propane conversion or natural gas conversion for small engines

this page is to document a very interesting setup my father in law
Donald fabricated to convert small gasoline engines to run on
natural gas or propane.

Sadly Donald passed away a some years ago now and his collection of small engines has been sold and scattered to the winds
but perhaps some people will find the simple technique he used to make them run without having to mess around with messy gasoline interesting for academic purposes although i do not recommend using it as there are proper kits available and this settup is not safe for unattended operation.

To convert 1-5 HP gas engines to natural gas or propane he modifies a poppet regulator (Maxitrol RV48 works well)
by removing the pressure regulating spring and cap. disassembling and replacing the diaphragm with a piece of a latex surgical glove to get the regulator
to fully close but still open under vacuum .  That way if the regulator is oriented up side down so that gravity helps hold the diaphragm valve closed no gas will flow until vacuum created by the engine sucking air through the venturi draws the gas through the regulator.
for use with LP gas he puts a gas grill type regulator between the tank and the modified poppet valve.

poppet regulator

Next he constructs a venturi using copper water pipe brass shim stock and 3/16” O.D. thin wall brass tubing.

he selects the size of copper pipe that best fits over the air inlet of the carburetor on the engine and cut a piece 2” long.
(¾” rigid copper water pipe seems to work well for most small engines.)
then he rolls 2 pieces of shim stock into cone shapes about 1” long with the large ends being the same size as the I.D. of the copper pipe
and the small ends being between 5/16” and 3/8” larger
for larger engines smaller for smaller engines but 5/16 to 3/8 seems to work well for most small engines.
He Solders the 2 cones inside the 2”piece of water pipe so that the small ends meet in the middle
then drills a 3/16” hole though the side of the water pipe and though the shim stock just to side of were the 2 cones meet
so that the side of the hole cuts the edge of one piece of shim stock .

Then he cuts the end of the 3/16 O.D. brass tubing at a 45 degree angle.
Then inserts it into hole in side of water pipe aligning it so
that the angle cut lines up with the angle of the shim stock as best he
can and solders it in place.

next he fabricates a flow valve to go between the poppet regulator and
the venturi by drilling and taping a hole for a small machine screw
into one side of a piece of tubing so that when the machine screw is
screwed all the way in till it touches the other side of the tube it
pretty much blocks the entire tube. that way he can adjust the fuel air
mix by turning the screw in or out.

then he plumbs it all together with assorted tubing and hose in this
order, gas grill regulator (only needed for LP), modified poppet
regulator, flow valve, venturi. and then mounts the venturi on the air
intake of the carburetor of the engine being sure to get a relatively
air tight seal between the venturi and the carburetor.


this is posted for academic purposes only if you choose to use this information you do so at your own risk and I will not answer questions on this subject thank you.


the redneck dipole.

this is how i built my first antenna for HF its quick and dirty keep in mind that if you want a dipole that is going to last years and years do it the right way with a proper balun center insulator and proper end insulators but as a new ham you most likely will be experimenting with many antennas and moving through them quickly so it makes no sense to spend a huge amount of money on each one.

If you have some way of checking swr so you can tune the antenna then this antenna is a breeze allot of your modern radios have a swr meter built into them if your running an older rig like me then your going to have to beg, borrow, or steal a swr bridge when i built this antenna i borrowed one from a local ham and he ended up letting me hold on to it as a long term loan sorta deal.

anyway what your going to need is a so-239 panel mount a machine screw and nut to fit one of the mounting holes in the so-239  i small piece of rigid plastic i used a piece of the lid of a tidycat bucket about 3 x 3″ square this will be your center insulator . your going to need some insulated wire most any wire will do you can get 75ft rolls of 2 conductor 20 gauge speaker wire for less than $10 you can measure out enough for 1 side of the antenna cut it then split the 2 conductors apart use one conductor for each half of the dipole

this dipole can be made for any hf band within reason using this calculator  20 meters for a first antenna for a new general be a good place to start  or 10m for a tech looking to get on the tech portion of 10M

dipole calculator

use the dipole calculator linked above to decide how long to make the wires make sure to make your initial cut long because you are going to tie the wire though holes in your center insulator then attach the wires to the so-239 one side with the bolt the other side will have to be soldered to the center pin.

because the wire is insulated we do not need end insulators just bend the wire over in a loop and tie non conductive rope to it. believe me i had this antenna up an entire winter swr never changed.

calculate your antenna long to start and shorten equally on both sides until swr is good. word of warning though if you have more than a couple feet of wire bent under and the end not shorted back onto the main radiator say for instance you built it for 20M but you want to experiment with 17m so you try to shorten the antenna by folding the extra wire under. well i tried that and after a certain point swr goes crazy unless you strip a bare spot in the main wires and short the ends of what is folded under to it.

you will need to wind a 1:1 choke balun in the end of your coax to do that measure out 10 feet of coax in the end of your coax a few inches from the connector were it connects to the antenna then wind that 10′ into 7 equal flat coils and tape it up make sure the the end of the coax going to the radio and the end going to the antenna are on opposite sides of the coil and do not touch. this is directly out of the aarl handbook 2004 edition. this will work with rg-58 rg8x and rg-8 coax and is multi band but works better on  10m-20m i am told

as far as coax if your building this for 10M get good coax but for 20m or 40m if your on a budget rg-58 will work on 20m over 100′ of rg-58 would be about 1.4db which means your getting 71watts to the antenna stepping up to rg8x would only get you 4-5 extra watts at the end of the cable on 20m and rg8x is twice the price usually.

the cheapest way to get coax is to buy just the coax no ends and buy solder on pl-259 ends and adapters then find a local ham to teach you to solder them on. or you can buy a crimping tool and use crimp on ends.

if your going to leave the antenna out in the weather tape the so-239/pl-259 connection with the weatherproofing method of your choice. electrical tape will work fine for the short term.

best how to solder pl-259 connectors videos end insulatorbalun