6 replies to this topic

[rmorein]

This concerns assembling the scope pictured here:

https://astromart.co...opecomplete-kit

 

The method I envision is:

 

1. On a tarp, assemble the legs to the mount, including the spreader and slow motion cables.

2. Tip to vertical.

3. Install the counterweight shaft and weights.

4. Attach the tube.

 

This minimizes the chance of losing screws for the slow motion cables, which are mere M4. If they fall from my grasp, they will land on the tarp near the mount. 

 

As a slight variation, the lowest section of the mount, the azimuthal base, looks suspiciously like a modern Vixen metal tripod base. The legs/base could be tipped vertical before the rest of the mount is attached.

 

How do you handle this?

Edited by rmorein, 16 February 2025 - 07:52 AM.

[apfever]

Mounts like this are rarely taken off the base. The base is also called the tripod hub.  Observing tarps are iffy, some do and some don't. I don't. The biggest thing with a tarp is the trip hazard around the edges where the ground will inevitably hold it up a little. If you snag a foot on the edge, you will likely be heading for your scope is bad fashion.  A sudden trip with inevitable fall causes brain shut down and jerk reaction - Hands out and anything upright is fair game. That includes a bear hug if you hit full frontal. Use a small  ground cover under the mount for assembly if you are concerned and you don't tarp. 

 

Place the mount upright and splay the legs out if you have room.  Then pick the mount straight up to desired height and let the legs naturally come up under it.  I find this a little easier than sideways assembly.

 

Floppy controls are the last thing I put on. They are the most inconvenient thing to work around during assembly.  Don't back the set screws all the way out to put them on, leave some safety margin. Slide them on till they tap the screw, then back the screw out a hair till the floppy slides on - followed by tightening all in one move.  The flat on the stub will be in a convenient position because that is where you will put it when you take them off. YES, it is important to not loose those screws since they are likely an out of production Japan thread pitch (M4X0.75) that is hard to replace. Taps and dies are still readily available.  Safety is your call, do what leaves you comfy.

 

The floppy set screws are often nickel plated brass. They are soft and can easily mushroom.  It is common to find these locked into the floppy because the tip threads have been slightly squashed. They will have a natural 'stop' that just lets the floppy slide on and off.  Don't over tighten. 

 

Turn the mount saddle sideways so it will hold the OTA easier during assembly.  Slide your hands together under the OTA and they will naturally come to the balance point you want in the center of the cradle. 

Edited by apfever, 16 February 2025 - 09:21 AM.

[rmorein]

That's good advice, which has problems with this mount. The leg bolt holes are not holes, but slots open at the bottom, so the legs could fall away during the lift. The spreader is non adjustable, requiring that cylindrical pins captive to the legs be precisely inserted into holes in the spreader.  The floppy screws are not held by any threads in the floppies. They thread into the mount through threadless holes in the floppies, and must be completely removed for assembly / disassembly. They have collars which thread down for tightening.

Edited by rmorein, 16 February 2025 - 06:19 PM.

[Jay_Reynolds_Freeman]

[...] The leg bolt holes are not holes, but slots open at the bottom, so the legs could fall way during the lift. [...]

I had a mount with that problem once: It was unusable in that configuration because the leg bolts tended to wiggle out of the slots during use, and if not noticed and caught early, everything but the legs would collapse and fall onto the cold, hard ground. The best fix I could come up with was embarrassingly crude: I didn't want to drill holes in the slotted piece because I worried about structurally weakening the soft pot metal, so I cut a plywood disc large enough for the slotted piece to sit on, drilled holes in it and used u-bolts to clamp the slotted piece to the disc. That left many options for attaching the plywood to a sturdy tripod or pier. I expect a machinist could come up with something better, but be wary of weakening the slotted piece.

 

On the bright side, those tripod legs look like mine, and they are wonderful! I use them on other, better designed mounts that came with spindlier legs.

[apfever]

HA, well my suggestions for the legs and floppies sure flopped for your situation.  I'm not a fan of those slotted hubs either for the reasons stated above, but I have a few of them because that's just the way some did it. 

 

Check your floppy set screw threads. If they are standard M4X0.7 then they can be replaced with something functional if not original.  If they are M4X0.75 then step up the precautions. You will likely have a bunch of the archaic JIS (Japan Industrial Standard) threads on your scope if find just one.  

 

After WW II there was a global cooperation to standardize a lot of things.  One of these was specifically to standardize screw threads. I think the conference was held or started in the 50's or maybe late 40's.  A lot of the JIS threads were discontinued and a lot of the old stock was bought out by telescope makers.  They probably got a lifetime supply for peanuts. 

[rmorein]

They are M4X0.75. I had to have some spares, so I found that 0.70 screw in far enough to obtain purchase before binding, locking down with threaded collar nuts. I don't want to use them.

 

The thread is available, but only in hex-head. The collars are not.

[ccwemyss]

The slotted tripod brackets drive me crazy. On one I epoxied washers to the inside. On another, I made a three-pronged bracket with a center hole, so that the bolt holding the upper section would go through and clamp it in place, with the prongs extending out into the brackets, bent at just the right angle so the bolts would pass through and be held in place. The prongs only need to be strong enough to hold the weight of the tripod legs while it is being carried, but the bolts need to be tightened before applying any off-balance load. 

 

Chip W.