Frequently Asked Questions – Solar Slide Edition

In this blog post, I hope to address many of the frequently asked questions regarding our pneumatic air powered solar slide mechanism. This post will cover different questions from different angles so if I sent you a link to this page but it doesn’t seem as though it answers your question right away, keep reading. 

Keep an eye out for links in the text which I will link relevant video clips giving more context to what I’m trying to say.

Probably the most frequently asked question is why we chose pneumatic air cylinders over electric linear actuators or a linear rack and pinion gear drive arrangement.

While I don’t think there’s anything explicitly wrong with an electric linear actuator, there were several contributing factors why I chose to go with air. 

  1. We already have three redundant air compressors onboard which are used to pressurize our water system, the three point Flex Mount Bumper system, The inside retractable step and now, of course the solar slides. (not to mention airing up our monster tires)
  2. The ¾ inch air cylinders we used are physically far smaller than any gear train/linear actuator I know of. This was important for our rooftop solar slide mechanism because we wanted to keep it as low profile as possible. The whole solar sliding apparatus is only ¼ inch thicker than the panels themselves, ⅛ of an inch below the lower sliding panel, and ⅛ of an inch between the two sets of panels.
  3. Simplicity, no gears to grease, bind up, limit switches to fail, etc, you just push air in and they move… 
  4. They fail closed, should any parts of my control system fail, wiring to the solenoids gets damaged etc, the panels automatically retract. (Assuming there is air pressure left in the 6 Gal, 200 PSI tank, which is critical for other functions too, thus the compressor redundancy)
  5. You can get a lot more work done through one ⅛” air line then through the comparable volume of electrical wire. Running long lengths of wire of sufficient gauge (10AWG?) to power motors, limit switches, position sensors etc adds to the cost quickly.
  6. Cost! it’s was far more cost-effective to go with air cylinders then any electrical option I could find capable of pushing these panels 24”. 
  7. Ease of override, should anything fail I can just pop off the airline from the push-to-connect fitting and manually push these in or out with one pinky finger, the same could not be said for a failed or jammed up linear actuator or geared mechanism.
  8. Weatherproof, this whole thing is stainless steel, aluminum, and UV stabilized air lines, after 4 years on the road, 100,000 km and four countries, we have had zero issues with breakdowns or other reliability issues.

I am often asked about dirt buildup in the grease in the slides themselves, one would think road grime and dust would build up in the greased rollers of the stainless steel drawer slides, creating an abrasive paste that would wear the slides quickly.  I foresaw this as a possible problem, and used a degreaser and then a steam pressure washer to remove any trace of grease and oil from the slides before assembly. I then applied a dry graphite lubricant, which I assume is mostly gone by now. Without the lubrication, the slides are a little noisier, but the 304 Stainless Steel is very hard and seems to be holding up very well running dry. They’ve literally being extended and retracted thousands of times and on recent inspections, they look as good as the day I put them in. 

Another criticism is that I used common kitchen drawer slides, and these are not up to the task and will fail very soon. I would agree with this if it were true. I sourced industrial-grade Stainless Steel drawer slides rated at 100 lb each, these are commonly used in heavy truck service bodies, exposed to outdoor elements, and hundreds of pounds of tools on each shelf. I feel these are more than adequate to hold up a seven-pound solar panel, and I would argue that time agrees with me. 

Below is a list of all the components I used to assemble this solar slide mechanism, Including links to the vendors I purchased them from.

Air Mufflers to help slow down the air cylinders

100lb Rated, 304 Stainless Steel Drawer Slides

Cushioned Round Body Air Cylinder, Double Acting

NITRA solenoid valve, 5-port (4-way), 2-position AVS-5111-24D

12 Volt Coils to replace the 24 Volt coils that come on the above valves

The framework is simply 3” web, 3/16 wall “L” Channel Aluminum Extrusion, I sourced from a local aluminum supply shop.

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