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OT: Engineering Force Question

Knight Shift

Knight Shift

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May 19, 2011
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I was horrible at engineering dynamics. Maybe they should revoke my degree. 😜

The manual for a pickup truck says:
Maximum force between diagonally opposed cleats (Diagonal B)=600 lb





Does that mean 600 lb is on each of the cleats, or 300 lbs on each cleat?

The real question is what if I wanted to use the cleats closest to the front of the bed to pull a heavy load into the back of the truck up a ramp--What is the maximum load that could be pulled if a ratchet strap was attached to the two front cleats and to the load on a ramp sliding up over the license plate shown by the dashed arrow?

300 lbs?
600 lbs?
1200 lbs?

Thanks.
 
Last edited:
ScarletDave

ScarletDave

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Oct 7, 2010
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First off that means 600 lbs on each. Anything tied along axis B would have the same force on both straps. A 300 lb force on both is a 300lb force.

HOWEVER, that doesn’t mean you can go up to 600 lbs doing what you are describing. The hook is designed to support 600lbs along axis B (kind of 45 degree angle but more perpendicular to the side wall) .. what you’re describing would be a force more parallel to the side wall .. so, the hook isn’t designed to take as much force that way - it’s a shear force rather than a tensile force. I would guess that I would not go more than 400lbs that way, just based on the angles.
 
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Knight Shift

Knight Shift

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May 19, 2011
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ScarletDave said:
First off that means 600 lbs on each. Anything tied along axis B would have the same force on both straps. A 300 lb force on both is a 300lb force.

HOWEVER, that doesn’t mean you can go up to 600 lbs doing what you are describing. The hook is designed to support 600lbs along axis B (kind of 45 degree angle but more perpendicular to the side wall) .. what you’re describing would be a force more parallel to the side wall .. so, the hook isn’t designed to take as much force that way - it’s a shear force rather than a tensile force. I would guess that I would not go more than 400lbs that way, just based on the angles.
Click to expand...
I should add that the manufacturer recommendation between arrow A is:
Maximum force between directly opposed cleats 276 lb.

Does that perhaps indicate that as the angle moves towards 60 degrees, the force can be increased or decreased? It seems the maximum tensile force normal to the cleats is 1/2 the max tensile force on the diagonal, so perhaps the max shear force at a greater angle may be even greater?


As I said, I was awful at engineering mechanics. If my memory is correct- first midterm, scored 9 out of 100, but still got a B grade!!!
 
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RutHut_rivals

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I interpret that the "pull-out" capacity of the cleat at an approximate 45 degree angle is 600 lbs. If the tension to each cleat is distributed evenly then you should be able to pull at least 1200 lbs maybe a little more to get to the outside of the bed. From there push into bed (I assume on wheels). But just remember, I'm just a manager, and sign what they tell me to sign, and the whole "diagonal" cleat guidance does not seem to apply to this application. Any good engineer would factor a deadload by 1.3 to allow a factor of safety and include a caveat to cover his ***. 😜
 
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Knight Shift

Knight Shift

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RutHut said:
I interpret that the "pull-out" capacity of the cleat at an approximate 45 degree angle is 600 lbs. If the tension to each cleat is distributed evenly then you should be able to pull at least 1200 lbs maybe a little more to get to the outside of the bed. From there push into bed (I assume on wheels). But just remember, I'm just a manager, and sign what they tell me to sign, and the whole "diagonal" cleat guidance does not seem to apply to this application. Any good engineer would factor a deadload by 1.3 to allow a factor of safety and include a caveat to cover his ***. 😜
Click to expand...
Yeah, trying to figure out a safe way to pull/push lawn tractor up on ramps. It is possible to drive the tractor up the ramps, but I want to live to see the holidays without any broken bones.
 
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GoodOl'Rutgers

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use a ton of pulleys.. what they hell was it called.. I'll find the cool youtube..

Ahh.. why snatchblocks are awesome....



 
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Knight Shift

Knight Shift

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GoodOl'Rutgers said:
use a ton of pulleys.. what they hell was it called.. I'll find the cool youtube..

Ahh.. why snatchblocks are awesome....



Click to expand...

LOL. You said snatch block! A multi-pulley system or what the deer hunter did crossed my mind. A double pulley system will give a 3 to 1 mechanical advantage. We utilize mechanical advantage quite a bit in fire department rescue training scenarios when we have to do drags of heavy victims. Great suggestions!

If none of that works out, since you posted a deer hunter:

 
T2Kplus20

T2Kplus20

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Knight Shift said:
I was horrible at engineering dynamics. Maybe they should revoke my degree. 😜

The manual for a pickup truck says:
Maximum force between diagonally opposed cleats (Diagonal B)=600 lb





Does that mean 600 lb is on each of the cleats, or 300 lbs on each cleat?

The real question is what if I wanted to use the cleats closest to the front of the bed to pull a heavy load into the back of the truck up a ramp--What is the maximum load that could be pulled if a ratchet strap was attached to the two front cleats and to the load on a ramp sliding up over the license plate shown by the dashed arrow?

300 lbs?
600 lbs?
1200 lbs?

Thanks.
Click to expand...
As a ChemE, I have no idea about those forces. However, I can blow-up that truck if you would like!
😁

 
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kupuna133

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Knight Shift said:
What fun is that?
Click to expand...
Fun in having all my limbs, functioning back and pride in tact. Because I know how it would end for me.

Not to mention saving on damage to truck. But my brother the engineer regularly attempts these stunts and usually ends well. Usually….
 
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Knight Shift

Knight Shift

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kupuna133 said:
Fun in having all my limbs, functioning back and pride in tact. Because I know how it would end for me.

Not to mention saving on damage to truck. But my brother the engineer regularly attempts these stunts and usually ends well. Usually….
Click to expand...
Ya know, I thought about what you suggested. Right around the corner in Squan on Broad and Main, reserved this, which has a ramp. $25 bucks, which is cheaper than broken bones and a broken heart. I will use the ramps still, but for snowblower and other stuff.

I'll buy you breakfast at the Committed Pig if you help me load the tractor! 😉

 
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kupuna133

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Knight Shift said:
Ya know, I thought about what you suggested. Right around the corner in Squan on Broad and Main, reserved this, which has a ramp. $25 bucks, which is cheaper than broken bones and a broken heart. I will use the ramps still, but for snowblower and other stuff.

I'll buy you breakfast at the Committed Pig if you help me load the tractor! 😉

Click to expand...
Would be happy to help! But ….remember not an engineer.
 
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Knight Shift

Knight Shift

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kupuna133 said:
Would be happy to help! But ….remember not an engineer.
Click to expand...
I've enlisted my better half. She's an engineer (same degree as me) plus a master's in statistics. She is calculating the probability of failure and angst (always very high) right now. What could go wrong? If open and not swamped, will take her to the CP for breakfast.
 
iReC89

iReC89

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How much weight can the gate support?

I backed my mover down a rental truck on provided ramps when I bought it. I learned from that process that I never want to do that again, but someone with a better comfort level for these things would send it no problem.

It will be interesting to see if your wife suggests you go for it. I'm not saying get a second opinion, but make sure you understand the status of the relationship. Calculations of risks and costs entering the equation, I think you know you are going to end up calling someone to take it.


ps This is more of a process design issue (IE).
 
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