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My webster build
NickG:
Doug,
It will be interesting to see a different method of cutting gears. This is going to be my stumbling block on an ic, unless I make a 2 stroke or buy them in.
Nick
dbvandy:
I was totally engulfed with working on the Otto yesterday afternoon and then took the little lady out to dinner for V day. Will turn a quick blank and show you what I did.
krv3000:
:mmr: well thats one nice job well dun
dbvandy:
Here is what I did to cut the gears. The actual blank for the 40 tooth on the motor was thicker and had a small hub for mounting the cam, but you will get the idea (I had some 3/16 inch plate laying around...)
I turned the blank to the correct OD for the 40 tooth gear that I was copying from the change gears on my 7x12. If you don't have a gear to copy, you can easily cut a circle into 40 even slices buy using excel and putting in 40 1's then pie graphing it. presto... 40 even divisions, you can see the printed pie graph in the pic with all the parts. I did not need to do this for this build, but have used this in the past for other times I needed to divide a circle. Then you double tape it to the blank, centering needs to be very close, but perfection is not critical. You could tape it up before you cut the ID in the blank and it would be perfect...
I turned an arbor to match the ID of my sample gear and drilled the same ID into the gear blank. (Later, after the gear was cut, I chucked it back up on the finished OD and turned the ID to match my bearings and the cam hub OD to match the ID of the cam.)
Then all you have to do is start cutting teeth with the cutoff wheel. I chucked mine up in my lathe (and put some shop towels down to protect the ways) just because it was easier to hold the Dremel steady when I rested my arms on the table the lathe sits on. The 20 tooth was done first (and then a large piece was pressed over its hub part so I had a place to put in the set screws). You can see where I got a little deep by the cuts in the washer on my arbor. That was during the "learning phase" when I was trying to do it with a file. (bad idea, no control and takes FOR-EV-ER!!!) 45 minutes and 6 teeth later is when I decided to use the Dremel. Great decision.... it only took about 15 minutes after that to finish the 20 tooth. Then I made the 40 tooth with the same process. I did then go back with a small hand file to even out the teeth and make them pretty.
I had a sample gear so I could duplicate the depth and profile radius of curvature, but for this motor it is not SUPER critical as it is low speed and next to zero pressure on the tooth face. Just look at any other gear and try to match the basic shape. You could also look online and there are programs that tell you how deep the tooth should be and you could put that dimension and the OD dimension on the pie graph with a compass before you mount it to the blank.
My gears:
20 tooth: .864 OD .682 depth of tooth
40 tooth: 1.653 OD 1.508 depth of tooth
This might not be the way a "real" machinist would do it, but without making a ton of tooling and lacking a true milling machine and a rotary table, this worked just fine for me. Total time for the three teeth shown was about a minute of cutting.
Hope this helps... feel free to ask questions if needed... I am pretty easy...
Doug
bigmini:
Wow. Here I was thinking that cutting gears was out of reach for me. Well done! :clap: :clap:
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