Author Topic: Tiny pipe fittings for a Tiny engine  (Read 1697 times)

Offline gbritnell

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Tiny pipe fittings for a Tiny engine
« on: April 07, 2018, 04:35:36 PM »
  In the course of building miniature engines a lot of us have needed small pipe fittings for air lines or coolant lines. If the needed fittings are of standard (Imperial) dimensions then PM Research has fittings, both rough cast and finished that will do the job. The finished pipe fittings are for MTP threads.

 On many occasions I have needed fittings other than standard sizes or where the available fittings just look a little too out of scale so I make my own. These can be any configuration, tee's, el's, crosses etc.

 For my current project, the Tiny side shaft hit and miss engine I needed fittings that would replicate the plumbing used for the intake tract and given their size I made my own.
Generally all fittings are connected to a piece of pipe/tubing so where I can I turn one half of the fitting with the piece of tubing as one part. I drill the passageway first, in this case .093 diameter. I calculate the drill depth so that the tip of the drill stops at the inside wall of the fitting, using the 118 degree point on the drill to form the inner radius of the fitting. I then turn the tube diameter, the flange and the fitting outer wall diameter. Tube .125, flange .156 and fitting. 140. The piece is then parted off to the necessary length.
Using a small chuck mounted in the mill at 45 degrees I trim the fitting until the cutter just skims the outer edge of the material. If it's a few thousands off it won't hurt anything.
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Offline gbritnell

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Re: Tiny pipe fittings for a Tiny engine
« Reply #1 on: April 07, 2018, 04:45:23 PM »
 Years ago when I started making my own fittings I realized that just laying the parts on a fire brick to silver solder would give varying results so I made up this fixture. It's just a steel plate onto which I have two small V-blocks mounted. I have several holes in the plate so I can move the V-blocks to adjust for larger fittings.
Even if you just make the fitting without the combined tubing, usually for larger sized fittings, the process is the same. I turn a short stub onto the end of a piece of steel that fits snugly in the fitting or tube.
The fitting is then mounted in the fixture V-block and moved close to center. The other half is mounted and then both pieces are adjusted so they are centered up. I generally eyeball a small gap between the fittings but a piece of shim stock can be used. This gives just enough gap for the silver solder to flow into the joint.
Talent unshared is talent wasted.

Offline crueby

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Re: Tiny pipe fittings for a Tiny engine
« Reply #2 on: April 07, 2018, 04:47:00 PM »
Oh, I like that fixture! Gotta remember that one!

Offline Roger B

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Re: Tiny pipe fittings for a Tiny engine
« Reply #3 on: April 07, 2018, 04:50:45 PM »
That's a neat idea  :ThumbsUp:  :ThumbsUp: I need to make couple of custom elbows/flanges for my twin cylinder engine.
Best regards

Roger

Offline gbritnell

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Re: Tiny pipe fittings for a Tiny engine
« Reply #4 on: April 07, 2018, 04:57:32 PM »
 The pieces are fluxed and a small cutoff of silver solder is laid into the flux at the joint line. For these fittings I would guess that the piece of silver solder is no more than .025 wide (.062 dia. solder)
The parts are slowly brought up to temperature to where the flux starts to get clear. I use a piece of steel rod to make sure the piece of solder doesn't roll off the fitting. When the flux starts to boil the piece of solder generally has a tendency to move. I slowly bring the temperature up until I see the solder turn silvery and flow around the joint. I try to hold the torch (propane) near the bottom of the fitting as the solder runs toward the heat. After soldering the parts are boiled to remove the flux. Hopefully not too much solder was used otherwise it flows into the inside corner and the detail of the flange is lost. On larger fittings this isn't a problem but with these tiny ones it doesn't take much solder to overwhelm the joint.
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Offline gbritnell

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Re: Tiny pipe fittings for a Tiny engine
« Reply #5 on: April 07, 2018, 05:05:23 PM »
 Using the steel rods that the parts were mounted on for soldering as a handle the radius is filed on the outer shoulder of the fittings. Everything is cleaned up, filed and sanded smooth. I then take the drill that was used for the I.D. and mount it in a chuck. Turning it by hand I take it down the tubing into the fitting and this cleans out the inside corner of any flux or mismatch between  the two parts.
The one piece of tubing has a coupling joint turned on it. I used it for these fitting because they were so small that using my assembly process would have been tough. This joint will be soft soldered together.
« Last Edit: April 08, 2018, 12:31:20 PM by gbritnell »
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Offline gbritnell

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Re: Tiny pipe fittings for a Tiny engine
« Reply #6 on: April 07, 2018, 05:09:11 PM »
 This is how the assembly will look on the engine. The end that goes into the head will have a screw (2-56) turned down to the minor diameter leaving a small stub on the end. The tubing will have a hole drilled in it to match the stub. This will hold the piping in place.
The carburetor will be s light press fit into the end of the lower pipe.
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Offline crueby

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Re: Tiny pipe fittings for a Tiny engine
« Reply #7 on: April 07, 2018, 05:09:51 PM »
Wonderful!
 :praise2:

Your shop elves need T-shirts with 'Britnell's Nano-Plumbing' on the back.

Offline gbritnell

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Re: Tiny pipe fittings for a Tiny engine
« Reply #8 on: April 07, 2018, 05:12:56 PM »
 As an additional note to this process when mounting the V-blocks to the base plate use a square against the two faces of the V-blocks to insure that they are square. If anything other than 90 degrees is used then I just make up a small triangle to set the blocks at the required angle, like for a quarter or eighth bend.
gbritnell
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Offline b.lindsey

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Re: Tiny pipe fittings for a Tiny engine
« Reply #9 on: April 07, 2018, 05:27:59 PM »
Very instructional as always George, and a great looking result too!!  Did you make the vee blocks? Just curious as to their size.

Bill

Offline cwelkie

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Re: Tiny pipe fittings for a Tiny engine
« Reply #10 on: April 07, 2018, 05:45:00 PM »
Very instructional as always George, and a great looking result too!!  Did you make the vee blocks? Just curious as to their size.

Bill

Bill - Those are 00-80 machine screws for clamps ... :mischief:

Joking aside - beautiful work as usual George.
Charlie

Offline gbritnell

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Re: Tiny pipe fittings for a Tiny engine
« Reply #11 on: April 07, 2018, 05:46:08 PM »
Hi Bill,
The V-blocks are just made from mild steel. Size wise, the rods sitting in them for the fittings are .250 diameter. The biggest rods I can get in them is about .438 which would make some pretty good sized fittings.
gbritnell
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Offline b.lindsey

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Re: Tiny pipe fittings for a Tiny engine
« Reply #12 on: April 07, 2018, 05:50:22 PM »
Thanks George, its plain to see how useful such a fixture is for these small fittings.

Bill

Offline Kim

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Re: Tiny pipe fittings for a Tiny engine
« Reply #13 on: April 07, 2018, 05:55:36 PM »
Thanks for taking the time to share this, George!
Another excellent technique I'll have to try out sometime.
Thanks,
Kim