2008 Aluminum MacM Trailer - Axle Rusting

[drams_1999]

Ahoy Mates!

So I have just serviced my trailer again (as I do every year) and am becoming concerned about the rusted steel flaking off of my trailer axle. I took the axle off a couple of years ago and after removing the scary looking flaking bits of rust, I treated the whole thing with very expensive cold galvanizing paint. Now it is looking scary again. The worst of it is right under the boat's centerline bunk.

Has anyone ever had their axle fold up or split?

I dunk my trailer in salt water about a dozen times a year and fresh-water rinse it very thoroughly every time I come home (usually within 1 or 2 days of launching).

Obviously I can't access the interior of the axle so heaven knows what has happened in there over the years.

I have a MacM trailer that came from the factory, with a single axle, and torsion suspension system. Aside from this issue, the trailer is fine. I have upgraded some of the other components over the years but the axle and original aluminum frame are still original.

I'd love to know everyone's thoughts on the vulnerability of this axle. Trying to decide if I should shell out some boat bucks for a new one. Wondering how much steel is still left on the tube walls and what the life expectancy is on one of these things.

Your thoughts are appreciated!

Doug

[Tomfoolery]

Absent ultrasound testing equipment, you can tap the axle with a ball peen hammer in numerous spots, get a sense of how it 'rings' when struck, and check the mid-span area to hear how it sounds by comparison. If it's a dull thud, it's probably corroded internally to nearly nothing.

If only the center portion is bad, you could weld a tube to each side or to the underside to reinforce it. The bending stress is lowest at the center, assuming the boat weight doesn't bear on it, so spanning that with some solid metal is a quick(ish) fix. I'm not sure how the bunks on the M trailer are arranged, though.

Or just get a new axle.

[Russ]

I don't remember if the axle is sealed. Memory has me thinking it as sealed, but you should look. If sealed, water shouldn't have a way inside and you are probably okay.

What Tom said ^

Worst case, replace the axle. I added a second one for about $500. That was the whole thing. You might not need the torsion bar and bits so it is probably not expensive and you can DIY or have a shop do it for cheap.

---Russ

[drams_1999]

Thanks for the replies. So last night I crawled under there with a ball peen and did some tapping. Near the wheels where there hasnt been much flaking at all I hear a crisp and resonating ping. Near the center span I hear a solid non resonating thud. It doesnt sound weak....it sounds less pingy (did I just invent a word? Lol) . It felt like it still has solid steel nut clearly not as much as it once did.
The boat rests right on the center of the axle.
Guess I'll put away a few bucks and get a new axle as soon as I can. I'll install it myself as I did last time. It's probably ok for another year or so but it's too much of a risk to take.
Based on my experience.....I think a reasonably well maintained factory axle lasts about 8 to 10 years depending on how much risk you are willing to take.
Thanks again gents....I welcome further thoughts.
Fair winds.
Doug

[dxg4848]

I added second axle this year. Torsion axle (beam only) is $214 and since you are not adding axle you can reuse end units.

[Russ]

Were you able to establish if the axle is "open" or sealed?

When I launched last, there was a long period of bubbles. It alarmed me because I thought I punctured a tire. Eventually it stopped. Check of tire pressure showed no leaks.
So, I wonder if the axle is hollow and letting water in/air out.

--Russ

[Tomfoolery]

Were you able to establish if the axle is "open" or sealed?

When I launched last, there was a long period of bubbles. It alarmed me because I thought I punctured a tire. Eventually it stopped. Check of tire pressure showed no leaks.
So, I wonder if the axle is hollow and letting water in/air out.

--Russ

AFAIK, torsion bar axles are not sealed, at least not trailer versions. Don't know about what VW did with the Beetle and similar cars.

The square bar that rides inside the hollow tube and bears against the elastomeric rods rotates (of course) as wheel load is applied, so unless there's a seal where that shaft exits and the crank mounts, water will be able to get in. One manufacturer even states on their web site that the tube is galvanized inside and out, though what they didn't mention is that if it's hot-dipped, it really has to be plated inside unless the ends are capped. And even then, air holes would have to be drilled. But I digress.

I also don't see MacGregor spending money for sealed axles, if that's available, when a less expensive unsealed version is available.





So I'm guess that's air from the interior of your axle you're seeing. And if the OP's axle has any sag whatsoever from the weight of the boat on it, a small puddle of salt water can sit there essentially forever, until it's refreshed on the next dunk. Which would suggest a careful inspection would be prudent.

By the way, a good welding shop may be able to UT (ultrasonic test) the wall thickness of the axle, assuming it's not a rough galvanized surface, to spot deterioration. And another tube could be welded to the bottom of the existing with intermittent welds (aka 'stitch welding') to gain more time on an otherwise good axle. But the cost is probably the same or more as that of just buying a new axle assembly, and transferring the cranks (or whatever they're called) with brakes and spindle stubs to the new one. Might not even have to disconnect the brake hoses if the hubs are supported.

[Russ]

Wow! That's VERY interesting Tom.

Makes a lot of sense where the bubbles were coming from. I agree, I seriously doubt MacGregor used sealed axles if they cost more.

So, this is kind of a game changer for these axles in salt water. The weight of the boat definitely bows the axle. At least mine did when it was loaded heavy on a single axle. Salt water trapped in there can't be good at all. Almost seems like a design with failure waiting to happen. I wonder if drilling a drain hole would be wise or be creating a rust origin point. Probably no way to flush that out either.

MacGregor has been using these steel torsion axles for over 8 years and we haven't had reports of failures. So maybe it's not a problem.

We are in fresh water, but water neverthless trapped in there can't be good.

--Russ

[Tomfoolery]

MacGregor has been using these steel torsion axles for over 8 years and we haven't had reports of failures. So maybe it's not a problem.

Yeah, I'm just thinking out loud, but in reality, if they're lasting 10 years or more, that's more than what I would guess the anticipated life of a boat trailer in salt water is anyway. And a new axle of the same make/model is not very expensive if you can reuse the ends.

Just keep an eye on it so it doesn't fail completely on the road.