Walking Beam Trailer

[ChugiakTinkerer]

I've been looking at some trailers for off-road use and am contemplating building my own. There are some mighty fine examples in some older threads, and I'll shamelessly steal all the good ideas from those.

The trailer available from DR and Woodland Mills is pretty much what I want. I'm exploring a design for something a little heaver duty and sized for my needs.

What are my needs? Something I can haul with my Arctic Cat Prowler (tow limit 1500 lbs) as well as my LS XJ2025 tractor. I want it to have a tire width the same as the Prowler, and am looking at a walking beam design to allow for taking it over some rough terrain. I'd like to be able to tow it with the tractor with upwards of 2,000 lbs in materials.

My first effort in Sketchup is here:

And here's what I've got for a walking beam. I'd like to have 360 degree rotation for the walking beam, for when I'm in the really nasty stuff.

In addition to the reasons above for building my own, I live in Alaska and freight shipping of big items is brutal. I'm guessing the freight for the $1500 Woodland Mills unit will be another $600 or more. So I could potentially get a better trailer for less out-of-pocket expense.

My initial design uses 3x2 rectangular tube (1/8" wall) for the main elements. I experiments with the StructuralWeb beam calculator and determined that the walking beams would have no problem supporting a ton of cargo. My concern is the center beam for the frame. I'm pretty sure that I would get a lot of deflection on the tongue. Anyone have suggestions on what an optimal tongue beam would be?

 

[franklin2]

Keep the same material, but put a truss on the tongue. Much like a engine hoist has one on top, put yours on the bottom of the tongue to support excess downward force on the tongue.

Or, keep the same material, but put another piece along side the original center tongue piece. In other words, double it up. Stitch weld it the full length top and bottom. Double it up the full length, from the tip of the tongue all the way to the rear. Make your other crossmembers shorter to compensate.

 

[Cord]

I think you beam trunion is too short and will twist. Consider having the shaft be full width with a pair of pillow bearings on either side.

 

[boggen]

have seen a few trailer tongues were they just tac welded flat bar to sides/top/bottom. of the longer tongue. same concept of what franklin2 talking about. but more likely more geared towards 'torque' / twisting the tongue vs. causing the tongue to bend. in essence making the tongue portion a thicker wall .

the pieces you have dropping down for the rotation of beam/wheel. see about running axle all the way across for the beam/axle rotation. so the axle itself becomes a support brace per say. to keep the wheels/beams from angling/bending out.

=========
looking at the 2 trailers you posted links to. the single central beam structure. looks rather nice, and looks like everything slides onto central beam then bolts/pins to central beam to keep it in place. vs welding everything to the central beam. assuming part of this is for perhaps packaging everything and tossing on a pallet then assembly were ever. but looks from pictures, the slide bolt/pin combo would allow you to adjust things.

if you are not going with central beam thing. i am then wondering why do you need a central support running all the way to the back? ya part for tongue. but all the way to the back?

 

[GLyford]

Those short sections of box supporting your beam pivots will fold flat in no time without some sort of additional bracing (internal web, cap the ends, gusset up to crossbar, etc. etc.). That's probably going to be you single highest stress point in the whole structure. I realize this is just a concept sketch, but that point needs a bunch more attention.

Take a look at this pic fomr someone else's thread:
http://www.tractorbynet.com/forums/...-convert-air-brake-equipment-trailer-sub1-jpg
and look at how much structure they have around their pivots. Their loading is different because they are supporting both sides of the beam, and I understand why you don't want to do that. The other commenter's idea of continuing your beam pivots across the trailer as a single piece (or welded to a single piece if that long a piece of round is hard to get) is a good one, it gives your pivots a much longer lever arm to resist twisting the structure.

Speaking of twisting...have you looked at what a ton load will do to twist your walking beams between center and end, not just the simple beam bending end-to-end? You will basically have a twist with 1/4 ton times the distance from the beam to the center of the tire (maybe a foot?), so 500 ft-lbs, before you even start getting into multipliers for shock loading from hitting stumps, etc. I'm not saying you are wrong that it will be OK, I am just saying run the numbers and see.

 

[ChugiakTinkerer]

Thanks everyone for the feedback. I'm a monkey-see, monkey-do sort of builder so I am a babe in the woods when it comes to knowing whether or not my proposed structure is adequate. So please keep up with the suggestions and comments.

Keep the same material, but put a truss on the tongue. Much like a engine hoist has one on top, put yours on the bottom of the tongue to support excess downward force on the tongue.

Or, keep the same material, but put another piece along side the original center tongue piece. In other words, double it up. Stitch weld it the full length top and bottom. Double it up the full length, from the tip of the tongue all the way to the rear. Make your other crossmembers shorter to compensate.

That may be why I see so many of the dropped tongue hitches - not so much because the height is an issue but to allow for gussets. Hmmm...

I think you beam trunion is too short and will twist. Consider having the shaft be full width with a pair of pillow bearings on either side.

Thanks, I should have mentioned that this is a conceptual design, not at all final. I plan on making the trunion connection more substantial.

 

[ChugiakTinkerer]

have seen a few trailer tongues were they just tac welded flat bar to sides/top/bottom. of the longer tongue. same concept of what franklin2 talking about. but more likely more geared towards 'torque' / twisting the tongue vs. causing the tongue to bend. in essence making the tongue portion a thicker wall .

the pieces you have dropping down for the rotation of beam/wheel. see about running axle all the way across for the beam/axle rotation. so the axle itself becomes a support brace per say. to keep the wheels/beams from angling/bending out.

=========
looking at the 2 trailers you posted links to. the single central beam structure. looks rather nice, and looks like everything slides onto central beam then bolts/pins to central beam to keep it in place. vs welding everything to the central beam. assuming part of this is for perhaps packaging everything and tossing on a pallet then assembly were ever. but looks from pictures, the slide bolt/pin combo would allow you to adjust things.

if you are not going with central beam thing. i am then wondering why do you need a central support running all the way to the back? ya part for tongue. but all the way to the back?

One of the up sides of not having a continuous axle is the increase in ground clearance under the trailer. My first instinct is to think I don't want an axle going all the way across but I should know by now that my instincts are not always right. :laughing: It's definitely worth looking at your suggestion, or some variation thereof.

The short box is just a spacer for me conceptually. I would at the very least have it with a 45 degree cut tapering down and weld on a plate at each end to give it support. The stub axle would probably be a square end like this guy ( Spindle 1-1/2" Square x 4" Long Stub, for 2, lb. Trailer Axles Redline Trailer Spindles SP24BT8 ) to facilitate welding. Or something completely different - way out of my league here and open to suggestions.

 

[ChugiakTinkerer]

Those short sections of box supporting your beam pivots will fold flat in no time without some sort of additional bracing (internal web, cap the ends, gusset up to crossbar, etc. etc.). That's probably going to be you single highest stress point in the whole structure. I realize this is just a concept sketch, but that point needs a bunch more attention.

Take a look at this pic fomr someone else's thread:
http://www.tractorbynet.com/forums/...-convert-air-brake-equipment-trailer-sub1-jpg
and look at how much structure they have around their pivots. Their loading is different because they are supporting both sides of the beam, and I understand why you don't want to do that. The other commenter's idea of continuing your beam pivots across the trailer as a single piece (or welded to a single piece if that long a piece of round is hard to get) is a good one, it gives your pivots a much longer lever arm to resist twisting the structure.

Speaking of twisting...have you looked at what a ton load will do to twist your walking beams between center and end, not just the simple beam bending end-to-end? You will basically have a twist with 1/4 ton times the distance from the beam to the center of the tire (maybe a foot?), so 500 ft-lbs, before you even start getting into multipliers for shock loading from hitting stumps, etc. I'm not saying you are wrong that it will be OK, I am just saying run the numbers and see.

As noted above I need to do some more work on my mock-up to reflect where I think I want to be. A brace angled up from the axle stub to the frame above would strengthen things pretty well without bringing an axle into the picture. Should still allow good clearance of brush and tussocks.


Regarding the trailer I linked to, I am thinking of something comparable from a performance standpoint, rather than actually riffing off the design. Doesn't mean I shouldn't borrow a good idea. I'll chew on their design a bit, but I think you are right that it's made that way because it gets shipped as a kit. Not necessarily a bad thing, I can see that an adjustable trailer length could be quite handy.

 

[boggen]

*rubs chin* you noted clearance underneath and not wanting an axle all the way through to each side. but for me. only time something like that has become an issue. is when i sunk everything into a wet spot in hill side, that i did not know was there. and i was already past my axle point if not deeper in the mud. granted your in alaska and riding on top of snow itself is beyond my knowledge. but even with snow here in Illinois. i would end up getting stuck with pulling vehicle first, before ever worrying about trailer tires getting stuck. in my instances it would be going through 2 to 3 feet or deeper snow drifts trying to clear the driveway.

i have more issue rolling over logs with tractor / truck / even an ATV clear back in the days. the pulling unit needs to get over them logs as well. granted... with tractors and field implements. some of the larger field stuff have "trip wheels" something like if not the same walking beam idea. so when trash (dirt, corn stalks, etc...) pile up, the wheels will rotate over the trash pile and continue going vs raising up the implement from the ground. but with field implements the tractor is not rolling over piles of stuff, the piles of stuff are happening due to ground engagement and tearing up the field and causing the piles to be created between pulling unit and the trip wheels / roll over wheels / beam wheel setup.

i realize there are some folks that run ATV's and hip/hop over logs on there trips out into the forest to have fun. and i could see the walk beam / wheels being a benefit to those folks possibly. but i am guessing those folks more out there just running there 4 wheelers / ATV having fun, jumping around, taking sharp corners, spinning tires, trying to take steepest incline they can take, etc... maybe you are this person.

if you were planning on smaller diameter tires vs a single larger tire diameter. i might see walk beam / wheels as something.

ya trying to talk ya out of the walking beam/wheel design. good old leaf spring axle setup been around for ages.

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with above said. sounds like ya got a plan down and finding your parts already to see the idea through *thumps up*

 

[Stimw]

You might want to look at Torsion Axles.
They mount to the frame so there is no drop down but you have the strength going all the way across.