Author Topic: Stuart twin oscillator problems  (Read 750 times)

Offline AOG

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Stuart twin oscillator problems
« on: March 29, 2018, 03:35:48 PM »
I need some help getting my Stuart twin oscillator running. I am having issues with the rotary valve. To be blunt itís leaking like a sieve. I have used my standard procedures for preparing oscillator cylinders on the valve. Iíve gone up to 800 grit sandpaper on the valve and standard useing my old surface plate to keep them flat but I just canít get a good seal. Any suggestions?

Thanks

Tony

Offline Jo

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Re: Stuart twin oscillator problems
« Reply #1 on: March 29, 2018, 03:37:09 PM »
Have you tried some heavy oil on the two surfaces?

Is something not square? i.e. is it leaking only on one side?

Jo
Usus est optimum magister

Offline Gas_mantle

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Re: Stuart twin oscillator problems
« Reply #2 on: March 29, 2018, 03:51:55 PM »
Hi Tony, sorry to hear you can't get it running  :(

Can you take a pic of the parts at the affected area so we can see how it goes together etc.

Offline AOG

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Re: Stuart twin oscillator problems
« Reply #3 on: March 29, 2018, 04:00:41 PM »
Hi Tony, sorry to hear you can't get it running  :(

Can you take a pic of the parts at the affected area so we can see how it goes together etc.

Iíll try to get some pictures after work.

Tony

Offline bent

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Re: Stuart twin oscillator problems
« Reply #4 on: March 29, 2018, 05:34:20 PM »
Do you suspect the casting may be porous?  You can seal the surfaces with a coating of cyanoacrylate (super glue) then sand it smooth, this sometimes works for us (I'm the engineer for a valve mfg. company). 

Offline Jasonb

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Re: Stuart twin oscillator problems
« Reply #5 on: March 29, 2018, 06:55:46 PM »
Is the hole for the valves pivot tapped square to the face and what strength spring are you using, it can be quite a bit tighter than the cylinders as you only want it to move when the lever is pulled/pushed

Offline AOG

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Re: Stuart twin oscillator problems
« Reply #6 on: March 29, 2018, 11:26:26 PM »
Jason called it. The pivot isnít tapped square to the standard. As a result the valve is slightly cocked. I straightened as best I could and now itís running on about 40 psi. Unfortunately the valve is still leaking pretty badly. Any suggestions short of plugging and retapping the standard?



Tony

Offline 10KPete

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Re: Stuart twin oscillator problems
« Reply #7 on: March 30, 2018, 12:42:52 AM »
When I built my single I hit the same problem. Even if the hole in the cylinder is perfectly straight the thread pulls the shaft off square when the thread bottoms, at either end.

I put a piece of 360 Wet or Dry between the standard and the cylinder (a little hole for the shaft, and I had finish milled the standard and drilled the hole in the same set-up) and turning the cylinder by hand seated the cylinder. Some 660 paper finished it up.

Chuck up the cylinder by holding the shaft and turn the lathe by hand. You'll know soon how square the shaft is!

Hope this helps,

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline Jasonb

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Re: Stuart twin oscillator problems
« Reply #8 on: March 30, 2018, 07:23:58 AM »
It would not matter if the valve was a bit loose on the pivot pin so you could just open up the hole a little.