This took forever to find a solution that worked. Eventually I drilled a hose hole in a cap and a smaller hole for my pressure gun. After I rigged up this makeshift air pump, it takes the following steps:
To prepare:
- I cut the 1/4" ID hose to length and stuck a length of brake line in the hose to keep it straight and held at the bottom. YMMV.
- Drill 3/8" hole in cap carefully (this took like 3 tries).
- Drill 3/16" hole for my air gun. YMMV.
- Stick hose through big hole.
Once for each tire:
- Deflate/remove valve core
- Jack up rear end
- Put some blocks of wood under the tire (or skip this, perhaps, if your tractor is much heavier)
- Stick 1/4" ID hose onto valve stem - it will remain on until the tire is full
- Let down rear end and sit on tractor if needed to deflate.
Steps that I used per gallon:
- Open a new gallon jug
- Thread cap with hose and holes onto a new jug of your favorite ballast.
- Shove air gun into the small hole
- Jack up rear end so you aren't trying to pressurize against gravity.
- Gently pressurize the jug. Engage common sense mode. They are made to take some pressure so they expand quite a bit before anything bad happens. Worst thing that happens is some splashing and mist leaks around the cap.
- It will pump the entire gallon into the tire in just a couple of minutes.
- Remove air gun, unthread cap, mount the hose somewhere reasonable
- Let down the jack to deflate the tire and displace as much air as you can.
- Sit on tractor (probably not necessary for a much heavier machine) to get all the air out
Repeat from the top until the tire is full (up to the valve stem).
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I've got about 9.5 gallons pumped in between the two tires. One tire will take probably most of the remainder. I threw one gallon in the freezer overnight to see what it would do around 0F. It turns to this slush/slurry but still moves around and this is all I needed to see. Of course now it won't pump right so I placed it on top of the water heater to warm up and I will pump the rest in.
Oh, at the end, you do the following steps, per tire:
- You will know the tire is full when the valve sitting in the 12 o'clock position still pushes liquid OUT of the hose after you stop pumping. This means the level as it as high as it can be (and should be, if you want an air cushion).
- Quickly remove hose and shove valve stem in and tighten. I did a terrible job at this compared to the left side, mainly because I had the valve in backwards so a bunch of fluid pushed out before I figured it out. This may mean that the left side is over the level of the valve stem. Meh.
- I inflated to 13 psi and will test ride when done to see if this pressure still seems about right. I could see it taking a tad less since the air spring will be stiffer with less volume but maybe it's a wash....this isn't the space shuttle, as they say.
Anyway, 5 gallons is around 42.5 lbs (minus jug weight but they don't weigh much). So I would say probably right around 41 lbs per tire? My wheel weights are only 31 lbs each so....this more than doubles it. That will definitely be worth something.
I'll revise that down slightly.
Each jug weighs 4.4 oz including the splash at the bottom of each. So each gallon is 8.5 lbs minus 4.4 oz, so 8 lbs 3.6 oz per gallon, and about 9.5 gallons combined are in the rear tires, for a total additional ballast of 78 lbs or 39 lbs per tire. Slightly under my initial estimate (I expected to get more than what I got in the last tire and if I wanted to I could have put the level above the valve stem) but still more than the wheel weights. Total ballast on the rear end is 140 lbs pretty much exactly, none of which is supported by the axle, just the wheel/tire itself. Not bad. But if I want more I'll have to build something to hang off the rear frame. Fortunately I think this is going to suffice for what the capability of this machine actually is.
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