Are floor jacks supposed to get harder to pump

[Ran58]

I have my Dad’s old Sears Green 1 1/2 ton floor jack. Not really familiar with how floor jacks are supposed to work. As you lift the handle and the jack starts picking up the weight is it supposed to get harder to pump the handle or is it supposed to be pretty effortless to pump the handle as it is before the jack contacts and lifts the weight?

thanks

 

[JKinAK]

Harder with increased weight is normal.

 

[cleveivy]

Yes, that's pretty normal. As you start lifting the weight, it’s gonna get harder to pump because the jack’s working harder to support the load.

 

[Wrench97]

The more weight on the jack the harder it is to pump.

 

[MovingAlong]

1 1/2 ton may be light for what you're lifting - so yeah, it probably does get harder to pump.

 

[Zewnten]

What are you lifting?

 

[finn]

Look at the geometry of the scissors / lift mechanism. The geometry changes as the ram extends and the saddle raises, so physics says the pumping effort will increase.

 

[charbar]

1 1/2 ton may be light for what you're lifting - so yeah, it probably does get harder to pump.

This also^^^

If you're trying to lift the front of your F350 with a PowerStroke and a RanchHand bumper hanging off the front you are going to have a hell of a time with a 1.5 ton jack.....

 

[kbuhagiar]

I have my Dad’s old Sears Green 1 1/2 ton floor jack.

That is a GREAT vintage jack, made in Japan. Weighs a frickin' ton but is SOLID.
Just sold my brother's, he bought it new and had it for over 45 years. Still worked like the day he bought it.

 

[mike93lx]

How nice would it be if you could do work without effort you'd have unlocked something amazing

 

[Ran58]

How nice would it be if you could do work without effort you'd have unlocked something amazing

Well I didn’t know. Wasn’t sure if hydraulics would make it lift without too much effort. I was using it to lift the back end of my K1500 Silverado and I had to exert a pretty good amount of force to lift it. Didn’t know if that meant that I was overtaxing the jack or if there was something wrong with it.

 

[johnre]

There are three ratios that affect the effort required for a floor jack:

1. Hydraulic ratio - essentially ratio of the relative areas of the primary (pump) and secondary (lift) pistons
2. Pump mechanical ratio - essentially the lever advantage on the primary (pump) side
3. Lift apparatus mechanical ratio - essentially the lever advantage of the jack's mechanicals, i.e. how much vehicle lift is produced per unit change in the length of the secondary piston

As @finn noted, #3 on the list can change as the jack is lifting. As a thought experiment, a bottle jack has a unity mechanical ratio; i.e. 1" secondary piston movement produces 1" of lift.

As you lift the handle and the jack starts picking up the weight ....

Don't you mean "as you push down on the handle"? No floor jack I know of produces lift as you pull up on the handle.

 

[bwringer]

... I was using it to lift the back end of my K1500 Silverado and I had to exert a pretty good amount of force to lift it. Didn’t know if that meant that I was overtaxing the jack or if there was something wrong with it.

You definitely need a higher capacity jack than 1.5 ton for working on pickups.

You are likely very, very close to the capacity of the jack with that amount of weight. You'd probably find this jack would not lift the front of the truck.

Hydraulic jacks have safety valves (AKA "bypass" or "overload" valves) that will release pressure if you try to lift something that's too heavy. The structure and hydraulics are only designed for a certain amount of weight.

Please don't take chances like this. Head to Harbor Freight and get a 3 or 4 ton floor jack for working on pickups, and use Dad's old jack for working on cars.

Here's a pretty good comparison of 3 ton jacks, and you can see how the bypass valves work.

 

[Wrench97]

1.5ton(3000lbs) is fine for jacking it up one corner at a time as always use a jack stand.

 

[mm08822]

1.5ton(3000lbs) is fine for jacking it up one corner at a time as always use a jack stand.

And I've lifted the rear end of my f250 crewcab from the pumpkin with the same jack to place a pair of jack stands.

If it was too heavy, the bypass would open and lift no higher.