0

Recently, I bought a 2 Ton Big Red scissor jack. My car weighs around 1.2 ton and each front corner of the car is no heavier than 650 - 700 kg. However, it requires so much effort to turn the jack handle and it really struggles to lift the tires off the ground so that you can change or rotate them. I had read many positive reviews about Big Red jacks and paid almost a fortune for this product but now I'm indeed disappointed with my purchase. (Even my cheap Chinese jack was better than this). I tried applying grease to its threads to make it perform better but that didn't make a difference either. Why is it rated at 2 ton capacity if it can't lift as low as 650 - 700 kg?

Here are some pictures of the jack as requested:

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

Improve this question
15
  • 1
    I'm not clear by what you mean by "it struggles". Is the jack deforming or bending or do you mean it's just difficult for YOU to turn the crank. In other words, YOU struggle to use the jack??
    – jwh20
    Commented Apr 6, 2023 at 10:25
  • @jwh20 - Yes, it can be expressed in both ways. It is so hard for me to turn its handle to lift the car but it is not my fault because I could lift the same car with other jacks. That's why I say, the jack struggles not me! The jack doesn't seem to bend or deform while operating and I even checked it to raise as straight as possible.
    – LFY MP7.3
    Commented Apr 6, 2023 at 10:29
  • Can you add a link to the exact jack you have purchased?
    – HandyHowie
    Commented Apr 6, 2023 at 10:33
  • 1
    I'm not finding any "Big Red" 2 ton scissor jacks. I only find a 1.5 ton model. I also don't see any Big Red jacks at all that you might have "paid almost a fortune for". The 1.5 ton model is advertised for around $27.00 at many places including Amazon. I'd put this squarely into the category of "cheap Chinese" jacks.
    – jwh20
    Commented Apr 6, 2023 at 10:37
  • @handyHowie - My jack is very much like this one but it is rated at 2 ton: amazon.com/Torin-Steel-Scissor-Jack-Capacity/dp/B004PX8BC2?th=1
    – LFY MP7.3
    Commented Apr 6, 2023 at 10:45

1 Answer 1

Reset to default
3

The scissor jack needs the maximum input force at its lowest position, similar to the principle of levers. If you consider an "ideal structure" with components of zero thickness, the scissor jack at its bottom position will need an infinite force applied horizontally to make it begin to rise vertically.

An analysis of the force is shown in Scissor Lifting Elevator Mechanism, which summarises:

The maximum force needed when the angle theta [between the struts] is minimum.

This is distinct from the pitch of the screw used to raise it, the force from which is independent of the height raised.

Frankly, the scissor jack isn't a very good design. There are other designs that need a constant force regardless of the height raised. In the days when I carried a tool box in my car, it would include a simple hydraulic jack.

Improve this answer
14
  • 3
    @NarimanAsgharian - Maintenance on a bottle jack? I have bottle jacks that are over 20 years old and have done zero maintenance (other than keeping them upright as Weather Vane suggested) on them and they still work as designed and without issue. As long as the fluid doesn't leak out, there's really very little to them.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Apr 7, 2023 at 8:34
  • 2
    @NarimanAsgharian - If the wild hair existed to change the fluid in a bottle jack, you just have to remove a small rubber plug, drain it out, then refill it. Very easy, and just the cost of the hydraulic fluid, which isn't expensive. Raise height of the jack is dependent upon the jack itself, though most have a threaded rod which can be used to take up the initial distance between jack and lifting point. I use a piece of 2x4 between jack and vehicle no matter what type of jack I'm using. It spreads the load over a large area to prevent damage.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Apr 7, 2023 at 10:15
  • 2
    Yeah, I've never replaced fluid in any jack, and I've had most of mine for over 30 years. They still work. If your scissor jack isn't being damaged it may just be hard to turn. Make sure you lubricate the thrust bearings with something preferably non-sticky like graphite paint.
    – Harper - Reinstate Monica
    Commented Apr 8, 2023 at 5:14
  • 1
    I think a rubber pad is necessary to prevent damage. I carried bits of wood, and I always use some protection regardless of the type of jack. Even a scissor jack with a lip that locates under the bottom seam, I will at least use a cloth to protect against scraping the paint.
    – Weather Vane
    Commented Apr 8, 2023 at 9:48
  • 1
    There is unlikely to be a catastrophic failure just due to old oil. In any case you should never go underneath a jacked vehicle without using rigid axle stands.
    – Weather Vane
    Commented Apr 10, 2023 at 12:33

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .