEM design of the Coleman. The torsional force on the rotor of tightening such a belt would quickly destroy the bearing.

A cogged belt would more or less have to be used as they need not be stretched too tight for positive engagement.
I was figuring on using a cogged belt to prevent slippage - this should preclude any untoward force on the rotor bearing/shaft. (I agree that that could be a concern.) Automotove timing belts and gears are dirt cheap. I would have to do some catalog searching to find the best donor.
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  #8  
Old 11-21-2012, 08:19 PM
DriverR DriverR is offline
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Default Re: Gear up for generator head

Here is a picture of a Honda Goldwing MC engine. All automotive gearing between cam and crank will be 2:1.



---------- Post added at 07:19 PM ---------- Previous post was at 07:17 PM ----------

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  #9  
Old 11-21-2012, 08:30 PM
plym49 plym49 is offline
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Default Re: Gear up for generator head

Quote:
Originally Posted by DriverR View Post
Here is a picture of a Honda Goldwing MC engine. All automotive gearing between cam and crank will be 2:1.



---------- Post added at 07:19 PM ---------- Previous post was at 07:17 PM ----------

Yes, so with the cam belt gear on the motor and the crank belt gear on the rotor, I can run the engine at 1800 with the rotor seeing 3600.....

(the picture did not come through)

---------- Post added at 07:30 PM ---------- Previous post was at 07:20 PM ----------

I stand corrected - the picture did indeed come through. That is a great example of what you could accomplish with automotive (or motorcycle) timing belts.

McMaster-Carr also has a good selection of timing belts and pulleys. Could be easier to mount theirs to the motor and rotor shafts..............
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  #10  
Old 11-21-2012, 08:57 PM
ken karrow ken karrow is offline
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Default Re: Gear up for generator head

Two thoughts, One: have considered roller chain with a little lube they are extrmely effient. Two: get a variable speed governor set off the same series of engines with cable contro and adjust till you get 3600RPM on gennie. Also once you have got you sprocket or pulley set up in place, check with briggs. On some engine series various governor springs are available at minimal cost. I do agree that 2600RPM or thereabouts is a good compromise. I do have a question for all the gennie pros out there. I have a 3.5 KW gennie that calls for 3600 RPM and I want to tie it to a cast iron Briggs. It is made for belt drive. Have an extra 12 & 15 Hp engines, 30 & 32 cu. in. These are the old big block singles. I want to what this poster is doing and run the engine slower than 3600 RPM. My question is does it make any difference what direction I spin the gennie? Thnks for any help. Ken
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  #11  
Old 11-21-2012, 09:00 PM
Jim McIntyre's Avatar
Jim McIntyre Jim McIntyre is offline
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Default Re: Gear up for generator head

Quote:
Originally Posted by plym49 View Post
I wonder if this might not be a good science project. What do you all think?
The end result will be a frankengenerator of questionable utility and reliability.

IMHO a better science project would be to find an old Onan CCK genset and get it working...
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  #12  
Old 11-21-2012, 09:01 PM
beezerbill beezerbill is offline
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Default Re: Gear up for generator head

Hello,

Interesting project. Keep in mind that the alternator rotor is attached directly to the crankshaft with no intermediate bearing on the engine side of the alternator, so, as stated by wayne 440, separating the two and running the alternator with a belt will require a not insignificant amount of engineering and machine work. Also, the bearing on the "tail" end of the alternator is probably in a plastic end cap but is also under no significant load; if you rearrange the alternator to be separate from the engine and driven by a belt, this bearing will have a load on it and the plastic end cap may not be too happy with that. Finally, the engine may be one of Briggs & Stratton's "kool-bore" engines; a slick marketing term to sell the notion of running the piston directly in an aluminum bore without benefit of an iron liner. These engines had lifetime issues especially if not well maintained; I would at minimum pull the head and look for wear, and perhaps pull the piston and look for scoring.

One thing to consider is to find another 8 hp Briggs engine like the one on your Coleman (they are common), but with a straight, not tapered, PTO shaft. Cannabilize the engine on the Coleman for the PTO side cover and crankshaft; you could probably make your alternator end cover and extention shaft out of these. You will have a plain bearing at that end of the alternator but to get a sanity check on whether the idea works, it might be a quick way to get there.

If you do undertake this project, please post your progress!
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  #13  
Old 11-21-2012, 09:10 PM
DriverR DriverR is offline
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Default Re: Gear up for generator head

I was on the same train of thought 1800 (1850 is considered idle) was too slow as some of the earlier posters wrote. If lugging the engine at 1800 there may not be enough cooling air flow. They do sound good at 3000 and will still be within the torque curve and not breaking a sweat.
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Old 11-21-2012, 09:22 PM
plym49 plym49 is offline
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Default Re: Gear up for generator head

Quote:
Originally Posted by Jim McIntyre View Post
The end result will be a frankengenerator of questionable utility and reliability.

IMHO a better science project would be to find an old Onan CCK genset and get it working...
I might have mentioned it already, this unit is a backup to the backup to the backup. It's utility is for when I need a small (3KW or less) of power for an extended period. Hence, fuel consumption and noise are issues. That, for me, would be the utility.

As far as reliability, I would imagine that unless I totally slim shadied things, the parts I'd add would have a greater mean time to failure than the engine or genhead have now. I would also do things reversibly, so it could always be brought back to stock configuration.

---------- Post added at 08:15 PM ---------- Previous post was at 08:13 PM ----------

Quote:
Originally Posted by DriverR View Post
I was on the same train of thought 1800 (1850 is considered idle) was too slow as some of the earlier posters wrote. If lugging the engine at 1800 there may not be enough cooling air flow. They do sound good at 3000 and will still be within the torque curve and not breaking a sweat.
Air flow - that is a good point. I will have to look into that.

---------- Post added at 08:22 PM ---------- Previous post was at 08:15 PM ----------

Quote:
Originally Posted by beezerbill View Post
Hello,

Interesting project. Keep in mind that the alternator rotor is attached directly to the crankshaft with no intermediate bearing on the engine side of the alternator, so, as stated by wayne 440, separating the two and running the alternator with a belt will require a not insignificant amount of engineering and machine work. Also, the bearing on the "tail" end of the alternator is probably in a plastic end cap but is also under no significant load; if you rearrange the alternator to be separate from the engine and driven by a belt, this bearing will have a load on it and the plastic end cap may not be too happy with that. Finally, the engine may be one of Briggs & Stratton's "kool-bore" engines; a slick marketing term to sell the notion of running the piston directly in an aluminum bore without benefit of an iron liner. These engines had lifetime issues especially if not well maintained; I would at minimum pull the head and look for wear, and perhaps pull the piston and look for scoring.

One thing to consider is to find another 8 hp Briggs engine like the one on your Coleman (they are common), but with a straight, not tapered, PTO shaft. Cannabilize the engine on the Coleman for the PTO side cover and crankshaft; you could probably make your alternator end cover and extention shaft out of these. You will have a plain bearing at that end of the alternator but to get a sanity check on whether the idea works, it might be a quick way to get there.

If you do undertake this project, please post your progress!
I do in fact have a complete non-operational second unit like this one. I could cannibalize the second motor case and crankshaft to provide a front bearing for the rotor. This would also make crankshaft/rotor alignment easy. The outer end of the crankshaft would grab the rotor shaft, just like now. Putting the pulley on the inside of the 'crankcase' should isolate the far end of the rotor shaft from axial forces.

The motor does in fact have a cast iron liner. I love this motor - I have looked inside, and it is mint.
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  #15  
Old 11-21-2012, 10:28 PM
beezerbill beezerbill is offline
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Default Re: Gear up for generator head

plym49,

Sounds like you have a good handle on this stuff. There is some chance it might not work at 1800 RPM but you could easily regear it to run at a higher RPM, once you have the generator repackaged and the engine PTO shaft modified. Keep in mind lots of people have made up some pretty interesting "Frankenstein" conversions and fixes; there have even been a couple of recent threads on Frankenstein magneto adaptions as well as ingenious field fixes. Even if the project is an utter failure, what you learn from it is worth a whole lot more than sitting around listening to the old Coleman blattering away at 3600 RPM. Be safe with the electrical part, and go for it!
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Old 11-21-2012, 10:45 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Gear up for generator head

The engine plate should be ball bearing, it will be an open bearing, This should be replaced with a sealed bearing, it won't be bathed in oil anymore.
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Old 11-21-2012, 10:56 PM
richard.bessey richard.bessey is offline
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Default Re: Gear up for generator head

I like the idea, so much so that I did this myself.
Pictures Here

I searched craigslist for a belt driven generator, so I could gear the engine differently. Fairly odd, belt driven generators but they are out there. I was able to locate two within a year of looking. One at a yardsale, has not ran for years and the owner wanted $500 for it. I passed on that one
Another one, had a blown engine (Engine threw a rod), the engine was dissassambled, included the frame and genhead. I struck up a deal, $40 and I got to take it all home.
I had a Harbor Freight engine (Honda clone) that was on my old Areins rototiller. I pulled it off, got a 6 inch pully for the engine, the generator had a 4 inch pulley, rigged it all up and fired it up.
Overall, it works pretty well. The engine runs 2400 RPM to get 60 hertz. I have logged, 40 hours or so on this setup.

The engine is a lot more pleasant at 2400 RPM then 3600 RPM.

Its a 6.5 HP engine, running at only 2400 RPM. I have found its easy to pull more power from the genset then the engine can put out.

The bad - I had to build a new belt guard, the old one would not cover the larger 6 inch pulley I put on the engine.
The engine does not like to take a big load, like a saw or compressor. I get it to start the compressor, I have to throttle the engine up a bit to almost 3,000 RPM's, once the compressor is started I can bring the RPM's down.
The belt drive system does generate a little bit of noise. You can loosen the belt a bit which helps, but it still makes a little noise.
Starting the genset with the 6 to 4 ratio is a little difficult and hard on the starter rope.
The genset all together weighs about 80 pounds, a bit heavy to load in a pickup by yourself.

The good - Generator is fairly quiet, very reliable, and overall works well. Its nice to be able to adjust the RPM if I need more power, and if I am running a small load I can bring the RPM's down to an idle. Burns a lot less fuel that way (Poor mans version of the Honda EU200I inverter generator).

So I have a red generator, Blue Harbor freight engine. And last month the plastic parts of the recoil starter broke into a couple pieces. I ordered a replacement, its red. now its a fairly colorful genset.
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Old 11-21-2012, 11:20 PM
GADavis GADavis is offline
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Default Re: Gear up for generator head

Couple of things I have learned through the University of Hard Knocks. I worked 30+ years for a mining company and learned a lot about improvising things AKA local resources and supplies on hand. In other terms using junk. We had a pump that was specfic to an application which had an older Wisconsin engine like maybe an AKN or something close to that. It wore the cylinder and piston out. We took the rod out along with the cylinder and piston bolted a blank cover on the top of the crankcase,took the flywheel and had it machined so we could mount a 2 groove v-belt pulley on it and hooked a 5 hp 3 phase electric motor to it and it ran for many years after that. the pump impeller was mounted to the crankshaft like the generators are.

Second thing is that I have an 8 Kw Dayton belt drive generator coupled to an Onan that is like the CCK but is larger and maybe an NH? I run the Onan at 1800 RPM give or take 20 RPMs and use an 8" drive pulley coupled to a 4" driven pulley on the generator with 2 B-35 belts with no problem from slippage or friction loss. It is very smooth and reliable. The Onan will run all day under a full load and burn about 1/2 G.P.H. It does not vary or bobble and when the full load hits it the governor picks it up almost with out a flicker and will maintain 58-60 Hz and 235-240 volts. I am pretty sure this is a Winco generator relabeleld for W.W. Grainger Co.

I was going to replace this approximately 20 hp Onan with an 18 Hp Briggs 3500 series Vanguard V-twin and convert to LP gas but after doing my research I concluded the B/S did not have enough low speed torque to hold a steady rate of power as does the Onan so that ended that project . The Onan will soon get an LP conversion
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  #19  
Old 11-22-2012, 06:44 AM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Gear up for generator head

[QUOTE=GADavis;841246] We had a pump that was specfic to an application which had an older Wisconsin engine like maybe an AKN or something close to that. It wore the cylinder and piston out. We took the rod out along with the cylinder and piston bolted a blank cover on the top of the crankcase,took the flywheel and had it machined so we could mount a 2 groove v-belt pulley on it and hooked a 5 hp 3 phase electric motor to it and it ran for many years after that.

The Wisconsin probably had an oil pump for lube, the B&S will likely be splash lube, without the rod and dipper it will have to be modified to oil the mains.
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Old 11-22-2012, 10:02 AM
Joe Romas Joe Romas is offline
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Default Re: Gear up for generator head

I had a belt drive Honda generator like Richard's that originally had a 11 HP Honda flatheat that blew up and experimented running it with one of those 10 HP air cooled diesel engines. As other have mentioned I found that under 2700 rpms the torque drops off very fast.

I currently have a Kubota D905 powered Boss light tower for backup power that has a 6000 watt 4 pole generator. The 3 cylinder 900cc diesel engine is rated just over 20 HP max but at 1800 it's rated at just over 10 HP or only HALF
Advantages are sound, longivity and fuel economy and at 3600 hours it's still running like new.
Disadvantages are initial cost and weight but light towers are trailer mounted that makes it easy to refuel
Watching e-bay and Craig's list they can be had reasonably. There have been some on the extreme west coast selling around $2000 recently on e-bay.
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