Another AT style trailer

Martyn

Supporting Sponsor, Overland Certified OC0018
I thought I’d add a little more to the leaf spring discussion. There is more to deal with than just the influence one tire has on the other here. I’m not totally against leaf springs but they have some limitations.

Designing for load;
With a leaf spring the design has to take into account the maximum load of the trailer. In the case of most utility trailers the cargo capacity can be as much as the trailer weighs itself, so it has to be able to handle a 100% gain in weight. The smoothness of the ride will be dependant on the cargo load, the closer you are to maximum capacity the less the bouncing. This is less of an issue with a vehicle as the load capacity % is much less than a trailer.

Reduction in travel;
As the cargo load increase the leaf spring start to bend downward de arching the springs. This downward movement reduces the amount of travel the suspension has to use for absorbsion. A reduction in an already short travel spring.

Slow reaction time:
Leaf springs need to be long to absorb high frequency bumps, but even long leaf springs and shock absorbers are not quick enough to absorb wash board and rough terrain. All of the trailer bounce is then transmitted through to the tow vehicle making a bumpy ride even more uncomfortable and difficult, damages cargo, stresses the trailer.

Weight of assembly:
The live axle assembly accounts for a considerable amount of weight, the axle, long springs and a couple of shock absorbers adds hundreds of pounds in weight to your trailer.


Multiple connections:
To gain clearance for 33 –38” tires most spring combinations need a shackle. The combination of a mechanically clamped series of leaves, and 3 bushings increase the likelihood of sway.

So it may be more than scrambled eggs you have to worry about, it could be something devastating like broken bottles of beer !!!! :Wow1:
 
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RunninRubicon

Adventurer
Got it. Sprung and unsprung weight. Hence the addition of an air shock to compensate for added weight thus keeping near the original height and travel Something like adding air to air-bags.

Reaction to travel-Hear one should concur with your premise that leaves, even with teflon pads are slower to react then perhaps coils or air-bags. However, in this application, speed is NOT paramont and hence remembering to traverse rough roads with liberal applications of brake and forethought seems to steem the concern for my eggs and lantern socks. As you mentioned a long spring is more supple and reactive to change.

Weight is an issue, though there is something to be said about wear and tear. A typical leave pack serves there vehicles a very long service life with little to no attention required. There is no free lunch for performance.

Multiple connections.....I count 2 on leaves. Fore and aft. The shackles can count as 2 pair. 2 for the A-frame as well...not counting the shock mount, nor the air-bag mount though leaves can have shocks as well.

33's are on two trailers I can attest to that run standard length shackles and an under axle construct (much more stable then spring over). >33" tires, If you want more height, add a longer shackle or deeper arched springs. CJ and YJ suspension manufactures have been doing this since the 60's.

I agreed with your first statement-there are several ways to serve ones needs.

This discussion about leave springs, their strong and weak points has been tossed around a long time from many different folks. I recognize you have chosen to follow your intincts.....me too. It's that simple. It's just another way to look at things.

I appreciate that you have investigated the good and bad of an old suspension vs other technologies. Thus, one can appreciate the insight and reasoning behind your premise of using what you have. It is commendable.
The suspension under the AT is very cool. A very innovative approach to an old problem of shaken beer.
 

cruiseroutfit

Well-known member
For those with leaf sprung axles and weight concerns... air shocks or airbags (the latter would provide the most tuning ability). The technology is old and cheap to implement. Though in reality, you should try to design your spring rates around the loads you anticipate to carry. I never tow my trailer empty, so my unladen weight isn't remotely an issue. I designed my ride height and spring rate for the loads I constantly have... which don't seem to change by more than + or - say 50 lbs?
 

Grim Reaper

Expedition Leader
The biggest cause of sway is lack of tongue weight. It is usually recommended 10% of the total trailer weight.

You can actually loose tongue weight with speed. Depending on the airflow over the tow vehicle and the trailer it can actually cause lift on the front of the trailer. Volks Wagon did some wind tunnel tests that showed that. A small wing on the roof of the Tow Vehicle to kick the air up and over the front of the trailer does seem to help prevent the vacuum the forms between the trailer and tow rig lessening that lift.

You might be able to make significant changes to the handling with placement of the roof top tent if you have one on the trailer. Try moving it back and leave some open space on the front of the lid. The will change the wind foil shape.

Soft rear suspension on the tow vehicle can also lead to some sway complaints. I had a ramp queen K5 that I ended up with a BIG towing problem with and the suspension of the truck contributed to it heavily. I ended up adding two leafs to the pack. The extra spring rate really helped the towing manners and actually helped the on road ride and handling.

To much tongue weight can also give handling issues. Mostly noticed by a really light and non responsive feel in the steering.
 

RunninRubicon

Adventurer
cruiseroutfit said:
For those with leaf sprung axles and weight concerns... air shocks or airbags (the latter would provide the most tuning ability). The technology is old and cheap to implement. Though in reality, you should try to design your spring rates around the loads you anticipate to carry. I never tow my trailer empty, so my unladen weight isn't remotely an issue. I designed my ride height and spring rate for the loads I constantly have... which don't seem to change by more than + or - say 50 lbs?

Excellent point. The weight only varies with water, fuel and food that is added to the trailers load. Easily w/i the ability of these leaf-springs to carry.

I suppose one big factor IS the easy and cost or implementing this suspensioin and as I originally mentioned, I like the analogy of keeping it simple. Shows you how much fore-thought an innovative suspension like that which is found under the AT took to implement.

Never meant to infere that a leaf spring suspension was superior. Just mentioned an observation that was made and received some pointers as to what might indeed be some corrections to make to a trailer with something else under it. The dialog has been informative though, for sure.
 

Hitch-Toys

New member
Thank you.
I Built this trailer 6 years ago. Just for myself to wheel, fish and camp around Moab, Rubicon, Baja and all the local trails around California and surounding states. Within my travels I have had a lot of interest to build and sell these trailers. This year I am giving it a shot. So far so good.
 

ntsqd

Heretic Car Camper
RunninRubicon said:
snip.........
Shows you how much fore-thought an innovative suspension like that which is found under the AT took to implement.
Now I'm curious what AT's suspension looks like. Missed a prime chance as I never paid any attention to Rod's trailer when it was around.
Are there any pictures online?

John, I've long pondered what the market would be for a near 1/4t trailer clone. I've wanted to build one for myself. Have zero need for it, just looked like a really cool project. I hope it pays off for you.
 

Willman

Active member
Great looking trailer!!!!

Are those 35" or 33" tires on that trailer????

Good luck.....you have a good looking product:box:

:D
 

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