Author Topic: Stainless Oscillating Pistons?  (Read 22735 times)

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #50 on: April 21, 2009, 08:03:21 AM »
Did the PTFE piston expand with steam or were you talking about the brass one?

So you pinned the piston then, that's good info to know  :thumbup:

Darren,

This plastic piston lark isn`t quite straightforward........  ::)

The engine ran perfectly at room temp, on air.

Steam heat expanded the piston, locking it solid, as far as the engine was concerned.  :scratch:

Piston into lathe, take off "half a thou" per side. Back onto engine....... Several times!

The lathe chuck is "true"....... But not that good, so the piston is not truly round now.

Tried a little `speriment this morning. Dunked a couple of cylinders & machined ptfe into a mug of boiling water.
Got it to slide in one cyl. But not in the other (which has a thinner cyl wall).

Measured o/d when cooled....... It`s only .001" or so below std (.3125")!!!  :bugeye:

I get different readings from mic & vernier. Also depends weather the sun`s shining or not.......  :bang:

I think I`ll have to steam individual piston/ cyl sets before mounting to the 3cyl engine......  :scratch:


The piston s are tapped 1/8 Whit & screwed onto the rod, with a spot of loctite.



David D

David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline sbwhart

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Re: Stainless Oscillating Pistons?
« Reply #51 on: April 21, 2009, 08:13:19 AM »
David

One Little trick we use to do with nylon parts was to boil them, just like an egg, many plastics take up moisture and grow, I know that with nylon it can take up to about 1% of its own weight, don't know what it is for PTFE but you could try it before you machine to size.

Cheers

Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #52 on: April 21, 2009, 12:18:17 PM »
David

One Little trick we use to do with nylon parts was to boil them, just like an egg, many plastics take up moisture and grow, I know that with nylon it can take up to about 1% of its own weight, don't know what it is for PTFE but you could try it before you machine to size.

Cheers

Stew

Sounds good to me Stew!  :clap:

I`ll try anything.......  :thumbup:

The used plastic piston measures around .309".
The boiling water plug measures around .312".

I guess steam is hotter than boiled water...... And it shows in the differing diameters!

David D

David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Darren

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Re: Stainless Oscillating Pistons?
« Reply #53 on: April 21, 2009, 12:22:32 PM »
I did mention plastics absorb water, I didn't think it was that much though !
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

bogstandard

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Re: Stainless Oscillating Pistons?
« Reply #54 on: April 21, 2009, 12:50:41 PM »
So now you lads understand when I go on about the correct materials for making cylinders and pistons out of.

That is why I always ask if it is going to be run on just air or steam. It makes a very big difference.

Darren,

If you are going to make the twin engine for running on steam, I would stay with the recommended metals. David's engine is a lot different in design, and yours will have a lot more heat, friction and stresses involved. You could modify my design to use PTFE piston rings, but I don't think there would be any advantage over the standard o-rings.

John

Offline Darren

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Re: Stainless Oscillating Pistons?
« Reply #55 on: April 21, 2009, 06:23:03 PM »
Thanks for the tip John, I will go with metal then  :thumbup:

I don't intend to run it on steam, but someone might when I'm gone  :ddb:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

bogstandard

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Re: Stainless Oscillating Pistons?
« Reply #56 on: April 21, 2009, 08:14:00 PM »
Darren,

When you are gone, the least you will be worrying about is whether someone is going to be running your little engine on steam. Make it for yourself, no-one else. Unless of course you are thinking of taking it with you.

I was thinking about taking my mill and lathe with me, can you just imagine the Co-op pall bearers trying to move those, with my weight as well. :lol:

Mind you, I suppose I could get a few jobs doing furnace repairs, or maybe even a new set of gate hinges.


Bogs

Offline Bernd

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Re: Stainless Oscillating Pistons?
« Reply #57 on: April 21, 2009, 09:57:21 PM »
 :ddb:  :ddb: If I were going that way and taking my machines along I would make a coal stoker. To labor intensive shoveling all that coal.  :ddb:  :ddb:

 :lol:  :lol:  :lol:

Bernd

P.S.  :offtopic:
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Offline cedge

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Re: Stainless Oscillating Pistons?
« Reply #58 on: April 21, 2009, 10:05:09 PM »
Bernd
I doubt John would require a stroker, where he's likely to wind up.... but topping off the
a bit of a tough job...(grin)

Steve

Offline Bernd

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Re: Stainless Oscillating Pistons?
« Reply #59 on: April 22, 2009, 08:40:03 AM »
Ah Steve one of us spelled "stoker" wrong.  :lol: :lol:

I had to go back and check my spelling. :lol: :lol: :lol:
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Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #60 on: April 24, 2009, 02:24:35 AM »
I machined a piston to a sliding fit in one of the triple`s cylinders, then took off .001" per side.....

Assembled the assembly to the single cyl engine & steamed it to prove it worked ok.

After proving, each set was then assembled to the triple......  :thumbup:

Well, it all went perfectly........  :)

I lit the burner. After a few mins it just started, on it`s own! 

I throttled back to tickover & grabbed the camera.........



After a few minutes running it would tick over very sweetly......




After some time, it  STOPPED!!

The solder had melted on the regulator!  :shock:




I think the burner is a little too enthusiastic for tickover mode!

Now re soldered, with a heat shield fitted........



Will try out a smaller "tickover" burner, at Lincoln.

It`s all an experiment..........  :D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline sbwhart

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Re: Stainless Oscillating Pistons?
« Reply #61 on: April 24, 2009, 02:50:55 AM »
That was excellent David:-

Great Job,

Great Video,

Great Tomato Plants
 
:clap:  :clap:  :clap:  :clap:

Unfortunately I'll miss it at Lincoln we hit the plastic hard last week in Edinburgh and the bills just landed 

                                                                                                                                                  :jaw:


So enjoy the rabbit pie at Browns

and I'll look forward to meeting you at Arrogate


Stew



A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #62 on: April 24, 2009, 03:24:14 AM »
Thanks for that Stew.

This engine just keeps on developing.......  :wave:


A pity we`ll not meet at Lincoln, it should be a great get together.

Some of the "all weekend" members have set off, already!

Hope to see you at Harrogate.  :thumbup:

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

bogstandard

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Re: Stainless Oscillating Pistons?
« Reply #63 on: April 24, 2009, 03:43:26 AM »
Very nice indeed David, it ticks over like a swiss watch.

You've just got to wait now to see how the pistons stand up to real extended running. I shouldn't think you will have any trouble.

John

Offline Darren

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Re: Stainless Oscillating Pistons?
« Reply #64 on: April 24, 2009, 04:29:45 AM »
You're not wrong there David...

That is sweet, those pistons will last a lifetime or two I guess.... :clap:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline Bernd

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Re: Stainless Oscillating Pistons?
« Reply #65 on: April 24, 2009, 08:42:03 AM »
Sweet running and sounding engine at tick over there David.  :thumbup:

Full throttle sounds like a race car. I wouldn't have thought it would run that fast. Pretty vibration free too from what I saw.

Bernd
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Offline SPiN Racing

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Re: Stainless Oscillating Pistons?
« Reply #66 on: May 06, 2009, 10:20:20 PM »
Wow very very cool engine.
The sound ot the three humming away is really a nice tone at full song.  :headbang:
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