hydraulic cylinder (trig-angle calculations)

[Willl]

So far, this analysis will probably result in a cylinder larger than you need.

You say that like it's a bad thing.

 

[LD1]

well upon further research and doing some equations I have concluded that the sin method is the correct one.

The amount of lift force at the bed vs the cylinder is directally proportional to the lift at the bed vs the lift of the cylinder. What I mean by this is that if the bed raises 3" for every 1" of the cylinder, the lift capacity is 33% of the cylinder capacity.

using cosine law (c^2=a^2 +b^2 - 2abcos@) I was able to determine how much the bed raised for the first .01" of cylinder movement.

Using a simple set up with a 36" cylinder mounted @ a 36" pivot point and 12" drop(19.47*) with a cylinder with a straight force of 24500lbs, using the sin method, would be 8166lbs @ the pivot and 8166 x 36/48 = 6125 @ 48" midpoint of the bed.

I have attached pics but using only the given information you can find the angle of the bed from the rear pivot (on the left in the pic) to the lower cylinder pivot.

By extending the cylinder .01" it causes a .04774* angle change. sin(.04774) x 48 = .03999, which is how much the bed moved vertically @ 48".

.01/.03999= .250, which is the ratio of cylinder movement to bed movement, which is proportional to force.

.250 x 24500 = 6125lbs lift @ 48", the same as the sin method.

 

[quarencia]

If you need to lift 8000 lbs in the bed, you do not necessarily need to generate 8000 lbs of lift at the cylinder attach point. Where the rear pivot and cylinder attach are relative to the load define the lift requirements at the cylinder attach. As several here have said, you must compute moments of all forces around rear pivot point. I can't tell from what I've read where you intend to attach the cylinder and the rear pivot.

Would be best to mount rear pivot as far forward as the frame will allow. Would also be best to attach the cylinder to the bed as far forward as possible. See drawings...

View attachment Lift Attach.pdf

Additionally, the lower you can mount the rear pivot relative to the lift cylinder attach point, the more lift capacity you will get. See drawings...

View attachment Lower Rear Pivot.pdf

 

[yellowfordtruck]

dont know if this is the right place but im making a flat bed for my truck and i want it to dump, im going to run a pto off my transmission if this drawing will help can anyone help me with this or steer me in the right direction?

 

[LD1]

You should really start a new thread. this one is 4 years old.

But No one can give you the distance you are looking for cause there are too many variables. How much angle do you want to dump, how much force do you need it to have, what angle are you mounting the cylinder....

Best to start a new thread IMO, give a little more detail, and we will try to help.

 

[Iplayfarmer]

dont know if this is the right place but im making a flat bed for my truck and i want it to dump, im going to run a pto off my transmission if this drawing will help can anyone help me with this or steer me in the right direction?

View attachment 335860

I'm with LD1... Start a new thread and you'll get much more complete answers.

The short answer is to mount the base of the cylinder 39" in front of the hinge for a 45 degree bed tilt (further back = more tilt), but this makes a lot of assumptions. Post a new thread answering more of the questions listed below and a handful of characters will give you all the help you need.

How long is the cylinder when retracted?
How far do you want the bed to tilt?
What's the overall length of the bed?
How much weight do you want to dump?
How much lower can you mount the base of the cylinder than the rod end? (lower is better)

Do me a favor, though. Post back here when you've started the new thread so I'll know to follow it.

 

[ovrszd]

This appears to be a classic example of Google Searching a particular hydraulics question and getting directed to an old thread on TBN. Hopefully he'll take your advice and start over with a fresh thread. I in no way can figure out the answer he needs. But I really enjoy reading the contributions.

 

[9will79]

hmm, 8 years later after the last post, some things running through my mind... what about mechanical advantage? ie,... where on your dump bed are you placing that end of the cylinder? Seems in my head that a 1000 pound equally balanced load, might require a 500 pound starting lift if it was a telescopic cylinder on the front end... however, if your mount was in the middle, would the lift require 1000 pounds to start? or 75% towards the rear of the bed, would that not require a 1500 pound force to lift (or some factor of mechanical advantage), adding on top - the angle of the cylinder...? I wonder how it turned out... heehee

 

[LD1]

Yea zombie thread back from the dead. The original thread concluded 12 years ago.

Mounting points and cylinder angles were all accounted for.

Everything turned out well, and I hauled and dumped ALOT of wood with it. Sold it maybe 7 years ago and now have non-dump flatbed and a dump trailer. Among other things

hmm, 8 years later after the last post, some things running through my mind... what about mechanical advantage? ie,... where on your dump bed are you placing that end of the cylinder? Seems in my head that a 1000 pound equally balanced load, might require a 500 pound starting lift if it was a telescopic cylinder on the front end... however, if your mount was in the middle, would the lift require 1000 pounds to start? or 75% towards the rear of the bed, would that not require a 1500 pound force to lift (or some factor of mechanical advantage), adding on top - the angle of the cylinder...? I wonder how it turned out... heehee