Go Back OFN Forums > Fabrication > Fabrication 101

Fabrication 101 Everyone has to start somewhere and for some, theOFN might be that somewhere.


Fabrication 101 Everyone has to start somewhere and for some, theOFN might be that somewhere.

Reply
 
Thread Tools
  #1  
Old 09-21-2013, 09:16 AM
and_rej's Avatar
and_rej and_rej is offline
Junior Fabricator
 
Join Date: Sep 2013
Posts: 4
Making Trailing Arm Mount, (First Structural Job), Need Advice

Hi guys,

I'm currently in the process of making new upper trailing arm mounts for my car and need a bit of advice.

I've been welding casually for about a year and have made various bits and pieces, but nothing structural.

The car is a 1985 Nissan Gazelle (not much of an off-roader, sorry :P) and runs a triangulated four link in the rear. The mounts on the chassis are the culprit.

The original mount drew its strength from the floor and from the adjacent chassis rail. I basically want to do the same, but in a simpler way with thicker materials and sturdier mountings.

My major dilemma in this whole thing is trying to figure out how to create a strong enough anchoring point on the chassis.

I know I need a plate on the floor and a plate on the rail to weld to, but I can't figure out how I should attach them.

Should I just weld plates to the floor and rail? Weld all the way around? Stitch weld? Plug weld as well?

How large an area is large enough? The car will be used for circuit work and drifting.

Should I use bolts instead of welding where possible? I can't really do that on the rail because it actually isn't rectangular. It's more trapezoidal. So a plate on either side with crush tubes wouldn't really work.

I'm thinking of using 6mm plate...sound about right?

Here a bunch of pictures to help get an idea of the problem. Any tips at all would be hugely appreciated. Thanks!



















Reply With Quote
  #2  
Old 09-21-2013, 12:51 PM
entropy's Avatar
entropy entropy is offline
Master Fabricator
 
Join Date: Sep 2007
Location: 95-miles from the center of Oregon.
Posts: 8,233
Hello.
In your third picture down (which I have copied and attached) there is a factory plate designed to keep the fastener from pulling through the sheet-metal. They are giving you the answer.
No, you do not want to weld 6mm plate to the I'll guess 2mm Chassis structure, the way that you gain strength is to reinforce the mounting hole area specifically with a 3 or 4mm 'weld washer' of the appropriate size.
Welding technique I'm going to guess that you do not have the factory's spot-welding capability; I would fully perimeter weld AND I would plug weld.
While a Stitch weld might be in-fact 'enough' I would choose the full weld to keep water out of the joint and having the subsequent rust from occurring.

E~
Attached Thumbnails
Click image for larger version

Name:	1219.jpg
Views:	82
Size:	28.1 KB
ID:	7784  
__________________
Oh, never mind...
Reply With Quote
  #3  
Old 09-21-2013, 10:03 PM
and_rej's Avatar
and_rej and_rej is offline
Junior Fabricator
 
Join Date: Sep 2013
Posts: 4
Hi entropy, thanks for the reply.

That would make sense as that bolt is for the rear seatbelt. It should therefore be a very strong mounting, although I'm not sure what crash testing was like in Japan in the 1980s...

I'll keep that in mind though. A friend with a bit more fab experience is coming around today to talk through some ideas. I'll make up some cardboard prototypes to better illustrate my intentions.

In the meantime, with regard to the other things you mentioned:

* I'll be using my MIG for all welding. It's a Cigweld Transmig 175i. I've been using 0.6mm wire as I generally work with thinner materials.
* The floor appears to be 2mm thick or there abouts.
* The rail is made up of multiple layers of roughly 2mm sheet. Seems to be at least two layers thick in most places.
Reply With Quote
  #4  
Old 09-22-2013, 10:56 AM
entropy's Avatar
entropy entropy is offline
Master Fabricator
 
Join Date: Sep 2007
Location: 95-miles from the center of Oregon.
Posts: 8,233
Quote:
Originally Posted by and_rej View Post
Hi entropy, thanks for the reply.

That would make sense as that bolt is for the rear seatbelt. It should therefore be a very strong mounting, although I'm not sure what crash testing was like in Japan in the 1980s...

I'll keep that in mind though. A friend with a bit more fab experience is coming around today to talk through some ideas. I'll make up some cardboard prototypes to better illustrate my intentions.

In the meantime, with regard to the other things you mentioned:

* I'll be using my MIG for all welding. It's a Cigweld Transmig 175i. I've been using 0.6mm wire as I generally work with thinner materials.
* The floor appears to be 2mm thick or there abouts.
* The rail is made up of multiple layers of roughly 2mm sheet. Seems to be at least two layers thick in most places.
Looking forward to what you come up with.
__________________
Oh, never mind...
Reply With Quote
  #5  
Old 10-01-2013, 05:34 AM
and_rej's Avatar
and_rej and_rej is offline
Junior Fabricator
 
Join Date: Sep 2013
Posts: 4
Sorry for the delay, but here's a bit of an update.

I had my brother and his mate over on Saturday. The picture below shows the plating plan pretty crudely, but hopefully it will convey the idea. Still working on those cardboard prototypes...

* Plates will be welded to the floor and side of the chassis rail. The mount itself will be welded to these.
* Only slightly thicker material will be used e.g. 2.5-4mm. Any suggestions on thickness?
* Perimeter welded in. The circles denote plug welds, but I really have no idea on hole size or spacing.
* An identical plate to the floor plate will be added on the interior. This plate can be made larger than the underneath plate if deemed useful.



Also knocked up a little practice piece to get myself back into the swing of welding.

Some stringers on a bit of 2.5mm flat bar:


Some stringers on a bit of 1mm sheet (old BBQ lid):


Close ups of the 2.5mm lapped to the 1mm sheet:




Please be kind. I definitely feel like I need a fair bit more practice before I move to the car, but it felt like progress. A few thoughts:

* Feels like I'm depositing too much in general. Tacks are all way too big. Generally bulbous look. Will try and see if I can get a lower deposition rate going while still feeling hot enough.
* Still having difficulty "finding the arc" after starting. Kind of guessing what's happening for the first second or two while my eyes adjust. I think I'll keep trimming my stick-out for each start and actually resting the wire precisely where I want it to start. Also look for ways to improve seating position and lighting.
* Absolutely no idea how to plug weld :/ The holes were pretty big though ~12mm. Tried to do it in a continuous motion, but really didn't work. I was quite off to the side instead of directly above.

The box for the trailing arm to live in and how it attaches to those plates is a still a work in progress. Quite difficult to draw due to the funny angles involved.

I'll try and get something together ASAP.

Cheers,
Andre.
Reply With Quote
  #6  
Old 10-02-2013, 04:09 PM
Captainfab's Avatar
Captainfab Captainfab is offline
Master Fabricator
 
Join Date: Jan 2006
Location: Coeur d'Alene Idaho
Posts: 2,723
Regarding your welding, what machine do you have? What size wire and what type gas? Are you dragging the weld or pushing it? I prefer to push most of the time in the flat position. Being able to see what is going on is crucial to laying a nice bead. The first thing I would suggest is making sure your cover lenses are clean and clear. If not you might need to relace them. It is amazing how much better you can see with new clear lenses. Also you might need a different shade than what you are using now, and not necessarily lighter. Sometimes a darker shade will allow you to see better.
Reply With Quote
  #7  
Old 10-02-2013, 08:26 PM
and_rej's Avatar
and_rej and_rej is offline
Junior Fabricator
 
Join Date: Sep 2013
Posts: 4
Quote:
Originally Posted by Captainfab View Post
Regarding your welding, what machine do you have? What size wire and what type gas? Are you dragging the weld or pushing it? I prefer to push most of the time in the flat position. Being able to see what is going on is crucial to laying a nice bead. The first thing I would suggest is making sure your cover lenses are clean and clear. If not you might need to relace them. It is amazing how much better you can see with new clear lenses. Also you might need a different shade than what you are using now, and not necessarily lighter. Sometimes a darker shade will allow you to see better.
Hi mate, thanks for the reply. There's a bit of info earlier in the thread, but I'll repeat it here and add some extra details.

* Machine is a Cigweld Transmig 175i.
* Wire size is 0.6mm.
* Gas is a CO2/Argon mix from memory. I explained to the guys when purchasing the machine that I'd be doing mild steel and just got what they recommended. Bear in mind most of these welds are raw, no post clean up at all.
* The pictures contain a mix of pushing and pulling and a variety of settings. Very much a trial and error session. I do prefer pushing for the reason you stated. I also find my beads look better when pushing.
* I really don't know that much about my helmet/hood. The cheapo stick welder I started off with only came with a hand held mask so I just grabbed a middle-of-the-road priced auto darkening helmet and have stuck with that. This is from a chain hardware store mind you, not a welding supply store. I'll see if I can find some specs or post some pics of it. Seems like an important bit of kit so definitely open to upgrading.

In this pic I was pulling on most of the right hand beads and pushing on the lefts hand beads:
Reply With Quote
  #8  
Old 10-05-2013, 12:15 PM
entropy's Avatar
entropy entropy is offline
Master Fabricator
 
Join Date: Sep 2007
Location: 95-miles from the center of Oregon.
Posts: 8,233
Question

Recomend that you slightly increase the voltage and reduce the wire speed.
__________________
Oh, never mind...
Reply With Quote
  #9  
Old 10-05-2013, 06:41 PM
PDANKracing's Avatar
PDANKracing PDANKracing is offline
Master Fabricator
 
Join Date: Jul 2011
Location: Green Bay,WI
Posts: 247
http://www.youtube.com/user/weldingtipsandtricks has some good videos on welding.
Reply With Quote
Reply

Bookmarks


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

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

Forum Jump


All times are GMT -4. The time now is 01:57 PM.

Powered by vBulletin® Version 3.8.0
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Template-Modifications by TMS
Copyright 2012, Offroad Fabrication Network