Most buildings and bridges nowdays are field assembled with bolts. When I
worked for USS, we had a lot of general rules for welding on structural
shapes, most of which would apply to cars. The basic one was to never weld
across the member, always weld the long way. The reason is that you often
can't control sharp points, pits, slag inclusions, or welds where some of
the parent metal was taken up into the bead, leaving a hollow area of
reduced thickness. These are all areas where cracks can start. If welded
lengthways, the cracks are less likely to propogate to the edge of the
member and will not make it fail.
Proper strength bolts in drilled holes with sufficient metal around them
are very unlikely to crack or start cracks. The main problem is to torque
the bolt up tight enough to lock the two metal pieces together. You can
use tricks like cupped washers or you can just tighten them up a few times
after they break in You can also use things like lock nuts, loktite,
cotter pins, and fine threads to help keep a bolt from coming loose.
If two pieces of clean metal are joined together with properly strong bolts
(those hash marks on the heads aren't just to make them look pretty) in
reasonably tight holes, the joint will not come apart on its own. Loktite,
lock washers, and lock bolts are just insurance against problems.
Another interesting thing, say the torque on a joint puts 500 pounds of
tensile stress on a bolt joining two pieces of metal together. If you pull
the two pieces of metal apart, the stress in the bolt will not increase
until you are pulling with more than 500 pounds of force. An example would
be the head bolts in an engine. Because there are a lot of bolts and they
are torqued very tightly, there is no more tensile stress on the bolts when
the engine is running than when it is stopped hot, and there is more stress
when it is cold and the bolt has shrunk.
In a properly designed joint, the bolts only hold things together anyways.
The two pieces of steel are arranged so that the real force is transmitted
by the overlapping metal. In short, I have no problem trusting my life to
a proper bolted joint. We all do it every day.
Bruce Kettunen
57 3200
Mt. Iron, MN
>A certified welder will rarely have his welds crack. More often it's the
>surrounding metal that will give first.
>
>As far as trailer hitches are concerned, the main reason they're bolted on
>is because it's easier and cheaper to sell them that way. They are also
>not subjected to the same stress as IFS systems. There's a big difference
>between occasionally having to support the weight and sheer stresses that
>a trailer creates than having to constantly put up with every little bump
>in the road and twist of the frame like your suspension system does.
>
>Cotter pins and/or Locktite can be used and would definitely help, but how
>many people do you think actually use those techniques when installing a
>bolt on aftermarket IFS system? Not one in a hundred would be a safe bet.
>
>Bill Whittaker
>'53 3100 Hemi
>Built Like A Rock
>With Mopar Stock
>
>
>-----Original Message-----
>From: Grant Galbraith [mailto:trks@javanet.com]
>Sent: Friday, September 15, 2000 11:19 AM
>To: Whittaker Bill G Civ ASC/SMY
>Cc: 'Old Trucks'
>Subject: Re: [oletrucks] RE: IFS, but not to open any can or worms again
>
>
>I'm not sure that welds hold up better than bolts to stress and vibration.
>Welds crack. Isn't this why trailer hitches are bolted on rather than
>welded. They are many critical bolts in front suspension's. They can be
>drilled for cotter pins or loctited.
>
>Grant
>50 Chevy 3100
>52 GMC 150
>
>> Flexing and vibration are the two major culprits that loosen bolts,
>>and they don't discriminate as to which bolts !
>>
>>
>> Bill Whittaker
>> '53 3100 Hemi
>> Built Like A Rock
>> With Mopar Stock
>>
>> -----Original Message-----
>> From: Brian _ [mailto:pkupman57@hotmail.com]
>> Sent: Thursday, September 14, 2000 6:53 PM
>> To: ryan_border@hp.com; oletrucks@autox.team.net
>> Subject: RE: [oletrucks] RE: IFS, but not to open any can or worms again
>>
>> list,
>> i work for the ford dealer in town. ive changed several engines in vehicles
>> and most all FWD cars and vans use a bolt on front sub frame. the ford
>> windstar for example, uses 4 bolts to hold the front sub frame, engine,
>> suspension, steering, tranny, everything onto theh body. makes it EZ to
>> change engines tho, as you only undo 4 bolts, brake lines, and steering and
>> shift linkage, and the whole shabang drops out from under the van. so i dont
>> believe that the majority of bolt on front suspensions are unsafe.
>> Brian M
>> Atwater, CA
>> '57 Chevy 3200
>> _________________________________________________________________________
>>
>> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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