Angle of lean, before it topples? - Page 2

T-Cut · 11th June 2015, 23:28

If you can guesstimate how high the centre of gravity is, you can determine how high you can lift it. I guess the height of the CG will be somewhere around the top of the engine, perhaps somewhat lower. Using a scale diagram of the car's front profile, you can get a pretty good idea of the angle needed to put the CG outside the wheelbase. I assume it's all theoretical anyway.There may be data on the CG height somewhere on t'Net.

TC

bubs · 12th June 2015, 06:38

I would be more worried about the weight of the car pushing down on the edge of the other tyres more than the car going over.

David Lawrence · 12th June 2015, 07:05

How do you keep the car stable on this lift?

Are there supplementary supports to stop it toppling down if something shifts the balance point. Imagine the italian job bus, you take off a brake disk or something and the end of the car lifts up in to space.

HarryM1BYT · 12th June 2015, 08:20

Quote:

Originally Posted by David Lawrence

How do you keep the car stable on this lift?

Are there supplementary supports to stop it toppling down if something shifts the balance point. Imagine the italian job bus, you take off a brake disk or something and the end of the car lifts up in to space.

Nothing to stop you dropping it onto stands, but with the rear end lifted or one side, it is very stable. It would need a very major removal of weight to shift the balance point, such as the engine removal.

Its not so finely balanced that taking wheels or other small parts, could have it move a noticeable distance. It feels very stable, even at maximum. My only concern is that of lifting a front wheel so high, that it over balances to roll over sideways.

It feels a lot more stable and safer on this, than it ever did on axle stands. The base is many times bigger, than that of a stand and likewise the contact point with the car.

Its here if anyone wants to try it, see what it can do and just how stable it feels.

As said, they have/ had just one left at this price and it really is a great bargain. Machinemart are offering virtually the same model, at £2000 and its by far the cheapest/best on ebay and the only self powered one I could find on there.

Supervinnie40 · 12th June 2015, 09:06

Quote:

Originally Posted by T-Cut

If you can guesstimate how high the centre of gravity is, you can determine how high you can lift it. I guess the height of the CG will be somewhere around the top of the engine, perhaps somewhat lower. Using a scale diagram of the car's front profile, you can get a pretty good idea of the angle needed to put the CG outside the wheelbase. I assume it's all theoretical anyway.There may be data on the CG height somewhere on t'Net.

TC

Agree, but you would have to take in account that the fluids try to remain level. So they "lean" towards the side that is not being lifted up. Shifting the centre of gravity towards the side that is down. Also, while the wheel will stay at 1 place, the top of the car will soon hang over the point where the wheel touches the ground.
But the general theory is correct I think. As soon as the centre of gravity goes over the centre of support area, it'll topple over. A meter should be easily done.
Seeing as the car is about 1.50 or 1.60 meters wide, (and you believe that the centre of gravity is roughly around the centre) you would eventually draw a triangle.
As soon as the bottom of the triangle reaches 0, it will have reach its maximum (going any further will push the CG over the point of contact with the ground).
Knowing that the sloped side of the triangle will stay the same length (that distance doesn't change) we can start to calculate.

The centre of width is roughly the centre of the width= 80 cm.
The height of the CG is unknown, but I estimate around 50 cm high.
The corner underneath the CG is 90 degrees when the car is flat.

So we get:
a= bottom: 80.00
b= sloped side: 94.34
c= height: 50.00

b won't change, but a will. So we just need to change a to 0 and make sure that the bottom corner stays at 90 degrees.
c can never be higher then b, because then it wouldn't be the same triangle anymore. So the max for c is equal to b.

So I would estimate that IF the CG is at roughly 50cm height, the maximum height to lift the car on one side would be 94.34 cm.
If the CG would sit at 60 cm, that would make it 100cm.
If the CG would sit at 70 cm, that would make it 106.30cm.

Just a quick thought. There might be more to it...

HarryM1BYT · 12th June 2015, 09:15

Quote:

Originally Posted by Supervinnie40

Just a quick thought. There might be more to it...

What immediately springs to mind, is that as it lifts under the tyre and suspension - the suspension will expand on the higher side as the weight comes off, on the low side it will be compressed. So the actual angle of lean will be quite a lot more, than calculated.

kaiser · 12th June 2015, 09:43

If you know the centre of gravity, then it is easy, as the load will tip when the centre of gravity overshoots the outer support.

I guess it will lean more than you think.

But I would not work on it at that angle.

pinebob · 12th June 2015, 09:53

Quote:

Originally Posted by HarryM1BYT

What immediately springs to mind, is that as it lifts under the tyre and suspension - the suspension will expand on the higher side as the weight comes off, on the low side it will be compressed. So the actual angle of lean will be quite a lot more, than calculated.

at that price harry just buy two and lift both sides together.problem solved haha,

HarryM1BYT · 12th June 2015, 12:43

Quote:

Originally Posted by kaiser

If you know the centre of gravity, then it is easy, as the load will tip when the centre of gravity overshoots the outer support.

I guess it will lean more than you think.

But I would not work on it at that angle.

I wasn't thinking of doing so, but it would be good to be able to put a line on the lift, beyond which it becomes unsafe.

What I will be doing, is lifting one side, dropping it onto bits of rail sleepers, then lifting the other side.

RodgerD · 12th June 2015, 12:43

I certainly wouldn't lift one wheel up one metre. The stresses placed on the chassis and the loadings on the opposite wheels/suspension could lead to failure at a later date.

What effect it will have on an alloy wheel bearing the weight of a car on an angle is anyone's guess.

I'd either lift the entire front or rear so weight of car remain fully across the tyre section on the other two wheels that remain on the ground.

We used to use that type of vehicle lift for bendy-buses (six off) and was thinking of manufacturing a car set (four off) myself, either using the rams from engine hoists which are rated at 8 tons, which will give approximately 18" of lift, or using a cable/pulley system with electric motors and ratchet rack safety locking on upward travel. Rams are easier, but you have to run round manually pumping them and limited on travel, whereas electric can be any height and all controlled from one spot. Replacement hoist rams are £37

12th June 2015, 12:43	#20
RodgerD Rodger & Out Rover 75 Saloon Join Date: Nov 2014 Location: London Posts: 712 Thanks: 10 Thanked 159 Times in 141 Posts	I certainly wouldn't lift one wheel up one metre. The stresses placed on the chassis and the loadings on the opposite wheels/suspension could lead to failure at a later date. What effect it will have on an alloy wheel bearing the weight of a car on an angle is anyone's guess. I'd either lift the entire front or rear so weight of car remain fully across the tyre section on the other two wheels that remain on the ground. We used to use that type of vehicle lift for bendy-buses (six off) and was thinking of manufacturing a car set (four off) myself, either using the rams from engine hoists which are rated at 8 tons, which will give approximately 18" of lift, or using a cable/pulley system with electric motors and ratchet rack safety locking on upward travel. Rams are easier, but you have to run round manually pumping them and limited on travel, whereas electric can be any height and all controlled from one spot. Replacement hoist rams are £37 Last edited by RodgerD; 12th June 2015 at 12:49..

11th June 2015, 23:28	#11
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,754 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	If you can guesstimate how high the centre of gravity is, you can determine how high you can lift it. I guess the height of the CG will be somewhere around the top of the engine, perhaps somewhat lower. Using a scale diagram of the car's front profile, you can get a pretty good idea of the angle needed to put the CG outside the wheelbase. I assume it's all theoretical anyway.There may be data on the CG height somewhere on t'Net. TC

12th June 2015, 06:38	#12
bubs Posted a thing or two ROVER 75 Join Date: Oct 2012 Location: Canvey Island, Essex Posts: 1,651 Thanks: 43 Thanked 163 Times in 134 Posts	I would be more worried about the weight of the car pushing down on the edge of the other tyres more than the car going over.

12th June 2015, 07:05	#13
David Lawrence This is my second home Rover 75 CDT-2001 Join Date: Jan 2009 Location: Wrexham, North Wales Posts: 3,606 Thanks: 195 Thanked 606 Times in 501 Posts	How do you keep the car stable on this lift? Are there supplementary supports to stop it toppling down if something shifts the balance point. Imagine the italian job bus, you take off a brake disk or something and the end of the car lifts up in to space.

12th June 2015, 09:43	#17
kaiser This is my second home 75 Tourer 2.5 Auto, 1.8T, 75V8ZT Join Date: Jun 2007 Location: Johannesburg ZA Posts: 6,200 Thanks: 1 Thanked 859 Times in 613 Posts	If you know the centre of gravity, then it is easy, as the load will tip when the centre of gravity overshoots the outer support. I guess it will lean more than you think. But I would not work on it at that angle.