self-levelling tribrach ?

[Billy9m888]

I am looking for a self-levelling tribrach for a prism ?
I'm sure I have seen one in the distant past (Formby Surveys in the UK in the 1990's, or was it a dream ?)
It may have been a Leica/Kern\Wild product ? Part number anyone ? one to sell ?
I have seen the AD12 Self Levelling Tribrach but that is way over the top for what I need both in terms of size, weight and cost.
Thanks in advance

[jcoco3]

The AD12 looks Interesting, but I can see why it might be overkill for just a prism. I have never seen what you are talking about, but I would imagine many like it exist somewhere.

Is the wild part the GAP 1 here?
https://www.swisstek.com/rental_equipment.htm

Not sure how level you want the prism to be and if it would suit your needs, but could you suspend a mini pinpole and prism below a tripod like a plumb bob? Would not be very useful in the wind.
https://www.baselineequipment.com/seco- ... compatible

[Ioannis]

It’s something that I also like to have but is very expensive..
https://www.sccssurvey.co.uk/ad-12-self ... brach.html

[Wags]

viewtopic.php?p=20928#p20928

[jcoco3]

Wayne, thanks for that link I saw your creation a while back when you originally posted it, but couldn't remember what to search for to find and repost it.

Seems like a viable solution.

[LRS-SCAN]

You get this from Taobao

https://item.taobao.com/item.htm?spm=a1 ... 5828927014

[tadol]

This may be totally off base - but some years ago I saw a need for something similar, and developed a few prototypes -

I was working on a scanning plumb-bob - it was basically a pair of my 80mm targets, set a fixed distance apart (as a reference value) which swung from a gimbal mount. The point on the bottom weight could be set over a reference point, and it would self align vertically. On the top of this assembly was mounted one of my blue discs, allowing a larger (150 or 200mm) target to be mounted directly above the reference point. Now, with my mini-prism adapters, one could mount a mini-prism directly above that point, then once the center is shot, a spherical target could be substituted for the prism, and used in the scan data.

Problems I never completely worked out - how to keep the plumb-bob stable in windy conditions, how to keep the distance between the small targets fixed accurately enough to act as a sub-mm reference value, and finally, how to put it all in a case so it could be shipped easily and maintain accuracy.

The one part I did have - it was mighty darn cheap to build - and pretty darn accurate -

[fobos8]

Problems I never completely worked out - how to keep the plumb-bob stable in windy conditions

One method to get round this problem is the submerge the plumb bob in a bucket of oil

[tadol]

Yeah - oil would help, but it would introduce just a couple of other problems -

[Billy9m888]

I am pretty sure it was red and ran off batterires.