Impact of trolley - hand calculation method

[Mech King]

Hello,

Been a while since I posted on here, nice to be back :) .

I just want some pointers as to the methodology for an impact load case that I'm looking at. I've attached a very basic sketch of a trolley which is traveling at a known velocity and impacts a rigid structure at it's base.

What I'm going to do is to determine the stiffness of the trolley at it's impact location, then calculate the deflection and resulting force by utilising conservation of energy between the KE of the trolley and the spring energy of the system. So I can do all that and obtain the impact force and look at my stresses. But once the trolley impacts, it will decelerate rapidly and tend to rotate about the pivot shown on the bottom view of the attached diagram. The restoring moment due to weight of the trolley relative to the CoG will not be enough to prevent it from rotating clockwise toward the rigid structure.

I'm confused on how to work out how far the trolley will rotate and whether it will impact the rigid structure at the top - denoted by "point A" on the attached bottom image.

I was going to use the inertia of the trolley to determine this, but I'm very confused, because I have both linear kinetic energy and rotational kinetic energy. If I can work out the height that the CoG will rise to on impact then I can calculate the angle of rotation, but is this too simplistic? I'd have to equate the

rotational KE to the PE, but PE=mgh is linear :/ ?

I'm really confused! Any pointers for my approach would be so appreciated.

Many thanks

 

[rigetFrog]

I wasn't able to glean what you're trying to calculate. Could you give me the units (e.g. Newtons, meters, kg, etc...) of what you're trying to calculate.

Hints
1) draw the force vectors in figure 2. And then draw the vector you want to calculate.

2) don't use the word utilize or any of its weird spelling. You know what they say about people you "utilize"? They make a tool out of you and ize.

 

[Mech King]

Hey, thanks for your reply.

I don't need units, it's a the method I'm discussing! I a freelance chartered engineer and stress analyst - a d u use the word utilise often; it's a word lol.

I have solved the problem now, but wanted to discuss my approach! Maybe there is a better way of doing it!

 

[Mech King]

Apologies for typos - can't type on my iPhone :/

 

[PJC01]

,Hello there,

First of all, it's great to have you back on the forum! As for your question, determining the impact of the trolley using hand calculation method can be a challenging task. However, there are a few steps you can follow to help guide your approach.

1. Start by determining the stiffness of the trolley at its impact location. This can be done by analyzing the materials and dimensions of the trolley. You can also consider the impact speed and angle to get a more accurate stiffness value.

2. Next, calculate the deflection of the trolley upon impact using the conservation of energy principle. This will give you an idea of the displacement of the trolley upon impact.

3. To determine the impact force, you can use the formula F=ma, where F is the force, m is the mass of the trolley, and a is the acceleration caused by the impact.

4. As for the rotation of the trolley, you can use the principle of conservation of angular momentum. This means that the initial angular momentum of the trolley will be equal to the final angular momentum after impact. You can calculate the initial angular momentum using the rotational kinetic energy formula, and the final angular momentum using the formula L=Iω, where I is the moment of inertia and ω is the angular velocity.

5. Finally, to determine if the trolley will impact the rigid structure at the top, you can use the principle of conservation of energy again. If the potential energy of the trolley at the top is greater than the kinetic energy at impact, then the trolley will collide with the structure. If not, then it will not reach the top.

I hope this helps guide your approach to solving the impact load case. It's important to keep in mind that hand calculations can be limited in their accuracy, so it may be helpful to also consider using computer simulations or experimental testing to verify your results. Good luck with your analysis!