OT: any physics gurus here?:OT

RRP

This is an old picture - taken 16 years ago, but should work for this purpose.


Recently I had to replace the deck boards under which the "legs" on the right side had started to sag.
Then when I checked the condition of those plastic wheels on the left side the outer wheel just cracked and nearly broke apart! These are 8" plastic rims and after 16 years I need to replace them! Today I purchased 2 new steel rimed ones. The label says they can only support 60 pounds each. I then checked the labeling on similiar plastic rims being sold and they were listed as only 20 pounds. My guess is these new 60 pounders should easily support the load. OR should I spring for more expensive wheels? I just don't know how to calculate the weight load strength of two 60 pounders on a 1/2" steel axle. Can any physics gurus help me out?

DMW

You probably would be better off soliciting the advice of an engineer rather than a physicist.

Botch

I shall do so, if you can wait until tomorrow.  Right now there's a unicorn urinating in my kitchen.  >hic<

Legume

It seems to me you have four points supporting the weight.  So if you know the total weight, divide by four and that should be all the math you need.  If it’s close to the limit of the wheels, then buy heavier wheels.

Legume

Wait, what kind of steel is that axle made of?

DMW

Legume said:

It seems to me you have four points supporting the weight.  So if you know the total weight, divide by four and that should be all the math you need.  If it’s close to the limit of the wheels, then buy heavier wheels.

It's a bit more nuanced than that, but for this project, that math is probably close enough.

Legume

Well, so you want to calculate at precisely what weight it’s gonna fail?  Or do you want to make sure you have enough wheel?  The total weight’s gonna be a guesstimate as it is.

RRP

Thanks to all of you! - I'm off to bed!

DMW

Legume said:

Well, so you want to calculate at precisely what weight it’s gonna fail?  Or do you want to make sure you have enough wheel?  The total weight’s gonna be a guesstimate as it is.

Yeah, that's what I'm getting at. The overall weight is not uniformly distributed. There's a large egg on one side, and a small egg with storage space on the other. The required weight load for the wheels on the left side is probably (I don't know the contents of the storage space) not equal to the weight load for the right side. Again, I'm skating on a bit of thin ice here, as my engineering experience isn't in the area of civil engineering. A bridge engineer would probably be useful here. 

nolaegghead

60 pounds dynamic load (moving)...probably be fine to support 100 plus if you don't move it over cobblestones. 

Legume

How many miles/year on those wheels?  When you move it, it’ll be all the weight on just the wheels, but you’ll be lifiting some of it.  How high off the ground do you lift it?

Gotta figure in full loads of lump and whatever you’re cooking, like 15 lb brisket, 10 lb pork belly, etc.

DMW

Legume said:

How many miles/year on those wheels?  When you move it, it’ll be all the weight on just the wheels, but you’ll be lifiting some of it.  How high off the ground do you lift it?

Gotta figure in full loads of lump and whatever you’re cooking, like 15 lb brisket, 10 lb pork belly, etc.

Right here, these variables you mentioned, are why I have not volunteered any advice. I'm more than a few years from any course that would have covered such material. And, I have not exercised said material in any professional capacity ever. 

Now, if you are interested in how to best construct a leaf/spine network fabric for an enterprise data center, I might have some insightful input.

Legume

DMW said:

Legume said:

How many miles/year on those wheels?  When you move it, it’ll be all the weight on just the wheels, but you’ll be lifiting some of it.  How high off the ground do you lift it?

Gotta figure in full loads of lump and whatever you’re cooking, like 15 lb brisket, 10 lb pork belly, etc.

Right here, these variables you mentioned, are why I have not volunteered any advice. I'm more than a few years from any course that would have covered such material. And, I have not exercised said material in any professional capacity ever. 

Now, if you are interested in how to best construct a leaf/spine network fabric for an enterprise data center, I might have some insightful input.

Buy more wheel than you need, sleep well at night.  

DMW

Legume said:

DMW said:

Legume said:

How many miles/year on those wheels?  When you move it, it’ll be all the weight on just the wheels, but you’ll be lifiting some of it.  How high off the ground do you lift it?

Gotta figure in full loads of lump and whatever you’re cooking, like 15 lb brisket, 10 lb pork belly, etc.

Right here, these variables you mentioned, are why I have not volunteered any advice. I'm more than a few years from any course that would have covered such material. And, I have not exercised said material in any professional capacity ever. 

Now, if you are interested in how to best construct a leaf/spine network fabric for an enterprise data center, I might have some insightful input.

Buy more wheel than you need, sleep well at night.  

Think this is big enough?

HeavyG

THose are wheels and not casters so they just essentially move lineally which is a lot less stressful than casters having to move every which way experiencing side loading until they swivel around. I'm sure the 60 pounds per wheel will be fine as they are probably designed to handle two or three times that weight before anything disastrous happens to them. You don't need to worry about that table and its contents weighing anywhere close to the weight needed to shear or bend a 1/2" steel axle.

If you are concerned about really knowing the weight on each wheel just get your bathroom scales and place them under each wheel and that'll give you the actual weight loading on each wheel.

MaskedMarvel

You may be better off with a REGULATION guru...

the maximum weight advertised for those wheels is a fraction of the ACTUAL weight they can take. Like a CO2 tank - they can handle a lot more before failure...

JohnInCarolina

Legume said:

How many miles/year on those wheels?  When you move it, it’ll be all the weight on just the wheels, but you’ll be lifiting some of it.  

No.  When you lift it, you’re just transferring the contact points from the deck to your hands.  All of the weight does not transfer to the wheels on the left side when you pick it up on the right.

Taking the total weight of the table (with Eggs, etc.) and dividing by four is a very good estimate here.  If you want better than that, you can determine the mass and locate the center of mass of each component and figure out the moment balance and ... that’s going to take awhile.  Alternatively, yes, you can place a scale under both wheels and both legs on the right, although I don’t know too many folks with four bathroom scales in their house but this is Ron so who knows.

And any decent first year engineering student in college can help you with this.  Physics majors too of course.  

alaskanassasin

Spring for the heavier casters! Your eggs deserve the best

1voyager

Keep the steel ones for the "cool factor".

Otherwise, I need to know these variables:

Weight (load) on all four wheels

Diameter of rim

External diameter of tires

Width of tire

Diameter of axel

Mean density of steel rim - or maximum shear stress

Carolina Q

With large and small eggs (162+80 lb, or is that a med @ 114?), the table (no idea, say 150 max), 100 lb misc accessories, 20 lb lump and 50 lb of butts, that's 562-596 lbs. Weight distributed unevenly of course, but maybe not, depends on what's under that smaller egg. And anyway, it doesn't matter.

Head down to Harbor Freight in East Peoria (or online of course) and buy two of these for $14. 300 lb ea, 8" dia, steel wheels, ball bearings, they take a 5/8" axle and have solid rubber tires so no flats to deal with. Overkill I'm sure, but so what, they're $6.79 each!

https://www.harborfreight.com/8-inch-solid-rubber-tire-42427.html

And they're even GREEN!

ColtsFan

I think you should make the axle longer and add more wheels. Duals on the outside and 2 in the center. 

1voyager

Something like this?

theyolksonyou

JohnInCarolina said:

Legume said:

How many miles/year on those wheels?  When you move it, it’ll be all the weight on just the wheels, but you’ll be lifiting some of it.  

No.  When you lift it, you’re just transferring the contact points from the deck to your hands.  All of the weight does not transfer to the wheels on the left side when you pick it up on the right.

Taking the total weight of the table (with Eggs, etc.) and dividing by four is a very good estimate here.  If you want better than that, you can determine the mass and locate the center of mass of each component and figure out the moment balance and ... that’s going to take awhile.  Alternatively, yes, you can place a scale under both wheels and both legs on the right, although I don’t know too many folks with four bathroom scales in their house but this is Ron so who knows.

And any decent first year engineering student in college can help you with this.  Physics majors too of course.  

You didn’t drink enough bourbon last night. 

theyolksonyou

If the previous plastic ones lasted 16 yrs,it’s a pretty safe bet the steel ones will work for a while...

Eoin

When you said that the plastic wheels fell apart after 16 years, that's probably degradation and not pure load. The rated load will be moving, so the static load will be higher and for ths distance / speed you are moving, the load can be considered as static. Also, a half inch axle will take a huge static load compared to what you are supporting.

JohnInCarolina

theyolksonyou said:

JohnInCarolina said:

Legume said:

How many miles/year on those wheels?  When you move it, it’ll be all the weight on just the wheels, but you’ll be lifiting some of it.  

No.  When you lift it, you’re just transferring the contact points from the deck to your hands.  All of the weight does not transfer to the wheels on the left side when you pick it up on the right.

Taking the total weight of the table (with Eggs, etc.) and dividing by four is a very good estimate here.  If you want better than that, you can determine the mass and locate the center of mass of each component and figure out the moment balance and ... that’s going to take awhile.  Alternatively, yes, you can place a scale under both wheels and both legs on the right, although I don’t know too many folks with four bathroom scales in their house but this is Ron so who knows.

And any decent first year engineering student in college can help you with this.  Physics majors too of course.  

You didn’t drink enough bourbon last night. 

I think maybe you had my share on top of yours.

johnnyp

What’s that force in kips? 

1voyager

@johnnyp That should be intuitively obvious even to the most casual observer. 

JohnInCarolina

1voyager said:

@johnnyp That should be intuitively obvious even to the most casual observer. 

At a moment’s glance.

theyolksonyou

JohnInCarolina said:

theyolksonyou said:

JohnInCarolina said:

Legume said:

How many miles/year on those wheels?  When you move it, it’ll be all the weight on just the wheels, but you’ll be lifiting some of it.  

No.  When you lift it, you’re just transferring the contact points from the deck to your hands.  All of the weight does not transfer to the wheels on the left side when you pick it up on the right.

Taking the total weight of the table (with Eggs, etc.) and dividing by four is a very good estimate here.  If you want better than that, you can determine the mass and locate the center of mass of each component and figure out the moment balance and ... that’s going to take awhile.  Alternatively, yes, you can place a scale under both wheels and both legs on the right, although I don’t know too many folks with four bathroom scales in their house but this is Ron so who knows.

And any decent first year engineering student in college can help you with this.  Physics majors too of course.  

You didn’t drink enough bourbon last night. 

I think maybe you had my share on top of yours.

That’s certainly a plausible theory

nolaegghead