Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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Hi everybody.  I'm in the middle of building a parallelogram mount for my 25x100 binoculars and I am about to make the part that swivels and holds the binoculars themselves.
In the pic provided, you will see two RED ARROWS. These point to the "C" shaped piece of wood that will ultimately hold the swivelling piece that holds the binoculars. I need to know engineering-wise which one would be more stable. Having the "C" shaped piece on the inside or the outside?
My guess would be the one on the outside, but I need some engineering advice on which would be more stable.
Thanks for your help. 
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12581
Loc: Cumberland, R I , USA42N71.4W
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I don't see that either one would be more stable than the other. However, the one on the left would have unencumbered movement. The one on the right might need rounded shaping at the corners to prevent binding.
The vertical L piece should not be made with only one screw hole. Both your C piece and the L bracket should have more than one whole for vertical adjustment of the L bracket, which will insure ability to keep the load of varying binoculars on the center of gravity axis.
edz
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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
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Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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Thanks Ed. I don't understand why the vertical L piece would need more then one screw hole because it needs to turn up & down. Does anybody have some suggestions for the rest of my mount?....Here is what I have so far.
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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Buck
sage
Reged: 04/29/05
Posts: 471
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Markus
I'm not a trained engineer but I'd go inside. The "C" would be shorter making it better to take the stress of the center bolt holding the L bracket with the Binos.
Just my $.02 which is exactly what it is worth.
Buck
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Astrowood
super member
Reged: 04/02/05
Posts: 161
Loc: New Brunswick, Canada
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Markus
This C bracket attachment can be accomplished a couple of ways, A good rule of thumb is to use as few connections as possible,and have tight tolerances between the bolt holes and the fasteners. Ed's point about multiple holes in the L bracket may be a factor if you plan on using a variety of different binoculars and the center of gravity (cog) is widely different between them.
The diagram below may be a useful illustration of how you could determine the approximate cog. While I do not have an exact method of determining what the cog of a given set of binos is. By estimating a horizontal line through the center of the objective lens, seems reasonable given thier weight. This has worked for me over a half dozen times.
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Roy
22 X 100 Antares
20 x 80 Meade
couple of Pmounts
8" F/5 Dob
4" SkyWatcher
Observing Chair
Wooden gadgets to numerous to mention
Observing Buddies "Max & Sam"
www.astrowood.com
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Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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Thanks Roy, This diagram is very helpful. I only intend on using my 25x100's on this mount. I have seen your mounts on youtube and I will keep this in mind. 
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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patter1
professor emeritus
Reged: 01/19/05
Posts: 597
Loc: Canada
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Assuming the outside C has wider spacing than the inside C (it looks like it would), the outside C will be more solid, at least from the standpoint of putting less lateral force on the two vertical bolts. If you can use one long vertical bolt instead of two, that'll be better still.
Roy is right on about the value of keeping the bolt/hole tolerance tight. It also would be good if you could put a smooth sleeve/bushing around the bolt threads so that they don't wear through the wood when under lateral pressure. Or use bolts that are smooth where they're in the wood.
Nice work so far.
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Patrick
8" f/6 NewStar dobsonian
Orion Starblast 4.5" f/4 mini dobsonian
42mm SuperView, 17mm Nagler T4, some other cheapies
Omcon 7x50, Oberwerk 11x56, Olympus DPS-R 7x35, Olympus Magellan 8x25
homemade 50mm right-angle bino-scope prototype
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Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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Thanks for the much needed advice everybody. I went out and bought more parts to finish up the p-mount today and instead of having wood I bought two STEEL L-brackets to add to the mount.
One will be bent into a C-Shape and the other will remain L-Shaped to hold the binoculars. One thing is I don't know where to find any teflon washers.  I'll post more pics of the mount when it is completed. 
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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Astrowood
super member
Reged: 04/02/05
Posts: 161
Loc: New Brunswick, Canada
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Markus
Phone Spaenaur 800 number and ask for a dealer location in Hamilton. You should be able to find many dealers in "Steel Town"
http://www.spaenaur.com/
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Roy
22 X 100 Antares
20 x 80 Meade
couple of Pmounts
8" F/5 Dob
4" SkyWatcher
Observing Chair
Wooden gadgets to numerous to mention
Observing Buddies "Max & Sam"
www.astrowood.com
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Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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Thanks Roy.
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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P-mount is just about done. I went with the "inside" C-Bracket today. All I really have to do now is mount the binocs on there and she how everything feels.
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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camvan
Carpal Tunnel
Reged: 05/02/05
Posts: 2086
Loc: British Columbia
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lookin good Mark, but I'm wondering about the lack of wing nut or something to tighten the tension if you decide you want a position to hold. 
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Cameron
"Aperture can only be replaced by even more aperture. Dark transparent skies cannot be replaced by anything else." - Stathis Kafalis
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Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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I have lots of wingnuts....lol. I'm using locking nuts on the part that turns left & right, and in two other places. There's a wingnut for the steel L-Bracket to hold the altitude of the binoculars. All I really need now is some kind of handle to tilt the bins up or down.
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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pic 2
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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Astrowood
super member
Reged: 04/02/05
Posts: 161
Loc: New Brunswick, Canada
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Markus
If I may, just a suggestion. Your C bracket looks good and solid, and using lock nuts is a good idea as you can back them off if they are to tight and you need more play at this joint. My suggestion is to use teflon washers in each of your "arms" of the C joint, to avoid wood on wood contact. If you do not have teflon washers, try using one of those plastic milk jugs and cut yourself some thin washers, and I'll bet you feel a noticable difference.
Just a thought.
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Roy
22 X 100 Antares
20 x 80 Meade
couple of Pmounts
8" F/5 Dob
4" SkyWatcher
Observing Chair
Wooden gadgets to numerous to mention
Observing Buddies "Max & Sam"
www.astrowood.com
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Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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Thanks for the suggestions Roy. Coming from someone like yourself who has the experience with P-Mounts, I am all ears because this is my first attempt at building a P-Mount.
In between the wood is metal washers and no wood contact at all, but your suggestion of the milk jug washers is great. I saved a whole bunch of those milk jug washers from my old dobsonian mount, so I just might be able to use them on my P-Mount. If not, I can always cut up some more and insert them between all of the wood to avoid "wood on wood" contact like you suggested. One other thing, I made sure to use glue & screws for the top & bottom plates and also in the C-Joints to maximize strength. I haven't tried the binoculars on the mount yet, and I won't until everything is ready to go, and even then, I plan on attaching a 10 pound barbell weight to make sure everything will hold.
That way, if something gives, it won't be the binoculars and it will only be the weight that falls if something were to go. Do you think the L-Bracket in the pics is strong enough to hold my 25x100 Burgess binocs? Do I place the milk jug washers on TOP of the metal washers ?
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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mark22c
sage
Reged: 08/12/07
Posts: 343
Loc: cornwall UK
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nice one mark, the mounts looking really good so far
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opticron "imagic" BGA SE 8x42 roof's
10x42 roof's
meade/bresser (lidl) 10x50 porro's
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Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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Thanks Mark. I still have to test it out in my yard on a chair, so I'll make sure to make a first light report with the 25x100 bins and the P-Mount whenever I can. This has been quite the task building my first P-mount, because all I had to go by was pictures. I did however, get to look at the half moon last night for a brief moment between rain and clouds with my 25x100 binoculars and the sight was jaw-dropping to say the least. 
Cheers
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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Astrowood
super member
Reged: 04/02/05
Posts: 161
Loc: New Brunswick, Canada
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Markus
I did not notice that you had steel washers at the joint in the C bracket - give it a try.
Quote:
Do you think the L-Bracket in the pics is strong enough to hold my 25x100 Burgess binocs? Do I place the milk jug washers on TOP of the metal washers ?
The L bracket may be strong enough to hold your binocular, but it may not be rigid enough, so as to not flex when the bino is in use - give it a try anyway.
Secoundly, if you do use a plastic washer, it would be placed against the arms of the C that actually move. In your case, on top of the washer on the bottom connection, and reverse on the top.
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Roy
22 X 100 Antares
20 x 80 Meade
couple of Pmounts
8" F/5 Dob
4" SkyWatcher
Observing Chair
Wooden gadgets to numerous to mention
Observing Buddies "Max & Sam"
www.astrowood.com
|
Markus
Postmaster
Reged: 12/26/04
Posts: 5395
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Thanks again Roy, you've been a great help here, I'll give the plastic milk jug washers a go and place them right where you said to. If the L-Bracket has too much flex, I'll make one out of wood with a corner brace.
Cheers.
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25X100 Skymasters
15X70 Skymasters
Home built Parallelogram Mount
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