dump bed drops down

[AKKAMAAN]

Is it fixable? Do you have a picture of one done correctly? How far out of horizontal does it have to be? What about a shorter ram of similar strength and drop down the lower end (being careful not to bottom out?)

If you keep current cylinder, and mount a second similar cylinder, reduced diameter very possible, in the nose of the trailer. That will help to control both forces and the lowering speed. This second cylinder can not med pinned into the trailer. When the current cylinder "takes over" this front cylinder will disconnect from the trailer.

This 2nd cylinder shall be connected with a "T" to the line to the current cylinder.

This will of course slow down the start of the cycle.
With this arrangement, you can also replace the current cylinder with a smaller diameter cylinder.

A one way flow control needle valve is still a good idea to control/maintain a SAFE lowering speed.

 

[1claydude]

Thanks so much! This is a real help! I am sold. Now I need to work out some details. I'll have to measure to see what size ram extension I need (with some overlap.) I am guessing that a 2 foot throw will be more than enough. Any recommendation on who's hydraulics to buy? I could use some help on the lower mount and should I have a pocket of some sort at the top? It seems uncomfortable to assume that the ram will be in the right spot for the return trip if I don't guide it in some way. Maybe a combination skid plate and angle iron. Do you still need a video? All thoughts greatly appreciated !

 

[AKKAMAAN]

Thanks so much! This is a real help! I am sold. Now I need to work out some details. I'll have to measure to see what size ram extension I need (with some overlap.) I am guessing that a 2 foot throw will be more than enough. Any recommendation on who's hydraulics to buy? I could use some help on the lower mount and should I have a pocket of some sort at the top? It seems uncomfortable to assume that the ram will be in the right spot for the return trip if I don't guide it in some way. Maybe a combination skid plate and angle iron. Do you still need a video? All thoughts greatly appreciated !

hahaha...I am happy to sell this idea to you!!
Cost?? A video when you are done with your rebuild!!!

Good luck!

ps. No video needed now, since you are already "sold"...LOL

 

[1claydude]

No problem, you'll get pictures and a video. You really have been a great help!

 

[wdchyd]

Akkamaan,

I've seen short nubby cylinders added to Ladder Fire Trucks using this same arrangement.....adding 2 single acting cyls ( or d/a using bottom port only) added at the frame with short stroke and larger bore dia will do basically the same as you describe without the larger cyl in the way........the base end securely mounted near the rear pivot pins and the rod end not connected to the frame (used for just the initial lift)......

You could use maybe a 3 or 4 " bore with a 4 or 5 " stoke.......it would new a flow control as you said to control the down speed and tee them to the main cyl...........

The results would be the same...........

 

[1claydude]

How much PSI in each of the two scenarios? 5x12 bed, two 3500# axles, max load 5000#. Also, I picked up a "basket" of Moss Rock yesterday that weighed 3009 lbs (with skid and wire cage.) I saw no difference in the lifting action (like there was no weight at all) and no difference in the sudden drop if I held the remote on the way down. How come the really flat triangle formed by the two points on the cylinder and the hinge of the bed has no visible effect through the range of motion going up and is the exact opposite going down? Would it be a different story if I put 5000 lbs on it?

 

[wdchyd]

Probably with a heavier load it would struggle to lift the load with that geometry......the added cyls for the beginning of stroke (both senarios) would add to the lifting strength while starting and help to slow down the velocity of the oil on the last bit of stroke going down ( the flow control valve can be tuned to your liking)

If you were to put a hyd guage on the pressure line while lifting a load, you'd see that it will take alot more pressure when it starts lifting and gradually the pressure will fall back the higher it goes....with the same load on it....

The extra "Kicker cyl(s)" would probably be MORE needed for the down but will be an added benefit in the lift cycle.....

 

[AKKAMAAN]

How much PSI in each of the two scenarios? 5x12 bed, two 3500# axles, max load 5000#. Also, I picked up a "basket" of Moss Rock yesterday that weighed 3009 lbs (with skid and wire cage.) I saw no difference in the lifting action (like there was no weight at all) and no difference in the sudden drop if I held the remote on the way down. How come the really flat triangle formed by the two points on the cylinder and the hinge of the bed has no visible effect through the range of motion going up and is the exact opposite going down? Would it be a different story if I put 5000 lbs on it?

The "secrets" about dumping a bed like this are many.
1. Where is center of gravity of the bed and load combined?
2. Where is the cylinder affix point to the bed?
3. Where is the cylinder affix point to the trailer frame?
4. Where is the hinge point between bed and trailer frame?
These things will determine the size of the load (Force), the cylinder have to overcome.
5. The bore diameter (piston area) will then determine the required pressure to lift bed.
6. While bed is pivoting during the dump cycle, the effective cylinder force will change. The way your current design is, cylinder is least effective when bed is all the way down., and most effective when cylinder is fully extended (square to the bed). That means the highest pressure is required at the start of the dump cycle.

This drawing illustrates the complexity of forces and distances on a design like this. What ever your actual numbers are, everything can be calculated.
The most interesting during the dump cycle, happens within the yellow shaded area. I leave it open for discussion.