• Spring 2024 meetup in Calgary - tentative date Saturday, April 20/2024. Other regions are also discussing meet ups. If you want one in your area get going on organizing it! discussion
  • We are having email/registration problems again. Diagnosis is underway. New users sorry if you are having trouble getting registered. We are exploring different options to get registered. Contact the forum via another member or on facebook if you're stuck. Update -> we think it is fixed. Let us know if not.
  • Spring meet up in Ontario, April 6/2024. NEW LOCATION See Post #31 Discussion NEW LOCATION

Aluminum Welding Questions

whydontu

I Tried, It Broke
Premium Member
My welding skills would be 0.3 out of ten, but my business partner has asked me if I can help him with a small project. After upgrading his 36ft speedboat to twin 300HP Yamaha outboards, the attachment post for water skiers no longer clears the top of the outboards. (I know, the horror of first-world problems.)

The request is to increase the distance between the two cross arms and the plate. The plate attaches to the top surface of the transom. The cross arms need to be 12” farther away to clear the outboards. The open end away from the cross arms is drilled and tapped in two places to bolt to a couple of angle brackets below the transom. The top is capped off with a 1/2” thick plate.

The problem is the post is bizarre. It’s fabricated from two pieces of aluminum pipe - 2” Sch40 sleeved inside 2-1/2” Sch40. The two pieces of pipe are welded at each end, with the cross arm as a single piece of 1” aluminum bar welded to the outside of the 2-1/2” pipe. So I can’t just cut and weld in a section, because it’s impossible to weld the inner pipe.

I‘m about 90% sure the manufacturer made up this kluge so they would have enough wall thickness to drill and tap, my math says adding the inner 2” pipe doesn‘t provide much extra strength.

So - try to cut it apart and do a multi-step staggered weld, or cut off the plate and just buy two new pieces of pipe and make a whole new post? 6DCC5F78-57BD-48CC-81F9-781984ABBE9F.jpeg
 

Attachments

  • 0595FA7E-B669-44BD-A29C-CDB30F62CC63.jpeg
    0595FA7E-B669-44BD-A29C-CDB30F62CC63.jpeg
    468.9 KB · Views: 13
  • F9F523A5-50A5-410C-A5BF-6BCA5E91598A.jpeg
    F9F523A5-50A5-410C-A5BF-6BCA5E91598A.jpeg
    241.3 KB · Views: 13
  • F8E8F3CC-4652-4D56-80CA-4053131ED819.jpeg
    F8E8F3CC-4652-4D56-80CA-4053131ED819.jpeg
    313.6 KB · Views: 13
  • 12AF19DB-3EFB-4B39-90A3-8B489138FC81.jpeg
    12AF19DB-3EFB-4B39-90A3-8B489138FC81.jpeg
    151 KB · Views: 12

phaxtris

(Ryan)
Premium Member
Premium Member
@Aliva has a good suggestion

My question is what are you going to be welding this with ? 1" plate, 1/2 plate, sched 80 pipe....that all takes mega amps for aluminum, a 200a machine isnt going to cut it without some big time preheat
 

LenVW

Process Machinery Designer
Premium Member
I suggest buy a new 2" schedule 80 pipe and make new post, No farting around with different size pipes.
Start with a hefty 2” Schedule 80 pipe.
I would agree that preheating would be required for the fusion process.

I would like to hear from current TIG welders.
It has been years since I had any aluminum welding done.
There must have been vast improvements in processes and welders.
 

phaxtris

(Ryan)
Premium Member
Premium Member
i missed that the original od pipe was 2.5.....you should keep it at a 2.5" pipe at least, esp considering you would loose wall thickness by going with one pipe over the original two

you are absolutely going to be right to the floor with a 200a machine, 2.5 sched 80 is .276" thick, you will almost certainly require preheat...youll see

@LenVW the only real changes in the last 20 years is that they no longer recommend pure tungsten for aluminum, and inverters are more common (frequency control). Pulse, balance control, that has all be around for 20+ years, dynasty's are still the top machine (big buck inverter). Syncrowaves are still produced and i would say still more popular because of the huge price gap between a 400a transformer and a 400a ac inverter....if you knew how to tig aluminum 20 years ago you havent missed anything
 
Start with a hefty 2” Schedule 80 pipe.
I would agree that preheating would be required for the fusion process.

I would like to hear from current TIG welders.
It has been years since I had any aluminum welding done.
There must have been vast improvements in processes and welders.
Good prep and Argon.
 

LenVW

Process Machinery Designer
Premium Member
i missed that the original od pipe was 2.5.....you should keep it at a 2.5" pipe at least, esp considering you would loose wall thickness by going with one pipe over the original two

you are absolutely going to be right to the floor with a 200a machine, 2.5 sched 80 is .276" thick, you will almost certainly require preheat...youll see

@LenVW the only real changes in the last 20 years is that they no longer recommend pure tungsten for aluminum, and inverters are more common (frequency control). Pulse, balance control, that has all be around for 20+ years, dynasty's are still the top machine (big buck inverter). Syncrowaves are still produced and i would say still more popular because of the huge price gap between a 400a transformer and a 400a ac inverter....if you knew how to tig aluminum 20 years ago you havent missed anything
Ryan,
20 years ago, I was designing moulds for vacuum formed HDPE pipe. We had to sand cast huge blocks with excess aluminum in places where we machined reference points that we needed to mount the blocks to the apparatus.

I had experimented with ‘fabricated’ moulds made from 6061 plate and extruded profiles.
The idea was never developed due to a changes in priorities and the sale of the company.

Do you have experience TIG welding large (3/4” thick) plates into sealed 6 sided boxes ?
Would welding the boxes (48”H x 20”D x 18” W) take a long time to TIG weld with 1/2” fillet welds at the corners with common welders these days ?
 

phaxtris

(Ryan)
Premium Member
Premium Member
Do you have experience TIG welding large (3/4” thick) plates into sealed 6 sided boxes ?
Would welding the boxes (48”H x 20”D x 18” W) take a long time to TIG weld with 1/2” fillet welds at the corners with common welders these days ?

Yes, I have welded thick sections, 5/8 wall pipe with Tig the thickest that comes to mind. I can't say how long for sure without having an idea of how many inches of weld that is, but I would wager *if* you could find someone to do it with a tig your going to pay for a full day for sure if not two. Most guys are going to steer you towards MIG for that thickness of plate and that size of weld, faster and less warpage. Should be no concern of leakage, it's going take 3 passes anyways, MIG is really what a guy should use for that thickness and weld size
 

LenVW

Process Machinery Designer
Premium Member
Yeah I was figuring on 3 passes per joint and MIG would best for the amount of wire used.
The advantage I was trying to ‘push’ through the design team was the fact that all the fabrication materials would be virtually void of porosity that can be produced when pouring is sand castings.
Thanks for your estimated welding time.
 

whydontu

I Tried, It Broke
Premium Member
I'm sorry, I can't get past wondering how you call anything 36ft long a speed boat.
I know nothing about boats, just that it’s insanely fast. It’s 36ft long, maybe 7ft wide, and it’s fricking uncomfortable to be on it going 60 knots into pouring rain. First trip my favorite ball cap got whisked off my head about 20 seconds after partner cracked open the throttle, followed about 20 seconds later by the forward hatch whooshing out into the Salish Sea. Oops, forgot to tighten it down.
 
Top