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Mido pressure tester cylinder problem

karlmansson

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Apr 20, 2013
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Hello!

I just got an old Mido Multifort Superautomatic pressure tester. It has seen better days but a little cleaning up did wonders for the looks of it. Problem is, the gasket for the piston that builds the pressure is shot. I've tried replacing it with a leather disc but to no avail. It appears that the oulet from the cylinder, I'm unsure if there's a valve there, is either jammed, clogged or both.

Is there anyone here that has any experience with these and maybe even experience in servicing them? It's the same machine as the one in the linked image.

Best regards
Karl

s-l1600.jpg

For more pictures, please see this ebay auction (ended): Mido Multifort Superautomatic Pressure Tester | eBay
 

karlmansson

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I managed to do some trouble shooting on my own. It seems I've been mistaken about how the cylinder works. I thought that the pressure build up would open the valve in the cylinder but I now realize that it is in fact the tip of the piston that pushes the valve open, allowing the air that has already been compressed in the cylinder to reach the rest of the system. Which means that the seal in the piston has to be very tight as I will have to compress the air inside the cylinder to about 4 bar for each stroke.

Two issues remain: if I am to really get at the valve in the cylinder I will have to take it apart. And I can't tell if the valve section is threaded onto the cylinder or if it's a press fit. The cylinder has a very thin wall and I'm afraid to break it. Is it a press fit, solder joint or thread?

The second issue is still the material for the gasket. Leather will not do, it isn't elastic enough. Rubber?

image.jpeg image.jpeg image.jpeg
 

karlmansson

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Well, I worked it out. The gasket that is, still haven't taken the cylinder apart.

I glued two pieces of bicycle tubing together using neoprene cement and then cut and sanded the gasket on the lathe. The tool build up to and keeps 3 bars easily now. Haven't gone up to 4 yet, it's old and has seen some hard times by the looks of it.

This has been and enjoyable monologue. Thanks you stopping by! No, thank YOU!

image.jpeg
 

proto57

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Nov 12, 2010
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Hi Karl... "You're welcome" for my stopping by! Took me a year, though... because I only just got my Mido Multifort pressure tester.

Beautiful device, isn't it?

Anyway, great tips on the plunger seal. I will probably have to replace mine at some point, only the leather is in surprisingly good condition. My leaks are elsewhere, and so I wanted to ask you a couple of things (if you see this, or anyone with experience taking these apart).

I have a small leak from the immersion rod hole in the screw-down cap. I'm assuming there is a compressible "O" ring in there, or perhaps another leather or felt compression washer. And it is clear that the disk on the underside of the cap (the one held in place by the three screws) holds that compression washer in place, and compresses it.

Trouble is, after taking out the three screws, that disk will not come out of its recess in the cap. I do think that if I could give it little whack or two, it would come out, but I'm not sure what to whack. I tried putting rods in from the other side, but it is hard to see where there is any "shoulder" to push against. I also think there is a tube in there, which it seems, presses on the compression washer... but not sure, hard to tell.

So... did you take this assembly apart? How?

There are also small leaks from the main cap gasket, and from the pump (very small, all of them... I used soapy water to find them). But I suspect the pump leak is not from the plunger, but from the little "one way" valve on the plunger end. So I have a few seals to replace.

Thanks for any help. Thanks for stopping by!
 

karlmansson

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Apr 20, 2013
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Hello!

First I saw the thread and thought it was neat that someone else was asking the same question as me. Then I saw who started the thread...

It’s been so long now since I had mine apart that I can’t really remember what it looks like inside the part you are asking about, and if I even had that part apart. I know some of the seals in mine are pretty hard but they still work. Can you post a picture of the part that is causing you grief? I won’t be able to have a look at min for a couple of weeks.

Best regards
Karl
 

proto57

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Karl! Thanks for getting back to me.

The part that is stuck is the one I've labeled "seal compression disk", because I suppose it squeezes the O-ring or seal in the cap. That is the part stuck in there. I can take out the screws no problem, but the disk won't budge.

Mido_Cap_Assembly_1200x_labels.JPG

The thing is, if I knew that under the seal (on the top side of the seal, as the instrument is normally standing) there was a washer, I could put a soft drift rod in from the top and drive out the disk.

But if the upper seal retainer was NOT a washer, but a "ledge" that was part of the cap, then of course I cannot drive the disk out by pushing against it.

I did try some gentle to moderate taps, but didn't want to hurt anything. I may try my large case back opener in the screw holes to see if I could twist loose the disk a bit, but really have little hope it would move. I may also chill the parts, because I think if all parts shrink a bit, the relative size of the hole would increase. Not sure, either. And I am wondering/worried if a past owner glued that sucker in there... it is really tight.

Hopefully the pic jogged your memory, and you did have this apart. Thanks again for your time...

Rich.
 

karlmansson

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Sorry no, I don’t remember that part. I know I installed new seals in a couple of places but not sure about that one. I’ll have a look when I get back home.
 

proto57

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Thanks again, Karl. Whenever you have a chance... if yours comes apart easily, at least we could see how the internal parts are shaped, and I'll know better how to get it apart.

All the best, Rich.
 

karlmansson

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Apr 20, 2013
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Thanks again, Karl. Whenever you have a chance... if yours comes apart easily, at least we could see how the internal parts are shaped, and I'll know better how to get it apart.

All the best, Rich.
Well, this explains why I didn’t recognize your situation...

There is a step inside of the main body of the cap on mine if you poke a rod through from the plunger side.

3F6DD050-67DA-4235-B491-6BD79F10491C.jpeg 401D4637-4E7F-482B-908B-278186B4F427.jpeg 613D1732-8D19-4320-A000-A390A19D65DA.jpeg
 

proto57

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Maybe it would be easier to get the seal off if you unscrew the hook and pull the plunger out?
Thanks, Karl... actually I did have the hook and plunger out when trying to get mine apart. I only had them back in for the above picture.

Well it just figures, then... our units are differently designed! I'm going to take a wild guess that your's is the improved version. In your design, when unthreading, the threads are also effectively lifting the compression ring out. But in mine, after you take out the securing screws, the compression ring is still tight in the hole.

OK then... much appreciated, but it is back to the drawing board. Over the next couple of days I'll take some time and go at it again. My next move will be to use my larger watch back opener, and put the three largest prongs into the screw holes on the compression cap, and see if twisting it will break it loose. I'll post if there is any progress... and I'll post what the inside of mine looks like, if it works, so others can see this thread as a reference.

Later, Rich.
 

karlmansson

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Apr 20, 2013
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Thanks, Karl... actually I did have the hook and plunger out when trying to get mine apart. I only had them back in for the above picture.

Well it just figures, then... our units are differently designed! I'm going to take a wild guess that your's is the improved version. In your design, when unthreading, the threads are also effectively lifting the compression ring out. But in mine, after you take out the securing screws, the compression ring is still tight in the hole.

OK then... much appreciated, but it is back to the drawing board. Over the next couple of days I'll take some time and go at it again. My next move will be to use my larger watch back opener, and put the three largest prongs into the screw holes on the compression cap, and see if twisting it will break it loose. I'll post if there is any progress... and I'll post what the inside of mine looks like, if it works, so others can see this thread as a reference.

Later, Rich.
Can you get a knife edge in under any potential edge of the block?
 

proto57

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"Can you get a knife edge..."

No, there is no gap at all. I didn't want to assume, so I checked again, carefully, at your suggestion. I can get to a small gap under the screw holes, but really nothing large enough to wedge it apart can fit in there. I tried tapping in one of those cheap mini screwdrivers, and only bent it.

I also tried my case back opener, to see if a twisting force applied, using the 3 screw holes, might help. But it didn't move.

The hole in the compression disk is exactly 3/16" of an inch. I know this because a 3/16" drill shaft is a snug fit. I may grind down one edge of the drill shaft, to make a small "lip". If I can come from the top, and get that lip under the bottom of the compression disk, perhaps I can tap it out. But no high hopes there. I'm thinking I may be able to pull it from the bottom side, by making a lipped tool, and rigging a small slide hammer of some kind.

Right now I have it chilling in the freezer... I always do this with stuck bearing races, when I can. The compression disk should shrink slightly. The hole will be ever so slightly larger, too, as the "ring" of the cap, when shrinking from cold, will have a lesser width, enlarging the hole. As I understand it. I'll post here with results, when I have any...
 

proto57

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... I thought of another thing I may try, but not today: I could machine a soft steel drift to fit from the top. I could drill, tap, then split the end first. Then after it is in the compression cap, insert a screw to enlarge it, thus wedging it into the compression cap hole. Hopefully it would be tight enough in there to allow the cap to be tapped out... not hopeful there, either, but I'm like a dog with a bone, now. I don't want to give it up...
 

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