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A sole plate with jack bolts that allow screws to block the bearing ends would minimize your need for a friction
force to hold the bearing in place.
Mike Halloran
Pembroke Pines, FL, USA
ldeem (Structural)
(OP)
24 Dec 17 22:08
Mike,
This is a one-off structure and there are only three bearing I need to do calculations on. So its not to time
consuming. However, you have a good point if they just torqued to the usual values there would be more than
sufficient clamping force.
Unfortunately, on the larger 1.5” bolts the contractor wasn’t sure they could meet the 1,950 ft-lbs torque for
dry threads.
dvd
Thank you for the reference to sole plates. The web site link looks very interesting and has a lot of useful
content.
In this application I have designed the jack bolts for the full horizontal load. My goal is to design the friction
force for the full load as well so in combination it will be a very robust joint.
I am curious if you normally specify machined sole plates to be tack welded to the mounting flange? I thought
about this but assumed a plate would distort to the match the flatness of the mating beam flange. I have also
seen many places where 1/2" sole plates have been fully welded to the beam flange. I had a situation similar
to this on a large flui
tbuelna (Aerospace)24 Dec 17 00:52
What you have is similar to a slip-critical bolted connection. There are standard analysis approaches for slip-
critical connections used in aerospace, structural steel construction, etc. Here is a example of an analysis
approach used for structural steel bolted connections that should work for your case. There is a reference
noted in the document for faying surface characteristics, including static friction coefficient.
Hope that helps.
Terry
dvd (Mechanical)24 Dec 17 03:22
A sole plate with jack bolts that allow screws to block the bearing ends would minimize your need for a friction
force to hold the bearing in place.
Have a look at this - Sole Plates, and this, Soles Plates 2. Additionally, if you could mount your bearings so
that the belt reaction forces were borne by the support members, you could remove the shear on the bearing
bolts.
ldeem (Structural)
(OP)
24 Dec 17 14:38
tbuelna
Thank you for the reference to slip critical design. I am familiar with this approach which is similar to what I
am doing. The trouble I have is the slip coefficient from cast iron bearing housing to HDG is hard to find.
MikeHalloran (Mechanical)25 Dec 17 05:10
For big threads, take a look at SuperBolt nuts.
Mike Halloran
Pembroke Pines, FL, USA
Tmoose (Mechanical)25 Dec 17 16:44
I think the contractor should rent/borrow/buy a torque multiplier.
1950 lbs-ft sounds like about a grade 5 bolt.
tbuelna (Aerospace)26 Dec 17 04:33
Ideem-
Chapter 12 of this reference might provide some answers to your question regarding slip coefficient of HDG
surfaces.
Best regards,
Terry
ldeem (Structural)
(OP)
27 Dec 17 17:30
Thank you everyone for your help on this issue.
Tmoose (Mechanical)27 Dec 17 17:37
If space permits, an 8 foot long pipe/cheater bar plus this $75 scale and I'd be good to go.
https://www.mcmaster.com/#1756t5/=1av9bni
Might take a come-along etc rigged to a perpendicular location to be able to exert ~250 lb force out at the 8
foot mark.
Similarly, welding some 1" drive sockets. etc to the pipe would permit using a 250 ft-lb torque wrench
according to this formula.
https://www.norbar.com/en-gb/Home/Torque-Wrench-Ex...
==========
If space at the actual installation is a problem, then one of the rigs above could be used to develop a
reasonable turn-of-the-nut spec out in the open where it is convenient in about 15 minutes.
=============
The typical torque indicating washer (A325 or A490) is likely to be rated for a service a little higher than yours,
but I only looked at a few suppliers on-line.
