Running LP Tractors

Have 2 d17 propane for sale. Ryan 402-469-1738

I've thought about it too but my spin is that I wonder if you can have a methane digester and have the tractor run on methane.  

I run a WD45 lp as a chore tractor. I think that LP will be back on more Automobiles and tractors. The way our fuel production is going, we have a great supply of LP. You speak of a LP not having the HP as a Diesel. A 190 LP will pull the same plows as a 190 diesel. In twenty years you will see LP tractors in the field again.

Many years ago Bob Gretencord was the MM dealer at Remington, In. He was famous in the area for making "STRONG" Minnies, and getting horsepower out of the other brands. The Remington area, sitting on US 24 is a good divider between heavy black, prairie dirt to the south, and a combo of sand hills and heavy dirt to the north. M's to the south pulled 2 bottom plows, and to the north of 24, would generally pull a 3-14" plow. Most of his customers were in the black dirt south of town. There are many secrets that died when Bob passed away, but some of the things known are that a Moline can have the "jugs"(the cylinders) replaced with larger bores, and different cranks(off the shelf) can be installed, different heads are available to raise compression. And of course carbs, or maybe more correctly, mixing chambers can be replaced, along with dry air filters vs. oil baths. I had one of Bob's G-1000's for a while. It must have been putting out in the neighborhood of 135 hp, based on the way it pulled my chisel plow! That from a 108 hp factory tractor. I had an Oliver 1855 with a 1955 motor at the time and I hooked that chisel to it one year. You know, nicer cab, easier driving, diesel vs. slow filling with LP, etc. I drove to the field and dropped the plow in the dirt, and instantly spun out, trying to raise the plow to pull it, I found a spot where I had traction, and killed the motor!!! This was with 119 dynoed horsepower. So I headed back to the house and switched tractors. I did not have a tractor that would pull that plow until I got my 7060!

Horsepower is avilable with LP, and can be had! Dave Stangle campaigned his "Solid Junk" G1000 for several years and was very competitve with Red, Green, Orange, and all the rest in the unlimited classes. He never had real competition until the advent of the turbine engines!

Depending on who's numbers you use, LP is in the 100-120 octane range, and yes, there is a slight "give-away" in power, but like diesel, with higher compression and a healthy slug of gas, power can and will be made with it.

My G-1000 had the factory 30-35 gallon tank, and mounted on a platform in front of the radiator was another tank. If I filled both tanks, some 60 gallons, I was good to go for all day, until suppertime when I had to fill again. Fuel was cheap, and I had work to do so economy wasn't the big concern it is today.

Hope this gives you some answers to questions 37, like the other guys said it can work for you!   joe 

Dave, 

Sandknob I wonder about those milk trucks, but the only driver I found to talk to didn't know whether the trucks ran on vapor or liquid injection. They are all Kenworths, class 8's and sound almost like a diesel engine. They do seem to run with all the rest of the trucks as far as power goes.

For Jeremy's original question:

One can easily set up a spark-ignition engine to RUN on propane... even if that engine is not originally built to suit the fuel burn character of propane, it'll do it just fine- Without modifying the internals, but adjusting ignition timing, you'll have a little loss in output, but the cost of fuel will make the pain in your back pocket much, much lower, and ease the pain under your throttle lever much less.

There's some basic components to the LP conversion system, and they all revolve around simple-principles that exist in gasoline engines... it's just that the fuel's character makes things happen in a different way.

Propane tanks have two types of withdrawal systems-  liquid (off the bottom) and vaporous (off the top).  Your gas grill runs off vapor... and if you have a big grain dryer, it most likely draws off liquid.  Difference being, when you pull a gallon of liquid through a small line, you're still moving LOTS of energy.  When you pull vapor off the top, it takes more VOLUME to get the equivalent energy.

Liquified gaseous fuels don't WANT to be a liquid- they want to boil at ambient temps... (except one gotcha I'll note later).  This means that if you open up the gaseous withdrawl, you'll blast gaseous propane into the sky.  If you open up the liquid withdrawl tube, you'll have a massive geyser of liquid shooting straight up, and then evaporating.  BOTH scenarios are rediculously deadly, so please don't do it.  You're essentially messing with a steam engine here, but the steam is really, really, really flammable.

Okay, so in a vaporous withdrawl, you have a tank which has pressure in it, you'll feeding a 'first stage' regulator that drops the tank pressure (on propane, anywhere from near zero, to up to 250psi or so) and holding it around 3psi or so.  That goes through your transport plumbing, to a 'Second Stage' regulator at the USE point, typically drops it down to a pressure of about 11" Water Column (much lower than 1psi... just enough to raise the water level in a tube by 11 inches, and yes, you can make a WC manometer at home, with clear plastic hose, some water, and a permanent marker!).

So it's down to 11" WC.  Now it comes to the engine, where it needs to be fed to the engine in a variable state, to match engine demand.

There's also a gadget that introduces the vapor into the airstream, and mixes it with oxygen so it'll burn. 

The gadget is called a 'mixer', and sometimes, it's a dedicated device (like a carbeurator, or an added device before, or after a carbeurator)...

And then there's some way for the fuel flow to be controlled.

In a liquid fuel carbeurator, fuel sits in a bowl, and when airflow occurs through the venturi, the pressure difference (vacuum) draws fuel up through the jet, where it sprays (atomizes, evaporates) and mixes with air.

Propane, in a vaporous system, is already evaporated... we just need a way to CONTROL it.  Some 'Mixers' have a mechanical technique for varying fuel flow based on airflow... a plate or something sitting IN the airflow path, that as air flows, it lifts the plate, which operates the fuel metering valve.  IMPCO CA-series comes to mind here...

There are other techniques for introducing fuel and metering... one is drilling a hole in the bottom of the carbeurator or into the manifold, and just feeding the fuel in... (frequently called stub-in) and using some OTHER method to control fuel flow.  One of the methods, is by using something called a 'demand regulator', which takes in the 11"wc vapor, and monitors vacuum at the mixer or stub-in, and the DR does all the dirty work, just feeds it in as vacuum demands it.  Slick gadget.

Now, for LIQUID delivery, the same concepts apply... out of the tank, through first stage regulation (different part, but same concept... all about safety), then into a gadget called an 'evaporator'... basically a snail-shell shaped vortex that has a water jacket around it, wherin engine coolant circulates to cause the liquid to boil to vapor.   Oftentimes, the first stage reg and evaporator are the same thing.  From there, it's a high-volume vapor, so on to the engine just like the vapor-based.

The 'gotcha', is that with LP, it's boiling point is down around -20F or so.  If you watch the pressure gauge of your home tank, you'll see that even if you NEVER use the tank, the pressure inside varies.  On a hot day,  it'll hit 250psi or so (pressure relief valve will pop off a bit when that happens)... on a really cold day, it may drop darned-well zero.  In order to get vapors to flow, there needs to be SOME pressure... if there is no pressure, there'll be no flow.

If you're doing vaporous withdrawl, and only have say... 4psi to work with, you'll have 4psi with a substantial restriction flowing through the plumbing to your load.  If you're doing liquid withdrawl, you'll have that same 4psi, and perhaps a little more restriction because you're pushing liquid... but the amount of VOLUME you're pushing through is essentially same regardless of vapor or liquid, but with LIQUID, you have substantially more energy coming through with unit volume, than you would vapor.  This is why bigger engines are liquid-fed... they evaporate JUST before the mixer.

Here's another gotcha:  When your tank is totally full, there's very little space at the top of the tank for the propane to 'boil' to vapor.  This is one of the reasons why you don't want the tank to be filled over 80%.  NExt, if you're using a very small tank, there will be very little surface area in that tank from which it can boil, and as a result, the tank will get very, very cold, and the propane will stop boiling.

This 'cold'... is Boyle's Law (Combined Gas Law) at work.  (Pressure = Volume)/Temperature.  Basic concept:  When you compress a gas, it gets hot.  When you discharge a compressed gas, it gets cold.

Demonstration:  Place your hand on the outlet pipe of your compressor while it's running.  Place hand in your mouth, because it hurts, and notice- your skin tastes very warm.  This is because the compressor is taking a big volume of air, and cramming it into a small space.  The ambient heat energy of all that air, is being 'squashed in', and hence, is trying to get out.  Compressor's intercooler and aftercooler help improve compressor efficiency (and lifespan) by giving that heat a very quick path out of the air... and it also helps dry the air... but that's next week's lesson)

Now, allow compressor to shut off, and open air-hose at other end of compressor tank, and let it blow.  Hold onto that nozzle, and notice that, even though it's 85F in the shop, that nozzle is starting to develop frost.  That is because the expanding air is PULLING HEAT from the area around it...

Now, if the air temperature was low enough, even with that tank pumped up to full pressure... cool it SO FAR that the air pressure in the tank would drop so low, that opening the valve would NOT result in much airflow coming out... it just sits there.

Propane, when in liquid form, will want to STAY liquid below -35f... and it will impart NO pressure on the lines... so you'll have NO fuel flow.  In effect, it'll be just like gasoline... it'll stay a liquid.

Sucks when it's -35 in the midwest on a really, really cold night... and there's not enough pressure in the propane lines to keep the furnace burning.  Grandpa's trick times when it was too cold to develop pressure...  build a little snowbank around the up-wind side of the propane tank, and place a can of STERNO under the tank... keep the flame no closer than about 3-4", and it'll warm it enough to get pressure to build... not alot, but enough.

So there's your propane-engine primer for the day.

I have heard that LPG stores well with no deteriration in long storage periods. Any fact to this? Mike