Another (unsure) Upshur twin (lots of beginner questions?)
- Thread starter timo_gross
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Timo, see my comments about the conrod hitting the liner and my suggested fix
https://www.homemodelenginemachinist.com/threads/upshurs-opposed-twin-engine.36037/post-410429
9mm at the bottom and 6mm at the top would also work
https://www.homemodelenginemachinist.com/threads/upshurs-opposed-twin-engine.36037/post-410429
9mm at the bottom and 6mm at the top would also work
Last edited:
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The cam shaft gear was made today. (from some cold rolled mystery steel) I have a 0.5 module hob, i decided to go with that.
0.5 module gears compared to 0.528 module gears (aka 48 pitch) have little smaller teeth. So I adjusted the counts from 30/60 to 32/64.
That pair would have a center distance of 24 mm which is then 0.18 mm too large.
I try to leave both blanks 0.18 mm smaller in diameter, and keep the tooth depth same. I am hoping I will get away with it.
Thre blanks, one was in the middle, so the burr is very small, one has a burr on the climb cut side and the 3rd one has a little messed up tooth profile.
Deviating from the schedule I gave the crank shaft a try.
I found a big plate hot rolled steel 16 mm thick. I could cut a strip off with the band saw that was roughly the proper length.
Drilling center spots on both ends, using the toolpost as the workholding, with the center drill in the collet block. For height I made a scribe line, for distance using the digital helper.
Interrupted cutting at low rpm with patience went almost uneventful. (The plan suggested to drill and mill out parts before, but I went with plunging directly) The most irritating thing is that the part becomes "transparent" which requires a lot of attention.
The burr in the last plunge cut was quite big, but it went away as soon as the diameters of first and second plunge cut matched. I made a block that fitted nicely into each gap.
To keep the corners sharp on the crank I made a left and right hand skinny parting tool.
The first trial was totally annealed, because of insufficient patience and cooling. The second went flying, when I wanted to touch up the front angle.
Number 3 and 4 were better. (0.5 mm wide)
After lot more work, interrupted cutting I have my first single piece crank shaft. Might need some modification later. (is a little bit too long on both ends and no gear mounted yet.
Greetings Timo
0.5 module gears compared to 0.528 module gears (aka 48 pitch) have little smaller teeth. So I adjusted the counts from 30/60 to 32/64.
That pair would have a center distance of 24 mm which is then 0.18 mm too large.
I try to leave both blanks 0.18 mm smaller in diameter, and keep the tooth depth same. I am hoping I will get away with it.
Thre blanks, one was in the middle, so the burr is very small, one has a burr on the climb cut side and the 3rd one has a little messed up tooth profile.
Deviating from the schedule I gave the crank shaft a try.
I found a big plate hot rolled steel 16 mm thick. I could cut a strip off with the band saw that was roughly the proper length.
Drilling center spots on both ends, using the toolpost as the workholding, with the center drill in the collet block. For height I made a scribe line, for distance using the digital helper.
Interrupted cutting at low rpm with patience went almost uneventful. (The plan suggested to drill and mill out parts before, but I went with plunging directly) The most irritating thing is that the part becomes "transparent" which requires a lot of attention.
The burr in the last plunge cut was quite big, but it went away as soon as the diameters of first and second plunge cut matched. I made a block that fitted nicely into each gap.
To keep the corners sharp on the crank I made a left and right hand skinny parting tool.
The first trial was totally annealed, because of insufficient patience and cooling. The second went flying, when I wanted to touch up the front angle.
Number 3 and 4 were better. (0.5 mm wide)
After lot more work, interrupted cutting I have my first single piece crank shaft. Might need some modification later. (is a little bit too long on both ends and no gear mounted yet.
Greetings Timo
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