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-   -   Wheel Ballast Vs. Soil Compaction (https://www.mytractorforum.com/45-backyard-round-table-l-g-tractor-related-topics/1237146-wheel-ballast-vs-soil-compaction.html)

Willscary 01-23-2018 01:50 PM

Wheel Ballast Vs. Soil Compaction
 
Recently there have been a few threads where ballasting was discussed. In several instances liquid ballast and wheel weights were brought up and members had dismissed this weight inferior or not acceptable. The main reasoning is that liquid ballast is basically permanent and that wheel weights are hard to remove. Apparently, ballast is only useful as counterweight for heavy front or rear attachments. Some people here are recommending suitcase weights and chains as the only things needed for plowing or blowing snow, and that summer mowing should be done with no added machine weight because of soil compaction and ruts.

While I understand that certain places may have very loose, soft soil that might even be wet most of the time, I would be willing to bet that most people have turf that is plenty firm enough to handle the weight of a ballasted tractor.

Here is my reasoning...I will use my equipment and my life as an example.

My tractor, with the home made rear hitch and the permanently mounted Johnny Bucket sub-frame weighs about 850 pounds when fully fueled (without the mower deck). With my big butt in the seat it goes to 1,120 pounds. Of this weight, 650 pounds are on the rear wheels and 470 pounds are on the front wheels. The ground under each rear wheel sees 325 pounds. The contact patch for each rear wheel is 9" wide and 5" long, or 45 square inches. This works out to just about 7.25 pounds per square inch of pressure on the ground. Filling each tire with Rimguard added 77 pounds. The cast iron wheel weight added another 56 pounds for a total of an additional 133 pounds per wheel, raising the total weight for each wheel to 458 pounds. This raises the pressure exerted to the ground to just over 10 PSI.

I did not add in the weight of the deck because on my machine, the deck is free floating...it rides on the rear rollers directly on the ground. It does exert some downward pressure on the front wheels, but really none on the rears. If you have a suspended deck, your results may be different.

Here is the kicker...

I went out and got the two pairs of shoes that I would normally be wearing when out and about on the lawn. One is a pair of "deck shoes" and the other is a pair of tennis shoes. the bottoms of the shoes are not flat. I wear 12-1/2 EEEs, so I have big feet to help distribute the load of my body, but the fact that the shoes are not flat changes the actual contact patch with the ground. So...I put on each of the shoes, stepped in some shallow water, then stepped onto paper to get an outline of the actual contact patch of my shoes. Interestingly, these are two completely different types of shoes. they are not flat like basketball shoes and their contact patches looked completely different. What was interesting is that both shoes had nearly identical overall contact areas. The shoes were about 12-1/2" long and more than 4" wide at their widest points, yet their total contact area when I stepped on the paper was only 31" for the deck shoes and 30" for the tennis shoes.

When I stand on my lawn, I am exerting roughly 4.5 PSI of pressure on the ground. When a person walks, they generally have most of their weight on one foot at a time, which means that if I evenly place my feet down in that manor, I am then transmitting about 9 PSI to the ground just by walking. If you add to this that we generally don't walk flat footed, but instead heel to toe, this pressure becomes even greater.

Trial number two...OK, so I am a big guy. What if I was a young woman, very slim and very fit? Well, my 19 year old daughter is just that. She is a very athletic and fit size 2. She weighs 115 pounds. I di the same thing with her tiny little size 7-1/2 womens shoes. Her contact patch was only 13 square inches per shoe. Guess what? It worked out to within two decimal points of my results...almost exactly 4.5 PSI when standing.

With these measurements, I would say that if my daughter runs across my lawn in her tennis shoes, she exerts a higher PSI on the soil than my Prestige with my fat butt on the seat plus 133 pounds of wheel ballast on each side.

So, after all of this...do we really need to worry about soil compaction from ballasting our rear tires? Will the added 3 PSI really make that much of a difference?

I will say that the difference when mowing my ditch or driving up my steeper areas is much more stable and produces much less wheel slippage than prior to ballasting the wheels.

Thoughts?

Iron Mike Golf 01-23-2018 02:00 PM

Re: Wheel Ballast Vs. Soil Compaction
 
I find these things are sensitive to soil conditions. I can mow with my JD300 using loaded ag rear tires in July or August without any issue. April or May is another matter, though.

Willscary 01-23-2018 03:15 PM

Re: Wheel Ballast Vs. Soil Compaction
 
Quote:

Originally Posted by Iron Mike Golf (Post 11568986)
I find these things are sensitive to soil conditions. I can mow with my JD300 using loaded ag rear tires in July or August without any issue. April or May is another matter, though.

I had mentioned this early in my post...some soil is just too soft or too wet. then again, if 10 PSI from the tires is enough to cause the compaction and rutting, then just my walking or my daughter's walking or running should do the same damage. In other words, if the ground is soft enough to cause the tractor to sink a bit, then my daughter and I should both leave tracks if we run through the same area.

In your case, If I had to venture to guess, ag tires would compact and destroy the ground much more easily because the ground patch would be MUCH less, meaning that all other things being equal, you exert a MUCH higher pressure on the ground than if you were running turf tires.I would think that the contact patch of the bars is probably only about 1/4 of what the contact patch of similar sized turfs are, so you would be exerting 4 times as much pressure on the ground,,,and that might even be conservative.

TUDOR 01-23-2018 10:48 PM

Re: Wheel Ballast Vs. Soil Compaction
 
The internal pressure in my tires is 14 psi. The area of the contact patch will be consistent with that pressure for the weight supported. A higher pressure will result in a smaller contact patch and a lower pressure will result in a larger contact patch for a given tractor weight. Likewise, a heavier tractor will result in a larger contact patch and a lighter tractor will result on a smaller contact patch for the same pressure.

I noted in another thread how ballast is carried on a tractor.

- Liquid ballast is carried by the ground. (In actuality it's supported by the surface area of the tread blocks in ground contact. This results in a major difference in ground pressure between turfs and ags.)
- Wheel weights are carried by the tire.
- Rear end counter weight is carried by the axle.
- Chain weight is divided between being carried by the ground and carried by the tire.

For all intents and purposes, wheel weights and counterweight have a minimal effect on pressure in the tire and therefore ground pressure. The tire merely squats a bit to provide more ground contact area to support the additional load.

Because liquid ballast is supported by the ground (it is merely contained within the tire), it has no effect on the area of the ground patch, but it does increase the ground pressure for that patch with its added weight. So much for liquid ballast being inferior for traction.

Liquid ballast and wheel weights are for traction. Counterweight is for balancing the weight of front end implements during transport, and traction when the implement is on the ground doing work.

The order of ballasting for winter traction is:

- Liquid ballast.
- Wheel weights.
- Chains.
- Counterweight.

Don't believe me? Try it out at the start of the season. I learned this lesson over 40 years ago, one step at a time, and it has served me well. My GT used liquid ballast and chains and, when necessary, counterweight when the back blade wasn't in use due to a heavy snow load. My heavier 4wd SCUT uses liquid ballast and, when necessary, counterweight when the back blade isn't in use due to the heavy snow load. I have a set of wheel weights, I just don't need them due to the much heavier weights of those tractors. The GT weighed 2450 lb with operator, and the SCUT weighs about 2600 lb with operator. Both are FEL equipped. The GT does snow duty better because of the chains.

When walking on the ground, the broad surface of the toe of the footwear is still in contact with the ground when the back edge of the heel of the other foot contacts the ground. With the forward motion, the heel impact puts considerably more stress on the ground than when the foot is flat. That's why the back edge of the heel of footwear shows major wear compared to the rest of the heel or the sole of older boots and shoes.

PA318Guy 01-23-2018 10:58 PM

Re: Wheel Ballast Vs. Soil Compaction
 
Quote:

Originally Posted by Willscary (Post 11568962)
Well, my 19 year old daughter is just that. She is a very athletic and fit size 2. She weighs 115 pounds.

You know that you are dead to her if she see's this right?? :sidelaugh

Willscary 01-23-2018 11:03 PM

Re: Wheel Ballast Vs. Soil Compaction
 
Quote:

Originally Posted by PA318Guy (Post 11570730)
You know that you are dead to her if she see's this right?? :sidelaugh

:tango_face_grin:

Willscary 01-24-2018 12:04 AM

Re: Wheel Ballast Vs. Soil Compaction
 
Quote:

Originally Posted by TUDOR (Post 11570682)
The internal pressure in my tires is 14 psi. The area of the contact patch will be consistent with that pressure for the weight supported. A higher pressure will result in a smaller contact patch and a lower pressure will result in a larger contact patch for a given tractor weight. Likewise, a heavier tractor will result in a larger contact patch and a lighter tractor will result on a smaller contact patch for the same pressure.

I noted in another thread how ballast is carried on a tractor.

- Liquid ballast is carried by the ground. (In actuality it's supported by the surface area of the tread blocks in ground contact. This results in a major difference in ground pressure between turfs and ags.)
- Wheel weights are carried by the tire.
- Rear end counter weight is carried by the axle.
- Chain weight is divided between being carried by the ground and carried by the tire.

For all intents and purposes, wheel weights and counterweight have a minimal effect on pressure in the tire and therefore ground pressure. The tire merely squats a bit to provide more ground contact area to support the additional load.

Because liquid ballast is supported by the ground (it is merely contained within the tire), it has no effect on the area of the ground patch, but it does increase the ground pressure for that patch with its added weight. So much for liquid ballast being inferior for traction.

Liquid ballast and wheel weights are for traction. Counterweight is for balancing the weight of front end implements during transport, and traction when the implement is on the ground doing work.

The order of ballasting for winter traction is:

- Liquid ballast.
- Wheel weights.
- Chains.
- Counterweight.

Don't believe me? Try it out at the start of the season. I learned this lesson over 40 years ago, one step at a time, and it has served me well. My GT used liquid ballast and chains and, when necessary, counterweight when the back blade wasn't in use due to a heavy snow load. My heavier 4wd SCUT uses liquid ballast and, when necessary, counterweight when the back blade isn't in use due to the heavy snow load. I have a set of wheel weights, I just don't need them due to the much heavier weights of those tractors. The GT weighed 2450 lb with operator, and the SCUT weighs about 2600 lb with operator. Both are FEL equipped. The GT does snow duty better because of the chains.

When walking on the ground, the broad surface of the toe of the footwear is still in contact with the ground when the back edge of the heel of the other foot contacts the ground. With the forward motion, the heel impact puts considerably more stress on the ground than when the foot is flat. That's why the back edge of the heel of footwear shows major wear compared to the rest of the heel or the sole of older boots and shoes.

Well, that makes sense...my tires are filled to 10 PSI. I also agree with the rest. Liquid and cast iron wheel weights!

Part of my point is that these are useful in the summer also and add little to soil compaction.

Sergeant 01-29-2018 03:56 PM

Re: Wheel Ballast Vs. Soil Compaction
 
Quote:

Originally Posted by PA318Guy (Post 11570730)
You know that you are dead to her if she see's this right?? :sidelaugh

:sidelaugh:sidelaugh

Tractor-Holic 01-31-2018 12:32 PM

Re: Wheel Ballast Vs. Soil Compaction
 
I've seen a woman's high heels sink into asphalt on a hot summer day before!...
They say the amount of force on a high heel's tip is greater than just about anything else..
BTW--the woman was tall,skinny,and blonde,not some fattie!..

TWG1572 01-31-2018 02:51 PM

Re: Wheel Ballast Vs. Soil Compaction
 
I think the assumption that people don't cause soil compaction is a bit flawed. They do. That's what paths are. I've got one going from my driveway to back deck that I have to aerate every year just to break up the hardpan. If I step in wet turf, I'll leave an imprint.

Probably the key difference here is that a tractor tire leaves a strip of compaction wherever it goes, where a footprint is just a single spot. I have a front lawn where the prior owner much have followed the same path mowing every time. You can feel the grooves he made running in the same path every time when you cut it across them .

I think the right answer is to use enough weight where you feel safe, stable, and have good traction on any slopes you might have. More than that is overkill, and you are unnecessarily compacting the ground. You alone know how many pounds of weight that is going to take.


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