Introducing the Hatsuden Nabe
The material presented on this page is intended to start you thinking about what you can do today that might someday save your life. If nothing else, our "Tip o' da Week" might just make your life a bit easier when a disaster strikes. We do not present topics that cost a lot of money (like structure reinforcement.) These are "do it yourself" projects and are relatively inexpensive.
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This tip will discuss conversion of a specific family of engines, namely the Tecumseh brand of vertical shaft or horizontal shaft engines, and a specific carburetor (also Tecumseh brand) for use with propane fuel. However, the discussion is applicable to other engine manufactures, engine models and carburetors. Check with state and local authorities for applicable codes. Please see safety notes below.
-- PLEASE NOTE --
Engine conversions must be carried out by qualified technicians and/or persons who will follow all safety guidelines as contained in pamphlets NFPA 54, 58, 38 or any other publication or guidelines stipulated by local, state or federal agencies and the authority having jurisdiction. As a starting point, contact your local fire department, propane supplier and insurance company for guidance. They will be able to direct you to the correct local governmental department for additional state and local requirements.
The manufacturer of these kits reminds us that they are NOT approved for use indoors use! Call U.S. Carburation in West Virginia at 1-800-553-5608.
For information on propane safety, publications may be ordered through The National Fire Protection Association at http://www.nfpa.org.
A partial list of applicable publications are shown below:
In this project we used Tecumseh brand engines with heavy cast iron flywheels. This is a must have feature necessary for easy starting and smooth operation.Both of the engines we have used were 5 HP models.
Both engines used the same Carburetor, so the discussion below applies to both the Horizontal and Vertical engines.
Typical conversion kits require modification to the carburetor, and once modified, the carburetor can not be used for gasoline. So, if you plan to install a propane kit, you might want to also purchase a replacement carburetor so you can swap back to a gas powered configuration if needed.
Propane is easy to store in large containers, and doesn't require special treatment for it to last a long time. It is commonly used for outdoor barbecues, but also for cooking and heating in homes and trailers. Propane is sometimes used to power refrigerator units in portable applications. It can be stored in refillable containers that can be refilled at many locations friendly to motor homes, travel trailers and such. Many folks in rural areas have propane delivered to large stationary tanks on their own property.
Since propane can be used for so many applications (cooking, heating ect), it's an ideal fuel for a generator as well. I like the idea of having one type of fuel source stored that I can use in a variety of ways.
The existing carburetor on the engine must be modified to deliver propane into the combustion chamber. It sound simple, and it really is.
Basically, instead of delivering vaporized gasoline as the engine sucks in the air/fuel mixture during the "intake" cycle, the carburator delivers a propane/air mixture. The engine itself is not modified in any way. It still sucks in the air/fuel mixture, compresses it, ignites it and converts the resulting explosion (internal combustion) into rotary energy during the power stroke. Thus delivering work energy to the item which requires power (to rotate a generator armature for example).
The waste products are still expelled in the exhaust stroke, and the process continues, over and over. It's like using little controlled explosions to rotate the output shaft. Suck it in, compress it until it's explosive, blow it up, and use the explosive energy to rotate the output shaft. That's the way an engine works!
OK, enough said... A propane conversion just swaps one kind of fuel for another, and the other principals are the same.
We contacted the experts in carburetion and asked for help! They said, "been there, done that, been doing it for years." The key is a vacuum controlled flow rate regulator, linked directly to a modified carburetor.
This conversion kit works because the air/fuel mixture is automatically adjusted as load changes are made. This automatic adjustment is only possible because this special flow regulator is linked by a vacuum hose to the carburetor itself.
This allows the flow regulator to automatically sense changes in engine intake vacuum which is directly related to engine load changes. So, if more load is added, the carburetor throttle changes, which causes an increase in intake manifold vacuum. And this vacuum causes the flow regulator in the propane conversion kit to increase fuel flow to keep the air/fuel mixture ideal. Without this feedback, it's impossible to keep the fuel/air mixture ideal and the motor running!
At the heart of the conversion is the modification of a carburetor to deliver the alternative fuel, and to provide a feedback method (a port to the vacuum inside the carburetor) to an external propane fuel delivery flow regulator, which is designed to accept the vacuum feedback and adjust the fuel delivery flow rate. This special vacuum flow regulator is like having an extra hand automatically adjusting the regulator output knob, keeping the air/fuel mixture ideal!
As with all of the Tip of the Week episodes here at TheEpicenter.com, we have tried to be technically correct in our discussion. As always, I'm sure we will be corrected here or there, but what I'm trying to get across is that the conversion is fairly straight forward. The most difficult part of the conversion is drilling one hole in the carburetor.
So without further delay, lets talk about what's involved in converting one of these engines with an off the shelf conversion kit to run on propane.
The main task in modifying the carburetor is to replace the existing gasoline fuel delivery tube (the red plastic tube) with a brass propane delivery tube.
To do this will require drilling out the opening in the carburetor where the old jet was located. The new brass jet (and some other fittings and a valve assembly) will take the place of the gasoline delivery jet.
Another brass fitting (the slow running fitting) will be replaced with a larger (hollow) fitting, which will serve as a vacuum feedback port to the vacuum controlled flow regulator.
Unused air passages which are only required for gasoline fuel use will be sealed with RTV silicone.
The photos shown are for a specific model of carburetor but the modifications are similar on all carburetors.
Shown below are the spare parts from the original carburetor that are not required.
Here the system is shown before being installed on an engine (for clarity).
The modified carburetor is connected via two hoses to the vacuum controlled flow regulator. The hose connected to the bottom of the carburetor delivers propane or natural gas to the new jet.
The second, smaller hose is connected to the side of the carburetor where the vacuum fitting has been installed. The other end connects to the vacuum control feedback port on the flow regulator.
The third hose connected to the vacuum flow regulator could either be connected to the low pressure household feed for natural gas use; or, with the a portability tank kit, it can be connected to a portable propane tank using the special 12 PSI regulator included with the portability kit.
Shown here is the motor and flow regulator mounted on a pressure washer cart, and a close up of the flow regulator connected to the carburetor. The next shot is of the completed project.
In this project we used our direct drive alternator bracket and couplers to connect a 93 amp GM alternator and charging cables to the propane powered motor.
The best thing to do is use our search tool and enter "propane conversion" and the brand of your motor. Like this: Briggs & Stratton propane conversion kit:
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