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View Full Version here: : My GMT-128 Tripod Grew Some


Kunama
26-01-2017, 09:39 AM
The GMT-128 tripod by Synta, also known as the EQ6 Tripod, just wasn't up to the task of holding the bulky Takahashi TOA130NFB / AZ-EQ6GT combination still enough for my liking.....

First step was to remove the standard eyepiece tray/spreader which was good at neither job. This meant also getting rid of the very long centre bolt and replacing it with a custom M12 Ring Bolt.

Then came the "Kunama Spreader V1.0" which has helped enormously but the one problem that remained was that the lower leg extension of the tripod needed to be extended for viewing comfort but this induced unacceptable vibrations.

Presenting the "Kunama GMT-128 Version 2.01"
The ultra thin walled (0.85mm) 660mm long standard leg sections have been removed and in their place are 50.8mm x 1.6mm walled 316 grade highly polished (by a 200yr old Master Polisher from Outer Mongolia) legs of 1000mm length.

Now the only function of the extensions is a little bit of levelling :thumbsup:

Picture shows one of the original leg tubes for comparison. Second pic shows the new centre bolt which can be further utilised for stability by hanging the power pack from it.

FlashDrive
26-01-2017, 09:54 AM
Well Done Matt ....

Col ...

Tinderboxsky
26-01-2017, 10:02 AM
Looks good Matt and should be much more stable.

Where did you source the custom M12 ring bolt from?

Cheers

Steve.

Wavytone
26-01-2017, 11:48 AM
Marine chandlers such as Whitworths should have things like M12 ring-head bolts, and most likely in stainless steel.

Matt, great job. I've looked at those tripods many times (and had one before) and concluded they're a bit flimsy for the scopes some people put on top.

Atmos
26-01-2017, 12:00 PM
Barely even looks like an EQ6 Tripod anymore :P

Kunama
26-01-2017, 12:06 PM
Steve, as Wavy mentioned Whitworths etc stock them. Then all that is needed is to cut to the appropriate length and then either grind or turn down on a lathe part of the threaded section.

Wavy, quite true, they are fine for very light loads but with the TOA + AZEQ6+ counterweights, finder, diagonal, binoviewers and eyepieces the load is approaching 50Kg, far too much for the stock tripod.

Kunama
26-01-2017, 12:20 PM
Here is a pic of the finished bolt on mine:

M12 316 grade s/s eyebolt from Specialty Fasteners fitted with the Synta black plastic nut, then a spacer that is locked onto the thread with an M12 s/s nut then the thread removed to allow rotation inside the tripod top plate.

Length of bolt from shoulder 101mm, from shoulder there is 45mm of thread, then 33mm of thread removed and finally 22mm of thread that locks onto the mount.

This works well on AZ-EQ6. For a T-Rex an extra 6mm of thread is needed so make the bolt 6mm longer or the spacer 6mm shorter.

The spacer is there to make it easier to grasp the black 'nut' to tighten the bolt.

issdaol
26-01-2017, 12:27 PM
Well done ! Will be interesting to see the comparison :)

Not sure about your Mongolian Master.........I believe there is a Grand Master Stainless Steel Pole Polisher in Victoria with more experience ....:question:

Tinderboxsky
26-01-2017, 01:04 PM
Thank you for your feedback Matt and Wavy.

Steve.

LewisM
26-01-2017, 01:27 PM
I am not sure if Matt used dairy-grade stainless, so perhaps that service is not available?

Had he used dairy grade, or that from a Maserati or Lotus, then perhaps the polishing service would have become an option. Using inferior graded stainless is counter-productive it seems.

(the "stainless" of the SW legs are a joke - I used to oil and steel-wool the ones I had continuously as they rusted quite rapidly. SW must use soy-bean industry standard stainless)

LewisM
26-01-2017, 01:32 PM
Matt - as beautiful a job as it is, would not the German forestry grade ash Berlebach Planet have been an option?

Kunama
26-01-2017, 02:12 PM
Where's the challenge in that Lewis :shrug: :D

bigjoe
26-01-2017, 03:42 PM
This looks great Kunama.
But all your work have been done out of dairy grade stainless, by a 50yr old Master BSer from Australia for twice the price!!!!:P
bigjoe

bigjoe
26-01-2017, 03:48 PM
Of course I'm referring to myself and no one else !Of course.
bigjoe.;)

LewisM
26-01-2017, 07:01 PM
Maybe back-fill the legs with lead shot for further stability Matt? I always contemplated that with my SW's .

I can happily bring down some antimony/lead shot for you in a big truck in a week and a bit :)

Tinderboxsky
27-01-2017, 08:14 AM
I tried that idea, using very fine grained sharp sand.

I did not find any worthwhile improvement in stability and found the tripod excessively heavy. It was not long before the extra weight got the better of me and I removed the sand completely.

Steve

LewisM
27-01-2017, 01:58 PM
I always put an old 3kg counterweight (I glued flet onto the bottom of it) in the EP tray of my HAL130 tripods, and it made them extremelly steady - 20 minute photo subs were no issue.

Kunama
27-01-2017, 03:45 PM
This change of the legs resulted in a weight gain of 4.7Kg for the tripod, no sand, cement or lead shot required. It is already almost too heavy for someone my age :sadeyes:

issdaol
27-01-2017, 06:13 PM
Yep you're an Ole Geezer now ......Should give those scopes to someone younger who can handle them :P

LewisM
27-01-2017, 06:29 PM
I think Matt needs to be prohibited from TA2017...he'll be using a Chinese mount after all.

Oh hang on...those SXW HAL tripods are Chinese. All good Matt, your'e in :D:P

Kunama
11-02-2017, 05:22 PM
Just a quick update to this thread.....

The tripod modifications have transformed the setup. The leg extensions are now just for levelling. Vibrations caused by hitting the OTA are damped quickly. Focusing does not induce visible vibrations.

issdaol
11-02-2017, 08:17 PM
Can attest to this....... :thumbsup:

Major difference to the tripod and mount...anyone owning this mount and tripod should do this ASAP !!:D

Atmos
11-02-2017, 09:56 PM
Well I have a HEQ5 and an EQ6 tripod, neither of which are the stiffest hehe
Maybe I'll replace both of them with nice wooden Berlebach ;)

casstony
02-03-2017, 09:50 AM
Hi Matt, is it difficult to separate the tubing from the tripod fittings? I'm thinking of doing this tripod mod and leaving the CGEM (which I just bought from Ian) set up semi permanently with a Telegizmo 365 cover.

I had in mind to make a heavy duty wooden tripod in lieu of a pier, but your mod might be simpler. I'd leave the lower fittings off and just the stainless legs would be exposed to the weather.

Kunama
02-03-2017, 12:37 PM
Hello Tony,
the cheap Chinese stainless tube is actually slightly smaller outside diameter than the replacements. The tubes are each held in place with just the 4 grub screws, undo those and you can wriggle them out.

To install the new tubes I did have to use a small grinding wheel to clean up the castings which weren't perfectly round. All in all it took me an hour to get it done.

LewisM
02-03-2017, 01:46 PM
Import the Berlebach from Teleskop Express directly and save a lot!!! When I got my Planet it worked out $240 cheaper than locally and that included UPS to my door. That's not insignificant savings.

casstony
02-03-2017, 01:51 PM
Thanks Matt. By grinding wheel do you mean a grinding stone attached to a drill or some other grinding tool? I'm thinking a stone would fill with aluminium.

Kunama
02-03-2017, 02:52 PM
I used a 45mm diameter x 15mm thick stone on my drill, worked well, being cast aluminium it doesn't clog like other AL would.

casstony
02-03-2017, 03:18 PM
Very good, off to the shops then. I see they have the same tubing you used on ebay for $25/m. They also have 1.5 inch tubing which might be useful for the HEQ5 tripods.

casstony
29-03-2017, 10:49 AM
So I tried enlarging one of the tripod castings to fit the new stainless tubes but gave up as it seemed to take forever and it's not great for the drill - just refitted the original legs.

However, after buying a digital caliper and measuring the tubes I've found that the new tubes are out of round. One dimension is the same as the original tubes (~50.8) while measuring perpendicular to the pipe weld measures 51.3mm. So I'm going to use the bench grinder to take the 'wide sides' off the tubes and try again, the next time the mount is off the tripod.

Kunama
29-03-2017, 04:33 PM
That's odd Tony, my tubes were round but the castings on the Synta tripod were out of round so a little bit of grinding of the 'sockets' sorted it. You could squeeze the tube a little in a vice :question:

casstony
30-03-2017, 06:14 PM
Softly, softly approach wasn't working so I cut a slot along the tube with the angle grinder and tapped the legs in. It's going to be out in the weather anyway so I'm not fussy about the finish. Now I need to find some sort of clamps to put on the lower legs for levelling. I'll save the original legs so they can be refitted if needed.

casstony
08-04-2017, 05:25 PM
I ended adding different length sections to each leg to make the tripod level. I used roofing silicone to glue the joints together and put a rivet in each joint. It's a solid and weather resistant tripod.
In hindsight it would have been easier to buy 1.3m lengths and cut each leg to size rather than do the join; stainless steel is a bit hard on the tools.

Kunama
08-04-2017, 06:53 PM
Beautiful finish Tony. Like the handrail caps :thumbsup: