DIY Tandem Axles

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trdprotruck
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Sailboat: MacGregor 26X
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DIY Tandem Axles

Post by trdprotruck » Mon Nov 02, 2020 8:39 am

So I'm in the middle of a repower my :macx: with a Suzuki DF90 and I started thinking that I better do something about the old rusty mac trailer. The frame rails weren't that bad, but the axle and springs hangers were horribly rusty...

I sourced all my parts from ebay and amazon:

Parts List (So Far)
  • 2 Galv Axles
  • 1 Galv Hub Kit
  • 1 Kodiak Disc Brake Kit
  • 2 Galv Spring U bolt sets
  • 2 205/75/R15 LRD Tires
  • 2 Galv 15" wheels
  • 2 sets spring perches
  • 1 tandem spring hanger kits
I read a lot from this forum and I wanted to keep the tandem axles centered with the original axle to maintain the same tongue weight, but the bend in the frame rails would not let me move the axle that far. I moved the axle as far forward as the frame would allow me, but with the extra weight in the back, I think it is going to be a wash. The only hiccups I had was that the kodiak brake kit did not include the hardware for mounting their bracket to the axle. I guess I'm going to have to order it separately.

Overall I'm happy with he result, but there's still a lot of work to do.

Image

Image

Image

Next items on the list:
  • brake lines
  • fenders
  • caliper mounting hardware
  • bunks
  • carpet
I'm starting to think, I should have just bought a new trailer :D

svscott
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Re: DIY Tandem Axles

Post by svscott » Tue Nov 03, 2020 5:31 am

I've been thinking about doing the same thing for my boat trailers. I hate the idea of being right at the recommended weight limit and an always afraid of a tire blowout.

Finding the right balance was a little tricky when I modified a 26M trailer to fit my 26D. My new trailer only has a single axle with torsion bar suspension that bolts onto the aluminum I beam so it was pretty easy to move around. If I was starting fresh with all new components, I'd opt for electric brakes though. My vehicles all have nice brake controllers already already wired in for when I'm hauling my work trailers.

Once it's all complete, I'm interested in how it tows and how much it cost you to add the 2nd axle.
1987 26D - Three Hour Tour; 1998 26X - to be named

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Tomfoolery
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Re: DIY Tandem Axles

Post by Tomfoolery » Tue Nov 03, 2020 6:21 am

trdprotruck wrote:
Mon Nov 02, 2020 8:39 am
I read a lot from this forum and I wanted to keep the tandem axles centered with the original axle to maintain the same tongue weight, but the bend in the frame rails would not let me move the axle that far. I moved the axle as far forward as the frame would allow me, but with the extra weight in the back, I think it is going to be a wash.
I think you may have (accidentally) done yourself a favor by not moving that front axle as far forward as you wanted. Mine was moved such that the mid-point between front and rear axle is where the original single axle was, as witnessed by the remnants of the old hangers still visible, and the tongue weight is too low for the loaded boat. I have to pile stuff into the bow to get the tongue weight where I want it. The PO added some structure to the forward hanger to allow it to move that far forward.

You might not have that problem now, though your OB is probably 100 lb or so heavier than my Honda BF50.

Do be aware that the pole tongue is a bit light, so you may want to reinforce it while you're at it. Another 3x3x3/16" tube, notched where it passes the two side channels, and stitch welded to the underside will make a huge improvement, both to strength and to stiffness. The notch won't hurt anything, as it'll be in the middle of the composite beam (all shear there). The top and bottom 'flanges' are where the strength against bending is in this situation, and it's only needed where bending moment is highest anyway, right where the channels meet the tube.
Tom
Be seeing you . . .

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ris
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Re: DIY Tandem Axles

Post by ris » Wed Nov 04, 2020 7:35 pm

When we put tandem axles on our trailer we left the front axle in the original location and put the second axle behind the original location. We also put 4 inch drop axles in place of the original to lower the height of the trailer which lets us get into some shallower boat ramps. Nothing is worse than not enough tongue weight. This year we are going to replace the springs and the U-bolts that attach the springs to the axle. We also replaced the tongue last year as it is the original trailer and the tongue was rusting out.

leefrankpierce
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Re: DIY Tandem Axles

Post by leefrankpierce » Thu Nov 05, 2020 6:16 am

What are the specs on the existing MacX trailer axle if I wanted to add a second?
I live right by a Northern Tool, are the axles they cary good?
If you do not mind me being lazy, which Northern Tool would you add to compliment the existing?

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Tomfoolery
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Re: DIY Tandem Axles

Post by Tomfoolery » Fri Nov 06, 2020 7:39 am

ris wrote:
Wed Nov 04, 2020 7:35 pm
This year we are going to replace the springs and the U-bolts that attach the springs to the axle.
If I might make a suggestion, use lighter capacity springs than the originals. You don't need 7000 lb worth of suspension to carry a 4000 lb boat (minus tongue weight). Equalized leaf springs will share the load, but the total capacity only has to be enough to carry the load between them. Say 1250 lb each springs for 2500 lb axles of the same eye-to-eye length instead of the 1750 lb each springs used on 3500 lb axles. That's 5000 lb of suspension, which is still too much (IMO), but better than 7000 lb of suspension. https://www.etrailer.com/Trailer-Leaf-S ... 19275.html

I dismantled my existing mis-matched spring stacks and reconfigured for a softer suspension. And yes, I did calculate spring rate and capacity for each of the two different spring arrangements (the OEM's were crazy thick and stiff) before making changes. I'm a mechanical (primarily) machine design engineer and just can't help myself. :|

It's a sickness - just ask the admiral. :wink:
Tom
Be seeing you . . .

beechkingd
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Location: Central VA 1996 26x

Re: DIY Tandem Axles

Post by beechkingd » Fri Nov 06, 2020 2:36 pm

leefrankpierce wrote:
Thu Nov 05, 2020 6:16 am
What are the specs on the existing MacX trailer axle if I wanted to add a second?
I live right by a Northern Tool, are the axles they cary good?
If you do not mind me being lazy, which Northern Tool would you add to compliment the existing?

Mine failed last year and I was able to get a new axle custom made by Champion trailers. The original axle on my 96 26X trailer was a 2X3 drop axle but the original spindle wasn't mounted on top of the axle tube so I went with the 2X2 tube since they weld it on top. It fit perfectly, the only thing lacking was brake line loops which I ended up attaching with some ziptie standoffs.

https://www.championtrailers.com/galvan ... e-over-85/

Hub face 88" Spring center 68"

trdprotruck
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Re: DIY Tandem Axles

Post by trdprotruck » Fri Nov 06, 2020 3:41 pm

Tomfoolery wrote:
Tue Nov 03, 2020 6:21 am
I think you may have (accidentally) done yourself a favor by not moving that front axle as far forward as you wanted. Mine was moved such that the mid-point between front and rear axle is where the original single axle was, as witnessed by the remnants of the old hangers still visible, and the tongue weight is too low for the loaded boat. I have to pile stuff into the bow to get the tongue weight where I want it. The PO added some structure to the forward hanger to allow it to move that far forward.

You might not have that problem now, though your OB is probably 100 lb or so heavier than my Honda BF50.

Do be aware that the pole tongue is a bit light, so you may want to reinforce it while you're at it. Another 3x3x3/16" tube, notched where it passes the two side channels, and stitch welded to the underside will make a huge improvement, both to strength and to stiffness. The notch won't hurt anything, as it'll be in the middle of the composite beam (all shear there). The top and bottom 'flanges' are where the strength against bending is in this situation, and it's only needed where bending moment is highest anyway, right where the channels meet the tube.
Thanks for the info! I'm glad that I wasn't able to move the axles all the way forward now. Now that you mention it, I was also thinking I should do something about the pole tongue as the bottom is getting quite rusty. I think stitch welding another 3x3 would be the easiest route, but I'm wondering if I should just replace the whole tongue... I could stitch weld the 3x3 myself, but replacing the tongue is more work than I'd want to take on myself right now.

trdprotruck
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Re: DIY Tandem Axles

Post by trdprotruck » Fri Nov 06, 2020 4:03 pm

The stock axle is 68" spring center to center, 86 HF-HF with a 3in drop.

In case some people were wondering, the axles I got were made by Tie Down Engineering, galvanized, 87" HF-HF with no drop. I actually wanted to raise the trailer since my driveway has kind of a steep angle and I have to always to play games with my hitch height so that the transom doesn't scrape on the ground at the transition to the street.

I bought it via ebay for $175 shipped/axle: https://www.ebay.com/itm/Galvanized-2-S ... 2749.l2649

I could have bought some cheaper tubular painted axles that were meant for utility trailers, but I decided against it because I couldn't find the right width or I would need to grind/reweld the spring perches. The square galvanized axles are pretty much "bolt on" and for the price I got two new axles instead of a single custom one...

-Randy

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Dougiestyle
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Re: DIY Tandem Axles

Post by Dougiestyle » Fri Nov 06, 2020 4:45 pm

This is what I did with the front extension.
Dougiestyle wrote:
Wed Dec 04, 2019 5:23 pm
Things I have learned and done to my trailer (1998 OEM steel)

1. INSPECT your trailer, look close, scrape off any indications of underlying RUST, this is a common problem. If any rusting is found you need to investigate!. Is it pitting? viewtopic.php?f=11&t=23553
Any loss of metal needs to be evaluated, due to the trailer being built to minimal thicknesses.

2. Modification: Bracing the tongue. I used a 3” x 3” x 3/16” square tubing with spacers welded to the support tube only.
Then U-bolted to the tongue. No welding was done on the trailer.
Image

3. Remove and replace: Both brake assembly with reversing ability. New master cylinder, new nylon bushings in springs, new greaser bolts. Flush the lines.This work would have been much easier to take to the local trailer shop.
Remove 15" (rubbing) and replace with 14" Class D tires.
Dougiestyle
1998 26X , Nissan 50D, "Water Buffalo"

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Tomfoolery
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Re: DIY Tandem Axles

Post by Tomfoolery » Tue Nov 10, 2020 5:06 am

Nice job on the tongue. And you gotta love the hole in the gate for the coupler. :D

trdprotruck: Bolting a second 3x3x3/16 wall tube under the original (same dimensions) doubles the strength and stiffness. Stitch welding another tube to the bottom makes it about 3 times as strong and 5-1/2 times as stiff (vertical deflection). Horizontal strength is still doubled, as is stiffness. "Gluing" them together makes them act as a single member, since they can't slide on each other as they flex, like leaf springs do. That's where the extra strength and stiffness come from.

That's based on 6x3x3/16 tube, as I'm too lazy this morning to actually work out what the composite beam made from two smaller ones would be, but it's close enough. U-bolted together is more than adequate. Especially considering that the original single tube was adequate by itself if not rusted through. :wink:
Tom
Be seeing you . . .

trdprotruck
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Re: DIY Tandem Axles

Post by trdprotruck » Tue Nov 10, 2020 10:20 am

Hi Doug and Tom,

I guess I'm trying to decide whether to bolt/weld another 3x3 or just replace the tongue... The reason being is that I do see some rust (not nearly as bad as the failure pictures), but I'm thinking that there is no way to stop the rust since it is from the inside of the tube. If I stitch weld/bolt it, I'm thinking it is more of a stop gap since the original tube will continue to rust away and eventually fail.

Decisions decisions....

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Tomfoolery
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Re: DIY Tandem Axles

Post by Tomfoolery » Tue Nov 10, 2020 11:20 am

If you stitch weld them together, the two horizontal tube walls that are against each other do essentially nothing. They don't have to be there at all, in fact. That's why stitching another tube to the underside will get a second life, as long as there's enough metal in the corners to support a weld. Run a continuous small bead each side if in doubt.

But there's nothing wrong with just replacing the tube. Maybe use 1/4" wall, to increase both stiffness and bending strength by about 22% over the original with 3/16" wall. Just a lot more work.
Tom
Be seeing you . . .

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Dougiestyle
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Re: DIY Tandem Axles

Post by Dougiestyle » Tue Nov 10, 2020 6:06 pm

Tomfoolery wrote:
Tue Nov 10, 2020 5:06 am
Nice job on the tongue. And you gotta love the hole in the gate for the coupler.
Here is another couple of photos showing the plates welded to the support tube only. I stacked them to match the I-beam thickness. A total of 4 clamps were used for attaching to the original tongue.

Image

As far as the hole in the gate, the wife says "It wont fit", I said "problem solved".

Image

Image
Dougiestyle
1998 26X , Nissan 50D, "Water Buffalo"

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