Anyone ever add a tandem axle

[Dmpaul89]

my 24' pontoon came on what I believe is a 20'ft trailer. its worked fine for a few years but I don't pull it far. the rear of the boat hangs past the rear of the trailer 4ft. not much tongue weight. and has the little fat 8" rim tires on a single axle. I need to replace the tires soon just due too age and ive noticed the frame of the trailer bows down a little in the rear from all that weight hanging off the end. Im thinking about adding an axle to go behind the current one to make it a tandem. has anyone done this and how did it work out? might even consider extending the frame a few ft as well. its a 89 landau Bear trailer. Buying a new trailer isn't in the budget.

 

[NYBo]

You need another trailer, not another axle.

 

[MTboatguy]

You would have to re-engineer your trailer to handle the boat correctly. I have seen guys put a tag axle on their toon trailers before, never did talk to any of them to see how it worked out for them, but if you can swing it, I would find a new or a newer used trailer to handle your boat.

 

[62Scout]

My 1st thought would be that the trailer is severely undersized for the weight of the boat. I'd suspect that your boat likely weighs more than the current axle is rated for as well. You could add two more axles, and still not fix the frame being undersized for the boat. Adding another axle to the rear also isn't likely to have a significant impact on tongue weight either, as going to a tandem will have a minimal effect on your center of gravity of the trailer (or balance point front to rear), unless you currently have a crap load of weight within a few inches behind the current axle.

Going to a tandem (or triple) axle is done for additional load carrying ability, not balance changes.

If your current set up is bowing under the current weight, extending the rear of the trailer will do squat at best, and may even make the issue worse due to additional leverage.

If you're dead set on retaining the current trailer, which I'm not recommending, you'd also need to do some center of gravity calculations, and move the axle back some to balance it out better. Adding a 2nd axle may be needed from a total weight standpoint too.

 

[GA_Boater]

If you're dead set on retaining the current trailer, which I'm not recommending, you'd also need to do some center of gravity calculations, and move the axle back some to balance it out better.

A trailer balanced like this is a swaying trailer. The axle is moved to adjust tongue weight and a balanced trailer has zero weight on the ball.

Dmpaul - Can you add a couple of pictures?

 

[Scott Danforth]

Sell the wrong ttrailer you have, buy the right trailer you need

 

[M2HB]

I really don’t have enough info for an accurate analysis.

IF the frame rails are parallel to each other, and strong enough you can build an adjustable tandem axle set under some 4”x 2” x 1/4” angle iron with the 4” web in the vertical position. This allows you to adjust the tongue weight by adjusting the axle set location. This also strengthens the frame.

More info is needed to determine the feasibility.

 

[Dmpaul89]

Here are some pics. Im thinking a second axle on the rear would help with the bowing just because of the reduced leverage. I havent had any problems yet with the single axle and they are 10 ply tires. They do get warm though! Farthest i go is about 50 miles one way to carlyle lake. Im a farmer so the fabrication is no huge task. I havent priced an axle yet but im thinking the project should be under $500. The floor jack is just to keep it from tipping while im working in the deck!

 

[Dmpaul89]

With a full tank of gas i estimate the tongue weight at 50-75 lbs currently. Havent had any sway issues. I pull it with a 2001 f250 quad cab diesel.

 

[M2HB]

That trailer should be easy to convert to tandem axles. If that is standard channel it will have a sharp 90 degree edge. The 2” x 4” angle iron would need a 1-1/2” x 1/8” steel strap welded to the inside of the 2” web of the angle iron (flush with the outside of the web) to eliminate the radius inside of the angle iron. It is simple to remove the existing axle mounts and weld new tandem axles mounts on the bottom of the 2” web of the angle iron. I would buy a 20’ piece of the angle iron and use 10’ on each side for the axle mounts. That would significantly strengthen the trailer frame. I would use 1/2” stainless bolts every 2’ through the vertical 4” web of the angle iron and the trailer frame. If the trailer frame was drilled accurately, every 6” then you would have the axle adjustment every 6”. This all assumes that the two trailer rails are perfectly parallel to each other. this would be an easy conversion. While you are at it, it would be easy to add a couple of feet to the back of the trailer.

 

[M2HB]

An example of an angle iron axle mount with fenders. This one is for a single axle, but the concept is the same.

 

[GA_Boater]

Got a dumb question - Why the floor jack under the rear frame rail? You better weigh the tongue and I saw what you said about the jack.

 

[Scott Danforth]

Buying a new trailer isn't in the budget.

modifying your existing trailer will cost you much more than selling what you have, adding a few hundred to that and buying what you need

based on this pic alone, your trailer is 6' shorter than you need and way to under-sized capacity wise

what is with the jack?

 

[GA_Boater]

And right above the jack, the rubber bungee cord isn't gonna hold the toon on the bunks. You need some proper, unstretchable tie-downs.

If you have 500 bucks to spend to make an undersized single axle trailer into a dual axle undersized trailer, you can probably find a right-sized for close to the same dough.

 

[H20Rat]

With a full tank of gas i estimate the tongue weight at 50-75 lbs currently. Havent had any sway issues. I pull it with a 2001 f250 quad cab diesel.

That is way too little tongue weight. Tow vehicle doesn't have much to do with sway, any trailer can start oscillating, although lighter vehicles can make the problem worse.

Agreed though, I'd be looking for a new trailer vs converting to a tandem. Slapping a second axle on to it isn't great either, you want a true walking beam tandem.

 

[Dmpaul89]

I put the jack under there because if i walk on the deck and go behind the helm the boat will tip. thats not a bungee cord on the toon that's a nylon binder strap. It would be pretty difficult to sell my trailer without first buying another trailer. I dont have anywhere i could leave the boat in the water for a length of time, so that means id have to jack it up and put it on blocks here in the yard. well, you guys have given me much to think about. thank you

 

[M2HB]

It would be easier to buy another trailer if one was available. The problem most people don't consider is that if you buy a used one, you probably will still need to do a lot of work to it. Also, finding the trailer that properly fits your boat isn't always easy.

It appears from your picture that your trailer may be bowed down in the back. It may also be an optical illusion.
Building an adjustable axle assembly as I described above isn't hard to do if you have someone to may a few welds for you to put the axle mounts and fenders on. It certainly would strengthen your current frame. It would cost you two axles, the front one with brakes, a little steel and a couple of fenders.

 

[jimmbo]

Looking at the pics, I'd say the trailer is too small for the boat. I will assume you tie a red or orange flag/ribbon to outboard? Adding an extra axle won't solve the overloading issue. I'll bet the main(A) frames are bent front and rear of where axle-spring frames attach. Run a straight edge to check.
I guess you could get/make heavier and longer A frames, bunks and cross members in addition to the extra axle. To do it right both axles should be the same, so you would need two. By then a complete trailer would be cheaper. There really needs to be laws that prohibit dealers from selling boats with undersized trailers.