Can any master give me some idea

sporty

thanks a lot t oyour reply danger, you make me more understand on skipping follower, but is it too troublsome for a person to screw the bolt to follow and unsrew it frequently? or is it have other mechanism to substitude the screw bolt to lock the thread?
Now i am more understand to the linear actuator, actually i need the mechanism for analysis for my project, my project is to design a mechanism for analysis so if i using actuator, it is only one things and no mechanism to analysis in my report.I propose wheelchair seat lift to my lecture because i saw a lot of leg broken patient, aging people like my grandma in my home , i wish to help them too beside can finish my project.
Before this, i bought a ratchet with rack and pinion mechanism, it is a device use to hold tightly the line to tighten the box. so i thinking to modified it by put the rack to a rectagular hollow bar and fixed the bar on side of wheelchair fixed also the pinion ratchet too. and that rectangular bar i open a slot at one of its side to pin the linkage with rack. so they can move together to lift a human. but i am not sure is it can work for my mechanism . with help in reduce the applied force by patient.

and my linkage also got problem, because it is unsymetric scissor linkage. different length for the leg. and one of the linkage is both end moveable. So i don't know wheather it will work ?
. Further Question is in my picture.
you are very kind danger. thanks for your advice. and your helpfulness.

Danger

It's not so much that I'm kind, as it is that I love an opportunity to both assist someone and exercise my mind at the same time. And believe me, most of my ideas are way off base. I have no education, so everything that I come up with is something that I would do with available tools and supplies. Anything that I've ever built was based upon car parts, typewriters (my favourite), VCR's... I believe that there was part of a goat involved in the last one...
Anyhow, back to the chase...
Rather than using the set-screw situation that I mentioned originally, the main thought was to utilize an over-centre cam with the "follower" built into it. I mentioned the set-screw only to illustrate the point about not needing full thread engagement.
I really am too burned out right now to post any more, but I'll get back to you tomorrow.

sporty

thanks a lot Danger, have a nice dreams..

Danger

I haven't given up on you, pal... but have also not yet slept. I promise that I will get back to you as soon as I am able. I don't even feel tired, but I know that I am impaired by endorphins and lactic acid. My cozy little bed is very attractive to me right now. I will get back to you.

Danger

Jeez, but it's been a while. Sorry... I got sidetracked a lot. Still, I've been thinking on this quite a bit. It suddenly struck me a couple of weeks ago that there might be some way to accomplish the design using roller chains, but I haven't figured it out yet.

Know_seeker

i think that u should consider using a mechatronics system for ur purpose. i think this is what is meant by linear actuator in the previous post. To implement this u will need some type of a controller , a electrical motor(actuator) there (are DC Motors , Stepper Motors , Servomotors , u can choose among them depending on their price ,torque, and wether u accuracy is important in ur system , i think for ur application a stepper motor is suitable ), and u will need a switch to activate the system.
now a electrical motor usually outputs a rotational movement so to convert it to linear movement u could use rack and pinion (this is only an idea ).
for controller u could check arduino microprocessors because it is easily to deal with and they provide Pulse Width Modulation signal for the motor.
i hope that i helped