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- #21
Got Engineering Skills? (1 Viewer)
- Thread starter LandCruiserPhil
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see why I need help
Too many unknown variables to calculate I would think. I don't know if those lift cylinders are constant force the entire stroke or not? If not you would need to find out the force exerted at the part of stroke you are at now the height and angle you want, and then do the same with the new proposed lift cylinder.
But you would guess that if the equivalent lift was used that it would be about the same +- a couple inches, might be at 8" instead of 10" if you go 100lb 36", etc. the more vertical lift the lower that point would be.
But you would guess that if the equivalent lift was used that it would be about the same +- a couple inches, might be at 8" instead of 10" if you go 100lb 36", etc. the more vertical lift the lower that point would be.
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I don't know if I right but your numbers are wrong. You need to compare the collapsed lengths. Not sure but to get the idea
44.5" collapses to 22.25 (half) and 36" collapses to 18" (again half) so the distance changed when closed is 4.25" when you moved the top 10"
Not sure I understand the problem about length? If the bottom mount is 45" from the pivot and the top mount is 68" from the pivot that gives him 23" (actually a little longer because of the angle) for a 36" total length lift cylinder.
Going quickly to McMaster they have a 35.43" 100lb ball joint lift that collapses to 19.xx"
Going quickly to McMaster they have a 35.43" 100lb ball joint lift that collapses to 19.xx"
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You forgot to take into account mechanical advantage for a class 2 lever. It's all in the post above.
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- #27
IRRC its the amount of room I have to work with given the mounting points. To further clarify it has nothing to do with the spec of the strut. I do recall based on the struts spec I have enough room to avoid bottoming of the strut when closed.
Yes you should have just over 23" fully closed, and the 35.5" strut I found had a collapsed length of 19.xx" so shouldn't really be a problem.
Have you considered linear actuators? Even inexpensive actuators impart a tremendous amount of force, so you could use an even shorter stroke. Plus it would be pretty cool to mash a button and have camp set up. http://www.amazon.com/Stroke-Linear...21634746&sr=8-11&keywords=linear+actuator+12v
Yes, I did account for it. It is all in my previous post above.
I don't have a scanner to show my work right now, but, it would seem, but a rough calculation, 98lbs struts should be enough to hold the lid open.
I imagine the increments aren't soooo precise so maybe the next step is 100lbs?
If you make a triangle from your dimensions, the sides are 44.5(strut), 45(lwr strut mount to pivot), 78(pivot-upr strut mount).
This is close enough to 45, 45, 78. Luckily, this makes the acute angles 30degrees.
the current strut supplies 90lbs of force in this position. With some vector calculation that means 78lbs in the vertical direction. the horizontal distance from the pivot to the upr strut mount is ~67.5" or 5.625'. 78lbs x 5.625ft = ~440lb-ft of torque are required to hold the lid open at 30 degrees.
changing the strut open length to 36 inches and keeping the 30degree opening(limited by the shape of the tent sides) means the new sides of the triangle are 45, 36 and 67. the law of sines and some other trig is helpful to figure that out. to find the horizontal distance from the pivot to the new upr strut mount, its just cos(30)x67" = 0.866*67=58.1"=4.84ft. you know you need 440lb-ft of torque to hold the lid, so 440/4.84=~91lbs.
That is 91lbs in the vertical direction. Using some trig, you find the new angle of the strut rod is 111.3deg. Calculating the force vector at 111.3deg with 90.5lbs in the vertical direction gives 97.5lbs for the struts.
However, the new distance from the pivot to the upr support is 67" and the distance from the pivot to the lwr support is 45". That leaves a 22" difference. The new closed length is 23" so it doesn't work so well unless you move the lwr support by an inch towards the front. 100lb struts will have enough margin to allow for moving the lwr support by that inch.
I imagine the increments aren't soooo precise so maybe the next step is 100lbs?
If you make a triangle from your dimensions, the sides are 44.5(strut), 45(lwr strut mount to pivot), 78(pivot-upr strut mount).
This is close enough to 45, 45, 78. Luckily, this makes the acute angles 30degrees.
the current strut supplies 90lbs of force in this position. With some vector calculation that means 78lbs in the vertical direction. the horizontal distance from the pivot to the upr strut mount is ~67.5" or 5.625'. 78lbs x 5.625ft = ~440lb-ft of torque are required to hold the lid open at 30 degrees.
changing the strut open length to 36 inches and keeping the 30degree opening(limited by the shape of the tent sides) means the new sides of the triangle are 45, 36 and 67. the law of sines and some other trig is helpful to figure that out. to find the horizontal distance from the pivot to the new upr strut mount, its just cos(30)x67" = 0.866*67=58.1"=4.84ft. you know you need 440lb-ft of torque to hold the lid, so 440/4.84=~91lbs.
That is 91lbs in the vertical direction. Using some trig, you find the new angle of the strut rod is 111.3deg. Calculating the force vector at 111.3deg with 90.5lbs in the vertical direction gives 97.5lbs for the struts.
However, the new distance from the pivot to the upr support is 67" and the distance from the pivot to the lwr support is 45". That leaves a 22" difference. The new closed length is 23" so it doesn't work so well unless you move the lwr support by an inch towards the front. 100lb struts will have enough margin to allow for moving the lwr support by that inch.
Golgo13 makes 2 votes for 100lbs at 36"
I also really like the linear actuator idea. I believe the new RAV4 uses these for the rear lift-gate, so, in theory, you could get OE parts for it.
I've also been talking to one of the guys at work about how to adapt the electric opener and latch from a Sienna to the rear upper hatch on my 80. Doesn't really seem to be room enough for the latch unit, but we're not done playing with the idea yet.
I've also been talking to one of the guys at work about how to adapt the electric opener and latch from a Sienna to the rear upper hatch on my 80. Doesn't really seem to be room enough for the latch unit, but we're not done playing with the idea yet.
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- #35
Have you considered linear actuators? Even inexpensive actuators impart a tremendous amount of force, so you could use an even shorter stroke. Plus it would be pretty cool to mash a button and have camp set up. http://www.amazon.com/Stroke-Linear...21634746&sr=8-11&keywords=linear+actuator+12v
Cool idea but not enough room
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- #36
You guys have been a great help thank you!
Based on the results above I will be going with the following -
GSNI-3849-101
P1 force in lbs - 101.2
Extended length(EL) - 35.79"
Compressed length - 20.04"
Stroke(S) - 15.75"
Rod dia(D) - .39"
Tube dia - .9"
Based on the results above I will be going with the following -
GSNI-3849-101
P1 force in lbs - 101.2
Extended length(EL) - 35.79"
Compressed length - 20.04"
Stroke(S) - 15.75"
Rod dia(D) - .39"
Tube dia - .9"
OP started drinking Coors light and coupled with a vigorous workout routine didnt need mods after all.....
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- #40
Not installed
- too many irons in the fire I will definitely keep all posted on the final resultsThanks again to all for the help
