Author Topic: AOG's version of Elmer's number 7 Square  (Read 2930 times)

Offline AOG

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AOG's version of Elmer's number 7 Square
« on: December 16, 2015, 02:28:04 AM »
It's time to start a new project. It will be Elmer's number 7 the square.



I decided to do this one because there is a bunch of soldering required and I really need the practice. Let's get started. I like to start from the bottom so I squared up a piece of aluminum for the base.



Then I coordinate drilled the holes.



Then I milled the base flat.



 The next piece is the frame assembly. I started by squaring up the frame blank.



Then the blank was milled flat.



Next the frame was marked out.



Then it's back to the mill to drill the holes.



I set up my die filer with a blade and cut out the waste stock.



Next the cuts were cleaned up on the mill.



I set up and drilled the air hole.



Then I drilled and tapped the holes for the base.



I put that piece aside for a while to start on the hollow square stock that would become the "cylinder". I faced it to length and put it aside.



For the end plate I deviated from Elmer's design. He just has you cut a piece of 1/16 stock and solder it into the end of the cylinder. I wanted something more fancy so I started with some square stock in the self centering four jaw and rounded of the corners.



Then I used the ball turner to round over the end.



I parted the piece off and I was left with this.



That's when I realized I had screwed up. I forgot to mill away the edges to allow the cap to Slide down into the cylinder. To make matters worse with the end rounded over how was I going to hold the part? I ended up using an adjustable parallel to set the height and a spirit level to get it level. It was very much a case of light cuts required.



I worked out ok.



I used some scrap pieces of aluminum to prop up the assembly and silver soldered the end cap on. This was my first use of the easyflo flux and silverflo solder. I have to say that worked much better the the Harris stuff I was using before. That leaves us here.



Next came the part I was dreading. Soldering the tube onto the frame. Per Elmer's instructions I used soft solder to mount the tube. To be honest it was a complete nonevent and I ended up with this.



The following  thing I did on the assembly was to drill the hole from the air passage.Then I counterbored the hole for a plug.


 
Next a plug was turned up to fit, parted off and Locktited in.



Till next time.

Tony

Offline b.lindsey

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Re: AOG's version of Elmer's number 7 Square
« Reply #1 on: December 16, 2015, 02:57:54 AM »
Wow, another one already half done Tony!  Ain't no grass growing under your feet :)  Looking good so far too.

Bill

Offline AOG

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Re: AOG's version of Elmer's number 7 Square
« Reply #2 on: December 22, 2015, 06:50:36 AM »
This edition starts with the bearing. The profile was turned.



Then the bore was drilled and reamed.



The part was taken over to the mill where the intake port was drilled.



Then the inlet tube was soldered in.



The next assembly was the crankshaft. I started by turning the the crank disk.



The center hole was drilled and reamed.



Over to the mill where the crank pin hole was was drilled.



Then the crank shape was milled out.



Then the piece is parted off and the crank pin hole was tapped.



Next I turned the crank shaft profile.



Next I drilled the exhaust.



Then it was into the collet block andover to the mill where the exhaust flat was milled.



Then the hole connecting the flat to the exhaust was drilled.



Then I flipped the the shaft over and milled the intake flat. The shaft was then pressed into the crank.



Then the piece was trued up in the lathe.



The next part was the flywheel. I faced blank on both sides.



I drilled and reamed the center hole.



Then the decorative rebate was turned into both sides.



Then I drilled and tapped the set screw hole.



Then I put the flywheel on a mandrel and trued up the flywheel.



Next I started on the piston assembly.  I turned a piece of tubing to a slip fit into the frame assembly.



Then the piston was parted off and filed to fit the tubing.



Then I drilled for the connecting rod.



Next I turned the connecting rod profile.



Next I drilled for the crank pin.



That's where I ran into trouble. When I test fitted the connecting rod to the piston it was to short. I forgot to add extra length for the dead center. I ended up remaking the connecting rod. Then I tried to solder the piston to the connecting rod. I melted the piston while I was heating up the connecting rod. I had to remake both parts. The end result was this.



The last piece I made was the crank pin. I turned some hex stock to the correct profile.



Then I threaded the end.



I'll end this with a family shot.



All I have left is the polishing, blueing and assembly.

Tony

« Last Edit: December 22, 2015, 03:19:43 PM by AOG »

Offline propforward

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Re: AOG's version of Elmer's number 7 Square
« Reply #3 on: December 22, 2015, 01:40:22 PM »
This is great - what an excellent set of step by step pictures. Much appreciated!  :ThumbsUp:
Stuart

Offline b.lindsey

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Re: AOG's version of Elmer's number 7 Square
« Reply #4 on: December 22, 2015, 05:56:39 PM »
Won't be long now at all Tony!  Looking forward to it!  Not even sure I have seen one of these run before.

Bill

Offline Don1966

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Re: AOG's version of Elmer's number 7 Square
« Reply #5 on: December 22, 2015, 06:48:06 PM »
Dam Tony, you haven't wiped the dust off your shoes yet nod already almost finished with another. Nice work bud............. :ThumbsUp:

Don

Offline AOG

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Re: AOG's version of Elmer's number 7 Square
« Reply #6 on: December 22, 2015, 06:48:58 PM »
Thanks everyone. For some reason this engine doesn't appear to be one of Elmer's more popular ones.  The engine is the size of (and based on) the standby so it's tiny.  It has some tricky soldering required because of the size. The other factor is that the inside of the square extrusion is very rough. It makes sizing the piston a challenge. To overcome that I had to make the piston a bit looser than I would like so it will leak and probably badly. We'll see when I get it together.

Tony

Offline AOG

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Re: AOG's version of Elmer's number 7 Square
« Reply #7 on: December 28, 2015, 08:32:23 PM »
Not much progress in his week. All I got done was to hot blue the steel parts.



I wrote up a thread in the hints and tips section on how I did it.

The thread is here:

http://www.modelenginemaker.com/index.php/topic,5641.msg108336/topicseen.html#new

Tony

Offline AOG

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Re: AOG's version of Elmer's number 7 Square
« Reply #8 on: December 29, 2015, 10:46:22 PM »
Some days it just doesn't pay to get out of bed. I had some time today to work on this engine and it didn't go well. While attaching the base I used the wrong length screw and snapped it off in the hole. Next I tried assemble the rest of the engine and the piston is bottoming in the cylinder. The connecting rod (which is to print) is to long. I have set up the alum pot and I am going to spend the evening making a new (fourth if your counting) con rod. Hopefully tomorrow will be better.

Tony

Offline b.lindsey

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Re: AOG's version of Elmer's number 7 Square
« Reply #9 on: December 30, 2015, 12:36:39 AM »
Sorry Tony, but as you say, some days you might as well stay in bed. Hopefully tomorrow will be better!!

Bill

Offline zeeprogrammer

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Re: AOG's version of Elmer's number 7 Square
« Reply #10 on: December 30, 2015, 02:24:39 AM »
Some days it just doesn't pay to get out of bed.

I disagree.  ;D
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline AOG

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Re: AOG's version of Elmer's number 7 Square
« Reply #11 on: December 31, 2015, 12:24:59 AM »
Well it's alive and a runner. Getting it to run was a killer. After remaking the con rod I discovered that when I had plugged the hole I drilled for the air passage I also plugged the cross hole that goes into the cylinder. I drilled them out  and replugged. I went ahead and counterbored the holes 1/8 to set the max depth of the plugs. I put everything back together and when I turned it over there was a tight spot in the cylinder. Since the cylinder is rectangular you can't ream it or bore it so I had to file it out. When I was done the piston didn't bind but it was much looser than I would like. I put the engine together and tried it. The thing wouldn't run. I checked the valve timing and I noticed that I was getting (very) late admission. I pulled it all back apart and I found the problem. I looks like when I drilled the air passage the bit wandered and I wasn't centered on the bore of the bearing. Using the cut and try method I filed the leading edge of the valve flat until I got proper admission. I put it all back together and it still didn't run. I was leaking to much air past the piston. Time for piston and connecting rod number 5.  I put it all back together and the bore sealed properly but the friction was way to high for it to run. What I really needed was some way to fit a piston ring to seal the bore instead of a machined fit. Then it struck me why don't I wrap con rod number 4 in some Teflon tape. So it did.



I put it all back together and it worked like a charm.

Final pics can be found here

http://www.modelenginemaker.com/index.php/topic,5651.msg108554/topicseen.html#new

Tony