Help with anchor and bolt sizing calcualtions

[JCSS]

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

 

[jeff davis]

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

 

[JCSS]

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

 

[jeff davis]

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

 

[JCSS]

what is W3? (weight of arm)

thanks

jeff

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

thanks

 

[jeff davis]

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?

 

[jeff davis]

(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.

 

[JCSS]

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

Thanks

 

[jeff davis]

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

 

[JBA]

The only source of sufficient knowledge about the machine's requirements to answer your questions is the manufacturer.

 

[jeff davis]

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.