work platform on truss boom

[zzvyb6]

On my JLG, there is a tap into the hydraulic lift line which feeds the work platform pitch angle. The pitch cylinder is sized such that a horizontal work platform position is maintained no matter what the elevation. Mine also has a yaw angle rotator so that I can square up the platform angle with the wall of a building or sneak around a limb as necessary.

As long as you are comfortable with your lift, one or both of these features could be added. I'd also suggest adding some baseboards aound the base of the platform. Sometimes you have tools and cans of gas/oil/paint, etc. that you don't want to roll overboard.

 

[Renze]

Yes, we did add a baseboard just above the floor. I needed that when my brother leaned me out of reach and the relief valve blew over, dropping me down 3 meters at a velocity that gave me time to stop the chainsaw, put it behind the baseboard and hold on to the rail. Unless you try to reach too far by putting the boom horizontal, being in the bucket with the boom 60 degrees up, while driving, the boom lift feels more secure than the commercial lifts i have used professionally, because the construction is stiffer (though more labour intensive to build) than commercial booms made of single rectangular tubing.

As said, hydraulically the critical point is at ground level with the boom flat on the ground, when the depth of fall is little (designed that way) Once upright it is very stable, especially with the tractor on duals for a wider stance.

 

[muddstopper]

It would be so simple and cheap to make this lift safer, it just doesnt make sense to me not to do it. Three obvious methods are , orifce fitting, flow control and counter balance valves. Orfices would be the cheapest method. Simply weldup a fitting and drill a hole in it to control oil flow. Problem with this method is that altho you can control the flow of oil out of the cyl, if a hose blows, its still going to fall, only in a semi control method and speed of extend is also effected. If you choose to use a flow control in a meter out arrangement, you have adjustability in the rate of fall, but its still going to fall if a hose blows, By also having a check valve bypass, the extend speed can be wide open. Third method would be thru the use of a counter balance valve. Using this method, it would actually take a set amount of hydraulic pressure to make the boom fall. This pressure is adjustable so you can control speed of fall in event of hose failure, have full speed retraction under normal situations, and has a checkvalve bypass that allows full speed extention. A good counter balance valve would cost around $100 so it just dont make sense to take chances with ones health or life.

 

[Citydude]

I agree with you totally, bailing wire is great stuff. Bailing is much better than duct tape. You can build anything with bailing wire. My dad could fix a flat tire with bailing wire. In my opinion bailing wire should take first place over the wheel for man's greatest invention. As far as building it out of wood, I could do that. Ships have sailed around the world made of wood, so I'm sure I could get 20 feet in the air with it. However bailing wire would not be my first choice to fasten it all together.

I for one, appreciate your humor! Thanks for the chuckle!

 

[bigdeano]

Muddstopper,

I've had problems with jerkiness when lowering weight with a counterbalance valve. Do you know of a type or brand that works smoothly? Thanks.

 

[muddstopper]

A counter balance valve works very much like a relief valve, except the CBV will have a check valve bypass to allow oil free flow in one direction. It keeps oil from return until a set pressure value is met. Jerkyness could be a result of having the CBV pressure values set to high or having a valve with to high a cracking pressure. Cracking pressure being the amount of pressure needed to start letting oil bypass at a restricted flow rate. As pressure builds, the valve will continue to open until it reaches a full flow letting all oil pass thru the valve. There are more than one type of CBV. The common type is internally load sensing. By internal sensing, it is actually checking pressure between the actuator and the return. A externally sensing CBV will check for pressure on the inlet using a pilot port. If I had a CBV acting jerky, I would try adjusting the pressure settings first to see if that helps. Your settings should be just high enough to control the loads being suspended. If you only need 500psi to support a load, and the valve is set at 1000psi, then the valve is going to be opening and closeing as pressure rises and falls.

Using flow controls is another valid option. Usually only one flow control is used and it is installed to control flow at the outlet side of the actuator, called metering out. You can also install a second Flow control at the inlet to control how much fluid is entering the cylinder, called metering in. Because of the base end and rod end of a cyl have different surface areas. using two flow control allows adjustment of both the flow IN as well as OUT to make the cyl extend and retract at the same speed in either direction. Again, not all flow controls are created equal. A plain flow control isnt a very good flow control, as the pressure differential changes at the inlet and outlet side of the FCV, the flow rate will actually change. A more accurate FCV to use would be one that is also pressure compenstated. There are many flavors of PCFCV, and they are internal as well as external sensing types.