Need Help Mechanical double lid lifter

[tyroman]

nvn,

Very clever arrangement... however, at least one problem would arise when the doors are opened beyond 90 degrees with the spool mechanism. The twine(?) would lose contact with the pully at H and the doors would then have to be manually closed (at least until they reach 90 degrees or less).

Another potential problem might occur if the doors are opened and closed repeatedly by hand... could this cause the twine to become fowled?

Also, if this double spool arrangement is mounted outside of the long 1" tube, (allowing access to the twine for maintenance) the assembly will occupy a lot of the available 2" space and a right angle drive for motorization might not fit.

cybertron,

You might think about what you said in post #67;

"the door will sit at the lowest point of the 3'' height of the tubing.That not a major problem to change."

See attached sketch. The "possible solution" shows a new strip of wood attached to the right door which would over-lap the left door, covering the gap.

 

[cybertron]

tyroman

Why do I need to rethink post 67

In post 67 the doors do lay at the level of the plywood base and that's 3'' below from the top of the shorter tubes to the base do to the spacer added for your rack and pinion design mechanism this is why I add the spacer for the stability and for added strength in your rack and pinion design as you suggested for the added height for the rack and having a stronger design. At this time which is not being considered anymore as a design, but might of worked.
I haven't heard from you for sometime now about this proposed design.So I'm asumming this is not an option anymore.

In your latest 3D image of where the doors sit (they do sit right at the level of the plywood base): and leveled with the bottom of the longer tube
as indicator in your last image at the bottom part of your sketch.


Now. Why would i need to cover the gap between the two doors.There must be a gap between the two leaf doors for expansion and contraction and so the doors do not hit each other when opening/closing.
So why would I need to add a strip of wood on the right side of the door laping over the left door to cover the gap.There could be a problem with adding a strip to the right side of the door, say the left door opens before the right door dose and hit the right door by 1sec asummuing the left door opens first.
Explain the reason why this wood strip is to be added on the right side of door, and for what purpose.
I'm asumming this is added so nothing falls through the gap or for aesthetics.

 

[nvn]

When the doors are opened beyond 90 degrees, ... the twine(?) [cable] would lose contact with the pulley at H, and the doors would then have to be manually closed (at least until they reach 90 degrees or less).

tyroman: Very observant. Good catch. And I notice my previous drive mechanism in post 94 exhibits this same problem.

 

[tyroman]

Corrected diagram for discussion...

 

[cybertron]

tyroman

What do i need to do and need to know about this image in post 110.

And are you still working on the rack & pinion design Yes or No.



nvn

Have you're come up with any new ideas or changes for the motor drive mechanism in your latest revised design in post 104.

 

[nvn]

cybertron: Don't worry about the image in post 110. It is a free-body diagram by tyroman of the left-hand door.

My latest concept is shown in the attached diagram, below. Not to scale. The red part is a U-shaped plate. The bottom of the U is underneath linkage bar BH. Only if the doors are being opened by the motor, then the two uprights of the U actuate the green compression springs, beginning when the door angle is 85 deg. The red U-shaped part does not engage the springs when opening the doors manually. Let's see if tyroman has comments.

You can use right-angle, helical bevel gears to rotate the drive mechanism, if you wish. You can mount the linkage mechanism inside or outside the square tubes, whichever you prefer. If the mechanism is mounted outside the square tubes, the spool can be quite narrow.

 

[cybertron]

cybertron: Don't worry about the image in post 110. It is a free-body diagram by tyroman of the left-hand door.

My latest concept is shown in the attached diagram, below. Not to scale. The red part is a U-shaped plate. The bottom of the U is underneath linkage bar BH. Only if the doors are being opened by the motor, then the two uprights of the U actuate the green compression springs, beginning when the door angle is 85 deg. The red U-shaped part does not engage the springs when opening the doors manually. Let's see if tyroman has comments.

You can use right-angle, helical bevel gears to rotate the drive mechanism, if you wish. You can mount the linkage mechanism inside or outside the square tubes, whichever you prefer. If the mechanism is mounted outside the square tubes, the spool can be quite narrow.

OK. Let's see what tyroman thinks.

I really don't get what the red part dose in both images or how its connected to the tube.

 

[tyroman]

nvn,

Another clever design... but I'm not sure how cybertron is going to find the spring/bracket assembly "off-the-shelf", though it reminds me of some spring-loaded cabinet door latches I have seen.

When the door is lifted manually from the closed position, tension in the cable would be released and your linkage bar BH would immediately drop down and subsequently the two uprights of the U would pass below the springs.

This would work fine; however, if I understand the mechanism correctly, the springs will supply a tensioning force to maintain cable contact with the pully at H when the motor moves the door from 90 to 100 degrees. Would the force they exert (when the motor is stopped at 100 degrees) then not be sufficient for the springs to independently tip the door back to the 90 degree position from which it would fall closed of its own weight? This assumes that the motor (including its gear box and any right angle drive connected) can be driven in reverse via a force exerted on its output shaft... an assumption which is necessary for manual and motor operation to be independant. I suppose it might be possible (if the springs are sized very carefully) to find the fine line between operation as you envision it and the scenario I describe.

My comment above reminds me of something cybertron has said in an earlier post which has troubled me;

#58 "The motor will hold the mass of both doors at ANY ANGLE as indicated."
and,
#33 "When one side of the small bar is pull up from the close position the opposite side starts lifting at the same time assisting the opposite side and rotates to ANY ANGLE between zero degrees to 100 degrees."
NOTE: I added CAPS above to highlight the phrase of concern.

If, for example, cybertron wants to be able to open the doors to 60 degrees by hand or motor and have them remain there without further input, then some sort of counterbalance system or arbitrary frictional force will need to be introduced into the design.

 

[cybertron]

nvn,

Another clever design... but I'm not sure how cybertron is going to find the spring/bracket assembly "off-the-shelf", though it reminds me of some spring-loaded cabinet door latches I have seen.

When the door is lifted manually from the closed position, tension in the cable would be released and your linkage bar BH would immediately drop down and subsequently the two uprights of the U would pass below the springs.

This would work fine; however, if I understand the mechanism correctly, the springs will supply a tensioning force to maintain cable contact with the pully at H when the motor moves the door from 90 to 100 degrees. Would the force they exert (when the motor is stopped at 100 degrees) then not be sufficient for the springs to independently tip the door back to the 90 degree position from which it would fall closed of its own weight? This assumes that the motor (including its gear box and any right angle drive connected) can be driven in reverse via a force exerted on its output shaft... an assumption which is necessary for manual and motor operation to be independant. I suppose it might be possible (if the springs are sized very carefully) to find the fine line between operation as you envision it and the scenario I describe.

My comment above reminds me of something cybertron has said in an earlier post which has troubled me;

#58 "The motor will hold the mass of both doors at ANY ANGLE as indicated."
and,
#33 "When one side of the small bar is pull up from the close position the opposite side starts lifting at the same time assisting the opposite side and rotates to ANY ANGLE between zero degrees to 100 degrees."
NOTE: I added CAPS above to highlight the phrase of concern.

If, for example, cybertron wants to be able to open the doors to 60 degrees by hand or motor and have them remain there without further input, then some sort of counterbalance system or arbitrary frictional force will need to be introduced into the design.

In post #58
I stated that do to the information that I gotten from the vender i purchased the motor from they stated the motor will hold both of the doors which is 20Lbs total which the motor would handle up to 75lbs in oz holding 75lbs the lid 1'' above the opening. So I'm assumming the the motor will hold the weight or mass of the door at the 0-90degs suggested by the vender.
In post #33 as stated But what I was try to say is..
The side that's lifting one door by the motor or by hand that the oposite side lifts up the other door at the same time do to the assistance of the small bar on on the other side of the lifter so both doors open and close from 0-90 or 0-100degs in unison...

Opening the doors from 0-100 degs is fine.
I don't think i would need to open the doors at 60 degree.

tyroman:Sorry If this troubled you. what I was stating is that the doors when opening at the angle of rotation from 0-100 degrees they open in unison and not stop at any certain angle but rotate thru the 0-100degree angle of rotation. if this makes sense.

 

[nvn]

tyroman: The spring force would be designed to be just sufficient to rotate the doors from 100 deg to 85 deg, which is much less force than the drive mechanism applies, and much less force than is applied when the doors are at 0 deg.

Good point regarding your comments in post 114. A motor with a built-in locking device would perhaps be required. When power is supplied, a built-in solenoid in the motor would disengage the locking device, allowing the motor shaft to rotate. When power is removed, the locking device would automatically retract to the default, locked position. Maybe the designer can find a motor like this; I do not know the details. Otherwise, locking a door open manually would be required, such as using a prop bar; however, this might be cumbersome. The designer can implement any operational details desired. It is up to the designer to work out the intricate details of the design.

 

[tyroman]

cybertron,

You said;
"I really don't get what the red part dose in both images or how its connected to the tube."

The red part is not connected to the tube, it is connected to link BH. As the motor raises the door, the red part engages the green springs which ARE connected to the tube. As the springs are compressed, they exert a force to the right on link BH, keeping the purple cable taut.

See my edit of nvn's sketch attached. Note; the solid green blocks represent the fully compressed springs with the door open to 100 degrees. Also, the upper part of nvn's sketch is the side view of the mechanism while the lower part is the same mechanism viewed from below.

You also said;
"Opening the doors from 0-100 degs is fine.
I don't think i would need to open the doors at 60 degree."

Good! A mechanism which would allow them to STAY at any position except 0 degs or 100 degs would be more complex, as nvn stated in his post #116.

In answer to your earlier question... no, I have gone no further with development of the double rack & pinion idea. As I have stated before, I feel that nvn's design will be cheaper, simpler for you to build and (potentially) more robust than the rack and pinion design. All that is needed is to come up with the way to motorize it.

 

[cybertron]

nvn

In post 105,104,and 112 are these drawings the final designs of the door mechanism including your motor drive mechanism concept in post 112. if not.Will there be any new changes.

In post 104 is this the final design door mechanism without the motor drive mechanism and if i construct this without the motor drive mechanism i would need to open the doors by hand. correct.

The design in 112 with the motor drive mechanism might not be as simple to build as i throught. That spring mechanism in the design is not a part i would beable to find off the shelf as tyroman mentioned, also the part that connects the spool to linkage (B) is a custom part which i got from two places who could make that part but its going too be very expensive to make about $300-$600 they will have to forge that part as a one piece item which I'm not willing to spend on one part.

The design in post 104 i think is doable and i think i might beable to construct it but without the motor drive mechanism in post 112 do to the parts which are not something that's going to be found off the shelf. I NEED a motor drive mechanism design that can be constructed with parts i could buy from hardware stores or online stores.
But don't get me wrong! the drive mechanism design in post 112 looks like a good design but its not an option that i would beable to biuld do to the motor driver parts

nvn do you have any other design options to drive post 104 with a motor but usig only parts i can get off the shelf.Not Custom.

Tyroman.

In your early designs could anyone of them be used that uses a screw drive be attach to my tubular lifter with nvn design in post 104. Without custom or hard to find parts. Any options.

 

[tyroman]

cybertron,

You ask;
"In your early designs could anyone of them be used that uses a screw drive be attach to my tubular lifter with nvn design in post 104."

If you mean "worm drive", no. The worm drive idea was discarded when it became clear that operation of the mechanism with a hand crank was not acceptable to you. There would be no other way to manually operate the mechanism if the motor is connected through a worm/worm-gear arrangement.

Among the various schemes I have offered, the "door-mechanism-05 (with motor).png" at post #83 would be my suggestion for motorization of nvn's design. However, it would require that his design be modified as follows;

1. mount the mechanism on near-side of long tube rather than inside
2. substitute a rack for his link BC

Also, my post #83 sketch contains no detail on the size or method of mounting or attaching the various components... Some further work would be needed before you would have all the info to buy and build;

1. The rack and pinion design strength calculations- [nvn or vendor]
2. The right angle drive or bevel gear strength calculations - [nvn or vendor]
3. The method of mounting the gear motor - [motor mount dimensions known only to you]
4. The method of attaching the various gears including a bearing assembly for the pinion gear mounted to the long tube - [follows decisions above in 1, 2 & 3]
5. Selection of rack guides/bearings to support link BC [follows decisions above in 1, 2 & 3]
6. Selection of link connectors for points A, B, C, and D [follows decisions above in 1, 2 & 3]
7. More?

Rack and pinion sets are available on-line, however they are not cheap. A set of appropriate size (strength) would need to be selected based upon nvn's calculated design forces.

I have attached a photo of a rack and pinion arrangement in a common bathroom scale for your information...

I understand from another thread that nvn may not have time in the next few weeks to visit PF... so, unless someone else comes to your aid on the points I've outlined above, you will have to continue to be patient.

Links to an on-line site with relevant equipment are listed below. This is for information only, so you can get an idea of what is available (and how much it may cost). Also see links I have provided in earlier posts.


http://www.sdp-si.com/index.asp

they sell gear motors;
http://www.sdp-si.com/web/html/Motors.htm
https://sdp-si.com/eStore/Direct.asp?GroupID=819
gears;
http://www.sdp-si.com/web/html/gears.htm
racks;
https://sdp-si.com/eStore/Direct.asp?GroupID=284
round racks;
https://sdp-si.com/eStore/Direct.asp?GroupID=501
https://sdp-si.com/ss/PDF/79001188.pdf
rack guides;
https://sdp-si.com/eStore/Direct.asp?GroupID=766
https://sdp-si.com/ss/PDF/78001137.pdf
linkage ends
https://sdp-si.com/eStore/Direct.asp?GroupID=1080

 

[nvn]

cybertron: The attached diagram, below, shows an alternate method, in which the axial springs are replaced by the green torsional spring. (If you use the torsional spring method, you will need a prop bar or locking pin to hold a door open, when opening the doors by hand.) You can use whichever method you prefer.

Yes, the linkage mechanism shown in post 104 is currently a final design concept. It has a motor drive mechanism shown in later diagrams, even though the motor drive mechanism is not shown in post 104. You can open the doors by hand or by motor.

The part that connects the spool to linkage B is a custom part...

The part connecting the spool to linkage bar BC is called linkage bar BH. Linkage bar BH is not a special part. It is relatively easy to make, and not expensive. It is simply two flat bars, a cylinder, and a pin.

 

[cybertron]

nvn


This torsional spring alternate replacement part, is it part of the hinge or a separate part that attaches to the hinge and will i beable to find this separate part or hinge from a online supplier.

Will this torsional spring be need if the drive motor mechanism attached to point BC linkage is not used as is in post 104. Or would i need to used the torsional spring no matter if the motor drive mechanism is used or not.

how would the cable be attached to the big spool to the smaller spool. if its attached to the in side of the longer tube its not going to be that simple to attach this inside the tube and how long would the cable need to be.The cable might not work correctly as suggested.this is my concern.Because there's always the problem getting the cable to work just right.

nvn
Can you LOOK into using the design in post 83 and make the modification but still use the design in post 104 with the required 104 design forces and calculations and suggestions as tyroman suggested in post 119.

 

[nvn]

The torsional spring is needed only if a motor drive mechanism is used. In general, you would probably purchase the torsional spring and hinge separately, remove the hinge pin, cut a notch for the torsional spring, then reassemble the parts. But how you do it is up to you. You can use any approach you prefer.

The cable can be attached in any way you prefer, and is relatively easy to attach. How you do it is up to you. The cable does not need to be an exact length. You want the cable to be longer than necessary, so that the cable makes approximately one and a half extra loops around the empty side of the spool when the mechanism is fully extended or contracted.

For the axial force in linkage bar BC, use the maximum linkage bar axial forces listed in post 104, paragraph 4.

 

[cybertron]

The torsional spring is needed only if a motor drive mechanism is used. In general, you would probably purchase the torsional spring and hinge separately, remove the hinge pin, cut a notch for the torsional spring, then reassemble the parts. But how you do it is up to you. You can use any approach you prefer.

The cable can be attached in any way you prefer, and is relatively easy to attach. How you do it is up to you. The cable does not need to be an exact length. You want the cable to be longer than necessary, so that the cable makes approximately one and a half extra loops around each spool when the mechanism is fully extended.

For the axial force in linkage bar BC, use the maximum linkage bar axial forces listed in post 104, paragraph 4.

nvn.

The axial force in linkage bar BC as stated in 104, paragraph 4. Dose this force have anything to with the tension and compression of the Torsional Spring and what the spring needs to conform to in holding the force on linkage bar BC. If not, Please explain!


Also in post 104 when the doors are at 0dgs (closed) coordinates A points in mm 10.00 and 29.60 these are two points where do these two points get attach to on the short tube at (A).

 

[nvn]

No. The torsional spring applies a small force only when the doors are opened greater than 85 deg. This torsional spring force is much smaller than the linkage bar forces when the doors are at 0 deg. Therefore, the torsional spring does not govern the design.

The location of a point is given as two coordinates (an x and y coordinate), as shown here.

 

[cybertron]

nvn.

Can't open the file in post 124 for some reason it dose not open. its a svg type of file, do you know what software that will open this program.Because i cannot open it.

 

[nvn]

The location of a point is given as two coordinates (an x and y coordinate), as shown here, or here.

 

[cybertron]

nvn


In reading the topic on two points as two coordinates in post 126, assumming that 10.00mm and 29.60mm are the two coordinates for point (A). In that, the ending edge of the the shorter tube to point A is 29.60mm and from the bottom edge of the shorter tube to point A is 10.00mm which gives you coordinates x and y for point (A).
If this makes any sense at all and my understanding from what i read from the site you posted in 126. Please if I'm wrong correct me. explain!

 

[tyroman]

cybertron,

Attached is a sketch which is my understanding from the figures nvn gives in post #104. I have used a screen capture from nvn's latest animation and added the coordinates and calculated lengths from post #104.

Hope this helps...

.
(PS; edits to correct post reference # and added detail to sketch)

 

[cybertron]

tyroman.

Thanks for clarifying this up for me.


OK. So, I was about (80%) correct on the coordinates of x and y for point (A) from reading the topic in post 126. I had the dimensions backwards, and had based the origin point from the ending edge of the shorter tube instead of using the center point of the longer tube. As you indicated in your edited sketch of nvn animated design.

So the origin point X is the center point of the longer tube. correct! And all coordinated points are based off this center point of the longer Sq tube. correct!

Points J and K are these coordinates for the hinges.

Which would be the best and simplest way to construct the mechnism to my sq tube lifter inside or outside the sq botom tube.

Also these questions might need to be answered by nvn, if you can't answer tyroman.
1. If i was to construct this on the inside of the bottom tube how long would i need to cut a narrow slit where points B and C Slide right to left when the doors open and close from 0degs to 90degs and also on the shorter tube on the left side where linkage AB will need to slide in the top of the longer tube what would be the dimensions for all these cut slots.
2. Will point D's brown plate pass through the end of the longer tube or would i need to cut a slot at the longer tubes end side.

 

[tyroman]

cybertron,

Glad my sketch was helpful... but I need to be sure you understand how a coordinate system is used.

Where you say;
"the origin point X is the center point of the longer tube"

I would say;
"the origin point (X = 0.00, Y = 0.00) is at the LEFT END of the longer tube, at its centerline"

nvn said in post #104 [with edits by me];
"The coordinate system origin is ... located on the left-hand end [X = 0.00] of the long square tube, at the tube longitudinal centerline [Y = 0.00]."

The location of any point on the drawing is described with TWO numbers... (X, Y).

Your inside / outside question has been around for a while... Is there a reason you would want to put the mechanism inside the tube? I can think of reasons to put it outside the tube (aside from the motor-drive issue) such as; ease of access for lubrication, repair or adjustment. Additionally, from my understanding of the off-limits restrictions, most of the mechanism (link BC with its bushings and connections to links AB and CD) will have to be assembled inside the tube BEFORE the long tube is mounted to its base. Would this present a problem?

Your final questions;
"Also these questions might need to be answered by nvn, if you can't answer tyroman."
will most easily be answered by YOU when you build the device (or better yet, when you make a simple cardboard 2D model of the mechanism before you build anything).

.