I want to know all of the maths concerning this scissor mechanism!

[Maglatron]

so the plot thickens!! I'll post about it sometime tomorrow thanks

 

[Delta Prime]

That is what happens when soil has been added to your garden...

so the plot thickens!!

 

[Alec_t]

If it helps, I'm attaching a LibreOffice spreadsheet for this. Delete the ".txt" part of the file extension.
Should be compatible with OpenOffice.
Dependent variables have formulae shown and their cells are protected.

 

[Maglatron]

thats nice of you!! I made a discovery but I'm not ready to share it with the world untill it's perfect, but I do have to say Mr Alec_t, you have been an invaluable resource in my findings. watch this space!

 

[Maglatron]

after the exel document that you spent you're time on, when you didn't have to I'm really greatful. I would like to share my findings but not in the public eye maybe we can have a private conversation!!??

 

[Maglatron]

I know it's a big ask but can you make another spreadsheet like you did that automatally updates with this template

 

[Alec_t]

What number post shows the exact mechanism your spreadsheet refers to?

 

[Maglatron]

Not sure of the exact post but this is the mechanism that the spreadsheet refers to. So I have something I would like to talk to you about because this is not the finished product, there's a couple things I'd like to put forward! can we have a private chat?!?

 

[Maglatron]

????

 

[Maglatron]

What number post shows the exact mechanism your spreadsheet refers to?

do you understand it - the spreadsheet and the corrosponding diagram?

 

[Alec_t]

I understand the drawing, but it seems to me there's a major problem or two with it. As the weight falls the flywheel will be driven clockwise, but as soon as the cam tries to lift the weight back up again the flywheel would have to instantly reverse direction. That ain't gonna happen, given its huge inertia! Also, that flywheel will take considerable time to get moving when the weight falls, so the weight will fall slowly. In the meantime the cam is still rotating, so the cam follower won't stay in contact with the cam.

 

[Maglatron]

nope the flywheel is on a "spag" or "freewheel" same as the back wheel of a bike!! the freewheel is what allows you to pedal backwards when you're moving forwards, the wheel continues to turn this concept is fundamental

 

[Maglatron]

I understand the drawing, but it seems to me there's a major problem or two with it. As the weight falls the flywheel will be driven clockwise, but as soon as the cam tries to lift the weight back up again the flywheel would have to instantly reverse direction. That ain't gonna happen, given its huge inertia! Also, that flywheel will take considerable time to get moving when the weight falls, so the weight will fall slowly. In the meantime the cam is still rotating, so the cam follower won't stay in contact with the cam.

thanks for looking at it though It seems you get the part where the block accelerates the flywheel!

 

[Maglatron]

are you able to write up that spreadsheet? can you visualize the parts in the table and relate them to the drawing?? thanks also it would take about a 2 minute to get it to speed 2pi rad/s (60 rpm or just 1 turn per second) when accelerating at 0.05rad/s^2 so we skip this acceleration part and speed it up via another component - a starter motor at this rate 2pi rad/s the block takes a second to fall

 

[Alec_t]

at this rate 2pi rad/s the block takes a second to fall

.... in which time the cam rotates 1/4 turn and the cam follower is out of contact with the cam..

 

[Maglatron]

are you able to write up that spreadsheet? can you visualize the parts in the table and relate them to the drawing?? thanks also it would take about a 2 minute to get it to speed 2pi rad/s (60 rpm or just 1 turn per second) when accelerating at 0.05rad/s^2 so we skip this acceleration part and speed it up via another component - a starter motor at this rate 2pi rad/s the block takes a second to fall

I understand the drawing, but it seems to me there's a major problem or two with it. As the weight falls the flywheel will be driven clockwise, but as soon as the cam tries to lift the weight back up again the flywheel would have to instantly reverse direction. That ain't gonna happen, given its huge inertia! Also, that flywheel will take considerable time to get moving when the weight falls, so the weight will fall slowly. In the meantime the cam is still rotating, so the cam follower won't stay in contact with the cam.

very good! so do you know what a differential is and how it works? there are three shafts going into the diff one stays constantly turning, picture a remote controlled car when you hold one of the rear wheels still, then the other moves! the motion takes the path of least resistance so if one of the shaft has a brake disk on it, you can control when the cam turns simply by applying the brake, the cam is heavier than a brake disk so when the brake is off, that shaft is the shaft that will turn, applying the brake forces the cam to turn! and if you control the cam to turn when the weight gets to the bottom of its drop then ... watch @ time 4.12 if you wait till the weight has dropped then put on the disk brake on the diff for 2 seconds that solves that problem!! I'm thinking abit further ahead now and will be using arduino to controll the timing of the disk brake but there is even more to this that I want to tell you about because that is not the full design yet after all it's a simple mockup in paint

 

[Alec_t]

Sorry, but I haven't found the time to update your spreadsheet. I think you have all the maths you need now to do that yourself, using my spreadsheet for guidance as to how formulae are used in spreadsheets..

but there is even more to this that I want to tell you about because that is not the full design yet

This project is going way beyond considering the maths of the scissor mechanism, as per the thread title, and with no end in sight. I regret I don't really have the time to take this further. But let us know how the final design works out.

 

[Maglatron]

thats ok I was just explaining so you understand where I'm going with it, to be polite. I have already finished the machine on paper and thought it would be rude not to fill you in on what I've found because of you're input and the fact that you were so nice to provide that spreadsheet. but if you don't want to know then thanks for your time - you have helped me with the parts I needed to know, but if you could, do you recon you could do that spreadsheet? it's not necessary because I shouldn't be changing any of the variables any way but would be wicked okay thanks Mr Alec_t would really have like to work with you someday!

 

[Maglatron]

perhaps I could open a new thread with a fitting title what would you call it? I'd give you £15 a spreadsheet!! they'd be another 2 after that inculding the one you did thats £60 okay do I need to unlock boxes to see the formula? thanks

 

[Maglatron]

thanks I learned about the scissor mechanism and how it relates to the cam, this project won't be up and running for a LONG while but I will check back when it's going thanks again peace and I'll get pics