Features of the ideal Custom Trailer

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Tomfoolery
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Re: Features of the ideal Custom Trailer

Post by Tomfoolery »

Neo wrote:In Oz equalized springs are are sold only in sets. Some 7 leaf ones have 1600Kgs rating and other 5 leaf ones have 2000Kgs rating. :o ... I'm trying to work out what would be the best ones to go for (if I go for Tandem). Based on your experience what rating would you go for?
If it were me, I'd use a light suspension with strong axles. IMO, at least, trailer wheels, tires, and bearings are a bit overrated. It's a common complaint in the boat and RV world of trailer tires blowing out, bearings not lasting, and so on. Reducing the load on a bearing by a factor of 2 will increase the theoretical life by about a factor of 10 (varies as the 10^3.333 power for ball bearings; slightly different for roller). More than speed, load reduction will increase bearing life, and using two 3500 lb axles and 1750 lb tires [1590 and 795 kg, or whatever that translates to in Oz availability] with a soft-sprung, equalized suspension would, again IMO only, be the way to go. Which is why I went that way. :wink:

I calculated the spring rate and capacity of my modified springs, and they come out to somewhere in the 1200 lb range (capacity) each. Don't remember the spring rate, but it's something like 600-700 lb/in, if memory serves, with about 900 lb on each spring. And yes, my 3500 lb [1590 kg] trailer is technically overweight, but they don't normally pull boat trailers over at the truck weigh stations on the highway, and I've never seen portable scales used for boat trailers either, so I'm not worried.

There are even resilient equalizers of various styles (and cost), though mine rides soft enough. These boats are our babies, but they're tough enough to take the ride of the OEM single leaf spring axle, so I don't see a need to get crazy (like air suspension). :D

Modern torsion axles, by the way, have a variable spring rate. The further you deflect the suspension, the higher the spring rate, unlike leaf and standard coil, which have a fixed rate (progressive leaf and coil is progressive, though). So lightly loaded, the torsion axles are 'soft', but can handle the full weight on either axle when going over speed bumps (for instance), even though they're not equalized. So they also work well in dual axle configurations, as long as they're both loaded equally. And I don't think they're recommended for triples.

As an aside, here's one of many articles on LT vs ST tires for trailers. Perhaps a moot point, if you can't even guy ST tires in Australia, but an interesting read nonetheless. https://rvingwithmarkpolk.com/2012/11/0 ... -lt-tires/
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Neo
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Re: Features of the ideal Custom Trailer

Post by Neo »

Thanks Tom ... Some great information here :)
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Re: Features of the ideal Custom Trailer

Post by Neo »

Tomfoolery wrote:... but I put mine on the rear axle because with equalized leaf springs the rear will increase load while the front will decrease due to the equalizer between them.
Hi Tom,

To a certain degree does the above still apply to my Slipper Springs?

To explain, I have UFP calipers and disc hubs on my front (original) Parallel bearings axle. Discs and Caliper pistons are badly corroded. The local UFP supplier is slow to respond (no phone number to call) and I need a lot of parts to get these brakes in working order.

The second/rear axle is standard tapered (GM) bearing. Axle stub are currently a bit corroded on the bearing surfaces and the axle is too long. So I'm looking to cut the Axle stubs off (to align the wheels under the mudguards), buy new calipers and discs which will cost just an additional $150.

Obviously the discs will then be on the rear axle but should be much easier to maintain (with good local support) in the future.

Just wanted your thoughts on all this?

All the best.
Neo
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Tomfoolery
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Re: Features of the ideal Custom Trailer

Post by Tomfoolery »

Neo

Equalized suspension means, of course, that both (or all, if more than two) axles carry the same load.

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But when you apply torque to either axle via the brake(s), that torque is taken out by reaction in the springs to the hangers and equalizer. Below is an exaggeration, but it highlights the effect. The front axle tends to rotate upward about the front hanger, and the rear downward about the rear hanger, so the rear axle takes marginally more load. It doesn't matter which axle (or both) the brakes are on as far as load transfer, but since the rear axle ends up taking a bit more and the front a bit less, it makes sense to put the brakes on the rear axle. One manufacturer even specifically recommends putting the brakes on the rear, if only one axle has brakes.

Image

In the pic, I left the forward axle off the ground, but in reality, it just takes a little less load and the rear a bit more load, with the tires and springs elastically deforming.

Your slipper springs are not equalized (there are equalized slipper spring configurations, though), so braking one axle will deform the springs a little, but won't change the loading on them.

Image
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Tomfoolery
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Re: Features of the ideal Custom Trailer

Post by Tomfoolery »

Torsion suspension, on the other hand, has what amounts to drag links. Lateral braking force will tend to put some moment on the arm if the axle center is lower than the torsion bar center, but the brake torque will certainly work to rotate the suspension, unloading the wheel a little.

Image

But if both axles have brakes, they both tend to rotate, and the trailer lowers a little, but the wheel loading doesn't change. I've seen this a lot on certain heavy trailers with trailing suspension and air bags, where stepping on the brakes hard at low speed caused the whole trailer to momentarily sag a bit then recover, or stand up tall when going in reverse and hitting the brakes.

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Re: Features of the ideal Custom Trailer

Post by Neo »

Wow, thanks for all the great information Tom ;-)
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Re: Features of the ideal Custom Trailer

Post by Neo »

Hi Tom,

What would be the effect if the front axle stubs were mounted higher (by about an inch) than the rear? ... I've just noticed that this is how my Trailer has been setup, but I doubt it's intentional.

All the best.
Neo
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Tomfoolery
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Re: Features of the ideal Custom Trailer

Post by Tomfoolery »

The front axle would take less load than the rear, and the tongue weight would be a bit higher than if they were equal, or equalized. How much depends on the spring rate and tire stiffness. Cartoon sketches exaggerated for illustration purposes.

Unloaded:

Image

Loaded:

Image

Notice both the springs and the tires deflected more on the lower axle. The extreme case of this is the front axle not touching the ground at all, so the tongue weight would be at the highest. But in reality, there's still load sharing, so the increase over balanced load isn't that great.

Seems to me they could have either padded one axle (longer U-bolts if needed), or the slipper ends, to bring them to the same unloaded elevation.
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Re: Features of the ideal Custom Trailer

Post by Neo »

Thanks Tom,

So before I go leveling these out, do you think there could be ANY technical reason why they've done it this way?
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Tomfoolery
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Re: Features of the ideal Custom Trailer

Post by Tomfoolery »

I can't think of a single technical reason why one axle would be lower than the other. Your two axles are different, and spring stacks come in different arch heights (distance form eye center to top of spring at bottom of arc), but they often don't have much selection within certain spring types. So it's likely they did the best they could with what they had.

But from your pictures, it looks like you could add a small solid block between the spring and the new axle, to lower that axle, assuming that's the one that's too high. Kind of like a lift kit, but with the axle above the spring, it will lower it (the frame) relative to the other axle.

The spring will have some sort of pin or socket head cap screw to locate the axle to the spring, which will need to be duplicated on the block. Or replace the bolt with a longer one going through the spring and the block. But it could be a pin rather than a bolt. No way to know until you take it apart.

U-bolts may be long enough already, but new ones are cheap enough.

Only tricky part is measuring, with the spring lash removed. Slipper springs will move vertically a little when you remove the load, so it might be a difficult to get a good measurement on spindle offset differences. The springs have to have enough load on them to make contact with the frame, rather than hanging through the lash.

Image

Mine, when doing some suspension work. A spacer would be added in the gap to raise the axle, and a longer socket head cap screw used. Or a solid block with a recess on the bottom for the screw head, and threaded at the top for a short cap screw. Or a pin driven into the top. Something to lock the spacer to the axle so it can't slide around.

Image

But before going to all that trouble, are you sure it's even a problem? You can probably get a pretty good sense of how much load each axle is taking by looking at the tires with the boat on the trailer. Just make sure they're all inflated the same, and are the same type and size (radial tend to look lower than bias ply).
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Re: Features of the ideal Custom Trailer

Post by Neo »

Thanks for the great write-up Tom.

I've not had a boat on this trailer yet, but thinking back, when I removed all four wheels I discovered that one of the rear tyres was flat. So I guess the front tyre/axle was holding up the rear so the tyre didn't look flat on the trailer.

That front Axle has UFP brakes and Parallel bearing stubs. UFP have very poor support over here and anything to do with Parallel bearings it expensive here too.
So I've now ordered new Deemaxx Brakes and yesterday evening I cut off the old stubs, ready for new tapered bearing stubs to be welded on. This way I'll increase the axle length (to the same length as the rear axle) and lower it too.
It's a lot more work, but after all I've done so far I want to be sure I'm 100% happy with the trailer later. 8)

All the best.
Neo
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Re: Features of the ideal Custom Trailer

Post by Neo »

sailboatmike wrote:Duel 50mm solid axles are huge over kill, each 50mm axle is rated at 2000Kg.

I wouldnt be loading the frame to more than that and of course as soon as you go above 2000Kg rating you need breakaway brakes which almost doubles the cost.

Huntsman have a 2000Kg tandem system with 45mm axles with 2 choices if springs the standard leaf springs setup for load sharing and rocker / roller springs. Im not sure what the difference is.

TSP forum has some trailer gurus I will put a post and ask if they know the difference.

My thought is that if I go tandem axles the extra weight of the extra wheels, springs axles etc takes away from the weight carrying ability of the trailer even though all these parts aren't actually supported weight, all the authorities seem to care about is the GVM which is the total weight of the trailer and load, so if these parts weight 60Kg thats 60Kg less load I can carry on the trailer
Hey Mike,

Not sure if this helps you but when I took off my two axles I noticed the weight of the original Mac axle (Box section 50 x 75 x 5mm) was about half the weight of the other 45x45m solid axle.
Tomfoolery wrote:Only tricky part is measuring, with the spring lash removed. Slipper springs will move vertically a little when you remove the load, so it might be a difficult to get a good measurement on spindle offset differences. The springs have to have enough load on them to make contact with the frame, rather than hanging through the lash.
Hey Tom,
The above was very tricky to measure. But as the axle stubs needed to come off I ended up laying the two axles side-by-side and making the stub heights (and axle length) the same.

All the best.
Neo
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aviro
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Re: Features of the ideal Custom Trailer

Post by aviro »

Hi folks
for your infornation 4 years ago i modified mi 2009 trailer with double axel.
i bought a second axal similar at the one a have on the trailer.torsion one with brake.
2 axel similar with brake to be legual in Quebec canada,
result, no problem at all. 4 trip canada to florida on snow rain and all and more than 3000 miles in Canada during the summer.
coming down to Florida 2 weeks ago i left with 2 tire realy bad and they blow out one afther the oter.the result, i never feel when one tire fail it is alway somebudy pasing me making signe to tel me i have a flat tire .
now i replacing the stock tire by good radial one and it is beter. But more than10,000 mile with the stock tire is not bad.
i grease my bearing each time before i back off in the wather.
simple ang good,secure mods.
Jean-Francois
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Neo
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Re: Features of the ideal Custom Trailer

Post by Neo »

Good information Jean-Francois.... Thanks :)

In my case the jobs almost done. Just need to fit two new white rims, finnish the goal posts and weld on the new mudguards...
The drawbar is 8" longer ... benefits....
I always reverse down the ramp to the point where my cars rear tyres are just touching the water line.... My Mac seem a bit easier to position and winch up this time
When I step across the drawbar I don't catch my foot (or me nads :cry: ) on the handbrake lever anymore :D

My :macm: loaded on its new trailer just today 8)
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