Sunday Morning Quickie: Tool Time. Lets talk 3 leg axle stands.

[Mart]

Just a little quickie for Sunday. Axle stands. Here's my view on 3 legged ones. As with any safety critical item always use your best judgement and keep within the design limitations.

https://youtu.be/X78otmSeOZk

Mart.

[1931 flamingo]

Informative. Thanks for posting. I've got a pair from a loooong time ago.
Paul in CT

[51 MERC-CT]

Interesting and makes sense if not elevated. The pin that is used to locate height also regulates the orientation of the seat. If the orientation is the same then it's OK.
Speaking of the height locating pins, a number of years ago, locally, there was an account in the paper of someone who was pinned an killed under a car when one of the stands collapsed due to the use of an engine valve instead of the (lost) dedicated pin.

[19Fordy]

51 Merc: I think that's why Henry Ford used bolts that would bend before they reached their breaking point. No snapping of brittle hardened materials like valves.

[19Fordy]

Bottom line.
AVOID USING THREE LEGGED ANYTHING THAT IS SUPPORTING SOMETHING YOU'LL BE CRAWLING UNDER.

[DocJohn]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by 19Fordy

Bottom line.
AVOID USING THREE LEGGED ANYTHING THAT IS SUPPORTING SOMETHING YOU'LL BE CRAWLING UNDER.

That's not consistent with advice from the UK Health and Safety Executive. Maybe things are different over the pond.

[Brian]

I've always used ones I made out of V8 axle housings

[Mart]

^^ yeah, I've got a couple of those too..

[dumb person]

3 legged stands are more stable than 4 legged ones.

[51 MERC-CT]

Originally Posted by dumb person

3 legged stands are more stable than 4 legged ones.

Sure they are

[tubman]

What ever happened to "Right as a trivet"?

[Jay in Mass]

Originally Posted by 51 MERC-CT

Sure they are

51 Merc
"Someone said a picture s worth a thousand words"
Thank you for your picture.

[tubman]

That looks like a rusty piece of crap to me. I wouldn't use it if it had 5 legs.

[swedishsteel]

On that stand the number of legs had nothing to do with it bending in the middle. three legs will never be rocky rocky like four will. The width of stance in relation to the height and the overall strength are most important.

[tomcarman]

Mart is correct. He attempts to counteract the applied forces. With a degree in architecture and an emphasis on static structures, (no not static electricity buth rather static as in something that doesn't move or you don't want to move) I hope to explain this with quickee sketches. An applied force will always travel directly towards the center of the earth. If it meets resistance it will split the applied load and try and travel directly towards the center of the earth at a 45 degree angle, no matter the resisting forces angle. A very important thing to be concerned with is what's called a hinge point. That is a point where the load meets an unsecured connection with resistance. Hinge points can be overcome, but unsecured hinge points are dangerous. What Mart is showing is to try and counteract a tripod with 2 hinge points by turning them to counteract the applied force(s). As we all know getting a load off center will cause something to topple. (ever get drunk and fall down?). Same physics apply. Each time a load is split the resultant force gets divided by the number of points of resistance. Each load point resists weight by how far the load is off center and its resistance. The tripod shown is a result of an overload where the compressive strength of the steel was overcome by a load. Tripods are not nearly as stable as 4 points of contact. Tripods are commonly used as orchard ladders. Why, because they rest on uneven ground, where 4 points of contact like flat ground. The other force to consider though less likely to occur in this application is a lateral force, e.g. wind or someone leaning on the car while it's off center

[tomcarman]

Originally Posted by 51 MERC-CT

Interesting and makes sense if not elevated. The pin that is used to locate height also regulates the orientation of the seat. If the orientation is the same then it's OK.
Speaking of the height locating pins, a number of years ago, locally, there was an account in the paper of someone who was pinned an killed under a car when one of the stands collapsed due to the use of an engine valve instead of the (lost) dedicated pin.

Whenever we work under cars we always take an extra precaution such as putting plenty of wood blocks, old tires, concrete blocks and such under the car.That way should the vehicle topple at least it won't make it all the way to ground. I once saw a fat guy under his car changing his oil with the car jacked up in the front with a bumper jack.

[Brian]

Concrete blocks aren't too safe!

[tomcarman]

Originally Posted by Brian

Concrete blocks aren't too safe!

The compressive strength of a concrete block, CMU is 2000lbs/SI. Source: ASTM.C90. Concrete is excellent in compressive strength, worthless in tensile strength.

[dumb person]

Originally Posted by 51 MERC-CT

Sure they are

On uneven ground, yes.
4 legged ones rock all the time.

[Mart]

From reading all the comments it seems to me that the design of the stand is not as important as:
The evenness of the ground.
The levelness of the ground.
The firmness of the ground.
The actual quality and condition of the device.
The height to base footprint ratio.
The side loads exerted while working.

When working we all have to weigh up the risks involved. Just understanding that there is risk involved is the first step. How to handle and take steps to mitigate that risk is the next.

I wasn't trying to start a controversy. I just wanted to point out some salient points regarding the arrangement.

I respect peoples views and the fact that people mitigate the risk in their own way.

Mart.