Help with anchor and bolt sizing calcualtions

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Discussion Overview

The discussion revolves around the calculations needed to determine the appropriate anchor and bolt sizing for a robot setup, considering the weight of the robot and the dynamics involved in its operation. Participants explore various factors affecting the strength and stability of the mounting system, including the weight distribution and rotational speed of the robot's arm.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant states the robot weighs 900kg and has a maximum reach with an additional weight of 110kg at the end, raising concerns about the strength of the anchors used.
  • Another participant inquires about the maximum weight on the arm and the specifications of the stud anchors, indicating a need for clarity on these points.
  • Participants discuss the calculation of forces involved, with one providing a rough estimate of 2500 lbf based on their calculations, suggesting this provides a significant safety factor for the bolts used.
  • There is a mention of the rotational speed of the robot arm and its potential impact on the required force, with one participant questioning whether this would necessitate additional considerations for the moment created by the arm's movement.
  • Another participant expresses uncertainty about the calculations and the dynamics involved, indicating a desire to learn from the ongoing discussion.
  • One participant suggests that the manufacturer may be the best source for accurate information regarding the machine's requirements.
  • There is a suggestion to calculate the moment of inertia for the arm and consider dynamic loads, with a recommendation to apply a safety factor to ensure stability.

Areas of Agreement / Disagreement

Participants express various viewpoints on the calculations and factors to consider, with no clear consensus reached on the adequacy of the current calculations or the best approach to ensure safety in the mounting system.

Contextual Notes

Participants mention various assumptions and calculations, including the neglect of certain angles and the need for further clarification on the weight distribution and forces involved. The discussion reflects a range of uncertainties and dependencies on specific parameters that remain unresolved.

Who May Find This Useful

Individuals interested in robotics, mechanical engineering, or structural analysis may find this discussion relevant, particularly those involved in the design and mounting of dynamic systems.

JCSS
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TL;DR
Help with anchor and bolt sizing calcualtions
The robot weight is 900kg
I have a robot with max reach swinging around with a weight of 110kg at the end at 125 degree/s
I am not sure if the anchors I use are strong enough to hold it down assuming i mount the robot at the centre of the mounting plate
Any advice with doing calculations to do a sanity check?
I am also using M20 bolts to mount the robot to the base with 24mm thread engagement Class 12.9 bolts x 8 around the diameter Space around roughly at L1=300mm

Thanks
DIAGRAM.png
 
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Hello,
Do you happen to also know what the max weight you will be holding on the arm is also?

Are those stud anchor specs in imperial?

Thanks,

jeff
 
Hi Jeff,
The max weight in the arm will be 110kg at distance 300mm+ 1172mm+1227mm+769mm = 3468mm
the stud anchor specs are in imperial

Thanks
 
JCSS said:
Hi Jeff,
The max weight in the arm will be 110kg at distance 300mm+ 1172mm+1227mm+769mm = 3468mm
the stud anchor specs are in imperial

Thanks
what is W3? (weight of arm)

thanks

jeff
 
jeff davis said:
what is W3? (weight of arm)

thanks

jeff
Hi Jeff
This diagram is the correct info. W3 =0
DIAGRAM.png

thanks
 
Hello,
I am getting around 2500 lbf total just from rough calc.

so 1100 pullout of your bolts x 8pcs should be more than enough.

thats a good 350% safety factor. That is for the arm to the plate. You would need more anchors for the plate to the ground of the same strength. The force would be a little less because of the weight of that thick base.

What did you get?
 
(627*.3 + 518 * 1.172 + 190 * 1.227 + .769 * 110)* 9.81 = 10917.7 N = 2454.4 lbf

i neglected the 125 degree angle because this would only reduce the total force. worst case scenario is if someone puts the arm straight out.
 
Hi Jeff ,
The 125 degree / second is rotational speed of the robot spinning around , wouldn't that cause a moment and require more force?
I have additional information
I have the same results in your first step but your units should be KG*M X 9.81M/S^2 = KGM^2/S^2 Which N*M = joules
DIAGRAM 2.png


Thanks
 
Oh. Ok. I was thinking about it in just the x,y plane. Yeah that would cause a moment for sure. You probably would be worried about the arms movements in and out also. That would have some inertia also. Not sure if it would be more than the rotational inertia?

I'm not good enough at such calculations to be much help for you. I'd love to see yours when your done though to maybe learn a thing or two.

Maybe theven place you got it from would have these forces charted out?

Jeff
 
  • #10
The only source of sufficient knowledge about the machine's requirements to answer your questions is the manufacturer.
 
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  • #11
bummer,
Im surprised more people have not chimed in here. Ususally they do.

You could probably derive the moment of inertia for the arm easily enough but I am not sure how to translate that to the bolts as a force. It is a pretty dynamic load. I bet that the in and out movement force would be greater than the rotational force. maybe if you just calculate for that and then add a safety factor of 100% you would be covered.

You I am sure are already thinking of these things. Just throwing stuff out.
 

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