Author Topic: "TINY" This time a water cooled side shaft version  (Read 4729 times)

Offline 90LX_Notch

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Re: "TINY" This time a water cooled side shaft version
« Reply #30 on: March 24, 2018, 05:45:19 PM »
George, the head is an amazing piece of work. 

-Bob
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Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #31 on: March 29, 2018, 12:38:52 AM »
With all the 'big parts' done it's time to start on all the really tiny pieces. I wanted to get the side shaft mounted because all the other governor parts associate to it. I made up two trunnions (bearing blocks) for the shaft and when I fitted the gears they went together very nicely. Probably one of the more complex parts is the bracket that holds the rocker arm, the front of the side shaft where the cam is mounted and the lock-out lever. The best way I could see making the parts was to carve it on the end of a brass bar. The holes were drilled first and then the profile was cut. The block then had to be turned to all four sides to produce the little pad for the lock-out lever on the back side.
The part was then cut away from the block and all the corner radii were filed and sanded smooth. As with the full sized engine spacer bushing were needed to put the bracket at the correct height relative to the head surface.
(sorry for the poor pictures, I think the old camera is starting to give up the ghost)
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Online b.lindsey

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Re: "TINY" This time a water cooled side shaft version
« Reply #32 on: March 29, 2018, 12:52:24 AM »
Coming along beautifully George. As always look forward to your updates.

Bill

Offline Craig DeShong

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Re: "TINY" This time a water cooled side shaft version
« Reply #33 on: March 29, 2018, 02:29:35 PM »
Exquisite work know George, looks great!
Craig

Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #34 on: March 30, 2018, 03:07:16 PM »
 The next part, the rocker arm, although it looks simple became quite a project in machining. The first operations was to clamp a piece of round stock between small v-blocks in my mill vise. The part was indicated to center. A depth cut was made to allow material for the thickness of the arm plus a little to eventually cut off with a slitting saw. The X and Y cuts were made leaving a couple of thousands for the step-off profiling cuts. Two holes were drilled, one for the roller location (0-80 thread) and one for the pivot (.062 dia.) Using my Cad layout I stepped off the shapes and the radius on the roller end.
The round stock was then moved to the dividing head and indicated concentric. The flat surface on the arm was indicated horizontal and the dividing head set to -0-. The hole for the valve adjustment screw was put in (0-80 thread). The part was then put back in the mill vise for the next operation. The thickness of the arm is .062 but the boss on the valve adjusting end is .110 diam. To minimize filing I set the slitting saw to make the initial cut to created the .062 thickness. I moved the saw into the stock laterally only deep enough to allow for the boss on the end. The saw was then repositioned (Z) and the part was cut from the parent stock.
The holes were tapped and the step-offs filed and polished.

 The cam disc was next. I turned a piece of stock to the O.D. and put a counterbore into it to allow for the cam hump. The stock was drilled and reamed .062. The stock was then moved to the dividing head and indicated true. Using a .062 end mill I cut the material away from the face down to the bottom of the counterbore creating the cam hump. On my drawing a gave the exhaust a duration of 200 degrees which means that the cam hump would have to be shaped for 100 degrees. As the roller hits the hump it needs to hit it squarely and drop off squarely so the hump took the shape of a tiny triangle. While it was still on the end of the rod I filed a small radius on the edges of the hump and then cut it free in the lathe. The part was then Loctited to the end of the shaft.

 A roller wheel was made and a brass mounting screw.

The pictures show the parts assembled. I apologize for not taking pictures while making the parts but these are so tiny that it's hard to get a good shot while machining.

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Offline cfellows

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Re: "TINY" This time a water cooled side shaft version
« Reply #35 on: March 31, 2018, 05:27:01 PM »
Hey George, great work, as usual.  What is the diametral pitch of those helical gears you made?
So many projects, so little time...

Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #36 on: March 31, 2018, 05:52:29 PM »
Hi Chuck.
The D.P. is 80. I first picked a diameter that would fit over the crankshaft (.187) plus about .025 metal wall then developed a pitch diameter and pitch that would fit. I tried to keep the spacing between gears as tight as possible so that they would line up with the exaust valve.
gbritnell
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Offline Hugh Currin

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Re: "TINY" This time a water cooled side shaft version
« Reply #37 on: April 01, 2018, 01:25:32 AM »
George:

Very nice design and build. I'd like to try a Tiny and have the basic plans. Likely not the hit and miss, but one of the versions.

Thanks for the build log. Following along, as I can, quietly.

Hugh
Hugh

Offline NickG

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Re: "TINY" This time a water cooled side shaft version
« Reply #38 on: April 01, 2018, 01:25:19 PM »
I like the look of this George , do you know why manufacturers went towards side shaft engines? Were there a lot of advantages? Guess it’s like an overhead camshaft really.


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Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #39 on: April 01, 2018, 06:40:55 PM »
All of the tiny pieces are coming together. I have the whole governor parts train made and temporarily assembled. I have put small springs in place but won't know exactly what weights to use until I see how they react while running. The lockout shaft coming from the governor mechanism on the flywheel is .047 diameter stainless steel. This diameter corresponds with mm1.2 so the shaft ends were threaded that size. Up at the head end 2 small nuts were made to adjust the lockout lever. These are .078 across the flats.
Nick, I'm not sure why this particular style of valve operation and governing was use. It's possible that at the time there could have been patent infringements, much like when the crankshaft was patented on steam engines so for a while other forms of connecting the piston rod to the crankshaft were devised.
gbritnell
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Online b.lindsey

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Re: "TINY" This time a water cooled side shaft version
« Reply #40 on: April 01, 2018, 09:12:03 PM »
Really incredible George. The pictures are great but I can well imagine how small many of those parts really are :o

Bill

Offline Admiral_dk

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Re: "TINY" This time a water cooled side shaft version
« Reply #41 on: April 01, 2018, 10:04:08 PM »
Another beauty from you George  :praise2: .... but I must admit that I don't quite get how the movement of weight on the flywheel is transferred to the linear movement towards the cylinder head ... do the weight function as a wedge ...?... :noidea:

Best wishes

Per

Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #42 on: April 02, 2018, 01:56:07 PM »
Hi Per,
Here's how this type of governing system works.
In this picture you see the shaft with the brass weight on it. The shaft is screwed into a turned disc which has a hole reamed through it that fits the crankshaft diameter. In making the disc it is turned on the lathe leaving a step for the brass ring that you see. As I said it is drilled and reamed through on center to fit the crankshaft. While the disc is still on the shaft that it is turned from it is taken out of the lathe and put in the mill and indicated on center. A hole of the same diameter as the through hole is offset and cut through the disc. In this case the hole is .187 diameter. (4.76mm) and is offset .03 (.76mm) This forms a slot in the disc. The hole for the shaft was drilled and tapped in the disc. The disc was then cut off in the lathe. So now you have a disc that when slid over the crankshaft can move radially .03 from center. The weight and spring return it to center.
Now over top of the shoulder that is turned on the disc you have a brass ring, much like the eccentric strap on a steam engine. When the disc offsets it allows the governor rod to move .03. At this point you're saying "yes, but it oscillates .03 in both directions so it would move the lockout lever back and forth." The answer is yes it does but the governor rod doesn't have a fixed connection to the lock-out lever but rather slides through the hole.
In the second picture you see the governor rod going through the lock-out lever and has two adjusting nuts to set the position of the lock-out lever.  The lock-out lever is spring loaded so it will return to the unlocked position.
As the engine spins the eccentric disc offsets which moves the governor rod forward and thus moves the lock-out lever into position to hold the exhaust valve open. Now as the flywheel rotates 180 degrees the eccentric pulls the governor rod back .03 but being as it's free to slide through the hole in the lockout lever the lever stays in place being held by the tension of the valve spring against the rocker arm.
When the engine slow down the eccentric disc moved back to center so there is clearance between the adjusting nuts and the lock-out lever. Now as the cam moves the rocker arm it frees the lock-out lever and the return spring pulls the lock-out lever back to the unlocked position.
I hope this makes sense? I had to study it when I was building it because I like you had no idea how it worked.
gbritnell
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Offline Admiral_dk

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Re: "TINY" This time a water cooled side shaft version
« Reply #43 on: April 02, 2018, 10:41:28 PM »
Thank you very much for explaining the function. I got the part of cylinder head before I asked about the rest - it was the offset of the disk that I hadn't realized, as I thought that it "squeezed" the ring and that didn't make any sense ...  :noidea: ....
But that it oscillates the rod to the head forth and back in the active mode makes sense too now that I got the rest + that this haven't got any influence when it moves away on half the cycle.

I like this, even though it is a brain twister (or maybe just because it is :stir: ).

Offline gbritnell

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Re: "TINY" This time a water cooled side shaft version
« Reply #44 on: April 09, 2018, 07:34:54 PM »
 As with most original design projects there's things along the way that need correcting or modifying. Such was the case with the rocker arm. I always have one drawing that's kind of an assembly sheet. I use this to compare parts while building. When I developed the rocker arm I used two views, the front and top. Well in the top view for some reason I didn't have the valve layer turned on so I just went on my merry way of creating the rocker arm. As I was assembling the parts the other day I realized that the valve length/rocker arm shape collided. Hmmm, back to the layout. I couldn't make the existing rocker arm work as I would have had to shorten the valve stem way too much so I redrew the rocker arm and with the combination of the two was able to get back on track. This was my repair drawing. I then changed the main drawing to a completely set of new dimensions to allow the valve stem to be almost as long as the original.

 I now have all the governor bits made and fitted. I mounted the flywheel and governor eccentric on a dummy shaft and spin it in the lathe, adjusting spring weights until the eccentric moved at about 1200 rpm. I figured this would be a good starting point as these little engines like to run fast no matter what.

 The first 4 pictures show everything assembled. The spring is .008 diameter wired wound on a .04 diameter mandrel. What a son-of-a-gun trying to put the eyes on the ends of the spring.
The 5th picture shows the lock-out lever in position holding the rocker arm in the valve open position.
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