Breakable Bolt Calculation (first post on this forum)

Tried to have a look but the combination link+user + pass word did not work I got a blank only.

I shall look tomorrow again check if there is not somewhere a problem.

Hi Nick,

I've been watching our FTP log and it seems some people can get in and some can't.

Are you using Internet Explorer? If you are I don't know what the problem might be.

I don't think you can use FTP in Firefox.

I'm not sure I understand any of this, but, I'll make the following observations:

On a totally trivial point pi is approx 3.141593 try using PI()

Again trivial, but for clarity column C is in PSI and column D should be total force (not PSI) I think?

In excel you can always put in brackets to make sure you've got things right (leaving them out where they should be can be disastrous!).

Should cell H2 function=D2*(E2/F2)/G2 [total force times (ratio of distance to toggle end over distance to shear bolts)over # of bolts]

And, J2=H2*((100+I2)/100) OR J2=H2*(1+I2/100)

All these give the same answers (except pi of course) but make things a little easier to follow.

Finally it seems very unlikely that the yield strength of a bolt (cylinder of metal) will be linearly proportional to its diameter. Perhaps this is because I do not understand what you mean by ¼ radius groove. Where did you get the value 87200 from?

(Confirm that the link didn't seem to work in Firefox but did using IE).

Hi Randall and anyone else who is interested,

I should probably explain that our companys' meat and potatoes is the manufacture and refurbishing of rock crushers. We also act as the middle man between the hydraulic toggle manufacturer and the end user.

Hinged Safety Toggle Comparison Calculations.pdf was written by an engineer under contract to the hydraulic toggle manufacturer and a copy was kindly passed on to us. My boss won't allow me to contact the author as it will cost $s and I have nowhere else to go.

Given that there are many different sizes of rock crushers, it follows that they would use varrying sizes of hydraulic toggles, back safety toggles and breakable toggle bolts. When the breakable bolts fail in a back safety toggle we are often asked to supply new ones most often without knowing what the originals looked like.

Up untill now we have mostly been guessing what the dimensions of the required bolts are. This is why I decided to write Shear Bolt Groove Diameter Calculation.xls. Through the input in the yellow cells the diameter of a 1/4" radiusd groove in the breakable bolt is calculated.

Page 9 in Hinged Safety Toggle Comparison Calculations.pdf shows a cross-section of the hinged toggle through the breakable bolt. The groove is designed to weaken the the bolt by reducing the outside diameter in the middle of the length of the bolt.

Page 9 shows only a stud but there is actually a heavy nut and washer on both ends. In this example the bolt diameter is 1 3/4" and the groove diameter is 1.288".

Randall: as far as the 87200 value is concerned, after conciderable research over a period of several months trying to solve this problem I failed to get even close to it. I figured my best bet was to use the values in Hinged Safety Toggle Comparison Calculations.pdf.

Given on page 8: <"Individual Safety Release Load" is said to be 112,315 lbs.> (calculated in cell J2 of Shear Bolt Groove Diameter Calculation.xls)

Given on page 8: <The toggle bolt has a 1.288" Dia. at its weakest tensile point.> (calculated in cell K2)

Assumed: if 112,315/1.288=87,000(aprox) then 112,315/87,000=1.288

Now that you mention it, it does'nt look right but I'm not sure what it should be.

I've made the changes you already suggested but can't upload to the FTP 'till I get to work tomorrow.

On a side note, in these days of fierce competition, when it seems everyone is only concerned with where the next almighty dollar is comming from, it's phenomenally refreshing to find a place where one can go to find help without expected payback.

Thanks to all

Thanks for the criticizism Randall. I'll make the changes and post it later.

Regards,

Randy

For anyone who is interested this post has been updated. See reply to Randall.

Regards,

Randy

Good Morning Randall and others interested,

I updated Shear Bolt Groove Diameter Calculation.xls and posted to our FTP.

Link to Files

Username: pruser
Password: prpassword

Please see reply to Randall above.

Regards, Randy

Hi randymcdermott,

First I must stress that I have no knowledge in this area or of material properties. However I suggest that you change cell K2 to read

=SQRT((1.288*J2)/87200)

This is actually the same as = 1.288*SQRT((J2/87200)/1.288)

but, I've moved the 1.288 inside the square root and cancelled with the one on the bottom line. OK?

This way if you halve the number of bolts, say, you only multiply the diameter by √2. Or, say, you change the number of cylinders from 2 to 18 you only multiply the bolt diameter by 3.

This is all because the cross sectional area of the bolt is proportional to the square of its diameter.

Hope this makes sense.

You obviously still need to get confirmation of the yield strength of the steel.

OK I think I've got it right now. (posted to the FTP just after you replied Randall)