Scissor Car Jack Purpose of Teeth

  • Thread starter Altairs
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    Car Teeth
In summary, the purpose of the teeth in a scissor jack is to prevent lateral motion and ensure that the jack rises or descends evenly, keeping the bracket plate parallel to the ground surface. Without the teeth, the jack could potentially rotate and cause instability.
  • #1
Altairs
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What is the purpose of teeth in such jack ? Isn't the screw enough to provide the lift ? What will happen if these gear like teeth are not present in a scissor jack ?
 
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  • #2
I'm not sure what you mean by 'teeth', since I've never seen such a thing. My best guess without a visual aid is that it might be some kind of safety catch in case of the worm drive system stripping out.
Can you post a picture?
 
  • #3
Check the attachment...Number 19 is what I was referring to...

Moderator Note: In future, please resize your images to a maximum of 800 x 600 pixels.
 

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  • #4
Those teeth allow struts 12&14 and struts 13&15 to move past one another while remainng in in contact in such a way as to structurally support each other.
 
  • #5
And if these aren't there then what change will come to these struts while e.g. ascending and descending the car?
 
  • #6
Look at the construction at the bottom of the jack. There are actually to adjacent pivots, not a single pivot.

Now imagine for a moment that the gear teeth are not there. The base plate, the two lower arms, and the screw are all connected by pin joints, so they act like a four bar linkage and can move laterally. This would be highly undesirable for the jack! The purpose for the gear teeth is to remove this degree of freedom and prevent the lateral motion of the jack.
 
  • #7
Altairs: The scissor jack teeth (item 19) constrain both sides of the jack to rise or descend exactly the same amount, thus forcing bracket plate 16 to remain parallel to base plate 11 (and therefore parallel to the ground surface). If the teeth were not present, bracket plate 16 could rotate in response to grossly eccentric loading applied to plate 16. And, if bracket plate 16 (and base plate 11) were free to rotate, then the entire jack could translate/rotate laterally about base plate 11, as pointed out by Dr.D.
 

What is a scissor car jack?

A scissor car jack is a tool used to lift cars, trucks, and other vehicles off the ground in order to change a tire or perform maintenance.

What is the purpose of the teeth on a scissor car jack?

The teeth on a scissor car jack are used to grip and hold the vehicle in place while it is being lifted. They also help to distribute the weight of the vehicle evenly across the jack.

How does a scissor car jack work?

A scissor car jack works by using a mechanical lever system to lift the vehicle off the ground. The jack is placed under the vehicle and the lever is turned, which causes the scissor arms to expand and lift the vehicle up.

Are scissor car jacks safe to use?

When used correctly, scissor car jacks are generally safe to use. However, it is important to follow the manufacturer's instructions and to use caution when working under a lifted vehicle.

Can a scissor car jack be used for all types of vehicles?

No, scissor car jacks are designed for use with smaller vehicles such as cars, SUVs, and light trucks. They are not suitable for larger vehicles like heavy-duty trucks or buses.

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