Tractor FEL Crane *Update*

[alltoys]

How many trusses could you lift at a time?

Reason why I ask is because you could build say 3 on the ground then hoist them on to your project already assembled. Would cut time down on top the building. Then it would be just a matter of correct spacing and nailing them down.

In the construction world we build the roof on the ground then hoist it up with a crane. A lot faster and safer than one truss at a time.

 

[PhilCase]

How many trusses could you lift at a time?

A good question. I do not know the answer.

If I decide it "feels" comfortable enough, I "might" try two at a time, which would match some of the load tests I have performed.

I suspect the limiting factor would be the hydraulics of the FEL or tipping. I'd hate to find out by losing a pump or cylinder .... as well as a batch of trusses.

 

[westcliffe01]

Your numbers are a bit off, since the bucket cylinders are "pulling" instead of "pushing", so the rod diameter reduces the cross section quite a bit. If it really has 4" cylinders then the pressure goes up to 250psi (still low) if it has 3" cylinders it is closer to 485 psi and for 2" close to 1200psi.

Now those are static loads (truss stationary). Add in 1g of acceleration and those numbers double (when you lift the truss, or stop lowering it, or drive the tractor across uneven ground). I did guess the weight of the pipe to be around 60lb and that weight is cantilevered out about 7 feet at least, so that adds a bit to the load too.

Doing some rough trig, it looks like the angle of the cables to the pole will be about 9.5 degrees and the 2 cables will have to support a load of about 2000lb, or about 1000lb each (that includes the hardware store turnbuckles). Again, with the load stationary. Double or triple that number to take into account acceleration or deceleration.

Frankly, you could have bought a quick attach plate (about $150), used the same pipe, and triangulated it with 2 -1"schedule 40 pipes. All 3 pipes could have been welded to the quick attach plate and none of the weld joints would have the slightest problem holding 2-4k lbs. and if you did tip it back too far, it would not fall on you either.

Was just reading last week of a moderator on the hearth.com forum who had an accident while felling a tree and spent a few weeks in intensive care and is now a paraplegic (no motor control below the chest). No matter what you think you can save, your system needs to be more inherently safe and the hardware store fasteners are a deathtrap.

Ya know I had to try... Lets see...4" cyl area = Pi X r(sq) = 12.56 sq inches.

300lbs at 18 ft = 5400ft lbs (8' from bottom of cyl to end of bucket.)

5400 lbs /12.56 sq in = 430 psi...2 cyls...215 psi???

A 2" cylinder will be 1719 psi assuming my numbers are correct. but the weight will be between two cyls. so... 860 psi???

The valves would get the full pressure...right???

Take into account I struggled in physics.... These numbers are by no means to be assumed to be correct. I was origionally concerned with the geometry as the tractor weight is probably close to that with loaded tires.

 

[mbohuntr]

Thanks Wescliffe01, I was only considering the larger arm cylinders, and not the bucket tilts. My bad... I also did not anticipate any acceleration because he is using a winch which should minimize it. For the life of me, I could not remember how to calculate tension, and to tell the truth, that is what I believe is the weak spot in the design. I might have used chain instead of cable. Much stronger. Hopefully, they lift away from people.

 

[PhilCase]

I could not remember how to calculate tension, and to tell the truth, that is what I believe is the weak spot in the design.

FWIW, the 1/4 inch steel cable I'm using claims a load rating of 6000 lbs, if that helps. That would be per cable, not sure about the clamps. Also the boom pipe ended up weighing in at 75 lbs. (3/16 thick 3.5" OD pipe)

As indicated in an earlier post I do intent to safety cable around the turnbuckles, as they do feel like the weak spot.

 

[PhilCase]

Frankly, you could have bought a quick attach plate (about $150), used the same pipe, and triangulated it with 2 -1"schedule 40 pipes.

I would have went that route, but my FEL is not quick release.

 

[westcliffe01]

The problem is that keeping acceleration below 1g is near to impossible. And usually you would want your system to have reserves several times the expected load.

I sure as h^&* wouldn't want to be lifting 3000lb + with one of those junk turnbuckles. If they fail, it will all be over in an instant. Truss falling, boom swinging to the "good" side with the load until the pipe comes off the tooth or strikes something laterally... Cable whipping back towards the operator looking to impale him with what is left of the busted turnbuckle... Not a good mental image. And if the load falls and is then suddenly arrested, expect to find the tractor doing a wheelie on the front axle. Suddenly applied loads can magnify the base load by 10x.

People do many things, but getting hurt is no joke. I have seen peoples lives change in an instant and you can't take it back.

 

[mbohuntr]

I was worried about the weak spots in the system, mainly the very weak turnbuckles, clamps, counter weight and the one tooth mount. IMHO, If you replace the cable system, and limit the picks to one truss at a time, you limit the risk . As they are, the clamps and buckle will fail long before the cable. Like Wescliffe pointed out, those cables are holding both a vertical force, as well as a lateral force. If one should fail, things are going to get ugly real fast. I would place the trusses on the walls upside down,one at a time, and then flip em up. This should limit the exposure of people on the walls. Use long leash lines to guide the picks, keeping the ground help clear as well. As you said, the tractor will not be moving. If you place the trusses inside the structure, place the tractor with the boom at a fairly steep angle, and only pick with the winch, you limit the danger. You also have no protection from the boom coming back over at you if you are too steep.
I was once asked to build a hoist to pick floating docks out of a lake. The owner stated that the docks only weighed 400-600 lbs, so the system was designed to lift 1000 lbs. At 10ft from the pole, the static force was 5 tons!!One guy cable to a screw in anchor!!!. When I asked why he put a winch rated at 1 ton on the beam, he stated that he might occasionally lift friends sailboats onto trailers!!!!!! As he was the customer, I didn't question his sanity, I suggested he consult an engineer before any lifts take place to limit his liability. There were more than a couple of issues there, but the point being that the system should be designed to easily lift twice the expected max load, and incapable of lifting more than the max load. I think the cable system, bucket cyls. and counter weights are your weak spots. We brought in a log loader to lift our trusses. One at a time, then flip. I think the safety police have had our say. I guess since Wescliffe pointed out even more risks, I'm not comfortable with the set-up. I am no engineer, but I feel you are pushing the limits. Good luck, and be safe!!! Do everything you can to protect everyone. It might be better to pass on this one...

 

[PhilCase]

I sure as h^&* wouldn't want to be lifting 3000lb + with one of those junk turnbuckles. If they fail.......

As previously mentioned, the plan is to cable around the turnbuckles just for this contingency. Your point is valid.

Thanks for the feedback.

 

[PhilCase]

Good luck, and be safe!!! Do everything you can to protect everyone.

Thanks for the good wishes. I feel pretty confident with the testing done, that the system will perform as intended, but will certainly operate as if it might not. Appreciate all the feedback.

Work begins in the morning, pics/videos early next week.