Builders Level

[JFREE]

I want to make my own Builders Level.(I use that name because thats the name of the closest thing, to what I want, I've seen in stores.) The machining part I can handle, my problem is with the scope, and mostly, the level vials. My MC.Master-Carr catalogue has alot of vials, but I dont know what sensitivity I need. My goal is 1/4" at 100ft.

[SGW]

Ha! I thought about doing that, too; then I finally ended up buying used transit. But it ought to be a great project.

1/4" at 100' is 0.0025" at 1'. Inches-per-foot is frequently how you see accuracy specified, so you can look for that. I think you'd probably want at least 0.0005"/ft accuracy in the level to ensure the kind of accuracy you want in the readings.

Or, 0.0025"/ft translates into about 8 1/2 minutes of angle.

I assume a rifle telescopic sight will take care of the scope. but I don't know what power you'll need for what you're planning. A "real" transit has a scope power of 24X or so, I think, but it sounds as though you're envisioning use at relatively short distances so you probably don't need that much magnification.

Check out http://www.antiquesurveying.com/index.htm for used transits and builders levels. (Usual discalimers; no conenction except as a satisfied customer, etc.) The "collectible" stuff is expensive, but he also has some transits and levels that aren't too expensive. Of course, if the main idea is to BUILD one, then it's irrelevant, but I wouldn't be surprised if you can buy a used one for what it will cost you to build one.



[This message has been edited by SGW (edited 11-27-2002).]

[docsteve66]

JFREE: Do you want to level things at 1/4 to 100' or build a instrument with that capability?

[Thrud]

[I have seen transits go for nothing at government auctions - $125 for a $18,000 transit, Roof prisms & laser for $300 :eek

[mikem]

Have had two used ones so far and neither one worked quite right. The first one had three hairs for sighting and one was broken, so I sold it. The next one is a Power Craft and it is so cloudy that I can't see through it unless the sun is bright enough to fry eggs(which isn't that often in Nebraska)so I am thinking about acquiring number three. New ones are not that expensive, about $250. If the next bargain one doesn't work right I'll buy a new one.

[JFREE]

Thanks for the input SGW. My Idea Is to build one. Dont we all like showing off the latest gadget we've built in our shop? Even if we could have bought a real one for the same price. It would be nowhere near as cherrished. Besides I catch alot of flack for buying tools,but if it looks like I made it with stuff I had laying around I'm ok.
The 1/4" in 100' was the advertised accuracy of the store bought one. I think it can be beat, but I would hate to build one less accurate.

[SGW]

Well, more power to you; and how about writing it up as you go and sending it in to HSM as a construction series?

You may want to get an older surveying book (1940s or 1950s vintage), one that describes how to calibrate/align a transit, to get an idea of what matters for accuracy and how commerical transits deal with error.

[docsteve66]

Used transits are ususaly easy to repair ifthey are mechanicaly sound. REplacing a cross hair is often done in field. Done it my self a few times. Catch a small spider, touch a neeedle to its rear end and it will put out a thread. catch the thread on a small forked stick, wet it and lay it across the place where the old thread (hair) was. don't try to stretch it too tight, else it will break when dry, too loose and it will sag. put a drop of shellac on the ends. Most of the old travel boxes had a small bottle of shellac for this purpose. There are (again old transits) cross screws for adjusting the position of the hair tube so it is centered. If the position of the hairs appear to move when adjusted you have a parallax problems whch can be cured by moveing the screw on front andrear of the tube until the line of sight is parallel to the movement of the hairs. Replacing the stradia hairs (used to ESTIMATE distance) is more difficult. ususaly the surveyer "calibrates" by installing the stradia hair, looking at the stake at a distance, seeing how much his instrument subtends the stick and using that figure for THAT one instrument.

The tube (eyepiece, lenses, mount etc) is precision in much the same way a lathe is precision- the opeator makes it precise by his techniques of operation.

A careful man can adjust the levels, scales etc in the field using mostly a tape for distance, stakes and electricians tape. THe levels,as was mentioned in another thread are self checking.

Un-needed sensitivity is a waste of set up time, and even a source of error (hunting for seconds and miss a degree.
SGW has good advice about getting an old book and studying it. There are several military manuals that do a fine job of explaing how to dis-assemble, clean and reapir the optics.
Steve