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Automating the Bedroom Window

Master Doc.

(Draft in progress; please contribute)

Goal: 

Fully or partially automate the raise/lower of the bedroom read window that's positioned behind the bed. If only partially lowered, consider adding a thicker strip to the top of the window to serve as a sort of railing.

Challenges:

  • Window is approximately 80 kg
  • Window has an arclength (overall length) of 6 meters which potentially leads to large overhang moments
  • Blending 3D contour of Seapod shell with 2D contour of window. 
  • Sealing from the elements and not compromising R value
  • Hiding components allowing access
  • Automating affordably, ideally with off-the-shelf products

image-1614649407583.pngimage-1614649224317.PNG

 

 

Concepts:

Using a linear actuator:

This is an attempt to use a linear actuator (self-contained unit) to solve the problem. While these can be expensive, the tradeoff will potentially be in time spent engineering, proving, and troubleshooting a custom solution. Therefore, this can also be thought of as an "easy-button" to solve the problem, which is not inherently an easy problem.

Considerations:

Drive type:

    • Ball-screws vs. lead screws
      • Ball screws  ~90% efficient - > can backdrive
      • lead screws ~ 40% efficient - > usually can't backdrive do to inefficiencies
      • Ball screws are more precise and expensive
      • lead screws sometimes use a plastic carriage rather than a steel
    • Belt drive seems more oriented towards horizontal applications, whereas ours is vertical
    • Ball screw is most likely the most appropriate for our application

Lubrication:

    • Screw drives and linear bearings usually require periodic lubrication
    • Lubricate using grease rather than oil for vertical applications
    • Some ball screws will advertise that they are maintenance and lubrication free (internally lubricated)
      • These products have a finite lifespan. Once the internal lubrication runs out, the product may fail.
      • Depending on our intended # of cycles and lifetime, such a product may still be appropriate.
    • Some lead screws advertise lubrication free
      • plastic on metal
      • Likely not suitable for our heavy-lift application

Linear guides:

    • will help align the window pane and resist the overhanging moment loads (which are really heavy)
    • therefore, these must be robust due to the high pitch and yaw moments (392 Nm)
    • For instance, a counterweight or screw-drive system on its own would be unable to counterbalance these moments, so we need robust guide rails to do so.

Travel life:

    • Travel life seems to be an important factor:
    • Assumptions for travel life. Raised/lowered once per day, everyday for 100 years
    • 605 mm of travel (1300 mm per open/close)
    • 48 KM traveled in 100 years worst case - on the very low side for these sorts of applications

Electronic Brake:

    • Some systems allow electronic emergency brakes. These are electric open (24 V) - spring close
    • In other words, these are energized during actuation of the window, and normally stay closed
    • This can alleviate the need for a counterweight and/or other safety systems

Linear actuator and motor calculations:

https://docs.google.com/spreadsheets/d/17lEcmTDpThAO0ecSoPah9yGxuAAONtuhxkV19Jpn0XI/edit?usp=sharing

Selecting a linear actuator:

https://www.lintechmotion.com/products2.cfm?ModelNo=170&t=Group6image-1614475500082.png

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Selecting a motor and gearbox (see calculation page):

https://www.google.com/url?q=https://www.newark.com/nanotec/db59s0124035-a/bldc-motor-24v-3500-rpm-84w/dp/72Y1902&sa=D&source=editors&ust=1614478056906000&usg=AFQjCNEciozIo5CgJMnyyZRRSR6iWWqr5g

 


image-1614476178574.pnghttps://www.amazon.com/Gyheung-Extruder-Stepper-Planetary-Gearbox/dp/B08LH19VBG/ref=sr_1_6?dchild=1&keywords=gearbox+5%3A1&qid=1614476207&s=hi&sr=1-6image-1614476233323.png

 

image-1614647836792.pngimage-1614647868184.PNG

 

image-1614648478335.png

Costing (TENTATIVE - big ticket items only - hold off ordering anything):

 

 

Component Make Model Price Qty Ext. Price
Linear actuator Lintech Motion 1741224 $3,319 2 $6,638
24 V Motor Newark DB59S0124035-A $108.52 2 $217
Gearbox Gyheung B08LH19VBG $50 2 $100
           
      Approx. Total System Cost   $7-$8k

 

Other notable systems:

https://www.igus.com/info/page-19897

image-1614652287913.png

      • Could offer interesting options for counterweighting
      • This model is unable to resist heavy loads (plastic on aluminum)
      • Still unsure if a toothed belt drive is appropriate for vertical applications

https://www.youtube.com/watch?v=lQWBI0gnhpI

On another note, I noticed the mechanics that control the slide-out function of an RV slide-out. Its a combination of linear guides, pulleys, cables, motor, chain-drive, and mechanical advantage, albeit in a 'horizontal application' . These mechanics are cheaply available online, and may serve some purpose to us on this window or another.

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