A806 Timer Repair.

[d-jones]

Thank you very much for the compliments guys.

With any luck I'll still be worthy of them when this project is finished. Now since it was suggested that I might trim the rivets that are too long and still make them work(at least I think that's what was being suggested) I thought I'd make this quick drawing so I could explain whats going on with these semi tubular rivets.

 

The little image on the left simply shows a cross section of one of them. The hole in the end that's labeled "D" will be the exact same depth on all 1/8" diameter semi tubular rivets. Only the overall rivet length will vary depending on the application.

 

The image on the right shows a properly sized rivet that's been correctly installed in an imaginary Bakelite timer body, and the tubular end of the rivet has curled around and come in contact with the tab labeled "B."

 

If the rivet is too short for the hole it's being installed in, surface "A" of the rivet set will come in contact with tab "B" before the end of the rivet has been properly rolled over. At that point nothing more can be accomplished by further squeezing. You'll just be squeezing the Bakelite.

 

If on the other hand the rivet is too long, the tubular end will continue to roll over until the point labeled "C" on the rivet set bottoms out in the hole. At this point if one continues to squeeze, the solid brass portion of the rivet will begin to compress and as it does it will swell exerting outward pressure on the sides of the hole it's installed in until the Bakelite brakes apart. This would be a very bad thing, and it explains why a rivet that's too long for a particular hole can't simply be trimmed down.

I hope this clears things up.

[this post was last edited: 10/26/2013-18:15]

 

[jetcone]

David

absolutely fascinating! Thank you for the photos and theory of rivets! Can you show what your grip gauge looks like and how it is used? And that tool for compressing the rivets looks professional not like the silly pin tool you see in hardware stores, which barely works.

 

I bet your method would also work for restoring the silver contacts on the bars when they pit and breakdown too. I have seen websites where they probably can be ordered but being silver "they ain't cheap".

 

 

 

[d-jones]

Hi Jon

The Van Nuys Airport is just a hop skip and a jump from Hanson Rivets, so I stopped by my toolbox to use the grip gauge, then left it there and went on to buy the rivets and the rivet sets. So this means I don't have it here with me. But I did find this image on eBay of another one that's just about a dead ringer for mine. Too bad the photo's so blurry.

 

The idea is to simply insert the tool into the hole you wish to measure until it comes out the other side, then hook that little flat on the end portion up against the bottom  surface and read the number that's visible at the top. The number you see will be the grip length for the rivet you need for that hole. I measured a random sampling and thought I had all the bases covered. Obviously I screwed up, but I'll fix that tomorrow.

 

And yes, the rivet squeezer is one I've used extensively for aircraft work. On a lot of smaller rivets a rivet gun is just total overkill.

 

 

[jetcone]

Thanks

Dave that is a cool tool set. For timer work its invaluable as you have demonstrated.

 

 

 

[d-jones]

Jon

I'm glad you found that little drawing useful. If you wanted to do this sort of thing yourself sometime, Hanson Rivets in Pacoima has a web site where you can order the rivets, the rivet sets, and a squeezer that's almost identical to mine. They're very friendly people and I found them extremely helpful.

 

As I promised, I went out to Pacoima again today and picked up the needed rivets, so I'll go ahead and finish this up.

 

The two bad rivets indicated by the red arrows have been replaced here, and all three switches in the foreground of the photo were installed. On the other half of the timer body the two switches indicated by the white arrows had to go in before the upper switches could be installed.

 

[d-jones]

Here the remaining switches are finally installed. All six of these switches are spring loaded to be in contact unless a cam has come along and pushed them down. The two nearer ones also have contacts below them as seen in the prior photo.

 

[d-jones]

And here's the view from above. All the solderless connector tabs are back where they belong and firmly held in place.

 

[d-jones]

Now reassembled with a motor borrowed from one of the other timers that was damaged in shipping, this one is ready to go back into service whenever it's needed.

 

It's taken a while to finish, but now that I have all the rivets and the required rivet sets for this sort of work, I wouldn't hesitate to do it again. I hope anyone that's been following this wasn't too bored with all the delays. In spite of a couple of minor setbacks, this has been kind of fun.

 

Now all that's left is to figure out a way to label the terminals properly. I'll have to think about that a bit.

 

[kb0nes]

David, You accomplished a wonderful repair and you documented it flawlessly! Thank you so much for taking the time to share it with excellent photos along the way (not to mention the hand drawn rivet cross section illustration!). The sharing of your efforts will go a long way towards encouraging others to try it for themselves.

Somehow I have a hunch you are familiar with Cleco Skin Pins. Riveting is one of those forms of metal work that is becoming a lost art unfortunately...

 

[arbilab]

The businesses doing this several years ago are disappearing. This is a bible of rebuilding axial-cam timers. Very fine work.

"Don't crack yer bakelite." Why didn't they use HDPE? Chumps! I mean really. Bakelite? In the post-60s?

 

[kb0nes]

HDPE

While HDPE would be cheaper and less fracture prone, it wouldn't be well suited to this application. HDPE melts at ~250 Deg F. If one of those connections gets a bit warm the plastic would flow and reduce the clamping pressure of the rivet. This would create a death spiral likely leading to a fire.

Bakelite, while more fragile, is thermosetting and won't soften with heat. Even today phenolics are still in common use in electrical applications. We machine a lot of phenolic insulators and spacers, and boy we sure wish we didn't have to! Its a messy plastic to work with. It's far nicer to work with any thermoforming plastic like Delrin, Nylon or the various PE's but they all soften with heat too.

 

[d-jones]

I just though I'd take a moment to say thanks to those folks that stopped by this thread and left thoughtful or encouraging comments. It's always nice to feel that what you're doing is useful or helpful in some way, and based on the number of views it seems that there was a fair amount of interest in this subject(either that or a couple of guys checked in very frequently), but it was still very nice to find the occasional comment left by the handful of folks that took the time to leave them. So Ralph, John, Ken, Diomede, Robert, Jon, Phil and Rick, thank you very much. Your comments were appreciated.

 

And Phil, yes I do know what cleco's are. In fact any aircraft mechanic worth his salt will likely have at least a dozen or so in his toolbox. Sheet metal mechanics will frequently have hundreds of them, both the spring type and the threaded type.

 

Now on the off chance that someone else might want to do this as well, I have some additional information to share. The orange arrows in the photo below are pointing to the rivet sets. The longer rivet set fitted into the upper fixed portion of the squeezer head is part number CA2004-9 1/8 R.D. x 3/8 LG. It's described in the paperwork that came with it as an "oval head squeezer die." The term "oval" is important because there are two common head types on these tubular rivets. The ones found in this timer were all of the oval head type. The other type is called "truss head" and it has a significantly larger head diameter, so they can't be used.

 

The other rivet set fitted to the movable ram is part number CA2005-8 1/8 R.D. x 1/4 LG and it's described as a "tubular rivet squeezer die." Both of the rivet sets had to be ground down to reduce their outside diameters enough to make them fit into the tight spaces they needed to be used in.

 

The rivets all have the same basic part number that's then modified with a dash number. They are:

MS20450-C8-B8

MS20450-C8-B9

MS20450-C8-B10

MS20450-C8-B11

MS20450-C8-B12

MS20450-C8-B13

 

When you're using this type of rivet squeezer you'll want the handles to be just about fully closed when the rivet is fully squeezed. In order to accomplish this the ram is threaded onto a movable shaft which allows the user to thread it in or thread it out depending on the need. The ram can be a little tight making it hard to rotate, so a hole is provided(see the blue arrow) so that an object like a small Philips screw driver blade can be inserted for extra leverage. I was just on the Hanson Rivet web site and didn't see this squeezer listed anywhere, but they have them on display at the walk in sales counter so they're definitely there if you can't find one locally.

 

 

[this post was last edited: 10/29/2013-16:33]

 

[jetcone]

I need one

I want one oohh Santa??

 

 

[rp2813]

Excellent Work

David, your thorough documentation of the process will be a great addition to the archives here.

 

Ralph

 

[ricinalberta]

Great Work

Thanks for documenting all this in such a succinct way.