Lock Unit for Canon 500 mm lens

Hi--

I have a defective lock unit (can google CY1-4292 to see a diagram) for my 500 mm f4 Canon lens (the metal piece on the inside of the hood that the outside bolt screws into is completely bent beyond recognition).

I got the part number from Canon--and also found out that there was a 4-6 week backorder, $75 for the little part, $6 special handling, and some other charges as well. I checked around on the internet and found this thread about replacing the Canon part with an e-clip for $0.75 rather than $75.00.

http://www.sportsshooter.com/message_di ... ?tid=21381

Two questions:
Has anyone had this problem and used a solution like this? I have found a few more posts that talk about having an issue with this part, but hadn't seen this solution before.

Second:
Has anyone ever looked at the inside part? Does it look like one of these e-clips?

Thanks!

I believe they are talking about something different, the e-clip they are talking about is a small metal part. see:

http://www3.towerhobbies.com/cgi-bin/wt ... LXAMF6&P=M

This pushes on to the screw to prevent it being unthreaded from the metal part you refer to in this case I would think.

It sounds like what you are talking about is another part of the assembly. From what I can see of the diagram there is a metal part which is attached to the hood by screws from the inside. This is threaded to take the fastening screw. On the inside of the hood is a metal piece which is attached to the screw using I assume an e-clip. I am assuming this is what is bent

It might be helpful to post an image of the damaged part, that way I could possibly guide you better. It may be possible to substitute something to repair the part.

I had to mangle the part to get it off. Even looking at it under a loupe, I can't tell what it used to look like--it just looks like a hammered and crumpled piece of metal about 1/2 inch long and about 1/8 x1/6 in width and depth, with a little hole for a bolt to screw into (I'm guessing at the dimensions; I'd need to look around to find it). I suppose if someone with a similar lens unscrewed the hood set screw, he/she could see the inside part that I'm trying to get.

Hope that helps...

I brought my 600 hood over to Canon last week as my hood locking piece had fallen off. I had the pieces but Canon replaced it with a new one at no charge. Not sure if being CPS had anything to do with it.

Based on your description of the part I think you will find it is quite a specialised piece. From what I can tell it is a rectangular piece of metal which is attached to the hood screw in such a way that it does not rotate with the screw when you tighten it, it's pupose is to spread the load from tightening the screw onto the barrel and reduce marring of the barrel surface.

If you were handy you could likely make the piece from aluminium stock, but the challenge would be to attach it to the hood screw. The only other option would be to find a nylon screw or a nylon tipped screw to use in place of the existing screw and just us ethat to hold the hood on, couldn't guarantee it would hold as well or that it wouldn't marr the barrel though. Unfortunately it may be that you need to pay the exorbitant price for a part that costs less than $1 to make, mor ethan likely.

Thanks for the input. I think I'll try to manufacture something out of hard plastic (like a plastic kitchen cutting board). I'll let you all know how it works.

Nancy:

Can you remove the thumbscrew from the hood now that the E-clip and and "brake shoe" have come off the end of it?
If so, post a closeup picture of the screw, and measure the diameter of the tip. Maybe I can make something for you. If you don't take the hood off very often, a simple "shoe" drilled to fit the screw will work adequately. You'll just have to be careful not to drop it when you take the hood off. Unlike the original, it won't be locked onto the screw. If I can see what the screw looks like, I may be able to come up with a way to keep the "shoe" from coming off.

aj

Thanks for the offer. I don't take my hood off that much, so something like you're suggesting would work great.

But the screw won't come out easily (maybe it will if I take apart the ring on the inside of the lens). Regardless, I think I can figure out what the diameter of the screw is. I also think this contraption is the same as the one on my 400 lens, which means at least I can see what the metal used to look like. Basically it looks like a miniature Jersey barrier about 9/16" long, with the narrow part (analogous to top of a jersey barrier) matching up with a narrow groove on the lens, and the fat base against the screw.

I'm just getting ready to head out to the Cascades (with the lens hood taped on with gobs of blue non-residue tape), so will be in touch when I get back. Again, thanks for all the help!

-Nancy

Again, thanks for the offer, and I'll check in when I get back.

After thinking it over, and getting your response, I think this is the simplest fix:
Make the Jersey barrier out of any material you like. Hard wood, hard plastic, or aluminum. Just size it to fit the groove on the front of the lens where the original part goes when you put the hood on. Slip it into the groove, put the hood on and check to see that it will lock in place. You might have to fiddle with the height of the Jersey barrier, or at least the center of the barrier where the screw makes contact.
Once you are happy that the fix works, simply cement the barrier in place on the lens. I would use just a dab of clear silicone caulk. I would also put the barrier so it's at 12 0'clock when the lens is in the landscape position. This way you can use the screw as a crude sight to roughly aim your camera at your subject.ASnd it will make it easy for you to put the hood on in the right position so it matches up with the jersey barrier.
The silicone will hold the part securely enough that it won't fall out, but is not so strong that you can't remove it later if you want.
If you need help with the barrier, let me know when you get back.

aj