Triax dish arms - weird question on dimensions!

[jallen01]

A few years ago I acquired (can't remember from where, but it could have been my next door neighbour or the local recycling centre!) what turns out to be GT-Sat 80cm dish which looks very like this one (http://www.gt-sat.com/products/satellitensch%C3%BCssel/16), and I'm just getting around to installing it but I want to fit a multi-LNB bracket.

Problem is that the arm is rectangular in cross-section, and the only commercially-available brackets that I can find for arms that shape seem to be for Triax dishes - so could anyone with Triax knowledge tell me the internal & external dimensions of the arms they generally use as maybe one of those would fit the G-Sat dish arm?

Thanks in advance.

[RimaNTSS]

Go to nearest store and buy some cheap galvanized stuff and then construct something like that. Pretty easy :applause-003:
64887

[echelon]

plenty of different lnb racks of varying kinds on a well know a**tion site !!

some fit the rectangular slot where the lnb holder normally goes, with up to 4 lnb holders

some circle the current lnb and lock tight , with one or two extra holders for more lnb,s

some good be bolted onto the arm itself and then adjusted accordingly

some details and pictures in this lnb thread https://www.satpimps.co.uk/showthread.php?60102-Twin-lnb

[jallen01]

Go to nearest store and buy some cheap galvanized stuff and then construct something like that. Pretty easy :applause-003:
64887

Looks interesting! However, where did you get those clamping pieces used around the arm and the LNBs as I have never seen them anywhere?

PS: still interested in any answers to my original question as, if that looks a possible solution as it could also provide the LNB clamps.

[jallen01]

plenty of different lnb racks of varying kinds on a well know a**tion site !!

some fit the rectangular slot where the lnb holder normally goes, with up to 4 lnb holders

some circle the current lnb and lock tight , with one or two extra holders for more lnb,s

some good be bolted onto the arm itself and then adjusted accordingly

some details and pictures in this lnb thread https://www.satpimps.co.uk/showthread.php?60102-Twin-lnb

I've had a very good look at that site and many others, but I could not work out which have the correct dimensions to able to fit the arm on this dish, which is why asked the question.

Also, I'd like to try to fit up to 2x LNBs on either side, and that also limits the possible choices - especially as I would not want to have to buy 2x of "whatever" to get the extra LNB holders.

[echelon]

I've had a very good look at that site and many others, but I could not work out which have the correct dimensions to able to fit the arm on this dish, which is why asked the question.

Also, I'd like to try to fit up to 2x LNBs on either side, and that also limits the possible choices - especially as I would not want to have to buy 2x of "whatever" to get the extra LNB holders.

triax dish lnb socket on the arm itself is

outer is 50mm wide by 20mm height

inner is 46mm by 16mm

[RimaNTSS]

However, where did you get those clamping pieces used around the arm and the LNBs as I have never seen them anywhere? Have you been in the shop where they sell plumbing stuff and different nuts&bolts? It is LEGO for *****s.

[jallen01]

triax dish lnb socket on the arm itself is

outer is 50mm wide by 20mm height

inner is 46mm by 16mm

Thank you VERY much, and I will check those dimensions against the arm on the GT-Sat dish tomorrow!

[echelon]

this is the one on my 80cm triax dish

https://www.satpimps.co.uk/showthread.php?60102-Twin-lnb&p=420787&viewfull=1#post420787

4 lnb holders, been there a long time

[jallen01]

Have you been in the shop where they sell plumbing stuff and different nuts&bolts? It is LEGO for *****s.

This may be a "national" issue because I am in the UK and I have been into a few of those shops over the years and seen nothing, and nor would I know what to ask for; and most plumbers' merchants only have a small proportion of their stock on display and so asking for the right thing would generally be necessary. The only things I have seen that remotely resemble those clamps are the brackets use to support copper pipe runs, but they have standoffs with flanges that you then use to screw the brackets to the wall (and since most LNBs have 40mm collar dimensions, then probably only those for plastic waste pipes would have the right dimension at the LNB ends).

[TheBadger]

Don't know if these are any good to you
_http://www.jtmplumbing.co.uk/pipe-fittings-c433/rubber-lined-unlined-brackets-c244/jtm-rubber-lined-clamp-m10-m8-pp7502?utm_source=google&utm_medium=***&utm_term=jtm-rubber-lined-steel-pipe-clamp-clips-35mm-1-quot-32-36mm-clips-35-clips-35mm-1-32-36mm-rlc004&utm_campaign=product%2Blisting%2B ads&gclid=CjwKEAiA3Ou1BRDso5XyhduuwFA SJABP3PEDWudp6ViX6GTgVsaHmpiTEnGv kucN5GxblaKv0RT9hRoCfevw_wcB

[Mobley2]

Trying to fit the arm from another dish is not really a practical solution. While you may be able to get the arm to fit at the dish surface
you have absolutely no way ( unless you are acquainted with complex mathematics) of working out the Focal point for the Lnb.
On most arms the bend at the front of the arm would be matched to the angle that the Lnb holder enters the arm tube this,is to achieve maximum gain, fitting a different arm, could
mean that the Lnb focus might be beamed at the top of the dish and consequently the practical gain from the dish could be severely diminished. In order to have maximum gain the focus needs
to be more or less at the centre of the dish. I have some experience of trying this on an 80Cm dish with a Triax multi Lnb holder, but the focus was way off and it was not a success
If you are tempted to try using metal plates and threaded rod with stand off clamps, then I would suggest you do your experiments at ground level, as small adjustments could mean the difference between getting a signal
and nothing. My apologies for such a long winded reply.

regards mobley 2

[jallen01]

Mobley2
I think you slightly misunderstood my question about the arm as I was not intending to change that - but "simply" the LNB holder at the focus point end, and thus needed to know if TRIAX-type parts might fit, and, in turn, that meant knowing the dimensions that Triax normally use..

As for trying things out at ground level - my dishes are or will be all at ground level (actually about 5-6ft above it on poles or mounted on very firm fence posts) so that would be a given anyway
regards

John

[jallen01]

Don't know if these are any good to you

The 42mm version looks as if it might fit the 40mm neck LNBs, and the 22mm version would probably work for the LNBs with smaller necks - so that looks a very good lead (and could well be helpful to others looking for extra LNB holders for their modding projects.

Many thanks for that.

It also got me to thinking back about some rubber-lined P-Clips that I bought for another job last year as some of the sizes could accommodate LNBs as well, and some of those might be useful to or others - see
_http://www.eb*y.co.uk/itm/Rubber-Lined-Hose-P-Clamps-Pipe-Clips-Fastenings-/190886523214?var=&hash=item7220c8785e

[jallen01]

triax dish lnb socket on the arm itself is

outer is 50mm wide by 20mm height

inner is 46mm by 16mm

I've just measured the GT-Sat arm, and the external dimensions are 30mm wide x 15mm high - so it's a lot smaller than that Triax arm. Thus any Triax-type parts to be used would have be designed to fit over the end of a Triax arm, and not inside it - and then they would need quite a bit of shimming to take up the differences in dimensions. Might be worth a shot though if other avenues don't work out.

Anyway, many thanks again for making the measurements.

[echelon]

agreed, I suppose it could be adapted but its a long shot, so I would recommend one of the other lnb racks like the UNIVERSAL metal ones (gilbertini ?) and adapt one of those

or the INVERTO or KONIG ones that clamp onto the existing lnb with one collar and have one or two spare collars that are adjustable along slots in the metal

so it seems that you would need to experiment or build your own rack anyway

at first I did think you were going to change the arm, which gives the problems mobley mentioned earlier, then I realised you wanted to know about the triax arm dimensions of the box section at the lnb end, so as I have a spare arm (in the garage) with a single lnb holder mounted in it I disconnected the lnb holder and then measured the slot and the holder itself, for accuracy

so with some ingenuity I am sure you can manage it, especially with such easy access

another trick I do is wind sticky black tape around the lnb necks themselves if they are too narrow, to enhance the thickness

[Mobley2]

Mobley2
I think you slightly misunderstood my question about the arm as I was not intending to change that - but "simply" the LNB holder at the focus point end, and thus needed to know if TRIAX-type parts might fit, and, in turn, that meant knowing the dimensions that Triax normally use..

As for trying things out at ground level - my dishes are or will be all at ground level (actually about 5-6ft above it on poles or mounted on very firm fence posts) so that would be a given anyway
regards

John

Ahh! understood, I would still advise you to note my comment re the Triax multi bracket, when I bought mine, thinking similar to yourself, that it might fit, I had to mount it over the arm tube, not inside it, because of internal dimensions
however that was not my problem, I found the angle of the Lnb holder to be quite different to the original Lnb holder, and it was pointing much too high, pretty much on the dish rim, and consequently more noise than signal. If you are able to
compare them to check this then maybe it will be a runner, in my case I could not as I bought it online. Good luck in your endeavors

regards mobley2

[jallen01]

Echelon

I've decided to order a couple of these • (http://www.****.co.uk/itm/171780995613?_trksid=p2060353.m14 38.l2649&ssPageName=STRK%3AMEBIDX%3AIT) after finding the image shown here as I could not previously see how to fit them to the existing LNB arm - might need to put some quick/cheap bracing struts to the ends of the brackets like I did many years ago to the Raven Gemini 90 and old NEC 80cm dishes (pics available if anyone is interested!)

Mobley2

I take your point about the LNB holder angle - hopefully the brackets that I bought should put the new LNBs at the same angle as the existing LNB holder on the arm, but I can probably twist them in the vice to change that if I have to.

The main reason I bought some new brackets was to get the LNB holders as cheaply/quickly as possible - but, FWIW, extension brackets can often be fabricated from the perforated strips sold for securing car exhausts and the like (or even a piece of perforated dexion!)

[johnhenry]

I have a 80 cm dish with 3 LNB'S fitted. I set up on 13e as my primary to align the dish, then i fitted my secondaries 19e and Thor 0.8w all connected to 4 to 1 down switch fitted to the frame of my dish. I scanned each satelite on to my receiver first starting in with position 1 Hotbird 13e, position 2 Astra 19e, position 3 Thor 0.8w, As for my Astra 28e i ran this from my sky mini dish (Sky LNB with 4 connections 2 of which went to HD Skybox for Sky+ the third connection on the Sky LNB is a spare) the 4th Sky LNB connection is then connected to the 4 position on the down switch and scanned to position 4 on the receiver. By using the Sky dish for 28e this gives room on the 80cm dish to easily fit the 3 LNB'S for 13e, 19e AND 0.8w. Do hope this all make sense

[echelon]

it makes sense to me and is similar to mine

as for the pic in post #18 , I was looking at similar ones like the INVERTO or KONIG versions, but yes I think you will be fine with them , providing you can fit the centre one around the neck of your existing lnb as well as its current holder too (a long neck lnb would be ideal for that centre one, like the smart shown in the pic)

so for clarity, it clamps around the existing lnb neck , not the dish arm

if you can somehow brace it as well, even better

otherwise its try those UNIVERSAL 4 WAY ones and bolt the rack to the dish arm

[jallen01]

johnhenry

I think you might have posted this in the wrong thread, as I started it in order to find out more about how to fit additional LNBs to an existing dish and what bits I could use - rather than how to then set up the LNBs and receivers to scan the satellites (which is what your post seems to be about).

[jallen01]

so for clarity, it clamps around the existing lnb neck , not the dish arm


Actually, it looks like Imight need to drill a hole (or2?) in the existing LNB holder neck and put a bolt through that (which should not be a problem if done carefully).

[johnhenry]

Another feature about having 3 Lnb's fitted comes when we have a bad winter when snow about (how ever not this winter), one of my Lnbs (19e) froze up and stopped working but thankfully 13e and Thor kept working so I still had satellite programmes to watch. Just two days later 19e came back after snow melted. My bracket is still supporting the same original 3 Lnbs I fitted in 2010.

[echelon]

Actually, it looks like Imight need to drill a hole (or2?) in the existing LNB holder neck and put a bolt through that (which should not be a problem if done carefully).

I definitely would never do that, not at all , if only to stop water ingress

these triple clamps mean one goes AROUND the existing lnb neck, if it has room to fit 2 collars, the original collar and the clamp collar , which is why you need a long neck lnb in the prime position

this is exactly how it was done in the picture that you posted earlier

when it comes try it on a spare lnb and you will understand

see my attached picture, the centre clamp goes around the neck of the existing lnb

[jallen01]

I definitely would never do that, not at all , if only to stop water ingress



I take your point about water ingress in general - which would be easy to stop with a little silicone sealant anyway - , but even it does get into the holder then it's not going to get into the neck of the LNB itself because there would still be no hole in that (If that is what you are concerned about?) but maybe is going to run down the inside of the arm and then out the other end or somewhere else inconsequential!

[echelon]

I think you would damage the lnb, because there must be something inside that neck

plus its irrelevant , because the middle holder clamps around the lnb neck, no drilling required

[echelon]

an alternative is one of these like I used on a zone 2 sly dish many years ago

[jallen01]

I think you would damage the lnb, because there must be something inside that neck

plus its irrelevant , because the middle holder clamps around the lnb neck, no drilling required


Again, I think there is a little bit of a misunderstanding: if you look carefully at the picture (from another forum BTW) that I attached to Post 18, then that is EXACTLY what was done - the bolt in question (the 3rd from the Right) passes through the body of the LNB holder BELOW the actual LNB, and therefore there should be no possibility of damaging the latter (provided that the head of the bolt is not too large and thus pushes hard against the LNB body)

[echelon]

Again, I think there is a little bit of a misunderstanding: if you look carefully at the picture (from another forum BTW) that I attached to Post 18, then that is EXACTLY what was done - the bolt in question (the 3rd from the Right) passes through the body of the LNB holder BELOW the actual LNB, and therefore there should be no possibility of damaging the latter (provided that the head of the bolt is not too large and thus pushes hard against the LNB body)

I think there is a misunderstanding but on your part not mine

that bolt does NOT pass through the lnb in my opinion, its below the lnb and if you look at where the 3 lnb neck holes are you would see that they are in a line above it

that bolt and the 4th from the right as well hold the lnb holder in place which is actually clamped onto the long neck of that lnb as I keep telling you

the 6 bolts fasten the 3 lnb holders to the metal adjustable bracket , no bolts go through that smart lnb , sorry , but they dont , look at the picture I posted in post #25

I have fitted a couple of these myself elsewhere and can assure you that no drilling of the lnb is required

[jallen01]

an alternative is one of these like I used on a zone 2 sly dish many years ago


I looked at that sort of thing as well - but the issue of the dimensions of the arm V the unknown dimensions of the "saddle" at the "front" of the bracket caused me the same problem as the one I started this thread about!

PS: it really would be nice, but far too much to actually expect, if people selling these things gave some dimensional or other info that allow you to clearly understand what something is designed to fit on (even "for TRIAX" etc. would be a help). Some are even worse that that - I saw one advert with a picture of the BOX supposedly containing a holder but no picture at all of the holder itself or details of the design etc., and another with a picture of some sort of bracket/holder inside a sealed plastic bag but again no details of what it actually was! How DO people expect to sell something when they do that?

[echelon]

I know , and I fully agree with you , which is why I am trying to help you seeing as I have bought and used and adapted these parts myself over the years

[jallen01]

I think there is a misunderstanding but on your part not mine

that bolt does NOT pass through the lnb in my opinion, its below the lnb and if you look at where the 3 lnb neck holes are you would see that they are in a line above it

that bolt and the 4th from the right as well hold the lnb holder in place which is actually clamped onto the long neck of that lnb as I keep telling you

the 6 bolts fasten the 3 lnb holders to the metal adjustable bracket , no bolts go through that smart lnb , sorry , but they dont , look at the picture I posted in post #25

I have fitted a couple of these myself elsewhere and can assure you that no drilling of the lnb is required

Actually I think we might be talking at cross-purposes on the issue of the "hole" because, in my case, I would not be using the centre LNB holder on the new bracket to attach it to a "smart LNB" (or any other LNB) already fitted in the existing dish LNB holder because I think the 40mm sections of the necks of most of my existing spare LNBs are not long enough to allow me to attach them to both holders at the same time.

Therefore the " new hole" would be through that existing dish arm LNB holder, and below the LNB fitted in that position - and a longer bolt would obviously be used.

[jallen01]

I know , and I fully agree with you , which is why I am trying to help you seeing as I have bought and used and adapted these parts myself over the years

I know that, and thank you! - but please see Post 32.

[jallen01]

PS: I've "adapted" a few things over the years. Attached image shows how I fitted a standard Sharp Universal to my old (1991-ish) NEC 3000 80cm dish - which was said to be "impossible" to do - and got it spot on the focal point!

Still there about 20yrs later - but I doubt the Sharp LNB still works !

[echelon]

fair enough , but if you read my posts again I did mention that you need a long neck lnb at the main focal point where the existing single lnb holder would be (in other words you may need to buy and fit one there too) and I was giving you the official version of how it all works in practice

the lnb rack you have bought is designed to clamp aroung a long neck lnb and then fit one or two lnb,s in the spare holders, more importantly it allows you to "spin" the whole thing around clockwise or anti-clockwise on the existing long neck lnb until the rack is at the correct axis in relation to the holder, so on a slant is what I am saying

only when its on the correct axis (skewed) , which is not horizontal , will you be able to adjust the other 2 holders to pick up an extra 2 satellites close by

only when you have done the above alignments could you drill the existing lnb holder and fit the bolt , possibly a new bolt as well as those 6 bolts above, possibly replacing one of the middle ones with a longer bolt if it actually manages to line up and allow you to clamp the new rack to the existing lnb holder

but you cannot just drill the hole and bolt it up without getting that skewed plane right , plus you wont be able to adjust it clockwise or anticlockwise to get the axis right either, once its bolted up , unless your new bolt allows for that action too

I have just jury rigged up one of those racks with a new inverto long neck 40mm lnb and added the triax lnb holder as well for you to look at how it works in practice the way its designed to work, with no drilling required and maximum adjustment allowed, you can see the double clamp around the neck quite clearly , plus the outer lnb holders are in alignment with the middle one too in all directions

see the pics below

[jallen01]

Echelon

Many thanks for that, and I certainly did miss the point about the long-necked LNB in your earlier post but, as luck would have it, I do already have one - and it's the twin of the Sharp White Universal shown fitted to the NEC dish, and that one still does work as I checked that over the weekend (it spent the last 20 yrs or so indoors and unused)!

So, maybe I'll use that in the configuration you mentioned and then, when the tilt angle is determined, replace it with one of the short ones - pity that none of the adverts for these give enough info to make all this very important details clear (at all!).

Thanks again!

[echelon]

excellent , that should work and allow you to determine all the correct angles and skews and yaws

once done, its either leave the long neck one in place or bolt the new holder to the existing holder in the manner you describe, providing it doesnt pitch up or down or cause other alignment issues, I think my pictures made it clearer to you and I now see you meant to drill the existing lnb holder and not the actual lnb itself

so cross purposes on both sides but I believe as practical people we got there in the end

let us know how you get on, its very interesting to say the least :)

one other method I thought of was bolting some sort of L bracket to the dish arm underneath and bolting that new rack onto the upright of the L shape in some manner that allows the same issues to be sorted out even if it needed trimming with a hacksaw

[jallen01]

Now here's another weird thing!

I have finally finished all the gardening work for the meantime and can get back to setting up the dishes - when the weather is OK - and that will also involve a replacement of my old NEC steerable dish & mount by another "new old " dish and mount (which will now be a new Diseqc mount).

Here's the "weird" bit - the "new old" dish is white-painted steel, approx. 98cm high and 86cm wide, and has a "very TRIAX" looking folding arm on it with those 50mmx 20mm outer dimensions we talked about earlier - so it looks, armwise, like a TRIAX dish BUT the dish size does not seem to match with any of the current TRIAX sizes and there are absolutely no manufacturer's trademark or other markings on it.

Having done a few web searches I can't find anything to match it, and so does anyone know whether this might be an older TRIAX design or a rough clone thereof, as I want to try to get the dish specs and especially the offset angle

Thanks in advance.

[jallen01]

Update on 8th March post FWIW

It looks like this latest dish IS a TRIAX but possibly an unmarked contract version - but there is an intriguing thing that I found:
- Some retailers DO sell a 98cm TRIAX and show the TRIAX part number as 122901 (in keeping with the rest of the TRIAX TD dishes, the "9" appears to signify a 98cm dish - which "fits" this one)
- OTOH, the actual TRIAX catalogue, and the listings on many major retailers' sites, show part number 122901 to be the TD110 110cm dish, and no 98cm dishes are listed at all!

So it seems that TRIAX appear to have used the 122901 number for two different sized dishes, and the 110cm version is what you will now generally get at about £60-70 retail (unless you look on AM*Z** where you can double that price)!!

Makes the tenner I paid for this one AND a Silent Gold SM 99 mount from the local council waste site quite a bargain, even if it was 10yrs or so ago!:hurray:

[jallen01]

Echelon

I've decided to order a couple of these • (http://www.****.co.uk/itm/171780995613?_trksid=p2060353.m14 38.l2649&ssPageName=STRK%3AMEBIDX%3AIT) after finding the image shown here as I could not previously see how to fit them to the existing LNB arm - might need to put some quick/cheap bracing struts to the ends of the brackets like I did many years ago to the Raven Gemini 90 and old NEC 80cm dishes (pics available if anyone is interested!)

Mobley2

I take your point about the LNB holder angle - hopefully the brackets that I bought should put the new LNBs at the same angle as the existing LNB holder on the arm, but I can probably twist them in the vice to change that if I have to.

The main reason I bought some new brackets was to get the LNB holders as cheaply/quickly as possible - but, FWIW, extension brackets can often be fabricated from the perforated strips sold for securing car exhausts and the like (or even a piece of perforated dexion!)


FWIW reference the 3-way LNB holder shown in Post 18, I've just fitted the two of them to two dishes and found a few problems:
- had to cut off material from the lower edges of the existing LNB holders on both dishes because the large heads of the 2 posidrive bolts which secure the centre LNB to the slotted bar were fouling those existing LNB holders and were both preventing that LNB sitting in the existing holder at the correct angle and also prevented the bar being skewed to allow the LNB at one end to be higher than the one at the other end.
- The new LNB holders are quite fragile near the edge that is secured to the slotted bar - one was already snapped before I fitted it, and another one snapped as I trying (gently!) to open the top to slot in an LNB. "Repaired" those with cable ties around the breakage point - and reinforced another one before I even try to fit an LNB. Just ordered a 3rd LNB holder set to get some spares for the future :-(.
- Had to fit a couple of the LNBs (Comags FWIW) upside down because a lot of the body sticks out at 90deg from the axis of the LNB and is very close to the 40mm diameter part of the body, and thus fouled the nuts on those bloody posidrive bolts! Choose your LNBs carefully if you use these 3-way holders.