Trailer axle/tire question

[aczlan]

Can you perhaps use those same drawings for dual axle with brakes on all wheels, and explain which axle will cause the brakes to grab and lock, and why?

it will act the same as the drawing with rear brakes, but the effect will be more pronounced as both axles will be moving in harmony (the front of the equalizer being pushed up by the front spring and the back being pushed down by the back spring)

My thoughts have been that the equalizers serve to equalize or compensate for irregular surfaces, such as a pot hole or a rock or bump, etc. In the normal trailer situation, the front axle already has more weighI on it due to the 10% tongue weight

AFAIK with a dual axle leaf spring equalized trailer at rest on flat ground the load will be the same on both axles no matter where on the trailer the load is, if I had access to a dual axle trailer and a set of scales that would measure both axles separately I might load my FIL's 7510 Kubota and see what happens to the weight when it moved from front to back (if anyone has the chance to do this test, let me know how it turns out), I predict that the axles would be within say 25-50 pounds of each other (barring a sticky equalizer) but that the overall weight on the axles would change based on how much weight went to the tow vehicle.

I am thinking that the load shifts fwd, even more in a braking situation. How much weight is shifted to the back axle is up to conjecture. No one seems to know

Good question, my math skills aren't up to figuring out the forces involved and all that good stuff.

It would be neat to see a trailer being pulled down the road with a video camera looking at the wheels and springs to actually see what happens to the wheels, when a hard braking situation occurs, and which set of brakes will lock up

With the 20' (or was it 24') enclosed torsion spring trailer that I used to pull behind a F450 (front slightly higher than the back) when I did landscaping had the feature where if you didnt drop the power on the brake controller way down after you unloaded 3 1500#+ mowers and a pair of 800# mowers the front tires left nice black skidmarks, but that is completely unrelated to this discussion.
The 18' dual axle leaf spring equalized open landscape trailer we had would (IIRC) lock up the LF tire first, then the RF then the back ones (if you hit the manual brakes when driving)

The question might be is. if the equalizers are designed to equalize the load on the frame, do they also equalizer the braking force on the axles. Some people say some grab, and others say never.

they cannot equalize braking force on the axles, the diagrams I did above show that when the brakes are applied on either or both axles the front axle will be lighter than the rear one, the is due to the face that the equalizer is a lever, and it will act as a lever until it breaks.
as for grabbing or not that depends on how the brakes are adjusted (tensioned), where your brake controller is set (how much juice you are sending to the magnets) and how good the wiring to the brakes is.


Aaron Z

 

[J_J]

Aaron, Thanks, good explanation.

My thinking is that if the front axle is lighter due to spring action, and if the same current is sent to all electro magnets, then the axle with the lighter load will grab first because of the least resistance. So a question might be how do you set the brakes for the best braking force. If you set it just before lockup, which would probably the front, then the rear brakes will not be set correctly. You would think someone would have come up with a variable resistor in the front axle brakes , adjusted to match the braking force of the rear brakes, or a pulsed brake system similar to anti-lock brakes.

 

[aczlan]

My thinking is that if the front axle is lighter due to spring action, and if the same current is sent to all electro magnets, then the axle with the lighter load will grab first because of the least resistance. So a question might be how do you set the brakes for the best braking force. If you set it just before lockup, which would probably the front, then the rear brakes will not be set correctly. You would think someone would have come up with a variable resistor in the front axle brakes , adjusted to match the braking force of the rear brakes, or a pulsed brake system similar to anti-lock brakes.

you could adjust the tensioners to give you a little less braking power inn the front, but that wouldn't help when unloaded, because if you were to back them off enough to keep from locking up when unloaded it wouldn't help very much when loaded... hmmm, perhaps a switch to kill the power going to the front brakes (with the breakaway switch bypassing it, because if your breakaway switch trips you want all the brakes to come on) to be used when unloaded...

Probably the simplest way to do it is to dial down or shut off your brake controller when unloaded and adjust it properly when you are loaded.

Aaron Z

 

[rdbrumfield]

I don't care which axle locks up as long as they are all braking. If I have to stop that quickly I want every anchor I can get. When it comes to tandems, all mine have brakes front and rear.
Ever see a semi with half the axles braking, they would be sitting until the fixit wagon showed up.
When loaded I run up the amps for braking, empty, I back it off so I just get a small tug from the rear and let the pulling vehicle take care of it.