To fill or not to fill? The pier that is...

[Bizibilder]

Having just got my nice new pier back from the welders I do have a question for you pier experts out there: Is it worth filling the pier with anything?

I have looked around the net and found sites that range from the "use sand" type to the "the physics of high and low frequency vibration damping in telescope piers" kind!!

I'm confuddled!!

P.S. My pier is 5.5" steel tube 1m long and the whole thing, including the bracing, weighs in at 90lbs. If you want a pic please see my Blog in my signature.

Thanks in advance.

[RobH]

My pier is filled a little more than halfway with a sludgy mix of sand and engine oil. There is absolutely no vibration, ringing, resonance or similar of any sort.

If you do this though, make sure you dry the sand out thoroughly first though, as the oil will displace any water over time (as I found out!)

The reason its not filled the whole way is to keep the centre of gravity low. The oil has the added benefit of stopping any corrosion on the inside of the pier.

Cheers

Rob

[roundycat]

I have an eight inch diameter five foot pier made from steel with an 8mm or so wall thickness. It does ping very slightly if I whack it but I have never seen any kind of vibration in use. It is filled with fresh air. I did contemplate doing what Rob described above but it is already about 200lb in weight and I didn't want to add to that.

Dennis

[Helen]

I put play sand in mine, just to stop the ringing.

Helen

[adamsp123]

I would definately recommend filling it with dampening material - sand or similar material.

[Merlin66]

I like Rob's idea of oil/ sand mix.

[MikeD]

Just dry sand for mine.

Mike.

[Tim]

If you pop to a local builders merchants, or even B&Q, grab a bag of kiln dried sand. making sure there are no rips or tears in the bag. A bag of normal sand can contain a jugful of water.

I havent filled mine as yet, but plan to use at least oil to help fight corrosion, probably in the sand as above.

[NickH]

Same here, plan to fill mine (like Robs idea too)... about half way

We did something similar with speaker stands in work... (holding Genelec 1034's)

[MartinB]

I have an aluminium pier and my guiding is suggesting some rapid vibrations which I can't feel by touching the mount but it's there alright. Doesn't seem to effect the results. I'm going to use a sand and oil mix and see if that puts a stop to it. If you haven't got any evidence of vibration then it would seem sensible not to do anything!

[Bizibilder]

It looks as if sand is a favourite! I must admit I'm not too keen on adding oil, simply on the grounds of mess if I should ever want to move the darn thing!

I reckoned on painting the insides by swilling some diluted hammerite around in it and then draining the excess - that should help the corrosion problem.

Thank you all for the tips - anyone else????? - keep 'em coming!!!!!!

[RobH]

What the oil does is keep the sandy mix in really close contact with the pier at all points.

Sand will work of course but I tend to be 'belt and braces' with this sort of thing, and you'll only really find out if you have any vibration issues after you've invested a lot of time in getting a really good polar alignment and been using the rig for a while, at which point you'll have to then upset everything if you find there's a problem.

If I have to move, a bit more mess while dismantling the observatory won't make much difference

Cheers

Rob

[Tim]

A good layer of grease around the welds especially would do the trick too, but maybe access is tricky?

Due to the way in which hammerite works, I'd be surprised if a diluted solution of it would do very much. Although I have used hammerite for many garden jobs with no problems, the guys I know who are fabricators reckon it to be rubbish and say you might just as well use the normal metal paint from B&Q.

I suppose to ease the (potential future) mess you could fill the bottom and then cap off the sand and oil with an expanding polyurethane foam over a cardboard layer.

[Wobbly Bob]

It looks as if sand is a favourite! I must admit I'm not too keen on adding oil, simply on the grounds of mess if I should ever want to move the darn thing!

Thank you all for the tips - anyone else????? - keep 'em coming!!!!!!

MESS I swabbed the inside of my pier with greese before filling it 2/3rds with brichbats and concrete, now that was messy. No ringing now, solid as a rock. I dare not think about removig the pier as it is set in half a ton of concrete

[roundycat]

TJ mentioned using poly foam. Why have I never heard of that before, it would seem to be the perfect solution.

Dennis

[NickH]

a great thread this...thanks guys!