Stubby47's 6th CBC Entry - Blast Door

[Stubby47]

I looked at this the other day thinking a rack & pinion arrangement would be much smoother. Worth considering using mechanism out of an old PC CD/DVD drive. Built-in motor, rack & lifting device! The disadvantage being you would need approx 1.5 inches under the base. Use the eject button as an open/close button.

 

Thanks for the idea.

Maybe one issue would be the lack of length adjustment possible with the rack - if it's too short there's not a lot that can be done to extend it. Plus I need at least 4 doors (I might not have any on the ground level, still thinking about that), so that would need 4 ex-CD drive units. Also, I'm not sure what power or control these would need.

 

I'll be using servos for other (ok, non-visible) items, and I think I can get it to work more smoothly once the door slide is improved.

[riscosuser]

Thanks for the idea.

Maybe one issue would be the lack of length adjustment possible with the rack - if it's too short there's not a lot that can be done to extend it. Plus I need at least 4 doors (I might not have any on the ground level, still thinking about that), so that would need 4 ex-CD drive units. Also, I'm not sure what power or control these would need.

 

I'll be using servos for other (ok, non-visible) items, and I think I can get it to work more smoothly once the door slide is improved.

Control would be a simple momentary pulse, usually to earth, either by switch or electronics. Would need both 12V & 5v to be sure, plenty of cheap ex PC units out there. Current requirements low.

N.B. CD/DVD's can be scrappers as you're not interested in their normal use. I'd remove the laser assembly (with it's rather useful stepper motor worm drive) leaving just the frame and the drawer. Worth a play!

[Bergmann]

Why don't you use a wire rope? A servo with a double drum is enough. A drum wraps the rope and the second drum on, so you can open your door and pull. As a rope I use 0.5 mm rope from a radio.

[Stubby47]

Why don't you use a wire rope? A servo with a double drum is enough. A drum wraps the rope and the second drum on, so you can open your door and pull. As a rope I use 0.5 mm rope from a radio.

 

I need about 2" of movement from a max 180 deg rotation of the servo arm.  I'd need quite large drums to give me that sort of circumference, plus a pulley of some sort opposite the door for the returning rope.

 

Using a single drum with a wire rope that was springy enough to wrap, but stiff enough to push would also be an option, but again, difficult to find the correct gauge wire.

 

Using the servo with an extended arm ( the stiff wire) will work (it will, it will, it will) - I just need to build better mechanics.

[Smoking gun]

Hi Stu,

You don't need a complete drum just an arc from the rim, as to closing the door I have seen sliding heavy fire doors which use a weight on a piece of rope to pull the door shut, the channel the door moved along had a slight slope towards the "closed" end. I hope this makes sense.

 

Martin

Edited February 2, 2018 by Smoking gun

[Stubby47]

Thanks Martin, it does make sense.

 

Although in 4mm scale, the friction caused by the door (without the aid of well greased rollers) would make the counter weight quite substantial, and thus more strain on the servo pulling it open.