Author Topic: A tiny 3 Cylinder Holt based engine  (Read 35641 times)

Offline cfellows

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Re: A tiny 3 Cylinder Holt based engine
« Reply #90 on: July 29, 2017, 05:03:59 PM »
Hi Chuck,
To carve out the inside of the lower crankcase probably took about 3 hours. As you know my technique is to make a step-off chart for the shape so it's pretty much a matter of following the numbers. I don't mean to make it sound that simple but as long as you follow the numbers it goes quite fast. I'm guessing the whole lower crankcase took between 10-12 hours. (Machining) Finishing with files and such took another couple of hours.
gbritnell

Yeah, I'm familiar with your technique of whittling stuff out from solid.  Kind of blows my mind to see the results you get.  I've never mastered the art of working like that, guess I'm too impatient.  And, I've only recently begun to appreciate the skill required for using a file.  However, I do appreciate the value of good file work.  I've also come to appreciate the value of being able to use a jeweler's saw.  Very effective, and relatively fast, for cutting out small, intricate parts.
So many projects, so little time...

Offline Brian Rupnow

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Re: A tiny 3 Cylinder Holt based engine
« Reply #91 on: July 30, 2017, 12:15:58 AM »
George--Once again, you have out-done yourself. I love your engine, and I am in awe of your machining skills.  I am taking a break from machining for a while, but I still check the forums every day to see what people are doing. Great job.--Brian

Offline Doc

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Re: A tiny 3 Cylinder Holt based engine
« Reply #92 on: July 30, 2017, 02:23:48 PM »
Just catching up on the thread VERY impressive. Those heads are so small and the rockers WOW! You are doing some amazing work George!
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Offline gbritnell

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Re: A tiny 3 Cylinder Holt based engine
« Reply #93 on: July 31, 2017, 10:37:29 PM »
Thanks Brian, Doc, Chuck, Bill and everyone watching and commenting.

The next project is the carburetor. Having experience with the 'Tiny' hit and miss engines I realized how small the venturi can be made and still have an engine run. With the 'Tiny' hit and miss engines there is the governor mechanism to regulate the speed but having no such mechanism on this engine it's necessary to make a throttling carburetor. I have no idea what it takes as far as venturi size for this engine so kind of basing on the 'Tiny' carb, this engine being a bit larger, I opted for a .093 venturi. This is an air bleed style carb with a rotating barrel for the air control. The inlet and outlet sides are .125 and they taper down to the .093 diameter. I had run out of my small sewing needle supply so I headed to the local fabric store to see what they had. I bought a package of 20 sharps, ranging in size from #3 to #9.
The smallest diameter, the #3 is .028. The next size up has a diameter of .031, just right for using drills of .032 and .032 (#67 and #68)
I machined the body on the end of a piece of aluminum rod. The first one I started I began on the lathe and drilled and reamed the venturi hole. Right after finishing the hole I realize that I would have to put the barrel hole through this hole and it probably wouldn't make for a smooth cut due to no support for the drill. The barrel is .144 diameter and I don't have a reamer that size but I do have a new drill.
I cut this first try off and restarted. This time I put the rod in the dividing head and started cutting the sides, top and bottom. Once I had these sides squared up I put the barrel hole through. I then machined the remaining shapes and drilled and tapped the holes for the barrel retaining screw and throttle stop.
From the dividing head I put the rod in the lathe and put the venturi hole in. To taper the inlet I made a 10 degree D bit.
The body was then stood up vertically in the mill vise to put the 2 mounting holes in. These will be for 1.20mm screws (.047diameter) While standing up I used a slitting saw to part it from the rod.
The thread for the needle valve is 2-64. I have a tap that small but no die. Even if I had a die I wouldn't have been able to get close to the shoulder so I chased it by hand on the lathe.
When I say by hand I set up for cutting the thread, tool, dials etc. and then I have a crank handle that fits into the outboard end of the spindle so I can crank it by hand. (no power). I started using this procedure way back when I built the radial engine and had to get the cylinder thread up against the barrel shoulder.
I made the adjusting barrel first and threaded it. I then hand chased the male thread until the barrel fit nice and smoothly.
The fuel chamber is made from 2 pieces. The inner piece or the piece that goes into the carb body is drilled .026 so the .032 needle can seal into it. The counterbore is .075 and this area allows the fuel to flow in and around the needle. To seal this chamber off and provide support for the needle an outer piece was made and drilled .032. The two pieces were pressed together and the assembly was pressed into the carb body.
To fix the needle into the barrel I first screw the barrel onto the threaded stem until it bottoms. I then back it out about 1 turn. I insert the needle until it seats into the jet hole and mark where to cut it off.
Using a small cutoff wheel in the Dremel I cut it to length then grind a small flat on one side where it fits into the barrel. This allow the solder to flow around the needle and into the flat to secure the needle.
The last piece was a handle. I cut this on the end of a bar of steel and then parted it off with a slitting saw. The edges of the handle were filed and sanded with a nice radius.
These pictures are of the initial machining on the end of the bar.
Talent unshared is talent wasted.

Offline gbritnell

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Re: A tiny 3 Cylinder Holt based engine
« Reply #94 on: July 31, 2017, 10:41:37 PM »
The next 3 pictures show the parts before assembly. In the pictures the needle looks huge but consider it's only .032 diameter.
The last picture show the jet which projects through the bottom of the barrel and goes to the center line of the venturi.
Talent unshared is talent wasted.

Offline gbritnell

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Re: A tiny 3 Cylinder Holt based engine
« Reply #95 on: July 31, 2017, 10:47:58 PM »
And there you have it, a tiny carburetor. The first picture taken through the venturi shows the jet projecting into the venturi and the tip of the needle sticking out of the jet. The next picture shows the barrel retaining screw and the throttle stop screws, both 1.0x.25 mm.
As an aside these tiny parts are made on my 6 inch Atlas lathe and my 8 x 36 vertical mill.
gbritnell
Talent unshared is talent wasted.

Offline 90LX_Notch

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Re: A tiny 3 Cylinder Holt based engine
« Reply #96 on: July 31, 2017, 11:12:03 PM »
"And there you have it....." 

Much easier said than done George.  You make it look so easy.  I am always in awe of your skills.  I am really enjoying this build.


-Bob

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My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Online Vixen

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Re: A tiny 3 Cylinder Holt based engine
« Reply #97 on: July 31, 2017, 11:46:38 PM »
Hi George

Is this watch making or engine making?  When they say it's engineering in miniature, they are not exaggerating.

Congratulations on this fine piece of work.

 :cheers:

Mike
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

Offline crueby

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Re: A tiny 3 Cylinder Holt based engine
« Reply #98 on: August 01, 2017, 12:54:07 AM »
Wow.

Again. As usual!

Offline Kim

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Re: A tiny 3 Cylinder Holt based engine
« Reply #99 on: August 01, 2017, 05:15:12 AM »
Wow! is right!
And what's even more amazing, is that it's going to work too!
That's amazing George!
Kim

Offline gbritnell

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Re: A tiny 3 Cylinder Holt based engine
« Reply #100 on: August 01, 2017, 12:30:54 PM »
Thanks Chris and Kim for checking in and commenting.
gbritnell
Talent unshared is talent wasted.

Online fumopuc

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Re: A tiny 3 Cylinder Holt based engine
« Reply #101 on: August 01, 2017, 12:42:17 PM »
Another masterpiece. Impressive. You have big coins there at the other side of the pond.
Kind Regards
Achim

Offline Roger B

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Re: A tiny 3 Cylinder Holt based engine
« Reply #102 on: August 01, 2017, 08:41:13 PM »
Still following with interest  :ThumbsUp:  :ThumbsUp:  :wine1: I do like the way you machined the distributor cap and the carb is magnificent  :praise2:  :praise2: 
Best regards

Roger

Offline gbritnell

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Re: A tiny 3 Cylinder Holt based engine
« Reply #103 on: August 29, 2017, 12:02:37 AM »
It's been awhile since I posted on the engine. I've had several other projects going at the same time.
I finished the spark plugs. The thread is 6-40 (.138 OD.) I've never made plugs this small before so I don't know how they'll function. I know they should work as Lou Chenot made smaller plugs for his Deusenberg engine and they worked.
 
Talent unshared is talent wasted.

Offline gbritnell

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Re: A tiny 3 Cylinder Holt based engine
« Reply #104 on: August 29, 2017, 12:11:06 AM »
I made the fuel tank and mounting brackets. The tank is .625 O.D. x 1.00 long. The fuel line is 1/16th.
I made up all the fittings for the water manifolds then assembled them on the engine. The intent was to soft solder all the pieces together in place but I didn't know if the electric soldering gun would put out enough heat to do a good sweat job due to the fact that all the other pieces and the aluminum water jackets would be drawing heat away. I fluxed each joint then touched the gun to a piece of 50/50 solder and first applied a dab of solder to the joint itself then held the gun on each fitting. I was pleasantly surprised when the solder wicked all the way around each fitting. A little cleanup with a fine file got rid of the excess solder.
gbritnell
Talent unshared is talent wasted.

 

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