Added second axle what do you think?

[Sheppie62]

I know I’m asking for it, inviting criticism, but if something is wrong with what I’m doing I want to know, or at least consider the idea. I bought (2) new 3500lb axles with springs, hanger kit, slip on disc brakes for front axle, new surge tongue for disc brakes. I welded the hangers on 3/16” angle iron, so I could weld better and not mess up frame rail, also the idea was to be able to slide the axles back and forth to get a good balance, then weld in place (see grinding marks).

[NiceAft]

What exactly are you asking? Whether to create a second axle, or how you’re doing it?

Many have decide that a second axle is right for them. As to the nitty details of how to do it, only a select few here are qualified to answer that; I Would expect they would need more info than the supplied photos show.

I can tell you I’m impressed.

[ris]

We simply added a second axle behind the first. We left the original spring hangers in place and placed the second set of hangers behind the first. Trailer pulls fine at 65 mph. Our Chevy 1500 has a trailer tongue weight capacity of 600 or 650 lbs. If you do not have enough tongue weight the trailer will fishtail and this can cause an accident.
Richard

[svscott]

We simply added a second axle behind the first. We left the original spring hangers in place and placed the second set of hangers behind the first. Trailer pulls fine at 65 mph. Our Chevy 1500 has a trailer tongue weight capacity of 600 or 650 lbs. If you do not have enough tongue weight the trailer will fishtail and this can cause an accident.
Richard

So you didn't use an equalizer spring mechanism? Any idea what your tongue weight actually is?

[ris]

We will be home in about 18 days and can send pics then. Also will get tongue weight. There is a triangular piece that the front and back springs attach to, but we attached it to the original rear spring hanger.
Richard

[Tomfoolery]

I think what you've done is a good idea, and allows for tuning for tongue weight. Just be advised that the OEM pole tongue, which is 3x3x3/16" HSS (structural tube) of unknown but probably low grade steel, has a nasty habit of rusting right at the most highly stressed location - where the two channels meet it. If you're increasing the tongue weight, which is a good thing if the tow vehicle can handle it, do watch for that pole tongue bending. There's not a large design factor on that member with the 350 lb or so tongue weight the 3500 lb trailer would have been designed for.

And while you're at it, tap around the bottom of that pole tongue with a ball peen hammer, listening for a nice ring. If it's rusting, it'll sound dull, or duller than the top or further toward the coupler. More than one member here has had that pole tongue fail, including at least one on the road. Not something you want if you can take steps to avoid it.

[Jimmyt]

I know I’m asking for it, inviting criticism, but if something is wrong with what I’m doing I want to know, or at least consider the idea. I bought (2) new 3500lb axles with springs, hanger kit, slip on disc brakes for front axle, new surge tongue for disc brakes. I welded the hangers on 3/16” angle iron, so I could weld better and not mess up frame rail, also the idea was to be able to slide the axles back and forth to get a good balance, then weld in place (see grinding marks).

Don't be too concerned about getting roasted over a post. This is not that kind of crowd (see Tomfoolery's post above). Virtually everybody here is supportive and offers constructive criticism. They will let you know if you're walking off a cliff, but are generally pretty nice about it.

I like the concept of building a suspension subframe and then moving it to get the correct tongue weight. The only down side I can think of is, you've created some inaccessible spaces between the steel members. If you can keep the moisture and air out of these spaces, or pretreat them for rust prevention, it will be fine for a long time.

So, how did you set/check the tongue weight and what was your target weight?

Looks like you're doing a good job.

[OverEasy]

Good idea on being able to adjust your suspension and tongue weight…

Just be aware (as you probably are) that too much tongue weight can lead to over stress on the tongue tube. The increase in available load distribution having the second axle is a really good idea.

Not faulting single axle design but having four tires share the load is an improvement over only having two shouldering the load.

Within reason the handling between a single vs tandem are similar. The tandem ties generally better while the single can back-up turn in a smaller radius (but not by much on a regular basis).

As was mentioned try to ensure you have inspection access to do regular checks and preventative anti-rust treatments.

Note: while some have attempted to “seal” box beam members by welding the ends shut but in reality this type of practice this just traps moisture inside. Even a small hole will allow humidity or moisture into a sealed space where it will accumulate and react with the steel. A sealed humid environment will cause more rusting than a flooded environment. Humidity plus oxygen on steel = rust. (A flooded environment would help exclude oxygen.) Rust also attracts and holds more moisture which perpetuates the process and problem. A better design characteristic is to make sure the box beam can easily breathe, fully drained and dry out.

If you can pretreat or prime all interior and exterior surfaces with a rust preventative penetrating oil paint that is a great idea. I’ve used a cone spray on the end of a hose to coat hollow beams with good success in the past that have held up well. My favorite is to flood fill hollow beams with penetrating rust preventative paint and allow it to sit in the hot sun to warm up a bit before draining (but generally that is a challenge on larger structures as you might imagine).

I’ve found that removal of the “mill scale” by grit blasting prior to painting or rust preventative treatment helps make the paint or treatment work better and last longer.

Low spots should have drain holes that should be checked regularly to ensure they don’t become blocked. Periodic clean fresh water flushing of all surfaces (including interiors) in the hot sun and periodic retreatment with rust preventative penetrating paint can dramatically extend the useful life if your trailer.

Just some thoughts that may be of use.

Best Regards,
Over Easy

[Starscream]

I know I’m asking for it, inviting criticism, but if something is wrong with what I’m doing I want to know, or at least consider the idea.

Like Jimmy said, this isn't the place that you find a lot of criticism. It's not like FB or other forums.

Reminds me of the time I responded to an FB post about Macgregors. I thought it was a post from one of the MacGroups on FB, which usually aren't too bad (as long as you don't mention vaccines or Greta Thunberg, even in jest). But it wasn't from a MacGroup, it was a general post that made its way into my feed. So, stupid me, I said something nice. Aaaand Kablooey. There are a lot of nuts out there.

Our moderators do a good job of kicking the crazies out. Now we just put up with a grumpy member or two, one of them who doesn't always read the full posts before commenting, but always apologizes for it. And we love him anyway.

[OverEasy]

Personally I think it’s great that Sheppie62 has upgraded his trailer with those really nice axles and springs.
His allowing for axle adjustment is very perceptive of the need to take into account the uniqueness of a vessel that has been and will be modified to suit an owners desires.

Those are a great improvement over some of the trailers we looked at under the MacGregors we looked at in our search.
The POs of OverEasy did a great job selecting the twin axle galvanized bolted SeaLion trailer and we are VERY appreciative to have it.

There were several other boats we looked at where we just would not have felt they were safe to have them leave the driveways or fields they were in.

While I’ve designed, fabricated and spec’d trailers for personal and industrial use I have always appreciated other peoples constructive perspectives and the kindness they have shown in passing on good information and ideas by doing the same.

On my very first trailer to carry 3000 lbs on a single axle a mentor pointed out to me that I would be shortening the potential useful life of the design if I was to weld “C-channels” back to back as that would inevitably trap moisture and I would have no way to effectively protect those captured surfaces after welding. I heeded his advice by changing it to a spaced off design. At the same time I made up two sections, one of each design, and left them to the elements after painting. The back-to-back design was crap after about five years while the spaced one was still almost as good as new.

I later did the same for a box beam where one was weld sealed with an 1/8 inch diameter hole to simulate production weld pinholes on the bottom side and the exterior painted and the comparison one open on each end and painted inside and out. Both were grit blasted inside and out (prior to painting.) The open ended one was again nearly as good as new after five years exposure. The sealed one was a badly rust flaked interior while the outside looked fine.

I also did a set of accelerated salt fog tests on open ended box beam sections that had been vapor degreased.
Painting was accomplished utilizing a commercially available penetrating oil rust inhibiting paint.
A- One was with the original mill scale.
B- One was with the original mill scale but painted on the exterior.
C- One was with the original mill scale but painted on both the interior and exterior.
D- One was grit blasted to remove the mill scale on the exterior only and painted on the exterior.
E- One was grit blasted to remove the mill scale on the exterior only and painted on both the interior and exterior.
F- One was even grit blasted to remove the mill scale on bothe the exterior and interior and then painted on both the interior and exterior.

The best result after a 2000 hour exposure was sample F, next in descending order were E, D, C, B then worst was A.
Sample E is what was used for the production application given the substantial difficulties in being able to adequately grit blasted the interior surfaces.
Sample E was far and away superior to D, C, B and A.

The mill scale once it was compromised allowed for a trapped moisture migration path along the interface with the base metal in each case sample with mill scale.

Having a mill scale free surface performed substantially better.

Just some real world experience tid-bit that might be useful to anyone interested.

Best Regards,
Over Easy

[Sheppie62]

I am very concerned about the space between the spring hanger sliders and C Channel frame rails. I have seen what happened between the goal posts plates and the C Channel at the back of trailer. Rust has incredible expansion pressure (see any concrete structure where moisture gets to the rebar). I gobbled marine sealant all over the angle iron spring hanger to completely seal it before I bolted it together. Hoping this would be sufficient to stop any moisture from getting in there. I have no idea if this will completely stop rust. If I have to pull the spring hangers backwards then that seal will get broken and I’ll have to clean and reseal it again (Hoping balance is correct where it is now). I plan on rubbing sealant all over any possible points moisture can penetrate trailer. A guy at a trailer manufacturer/ repair shop suggested using bed liner coating on entire trailer.

[Sheppie62]

This is sealant I used, I hope I can move axle if needed. I just read the Loctite Door and window for $7 tube is almost same stuff for a lot less. Might be good for less critical applications. (Like smearing all over my trailer).

[Jimmyt]

This is sealant I used, I hope I can move axle if needed. I just read the Loctite Door and window for $7 tube is almost same stuff for a lot less. Might be good for less critical applications. (Like smearing all over my trailer).

Sounds like a solid approach. Well done. Hope you won't need to move it.

[OverEasy]

Hi Sheppie62

Using truck bed liner is an interesting idea if all the surfaces are really clean. Basically a damage tolerant paint

If the surfaces aren’t perfectly clean though you might find rust forming in isolated pocket. You can see the results in the wrecking yards.

Sometimes the best anti rust agent isn’t sealant but rather grease…

Hope this helps,
Best Regards,
Over Easy

[Sheppie62]

So maybe zerk fittings to lube between the channels? Seal all but the corners, then pump some grease thru till grease comes out. Could score the metal slightly with a grinder to allow flow. Then seal up till next lube.