Estimating center of gravity John Deere 790

[pretendfarmer]

I will be hauling my JD 790 close to 2,000 miles inside my enclosed trailer. I am unable to pull it all the way forward because I have stuff in the front area. My question is where the center of gravity, front to rear, of the tractor with FEL would roughly be. With the FEL and the engine up front, I would assume it would be a bit forward of the actual center measurement rear to front. Is this a wrong assumption?

Right now, as the tractor sits in the trailer, it is essentially centered evenly over the two trailer axles. If I take a tape measure, I have roughly 5'+ in either direction - rear of the tires to the rear, front of the bucket to the front. I do have some heavy tools and things in the front of the trailer - jacks, vise, all sorts of power tools for carpentry, fasteners, etc., but I don't know what all of that weighs. I hauled it about 35 miles and it seems ok, but I am wondering if the tractor is sitting back too far seeing as how 60% of the total weight should be in the front of the trailer. I don't have a way of weighing everything that's in the front of the trailer. I'm just trying to ballpark all of this.

 

[zzvyb6]

You don't say what kind of hitch you have (load equalizing of not), or the capacity of your towing vehicle. As someone with 40 years experience with this situation working for a vehicle manufacturer, my first recommendation is what we call "level frame" on the tow vehicle. This is because the tow vehicle (presumed to be a truck of some sort) is the dominant player in controlling all the actors in the vehicle dynamics actions, so the tires & suspension are specified, designed, and tested in this configuration, even cooling and brake distribution management.
Same for the trailer. Try backing the tractor onto the trailer if these 2 conditions can't be met.

 

[toolslinger]

Can you get a scale under the tongue of the trailer and see where you are? you can even do it with a bathroom scale if you use a lever to reduce the load on it by 1/2, or 1/4 and do a little math.

 

[pretendfarmer]

You don't say what kind of hitch you have (load equalizing of not), or the capacity of your towing vehicle.

Because that was not my question. I have a 4wd Ram 3500 dually diesel pickup.

 

[crashz]

I think I'd want to know my total weight on each axle after the truck & trailer is fully packed. Find a truck scale, pull in loaded with truck and trailer and get an axle weight on each axle. Run it into the parking lot and drop the trailer. Then get axle weights on the truck only.

I'd do this a week or so ahead, in case you want to change equipment or want to ship stuff out separately.

This gives you a lot of information. You will be able to find out the direct load of the tongue weight (not exach a 1:1, but close) and the effect on the tow vehicle. You may find that that frontend is too light and a weight distributing hitch is needed. Or maybe just a few things need to be shuffled around in the trailer.

BTW - do you have loaded rear tires? That will affect the COG and may make backing the tractor on more effective.

 

[pretendfarmer]

The rear tires are not loaded. I was just wondering about the center of gravity for the tractor.

 

[RjCorazza]

Eyeballing the COG of the tractor is information, but not the only (or best) information. I don't know the cog of your machine.
If you absolutely cannot weigh the axles or tongue weight, I would at the very least measure the trucks suspension empty, then again when loaded with your estimated positioning. You will not know how much weight is on the hitch in pounds, but you will at least know there is a positive tongue load.

I use a small hydraulic tongue scale made by Sherline (?) that lets me get the tongue weight correct at 10-15 % of the gross trailer weight. The previous post about using a bathroom scale and lever is totally legit also. Plenty of instructional videos available.
Good luck, and safe travels!

 

[pretendfarmer]

Eyeballing the COG of the tractor is information, but not the only (or best) information. I don't know the cog of your machine.
If you absolutely cannot weigh the axles or tongue weight, I would at the very least measure the trucks suspension empty, then again when loaded with your estimated positioning. You will not know how much weight is on the hitch in pounds, but you will at least know there is a positive tongue load.

I use a small hydraulic tongue scale made by Sherline (?) that lets me get the tongue weight correct at 10-15 % of the gross trailer weight. The previous post about using a bathroom scale and lever is totally legit also. Plenty of instructional videos available.
Good luck, and safe travels!

I don't have a scale, so I think the best thing for me to do is just hitch it up and head to a scale. I already know the tare weight of my truck is 7,840, so if I pull onto the scale without letting the trailer tires on, get a weight, then pull onto the scale to get the gross, then subtract the 7,840 I will know where I sit in terms of tongue weight and gross trailer weight. Thanks everybody.

 

[RjCorazza]

I don't have a scale, so I think the best thing for me to do is just hitch it up and head to a scale. I already know the tare weight of my truck is 7,840, so if I pull onto the scale without letting the trailer tires on, get a weight, then pull onto the scale to get the gross, then subtract the 7,840 I will know where I sit in terms of tongue weight and gross trailer weight. Thanks everybody.

Nothing better than hard numbers!
I know you specifically asked about a JD 790 cog, but the likelihood of someone here having the same machine and configuration is slim. Them knowing the actual cog even slimmer.

 

[pretendfarmer]

Nothing better than hard numbers!
I know you specifically asked about a JD 790 cog, but the likelihood of someone here having the same machine and configuration is slim. Them knowing the actual cog even slimmer.

For me it's just easiest to know the center of gravity of the tractor in order to effectively load the trailer. Seems ok now but for some reason I am wondering if it needs to be forward a little more. It's not that my truck can't handle it, it's just that I don't like to have a load too far to the rear, so I am exercising caution. A poorly loaded trailer is a poorly loaded trailer, regardless of the tow vehicle.

 

[zzvyb6]

If it's a dual axle trailer, the simplest measure can be made by:
1) with the trailer unhitched, use some ballast to balance the trailer tongue to zero hitch weight as best as you can. Ramps off or upright.
2) hook the trailer back up and slowly crawl the tractor forward until the hitch weight goes from negative to positive. You need to have the ramps in the off or upright position as in step 1
3) The tractor + loader combo's c.g. will be located where it passes by the walking beam center, as there is no pitching moment at this point.

 

[ljjhouser]

I think you had it in post $8. Might go to a cat scale, unload the tractor at the station, and weigh front and rear axles with loader and any implement off the ground. Then measure distance between front and rear axle. The line between center of axles is a line that represents a fulcrum. The weight of each axle becomes the weight on each end of the fulcrum. With that, you can use math to find the balance point, or Center of Gravity.

Don't know if that helps. I think the cat scales charge about $12. Use the app - it is easy to get results. Also go inside and ask for the printout.

Or you could just load the trailer the way you want, take loaded to the cat scale. That will tell you how much of the total trailer weight has been added to the truck weight. That weight and the trailer axle weight represents the Total trailer (and load) weight. You should have 10-15% of that total trailer weight added to the truck for proper loading and tracking.

 

[LD1]

Even if you knew the precise COG that still dont help you with loading it.

IF you knew it, would you put that COG 1' foward of the center of the axles? 2' foward? Right in the middle based on the other junk in the front of the trailer?

GO to a scale, its cheap if you are that worried.

But we are probably talking about a light trailer and certainly a light (~3000#) tractor. And being towed by a 1-ton that could probably handle the entire load weight in the bed.

So IMO, anywhere between pulling the tractor all the way forward, and the center of the tractor roughly center with the axles. Somewhere between there is gonna give a positive tongue weight somewhere between a few hundred pounds and maybe 1500 pounds. All of which should easily be handled.

For me....I just measure hitch height if Im bumper pulling. 8k mini-ex on a 2400# 12k trailer.....I like to see somewhere between 1" and 2" drop at my hitch from empty vs loaded. Which on my mini ex puts the center point of the machine about right at the front axle. Tows like a dream

 

[MTGreen]

I think some of these answers may be overcomplicating things. Most tractors are designed to be heavier in the back end than the front end for a number of reasons. Center of gravity is an engineering calculation that's not published by manufacturers. One could go to great lengths to figure it out but from a practical standpoint having an exact figure isn't necessary to loading a trailer.

Just back the tractor in to the trailer just past center over the axles with the butt end of the tractor facing forward in direction of the travel. You said you have an FEL so maybe bias it forward another 6-10 inches to compensate.
Then park the rig on a flat surface and look at what's sagging and what's mostly level. The front versus rear tandem wheels on the trailer and the rear of the truck. If something's grossly off then try repositioning.

Bumper pull trailers are supposed to have something like 10% of the trailer weight on the hitch. The biggest danger is putting too little weight on the hitch as that contributes the most to sway. If you put a little more than 10% on the hitch it's not that big of a deal unless your truck is sagging to the point that the steering starts to get floaty.

 

[super55]

I worked for years where I transported a Kubota L2500 w/FEL and loaded rears(about same size as 790) on a tandem axle trailer and it was the front wheels just slightly in front of the front duals. This was being done with 1/2 ton 2wd P/U w/o a towing packing and even a couple times back in the day with my little 4x4 s10 pickup.

 

[pretendfarmer]

Most tractors are designed to be heavier in the back end than the front end for a number of reasons.

Through a bit of research I found this to be true. There is a serious weight bias towards the rear for traction, which means I was really off in my guestimation of where the COG was.

Just back the tractor in to the trailer just past center over the axles with the butt end of the tractor facing forward in direction of the travel. You said you have an FEL so maybe bias it forward another 6-10 inches to compensate.

I cannot back the tractor into the trailer for a couple of reasons, most importantly that I have like 1/4" clearance at the door header with the ROPS crossbar removed and all the air out of the rear tires. Backing in will lead to contact.

Bumper pull trailers are supposed to have something like 10% of the trailer weight on the hitch. The biggest danger is putting too little weight on the hitch as that contributes the most to sway.

This I do understand which is why I am here in the 1st place. My enclosed trailer is "built out" a bit and so I am unable to pull the tractor in as far as I really would like to. I plan on changing this, but need to haul the tractor somewhere before I can.

 

[bcp]

Once upon a time, I saw some diagrams showing many tractors had their center of gravity very close to where the operator's feet rested. And they lived happily ever after.

Bruce

 

[MTGreen]

Through a bit of research I found this to be true. There is a serious weight bias towards the rear for traction, which means I was really off in my guestimation of where the COG was.

I cannot back the tractor into the trailer for a couple of reasons, most importantly that I have like 1/4" clearance at the door header with the ROPS crossbar removed and all the air out of the rear tires. Backing in will lead to contact.

This I do understand which is why I am here in the 1st place. My enclosed trailer is "built out" a bit and so I am unable to pull the tractor in as far as I really would like to. I plan on changing this, but need to haul the tractor somewhere before I can.

Are you able to put something heavy in front of the tractor when you pull it in to the trailer, maybe something you can put the fel on top of? I'm thinking something like a heavy box blade or equivalent size/weight object that you can lower the fel bucket on top of. That could help bias more weight forward

 

[pretendfarmer]

Are you able to put something heavy in front of the tractor when you pull it in to the trailer, maybe something you can put the fel on top of? I'm thinking something like a heavy box blade or equivalent size/weight object that you can lower the fel bucket on top of. That could help bias more weight forward

I have a bunch of tools, a work bench, supplies, etc. forward of the tractor.

I went into a deep dive on all of this and found some great information right on this site. The rule of thumb seems to be that the center of gravity of the tractor is right around the steering wheel area, not taking the FEL into consideration - which would skew it forward a bit. This means that the tractor COG as it currently sits in my trailer is centered over the rear axle, not between them. The loader probably balances it right over the axles. When you add the roughly 1,000-1,500 lbs of cargo ahead of the tractor, it would seem I'm probably looking pretty good.

I went ahead and measured how much sag I am getting in my suspension when I hook it up to the truck. I am dropping between 1.5"-1.75". I feel confident things are decently balanced. It just makes it hard when I have other stuff in addition to the tractor, and the tractor is back a few feet from where I'd normally want it.

 

[pretendfarmer]

Just thought I'd update the post. The trip went great. The tractor seemed to be in a good spot in the trailer and it handled very well.