Another hollow concrete block pier

[iamjulian]

After spending far too long thinking about it, I have sort of decided how to start building my pier. I am a fan of low tech solutions and although I could get permission to sink half a tonne of concrete into the back garden, I don't see the point.

For a good while I planned to copy the excellent brick pier someone posted here (apologies,forget who it was). Then I saw the hollow concrete block pier they have up at Todmorden and knew that was for me.

Picked up a couple of blocks from a farm in deepest Wales and am planning to attach them to a big paving slab. Now my questions for you knowledgeable lot

From what I read, I should just be able to glue block to block and block to paving slab. I also read some of these trade glues can be stronger than the concrete itself. Sound reasonable? Bolting them together was the other option.

Second problem is how to attach the telescope head. The top bit of concrete is 5cm thick so I cannot see an easy way to bolt the head and top bit of tripod (minus legs) with the existing bolt. Although it would save me messing about with pier plates and pucks and all that.

Any ideas or inspiration very welcome!

Thanks

Edited July 3, 2015 by iamjulian

[KyleStoke]

It shouldn't be too hard to drill the block, your original center bolt probably wont be long enough but you can get a longer one from a DIY store. not sure what mount you are using but if it is a Skywatcher its probable an M10 bolt.

What mount are you planning to attach?

[iamjulian]

Sorry yes, HEQ5. The existing bolt is thin at the top, then widens out and is only part threaded, I just assumed a standard bolt would not be suitable. That would simplify the task.

Downside would be that I would have to leave the top part of the tripod in place permanently, else I'd have no set up time saving over the tripod. There is no cover so it would probably rust maybe I will have to have some kind of pier plate.

Edited July 4, 2015 by iamjulian

[iamjulian]

I suppose if I mark its position, maybe glue some metal strips in place then I can just drop it into position each time. Which would probably be just as good or better than loosening the azimuth adjusters each time if I went the pier plate route. Sorry, thinking out loud in case anyone knows better

[Tinker1947]

My choice of glue would be this stuff......

http://stickwithusltd.co.uk/index.php?_a=product&product_id=8

[Peter Drew]

Hurrah! At last someone else giving the hollow concrete "Tod" pier a go, I've been banging on about these for ages on the grounds of their simplicity and cost effectiveness.

I just bolt through using M10 studding, preferably stainless, same for the mount. You can grind one block face against its mating one to get a good flat surface and the final build can be clad for appearance sake.  I now have 5 units on site.  

[keithatrochdale]

Hi glad you popped up to see us at TAC and found a simple and inexpensive solution for your pier.

And covered

Look forward to meeting you next time you visit.

.

[iamjulian]

Thank you, Tinker, looks like the kind of thing. If it is easy to drill I may bolt and glue the two blocks, and just glue the paving slab.

Thanks Keith and Peter. I met Peter at last year's NWAF. I may well ask you further questions about the best way to proceed. They whole thing is really heavy and stable even without anything attached to anything else. I love the simplicity of it.

[iamjulian]

Ground has been broken. The ground here is clay and sinks quite rapidly. I have decided to sight the foundation paving slab on top of an old tree stump. Made more work for myself but the root system should be giving the ground a bit more stability.

Gave the slab a quick test before putting the sharp sand down and wouldn't you know it, it was bob on. Ah well, another 20 minutes playing with sand and I am happy. Though no doubt it will settle wonky, especially once my 5 year old spots it in the morning and starts bouncing up and down on it

Edited July 4, 2015 by iamjulian

[KyleStoke]

Sorry yes, HEQ5. The existing bolt is thin at the top, then widens out and is only part threaded, I just assumed a standard bolt would not be suitable. That would simplify the task.

Downside would be that I would have to leave the top part of the tripod in place permanently, else I'd have no set up time saving over the tripod. There is no cover so it would probably rust maybe I will have to have some kind of pier plate.

You could place an upturned old style black bin over the top of it to protect it from the elements, i left mine out over a year with a motorbike cover wrapped around it, seems to have no ill effects

[iamjulian]

Glue has gone off and it all seems very solid. Bolted together with two m10 bolts with big washers and nylocs. I swapped out the flag stone in the earlier picture with a beefier one. Just took legs off tripod and drop a length of threaded rod through a hole in the top concrete block. A handwheel then locks it in place.

Once I have aligned it properly I shall glue some markers in place, allowing me to just drop the mount on the pier and know it is very close to being aligned. I don't plan on leaving the mount on the pier between sessions.

[richyrich_one]

Hurrah! At last someone else giving the hollow concrete "Tod" pier a go, I've been banging on about these for ages on the grounds of their simplicity and cost effectiveness.

I just bolt through using M10 studding, preferably stainless, same for the mount. You can grind one block face against its mating one to get a good flat surface and the final build can be clad for appearance sake.  I now have 5 units on site.  

Put me down, love the simplicity and low outlay. Bolting mine.

[spaceboy]

This looks a great solution and alternative to breaking your back digging a 3' hole for a drain pipe. Can I ask why these are stuck together with glue as apposed to mortar ??

[richyrich_one]

Can I ask why they are glued at all?

[Zakalwe]

Mortar is a very poor glue, when used in this application. It would fail very easily. A modern adhesive would probably rip the block apart before failing.

You could also use a chemfixer to anchor a bolt into the base and bolt the bottom block down.

[iamjulian]

There isn't enough for the mortar to grip to, plus as Zakalwe says, the type of glue I used should be about as strong as the block itself.

Why bother with glue at all?  The base footprint is about 20cm, the height just under a metre, so it wouldn't fall over easily, but I don't want it moving even a fraction of a mm so leaving it freestanding, heavy though it is, probably isn't the best idea.

[Zakalwe]

Why bother with glue at all?  The base footprint is about 20cm, the height just under a metre, so it wouldn't fall over easily, but I don't want it moving even a fraction of a mm so leaving it freestanding, heavy though it is, probably isn't the best idea.

It'd have to be secured to the ground. I would feel very, very nervous about a mount and OTA sitting on an unsecured pier. It'd be very top-heavy and the consequences of the lot getting knocked over would be horrendous.

[richyrich_one]

My mistake, I thought it was bolted as well.

[Physopto]

You could drill through the base of the blocks into the paving slab and fit resin anchor bolts. Also s/s bolts between the blocks with large washers plus fibre washers to stop any cracking of the surfaces.

What ever you do, do not use hammer action !!!!!!

Derek

[Scorpius]

OK - So I get the fact that a lot of folks are fans of low-tech, low cost solutions. But just how low-tech can you go before the laws of physics take over? There are sound engineering principles behind the idea of a solid foundation (concrete plug) for a telescope pier and I just can’t understand how a couple of cinder blocks glued together that depend solely on a “floating” paver for support could be substantial enough to carry expensive astronomy equipment.

Guess I’m in the minority here but I’d rather over-engineer something than under-engineer it but maybe the conventional wisdom of pier construction is wrong. I will say however, an unsecured paver placed on top of a tree stump (which will eventually rot away) can’t possibly be sturdy enough to limit movement to a fraction of a mm. Then there’s also frost heave – a proven phenomenon - where the earth above the frost line moves up and down. This type of movement in and of itself would seem to prohibit any type of permanent PA in areas which experience prolonged temperatures below freezing.

The whole idea just sounds flimsy to me but apparently many folks have had great success using this method and materials. I’ll just never know from personal experience since I’m gonna bury an 8 inch steel pipe 3 ft. in the ground and surround it with copious amounts of concrete and never have to worry about it again.

Best of luck but I’d at least find a way to tie it to the ground or the whole thing is liable to tip over and damage or destroy your equipment… 

[Zakalwe]

OK - So I get the fact that a lot of folks are fans of low-tech, low cost solutions. But just how low-tech can you go before the laws of physics take over? There are sound engineering principles behind the idea of a solid foundation (concrete plug) for a telescope pier and I just can’t understand how a couple of cinder blocks glued together that depend solely on a “floating” paver for support could be substantial enough to carry expensive astronomy equipment.

Guess I’m in the minority here but I’d rather over-engineer something than under-engineer it but maybe the conventional wisdom of pier construction is wrong. I will say however, an unsecured paver placed on top of a tree stump (which will eventually rot away) can’t possibly be sturdy enough to limit movement to a fraction of a mm. Then there’s also frost heave – a proven phenomenon - where the earth above the frost line moves up and down. This type of movement in and of itself would seem to prohibit any type of permanent PA in areas which experience prolonged temperatures below freezing.

The whole idea just sounds flimsy to me but apparently many folks have had great success using this method and materials. I’ll just never know from personal experience since I’m gonna bury an 8 inch steel pipe 3 ft. in the ground and surround it with copious amounts of concrete and never have to worry about it again.

Best of luck but I’d at least find a way to tie it to the ground or the whole thing is liable to tip over and damage or destroy your equipment… 

There's plenty of imagers that plonk a tripod on grass and get on with making excellent images. Would you say that they are all incorrect?

http://www.iankingimaging.com/show_article.php?id=32

As a "floating" paver? Well, it will move over time and require polar alignment ever now and then. But, unless it blows away in a breeze , it'll be more than substantial to support a mount and an OTA weighing less than 20Kg in total. Personally I think that there's a lot or garbage talked bout piers. Talk of "rat-cages" flexing and bending (ever tried to bend a 16mm studded rod?), huge diameter piers and tonnes of concrete being absolutely necessary is, IMHO, snake-oil. Sure, it won't do any harm to over-engineer, but at the same time, to insist on it isn't right.

[Scorpius]

There's plenty of imagers that plonk a tripod on grass and get on with making excellent images. Would you say that they are all incorrect?

http://www.iankingimaging.com/show_article.php?id=32

As a "floating" paver? Well, it will move over time and require polar alignment ever now and then. But, unless it blows away in a breeze , it'll be more than substantial to support a mount and an OTA weighing less than 20Kg in total. Personally I think that there's a lot or garbage talked bout piers. Talk of "rat-cages" flexing and bending (ever tried to bend a 16mm studded rod?), huge diameter piers and tonnes of concrete being absolutely necessary is, IMHO, snake-oil. Sure, it won't do any harm to over-engineer, but at the same time, to insist on it isn't right.

A tripod works because the legs extend outward thereby distributing the load over a much wider footprint but the whole point of a constructing a pier is to create something far more stable than a tripod, is that not correct? Otherwise, why even have a pier at all and just leave the tripod setup and cover it with something to protect it from the elements.

I don’t believe I insisted that the OP do anything more than he planned so not sure where you came up with that idea?

I’d say if someone wants to build their pier out of popsicle sticks that’s certainly their prerogative but how well it performs in the long term will be governed by the laws of nature (frost heave) and the laws of physics (top-heavy with inadequate foundation).

As I said – best of luck to the OP and sorry for having an opinion different than most. To be honest, I suspect the popularity of this type of design stems more from an aversion to manual labor than anything else but pretty sure that won’t be a popular opinion either. 

[Scorpius]

Greetings All,

After looking back at my previous post, it occurs to me my last comment was inappropriate so my apologies to anyone who may have been offended. For what it’s worth this was not my intent and I do realize what works for some doesn’t necessarily work for all. Since these block piers seem to be so quick and inexpensive to build, I may end up installing one outside my future obsy for visual use.

Hope everyone has a great weekend and best of luck with your future astronomical adventures…

Regards,

Scorpius

[Peter Drew]

Well said Scorpius, no ripples in the "Pond".   

[iamjulian]

Scorpious, thanks,a valued opinion and you may be correct mine is intended to be shortish term and an experiment.

Frost heave shouldn't be a problem as I take the mount off after each session so polar align needs doing each outing (though it is quicker than the tripod). Toppling isn't an issue as the total weight of the pier is about 85kg, it only stands 88cm high, and the bottom paver is about as wide as the structure is high. I am reasonably confident nothing is going to topple over

I chase asteroids so the 60 second sub's I am getting are fine else it's my targets that start to trail, even if the stars do not.

I completely understand why people decide to build it once and forget about it. But so far in my experience, a cheap and less permanent pier can still perform pretty well.