Question - to any and all Math Majors

[BLUEKNIGHT911]

#1. - I'm starting here because this has the most coverage and I know it will get moved to Off Topic, so please no re-criminations ...Thank you ..........#2.- I won't get into ALL the measurements and weights involved to achieve what I need - " UNLESS " someone can actually provide an answer to the problem .........#3. What I want to achieve is this : on my 917 project car, which has been cut in half ....is to raise the rear half from horizontal to vertical ( ie. open the back half for access to the motor )..... I started with Gas Struts ( because I had some ) but they won't work because the Struts provide Constant pressure ( ie. if something gets lighter, the struts will accelerate very fast )..... I can get Torsion springs in sizes to fit ... with lift capacities from 80lbs to 320lbs. ...these will fit on the rear hinges (?) ......... So if you can help me out it would be GREATLY appreciated.....either in a post or PM ........ Thank you ....Mike ...... PS, the rear is already hinged ( using Rod ends & 1/2 in bolts ) and I have lifted it to vertical successfully, so I know it works .......... PPS, my Albums have many pics of the project so far - more to come

[Joel The Biker]

https://www.firgelliauto.com/collect...near-actuators

Make it so it lifts using electric struts. Constant speed, strong, you control how high/low, and they will hold it open while you work on motor. And its very cool!!

[ARtraveler]

In my other life, I was an accountant. Not enough math to help with what you need. So....I am watching.

[canamjhb]

My tiny mind doesn't have any mathematical answer. Using your gas struts by themselves would make lifting progressively faster as you mentioned. Any thought about using a progressive spring in conjunction with the struts. The spring action would have to be calibrated to counteract the strut action to provide a smooth and even lift.....?

[Vader]

use some actuators. Like this..https://youtu.be/Ft4Kq2fnM0g

There is an episode of My Classic Car which featured a custom car builder and his creations..You can fast forward to the 12 minute mark, but I suggest watching the whole episode. Its rad.
https://youtu.be/HqRQ4qV9cHk

[BLUEKNIGHT911]

I just want to THANK all those who have posted in a POSITIVE manner ........ I knew I could count on the Spyderlovers community ........... If there are more idea's out there please post or PM me ....... Mike

[UtahPete]

https://www.firgelliauto.com/collect...near-actuators Make it so it lifts using electric struts. Constant speed, strong, you control how high/low, and they will hold it open while you work on motor. And its very cool!!

That would be cool, for sure.

[UtahPete]

... PPS, my Albums have many pics of the project so far - more to come

Here's a link to Mike's albums, including this project; http://www.spyderlovers.com/forums/a...=blueknight911

[IdahoMtnSpyder]

https://www.firgelliauto.com/collect...near-actuators

Make it so it lifts using electric struts. Constant speed, strong, you control how high/low, and they will hold it open while you work on motor. And its very cool!!

Thanks for that link. I'll have to look at it in depth later but it looks like they just may have what I've been looking for for years to move my kitchen pantry cupboard sections, 2' w x 3' d x 6' h, in and out with power. They move pretty easily by hand but I want to make them handicap friendly!

[Culpjp]

Have you looked at gas struts, but not using very heavy ones. Just enough to assist in lifting, but not enough to raise it in its own. Like the hatchback on a car. If I unlatch it the hatch won't raise very much on its own, but it helps take the effort from lifting.

[BLUEKNIGHT911]

Have you looked at gas struts, but not using very heavy ones. Just enough to assist in lifting, but not enough to raise it in its own. Like the hatchback on a car. If I unlatch it the hatch won't raise very much on its own, but it helps take the effort from lifting.

Thanks for responding ,( my thread said " I started with GAS STRUTS ) And I have tried a few different gas struts...I'm lifting 170lbs ...It's almost 5 ft long ....I used different strength and different length ....at different points along the frame and body ...... What I found was : once the body got to middle ( of the lift ) it accelerated so much, that I burned my hand that was holding the rope ( to prevent damage ) ...... the Torsion springs ( at $16.00 for as many as eight if I need them ) increase in strength as you lower the object ( up to their max rating ...40lbs ea. or less depending ) ....When you raise the object the spring is at Max strength and gets less as you raise the object.....so when the body is almost vertical the spring is giving no assist and actually prevents it going further ....... Mike

[Spyder_Cowgirl]

Mike ... Math was my minor; but it has been way too many years since I have used calculations to be of much use to you (I know, not helpful). However, it occurs to me that you might have some success in tapping the mechanical engineering knowledge of the group.

Just a thought .... good luck on finding method that suits your needs .... Ann

[BLUEKNIGHT911]

Mike ... Math was my minor; but it has been way too many years since I have used calculations to be of much use to you (I know, not helpful). However, it occurs to me that you might have some success in tapping the mechanical engineering knowledge of the group.

Just a thought .... good luck on finding method that suits your needs .... Ann

Thanks , I wish I could change the Heading but I can't seem to do it ..................Mike

[BoilerAnimal]

What is the greatest weight being lifted. Can't figure anything without that. Also, what does the weight decrease to?

[BLUEKNIGHT911]

What is the greatest weight being lifted. Can't figure anything without that. Also, what does the weight decrease to?

The rear half body weighs 170lbs. it is 5 ft. long and it balances in the middle at 2 1/2 ft..... The hinge is 8 inches in from the rear edge ..... so some of the weight is actually a bit of a counter-balance ...... it operates from zero degree's to 87 degree's ( almost vertical ) ....I weighed it at the front and it 63lbs. when lifting to vertical at approx. half way it becomes easier ( lighter ) to lift ( this is why the Gas Struts don't work, because you need a very High PSI strut to even begin to lift it when it is at zero, so at mid-lift you have to restrain it or it flys up ).... The torsion springs would be attached at the Pivot bolt at the hinge ...which is actually a ROD END with 1/2 inch bolts, the springs fit the 1/2 inch bolt and have 4 inch extensions, they are designed with one leg horizontal and the other at 90 degree's ....PS McMaster-Carr is the seller and they are listed under Torsion Springs in their catalog .... I can get them in 40lb ,28lb and 21lb in a size ( .666 actual Max bolt diameter ) for a 1/2 inch bolt ( the 1/2 bolt size is what I have to use, this cannot be adjusted ).....soooooooooooo if you can provide any info it would be much appreciated ....Thanks .... Mike

[IdahoMtnSpyder]

The rear half body weighs 170lbs. it is 5 ft. long and it balances in the middle at 2 1/2 ft..... The hinge is 8 inches in from the rear edge ..... so some of the weight is actually a bit of a counter-balance ...... it operates from zero degree's to 87 degree's ( almost vertical ) ....I weighed it at the front and it 63lbs. when lifting to vertical at approx. half way it becomes easier ( lighter ) to lift ( this is why the Gas Struts don't work, because you need a very High PSI strut to even begin to lift it when it is at zero, so at mid-lift you have to restrain it or it flys up ).... The torsion springs would be attached at the Pivot bolt at the hinge ...which is actually a ROD END with 1/2 inch bolts, the springs fit the 1/2 inch bolt and have 4 inch extensions, they are designed with one leg horizontal and the other at 90 degree's ....PS McMaster-Carr is the seller and they are listed under Torsion Springs in their catalog .... I can get them in 40lb ,28lb and 21lb in a size ( .666 actual Max bolt diameter ) for a 1/2 inch bolt ( the 1/2 bolt size is what I have to use, this cannot be adjusted ).....soooooooooooo if you can provide any info it would be much appreciated ....Thanks .... Mike

How high is the body? Where is the bulk of the weight in it, at or near the bottom, or higher? Based on the numbers you've stated you need something on the order of 300 lb-ft of torque to begin the lift. As it gets higher the center of gravity moves horizontally closer to the hinge thus reducing the torque needed to keep it moving. Now, if say the body is 3' high and the C.G. is maybe 1' above the bottom then when the body is up at something like 60° the c.g. is actually right above the hinge. Moving it further then puts into the position where gravity starts to pull it on over before you get to the 87° point.

If you can come up a better number for where the center of gravity actually is then it would be easier to figure out what the load is throughout the entire rotation.

[BLUEKNIGHT911]

How high is the body? Where is the bulk of the weight in it, at or near the bottom, or higher? Based on the numbers you've stated you need something on the order of 300 lb-ft of torque to begin the lift. As it gets higher the center of gravity moves horizontally closer to the hinge thus reducing the torque needed to keep it moving. Now, if say the body is 3' high and the C.G. is maybe 1' above the bottom then when the body is up at something like 60° the c.g. is actually right above the hinge. Moving it further then puts into the position where gravity starts to pull it on over before you get to the 87° point.

If you can come up a better number for where the center of gravity actually is then it would be easier to figure out what the load is throughout the entire rotation.

PM sent .....Thanks ...........Mike

[BoilerAnimal]

You say the rear half weighs 170 lbs. Is that the actual weight of the body or is that the weight that is lifted from the rear end of the rear end? All joking aside, we need to know the amount of weight that is being lifted at the beginning and the amount of weight that is to be lifted, or held, in the open position.

[BoilerAnimal]

To clarify, the weight calculations need to be made as it will be lifted attached to the hinges. I need to go now, got to ryde! Will check back later.

[BLUEKNIGHT911]

You say the rear half weighs 170 lbs. Is that the actual weight of the body or is that the weight that is lifted from the rear end of the rear end? All joking aside, we need to know the amount of weight that is being lifted at the beginning and the amount of weight that is to be lifted, or held, in the open position.

The 170 lbs is the total weight of the rear half ( the part we are dealing with ) .... I just weighed the internal metal support Cradle at 28lbs( plus body = 198 lbs total ) ... (this will be bolted to the body, it has the hinges - rod ends ) 90% of the cradle weight is past the Rod ends ...so it actually is a counter weight for lifting measurements ......when all is attached and in place, it only requires 68lbs of force to start the lift towards up-right

[viperryder]

There are motors that are called stepper motors. The armature has 360 separate individual steps, so you could move the back a total of any increments of 360 degrees. They can be run off of 12 volts, jus purchase them that way. You could use one or two depending on how you mount them, Good luck.

[IdahoMtnSpyder]

The 170 lbs is the total weight of the rear half ( the part we are dealing with ) .... I just weighed the internal metal support Cradle at 28lbs( plus body = 198 lbs total ) ... (this will be bolted to the body, it has the hinges - rod ends ) 90% of the cradle weight is past the Rod ends ...so it actually is a counter weight for lifting measurements ......when all is attached and in place, it only requires 68lbs of force to start the lift towards up-right

That's 68 lbs straight up, right? How far from the hinge is that?

[BLUEKNIGHT911]

That's 68 lbs straight up, right? How far from the hinge is that?

Yep, of course it's not really straight up ..... it follows an ARC because the hinge is stationary to the car frame ...... the Hinge / Rod ends are 8 inches in from the absolute rear end ..... Mike

[Spyder_Cowgirl]

Thanks , I wish I could change the Heading but I can't seem to do it ..................Mike

Mike …. edit the post and go to "advanced" …. you can change the heading there (at least I have in the past). ….. Ann

[IdahoMtnSpyder]

Yep, of course it's not really straight up ..... it follows an ARC because the hinge is stationary to the car frame ...... the Hinge / Rod ends are 8 inches in from the absolute rear end ..... Mike

I should have said at the start of the lift it's straight up. How far from the hinge is that lift point. The distance from the hinge to the lift point times the upward force gives you the torque the spring will have to exert to have zero lift force. If the lift point is at the front end of the half body I think you'll want to size the torque spring so that you have maybe 10 lbs lift required to open the body. That will minimize any bouncing of the body over bumps, etc., which will happen if the spring is strong enough so that zero force is required to start the lift. That is unless, you have a solid snug lock to hold it down.