Lighter, Smaller Pier Proposal

In the PAN008 I loosely describe the new pier that I have built but I wanted to make a dedicated thread for it to see if we want to adopt it as a default.

The biggest issue is that the aluminium extrusions we have listed as the default are a non-standard size, so are typically harder to find and cost a bit more. Additionally, these pieces are heavier, meaning that shipping costs can often be higher.

Similarly, the bottom and top metal plates that we use are designed to be very robust but are also a bit heavier and harder to find. Our default parts list had ebay listings, some of which have since disappeared.

Extrusions

The more standard aluminium extrusions are 40 series, referring to 40mm of at least one of the sides. These are listed as e.g. 4080 for a 40mm x 80mm size. You can see some examples from 8020.net here. In addition to varying sizes there are varying surface configurations: smooth, t-slotted, etc.

The most “standard” of these (as far as I can tell) is the 4040 smooth with t-slots. Of these there are three different types: regular, lite, and ultralite. This refers to how “dense” the extrusion is.

I’m proposing that we use these 4040s as our default for the custom pier.

For PAN008 I ordered the regular version because I was not aware the lighter versions existed (or they just weren’t available in Australia as I didn’t see the option).

My top plate is 120mm x 120mm(~4.7" x 4.7") and the extrusions are placed in the “corners”, as shown here:

The “regular” version can easily hold all the weight that we want to put on it. The “lite” version should be able to as well. The 8020.net website lists the same Yield Strength (241.1 N/ Sq. mm) for each of them, which is more than enough. They are all capable of having M8 taps.

Plates

For the plates, I think the biggest issue would be to reduce the thickness but we can also certainly reduce the size of at least the top plate.

Bottom Plate

My bottom plate is probably too small. I’m fortunate enough to be at a University with a metal shop so I just asked them to use whatever spare parts they had.

Current list: Aluminum 12”x12” x 3/4” (304.8mm x 304.8mm x 19.05mm).
Mine: 9.41" x 9.41" x .47" (239mm x 239mm x 12mm)

(I asked for 240mm it is just cut slightly smaller).

Top Plate

Our current list: Aluminum 6”x6” x 3/4” (152.4mm x 152.4mm x 19.05mm).
Mine: 4.72" x 4.72" x .79" (120mm x 120mm x 20mm).

Mine is probably too thick. As you can see mine is also the absolute minimum length/width you could use with the iEQ30 Pro as the mount is flush against the edges:

Proposal

  • Extrusions: 4040 UltraLite aluminium extrusions.
  • Bottom Plate: reduce the thickness to about 1/2" (12.7mm). Keep the length/width at 12"x12" if possible (based on availability).
  • Top Plate: reduce the thickness to about 3/8" (9.5mm). Keep the length/width at 5"x5" if possible (based on availability).

The changes above can actually have a pretty good cost savings, both in terms of materials as well as shipping costs.

Hi Wilfred,

I was doing some research. I still want to try out the wood, but just in case it doesn’t work, could you please have a look at this and check if it is similar to the one you used?

Please, do let me know. It can take a long time for them to get delivered, but I just want a plan b for units 2 and 3.

Here are more options:

Thank you!

@DrWags yes, those should work with some modification. The center hole is a bit larger so it couldn’t accommodate an M8 bolt, but that could probably be worked around.

This is a good example of why the 4040s might be a better option as they seem to have more availability world-wide. I can see some other sizes on the India Amazon but not the 80160s (or the equivalent imperial measurements) that we use on our current list.

I’ll email you off the forum about your specific order as we were planning on shipping some from the USA and this might be a better option.

I’m also using a smaller extension for the weather station support that sticks out the side of the pier, namely the 25-2514. It will require some adjustments to how the weather station is attached but still has the convenient t-slot so shouldn’t be too difficult. Specifically, you can just order some of the t-nut adaptors for attachment. The extrusion itself can be attached to the pier with the right-angle connectors.

This smaller pier may work. Note its not the axial load that is the issue (i.e. if you squeeze the extrusions along their long length, they will not buckle). Its the lateral stiffness that we are going for (i.e. how much the pier will bend due to wind for example).

The current pier has a metal cross section of 6"x6". Using 4 40x40 mm extrusions reduces the metal cross section to about 3"x3". Putting a gap between the bars increases the baseline and improves stiffness. Conceivably, your pier is probably stiff enough but hard to say until I build it and get a feel for it.

Thinning the top and bottom plates doesn’t really help. Using standard size plates is key to reducing lead time and cost. Whether its 1/2" or 3/4" should result in an incremental difference Id suspect. The top plate holds the 4 (or 2) extrusions together and supports the mount. it doesn’t have to be thick. It just needs to recess the M8 bolts. The bottom plate however, supports the mass of the pier, mount and head unit. It too is supposed to recess the heads of the M8 bolts and should probably be a little thicker to support all that. 1/2" would be the minimum but if 3/4" is available, Id use that to be safe.

In terms of area, for the top plate Id insist on it always being bigger than the cross-section of the base of the mount. Otherwise the mount wont sit on the plate in a stable and reliable fashion.