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Thread: todays tools gloat
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10th Sep 2017, 11:59 PM #2041Golden Member
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Nicely spotted Kryn, I went back for a second look and you're right, it's on backwards (unless there's no lift stroke then I guess it doesn't matter)
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11th Sep 2017, 12:26 AM #2042Golden Member
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Ah, Thanks for that Kryn. Yes the teeth are facing forward and it lifts on the pull stroke. Maybe the cam for the lift pump is 180 degrees out? I will have another look tomorrow night, i always thought push is the cutting action just like the manual saw.
Regards,
Trong
ps: it might not be possible for the cam to be out by 180 if there is one keyway, maybe the motor is turning on counter rotation or that crank gear is inside out?
not making sense if the crank gear is inside out either as the crank pin will be at exact the same location, maybe the motor rotation if it supposed to be lift on push stroke then?
edit3: I have another thought and take it back on that crank gear. It depends on the angle between the keyway and the pin. If 0 or 180 then it's the same, if 90 then it will change, if anything else then it will be out...
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11th Sep 2017, 01:42 AM #2043Most Valued Member
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Hi Trong, if it's lifting on the "pull" stroke, then it's correct, as I said earlier "most cut on the pull stroke", yours is then an exception.
KrynTo grow old is mandatory, growing up is optional.
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11th Sep 2017, 08:44 AM #2044Diamond Member
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This variety of power hacksaw (it was sold under many brands, King Rich etc etc) does cut on the push stroke. I got caught with that when I first got mine because I 'knew' that power hacksaws always cut on the pull stroke.
Its to do with the geometry of the con rod and the drive gear, but basically you get a fast stroke one way and a slower stroke the other way. I guess you could make it cut on the pull stroke if you were to reverse the direction of the motor, but bear in mind that the side thrust from the helical drive gears will go in the opposite direction, that may or may not be important.
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11th Sep 2017, 09:33 AM #2045Golden Member
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I also think it makes sense to cut on the pull stroke as it will give better accuracy due to free play on the components.
Interesting on the fast/slow stroke Bob, I will watch ot tonight. Could it be the resistant on the cutting stroke that "slows" it down?
Regards,
Trong
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I managed to turn the cam 1/2 of a circle and that makes the saw to work in a "conventional" way.
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12th Sep 2017, 07:40 PM #2046Golden Member
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I bought this on Gumtree today, I thought it's the Deckel D bit grinder attachment but it could be something else? The body is about the same as the 2U grinder I have. The base doesn't look to be home made.
20170912_181422.jpg 20170912_182349.jpg 20170912_182402.jpg 20170912_182410.jpg 20170912_182438.jpg
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12th Sep 2017, 07:57 PM #2047Most Valued Member
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Bob, I'm struggling to see how that would happen if the conrod is connected directly to a crank pin mounted to a driven disk or wheel. Not disputing what you have said, but I cant see how that would happen unless I'm missing something.
I know how it works with a shaper but the hacksaw doesnt have a rocker arm system like a shaper.
What have I missed?
peter
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12th Sep 2017, 08:56 PM #2048Diamond Member
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The path of the conrod pivot on the blade frame describes a straight line as it shuttles back and forth, if the centre of the drive wheel is on a continuation of that line then the pull and push strokes are identical.
If the centre of the drive wheel is moved above or below that line (above for the power hacksaw under consideration) thats when you get differences between the two strokes.
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12th Sep 2017, 09:35 PM #2049Golden Member
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Ah, Thank you Bob, that rings the bell. I studied that in "Motion Mechanics" or something along that line but I don't remember anything.
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12th Sep 2017, 09:41 PM #2050Most Valued Member
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Hi Jackaroo, I was looking at that grinding head on gumtree and due to the colour and how the assembly looks I would be pretty certain it was made by warren & brown for some kind of automotive reconditioning machinery.
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12th Sep 2017, 09:45 PM #2051Golden Member
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@Caskwarrior: it has 3 modes->free turning, 180 degrees and lock so that is likely to be tool cutter and grinder attachment some sort?
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12th Sep 2017, 10:00 PM #2052Most Valued Member
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Thanks Bob
I understand it now
peter
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13th Sep 2017, 09:14 AM #2053Most Valued Member
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13th Sep 2017, 02:00 PM #2054Golden Member
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Hi eskimo
I am assuming something like this? V is the same everywhere but not V1 and V2
20170913_125455.jpg
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13th Sep 2017, 02:09 PM #2055Most Valued Member
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