Torque for Mechanical "scissor" jack
Torque for Mechanical "scissor" jack
(OP)
Hello All:
I'm looking for typical torque values for lifting a load with the average mechanical "scissor" jack, most commonly found in the trunk of a car (center horizontal drive screw and hinged joints). I'd like to fit an electric gearmotor to this jack in direct drive, but I need to estimate the required torque to lift my load. Has anyone come across some curves plotting torque vs. load for various jack types? Any equations for this type of estimation? Thanks in advance.
I'm looking for typical torque values for lifting a load with the average mechanical "scissor" jack, most commonly found in the trunk of a car (center horizontal drive screw and hinged joints). I'd like to fit an electric gearmotor to this jack in direct drive, but I need to estimate the required torque to lift my load. Has anyone come across some curves plotting torque vs. load for various jack types? Any equations for this type of estimation? Thanks in advance.
ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee





RE: Torque for Mechanical "scissor" jack
RE: Torque for Mechanical "scissor" jack
ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee
RE: Torque for Mechanical "scissor" jack
Cheers
Greg Locock
RE: Torque for Mechanical "scissor" jack
RE: Torque for Mechanical "scissor" jack
Test it. The friction coefficients can vary all over the place. I have a jack that is loosem the gets tight and then loosens again as it raises. They are cheaply made and fits and tolerances vary all over ther place. Not to mention the cleanliness of the threads
Regards
Dave
RE: Torque for Mechanical "scissor" jack
z=height
T= torque
Theta=? (pitch of the threads? angle of the brackets?) Forgive me if these questions are too basic. I'm more of a chemical guy.
ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee
RE: Torque for Mechanical "scissor" jack
Cheers
Greg Locock
RE: Torque for Mechanical "scissor" jack
1. They are designed for little old ladies to pick up the corner of a car. Typical handle 6" long, typical old lady will pull 20lbs. Torque = 40 ft lbs to lift 500 lbs
2. They make caravan (trailer) jack operators from battery screwdrivers plus a bit of hex bar and a socket spanner
Good Luck
johnwm
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RE: Torque for Mechanical "scissor" jack
Be careful motorizing one of these things. They are lubricated with a heavy grease, but they aren't really made to be used a bunch of times. Maybe 10 times in the car's life? Anyway, if you start running that jack up and down with a motor, I think that grease is going to disappear pretty quick.
I think if you'll look at the geometry, torque is highest for a given lift when the jack is all the way down. But lifting cars, even if you start with the jack all the way down, you have to raise it a ways before you get the full weight on the jack. So you practically never operate one of these jacks in the maximum-torque condition.
RE: Torque for Mechanical "scissor" jack
Cheers
Greg Locock
RE: Torque for Mechanical "scissor" jack
ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee
RE: Torque for Mechanical "scissor" jack
Cheers
Greg Locock
RE: Torque for Mechanical "scissor" jack
life requirements, WITHOUT redesigning the mechanism. Your requirement is very minimal.
Before you buy, however check out the hinge area and the thread detail for good design as Greg implies.
By the way, given all the cars that are junked, I would think that there must be plenty around in junk yards that would easily work Most have rarely or never been used.
RE: Torque for Mechanical "scissor" jack
Also, I am going on to get my Masters, possibly at Penn State, along with, possibly a Ph.D. Any advice on the value of Ph.D. and what it can be used for? Is it only valuable for academia or can it be equally useful in industry?
Thanks, I appreciate any feedback.
RE: Torque for Mechanical "scissor" jack
As to the PhD, Check out the number of job adverts specifing a Masters. Divide by the number of MSc engineers graduating each year. Ditto with PhDs.
If you have a burning desire to investigate something to the nth degree then go for it, just don't expect too many other people in the real world to share your enthusiasm.
Cheers
Greg Locock
RE: Torque for Mechanical "scissor" jack
any info on calculating air fuel ratio for four stroke, otto cycle, internal combustion, single cylinder, honda g200 engine?
Thanks,
Dan
RE: Torque for Mechanical "scissor" jack
1. Whats the fuel
2. How's the fuel put in.
3. Hows the air put in.
Basically work out your stoichiometric fuel/air requirement,
then add some air. Job done.
Cheers
Fredbert