Welding on a rear axle hub

[muddstopper]

I am getting ready to build my knuckleboom and thought I had everything figured out, until I decided to actually start. My thoughts are to weld the cyl braceing to the hub of the 48,000rear axle and let the hub be my swivel point for the boom. Not sure what kind of metal the hub is made from. It is some kind of steel, but doesnt look like cast, but not mild steel either. I want to weld mild steel to the hub, but am afraid the hub metal might break out under load. If I can weld to the hub metal, what kind of rods should I be looking for, high nickle, 7018, something else. I dont want to spend a bunch of time, and money, building the boom only to have it break at the base. I know the hubs are probably 1in or more thick and hold tons of weight when on a big truck, but whats going to happen when I put the welder to it. I thought about just making a steel plate to weld to and just using the lug bolts to hold the plate on, but dont really want to do that if its not necessary.

 

[Shield Arc]

Do a spark test to confirm if the hub is in deed cast iron, or cast steel. If it is cast iron built a plate to bolt on using the lug bolts.
If it's cast steel, preheat the hub to a couple hundred degrees. Use 7018, 312 stainless steel, or Super Missie weld. When you're done welding wrap in house insulation, and let set over night.

 

[Stimw]

Axle should be forged steel. Basically hot pounded into rough shape then machined where needed.
Bolting a plate on with the studs makes a lot more sense, you won't compromise the temper of the steel.
Welding can soften it or make it brittle depending on your handling post welding.

 

[muddstopper]

Its dark outside now and snowing. I'll do a spark test tomorrow. If it is cast steel, I'll preheat with a weed burner and let sit on top of the wood stove overnite after welding. I have a spare hub if I cant get the welds to look right, I 'll just build a plate and bolt on.

As a second thought, I have to mount a large dia sprocket on the hub, probably need to look into bolting on the sprocket, using the lug bolts and using the sprocket for my boom base, kill to birds with one stone. Cant mess the sprocket up, they are around $800 for a new one.

 

[Stimw]

A cheap way to allow welded things to cool down is to pack it in Kitty Litter. Preferably not used!!
I buy a 25 lb bag for under $4.00 at Walmart. My cats show me what they think of it at least a couple times a day.

 

[oldtimer 66]

Hubs, shafts are generally 4140 HT and cast would be 4142, not very common. Commonly refer to as "Shafting". Rc about 30. Can be purchased annealed at 10 to 20. Can be heat treated to the upper 40's to low 50's Hammer hard. Not having a hardness tester you can use a file and get an approx. on the hardness. Suspect it is only in the 30's Google that and see what is recommended for welding. This is from my hard drive which is starting to fill up and give me bad info once in a while. LOL Later

 

[muddstopper]

This is the hub I plan on using. The weld area would be around the lug bolts on the flat flange. I took a file to the flange and it cut pretty easily. I also used the file on a cast iron pot which seemed to be harder. Havent done the spark test, to far to run a extension cord for the grinder, and I dont feel like moving the housing to the shop today. Cold, blowing snow, metal I have to work with is outside, no fire in the shop stove, and give me a minute and I can make up some more excuses.

 

[Stimw]

Your not dealing with an axle you are dealing with a wheel hub. That's a totally different animal.
It will be soft and welding on them is very tricky. I have had to weld stripped out wheel studs and most of them were cast iron.

 

[muddstopper]

Even though I said i would be welding to a axle hub, I thought a few folks where confused and thinking axle or axle flange. I figured the pic would clear that up. Being as its cold i have been sitting around (knapping), pondering the situation and think just making a flat plate to bolt to the hub might be my best option. It would also allow me to simply unbolt the boom for mounting and dismounting, making thinks a lot lighter to handle and easier to work on in the event the bearings or something needs worked on. I'll just use a old wheel to get the centerhole and lug pattern right and see what I can find for flat plate.

 

[Shield Arc]

I think that is your safest route! A mechanical connection is a lot safer than an unknown welded connection.

 

[muddstopper]

Now to just figure out how thick of steel to use for the mounting plate. I,\'m thinking 1/2-3/8 should be fine and is thicker than a truck wheel. Building something similar to this, https://www.google.com/search?q=knu...3drivers.com%2Fcatalog%2F320%2F361%2F;400;400 but boom wont be quite as heavy

 

[Shield Arc]

I'd use 1/2-inch at a minimum, but would feel safer with 3/4-inch thick plate, with at least 4 gussets.

 

[metalmaster]

keep in mind a truck wheel has very little leverage compared to a lever arm several feet from the pivot.

 

[muddstopper]

I am just planning a light weight boom. The hub is a 48000lb rear end. Half that is 24000lb. I am guessing at the leverage since I dont really know how to figure it. 1500lb at about 14ft should be around 21,000lb. Since most lifts are not made at max extension, and axle safety factor is about 5-6:1 and use speed as a factor, I should be ok. If you know something I am not considering, please point it out.

 

[mikefromnh]

How about something like this instead?

Slewing Ring Bearing with Outer Gear 12 14" OD with Matching Hydraulic Motor | eBay

 

[CNC Dan]

I think that is your safest route! A mechanical connection is a lot safer than an unknown welded connection.

Old saying:

"A good welder knows when to use a bolt."

 

[CNC Dan]

keep in mind a truck wheel has very little leverage compared to a lever arm several feet from the pivot.

But they go over bumps and pot holes.

 

[muddstopper]

Tons of snow outside, doubt I will be working on this again this weekend. I have located some 1/4in 4x4 tube to use for the boom. Spent a lot of time trying to figure out the angles for making the boom and cyl mounts. Think I have the math figured out. Going to draw it out on the shop floor before I start cutting and welding. Still looking for a 60+ tooth double #60 sprocket, Theres a 78tooth one on ebay at a good price, but dia is over 17in. Would work great for the swing, but not sure I have the clearance to make it work. Hub flange is a a little over 13in dia. I plan on boreing the sprocket to fit over the backside of the hub and drilling it for lug patten, about 11.25in bolt circle. I figure the large lugs, if long enough, should provide enough support to hold the sprocket and the boom mount together. Not sure the lugs are long enough, I might have to bore the lug holes out to accept regular bolts.

 

[ts01]

a good cast rod is cast alloy t-60. used it many time great results

 

[BukitCase]

You're limited by chain pitch as to how many teeth in your sprocket - since #60 chain means 6/8" spacing on the rollers, 60 teeth would result in a circumference (at the center of rollers as they sit in the sprocket teeth) of 45 inches, or diameter (plus twice the amount the teeth stick up past center of rollers) of 14.324" - add maybe an inch and a half to that, and a 60 tooth sprocket would come out to close to 16" in diameter.

Only way around it I can see is if you didn't need/want a full 360 deg. rotation - then you might be able to cut a half circle or some other portion of it, if that would buy you any clearance.

Dunno if you've seen this, but the guy has some fun stuff on his site -

Notes on Sprockets and Chains

Have you considered maybe a ring gear on your truck hub, driven directly by a slow speed hydraulic motor with a smaller gear on it? Might be harder or easier, just throwing stuff out ... Steve