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Jack Stands ...In Honor & Memory of Ethan Allen (yourfriendethan) by Fiero Vice
Started on: 08-01-2021 01:48 AM
Replies: 47 (1124 views)
Last post by: Patrick on 09-06-2021 07:57 PM
Fiero Vice
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Report this Post08-10-2021 11:10 PM Click Here to See the Profile for Fiero ViceSend a Private Message to Fiero ViceEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:
When all sizes are kept the same, the triangle jack stands will have 3 significantly less stable directions. Murphy's Law would imply those would be the only direction you would need to use them in.


FieroGuru, I noticed Europeans often go with triangle stands, which have been available for a long time.

Here's what I found from my research.

A square is capable of becoming a parallelogram. A triangle is only capable of being a triangle.



The struts of a square (or rectangle) are able to pivot around its vertices. Imagine a square held together with hinges. If you stood it upright and pushed against the top, it would lean to the side and eventually flatten like a pancake. The angles change but the length of the struts do not. The structure fails without any breakage having to take place.

Try the same with a triangle and nothing will happen. It is unable to pivot because the struts would have to lengthen to compensate for the change in angle. Its shape is rigid. Thus, a triangle will not fail unless the struts or connectors break.

Triangles have an interesting property.

Any triangle is completely determined by its side lengths (up to position, rotation and reflection).

This means if I tell you the side lengths of a triangle, you can find the angles (this is given by the cosine rule). Essentially this means the angle between any two sides is fixed, the triangle cannot deform without changing the side lengths.

Other shapes do not have this property. A square can be deformed into a rhombus with the same side lengths, without changing the side length.

This means a square will inherently have structural weaknesses at the corners, while triangles don’t.
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fieroguru
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Report this Post08-11-2021 06:53 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
You are focused on the strength of the triangle structure vs square (I am not disputing that the triangle shape is strong), I am concerned with stability when the triangle is positioned on its back and used as free standing base.
You are assuming failure of the jack stand is due to leg deflection, I am saying jack stands can tip over (fail) w/o the legs ever being deflected.

This diagram below should clearly demonstrate my concern... this doesn't change based on which country, state, city, garage, or driveway it is used in.

The value of "X" in the triangle is 0.5774 of the "X" value for square or 42.26% less.

[This message has been edited by fieroguru (edited 08-11-2021).]

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Report this Post08-11-2021 11:56 AM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
So sorry to hear about Ethan, prayers for his family.
Thank you for posting. It is always good to talk about safety issues.
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Fiero Vice
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Report this Post08-11-2021 11:57 AM Click Here to See the Profile for Fiero ViceSend a Private Message to Fiero ViceEdit/Delete MessageReply w/QuoteDirect Link to This Post
Dear FieroGuru,

Your diagram doesn't prove a point because my triangle stands have the widest legs of my all stands, including my 6 ton stands. It's impossible to knock it over if I tried. Now, with my 6 ton stands, I could knock it over easily.

Out of curiously, when I put my feet on two triangle stands, it felt very secured & not even shaky at all, even if I tried. Now, when I tried to put my feet on my 6 ton stands, the top pieces are shaky because of its lousy design and can tip over if I tried. I had to hold on to the wall when I attempted to do this.

That's why ESCO triangle stands got an excellent review. Strength & Stability should go hand in hand.

With all due respect, I guess we agree to disagree. I would recommend that you buy one & test it out yourself against your other stands.

[This message has been edited by Fiero Vice (edited 08-11-2021).]

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Report this Post08-11-2021 04:31 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Fiero Vice:
Dear FieroGuru,

Your diagram doesn't prove a point because my triangle stands have the widest legs of my all stands, including my 6 ton stands. It's impossible to knock it over if I tried. Now, with my 6 ton stands, I could knock it over easily.

Out of curiously, when I put my feet on two triangle stands, it felt very secured & not even shaky at all, even if I tried. Now, when I tried to put my feet on my 6 ton stands, the top pieces are shaky because of its lousy design and can tip over if I tried. I had to hold on to the wall when I attempted to do this.

That's why ESCO triangle stands got an excellent review. Strength & Stability should go hand in hand.

With all due respect, I guess we agree to disagree. I would recommend that you buy one & test it out yourself against your other stands.



I stated I didn't recommend triangle stands. You asked why. I responded twice in detail to support my position, you choose to agree to disagree... I don't get it... This is the thread about educating people of the hazards with jack stands, which is exactly what I am trying to do.

I suspect your triangle stands with the "widest legs of all my jack stands", might "feel" more stable to your other options... especially if the base dimension is more than 40% wider than your square jack stands.
Care to state the dimensions of both?

If the triangle base is 40% larger than your square based stands, then it should feel as sturdy as your smaller square jack stands.
If the triangle base is 50% larger than your square based stands, then it will be a sturdier jack stand - between the two you compared.

If we want a real comparison between the two shapes of bases, then you have to use the same size base (which is what I detailed above). When this is done, the square beats the triangle for stability every time. The only time the triangle base ends up being sturdier is when it is substantially larger than the available square base.

If I am going to have a 12" base for a jack stand, it will be a 12"x12" square base. You are more than free to make a different decision.

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Fiero Vice
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Report this Post08-11-2021 05:47 PM Click Here to See the Profile for Fiero ViceSend a Private Message to Fiero ViceEdit/Delete MessageReply w/QuoteDirect Link to This Post
Dear FieroGuru,

Yes, this is the thread about educating people of the hazards with jack stands. And I greatly appreciate all of your feedback.

You have knowledge that is beyond than most of us Fiero enthusiasts. And your products are awesome.

I wasn't trying to offend you at all. I'm just surprised that you have a different opinion on a product that has excellent reviews.

I'm not trying to force it on you or anything.

Thank you.

[This message has been edited by Fiero Vice (edited 08-12-2021).]

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Jerb
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Report this Post09-06-2021 02:31 AM Click Here to See the Profile for JerbSend a Private Message to JerbEdit/Delete MessageReply w/QuoteDirect Link to This Post
That's so awful!!! I only got to talk to him a couple times, but he seemed like a really good dude. I hope his family can get through this and keep going.

Buy a set or two of wheel chocks. Even the cheap plastic stackable ones in the trailer section are good. Just keep them behind the seat, you need them anyway for changing a flat, or having ebrake / trans issues. Place chocks both forward and behind the wheels opposite the jack.

If you're going to break a wheel off the car for any reason, lay it flat and slide it under the cars rockers. It's bad enough just having a jack go off-axis with just a tire change. Especially do this if you're going to crawl under the car. The car "only" falling to 'Width of Rim' off the ground gives you, your friend or family member, and first responders a lot more to work with.

Do NOT EVER use concrete blocks with the lightening holes in them to support anything. All of their strength is in the web direction, they fail suddenly and without warning, they can't tolerate point loads, or off axis loads... Look you can break these blocks over a dudes stomach without hurting him, they won't even slow down a car.

Lift the car to the needed height, and place your jackstands with good footing, set the locks. Ease the car down fully on the stands. Wiggle stands to see if they feel secure. Stand back up, SHAKE the car. If it's not solid, you are NOT jacked. Try again, add jack pads below stands, cribbing...if it wobbles, just don't.

Once the car is firmly seated on the stands, and everything feels secure, bring the hydraulic jack back up to a little bit (couple inches) Below the jacking hard point. I don't expect the o-ring in the jack to catch a car in an accellerating freefall. We just want it obvious where it needs to lift, and ready to start pumping.

If you need to do something that takes a sketchy amount of torque, find a way to bring it out from under the car. A couple feet of impact-rated 1/2" drive extension coming out to rest across another jackstand sitting on cribbing next to the car can take away the leverage that was going to make the car shift on the jack stands

When someone comes across a person that's pinned under a car, don't make them have to guess or work to find where these stupid jacking points are hidden! Most people don't do well under stress, help stack the deck for you, and your rescuer.

[This message has been edited by Jerb (edited 09-08-2021).]

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Patrick
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Report this Post09-06-2021 07:57 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Jerb:

<snip>


Jerb, good post in a meaningful thread.
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