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Broken stop tabs on a Century folding focusing hood

 
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Henry



Joined: 09 May 2001
Posts: 1439
Location: Allentown, Pennsylvania

PostPosted: Thu Mar 31, 2011 5:24 pm    Post subject: Broken stop tabs on a Century folding focusing hood Reply with quote

The one remaining stop tab on the frame of the folding focusing hood of my Century finally snapped off. There were two such tabs at the top corners of the panel cover, and they are subject to a shock force when the panel springs open. Since the panel is constructed of (I think) aluminum, after a few hundred or thousand openings, metal fatigue eventually wins out. I would have preferred to fashion new tabs out of brass and drill/tap these in place using tiny (00-90) machine screws, but I decided to first try gluing the L-shaped tabs in. Super glue was useless. I next tried two-part epoxy, and (he says with fingers crossed) so far, so good. Time will tell. I'll report back periodically.
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1banjo



Joined: 16 Nov 2008
Posts: 478
Location: kansas

PostPosted: Thu Mar 31, 2011 6:46 pm    Post subject: Reply with quote

yes I would try gluing it AND then put screw in it TOO
as the glue will hold it in place for drilling & screwing it
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Henry



Joined: 09 May 2001
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Location: Allentown, Pennsylvania

PostPosted: Thu Mar 31, 2011 8:01 pm    Post subject: Reply with quote

Easier said than done. Clearance is tight, and drilling two small holes in those locations will be very tricky and exacting indeed. That's why I'm hoping the epoxy holds.

BTW, to be clear, I did fashion new stops out of "U"-shaped brass stock (guess that's called a "channel"), by slicing 1/8" pieces off the stock with a jeweller's saw, then bending one leg of the "U" out flat to form an "L". I epoxied the short leg of the "L" to the aluminum cover plate in the same corner locations as the originals. But brass is soft, and that's another cause for concern: how will the replacements stand up to the shock? We'll see....
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1banjo



Joined: 16 Nov 2008
Posts: 478
Location: kansas

PostPosted: Thu Mar 31, 2011 9:02 pm    Post subject: Reply with quote

yes that why I would glue it first!
here where I live we have a GOOD Clock maker
I would take it out to see him to do the drilling
and so on
as he has really small screws & things TOO!!!
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45PSS



Joined: 28 Sep 2001
Posts: 3196
Location: Mid Peninsula, Ca.

PostPosted: Fri Apr 01, 2011 3:20 am    Post subject: Reply with quote

What 2 part epoxy did you use?

Did you clamp the parts until the epoxy cured?
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Henry



Joined: 09 May 2001
Posts: 1439
Location: Allentown, Pennsylvania

PostPosted: Fri Apr 01, 2011 9:01 pm    Post subject: Reply with quote

The epoxy was an el-cheapo I got at Horror Freight. It failed, but I don't believe that a name brand would have performed any better in this particular application. And clamping the part in that location is impossible: no clearance. I did apply steady pressure on the part with a needle-nose plier for 3-4 minutes until the epoxy started to set up, then let it set overnight.

After working on this project all afternoon today, I finally decided to drill and tap for 0-80 machine screws. I'll also need to fashion some sturdier "L" angles, as the stress on the corners is too great for the ones I already made. A trip to the hobby shop is in order for the screws and the brass shape!
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45PSS



Joined: 28 Sep 2001
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Location: Mid Peninsula, Ca.

PostPosted: Fri Apr 01, 2011 11:29 pm    Post subject: Reply with quote

Quote:
The epoxy was an el-cheapo

It's cheap for a reason, it won't hold pressure.

JB Weld, regular not the 5 minute, will be your best bet for an epoxy.

Tape or a weight can sometimes be applied in place of a clamp.

Also consider silver solder as it is very strong.
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Henry



Joined: 09 May 2001
Posts: 1439
Location: Allentown, Pennsylvania

PostPosted: Fri Apr 01, 2011 11:46 pm    Post subject: Reply with quote

Quote:
Also consider silver solder as it is very strong.


Does it work on aluminum?
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45PSS



Joined: 28 Sep 2001
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Location: Mid Peninsula, Ca.

PostPosted: Sat Apr 02, 2011 1:12 am    Post subject: Reply with quote

It might. I haven't done much aluminum soldering but what I did was difficult.
http://en.wikipedia.org/wiki/Solder technical solder data.
http://www.aws.org/wj/2004/02/046/ tips
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wrench



Joined: 08 Feb 2011
Posts: 6
Location: West Virginia

PostPosted: Sat Apr 02, 2011 7:56 pm    Post subject: Reply with quote

Silver solder is primary used to solder dissimilar metals together such as copper and steel, brass and steel, brass and copper, it however will not solder Aluminum, you can use a product called alumaloy found on the internet.
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Henry



Joined: 09 May 2001
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Location: Allentown, Pennsylvania

PostPosted: Sun Apr 03, 2011 2:08 am    Post subject: Reply with quote

I'm not going to solder this job. I obtained the needed 0-80 screws, nuts, and washers today at the hobby shop, also a 0-80 nut driver (*very* handy for those tiny nuts!) and some better brass shapes for the "L" brackets. The main challenge now is positioning everything and holding in place while starting the screw into the threaded hole. One needs at least three hands with seven fingers on each---very small hands, and very skinny fingers---and access is very tight at the corners of the frame. I think I've figured out how to do it, with the help of white liquid glue. Stay tuned....
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Henry



Joined: 09 May 2001
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Location: Allentown, Pennsylvania

PostPosted: Thu Apr 07, 2011 1:21 am    Post subject: Reply with quote

Update. Succeeded in installing brass angles at the upper corners of the hood frame, using 0-80 (1/8" long) round head screws and nuts. Fabricating the angles from 1/4" square brass tubing, doubled thickness for strength (flat-soldered two angles together for each corner), and drilling and shaping the angles, was very time consuming, though not technically difficult. It helps to have a Dremel tool and accessory drill press stand! Corners of the hood frame had to be ground out for clearance, likewise a bit of the corners of the gg frame to clear the screw heads. It's not easy to work with small 0-80 hardware with my monkey paw hands and fingers (OTOH, maybe a monkey could do it easier than I can!), but patience, persistence, and forceful vocabulary helps.

Time will tell about the longevity of this fix. Those angles take a real pounding every time the hood snaps open; it's no wonder the original aluminum ones eventually give out. That's one reason I decided to double the thickness of the brass stock by flat-soldering two pieces together. BTW, although most of the folding hood is not ferrous metal (aluminum?), the hood frame is attracted to a magnet, so I surmise that it's some kind of mild steel. I'm sure the next problem will be the springs giving out, at which point I think the hood will be toast (mm-m, rubber bands, anyone???).
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45PSS



Joined: 28 Sep 2001
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Location: Mid Peninsula, Ca.

PostPosted: Thu Apr 07, 2011 1:48 am    Post subject: Reply with quote

Quote:
monkey paw hands and fingers

No, you need to be like me and have thirteen thumbs.
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