Reply
 
Thread Tools Search this Thread Display Modes
 
Old 02-29-2016, 06:47 PM   #15
Rivet Master
 
2015 25' Flying Cloud
2016 30' Flying Cloud
Blenheim Ontario , Ontario
Join Date: May 2015
Posts: 1,264
Quote:
Originally Posted by JCWDCW View Post
Quote< "BTW - If your hitch bolts hafta be re-torqued, it's because they've stretched. And once stretched, they shouldn't be reused. Even grade 8 head bolts on certain motors will stretch, and as a consequence, they hafta be replaced." >

I think the OPs point was that he had re-torqued twice while trying the zero in the adjustment, not that they had loosened off.
I believe the bolts have Belleville Washers which are dished to provide continual resistance to overcome metal creep. The bolts are usually stable but washers tend to be soft unless matched to the bolt service, and continual working will even eventually cause the metal in the hitch head to creep thus requiring a re-torque once in a while.

I had loose fittings everywhere on my hitch head after a trip to Louisiana. Had them re-tightened using an impact wrench at an RV shop. I never had that problem again in 8 years.
JCW
AN IMPACT GUN?????
YIKES, ARE YOU NUTS???
An impact gun has the accuracy of a pile driver powered by a C-4 charge!
Let us know when you're going down the 401, so that I can be far behind you.
"I'd rather be an interested spectator, than an active participant"!
__________________

__________________
MelGoddard is offline   Reply With Quote
Old 02-29-2016, 06:54 PM   #16
Rivet Master
 
2015 25' Flying Cloud
2016 30' Flying Cloud
Blenheim Ontario , Ontario
Join Date: May 2015
Posts: 1,264
Quote:
Originally Posted by J. Morgan View Post
To the greatest extent, the only bolts that cant be tightened over and over and over are torque to yield bolts which would not be used in this application.


Talis gentium ceciderunt.
And where does one FIND "Torque to yield bolts"??????
__________________

__________________
MelGoddard is offline   Reply With Quote
Old 02-29-2016, 07:12 PM   #17
Rivet Master
 
2015 25' Flying Cloud
2016 30' Flying Cloud
Blenheim Ontario , Ontario
Join Date: May 2015
Posts: 1,264
Quote:
Originally Posted by nvestysly View Post
I wouldn't hesitate to tighten - loosen - tighten your screws numerous times. I've done it on our hitch a dozen times. I did it again recently when we installed new axles on the trailer and the tongue height and hitch needed to be adjusted.

Take a look at the information on the table shown HERE.

I presume you have grade 8 bolts, that's what I have and I would expect hitches to come with that hardware. The bolts on my hitch are 3/4" diameter (1-1/8 hex). The clamp load in the chart is just over 30,000 pounds!

The chart shows the torque for various friction factors of K=0.15, 0.18 and 0.20. The torque ranges from 282 - 376 LB-FT depending on the friction factor. Back when I was designing bolted joints I typically used K=0.20 as an approximation but the friction does vary depending on the material and plating. Regardless, the clamping load is intended to make the bolt act like a large rubber band - extending the bolt within it's yield curve as the nut is tightened and then returning to it's original length when the nut is loosened.

I wouldn't tighten and loosen indefinitely but a few times doesn't seem like a problem in my mind.
-If you remember Premier Fastener Corp. Of Euclid Ave. in Cleveland, they demonstrated, using a torque/tension tester, that the nuts should be replaced every time they were torqued to the usual 70% of the UTS.
If not, and retorqued, you would loose about 20% of your tension using the same torque.
I was an agent for Premier, and using a t/tester, a 3/8" Supertanium fastener assy.; 60 lb. ft. of torque would give us about 10,500 lbs. of tension. This was with a dry, plated assy., f/f of .18.
By loosening and retightening the nuts, we would read about 8,500 tension. Quite a drop.
Me? I replace my OEM Grade 5 bolts/nuts with Grade 8 bolts, nuts and washers, and torque them to the hitch mfr's spec of Grade 5 bolts.
That way, I'm not working the nuts to full load, and can retorque them as required.
Unfortunately, Premier seems to be out of business, in Canada, and so Supertanium bolts [220 KSI] are no longer available.
I have used Aircraft MS-21250 bolts. [220 KSI] and DSC-97 nuts in the past, but now am retired, and no longer able to access them.
__________________
MelGoddard is offline   Reply With Quote
Old 02-29-2016, 07:19 PM   #18
Rivet Master

 
Southwestern , Ohio
Join Date: Nov 2006
Posts: 1,669
Quote:
Originally Posted by MelGoddard View Post
And where does one FIND "Torque to yield bolts"??????
I think you used to be able to get them from the company that made special-purpose fasteners like those shown below. But I'm not sure if they're still in business.
Attached Thumbnails
Click image for larger version

Name:	special_bolts.jpg
Views:	60
Size:	126.0 KB
ID:	258003  
__________________
Nuvite-F is offline   Reply With Quote
Old 02-29-2016, 08:14 PM   #19
Rivet Master
 
J. Morgan's Avatar

 
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton , Arkansas
Join Date: Mar 2013
Posts: 5,040
Images: 11
How many times can the hitch head bolts be torqued?

Quote:
Originally Posted by MelGoddard View Post
And where does one FIND "Torque to yield bolts"??????

Mostly they are used for modern engine head bolts.

Use them once and throw them away.


Talis gentium ceciderunt.
__________________
The fact that I am opinionated does not presuppose that I am wrong......

J. Morgan is offline   Reply With Quote
Old 02-29-2016, 08:22 PM   #20
Rivet Master
 
J. Morgan's Avatar

 
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton , Arkansas
Join Date: Mar 2013
Posts: 5,040
Images: 11
How many times can the hitch head bolts be torqued?

The other modern style of fastener use is "torque angle".

Torque to a specified torque value and then advance the fastener a certain number of degrees irregardless of torque value.

This is commonly used on engine main bearing caps, connecting rod caps, etc. these fasteners can be used over and over.

I have a cool torque wrench that has gyroscopes in it for torque angle and torque to yield fasteners which are tightened in the same manner as torque angle fasteners.

Torque to yield fasteners are designed to be stretched a certain amount, ONCE, and only once. The advancement of the fastener a certain number of degrees stretches the fastener a specified amount.

Talis gentium ceciderunt.
__________________
The fact that I am opinionated does not presuppose that I am wrong......

J. Morgan is offline   Reply With Quote
Old 03-01-2016, 01:35 PM   #21
Rivet Master
 
1996 25' Excella
Tillsonburg , Ontario
Join Date: Aug 2014
Posts: 787
Quote:
Originally Posted by MelGoddard View Post
AN IMPACT GUN?????
YIKES, ARE YOU NUTS???
An impact gun has the accuracy of a pile driver powered by a C-4 charge!
Let us know when you're going down the 401, so that I can be far behind you.
"I'd rather be an interested spectator, than an active participant"!
Oh come on! It was a reputable RV dealership.
Garages use impact guns to tighten wheel nuts all the time. They can be set for a reasonably close torque. And as noted Grade 8 bolts can take a lot more than 250 ft lbs torque. And apparently the setting was good because that set up is still on the road 12 years later.
JCW
__________________
JCWDCW is offline   Reply With Quote
Old 03-03-2016, 12:03 AM   #22
Rivet Master
 
J. Morgan's Avatar

 
1972 31' Sovereign
1975 31' Excella 500
Currently Looking...
Benton , Arkansas
Join Date: Mar 2013
Posts: 5,040
Images: 11
How many times can the hitch head bolts be torqued?

A 3/4" coarse thread grade 8 bolt is rated to 376 foot pounds, a fine thread to 420 foot pounds. I doubt a 1/2" impact gun that is used with any care at all is going to be an issue.

Besides, the owner has 12 years of empirical evidence that says it was cool.


Talis gentium ceciderunt.
__________________
The fact that I am opinionated does not presuppose that I am wrong......

J. Morgan is offline   Reply With Quote
Old 03-03-2016, 12:40 AM   #23
Rivet Master
 
ROBERTSUNRUS's Avatar

 
2005 25' Safari
Salem , Oregon
Join Date: Mar 2006
Posts: 7,266
Images: 18
Blog Entries: 51
How many times can hitch head bolts be torqued?

Quote:
Originally Posted by RFP View Post
In the process of setting up our Reese SC hitch, I have made several adjustments (and readjustments!) to get it 'dialed in' correctly... many of you are already so familiar with this exercise.

In the process, I have twice fully torqued the two main hitch-head-to-shank bolts to the full torque spec (250 ft. lbs.), and dang, that's tight.

Knowing next to nothing about the 'mechanical engineering' aspects of all this, I'm wondering if repeated (twice) torquing to this spec has compromised the bolts' integrity in any way.

Should I replace the bolts with new, or should I just use the ones I have and go and worry about something else?

Thanks,

Rob
Hi, how long is a piece of string?????? You can torque bolts as many times as it takes before one breaks. I changed all of my hitch bolts to grade eight.
__________________

__________________
Bob

2005 Safari 25-B
"Le Petit Chateau Argent"
[ Small Silver Castle ]
2000 Navigator / 2014 F-150 Eco-Boost / Equal-i-zer / P-3
YAMAHA 2400 / AIR #12144
ROBERTSUNRUS is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
1973 Airstream Land Yacht Sovereign -- Many Many Many Upgrades!!! eBay Watch Airstreams on eBay 0 06-18-2013 07:30 PM
How many times have you used the spare tire? adonh Tires 75 05-14-2013 06:57 PM
How Many times per year? Mainstream Community Polls 10 05-12-2009 08:50 PM
OT: How many trailers is too many? Amazing short video. SilvrSausage On The Road... 1 09-10-2008 05:44 PM
How many times have you hit... drboyd Interior Restoration Forum 29 11-30-2003 05:19 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 06:26 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.