Adjusting the PH springs - Page 8

boywonder · 07-20-2018, 08:42 AM

The next attempt was to completely eliminate the helper springs. This may have several advantages.

Gas springs provide some nice controlled damping in both directions, and the spring noises are reduced when the top is raised and lowered. One downside of gas springs (at least readily available off the shelf units) is that they have a somewhat fixed/very low spring rate. Another downside is that they wear out over time.

Here is the next attempt.....2 stage booster with a long stroke 15lb spring and two short 90 lb springs in parallel for 180 lbs when the roof is fully down....threaded into black delrin blocks for extra slipperiness....

This also worked OK but still there is not enough load at the end of the roof travel when the roof is down. I'm really trying to get the roof to raise easier and lower easier/more controlled.

**BroncoHauler** · 07-20-2018, 08:52 AM

If you keep this up, we're going to have to upgrade your BoyWonder status to full Batman status.

Herb

boywonder · 07-20-2018, 09:03 AM

Quote:

Originally Posted by BroncoHauler

If you keep this up, we're going to have to upgrade your BoyWonder status to full Batman status.

Herb

...wearing these tights gets old.....the goggles fog up....and the cape gets in the way......

BUFFALO · 07-20-2018, 10:46 AM

I remember reading a thread where someone used air cylinders in place of the helper springs. I believe they were 300 lbs apiece. Can’t remember or find the thread.
But anyhow, it wasn’t enough force. It would’ve taken much more because the force it takes to push those bars forward is so great.

So thinking about that, I am wondering if the gas struts could be mounted on the lift bars. One point on the front bar and one point on the rear bar and both points on one side of the scissor bolt. That way the force of the struts is being used in a more vertical manor instead of the horizontal pushing which requires so much more.

That make sense to anyone?

boywonder · 07-20-2018, 12:31 PM

Quote:

Originally Posted by BUFFALO

I remember reading a thread where someone used air cylinders in place of the helper springs. I believe they were 300 lbs apiece. Can’t remember or find the thread.
But anyhow, it wasn’t enough force. It would’ve taken much more because the force it takes to push those bars forward is so great.

So thinking about that, I am wondering if the gas struts could be mounted on the lift bars. One point on the front bar and one point on the rear bar and both points on one side of the scissor bolt. That way the force of the struts is being used in a more vertical manor instead of the horizontal pushing which requires so much more.

That make sense to anyone?

Yes. The issue is that since both springs are horizontal you need lots of force at the end of the travel when the roof is down and much less when the roof is up.....it's a trigonometric function for all of you math heads. When the roof is down the crossbars are about 4-5 degrees off of horizontal, so there is very little spring force acting in the vertical direction.

That's the basic problem....if the crossbars were completely horizontal when the roof is down, no amount of spring force will raise the roof, since there is zero vertical force component.

BUFFALO · 07-20-2018, 12:50 PM

That makes sense. So coming up with enough force where the helper springs are is the best answer.
Can wait to see what you come up with!

boywonder · 07-20-2018, 03:28 PM

Quote:

Originally Posted by BUFFALO

That makes sense. So coming up with enough force where the helper springs are is the best answer.
Can wait to see what you come up with!

The helper springs have a linear spring rate.....and the crossbars need a highly non-linear spring rate (much more at the end of travel and much less at the beginning-when the roof is up) to be reasonably balanced......that's the goal here......

ShuttlePilot · 07-20-2018, 03:56 PM

Quote:

Originally Posted by boywonder

Yes. The issue is that since both springs are horizontal you need lots of force at the end of the travel when the roof is down and much less when the roof is up.....it's a trigonometric function for all of you math heads. When the roof is down the crossbars are about 4-5 degrees off of horizontal, so there is very little spring force acting in the vertical direction.

That's the basic problem....if the crossbars were completely horizontal when the roof is down, no amount of spring force will raise the roof, since there is zero vertical force component.

I have pondered this whole raising a manual top things also. I've got as far as the above description and then thought if I can't create an ideal force in the stock location, change the angle. I've thought about gas/air cylinder/contained springs in different mounting points on the van to the scissor mechanism, bar to bar in the scissor, bar to bar with offset to get more desirable angle of force, bar to roof with offset mounts. Then I remind myself why I'm not in the engineering department and go back to sleep.

I hope you find a solution boywonder and thanks for sharing.
- Eric

boywonder · 07-20-2018, 04:07 PM

Air cylinders are cheap and interesting....especially for those of us who have on-board air......never thought of that.....

That being said, I'm quite satisfied with a manual top, but it would be nice to have it go up and down easier.

**BroncoHauler** · 07-20-2018, 04:48 PM

Quote:

Originally Posted by boywonder

Air cylinders are cheap and interesting....especially for those of us who have on-board air......never thought of that.....

That being said, I'm quite satisfied with a manual top, but it would be nice to have it go up and down easier.

Would the air cylinders just be for initial assist, or to assist holding the top up? I would hate to count on no leak-down issues for the top to stay up.

Herb