Can anyone offer advice (such as "don't!") with respect to welding body mounts onto a medium duty truck frame? I've got a long wheelbase FL-70 with a heavy gauge aluminum van body hovering 2 feet above it while I figure out how to attach the body mounts. I cut the original steel body mounts off of the vehicle (a GMC C65) from which I got the van body but am uneasy about welding on the Freightliner's frame.

Thanks,
Timmy

Timmy

DONT weld them on!

try to fab up some BOLT ON body mounts https://www.truckhome.com/infopop/emo.../icon_wink.gif

frame rails are heat treated high strenght steel; the heat of the weld will drasticly reduce the strenght of the rails.

got any pics of the mount? maybe i can give you some ideas https://www.truckhome.com/infopop/emo...icon_smile.gif

btw
here is a pic of how the van bodies are usualy mounted:
https://sandcentral.net/trucks/albums...l_P5070989.jpg

the end of the box is welded to the frame (welding on the end of the frame is "kind of" ok) the rest sits on oak 2x4 strips and is U-bolted to the frame.

hope that helps https://www.truckhome.com/infopop/emo.../icon_wink.gif

....my wreecker bed hinges are welded to the end of the frame[butt welded]....as long as it is at the end and there is nothing behind it-I'd say it's OK....in the middle I say your in for some frame cracking.....BUT....John's Spring Service does it all the time.....shortens and lengthens truck frames while adding an outer "C'' channel to strengthen the the frame.....they do it everyday of the week...If they have had trouble with it I haven't heard about it in the last 7 years......geofkaye

Spooner/Geof,
Sounds like the safe thing is to fabricate bolt-on body mounts, but that doesn't exactly appeal to my lazy side. Would appreciate your input so I'll see if I can post a couple of pictures this weekend.

I should've explained that this box is unlike normal van bodies in that it's 100% aluminum construction -- imagine a huge ambulance body. The front-to-rear strength members are 2" x 3" C channel and are 48" on center which necessitates the body mounts unless you have a better suggestion. The company that built the box apparently had no problem welding body mounts to the stretched (welded seam) C65 frame that I salvaged the box from. This led me to believe that it might be OK to weld with certain manufacturers.

Frame manufacturers will void a warantee if you weld to, cut or drill the flange of the frame. This is because the flange provides the bulk of the strength of the frame. Heat from welding can destroy the temper and cause fishers/fractures which will destroy the integrity of the frame. Cutting and drilling not only removes metal but also introduces excessive heat.
The welded seam on the stretch is different in that you have 2 butt joints being welded together and then re-enforced by doubling the frame in that section.
Welding the vertical portion of the frame is discouraged as well. It can be done but should only be attempted by someone with a great deal of experience. Steel is a good conductor of heat and you can still damage the temper, even in the flanges, when welding to the body of the frame.
I'd suggest following spooners advice and using U-bolts.

Aren't steel and Aluminium not compatible over time... As I recall they don't like each other, so you would want a wooden beam or something in between the body and frame, so U-bolts would be the best route

timmyt
hmmmm.....sounds like a interesting body.
was the body solid mounted or on rubber pucks?

....in the pix it is a wood seperator....I have seen a type of white plastic block-but only on a moving rail system...with grease or something...I have never seen a puck but I haven't looked either.....airport lifter bodies sit on a large rubber foot front and rear and are held in place by hydraulic force and mechanical locks......whoever invented those freaks had to be using drugs....I've personally wrecked 3.....and I don't have the record......YET.....geofkaye

Spooner,
The body was attached with 1/2" bolts and 1/4" thick rubber spacers between the steel body mounts and the aluminum rails on the box. The body mounts were outboard the frame rails but there was still wood between the frame rails and box floor. (Camping Dutchman, my guess is that these two together was enough to keep the corrosion problem at a minimum?) Unless I make serious changes to the box I can't see how U-bolts would work. Here's the overdue picture -- if you look closely you can see some of the bolts sticking down still have their rubber spacers:

[img]https://groups.msn.com/_Secure/0QgCfAiISCDJQ6yzmyq!zuvfPCHVeAQQ!J*7cgzTnmkkZUXWgN cprVpRWI*Emo89frsYeEw38LWt1n2cpVa42I9AvPPgp7ZCCbA1 TYXwFuKA/BB40051.JPG?dc=4675528317683635909[/img]

....timmyt: That is a new one for me...what is this box off of?......If it is a fire departmant vehicle I have a relative from my "extended family" that sells/repairs Seagrave and has worked on Seagrave trucks for 25 years.....If it is Fire related-he knows all about it-vehicle wise....send some more more info or pix and I'll send it to him and get you an answer the next day.....He's one of those kinda guys that lives fire trucks and fire equipment....geofkaye

https://www.truckconversion.net/photopost...B40051-med.JPG

"....replace with stainless bolts and brass locking nuts use a brass lockwasher.....you aren't going to have any corrosion".....I should have known this because my aluminum airboat has stainless nuts with brass washers and nuts....duh!.......one kinda cancels out the other-even in salt water.....geofkaye