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Follow-Up: Emergency Power & Generators

14 Sep, 1999

A collection of email questions and comments from visitors:

From: (outdated email) — I just wanted to comment about the Tip Oda Week segment: The Home-Made generator.

Because of the expense of bringing electric service to my very rural home, my wife and I supplied power to our entire 1300sq ft. house (for 2 years) with a home built generator like the one featured in your Tip O'da Week segment.

We did own 10Kw military surplus generator but quickly discovered that the homemade D.C. generator used far less fuel to do the same job. (the A.C. generator was over-kill).

We converted our house to run entirely on 12v D.C except for the Television which used a 300w inverter. We were able to use all of our conventional light fixtures with 12v bulbs purchased at the auto parts store.

Since we now have electric service at our home, my Home-Built generator has found a new home bolted to the front bumper of my Ford pickup truck ( beside the 8000lb Warn winch) and has a second job running an air compressor. It gets some strange looks but its well worth it in times of trouble.

From: (outdated email): O.K. I don't know if this is going to be of much help. But it has all ways captured my interest. A long time ago in Mother Earth News magazine I seen a article on making a 12 Volt welding rig using a high output alternator on a car. It was used to do light welding in remote places. I don't even know if this is possible but if it is, it might make for a interesting article for those of use who want to stay prepared and don't have the big financial resources to do it all out with name brand items. If its possible I'd like to know what you think of the idea.

P.S. I love your page its been very informative and a big help in more ways than one. Keep up the good work!

From: (outdated email) — It's sometimes tough to start a generator during a cold blizzard (never saw a hot one). I cheat; I run a hose from a propane torch into the carb of the generator or whatever small engine I'm trying to start. The propane flow is small but enough to let the engine run at idle and warm up until the carb vaporized the gasoline. Then just turn the propane torch off and run the engine normally.

This works because propane vaporizes much easier than gas and has a much broader range of explosive mixture.

From: (outdated email) — Bryan: Just a follow-up on a long-since-past discussion we once had:

To quiet down my Coleman 8hp/4500w generator, I clamped a piece of 3 in. ID flexible stainless steel hose onto the engine muffler (3 in. OD) and clamped the other end to a generic truck muffler ($16) which also has a 3 in. connection. I used about 3 ft. of hose in order to provide flexibility (the engine shakes at stop/start and vibrates vigorously during operation). It's not extremely portable, but it's pretty easy, there's no significant exhaust back pressure, and it drops the sound down to the point that I can hear the valves clicking. It's a good solution for someone who plans to use the generator only in his own back yard. If I need to haul it elsewhere, I always have the option of going "stock" and leaving the big muffler behind.


From: Mike — Thanks for a great web page! I am particularly interested in the muffler arrangement you came up with for your Coleman unit. I would like to do something similar, but I am concerned about burning a valve or doing some other damage due to an improper configuration. Do you have any additional tips, plans or insight on this matter?


A response from Bryan @ TheEpicenter.com

... Guess I don't know as much about it as you do! I never thought about burning a valve by my modification. How does that work?


A follow-up comment from Mike

Excessive resistance to the exhaust gas flow (as MIGHT be created by an improperly sized/installed muffler) may cause harmful heat buildup around the exhaust valve. MIGHT is the operative word. Your installation may actually improve the gas flow if the muffler/pipe system resistance is less than the stock unit. On the other hand.... If you haven't had any problems to date, then it sounds like you're in good shape.

Mark Whaley gave me a good lead on a B&S "Super-Lo-Tone" (P/N 493963) muffler. I'll pursue that and fall back on the car muffler approach if I strike out.

Thanks for your response. I really appreciate it.


From: (outdated email) — I like your plans and idea about the emergency generator. I am planning to build one somewhat like the one described here only using a 230 amp Leece Nevelle internally regulated alternator and a little larger motor built on a modified hand cart (dolly). This will allow me to jump start diesel engines which require a large amount of current and also use a bigger inverter (1000 watt). with the addition of a small aluminum panel I will install a volt and amp meter to monitor the output. Ok, it is something a bit bigger, but allows me to get a unit running in short order without running a long run of extension cords or taking a generator out to hook up a small battery charger. I small fog light mounted on a adjustable height rod also allows me to have a work light for working at night.

From: (outdated email) — Good Morning. I am hoping that you may be able to assist me with a query concerning the use of a standby generator and the problem I am having in getting it to run my LP Gas combination boiler (furnace).

My reason for contacting you is as a result of a recommendation from a colleague on a UK conferencing service who suggested I search your website for info.

I live in a rural part of England in a modern timber house. Unusually for the UK in this area, I did not install a solid fuel fire in the house when I built as I do not like open chimneys in houses and a good closed system was going to be pushing my budget a bit too far! As the area I live in is prone to power cuts occasionally, I decided that I would put a changeover switch into the power supply to allow me to run the house on a Gennie and to also supply power to keep the balanced flue gas boiler running and so keep hot water and heating going. The technique works fine apart from the fact the boilers electronic equipment does not like the "flavor" of the electricity provided by the gennie. It has been suggested that the reason is that the control equipment uses the AC wave form as part of it's monitoring system. Dunno how though!! It is not a problem with a dirty power supply with peaks or surges, as all the other electronic gear in the house works fine such as PC's and faxes.

Having read your web site with great interest, I wondered if you could make any suggestion as to a means of resolving this hassle. At the moment, I have to rely on small bottled gas butane heaters for heat when the power goes down which are messy, damp and not particularly convenient.  As you will be aware, when the power goes, it is always in cold, bad weather and all of a sudden everyone wants bottles which then go into short supply. I maintain 2 spares, but heat from my nice, big gas tank in the garden with hot water appeals far more :-)

I have consulted with generator suppliers locally but they tend to be baffled!


From: Carl — First Subject: Home brew generator

1) GM alternators need 12 volts on the field (F) to start producing power (they do not self excite). So make sure the battery has a good charge. 2) I think the newer GM alternators with the single belt system rotate the other way. The are identified by having the multi V pulley.


From: (outdated email) — You should mention the use of propane powered generators. I am currently on a mission of finding a propane powered generator for use during nowstorms/ice storms. I live in a remote area in the Blue Ridge Mountains, and have a 350 gallon propane tank which fuels my furnaces. I have heard that propane generators are available, and it seems that this is much better than storing gasoline.

And a great response to the above question:

From: (outdated email) — This is in reference to the request for info about a propane powered generator. What I suggest is check with the dealer that sells you your propane. They can set you up with an adapter that fits on top of a standard gas carburetor. This allows the use of propane as fuel but also gives you the option to use gasoline if you wish. I used to sell propane hookups for irrigation motors and vehicles. It is advisable to run gasoline through the carb every once in a while to allow the gasoline carburetor to remain usable and help in keeping the engine in good shape. The propane gas tends to dry the system out. Our policy for a vehicle was after two tanks of propane (300 gallons) we would run half a tank of gas. After that we would switch back to propane. The dealer can help you set up a generator to run in this manner.

From: (outdated email) — Subject: Re: home-made generator cooling

Dear Epicenter Crew, I've enjoyed reading the information found in your website and have found that your earthquake/storm advice meshes nicely with what we on the coast of the Gulf of Mexico have learned from many, many hurricane seasons.  Thanks for making such valuable info available.

I have just read of your improvised generator that uses an automotive alternator and a horizontal-shaft Briggs & Stratton type engine. Your research indicated that if the alternator is required to put out its maximum rated amps (70 or so) it will soon overheat and fail.

That was a comment for David Hooper in Canada. IMHO, this is not a problem but I haven't tested it under full load. The fan still works when turned in a reverse mode, but with much lower flow rates. And it pushes air into the alternator, not pulls it through.

Remember that the temperature in an engine compartment is much higher than the alternator will ever see running in free air.

My question is: can a fan of the typical household type be used to blow cool air on the alternator, thus allowing it to run at higher outputs and with less risk of overheating and failure? It seems to me that the small amount of energy that a fan draws would be greatly offset by the extra cooling that a steady stream of cool air might provide.

Yes, that is an option. Another option is to use some J&B metal weld (metal epoxy) to attach external heat sinks to the alternator case (if you are really worried about it).

My reasoning is two fold (please pardon its amateurish nature). I have in the past been able to use a tiny 2-amp battery charger to recharge a dead car battery. The output required to do this caused the little charger's thermal protection to quickly trip off. Then, I aimed a common household fan on the charger and found that it was capable of outputting its maximum (whatever that might be) without tripping its thermal protection circuit. Also, an automotive alternator like the one you're using ordinarily lives at under hood temps of about 200 degrees F. (I'd think) in the summertime, so all you'd have to achieve is a way to keep the alternator from getting over its normal operating temp of about 200 degrees (right?). It seems like a fan-forced stream of cool air could do it.

Oops, jumped the gun. Yes you are correct.

Besides, this method of fan-forced air cooling worked, after a fashion, on air-cooled VW Beetles for decades.

I'd perform this experiment myself, but I don't have the resources. You have the resources and the opportunity to design, build, and market a small and inexpensive generator set. I hope you do.

Thanks again for all the info.


We are interested in building a generator, or purchasing one. My husband would like any help you have to offer. He was thinking of used possibly,for the next time a power outage occurs. Which could be today! Thank you.

And a great response from David Hooper

.....The best advice I have ever seen is in the series of tips in the Tip o' the Week at the EPICENTER page.

Don't get too large a unit or the gas consumption will leave you "powerless" very soon, but one that is too small is not going to do the job.

Evaluate your absolute needs, not your "I would like to" list.

In the worst case, think of getting TWO. A larger one for short duration, power-hungry needs, and a small, quiet one for on-going use for the 2 or 3 days (or longer) that it may be needed. (All of this is on the Epicenter page, so I'm repeating myself here.)

I had built one, because I needed a 12V source to recharge race-car batteries between rounds of racing, and to recharge batteries on my travel trailer when I am camping away from "all services" campgrounds. It just happens to be also useful for long-duration use (with an inverter added) for the home. Hence my contribution to the TIPS area on the Epicenter. I also have a 2500 Watt Homelite unit for short-duration, high power consumption needs, but with the 5 HP Briggs & Stratton on it, it is both noisy and hungry. An even bigger, 4500 Watt unit could power most of a modern house, but you could look at a gallon an hour or worse, so you may have to keep 100 gallons or so around. (How's your fire insurance?)

Go back to the first tips at THEEPICENTER...I submitted the Emergency Fuel Storage tip. Then, most recently, the further plans on building one yourself.

If you are creative, you can keep the costs down even more by junkyard scrounging.

If you look at a used one, be sure that BOTH the powerplant section and the engine section are good. I bought my Homelite used, and then had to rebuild the engine (worn crankshaft). Total cost came to worse than the price of a brand new one, and I still have a well-worn powerplant section with who knows how much wear & tear on it. Grrrr!

Anyway, get one big enough for the furnace fan (I sure hope you are NOT running electric heat - You'd need a "humoungous" one to power that set up!) or fan on your wood stove or whatever, and enough for a light or two. The 'fridge will stay cold, as will the freezer, if you can plug them in for an hour or two a day (and keep the doors shut!). Alternate running the furnace with the fridge and you never need to have both going at once! Oversizing beyond that might start to get into the "I wanna" area, not the "I gotta" size.

Good luck!

Good planning is NEVER wasted. (The best part about NOT planning is that your disaster will come as a complete surprise, without your having to spend a lot of time worrying about it first!)