Lightweight Car Trailers

[kerrynzl]

I just noticed...Is that a surge brake up front?


I hope not, but if it is...

Surge brakes are better than no brakes, and are common on boat trailers

It has drums on the front axle so maybe. And surge makes sense as many vehicles have hitches , not so many with brake controllers.

Over here in NZ we can get a proportional brake controller that mounts on the trailer [ it is activated off the stoplights ]
Outside of the USA most vehicles have orange turn signals and separate stoplights circuit [not blinking stoplights] so the trailer mounted controller works great.

 

[kerrynzl]

Why dual axles for such a light weight and short length?

Dual axles have the advantage of using a 90-92 load index tyre on a trailer which are cheap.
With a single axle you need to pony up for 115+ load index tyres, the extra cost goes a long way to adding an idler axle.
So dual axles don't cost much more.

The biggest issue with single axles is the public perception of value [ single axle = 1/2 price ] which is why I never build them.

The biggest handling issue with single axle leaf spring trailers is "roll oversteer"
[torsions don't have this issue]
When one side of the suspension compresses ,the axle moves rearward on an arc! This causes the trailer to dart off into the same direction causing weight to transfer to the other side [compressing that side]
This is the main cause of swaying on single axle trailers.

If the springs had the pivots at the rear and slippers/shackles at the front the suspension would be roll understeer which is more stable.

Single axle travel trailers [caravans] swaying all over the place with traffic backed up behind them, were the curse of NZ roads in the 1970's

A dual axle leaf spring set-up with shackles on the rocker so the wheelbase shortens under compression is more stable . It promotes roll understeer which requires a bit more steering effort instead of steering correction.

 

[Mr.N]

Surge brakes are better than no brakes

Really, that is what you're sticking with?


You'll not see me towing a vehicle with surge brakes, but I like to error on the side of safety.
They are only common as they are much cheaper and allow any vehicle to tow the trailer.... Not always the safest solution.
.

 

[iagsxr]

What's so wrong with surge brakes?

 

[Don-F]

The only thing I know thats a pretty big disadvantage with surge brakes is that if a trailer starts fish tailing you cant reach down and hit the controller to straighten it out. That may explain the greater than normal wheel spacing and the dual axles, as they both contribute to stability. I would still choose surge brakes over no brakes in a heart beat.

The problem with "armchair quarter backing" trailer designs is most people really get fixated on one thing or another, without looking at how the design functions as a whole. Its the same way with cars. Bill Jones once told me "I have beaten people with the parts they threw away, just because I took the time to make them work together." Thats good advice no matter what your building.

 

[iagsxr]

The only thing I know thats a pretty big disadvantage with surge brakes is that if a trailer starts fish tailing you cant reach down and hit the controller to straighten it out. That may explain the greater than normal wheel spacing and the dual axles, as they both contribute to stability. I would still choose surge brakes over no brakes in a heart beat.

The problem with "armchair quarter backing" trailer designs is most people really get fixated on one thing or another, without looking at how the design functions as a whole. Its the same way with cars. Bill Jones once told me "I have beaten people with the parts they threw away, just because I took the time to make them work together." Thats good advice no matter what your building.

Right on, I'm with you. And if it starts fish tailing behind your midsize sedan you're in a world of trouble no matter what the brake system.

I wish you'd giddy up building something. I've gotten some ideas from this thread already.

 

[Don-F]

I wish you'd giddy up building something. I've gotten some ideas from this thread already.

Alternate ideas are nice and I have learned a lot too. All the trailers here have cool stuff about them, and then there are the trade offs. When I first started this thread I thought that there may be an almost perfect trailer that someone just had to show me. Eight months later I think they are all cool, but its also give and take design wise. We really can't have it all and fixing one area usually means giving up another. I think thats partly why I put off building a trailer for eight months.

 

[volleyball]

I have owned many single axle trailers and not one has a slipper leaf. I never thought of them as a good idea. What if the spring breaks?

 

[Mr.N]

Right on, I'm with you. And if it starts fish tailing behind your midsize sedan you're in a world of trouble no matter what the brake system.

With a eletrical trailer brake system they've a nice lever for activating the brakes, pulls the trailer back in line very nice.




Unless you're on ice... Then you're just along for the ride.

 

[Mr.N]

What's so wrong with surge brakes?

They can pulsate on and off leading to the trailer tires locking up, if in less than ideal conditions and some times on dry pavement, they will then let go and lead to pushing the veichle and sliding the trailer sideways ending up in a jack knife.... Even under load limits.





They are not safe in my book and I've towed up to 900k, tow vehicle had four wheels.

 

[kerrynzl]

Really, that is what you're sticking with?


You'll not see me towing a vehicle with surge brakes, but I like to error on the side of safety.
They are only common as they are much cheaper and allow any vehicle to tow the trailer.... Not always the safest solution.
.

So you actually believe in your own ********
Surge brakes transfer a percentage of mass into the tow vehicle to activate them.
Disc brakes require a higher clamping pressure for the same brake torque, so a drum surge brake will actually stop in less distance because the tow vehicle isn't compromised as much.
In the UK mechanical surge brakes were the only legal way to brake a light trailer until recently [under 3000kg] It was also illegal to lock them out also, so they used "free backing/auto reverse" drum brakes.

They can pulsate on and off leading to the trailer tires locking up, if in less than ideal conditions and some times on dry pavement, they will then let go and lead to pushing the veichle and sliding the trailer sideways ending up in a jack knife.... Even under load limits.



They are not safe in my book and I've towed up to 900k, tow vehicle had four wheels.

The only time they pulse is when there is too soft a spring in the surge coupler and/or too small a master cylinder , and some ******** cowshed engineer puts the brakes on the front wheels of a rocker equalizer suspension.

If the brakes were on the correct [rear] axle the brake torque increases traction, and the braking forces will equalize with surge pressure.

Electric brakes are a better [and cheaper] option. But surge brakes are not dangerous if correctly installed [ not some redneck hack job by some "know all" ]

 

[Lippyp]

Yep, over here electric brakes on trailers only became legal in the last couple of years and very few people use them yet. My little single axle Ifor Williams 6 x 4 trailer which is rated at 1100KG tows like a dream and even heavily loaded I've never had an issue with the brakes or the trailer steering itself. I guess it's what you get used to.

 

[Mr.N]

kerrynzl,

We'll have agree to disagree.

The state I live in has over 15,000 lakes and I've seen way to many boat trailers with surge brakes jack knifed. I've also had a good friend with many hours trailering rent a surge brake trailer that almost died from it causing a jack knife in light rain.
One of my first trailer was a surger.... Never again.


Let's get back on topic!

I really like the idea of designing the minimum trailer for the load.

 

[kerrynzl]

kerrynzl,

We'll have agree to disagree.

The state I live in has over 15,000 lakes and I've seen way to many boat trailers with surge brakes jack knifed. I've also had a good friend with many hours trailering rent a surge brake trailer that almost died from it causing a jack knife in light rain.
One of my first trailer was a surger.... Never again.


Let's get back on topic!

I really like the idea of designing the minimum trailer for the load.

I originally wrote "Surge brakes transfer a percentage of mass into the tow vehicle to activate them."

The problem with boat trailers is "the boaties" [they are usually recreational users of trailers]
If the driver does stupid **** like apply the brakes mid-corner the surge brakes will try to jack knife the tow vehicle.
Electric brakes have an external power source so they don't do this [as much]

Surge brakes are not dangerous..... Fuckwit drivers are.
If they "trail brake" into corners or follow too close , they will get what they deserve eventually [usually taking out some innocent person]

If you don't agree with my comments about boaties, try spending a Saturday morning at a boat ramp watching these clowns trying to back their trailers into water.