Best size for Pier platform to suit a Losmandy G11

Visionoz (Bill) · #1 31-01-2011, 02:03 PM

Hi All

Would like some advice from the gurus here (who've been there & done that...) to see what is the appropriate size for a pier platform - the one that the EQ mount sits on

I'm going for a fully adjustable platform so it means that I will have four threaded posts and nuts to support the platform and it being the first pier I'm building I'm unsure what diameter I should make this platform - perhaps even a square one?

The mount is a Losmandy G11 - I've made a fitting which is a 6" ID pipe about 85mm high (perhaps should be higher?) which will have the usual 120deg slots to allow the base of the G11 mount to lock into and this ring is welded to the top of the platform centrally

I'm concerned about the clearance of the CW bar which can be affected by the height of the "ring" fitting as well as the diameter of the platform

Hope that I can get some information which will be greatly appreciated - before doing the deed!

TIA
Cheers
Bill

JohnG (John) · #2 01-02-2011, 10:13 AM

Hi Bill

Not sure if this is what you mean but I used an 8" square piece of plate steel, 1/2" thick. I drilled a 1/2" hole in the centre and welded a 1/2" bolt facing up to mount a Losmandy MA. Around the outside edge of the plate I drilled 4 x 7/16 holes to carry the levelling rods, I placed a nut and flat washer underneath and placed a flatwasher, spring washer and nut on top. This gave me plenty of adjustment.

Photo below shows the final setup, 230mm dia thick walled PVC sewer pipe filled with cement and the threaded levelling rods inside, the adjusting plate fitted with the Losmandy MA and the 12" Losmandy extension on top of that, the G-11 is mounted and there is plenty of clearance.

Hope that helps a little.

Cheers

Visionoz (Bill) · #3 02-02-2011, 01:11 AM

Thanks John for the reply - yes that plate (I used the term platform) - what size should it be? - based on what I described preceding post would I have issues with the clearance/space for the CW bar to swing freely all round? I have seen some previous efforts (I searched old posts) and did discover that I am doing what others before had done but because there were no dimensions listed I thought that I'd better ask first rather than be sorry!!

You have mounted atop the plate a Losmandy MA plus a 12" extension which I am not doing - and indeed with your method I can see from the picture that there's no impediment to freedom of swing/movement etc for the CW bar to clear its surrounds - wished I'd known before - I've already got the pier made so I just need to ensure that the plate/platform and mount will have the necessary clearance; in other words if I do rotate the mount in both RA & DEC all around I should not have the loaded CW bar plus weights foul up on the edge of the plate

BTW what is the height of the MA? 100mm maybe or 300mm? I plan to use either a 12" square plate or a 10" diameter disk/ring - with hopefully a MA atop centrally located on the plate

Cheers
Bill

Tandum (Robin) · #4 02-02-2011, 01:34 AM

Here's what the top of mine looks like. I believe Astroman built it, but he's metal mad

JohnG (John) · #5 02-02-2011, 09:14 AM

Hi Bill

I used the 8" (200mm) square steel plate as that was what I had lying around, no point in wasting it. I would be inclined to use the 10" round plate to mount the MA. The thing that you have to bear in mind when using a square plate is that you may not be accurately aligned with the pole, with a square plate and just using the MA alone you may find that the Control Box sticks out at an awkward angle if it is not perfectly square with the pole.

I overcame that by mounting the Losmandy 12" extension on top of the MA, They are compatable. I used the MA because it allows you, by loosening the centre bolt, to turn the base to get a better alignment. Once your close, you can tighten the bolt and use the azimuth adjusters on the G-11. The MA is 6" in dia and 4" high and is fitted with the mounting posts for the Gemini Box or the Digital Drive Box.

Cheers

Visionoz (Bill) · #6 03-02-2011, 10:54 AM

Thanks John & Robin

The information has proved invaluable and I'll be able to get something now fabricated - hopeully I can purchase the MA adaptor readily in Oz

Cheers
Bill

JohnG (John) · #7 03-02-2011, 11:17 AM

Hi Bill

You can order direct from Losmandy http://www.losmandy.com/ be aware that Scott is a little slack on his emails but I have never had any problems getting stuff from him.

Cheers

Derek Klepp · #8 03-02-2011, 02:10 PM

While we are on the topic of piers can I ask what size footing (how much concrete) you need for a stable pier base? Soil is clay type 30cm down.
Thanks Derek

Visionoz (Bill) · #9 04-02-2011, 04:01 AM

Quote:

Originally Posted by JohnG

Hi Bill

You can order direct from Losmandy http://www.losmandy.com/ be aware that Scott is a little slack on his emails but I have never had any problems getting stuff from him.

Cheers

Don't know about that John - as far as I am concerned he's slack in everything!

- Ordered the clutch washers about 2 months ago as mine was a bit worn being a used 2yo G11 - you know it had grooves ringed around the middle part - and am still waiting!!

Cheers
Bill

pmrid (Peter) · #10 04-02-2011, 03:50 PM

Quote:

Originally Posted by Derek Klepp

While we are on the topic of piers can I ask what size footing (how much concrete) you need for a stable pier base? Soil is clay type 30cm down.
Thanks Derek

Hi Derek. clay soil is also called 'reactive to highly reactive" because it responds to water by moving. That's why houses built on clay soil often show cracks in the corners of door frames and the like. So you need to aim to get your pier foundations as deep into the soil as you sensibly can - at least the same depth below as you want to have above the concrete. And with concrete, more is better. Don't skimp. From memory, both my piers swallowed up about 15 bags of premix each. I'm also in clay soil.
Peter.

Derek Klepp · #11 04-02-2011, 07:52 PM

Thanks Peter

Tandum (Robin) · #12 06-02-2011, 02:44 AM

Derek, I also have clay under the topsoil. My base is 900 deep by 800 square on top. I simply got sick of digging it and that is where it stopped. I put about 100mm of gravel in the bottom and used about 12 bags of premixed to fill it. You should put some gravel in the bottom if it's clay to give the water some where to go before it goes up and lifts the footing.

It's been in for well over a year and I only just had to level the bolts on the head of the pier this month after building a dome on top of it.