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Old 01-17-2017, 07:13 PM   #71
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Thanks John !
Yep it will go in a boat when it's all done, but the boat doesn't exist yet. Not really sure what it will look like but it will be as small as I can make it and still be stable and pond worthy.

I will have the boat build and maiden voyage in this thread too.

Pete


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Old 01-17-2017, 10:14 PM   #72
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Is it going to be prop driven or a paddler? Or is that another thing that is as of yet undecided.

don


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Old 01-19-2017, 12:54 AM   #73
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This one is going to be pushed around with a prop, not sure of size or pitch though. The plans say a 30mm diameter but I'll see what I can learn about those when I get to that bridge.
Pete
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Old 01-19-2017, 01:02 AM   #74
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The disk that ports the steam is next. It wasn't to bad to make, it's just tedious setting up the rotary table and doing that means the vise gets dismounted which will require time to get it back to square when this operation is done. The critical surface is the face and right now I don't have a way to tell if it's good enough. Guess I'll find out later and tweak it then if it doesn't seal well.

Pete

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Old 01-19-2017, 01:07 AM   #75
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The disk is pressed against the ports with a spring that is covered with a cup shaped piece of brass. This is going to have to be tested later to see if there is enough spring tension to make it seal. I'm sure it could be calculated, but I'm not your guy for that much math !
Pete

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Old 01-19-2017, 04:04 AM   #76
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Pete,

After making many dozens of this type of control valve, maybe I could give you a couple of pointers that 'might' give you a leak free valve.

If possible, lap the two faces together so that you get a nice flat looking face. You will see after you start where all the high spots are, and you keep going until you have a complete dull surface on both parts. Don't try to use power tools, your fingers are more sensitive when the correct surface finish is reached.

The spring loaded part is one area that is affected by vibration and your inputted rotation, so I would suggest you make the centre spindle a little longer so that you can use a locking nut on top of the nut that is on there, or make two very thin nuts so that they can be fitted into the space you have. I always tried to finish it off by using an acorn nut to do the locking, it looks much neater than just two nuts and are very easy to make.

This shows the locknut required



And these are the acorn nuts, you make them to whatever length is required.



Just suggestions

John
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Old 01-19-2017, 07:23 PM   #77
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John, I would like to know the details of how you do the lapping process. What do I need to do it properly ?
As far as the nuts go it would be good to make something a bit fancier wouldn't it.
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Old 01-19-2017, 07:40 PM   #78
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Pete,
Because it is ali and brass you do have to take it steady.

I would start off with a tiny bit of valve grinding paste, but the very fine one. I would use that until you very nearly get to a full lapped coverage on both parts.
Once that is done, wash everything to as clean as possible, you don't want that grit working it's way onto the faces again. Then you could use a tiny blob of brass polish and carry on lapping, eventually, it should be perfect, but if you want to be even better, use a bit of toothpaste for final lapping. Once it gets to that stage, after you have cleaned the faces off, put a drop of oil on there and you should be able to pick the engine up by suction alone.

The lapping technique is to get the top part (brass) between your fingers, and like spinning a top, with slight downwards pressure rock the brass part backwards and fwds about 90 degrees, after a minute or so, rotate the top by 90 and then repeat the 90deg fwds/bk. Keep doing this for about 2 full revolutions and then see what the faces on the parts look like. Continue until, as I said, nearly having a matte surface all over, then go to your finer stuff.

John


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