DIY budget Bridging ladder project

[Secretsponge]

well, looking at Bridging ladder costs and designs I started thinking that a set could be built at a reasonable price/weight by comparison. I've seen a few people try this with both wood and angle iron, which pretty much does well as a sand ladder, but ultimately fails in the bridging department... what I've made is not perfect as of yet, but for the one already made, I'm very pleased.

construction is made out of 2 four foot sections of the larger unistrut, should measure 1.75", with 2 sections of eight in a quarter inches of the same unistrut on either end (its whats left of the 10' section they come in)... that's all about 20 there

then I took 3 sections of 2" angle with a quarter wall and used them as more runners in between the 2 sections of unistrut.

on the back side I welded 2" by 1.75" sections of quarter flat bar, at each support runner, on the 4 foot sections of unistrut to keep them from flaring open.

total cost at this point is about $25, and some welding wire.

the total weight is 25lb...

got a little over zealous and threw our bobcat at work on top of it, just one, not a pair. The bridging ladder held up great till he hit the middle, then he bent. I'm pretty happy with that, being as the curb weight is 7,030lb on this bobcat, and the front end is being held by one bridging ladder (they're mount wheels, both on the front ...next batch I may use 3 sections of unistrut, instead of just 2...either way...

the pictures...




I know hes no longer in the center, panicked and backed up a little.

 

[Buddha.]

Unistrut, was thinking about making a roofrack out of that stuff but i didn't know what it was called.

 

[Secretsponge]

It's on the Home Depot website, strut... Also superstrut and a few different names. Would work great as a rack I think.

 

[HARDTRAILZ]

Good idea. That struff does work well for a bunch of stuff.

 

[millerfish]

Looks promising. I would consider using structural square tube in place of the unistrut. The open U shape is inherently weaker that square. And from my experience with the unistrut it just is not that sturdy.

 

[Secretsponge]

Looks promising. I would consider using structural square tube in place of the unistrut. The open U shape is inherently weaker that square. And from my experience with the unistrut it just is not that sturdy.

I decided to use the unistrut because of the open U shape makes it lighter, but I knowing it would be weaker and more prone to splaying out is why I added tabs on the back side, reinforces the open end, and gives it a grabbing lip. for the ground side. For a first attempt I'm pretty happy with it, minimal bending with the entire front end of a bobcat resting on top...from Cat their 7,030 pounds without the bucket or occupant, so I'd say it was about 8,000 give or take...my Pathfinder with a maxed out weight is 5,150, so about 3k lighter, and would be only on one corners weight, not 2
won't know for sure till I build some more of them, but worked better then I expected.

 

[millerfish]

With an empty bucket I would think most of the weight of that cat is on the rear wheels. I don't think the unistrut can sustain 4K lbs per piece. The majority of the strength of any structural member with vertical load is at the top and bottom. This is why I beam is so darn effective. If you close the open U in the unistrut the entire length you will increase the strength drastically.

 

[Secretsponge]

I understand going the full length would make it much stronger, but it would also increase the weight a good deal, which is what I'm trying to avoid, heavy weights and high cost, building a ladder for a tank would be a simple feat if weight was not a concern... weight wise, the Cats seem to be fairly evenly distributed with the bucket on, back heavy without, or with some fork carriages, and nose heavy with the jack hammer. I understand what your saying, and I will be adding more structure on the next go at it, but little by little to stay light.

 

[Secretsponge]

really just wish I had tried it with my pathfinder before moving to heavier equipment.

 

[millerfish]

I'm with you. I also have been banging around ideas for ladders. I think we need use the strongest material economically possible. Uni strut is 1010 or 1011 steel (I think) most standard square tube is 1018 a bit stronger. If we step up to 4130 you could reduce weight and be a lot stronger. Do you know how much the uni strut weighs per foot? Compare that to 1.25 sq tube x .090 wall might be pretty much the same weight.

 

[Ducky's Dad]

I'd suggest forgetting the unistrut and looking for some i-beam material. If you can find a profile that is deep and narrow (high web, narrow flange), that will maximize the deflective strength. It compromises lateral deflection, but that is usually not an issue in a bridging situation. The longer the ladders are, the deeper the web will need to be. If you have a spool gun, think about aluminum.

 

[Secretsponge]

The unistrut is about 2lbs a foot, the 4130 1.25 x 0.120 wall is only 1.4lbs, so that is quite a bit lighter and definitely going to be stronger, but the cost would drive up considerably.

 

[Jeremy P.]

There is a lot more to consider when welding aluminum vs mild steel if you want to maintain material strength.

 

[Secretsponge]

I'm not sure I understand what you mean, I've never had the opportunity to weld aluminum...mild, stainless, galvanized, and even Iron, but never aluminum. that's kind of why I want to stick to the steel route.

 

[Ducky's Dad]

never aluminum. that's kind of why I want to stick to the steel route.

Steel is cheaper, simpler, and heavier. If you don't have access to a spool gun or experience with aluminum, stick with steel. I still like the i-beam idea to increase resistance to vertical deflection if you want bridging ladders. For a given net weight of steel, orienting the steel vertically rather than wasting some of it on unnecessary horizontal members will give a higher strength-to-weight ratio, but only in one direction.