Mig welding Aluminum plate to cast Al

[DougM]

Hey guys.
I’ve searched high and low all over the web for mig or tig welding Al plate to cast Al. No joy. So this forum is one of my last resorts.

The Task:
Fabricate a high-speed, relatively low-tension winch spool from a cast aluminum scooter wheel and 0.25” thick Al plate sides.

The unit will be used as a stationary winch for ground-launching hang gliders and ultralight sailplanes. The tow-line spool must fit within the confines of the scooter’s trailing arms (a direct substitution for the wheel / tire). The donor scooter is a Yamaha Majesty 400cc scooter, and it’s engine and drivetrain, electronics, cooling system, etc, will be exhumed from the chassis and installed within a purpose-built steel frame. Tow line will be Samson 7/64” Dyneema line of 6400 ft in length. Calculations indicate that this line will easily fit within a spool of 5” inches internal width with an inner diameter of 13” (tire seating diameter) and an outer diameter of 22”, with an inch of radius to spare, wound on with zero tension.
Lines speeds that will be generated by this scooter winch will be normally 20-25 mph @ a max of 300 lbf tension while towing, and 60-70 mph @ ~200 lbf tension while reeling in line after glider release.
The spool’s side plates must withstand much bending moment created by the many layers of high-tension, low surface friction (slippery) line. How much bending moment is hard to calculate due to very scarce literature available on it’s larger cousins. Any data is mostly proprietary property of the large winch manufacturers.

Hopefully that abbreviated description fulfills your curiosity as for the project’s requirements. Here’s a vid that shows a slightly more powerful scooter winch doing it’s thing: https://www.youtube.com/watch?v=mnS_jTl-JYw

I have a well used, well tested Millermatic 251 with a Spoolmatic 30a. Though I have never used the spool gun or tried my hand at aluminum-anything, I can run nice looking, good performing welds in steel.

Others have done similar fabs for their scooter winches, but none of the garage-built winch builders are weldors, and haven’t given me solid details to ensure longevity and safety. One experienced tow pilot/instructor indicated that he used 0.25” 6061-T6 plate with lap joints to a cast Al wheel, but had a friend in the aerospace industry weld it for him (TIG).

Lap vs Butt joints:
The task that I’m needing your expertise in is to point me toward the best practices to weld aluminum plate material (side plates) onto the cast aluminum wheel rim with lap joints, or perhaps butts.
For lap joints, the two disk-shaped side plates need to be at least 0.25” thick, inside diameter is ~12.5”, outside diameter is 22”. The inside plate diameter is chosen to provide clearance for the disk brake caliper as well as ease in welding the lap joint to the rim. If using butt joints, the inside diameter of the side plates would be roughly 14.25” and be welded to the rim lips after appropriate prep, however the interior spool width would be at least 0.5” less compared to if it had lap joints.

Also, I am thinking of trimming down (reducing the max radius of) the rim lips from the wheel, as they splay out axially from the rim so that a flat plate will not lay flat across their whole surface (the intersection of outermost rim lip edge and disk plate would be only a very thin circle). Either that or grinding the exterior or building them up to create the proper, axially-flat faying surface. This is supposing that I will weld lap joints rather than butt joints. Lap joints will give me more internal spool width, and that is the goal. Is there any ideas about the strength differences between lap and butt joints for plate welded to cast?

Al Plate Series:
So Maxal has a guide that provides some good info on MIG/TIG welding Al plate (http://www.maxal.com/files/quicksite...g_6-11_doc.pdf), but little for cast.
From their guide, it would appear that 5083-H32 retains it’s strength far better than 6061-T6 (AW, no PWA). 5356 filler is suggested, and 4xxx series is firmly not suggested.
Many other sources suggest welding cast Al with 4043 or 4047, as 4047 has a lower melting point. As I understand, 5083 has a high magnesium content, and to use a low Mg-content filler is not suggested for 5xxx series base materials.
As 6061 has a lower Mg content (< 2.5%), fillers 4043 or 4047 are indicated to be ok, though the AW tensile strength would be much less than 5083, if 5083 could be welded successfully to the cast stuff. I do not know if the cast wheel / 6061 side plate weldment would warp with PWA to T4 or T6. PWA would have to be outsourced.
I have little idea as to the composition of my cast wheel, though it appears to be anodized with a clear-coat.

Preheating:
After all the normal surface prepping, should I ensure the cast wheel is fully pre-heated to avoid the inevitable weld-heat problems, and what is the recommended temperature? Is a propane heater out of the question for the very real possibility of carbon soot deposits?

I could be all wet in my reasoning, so please correct me if I am ( please support your arguments with reasoning).

This is my vid of towing on a 250cc scooter. Could only manage about 600 ft maximum altitude gain with the small engine’s lower output power and roughly 2500 ft of line to the turning block, 5000 ft of line total: https://www.youtube.com/watch?v=FWAiSDa92Wo

Yeah, this post looks like it should go into the projects forum, but since it has to do with a method not addressed previously, I thought it would be better suited in Welding Discussions. I could be wrong.

Thanks
-doug

[shovelon]

You are thinking too hard. 4943 filler is your friend.

[WillieB]

Shovelon is a man of few words. After cleaning super thoroughly, cook the surface of your cast a bit . Once able to puddle, coat the face with 4943. Then it is as welding any solid aluminum.

[topgunner]

Shovelon is a man of few words. After cleaning super thoroughly, cook the surface of your cast a bit . Once able to puddle, coat the face with 4943. Then it is as welding any solid aluminum.

Good reference Willie.

[Anarchy61187]

First time... Get plenty of tips for the gun!
keep a longer stick out, about an inch. 100% argon, no mix, aluminum likes hot and fast. Grab some scrap and have fun

[DougM]

Shovelon is a man of few words. After cleaning super thoroughly, cook the surface of your cast a bit . Once able to puddle, coat the face with 4943. Then it is as welding any solid aluminum.

Ok.... color me stupid, but I've never ever heard of 4943 filler. I'm guessing all you guys are trying to test me here.... do ya mean 4043?

Also, you say "Once able to puddle..." and I'm again guessing that you are referring here to TIG welding practices. I wish I had a decent TIG machine, but I don't yet. But I do have a spool gun and I'm fixin' to spray that sucker. Or so I think.
So, correct me if I am back-ashwards in interpreting your post, you are saying I should spray the cast surface with 4043 first, then mill it to a flat surface, and then spray in fillets for the lap joints?
Thanks in advance
-doug

Ah ha! Finally found 4943 filler. http://www.maxal.com/4943_datasheet.pdf
Thanks much! That saved my ash!
But please, still enlighten my ignorant self about pre-coating the surface with MIG.

[Anarchy61187]

As far as welding on/to cast aluminum goes I don't have much info there, haven't done it yet. I have run a spool gun and can tell you from first experience, expect to melt tips. A general rule of thumb is do not practice on your project. I'd stop by the junk yard and get an old rim to practice with that way you can try different methods, voltage and wire speeds to see what works best for what you are trying to fabricate. It will save you from trashing the good material if you just go at it blind. If weld strength is really a big concern, keep track of what weld parameters you had for each joint and do the cut, polish, etch test and roll with what turned out best.

[ryanjones2150]

Glad you found it. I'm glad I found it a while back too.

"Pre-coating"....not really sure. Unless you're asking if you should run a pass on your cast piece to cook the schmoo out before you attempt to join two pieces. If that's the case, I agree. I do it with tig when welding cast aluminum.

I honestly didn't read your whole first post because I have the attention span of a.....

Don't be afraid to weld cast. Sometimes it drives you batty, other times it welds excellently. Give it a go.

[DougM]

Thanks Anarchy... Just as you suggest, I have planned on purchasing a junk cast rim and some scrap plate and playing with that until good and ready. I have pure Argon that I mix with CO2 for my ferrous welding tasks, so I'm good to go there.
Just plugged in the spool gun and gave her a whirl without power, and discovered the drive roll has quite a bit of run-out. Haven't taken the drive roll off yet, but perhaps the shaft is bent, or the drive roll is not centered properly due to the two set screws. Don't know yet.

I'm figuring 0.047" wire should be appropriate for the base material thickness.
Thanks

[DougM]

Thanks Ryan, yeah, I figured that post was gonna be a drag. Thanks for all the info.

[Red Seal Tech]

I'm guessing pre-coating is the same as cladding. In essence you are adding a layer of the filler metal to the surface of the cast which acts like a middle layer where a dilution of the cast and the 'softer' filler makes the welding to the plate material a little easier.

Not knowing the metallurgy of the scooter wheel makes an accurate filler selection a little dicey. However, in a general sense, aluminum rims are an aluminum / magnesium alloy which means that a 5xxx series filler and plate would be your best bet.

With that in mind, if it were me (and it's not, so take it as my own 2p) I'd go with a 5356 filler and 5083 plate. Both common, off the shelf items.

Make sure you clean the rim thoroughly and wire brush it with a stainless steel brush only. Any oxidation or clearcoat will contaminate the weld area and makes for a messy result.

As far as welding, the parameters I have certified for are 24v 250a with 5356 .045 wire, 100%argon at 25 cfh. I preheat to 70*c (150*f) and don't let my interpass temp go above 140*c. That's using an XR 30 and an XMT 350.

The interpass isn't as big a deal with 5xxx material as it's not heat treatable. I'm just a little more cautious out of habit.

[DougM]

Thank you Red. Excellent information. I was thinking in similar circles about the Mg content of the cast Al after reading a bit more. Thanks for reinforcing that. I may not weld the side plates directly to the rim lips, rather cut off the rim lips all the way to the rim, then have some 0.25" plate that is 1" wider than the rim, rolled to the diameter of the rim, weld the rolled part seam while on the rim, weld the side plates to the rolled part, then align, tack, and weld the rim to the new rim/plate weldment. May be a bit heavier and have more rotational moment, but then the side plates would be welded to same material, with a better known strength.
Thanks
-doug

[FusionKing]

Doug,
If you clean the wheel up, and then turn it to the proper shape, facing all welding surfaces, then it will weld like a dream. Providing it is standard cast material without zinc.
5083 plate is going to be a bit hard for you to find unless you are near the coast. It is a salt water alloy as is 5086. both are very hard. And expensive.
Locally you will likely find 3003 or 5052.
3003 is cheaper than 5052 but 5052 is harder. 5052 is reasonable and good to work with. 6061 will loose most all of it's temper after welding
6061 is more expensive but a better chemical match most likely. That is assuming the wheel is 356 or similar. Then 4943 is the best filler.
In your case none of this is critical. It's more about getting a lot of cable on the wheel without getting tangled up.
I like the idea of widening the rim by rolling flat rings. If I was forming rings then I would use 5052 instead but still go with the 4943 filler.
As for filler size you should use .035 based on your experience. It will spray at a lower voltage and be more easy to control. I would and I have everything at my disposal...alloys and sizes.
Tack all your pieces at least every 2 inches everywhere before final welding. Fit-up is critical
I would knock the bearings out and turn that thing down (on a lathe) then make my pieces, put the bearings back in and rotate it around in a vice on a bolt to weld it.
I would also consider thicker material to make a nice rounded inside edge to aid in loading the cable back up. If you did a nice enough job you could put it back on the lathe, and turn it down, and you wouldn't be able to tell it was fabricated.
If you go on my Facebook page there are several photos in the photo gallery of cast ATV swing arms we have extended using 5052 plate.
These we done for years using both 4943 and 4043 filler and have seen extreme abuse without any known failures. After final welding they were extremely hard and durable.
These are my thoughts about how I would go about it if I were to tackle this project..... YMMV
I hope this helps.

[DougM]

Thank you FusionKing for taking the time to respond!
No, haven't been able to source any 5083 in the thickness required anywhere locally (Winston-Salem, NC area). 5052 appears to be readily available.

The mechanical issues with this design are that the proposed tow line (7/64" Dyneema) is quite slippery, and therefore distributes it's tension throughout more wrap layers than any other line-type would. For every other aspect of the tow, the Dyneema is the most preferred tow line due to it's very high tensile strength, low weight, high abrasion resistance, and very small diameter (low air-drag). Because of the accumulated radial and axial loads put upon the rim (compression) and side plates (bending moment) from the many high-tension layers of tow line, the side plates have a tendency to deflect outward if the spool is under-built. This is a common occurrence of other scooter winches. Not a huge factor if the side-plate deflection is small, but there should not be any interference with the trailing arms and the spool sides, obviously. Others have used 6061-T6, but I think they merely used what was most easily available to them without any real understanding of the material properties after welding.
Both 5052 and 6061 appear to have comparable resistance to corrosion in wet environs, with 5052 perhaps a bit better. As the tow line can entrain moisture from towing on humid days, a long storage period could result in poultice corrosion if not insulated with some impervious coating (epoxy paint?).

Currently, the gun has the .030 drive roll installed. Would you still recommend going to .035?
Thank you!
-doug

[FusionKing]

If you buy 4943 then yes switch to .035.
And just so you know 4943 actually lists wheels right on the box!!