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Old 12-27-2002, 09:46 PM   #91
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Default Cobra HELP

Can anyone give me the run down on setting up my new lathe that came without instructions? I have the diamond tool. Does the arm spin towards the operator or away? The point up or down? How far above centerline? I think I have it set up ok but when it cuts it makes a noise that may be vibration related. Also the grooves in the comm have rough edges and the exacto wont work to clean them. HELP! and THANKS
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Old 12-27-2002, 09:55 PM   #92
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I shimmed my old Cobras bit with thin pieces of cardboard. It wasn't any more than 1/8 inch above center. The arm should spin away from you. If you touch the bit to the comm with it spinning toward, trust me, you WILL know its the wrong way. The point should be down.
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Old 12-27-2002, 10:39 PM   #93
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Default Re: Cobra HELP

Quote:
Originally posted by onefastlap
Can anyone give me the run down on setting up my new lathe that came without instructions? I have the diamond tool. Does the arm spin towards the operator or away? The point up or down? How far above centerline? I think I have it set up ok but when it cuts it makes a noise that may be vibration related. Also the grooves in the comm have rough edges and the exacto wont work to clean them. HELP! and THANKS
A- the tip of the bit should be DOWN

B- the surface of the comm that contacts the bit should be spinning UP (this makes it spinning away from you)

C- the tip of the bit should be just SLIGHTLY (as in .01") above centerline. This means that the surface of the comm contacts the tip without interference from anything else. It should contact the tip as flat as possible, thus it should be as close to centerline as possible, but up a hundredth keeps any interference away and is safe.

D- if you have bad vibration, if the grooves in the comm are filled in with comm material, if it left grooves (a serrated comm. . .) then you had your lathe set up probably backwards. It MAY have ruined your bit. . .I've been there and done that.
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Old 12-28-2002, 01:54 AM   #94
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- the tip of the bit should be just SLIGHTLY (as in .01") above centerline. This means that the surface of the comm contacts the tip without interference from anything else. It should contact the tip as flat as possible, thus it should be as close to centerline as possible, but up a hundredth keeps any interference away and is safe.


This is correct. I rechecked mine.
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Old 12-28-2002, 10:43 AM   #95
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Boomer & GhostTown- Thanks guys for the advice. I was running the slave motor the wrong way. Got lucky and didnt chip the bit. I was using a p2k. Do the slaves from Cobra have reverse winds? I have read about 55t motors that run on 12v power. My 4cell wont hold a charge very long. power supply would be much better, any suggestions? Thanks- J.C. from K.C.
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Old 12-28-2002, 11:55 AM   #96
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A cheap 540 silver canned Tamiya motor is the best slave that I've found. They don't seem to mind being hooked up in reverse and they run very cool. As well they're very easy on a 4-Cell packs run time. Usually $10 at your LHS.
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Old 12-29-2002, 09:47 AM   #97
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hi guys,
tried a cut again today, but with a different amature ( p2k2) and it cut fine. But then i tried the orion stock core and it was screeching again, doesnt sound like chatter as i use lathes at college.
Also sometimes i am going down the comm and it jumps and takes more out, doesnt take chunks out but goes in a little deeper. i think my lathe has had it.
Anyone got a suggestion for a new lathe, the xipp one looks good (only 117 with the v blocks) has anyone got an eagle racing one? Hudy also looks good but i have no local supply over here :-(

see yah
thanks

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Old 12-29-2002, 12:20 PM   #98
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Default Screech and Chong

b3buggy;

Quote:
But then i tried the orion stock core and it was screeching again, doesn't sound like chatter as i use lathes at college.
There is something that is loose that is causing the problem you are seeing. It may be as simple as the Driving O-ring being stretched out and not pulling the Armature down into the "V"-blocks solidly enough. Don't let the O-ring run in the windings as this can cause problems too.
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Old 12-29-2002, 12:33 PM   #99
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hi pops,
yeh just after the post i thought that, the p2k2 has less of a gap in the armature stack so it sort of rides above the groove, but the core has a large gap so the only place for it to run is on the windings, i tried on the stack but it just falls off onto the windings, so i pulled the slave down lower to make the o ring tighter.
the cut was ok then, but still sometimes it takes a little deeper cut.
but it is better.
i think i will adjust the position of the pulley on the slave motor arm and bring it out a little more, so that i can get the o ring on the stack without it falling of.

see yah

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Old 06-10-2005, 08:54 PM   #100
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So, what kind of sound should be heard when cutting? I have some hi pitched sounds, which arent consistant across the comm. Is this from the comm being mishaped? Im also getting some scratches. My manual says lines are ok, but im not sure to what extent

**edit, damn i sure bumped an oldie
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Old 06-10-2005, 09:11 PM   #101
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Lines are not good. You should hear a very light filing sound. The best cuts are the quietest. Just take a Sharpie and blacken the spinning comm. Then make a very shallow pass. It should be very quiet. If the pass is loud or you can see the copper coming off the comm, then you are cutting too deep. A good pass on a Trinity and Reedy motor should look like perfectly smooth shinny copper. The Orion motors should get a rainbow glare after a smooth pass. Don't settle for lines or scratches, if you've got a diamond bit then you can make perfect cuts with some practice and patience.
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Old 06-10-2005, 09:18 PM   #102
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hrm, ok. i have been using a sharpie, but im still getting lines. Is there something that causes the lines? feeding too fast/slow? slave motor too fast/slow ? scratched bit? Or perhaps my bit isnt positioned correctly?

Oh yea, im using a carbide bit
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Old 06-10-2005, 09:25 PM   #103
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Quote:
Originally Posted by NVisible
Oh yea, im using a carbide bit
There's your answer.

A diamond bit might solve your problem. If your tight on cash, then just use these settings.

Med/tight tension on the o-ring. Tip of bit .001 above center of comm. 2.8 volts. Trinity royal oil on v or u blocks. 3-6 passes to clean up a 3 run comm.
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Old 06-10-2005, 09:29 PM   #104
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Ahh ok. Im not racing competitivly or frequently, so i dont think a diamond bit is in the budget. Ill give those settings a shot. Thanks a ton for your help!
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Old 06-10-2005, 09:36 PM   #105
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also try using a cutting fluid. it should give u a smooth finish
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