OP
powerstroke444e
Veteran Member
I put the correct numbers on your drawing hope that helps. All measurements down were from center of top pin
Superduty dump build
- Thread starter powerstroke444e
- Start date
- Views: 20104
LD1
Epic Contributor
That helps a bunch. When I get a second, I'll calculate it.
But where did the 32" you mentioned come from. I see you changed that to 1'
It does make a little more sense now though. So the total be length is 10'6"??
OP
powerstroke444e
Veteran Member
32inch was about how far the 2 cylinder pins are apart IE Adjacent side of the triangle
LD1
Epic Contributor
Well, I got around to crunching some #'s
And it looks like you are going to have WAY more dump than you need:thumbsup: even @ 1500psi
If your measurments are accurate, the following is what I came up with:
The "effective" angle of the cylinder (due to the rear pivot placement as previously mentioned) is 20.2 degrees. The Sin of that is .345 In otherwords, you are using 34.5% of the cylinders force to dump the bed.
@ 2500psi, that is ~16,900 lbs of lift
@ 1500psi, that is ~ 10,150 lbs of lift
BUT, since the cylinder is mounted a good bit ahead of the center of the bed, that increases the mechanical advantage. By my calculations, its about a factor of 1.9:1
SO....
@ 2500psi, you have a lift force @ the center of ~32000lbs
@ 1500psi " " " " " ~19241lbs
That is not taking into effect any weight over that 6" of tail either that would reduce the effort needed to dump. :thumbsup:
And if the cylinder will extend to 90", you will have a dump angle of 45.2 degrees. Which should be more than enough to dump most things.:thumbsup:
And in an earlier post, you made a comment about liking to calculate these things, well....you are right. I enjoy doing this sort of thing. So thanks for sharing.
And I know you have already started building, but I'll throw you a link to the dump bed I built about a year and a half ago. It may give you some Ideas, or may not.
http://www.tractorbynet.com/forums/projects/158521-turning-1985-dodge-into-real.html
Keep us posted through the build
And it looks like you are going to have WAY more dump than you need:thumbsup: even @ 1500psi
If your measurments are accurate, the following is what I came up with:
The "effective" angle of the cylinder (due to the rear pivot placement as previously mentioned) is 20.2 degrees. The Sin of that is .345 In otherwords, you are using 34.5% of the cylinders force to dump the bed.
@ 2500psi, that is ~16,900 lbs of lift
@ 1500psi, that is ~ 10,150 lbs of lift
BUT, since the cylinder is mounted a good bit ahead of the center of the bed, that increases the mechanical advantage. By my calculations, its about a factor of 1.9:1
SO....
@ 2500psi, you have a lift force @ the center of ~32000lbs
@ 1500psi " " " " " ~19241lbs
That is not taking into effect any weight over that 6" of tail either that would reduce the effort needed to dump. :thumbsup:
And if the cylinder will extend to 90", you will have a dump angle of 45.2 degrees. Which should be more than enough to dump most things.:thumbsup:
And in an earlier post, you made a comment about liking to calculate these things, well....you are right. I enjoy doing this sort of thing. So thanks for sharing.
And I know you have already started building, but I'll throw you a link to the dump bed I built about a year and a half ago. It may give you some Ideas, or may not.
http://www.tractorbynet.com/forums/projects/158521-turning-1985-dodge-into-real.html
Keep us posted through the build
Iplayfarmer
Super Member
Let's see if you and I get the same numbers.
The final tilt of the bed is 44.2 degrees. This is based on the following assumptions...
-The ram is 32" pin center to pin center closed with a 58" stroke (90" pin to pin extended)
-The bed pivot hinge is 9 feet behind the top pin and 1 foot below the top pin.
-The bottom ram pin is 17" below the top pin.
And here are my only slightly less crappy drawings.
Attachments
Iplayfarmer
Super Member
Oh, look. You beat me to the calculation.
We're within a degree of each other. I guess that counts as a match.
I didn't run any force numbers, but I can agree that the force is plenty. Of course our "effective angles" are different as we are going about it from different directions.
I asked my neighbor who is a retired calculus teacher about the problem of finding the torque needed to dump a loaded bed. He couldn't offer any help. I can't believe that this is that rare of a problem.
LD1
Epic Contributor
The 32" pin center to pin center is where we are deviating a bit.
He said that his measurement was a rough one.
BUT using his #'s of 38" for retracted cylinder length AND the rear pin being 17" lower than the front, basic A2+B2=C2 for a right triangle puts that # @ 33.98" and that is what I used.
Try that and see if you come up with the 45.2 like I did.
PS, those are MUCH better drawings than mine. What program is that and does it calculat the angles for you as well??
I calculated it long-form using that "green" line I refered to earlier. The line drawn between the rear pivot and the RAM-BED pivot. Using the 9' and 12" numbers he gave us, that makes that "green" line 108.66" long. The cylinder is 38" long. Using the rest of his measurments I was able to determine that the distance between the rear pivot and the base cylinder pivot was 74.188" long.
Those three sides make a triangle. and using the cosine law (C2= A2 + B2 - 2ABcosC) the angle between the 108.66 and 74.188 sides was 10 degrees.
Since those two sides DONT change through out the dump, they remain constant. BUT the 38" side increases to 90". Using cosine law again, that makes THAT angle change to 55.2 degrees. Subtract the 10 degrees that it started with and it comes out to 45.2.
BUt I could have made an error in my calculations OR rounding, etc.
Iplayfarmer
Super Member
One of the reasons for the delay in my response was because I had originally figured the whole thing based on 38" pin to pin center. I went back and refigured after I saw powerstroke's response detailing 32" pin to pin measurement.
The program is sketchup. It's a free download. You'd like it, LD1. It will calculate the angles in that it will tell you how far you have rotated an object. I always figure the angle of motion in a situation like this by drawing two circles. One circle is centered on the ram base pin with a radius equal to the extended length of the ram. The other circle is centered on the articulation joint with a radius equal to the distance between the articulation point (dump joint in this case) and the ram rod end pin. (See attached picture.) Where the two circles meet is the extent of travel. When I move the bed in the picture to meet the extent of the travel I watch the indicator telling me how far I've rotated it.
Two very different methods came up with answers that are the same within the margin of error considering estimated numbers. That's good data.
One question about your calculations... The law of cosines only works on right triangles. There's no guarantee that the final triangle created between the bed length, extended ram, and the hinge to ram base is a right triangle. What am I missing?
Attachments
LD1
Epic Contributor
You are missing that the law of cosines works on ANY triangle.
Its the pythagorean theorem that only works on right triangles.
And the pythagorean theorm is simply the law of cosines re-written.
The law of cosines (good for ANY triangle) is C2=A2 + B2 - 2AB(cosC)
and IF angle C is 90 degrees: the cosine of 90 is 0. So that completely cancels out the 2ABcosC and thus you are left with just C2=A2+B2
Law of cosines - Wikipedia, the free encyclopedia for a reference
OP
powerstroke444e
Veteran Member
I think next time I have a math problem I will pm one of you two:thumbsup:.
I figured I way over built this but wanted it heavy enought to put an a bigger truck down the road some day. One would guess that I wont have to worry about over loading the bed just the truck.
I ordered rest of the lights and picked up the wire to wire it. If all goes well should get it mostly done this weekend. Any good photo's of tailgates out there??? I think I have it figured out but just have build it.
LD1 you dump looks good would like to have that 4x4 when I am offroad as this thing needs a chain and tractor to get it to move offroad.
I figured I way over built this but wanted it heavy enought to put an a bigger truck down the road some day. One would guess that I wont have to worry about over loading the bed just the truck.
I ordered rest of the lights and picked up the wire to wire it. If all goes well should get it mostly done this weekend. Any good photo's of tailgates out there??? I think I have it figured out but just have build it.
LD1 you dump looks good would like to have that 4x4 when I am offroad as this thing needs a chain and tractor to get it to move offroad.
