center of gravity

[uninformed]

hey all,

does anyone know the height of center of gravity for a def 110 tray back?

cheers,
Serg

[Slunnie]

You're plotting something evil again!

I don't have the answer, but I though that a rule of thumb was the top of the gearbox or some height through the engine.

[uninformed]

Yeah the general rule of thumb is top bolt on bellhousing, but when i talked to a mate about it his gut feeling was it was lower,enough to make a difference in calcs. Now when this guy says something, i listern. we were ment to tip my truck over with his 7t tractor last time i was out his way, but ran out of time.............next time i guess.

Serg

[Slunnie]

No thats cool, I'd bet your mate is right too.

I guess the rear of a ute and the CofG would be somewhere between the top of the diff and the chassis depending on the tray construction. You'll probably only ever really know with your truck by pulling it with the tractor.

[uninformed]

he figured just above the rear ball joint, i thought that was a bit low but he knows wayyyyyyyyyyyyyyyyy more than me ;).

[windsock]

Yeah the general rule of thumb is top bolt on bellhousing, but when i talked to a mate about it his gut feeling was it was lower,enough to make a difference in calcs. Now when this guy says something, i listern. we were ment to tip my truck over with his 7t tractor last time i was out his way, but ran out of time.............next time i guess.

Serg

Hiya,

How to you get to know what the COG is by using a tractor? I am assuming you lift it up from one side to 'tipping' point but I cannot figure out how from this you calculate or otherwsie estimate where the centre of gravity is...

Figure it'd be useful to know before I try it at home... ;)

Cheers,

Phil

[uninformed]

get some masking tape and tape a center line down the middle (center of wheel track) of the grill. Lift side of truck untill you fid the tipping point, remember to put some safety straps to stop it going completely over, or just make sure you lift the good side with dinged side down :D

whilst in postion, take a plumb bob from contact patch of front tyre on the ground. where it interescts the center line will be the height of COG when back on all fours.

level ground is improtant. also lock out the steering ..... DO ANY OF THIS AT YOUR OWN RISK

[windsock]

Good stuff, as soon as I read where you put tape on the grill it all made perfect sense so is all good. I also have a 110 with trayback and would be interested in assessing where COG is - empty and loaded with camping stuff on the back. Near neighbour has a large excavator and so we may use this to lift it one day when he is less busy, otherwise it'll be a chain-block from the gum tree :eek:

Cheers,

Phil

[uninformed]

gum trees are structuraly reliably UNRELIABLE regardless of branch/trunk dia.

[Grover-98]

I have all the vehicles and a tractor... but dont have the guts to do it... Might do it to one of the Haflingers see how low that is. As for the others tell me when someone gets the guts to try it on a.

1. 2" lifted D1 with 31's
2. Standard SWB 2A with 2.25 Diesel
3. Classic Range Rover

:angel:

James.

[windsock]

gum trees are structuraly reliably UNRELIABLE regardless of branch/trunk dia.

hmmm, I am wondering if they differ between Aust and NZ. I have access to several old-man gums (exact type unknown) growing beside a stream and the only problem we have had is wind stripping small branches off them. They are not the 'widow-makers' I have seen in drier climates.

Agreed however on directly lifting a dead-weight on anything organic. I was thinking of wrapping a strap around and over the main trunk and over a branch on the opposite side from the truck and pulling up and towards the bank that the tree grows on. I figured if I park up in the right place I then can 'teeter' the truck at tipping point and have the bank to stop me going right over on my side.

Excavator would be by far the best option as far more controlable. A matter of persuading a somewhat conservative operator of the necessity :angel:

Certainly a task for when I have put stronger roll protection on and when no-one else is looking...

[Bush65]

The CoG can be calculated if you have suitable scales to measure the weight at each wheel when the vehicle is level, then when one end is elevated. The other required measurements are wheel base and height that the end was elevated.

Bathroom scales can measure the wheel loads by using a lever.

IMHO much less risk than tipping the vehicle over.

There is a good write up on one of the Jeep sites (jeepaholics from memory).

[Grover-98]

The CoG can be calculated if you have suitable scales to measure the weight at each wheel when the vehicle is level, then when one end is elevated. The other required measurements are wheel base and height that the end was elevated.

Bathroom scales can measure the wheel loads by using a lever.

IMHO much less risk than tipping the vehicle over.

There is a good write up on one of the Jeep sites (jeepaholics from memory).

Funny you should mention that, i was looking at that exact site last night! seemed far more practical.

[Grover-98]

Center of Gravity and Roll-Over Angle - Jeepaholics Anonymous (http://www.jeepaholics.com/tech/cog/) have a read fellas. :)

[uninformed]

Center of Gravity and Roll-Over Angle - Jeepaholics Anonymous (http://www.jeepaholics.com/tech/cog/)

yes its a good way of doing it, but in the past i have had difficulties getting a simple front and rear axle weight of my truck, let alone coming up with a way to raise the front of the vehicle 600mm off the ground, by supporting the tyres, with the rear on the scales........with all the legal stuff and time is money etc, i cant imagine to many scale places being up for it. If any one knows of one on the Gold Coast ill be happy to go do it, though im still trying to figure out how to get the front end up

Serg

[Grover-98]

Center of Gravity and Roll-Over Angle - Jeepaholics Anonymous (http://www.jeepaholics.com/tech/cog/)

yes its a good way of doing it, but in the past i have had difficulties getting a simple front and rear axle weight of my truck, let alone coming up with a way to raise the front of the vehicle 600mm off the ground, by supporting the tyres, with the rear on the scales........with all the legal stuff and time is money etc, i cant imagine to many scale places being up for it. If any one knows of one on the Gold Coast ill be happy to go do it, though im still trying to figure out how to get the front end up

Serg

You could just use ordinary car ramps. And adjust the calculations to suit. You will find the COG regardless of if you raise it 600mm or 200mm.

James.

[uninformed]

You could just use ordinary car ramps. And adjust the calculations to suit. You will find the COG regardless of if you raise it 600mm or 200mm.

James.

it clearly states that you must raise the vehicle at least 24 inches off the ground. Im going to go ahead and assume that the guy that put this together has done his research and knows why.

Serg

[Zute]

Finding the roll centre might be more practical.

[windsock]

Center of Gravity and Roll-Over Angle - Jeepaholics Anonymous (http://www.jeepaholics.com/tech/cog/) have a read fellas. :)

Now theres some good info right there for sure, thanks to Bush65 and Grover-98. I had access to the local landfill scales but may need to see who the new operator is before getting carried away with ramps etc. Discrete data and analysis followed by validation in the field... :cool:

Sounds like a nice little research project :D;)

[windsock]

Finding the roll centre might be more practical.

If the web site info is calculated accurately, roll centre is a given as once COG is obtained, as aren't they one and the same? Assuming my understanding of rolling is correct :angel: Roll angle may be another equally applicable and understandable phrase.

[Slunnie]

Roll centres are based on suspension geometry and are different between the front and rear - it's different to the CofG.

[uninformed]

Roll Center Height:

REAR Any rover running a A frame rear end, roll center height is the center of the ball in the ball joint.

FRONT Any rover running radius arms with panhard rod the roll center height is the height of the panhard rod (middle of the rod itself) at the intersection of the center of track width.

Vehicle Roll Axis angle: If a line is drawn from the front roll center height to the rear roll center height, this represents the vehicle roll axis angle.

These can be obtained with a simple tape measure.

What I do need for my Calculations is the COG.

Regarding the method discribed in the attached link, the reason they require the lift of 24 inches or greater on the front end, is to get enough of a differential in wheigts etc to create a more accurate outcome.

Serg