sounds silly, but...hard to raise M3 using scissor jack?

[Daniel in SD]

I'm unclear how suspension plays into this but you are certainly right that until the tyres come off the ground some of the car's weight rests on them.

If there was no suspension then the you'd be lifting the entire weight of the car right away. The softer the suspension the less force it takes when you first start lifting the car. Imagine trying to lift a 4000lb block of steel, no way it would even budge. However if you try to lift a car you can lift it an inch or two.

 

[angLe]

The reason it's easier to turn as the jack gets higher is that the mechanical advantage is increasing as the angle between the links approaches 180°.

 

[SageBrush]

If there was no suspension then the you'd be lifting the entire weight of the car right away. The softer the suspension the less force it takes when you first start lifting the car. Imagine trying to lift a 4000lb block of steel, no way it would even budge. However if you try to lift a car you can lift it an inch or two.

• One corner only
• I'm not sure about the leverage but an 8 inch handle on a scissor jack would travel about 25 inches in a rotation and ?? perhaps raise the car an inch

 

[Daniel in SD]

• One corner only
• I'm not sure about the leverage but an 8 inch handle on a scissor jack would travel about 25 inches in a rotation and ?? perhaps raise the car an inch

Try to lift the car by the wheel . When you lift from the frame the suspension helps for the first few inches which mitigates the lower mechanical advantage of the scissor jack.

 

[ceekz]

I've got a VW/Audi one with a custom adapter and it does feel a bit sketchy when I lift the car.
Like this: 99-05 VW GOLF PASSAT AUDI A3 A4 A6 JACK WRENCH POUCH 8L0011031A | eBay
Looks like someone is selling pad adapters: Tesla Model 3 jack pad adapter for Audi/VW jack | eBay

Ah! I just figured out why I sold 2 on eBay in the last 2 days! Thanks for the plug, all the $ from the sales supports my daughter's robotics team.

 

[ceekz]

How do you use a jackpad adapter with a scissor jack?

 

[Daniel in SD]

Ah! I just figured out why I sold 2 on eBay in the last 2 days! Thanks for the plug, all the $ from the sales supports my daughter's robotics team.

Yeah my buddy wanted two and I saw your listing when I searched for VW/Audi jack. I told him to just buy them from you I made mine by hacking up a Streetrays one with a band saw. Yours is much prettier.

 

[Glamisduner]

View attachment 366167

I have never seen one like that Looks great!

 

[ceekz]

I have never seen one like that Looks great!

All the design credit goes to @siminoff, who shared his specs with my daughter's high school robotics team. They are raising funds to travel to competitions by manufacturing these adapters!

 

[mswlogo]

Huh. I'll have to pull mine out tomorrow. I keep seeing the opposite in my head

Addendum:
The jack forms a right triangle, and the hypotenuse does not change.
As we rotate the arm and the jack rises the x value shortens and the y value increases but the relation
x^2 + y^2 = R^2 stays constant. The x shortening per rotation is constant.

Say we start at x = 6 and y = 1, then R = sqrt(37)
If we shorten x by 1 then x = 5 and y = sqrt (37 - 25) = sqrt (12)
If we shorten x another 1 then x = 4 and y = sqrt (37 - 16) = sqrt (21)
And another 1 for good measure: now x = 3 and y = sqrt (37 -9) = sqrt (28)

The vertical gain per decreases increases as the angle opens.

You were close on your math but you just lost scope of the problem.
You need to look at the delta Y for each unit change in X.
You‘re calculating the total Y on each iteration.

Addendum 2:
Let’s do the last 2 steps (jack fully up)

X = 1 and y = SQRT (37 - 1) = 6
X = 0 and y = SQRT (37 - 0) = 6.08 (delta Y is a tiny 0.08 for delta X of 1)

Let’s go back to your first step

Y = 1 (starting Y, jack fully down)
Y = SQRT (12) = 3.46 (delta Y is a huge 2.24 for delta X of 1)

 

[xanatos]

It's amazing how my question has resulted in a refresh of junior high trigonometry!

 

[mswlogo]

It's amazing how my question has resulted in a refresh of junior high trigonometry!

No Trigonometry has been discussed here It’s Pythagorean Theorem.

 

[Daniel in SD]

No Trigonometry has been discussed here It’s Pythagorean Theorem.

Had to check but you’re right. I thought the Pythagorean theorem was part of trigonometry but apparently it’s Euclidean geometry.

 

[SageBrush]

You were close on your math but you just lost scope of the problem.
You need to look at the delta Y for each unit change in X.

I think we agree the delta Y decreases per rotation as the jack rises so the work done per rotation also decreases. Since the rotation distance remains constant the torque required to rotate the handle drops as the jack rises.

 

[N54TT]

I have a 3 ton scissor jack, works great

Which scissor jack do you have? Looking for one to keep in the car along with my plug kit.

 

[joonrhee]

Which scissor jack do you have? Looking for one to keep in the car along with my plug kit.

I'm curious as well. I'm looking for a scissor jack to keep in the car along with tire repair kit. Also, would like to know if I buy the scissor jack, I wouldn't need a separate wrench to unscrew the wheels? I was initially thinking about going for a full spare kit from modernspare.com but what are the actual chances of using the spare? I never had to use it in past 20+ years..

So, I just need some advice on which torque wrench to unscrew the wheels off and a strong scissor jack. Thanks in advance!

 

[mswlogo]

I'm curious as well. I'm looking for a scissor jack to keep in the car along with tire repair kit. Also, would like to know if I buy the scissor jack, I wouldn't need a separate wrench to unscrew the wheels? I was initially thinking about going for a full spare kit from modernspare.com but what are the actual chances of using the spare? I never had to use it in past 20+ years..

So, I just need some advice on which torque wrench to unscrew the wheels off and a strong scissor jack. Thanks in advance!

First post describes the jack I use, scroll down a few posts and links for wrench, socket etc.

The perfect Model 3 emergency jack?