8 lug Ford 9"

[broncocraigellis]

I've run a 9" before (obviously) with good results; accordingly, I am thinking of using one in the buggy. I'd rather not go back to 5 lug wheels, so I need to get an 8 lug 9" semi-floating axle. However, no one makes flange blanks large enough to drill an 8 lug pattern that I've been able to find. I still have to call a couple of companies.

So the problem is not having the axle flange large enough to drill the 8 on 6.5" pattern. I'm thinking of having a ring cut to increase the diameter of the flange. Then I would chamfer both edges and weld the ring to the axle flange. I would put the axle in a lathe to weld and only weld in short bursts, letting the flange cool before continuing. Then the stock 5 holes would be filled with weld and the face of the flange trued with the lathe. I would then mark and drill the new 8 lug pattern using the lathe.

Give me your opinions. I have had some feedback from an axle manufacturer who thinks the idea would probably work, but the axle should not be operated at highway speeds for safety. I do not see how that would be a problem unless the flange became brittle from welding and separated from shaft or broke. Not continuously welding seems like it would prevent the flange's metal from weakening too much.

Of course, using a 9" would hopefully save weight over my 14B pig. I would also shave the 9" housing.

[broncocraigellis]

No one?

[rccolacc]

I'm not an expert in materials by any means, but after taking some materials science courses, I do not think this is a good idea. It might work for a little while in your application, but the flange you are welding on will not have the desired material properties you would want in an axle. The weld changes the material, regardless of how hot you get the flange. I need to talk to someone at work about this a little more to get better definition and to clarify what I'm saying, but for the sake of an answer right now, I vote not welding on a flange.
What about spacers?
I'll get back to you later on it.
-RC

[broncocraigellis]

Thanks for the reply, RC. Yeah, spacers are an option. So, welding on the flange would change the properties of the metal making it more prone to breaking? Where would it be most likely to break? I'm just trying to wrap my liberal arts brain around the negatives of doing this.

[rccolacc]

Alright. After a little research and talking with another engineer, I got some answers. Here's what I came up with:
-Axle shafts are heat treated in order to withstand the shock loading and stresses that driving puts on them. Some axles are only heat treated at the splines and others are fully heat treated. I also saw on some websites that axles are made in one piece, meaning the flanges are forged (hammered flat from the round stock). I know from experience that cutting and rewelding axle shafts never works because the weld messes up the heat treating and basically makes the metal brittle around the weld. Cracks form around weld and it breaks. I know you’re not directly welding on the axle part of the shaft, and I don’t know if your axle flange is heat treated, but I’m just throwing it out there. I would think that in order for it to work, you have to be REAL sure the weld is good and not porous. I would not be surprised if the flange breaks after it’s been shock loaded a few times (like bouncing on a rock). Then again, it may hold forever. Who knows I guess.
-Currie’s website has prices for redrilling stud holes on axle shafts for new bolt patterns. On one part of the website they mention a special charge if the bolt pattern is larger than the flange. It doesn’t say what they do if it is, but it sounds like it’s possible. I’d call them to see what they do, or even what they charge to have the axles redrilled.
If it were me, I would not weld the flange. If the flange breaks, the damage if it coming off (taking the brakes out) would not be good. See what Currie does and maybe that will solve this whole problem.
Hope this helps.
-RC

[rccolacc]

Something to think about:
I was in a class called Failure of Materials last year and all we did was look at failed pieces and parts of things and try to figure out why they broke. Cool class, but anyway-- we had this 3" shaft off of a fish pond aerator that had snapped off right at the hub. It was solid steel and as driven by a motor that only put out about 20hp I believe. This shaft was press fit in the hub and was supposed to have a woodruff key in it to allow power to be transferred. Well the fish pond people ran out of keys or maybe they lost the key, and they welded the shaft to the hub in order to get it to work. The motor cycled on and off to aerate the pond like it should, and everyone thinks the weld was just as good as using the key. Well 3 weeks later the shaft breaks off right outside the weld. Lesson learned was that the woodruff key (which is heat treated) takes the shock loads a lot better than the rigid weld, and the shaft broke around the weld because the weld was rigid.
It was pretty amazing to see that a 20hp electric motor sheared a 3” solid shaft, but it’s just an example of how something logically seems like it will work, but in the end it doesn’t.
Take it for what it’s worth. Hope it helps.
-RC

[Busted Knuckle Racing]

Craig, why not just build a custom axle using D60 parts, with a 9" center section? I am sure something like this has probably been done... The 9" has been modified more than any other axle.

[broncocraigellis]

Yeah, I've seen guys who made full floating 9"s using D70 or 14B spindles welded onto the 9" axle tube. This seems to work well for them...After doing more research, I believe I'll just redrill the front wheel hubs to 5 on 5 1/2. I was under the assumption that this was not possible, so I would have to buy new hubs @ $230 a piece; however, I saw pictures on pirate of a guy who simply redrilled his hubs and turned them down to match the 5 lug rotor diameter. That will be the cheapest option for me.