Slow retracting ran

[Sfrankland]

Just about have my dump trailer finished and noticed that the ram is quick to extend but once the second stage has retracted the first stage is really slow. I had to take the ram apart to fix a stripped out fitting last night and everything on the inside of the ram was like new. The ram has the same travel speed as it did before I took it apart.

I have attached a video in case I am not clear.

http://www.youtube.com/watch?v=76t_9RNUTuU

 

[medic0648]

If it's a single acting cylinder it's the lack of weight to the surface area of the cylinder. No load up= fast. No load down = slow.

 

[Sfrankland]

I guess I will have to live with it then, it's for personal use around the yard so I can wait. My buddy suggested that once the trailer had a load in it she would retract faster, then I reminded him the whole purpose for it going up was to dump the weight that was in it.

 

[J_J]

Is there an adjustment on the pump for the return fluid.

I believe a solenoid opens a port but there might be a screw to adjust return flow.

If the cyl port is say 1/2 in, then use all 1/2 fittings and hoses.

Check and see if any of the fittings are restrictor fittings.

Is slow return a big problem. The descent rate is based on gravity and weight of the bed

 

[Sfrankland]

The cylinder has non-restrictive 1/4" NPT fittings with 1/4" hose running to a 1/2" NPT hydraulic quick coupler tip. I can switch the hoses around and the up and down speed of the ram remains the same . I am guessing that the hose size won't matter if it is going into a 1/4" fitting or will it? The slow return is not a problem I just wasn't sure if it was normal or if I had something wrong with the cylinder.

 

[BukitCase]

I'm pretty sure your 1/4" fittings are the slowdown - I watched the video, and it gets slow when the largest section of the 2-stage ram is collapsing - this is because you have a LOT more fluid to displace in the larger of the two stages than in the smaller one.

This is also one of the benefits of a multi-stage cylinder for a dump - you have the greatest "push" where it's the hardest to get started, when the push points and cylinder are nearly in line. As the cylinder raises, your geometry changes and requires less push to keep moving. My 6-yard dump truck has dual 2-stage cylinders, and I can't put enough heavy or wet stuff in that thing to slow it down :=)

If you decide it matters, I'd upsize the smallest fittings/hoses in your system and see what happens. But you're right, the smallest diameter in the system will dictate the speed, so everything would need to be the larger size in order to see much (if any) change.

Keep in mind that a cylinder with 1.4 times the diameter of another cylinder, will require TWICE the flow to move the same distance. (Area of a circle is the formula) -

Sooo, from the cylinder's viewpoint you need to move a LOT more oil to move the larger section of the 2-stage the same distance -

but the good news is, from the FITTING/HOSE point of view, the same formula applies - so if your smallest fitting is 1/4" and you go to 1/2", you will increase the flow by 4 TIMES. Just going from 1/4 to 3/8 will DOUBLE the speed that last half of the dump cylinder moves, assuming all other variables remain the same... Steve

 

[wdchyd]

1/4" hoses are pretty small for that application........don't forget the orifice size at the crimped fitting can be as small as 1/8" ID (or less) when you consider the stem pushed into the hose is 1/4" OD

 

[J_J]

I don't think you can ever achieve the same speed going up as going down as the forces are different.

You will be limited by the smallest orifice in terms of GPM and flow velocity.

 

[mick101]

I too have the same problem but it seems to have gotten worse with time. If I drive forward and "jerk" the trailer the smaller cylinder will close/open about a foot or so at a time. Surely, with the lever in the down position, if the ram closes a portion then it wouldn't open again. Also today I had it fully tipped , put the lever into the down position, left the tractor ticking over and 5 minutes later it came down in one fast movement. Fortunately there was nobody nearby. The ram is old.

 

[Sfrankland]

My ram just failed. It was an aluminum cylinder and the the cylinder expanded where the cap screwed in. Needless to say I had a big mess to clean up in the driveway.