Author Topic: Stainless Oscillating Pistons?  (Read 22731 times)

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #25 on: April 07, 2009, 01:06:44 PM »
I`ll not tell anyone Stew...... :thumbup:

I`m not a hobby shooter either, anymore......  ::)

David.

David.

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

Offline Darren

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Re: Stainless Oscillating Pistons?
« Reply #26 on: April 07, 2009, 02:35:37 PM »
I'm not either, since Blair that is.... :(
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline sbwhart

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Re: Stainless Oscillating Pistons?
« Reply #27 on: April 07, 2009, 02:42:57 PM »
Dave

25th April is Members open day at Chester Zoo (we have a season tickets)

Spoilt for choise  :scratch:

Monkeys or Steamers.  :scratch:

Rabbit Pie or Ham sandwich.  :scratch:

The boss likes the Idea of the Rabbit Pie

I think it will be Lincoln I'll let you know for certain closer to.

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 #28 on: April 08, 2009, 08:05:14 AM »
Stew,

Well, that`s done it!  ::)

I`ve mentioned rabbit pie on the Mamod forum.  :wave:

Several of em are salivating furiously, and a Scottish member intends to take some back over the border with him!  :D

Where do we find this famous Brown`s rabbit pie shop?  :thumbup:

David D
« Last Edit: April 08, 2009, 08:08:09 AM by Stilldrillin »
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 #29 on: April 08, 2009, 08:18:59 AM »
Its near the Castle Prison and just across from the White Hart Hotel, at the top of Steep Hill:- Your not to far away at the musium of Lincolnshire life.

For pudding they do a mind blowing Bread and Butter pudding steaped in whiskey or Treackle Tart with a scoop of home made vanila ice cream MMMMMMMMMMMMMMMMMMMMMMM were going.

On occation as a special they do deep fried battered Marse Bars your Scotisch buddies won't want to go home

Steep Hill is the name of the street and it is Steep:- they supply oxygen part way up along with a cardiac arrest team.  :lol:

Stew
« Last Edit: April 08, 2009, 08:30:09 AM by sbwhart »
A little bit of clearance never got in the road
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Location:- Crewe Cheshire

Offline sbwhart

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Re: Stainless Oscillating Pistons?
« Reply #30 on: April 08, 2009, 01:51:54 PM »
Ok the address is

Browns Pie Shop, 33 Steep Hill, Lincoln, LN2 1LU  Tel 01522 527330

If your planning on going Saturday night it would be advicable to book.

Enjoy

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 #31 on: April 09, 2009, 02:16:25 AM »
Thank you for your info Stew.  :wave:

All passed on & posted.....

Much appreciated.  :thumbup:

David D
David.

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Offline sbwhart

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Re: Stainless Oscillating Pistons?
« Reply #32 on: April 09, 2009, 03:09:48 AM »
David

I'm more or less 100 % shure we will be going as well my bosess is keen on the idea.
I'll get in touch closer to the date

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 #33 on: April 09, 2009, 03:29:49 AM »
David

I'm more or less 100 % shure we will be going as well my bosess is keen on the idea.
I'll get in touch closer to the date

Stew

Nice one Stew!  :clap:

I`m really looking forward to a very good day, now......   :thumbup:

Cheers,
David.
David.

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

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #34 on: April 12, 2009, 03:48:02 AM »
David,

Before you start, contact me or ask on here, and I can give you a few pointers on machining PTFE, and how to get them to run in your engine.

John


Well John, I`m about ready to start these plastic pistons.  :wave:

My thoughts are to machine the rod & big end from 1 length of 1/4" brass rod.

Then, thread the piston end 1/8 or 3mm to screw the piston onto.

Of course, it will need locking onto the thread........  :scratch:

Have you any tips for me please?

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 #35 on: April 12, 2009, 04:12:54 AM »
I knurled a bit of stainless to grip PTFE, sure held on tight, but whether it would be tight enough for an engine I don't know  :scratch:
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 #36 on: April 12, 2009, 04:34:12 AM »
David,

Have the pistons oversize to begin with.

Drill and tap the piston and screw in the rod until it is really tight, you could put a bit of loctite on it to help grip.

Remount the piston rod in the chuck, and using razor sharp HSS tooling, preferably with a nose radius, take the piston down to size in one cut. It might take a bit of playing about to get to the right size, use a bit of ali or brass first to get the cutter into the right position and then lock up your cross slide gib. If you try to take fine cuts on PTFE it will 'string' badly. Plus a lot of airbourne dust will be produced, which isn't good for you in large quantities.

So to step thru it.

Cut pistons to length, but oversized on diameter (you can wack off 1/2" in one cut). The larger the cut the better, less dust.

Drill and tap pistons and fit rods.

Using a bit of ali or brass, bring the cutter to give you size, and lock cutter in position when size is reached. Retry for size just in case cutter has moved during lock up. It shouldn't be a tight fit in the bore, just a nice sliding fit. You can't lap in a PTFE piston.

Mount up pistons using rod in the chuck.

Take one smooth cut to bring piston down to size.

Check for fit in bore.

Hope it works for you, and if you have any questions or complaints, I am on holiday for the next few months.

Bogs

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #37 on: April 12, 2009, 06:42:20 AM »
Darren, Bogs,

Some great ideas/ info there. Thanks very much!  :thumbup:

Will Loctite stick ok to PTFE?

I have no worries over the working temperature of Loctite, as my 3 exhaust pipes haven`t fallen off yet!

I`m more than a little pleased about that part of the experiment......  :clap:


Questions? Complaints! Whooo?....... ME!!!!???? Nah!

Ah`m no trubble to nubdy...... No need for a holiday neither.....  :thumbup:

Many thanks,
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 #38 on: April 12, 2009, 07:05:19 AM »
David there are special glues that will stick to PTFE, but most normal off the shelf type won't very well if at all.
I've no idea about locktite though.
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #39 on: April 12, 2009, 08:48:10 AM »
David there are special glues that will stick to PTFE, but most normal off the shelf type won't very well if at all.
I've no idea about locktite though.

Darren,

I like your idea of knurling the conrod.  :thumbup:

I`ll have a little experiment with loctite, this afternoon.......  :wave:

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 #40 on: April 12, 2009, 12:04:01 PM »
David,

You have to look at the material you are using.

If you drill it, and force something into the hole, it deforms the material.

After time, the stresses in the joint will try to keep expanding the material. With something like ali or brass, that stress stays in the material and so doesn't allow the part to expand.

The reason for drilling and tapping is to prevent that internal stress build up, so you get no further expansion of the material.

You should find loctite will be plenty strong enough to hold the threaded joint.

John

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #41 on: April 13, 2009, 07:52:54 AM »
John,

You`re right, of course.  :thumbup:

Darren`s way was chosen cos` I have knurling ability, but no decent tap/ die combination.  ::)

Order for 1/8 whit. despatched to Arc this morning......... :wave:


The loctite experiment went ok......

The double drilled hole was a couple of thou undersize, probably soft material springing back.

I made the rod a sliding fit, & assembled with a spot of loctite.
After 6hrs it was a struggle to pull the rod out. 24hrs curing should be ok.  :thumbup:

All proceeding nicely.  :clap:

David D
David.

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

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

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #42 on: April 21, 2009, 02:29:46 AM »
Yesterday saw the first run of a PTFE piston.

I have a Mamod SE2 single cylinder engine, ideal as a test bed.



It ran perfectly on air.  :thumbup:

STEAM was another story, the piston expanding to grip the brass cylinder......  ::)

After 3 trips to the lathe it finished up some 2thou or so undersize, very baggy when cold, but the engine ran very well!  :clap:



After running, everything was clean! No orrible steam cream to clean up!  :clap:



Very pleased.

Now to finish machining a set for the Triple......  :wave:



David D
« Last Edit: April 21, 2009, 03:28:04 AM by Stilldrillin »
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 #43 on: April 21, 2009, 03:44:53 AM »
Now you know what your running clearance should be David, you should have no further troubles.

You're now cookin' on gas, and the only wear you should get is on the pistons themselves. Don't forget to put a spot of lube on your pivot points.

Now you know the exact size, you can make a few spares, then when the time comes, shave the old one off with a stanley knife and stick a new one on.

John

Offline Stilldrillin

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Re: Stainless Oscillating Pistons?
« Reply #44 on: April 21, 2009, 03:51:00 AM »
Now you know what your running clearance should be David, you should have no further troubles.

You're now cookin' on gas, and the only wear you should get is on the pistons themselves. Don't forget to put a spot of lube on your pivot points.

Now you know the exact size, you can make a few spares, then when the time comes, shave the old one off with a stanley knife and stick a new one on.

John

My thoughts exactly, John!  :wave:

Thank you for your guidance......  :thumbup:

David.
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 #45 on: April 21, 2009, 05:33:30 AM »
Well done David,  :clap:

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:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline sbwhart

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Re: Stainless Oscillating Pistons?
« Reply #46 on: April 21, 2009, 05:49:05 AM »
Darren are you going to use PTFE pistons on your bogstandard engine ?

Stew
A little bit of clearance never got in the road
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Location:- Crewe Cheshire

Offline Darren

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Re: Stainless Oscillating Pistons?
« Reply #47 on: April 21, 2009, 06:08:51 AM »
I wasn't planning to, but I could....

Oh go on, make my life more complicated than it already is..... :bang:

Now I have a decision to make.... :scratch:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline sbwhart

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Re: Stainless Oscillating Pistons?
« Reply #48 on: April 21, 2009, 06:29:46 AM »
Go on then  :poke:

I'm trying to use you as a Ginney Pig for when I have a go at one of them Engines later in the year.  :D

Stew
A little bit of clearance never got in the road
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Location:- Crewe Cheshire

Offline Darren

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Re: Stainless Oscillating Pistons?
« Reply #49 on: April 21, 2009, 06:32:25 AM »
I see,

There are names for people like you  :lol: :lol: :lol:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)