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32x40mm Engine mod help

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Groundhog

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#1
I've been working on making cad & cam drawings of Brian Weebly's 32x40mm engine for awhile now. I have almost all of the plans drawn in Fusion 360 and most of the milled parts CAM completed. (this is Brian's copyrighted material purchased for my personal use only - sorry) http://briansworkshop.weebly.com/

Weather I build this engine or not is still up in the air, but it has been a good project to fill in the days around my back and hip surgeries.

Anyway, I've been refining some of the parts and pieces to my taste but have gotten stuck on one thing. Maybe I've just been looking at it too long but I can't see a good way to adjust the backlash on the timing gear train. The the 2 end gears (crankshaft drive and camshaft driven) need to be fixed in place and backlash adjusted by the center (idler) gear. As you can see from these drawings space is limited on the inside of the frame and nonexistent between the gear and the frame.

click on the pictures for full size

trials drawing 1.jpg A somewhat exploded view. The red shaft is what I want to make adjustable.

geartrain.jpg

inside idler gear shaft.jpg Dark dot is the idler gear axle. This could be extended up to 6mm before it hits the crankshaft web.


top rear.jpg

with brass crank nuts.jpg overall picture of engine

If built the engine is about 10" long x 5.5" wide & tall. Runs on propane.
 

JimDawson

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#2
Put the gear on a cam. With the correct offset and position the backlash will be adjustable. I did it on my mill Z axis gear train, it took me a bit of trial & error in CAD to figure out the correct relationships.
 

Asm109

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#3
Mount the idler on a thin arm that rotates around the crank axis. mill a curved slot near the other end of the arm. lock rotation with one screw and washer. Loosen screw, rotate arm to set back lash, tighten screw.
 
D

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#4
Hi Mike
I think that in the instructions I mention that this shaft can be made eccentric if you encounter meshing problems. you have just enough room to get a wrench between the side plate and the flywheel to tighten the nut after adjustment
The mesurements for the shaft position are for when the gears are made using the single home made cutter . if you intend to use commercial
involute cutters you will have to buy two cutters to cut the gears.
The meshing of the camshaft gear is set by positioning the cam assembly then using a transfer punch to mark the position for the screws.
I will look at the instructions and see if I can find the relevant Page
I am still trying to recover the original CAD files for this engine that I lost in my resent computer crash. Luckily the book files are safe.
and the 5 cylinder radial engine, I don't know what I would have done if I had lost the radial drawings . I now back up everything to a USB drive.
Keep in touch Brian.
 
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#5
Hi Mike
Here are the two pages from the instructions referring to this. The clearance mentioned on page two is the clearance from the side plate to the inner crankshaft flywheel.
Always here to help
Brian.
gear shaft 1.PNG
gear shaft 2.PNG
 

Groundhog

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#6
Thanks Brian,
I've had the plan package spread out all over the place! I guess I've been looking at the pictures and drawings more than reading the text!

I want to keep the 60 tooth gear fixed so as to keep the edges of the top plate aligned with the side plates (thinking of fillets maybe). Still having a hard time envisioning if a single eccentric (on the center gear) will allow gear lash adjustment of all three gears. I's early morning - before caffeine. I'll figure it out as soon as I've had time to experment (in cad) some more.
 
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#7
Hi Mike
The setting of the position of the cam 60t gear is covered in the text ( Top plate assy Pages 1&2 ),
If you wish to create a smoother profie to the top of the side plate I suggest you initially leave the side plate square
and make the sides of the top plate assembly longer.
Then assemble the crank case, Set the lash of the cam gear as per the book, Dismantle the case, Reassemble the side plate and the top plate sides . then profile the top of the two components. You will possibly need an extra screw to ensure the top plate sides do not go out of line.

Brian.
 
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