Pier designs/plan/measurements.

[opticalpath]

About that central mounting screw ....

 

The EQ8 bears a remarkably close resemblance to the Gemini G42+ mount I have .... a virtual clone I would say, at least as far as the mechanics look. The G42+ has a lookalike massive tripod-pier with the same odd bevel gear arrangement to turn the central locking screw via a hand-wheel at the side (Gemini call it 'Q-lok'.)  It's actually quite convenient for using the mount on the tripod-pier, but not so helpful an arrangement for mounting on a permanent pier plate as you are screwing from below into the base of the mount.

 

For pier mounting, if you don't fancy the 'central-screw-from-below' arrangement, you could do what I did with my Gemini: fit a sleeve in the central threaded hole in the mount base to provide a smooth bore, then pass a high tensile bolt with washer through the hole from above.  This screws into a threaded hole in the pier top plate, so that it (as well as the two side lock-down bolts) are being screwed into the pier plate from above, without any need for access to the underside of the pier plate. Choose the type of bolt that is not threaded its full length so the unthreaded shoulder section can rotate smoothly in the sleeved hole.

 

As I mentioned earlier regarding levelling .... I screwed three coin-sized delrin disks on to my top plate, 120 degrees apart,  to act as defined load-bearing studs for the mount base to sit on. Before attaching the mount, I put a spirit level across each pair of studs to see how far off horizontal the platform was, then shimmed under the disks as necessary until the tops of the delrin studs were level before positioning and screwing down the mount.  I have not moved it since.

 

Adrian

[Leo.A]

Pardon my ignorance but I'm confused as to why the German equatorial mounts don't need to be levelled?

Wouldn't this throw the tracking out somewhat with my EQ5 Synscan system were I not to level the mount?

I have some 152mmNB pipe I've just picked up and am currently designing my own pier. I have looked at so many designs online and thought the extra plate to level the head created a weak spot and considered using shim washers at the base for absolute level. Should I decide to go the top plate, I have some 3/4 stainless bolts which will be the attachment medium for strength. I've seen many done with 8 and 10mm bolts and they appear to let the overall (overkill) strength of the rest of the pier design down considerably.

I am a welder (among other qualifications) and will be doing the welding myself and am confident of affixing the upright square to the base. I am however somewhat confused with what many specify as minimum requirements for pipe wall thickness and base plate thickness. Steel plate isn't cheap in my region with cutting costs added and I've decided to go with 16mm base and head plates. I first considered 19mm base plate but found cutting charges for 3 plates was going to triple the cost of supply ($50 steel and higher charges for cutting). I have a friend whose an engineer and he's going to get the plate cheaper for me as long as I do the final grinding of the edges. Were he not so busy I'd have him do my mount head too, which is to be machined out of some 125mm aluminium billet and attached with 6-8 bolts (design not finalised).

My largest two scopes are my 8" GSO (Bintel branded) reflector weighing in at around 10KG and a 152mm (1200mm focal I think) Skywatcher refractor I recently acquired. I haven't weighed the SW yet and, they will both take turns on my EQ5 Synscan mount head.

My biggest problem will be specifications for the concrete base. I'm working on an idea of around 900mm deep and 350mm square to accept the 300mm (12") square base plate. This will be affixed with 16mm high tensile threaded rod set around 600mm depth in a welded configuration so it can't pull out of the concrete.

I believe this to maybe be overkill for my scopes but it may as well be strong. I don't know what the land lord is going to say (rented premises)..

[K3ny0n]

Got my pier welded together last night apart from the base plate which is still getting finished. I had a pipe flange welded to the top of the pipe, then I had the top (adapter) part bolted to the flange leaving a 16mm gap between both top parts allowing me to get acess to the nut which holds the mount while also keeping the gap down to a minimun. I used bigger nuts than the bolts and a few penny washers to pack out the middle space between both top plates. The top "adapter" is machined to fit perfectly with the already drilled holes on the flange and is made out of a really thick slice of tufnol, which I am hoping will do the job. If not on to plan B.

Hopfully I can get some pictures uploaded tomorrow.

Rob.

[DrRobin]

Hi Leo,

I am not sure there is any real need to level a GEM, due to the polar alignment. The only thing that is really important is that the RA axis points towards the NCP (or SCP in your case).

If you are not level in the North/South direction this will be corrected for with the ALT adjustment (polar alignment) and if you are out East/West then this will be corrected for with the AZ adjustment. Once the RA axis is pointing towards the pole then any AZ/ALT adjustment is finished.

Having the mount level doesn't even help with polar alignment since you have adjustment of two axis at 90 degrees to each other, it doesn't matter that when you adjust one the mount moves in the horizontal or vertical plane.

So why do all of the manufacturers put a spirit or bubble level on the mount? I suspect the reason has more to do with loading and centre of gravity. The mount designer will have designed the mount to be exactly horizontal and the quoted loads will assume that the load is straight down through the base. If the centre of gravity is offset far enough you might see flex in the bearings/base fixings. I doubt a few degrees out will make any difference at all.

Now a Alt/AZ has to be very level to work correctly, so may be the manufacturers just carry over the same recommendations about levelling to be consistent?

Robin

[IanL]

I bought the EQ6 Extension tube (http://www.firstlightoptics.com/skywatcher-mounts/skywatcher-eq6-extension-tube.html) as the basis for the adaptor my yet to be built pier.  My brother is production manager at a large steel fabrication facility.  I can get on with some basic CAD done should be able to get him to knock up something for me.  Considerations which may help others:

- You definitely do not need to level the pier head to get polar alignment.  As others have said it is perfectly feasible to polar align a non-level mount using the alt and az adjusters.  Being level is likely to make it easier since the alt and az motions are then independent, and also if you are relying on a software/handset process via the polarscope you need to have a good starting point for the reticule, which usually needs the mount to be level to work.  Using software and a camera that shows you where to point the centre of the FOV to correct would work though.

- My plan for the adaptor (nicked from someone else on here I think, can't find the thread) is to drill three holes through the black anodised base plate of the extension tube (the image in the link above shows the extension upside down!)  This can be put back in the the extension tube with the locating hub pointing inwards or I could drill a big hole in the top plate of the pier for it).  Studs could be welded to the top of the plate to match the three new holes and the black base plate bolted on top.  Then the white tube is fixed to it using the three hex head bolts around the edge.  It is a bit tight to fit the holes and the nuts inside the tube but from my drawings and measurements it looks doable.

- The final bit is the white top plate of the extension.  This replicates the top of the tripod, so you just screw the az adjustment pillar in to one of the two holes, bolt the mount head to the plate using the supplied hand bolt (like a very short version of the central tripod bolt on the NEQ6) and then you drop the white plate in to the top of the extension tube and fix it with the other three hex head bolts.

- The neat bit (which may help some others) is that you don't need access to the main bolt to do az adjustments.  There is a supplied needle thrust bearing and a pair of washers (similar to this http://www.sourcingmap.com/15mm-28mm-4mm-needle-roller-bearing-thrust-ball-bearing-axk1528-p-372414.html?currency=GBP&utm_source=google&utm_medium=froogle&utm_campaign=ukfroogle&gclid=CKfi_pTVm7oCFTHLtAodky4AuA but check the measurements as the linked one is just for illustration).  This goes between the underside of the top plate and the handle on the main bolt.  You can tighten the head on to the plate fully it is very stable, but the bearing allows you to make az adjustments without access to the underside of the pier adaptor.

- Clearly you have to tighten both az adjusters once aligned to avoid any slippage thereafter, but it seems to work better than the standard tripod method where you have to slacken the main bolt to make az adjustments and then hope you don't get any unwanted rotation when you re tighten the main bolt at the end of the process.

My main thoughts are now about designing the pier.  Whilst my bro can make tubes up to a relatively small diameter, I don't think they would be big enough for a decent length pier (probably not much more than a drainpipe kind of OD).  So I have two thoughts:

- Have him make a box section instead.  He has a water jet cutter and many years as a fabrication welder under his belt so that would be doable.  Question is for a (say) 1.2 metre pier what size box, what thickness walls and would there be any point in making strengthening braces?  I know a circular pipe would be less prone to vibration but this would be ok do you think?

- Make smaller OD four pipes and arrange them in a square to make a multi leg pier.  Not so sure about that idea, probably no less welding or materials involved, might not be as stable (though I have seen some adjustable piers with 4 x square section aluminium struts arranged like this), probably makes laying out the top plate rather more complex and critical.

The whole thing would be fixed to a concrete base using stud or maybe bolts set in resin depending on how I go about it.  Thoughts?

[DrRobin]

Hi,

It all sounds well thought out, especially the ability to adjust the mount for polar alignment without having to slacken and re-tighten the centre bolt.

Just one thought, if it is a permanent set up you might want to consider a concrete pier?  Just find a tube the right length and diameter, mount it over a base and mix and pour concrete, it will be a lot more stable than a steel pier.  I made one from a stainless steel pedal bin, see this thread....

http://stargazerslounge.com/topic/196833-an-imaging-obs-in-northumberland/#entry2072269

But if it is not a permanent mount then a steel pier in the way to go.

Robin

[opticalpath]

I can recommend having a look at Dennis Persyk's paper on pier design that answers some of your questions:
http://www.cloudynights.com/item.php?item_id=1275

A few considerations:

1. Tubular piers get their rigidity from their diameter, much more than from their wall thickness (see the table in the above referenced paper). So bigger diameter thin wall is better than smaller diameter thick wall.

2. The anchorage of a steel pier to a concrete pad can be the weakest point of the pier for flexure: over-engineer here - use a large diameter thick bottom plate and strengthening webs where the bottom plate is welded to the tube.

I agree with Robin about a cast concrete pier if you don't mind it being non-removable. I made my reinforced concrete pier square using plywood shuttering above ground, sitting above a 3 foot cube hole below ground.
The concrete was done in one pour, so the whole thing is one solid mass right into the ground with no join, rebar going right through the pier and into the underground block. It's incredibly rigid. BTW, if you go that route, I was advised that my rebar should not come any closer than 2" from the surface of the concrete to avoid possible corrosion ... and that includes cutting the rebar short of the bottom of the underground block.

Here's what mine looked like during the build .... not as smart as Robin's, but does the job  
http://universalconstant.com/pier.jpg

Adrian

[ollypenrice]

Pardon my ignorance but I'm confused as to why the German equatorial mounts don't need to be levelled?

Wouldn't this throw the tracking out somewhat with my EQ5 Synscan system were I not to level the mount?

Think of it this way; you have a perfectly polar aligned German Equatorial Mount held in place by an invisible magic shaft running through the polarscope/Polar axis. The magic shaft holds the mount in perfect alignment and there is no pier or tripod. Now you can rotate the whole mount around the magic shaft but wherever you rotate it the polar alignment will always be perfect. And then you can tilt the altitude adjustment wherever you like, set it to any latitude you like, because it isn't doing anything. 

The universe is not the slightest bit interested in where your pier or tripod are pointing. It cares only about where your mount's polar axis is pointing.

Being something like level makes drift aligning easier because there is less interaction between Alt and Az adjustments but it is absolutely not necessary to be level to be polar aligned. Compromising strength in exchange for horizontality is not something I'd be inclined to do.

Olly

[Demonperformer]

Gina

I have a couple of questions about your design for a pier plate [post #15].

I have been  thinking about how I could adapt it for my situation. A permanent setup/obsy is not an option for me. But I may be able to produce a permanent pillar, but would not be able to leave the mount attached, as the threat of theft would be too great. This would, however, probably reduce the hassle of aligning the mount quite a lot, compared to using the tripod.

My primary consideration would be what is the length of the central bolt that you use? For a removable mount, it seems that there are two conflicting requirements: It needs to be long enough to firmly lock the mount in position, but if it is too long it will increase the gap between the upper and lower plates (to give enough room to fully disengage the bolt to remove the mount) which will reduce stability.

There is a red piece through which the bolt passes in your cross-section. Presumably this is another thin plate of some sort?  Probably threaded to stop the bolt falling out if you need to remove the mount?

The other thing I am wondering about at this stage, is there doesn't appear to be a bar against which the AZ bolts move when polar aligning in your design?  So just wondering how your alignment is accomplished without it? Or am I missing something?

Thanks for your help.

[Gina]

Gina

I have a couple of questions about your design for a pier plate [post #15].

I have been  thinking about how I could adapt it for my situation. A permanent setup/obsy is not an option for me. But I may be able to produce a permanent pillar, but would not be able to leave the mount attached, as the threat of theft would be too great. This would, however, probably reduce the hassle of aligning the mount quite a lot, compared to using the tripod.

My primary consideration would be what is the length of the central bolt that you use? For a removable mount, it seems that there are two conflicting requirements: It needs to be long enough to firmly lock the mount in position, but if it is too long it will increase the gap between the upper and lower plates (to give enough room to fully disengage the bolt to remove the mount) which will reduce stability.

There is a red piece through which the bolt passes in your cross-section. Presumably this is another thin plate of some sort?  Probably threaded to stop the bolt falling out if you need to remove the mount?

The other thing I am wondering about at this stage, is there doesn't appear to be a bar against which the AZ bolts move when polar aligning in your design?  So just wondering how your alignment is accomplished without it? Or am I missing something?

Thanks for your help.

Not quite sure of the length of the cantral bolt but I think it was 20mm.

The red thing is a large (penny) washer.  Not threaded - bolt and washers just drop down.  To adjust azimuth PA I just slacken the bolt a little then tighten it up afterwards and check PA again.  To take the mount right off I undo the 4 16mm bolts that connect the two plates and lift off the mount complete with top plate.  Doing it this way means the gap between the pier plate can be kept to a minimum and also if I can leave the plate attached, the PA azimuth will not be far off when reassembled.

For the AZ alignment post I used the post from the NEQ6 tripod - it was left off the diagram for clarity.

HTH

[laser_jock99]

I see the problem with not having the threaded rises, you can not tighten the mount to the top plate. Would a hole which would be drilled in to the side of the pipe to gain acess to the underneath of the mount be okay? Or would it create more problems along the way?

This way it will do away with the two plates I would of been using and have a more rigid pier with just one top plate welded on to the pier tube.

Rob.

You can drill a hole into your steel tube to attach the EQ6 nut- no wobbly 'leveling' bolts required!

My EQ6 is fitted to this turned puck. It's easier for me to adjust azimuth by rotating the puck in the tube.

[Demonperformer]

Thank you, Gina, for the clarification.  Keeping the mount on the top plate (and therefore reasonably aligned) certainly makes sense.

Thinking about this further, I am wondering if I can get rid of the bottom plate altogether (which would presumably increase stability).  Because the pier is not restricted by the size of an obsy around it, I could make it the same size as the plate (250mm). Then I think I could set it up so the threaded rods coming out of the pier would be positioned where your M16 bolts linking the two plates are in your diagram.

I could then have a nut on each threaded rod at an appropriate height above the top of the pillar to allow access to the central bolt.  Once I had these nuts in the right place to produce a level plate (I realise that isn’t necessary, but if it was as close to level as possible then it would minimise ALT adjustments if I then used the tripod, or built a second pier in the back garden) then I could use some sort of adhesive to lock the nuts in that position (thus preventing the local kids from “hopping over the fence” to fiddle with them).

And if I do go down this route, I wonder if three rods would be better than four on the basis that it is easier to get something level on three points (all of which will always be in contact with the surface) rather than four (which can easily produce “wobble” if all four are not perfectly aligned with each other)?  On the opposing side, this would make the forces acting on each rod 33% higher.   The heaviest scope I would be using is the OTA from my 8SE (with focal reducer, camera, filter wheel and OAG).  Not sure if/how much using 3 rods rather than 4 would compromise the stability of the setup?  Or am I seriously overthinking this?

I have been reading up a bit on bolt sizes and have found that M12 bolts come in different pitch sizes; standard and fine.  My guess is that the central bolt is “standard”?

Thanks

[Gina]

Thank you, Gina, for the clarification.  Keeping the mount on the top plate (and therefore reasonably aligned) certainly makes sense.

Thinking about this further, I am wondering if I can get rid of the bottom plate altogether (which would presumably increase stability).  Because the pier is not restricted by the size of an obsy around it, I could make it the same size as the plate (250mm). Then I think I could set it up so the threaded rods coming out of the pier would be positioned where your M16 bolts linking the two plates are in your diagram.

I could then have a nut on each threaded rod at an appropriate height above the top of the pillar to allow access to the central bolt.  Once I had these nuts in the right place to produce a level plate (I realise that isn’t necessary, but if it was as close to level as possible then it would minimise ALT adjustments if I then used the tripod, or built a second pier in the back garden) then I could use some sort of adhesive to lock the nuts in that position (thus preventing the local kids from “hopping over the fence” to fiddle with them).

And if I do go down this route, I wonder if three rods would be better than four on the basis that it is easier to get something level on three points (all of which will always be in contact with the surface) rather than four (which can easily produce “wobble” if all four are not perfectly aligned with each other)?  On the opposing side, this would make the forces acting on each rod 33% higher.   The heaviest scope I would be using is the OTA from my 8SE (with focal reducer, camera, filter wheel and OAG).  Not sure if/how much using 3 rods rather than 4 would compromise the stability of the setup?  Or am I seriously overthinking this?

I have been reading up a bit on bolt sizes and have found that M12 bolts come in different pitch sizes; standard and fine.  My guess is that the central bolt is “standard”?

Thanks

A larger diameter pier with the threaded rods further out would be a big improvement IMO and if I were doing it again I would do that.  Clearly the more rods the stronger and more rigid it would be.  I didn't have any problem with tightening the 4 nuts the same but I agree that a mismatch could lead to stresses in the plate and possible bending.  I think 3 threaded rods spaced further apart with one plate would certainly be better than my 4 on a mere 5" pitch circle.  That was a mistake on my part but I was limited by what I could find at the time to provide a containing mold for the concrete.  There were no 250 or 300mm SS air ducting pipes aroung then unfortunately.  I don't think over-engineering the pier is a bad idea as you might go for a bigger mount and multi-scope arrangement as I am now contemplating.  I'm glad I made mine good and strong

So... If I were doing this again I would use 3 x 16mm threaded rods (galvanised or SS) either bent at the bottom or with nuts locked together on about a 220mm pitch circle with 250mm diameter pier and 250mm x 10mm steel disc.  I would have the threaded rods coming further out than my present build to allow access to the central bolt.  Now that would be really strong and rigid - and well future proofed

Yes, the central bolt is standard M12.

[DrRobin]

Hi DemonP,

I went for 6 M8 SS rods and a 300mm pier plate for my concrete pier. Levelling 6 is easy, just have nuts under and over and level it on three, then run the others up and tighten. I used a stainless pedal bin for the former, it was the right diameter and for me exactly the right height.

Toolstation provided the M8 rods and I bought the aluminium top plate from Aalco via eBay. You can see the design here http://stargazerslounge.com/topic/196833-an-imaging-obs-in-northumberland/#entry2072269

Threads are measured in the diameter, M8, M12 etc and also in the thread pitch. Standard pitch for metric is 1mm, but when you get over a certain size they are also available in 1.5mm. You can measure the thread pitch by using a ruler, just count the number of threads in 10mm and if it is 10 it is 1mm and if it is 7 then it is 1.5mm.

You might also find some imperial sizes, the nominal diameter is the same, the pitch is measured/quoted in Threads Per Inch (TPI). Imperial sizes come in several different sizes/combinations and even different thread pitch angles and the ones you might see on a mount are UNC, UNF, BSW, BSF. To tell the difference you really need a micrometer/vernier, a set of thread pitch gauges, thread tables and a bit of patience.

To lock your pier in place use Loctite or put a second nut on top and tighten against the first.

Robin

[Sp@ce_d]

I went for the 250mm x 10mm steel plates & 4 x M16 rods solution too & never had a problem. I haven't had to re-tighten or touch PA for the last 18 months. This also gives me the option of lifting or lowering the height of the pier without much fuss too. I sunk plastic pipe into a cubic metre of concrete & rebar. For the central bolt I used one of these.. http://www.mossexpress.co.uk/mss/mss-pc.nsf/WebEngine?OpenAgent&cmd=query&itemdirect=y&itemdirectwildcard=y&search=493955

[opticalpath]

For my old LX200 mount, I wanted a single, but adjustable, top plate to mount the wedge on and I borrowed an idea from here:

http://www.pierplates.com/

Using a thick top plate, you can counterbore the holes to allow thin 'half nuts' on top to sit fully within the counterbores leaving a smooth top surface but still allowing a small amount of adjustment for levelling. (The tops of the rods may need a little trimming once you establish the level.

This design allows the 'legs' to be very short - just enough for the underside nuts and washers and a little extra for levelling adjustment. I used only three SS threaded rods but went big and chose M20. The bottom ends of the three rods were tied together with a triangle of three 6mm thick steel straps drilled and slipped over each pair of rods to form a triangular cage. Screwed down tight with spacers and more SS nuts, this held the rods at the correct spacing and acts as a very solid anchor in the concrete.

Adrian

Adrian

[Demonperformer]

Thanks for the replies.  Things are becoming a little clearer to me.

@ Sp@ce_d: I did give some thought to a bolt like that.  It would be a case of balancing ease of use (no spanner required) with the increased distance between the pillar and the mount (to get my hand in to turn it) and the reduced stability this would produce.  As the plate can be left attached to the mount (thus minimising the need for AZ alignment), I am coming down in favour of keeping the plate distance as small as possible and sticking with a 'normal' bolt.

Leg number: Maybe it is just my unreasoned bias, but I am definitely in favour of a multiple of three.  Six is a possibility, but my reasoning against this would be (a) smaller gaps between the legs would reduce the ease of getting at the central bolt when I do need to adjust AZ, and ( the total area through which the force is transmitted into the pillar is still twice as much if I use 3x16mm bolts compared to 6x8mm bolts.  I also suspect that three 16s would be cheaper than six 8s.

However, three legs does not really fit well with a square aluminium plate.  I am thinking that this plate only needs to be big enough to take the entire 'footprint' of the mount, ie about 14cm diameter.  So, a 15cm diameter disc would fit the bill.  This would give a rim around the edge of the plate of about 5cm, which would be enough for the holes for the pillar rods.

Are there any views on the use of wing-nuts for the upper nuts on these pillar rods?  My thinking is that, if I have the lower bolts fixed solidly in positions that enable the plate to sit level on them, then there is no great need for the upper nuts to be any more than 'finger tight' to keep the plate in position.  And they would certainly make attaching the mount and removing it at the end of the night a lot easier (particularly on those cold winter mornings after a night out with cold fingers and thick gloves!).

Once I have finalised all the details, I am going to need to get this made up by a local metal fabrication firm (I have no means of doing the job myself and would probably make a pig's ear of it anyway!).  Don't know if it would be cheaper to source the materials online and provide them, or just get whoever to source and manufacture all in one.  Yellow pages reveals one 'metal fabrication' company about 1/2 mile from me, so that would be really convenient.  Might take a walk over there and have a word - if the rain ever stops!

EDIT: Apologies for the inappropriate emoticon.  I can find no way of getting the system to accept the next in the 'listing' sequence (a), ...

[SnakeyJ]

 I also suspect that three 16s would be cheaper than six 8s.

Not so sure that the shops will support this theory - I just spent £ 20 on stainless bolts, nuts and washers for my pier - the M12 bolts were quite a lot more expensive than the M10 equivalents.

Rather against the good advice in this thread, my 4 x M12s leveled very easily and are rock solid.

[Gina]

I found the (a)... sequence suffered from this too hence using numbers.

I like the "Motel o'Scope" idea in the link above - just what I need for my second imaging position.  I may copy that but it'll need some very secure fastening down in this very exposed location on the side of a hill.

[Demonperformer]

Not so sure that the shops will support this theory - I just spent £ 20 on stainless bolts, nuts and washers for my pier - the M12 bolts were quite a lot more expensive than the M10 equivalents.

Rather against the good advice in this thread, my 4 x M12s leveled very easily and are rock solid.

My apologies.  I spoke without checking my facts.  A quick internet search has turned up prices of £2.10 for 2x2m M8 rod and £4.15 for 1x2m M16 rod.  This makes strength/£ roughly the same.  The nuts are also more expensive.

I think the other two points stand (increased strength and access), and am inclined to say that, for the sake of only a few £, I think I still come down on the side of 3xM16s.

[Gina]

I'm afraid it's no good scrimping and saving a few pounds.  This hobby is very expensive and if you continue you will have to get used to it   It isn't worth trying to save a pound here and there on the pier - make it stronger than you think you'll need and it will stand you in good stead for future upgrades.  Don't say you'll never upgrade - you won't be able to help yourself "once bitten by the bug", beilieve me

[Tinker1947]

Don't forget the delivery cost, my 3 X 1m 16mm studding were cheap enough the postages added £7 to the total..........

[Gina]

I got mine locally from a farm equipment shop.

[K3ny0n]

_{They sell them in a certain orange and white DIY shop if you have one locally.. 8x1000mm from £2.48 up to 12mm which is £3.48.}

_{http://www.diy.com/nav/fix/nails-screws-fixings-hardware/profile-metal-sheets-metal-rods/threaded_rods/FFA-Concept-Zinced-Steel-Threaded-Rod-L-1000mm-x-W-12mm-9283916?skuId=9293616}

_Rob.

[Tinker1947]

_{They sell them in a certain orange and white DIY shop if you have one locally.. 8x1000mm from £2.48 up to 12mm which is £3.48.}

_{http://www.diy.com/nav/fix/nails-screws-fixings-hardware/profile-metal-sheets-metal-rods/threaded_rods/FFA-Concept-Zinced-Steel-Threaded-Rod-L-1000mm-x-W-12mm-9283916?skuId=9293616}

_Rob.

I do believe i have a discount pensioners cards only works on a Wednesday, well 10% is something.....when i checked on-line they only go up to 12mm, i wanted 16mm