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Pier for 1100GTO #Guiding

Donald Gaines
 

Hi Len,

That is a very nice pier.  What you say makes a lot of sense.  It looks like the sides were rolled to produce the shape.

Thanks,
Don


On Saturday, March 20, 2021, Len Fulham <lfulham@...> wrote:
Embedded or bolt attached pipe piers are commonly and successfully used, but they have an inherent tendency to resonate vibration. Filling with sand or concrete changes the frequency and maybe amplitude without necessarily improving damping as might be expected.

The best piers have a broad base tapering progressively to the top. This form minimises the tenancy to resonance and is self damping. It is not a good shape for embedding, but works extremely well for bolted applications (eg bolted to a concrete base).

Look at this example:

https://ap-ug.groups.io/g/main/photo/113262/13?p=Created,,,20,2,0,0

The pier has a 600mm square base bolted to a isolated concrete foundation. The pier tapers exponentially to 150mm square at the top. It is made of 6mm thick mild steel. It forms an extremely stable base for the vintage AP 706 mount and 6" AP scope.  It takes more to organise a pier like this but it is appreciated in the long term.

A simpler "tall pyramid" shape (ie tapered flat sides rather than curved & profiled)) would be much better than a pipe, and could more easily be made embeded.

Something to consider,
Regards,

Len.
Len Fulham
 

"It looks like the sides were rolled to produce the shape."

Don, yes/no. I had a boiler-maker make it but there was no roller. A press was used to progressively make small bends to form the shape. I made a cardboard template with bends every 4" for him to work to. I do like the pier that results. On a different scope I replaced a pipe pier (8" dia, 60" long) with a similar tapered pier with great improvement. That one had a 16" base tapering to 6", 60" high but was asymmetric - the Nth  side was flat so the equipment C.O.G. was kept over the pier foot.

Made of steel these piers are quite heavy, but not intended for portability! Could be made of aluminium of course.

As mentioned a straight sided tall pyramid pier would probably be just as stable but has greater bulk higher up where it might affect a long scope.

Len,

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