Having a few issues with my machine and wondering if anybody can point me in the right direction with respect to diagnosis and repair suggestions. I'm not well schooled enough in the finer points of evaluating certain parts of these machine tools to feel confident in making an accurate diagnosis.
The problem is that when engaging the higher feed rates with the quick-change gearbox, it bogs down, spindle speed decreases, and the belt will slide off the drive pulleys. This is WITHOUT doing any actual work.
The gearbox may be compromised already, as there is a gear missing from the inside. Not sure that it has anything to do with the bog problem but thought I"d mention it. When the lever on the left is placed in position "E", there is no power supplied to the lead screw.
Here's how things run with the gear levers in various positions.
With the lever in position "A", this is where the drag on the motor is most noticeable. With the lever in this position, the motor is obviously overloaded, and the only way the belt stays on is if you are using the back-gear, especially with the right-hand lever in the position furthest to the left (highest feed rate). The lathe really does sound like its struggling to run at full speed, even if its not doing any work. Actuating the apron feed makes it worse. There seems to be a "growl" emanating from the vicinity of the gearbox. It acts as if somebody is applying a brake to the spindle. Running the motor in reverse yields a higher spindle RPM and less gear noise.
With the lever in "B" position, the drag and growl are less noticeable, you can cut metal, but the spindle revs still really drop.
Lever in "C" or "D" position - no apparent drop in spindle RPM, regardless of position of the right-hand gearbox lever. Much quieter operation also.
Position "E" - no lead screw engagement, ergo no load. Stone silent here, hehe.
I've fiddled with the gear engagement on the reversing and leadscrew gears. The gear lash is set so that it is about the same as I set it on my South Bend 9A, which runs dead quiet in all gearbox ranges. With the reversing lever in reverse, things run quieter than in forward. With the lever in neutral, there's no noise at all, which one would hope for as its only the spindle rotating. The gear driving the gearbox input shaft is the 48 tooth gear. I have the 24 tooth gear but haven't figured out how to install that one yet, I don't have the manual for this machine yet, its in the mail but should be here shortly.
The only work I've done to the lathe was replacement of spindle bearings, installing new shaft bushings in the drive unit, and making a bushing to support one end of a shaft that is in the gearbox. There was some sort of a split bushing that broke apart and fell out, I replaced it with a part that I machined up and tapped into place. it doesn't seem to be causing a binding condition in the gearbox assembly because everything moved freely when I turned it by hand when the gearbox was off the lathe, but it sure doesn't work when re-installed.
Lead screw looks straight and undamaged. Haven't tried to run the machine with the apron removed to see if the apron mechanism is causing any overload, but I doubt that it is. Still using the same flat belt that came with the machine, tension looks/feels about right; I suppose it could be slipping, but I've had some pretty crappy belts on my South Bend lathes and never ran into anything like this.
Any advice, insight or suggestions with respect to the bogging down issue y'all can offer would be greatly appreciated, thanks in advance.
Chris S
Logan model 820 problems
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Outboardguy44
- Posts: 15
- Joined: Sat Mar 24, 2007 5:23 pm
- Location: Southern Ontario, Canada
Logan model 820 problems
Chris S in C eh N eh D eh, where too many motors (or lathes) are never enough
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Jose Rivera
- Posts: 3803
- Joined: Wed Feb 21, 2007 9:21 pm
- Location: Vallejo California
Ideally this issue can be better addressed by a Logan user or someone that know these machines in and out.
What I can tell you is that my lathe, a Emco Maximat V10, has a lever that one has to change for cutting feeds and for thread cutting.
Could it be that you have it set for thread cutting?
In this case, the quick change gears will go like a bat out of hell making the gear oil actually shoot out of the slot for the change lever.
Something like what I am describing could bug-down the motor if the settings are for high spindle speed.
What I can tell you is that my lathe, a Emco Maximat V10, has a lever that one has to change for cutting feeds and for thread cutting.
Could it be that you have it set for thread cutting?
In this case, the quick change gears will go like a bat out of hell making the gear oil actually shoot out of the slot for the change lever.
Something like what I am describing could bug-down the motor if the settings are for high spindle speed.
There are no problems, only solutions.
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Retired journeyman machinist and 3D CAD mechanical designer - hobbyist - grandpa
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Retired journeyman machinist and 3D CAD mechanical designer - hobbyist - grandpa
Hmmm...
I have a similar Logan, actually a 200 w/ a 820 apron and I am unsure what could be causing your problem. What are you using in place of the 24T gear? What happens with she cross feed engaged (both with and w/o the clutch engaged)? It is impossible to engage both the halfnuts and the clutch at the same time unless something is missing in the apron and it sounds like you would notice that immediately. I have heard that a worn / mis-adjusted clutch can drag although I have no direct experience with that issue. You could see what adjusting it will do. As you can tell I think the issue is with drag in the apron. I would pull it and see if something is amiss. (Remember to support the lead screw) Another possibility could be severely worn worm gear bushings. Logans do have an issue with them. The originals are steel or iron (not sure) and do not oil well. This could allow the worm gear to get way out of alignment with the pinion and or allow it to shift enough within its cavity so it contacts the apron casting. Mine has wear in the bushings but not that severe. It is noticeable when starting a cut, the carriage will not start moving until the worm moves enough to contact the bushing. Mine also has radial wear but not so much that I worry about it. Logan sells new bushings as well as the worm gear ($$$). The bushings don't cost too much an are now bronze. I have the bronze to make my own but have not gotten around to it yet. I will have to turn the worm gear also as its diameter has worn, but there is enough meat left there to get is straight again albeit a little smaller in diameter than original.
JR
I have a similar Logan, actually a 200 w/ a 820 apron and I am unsure what could be causing your problem. What are you using in place of the 24T gear? What happens with she cross feed engaged (both with and w/o the clutch engaged)? It is impossible to engage both the halfnuts and the clutch at the same time unless something is missing in the apron and it sounds like you would notice that immediately. I have heard that a worn / mis-adjusted clutch can drag although I have no direct experience with that issue. You could see what adjusting it will do. As you can tell I think the issue is with drag in the apron. I would pull it and see if something is amiss. (Remember to support the lead screw) Another possibility could be severely worn worm gear bushings. Logans do have an issue with them. The originals are steel or iron (not sure) and do not oil well. This could allow the worm gear to get way out of alignment with the pinion and or allow it to shift enough within its cavity so it contacts the apron casting. Mine has wear in the bushings but not that severe. It is noticeable when starting a cut, the carriage will not start moving until the worm moves enough to contact the bushing. Mine also has radial wear but not so much that I worry about it. Logan sells new bushings as well as the worm gear ($$$). The bushings don't cost too much an are now bronze. I have the bronze to make my own but have not gotten around to it yet. I will have to turn the worm gear also as its diameter has worn, but there is enough meat left there to get is straight again albeit a little smaller in diameter than original.
JR
I have no knowledge of your Logan lathe but based on similar lathes, your problem may at least partially be the 48T gear. Generally the larger stud gear is used only when cutting the very coarsest threads and only with the gearbox in the A range. The lathe is generally run slowly, probably in back gear. The 48T gear causes a 2/1 speedup in the feed train so should not be used otherwise.
You should also check your gearbox and entire drive train to be sure everything is well oiled and turns without binding. You can drop the gearbox levers to isolate parts of the gearbox and drive train to help check for binding. Noise in the gearbox is not a good sign and should be checked out. Of course if it is running twice as fast as it is supposed to, that will increase the noise. Hope this helps.
Don Young
You should also check your gearbox and entire drive train to be sure everything is well oiled and turns without binding. You can drop the gearbox levers to isolate parts of the gearbox and drive train to help check for binding. Noise in the gearbox is not a good sign and should be checked out. Of course if it is running twice as fast as it is supposed to, that will increase the noise. Hope this helps.
Don Young
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Outboardguy44
- Posts: 15
- Joined: Sat Mar 24, 2007 5:23 pm
- Location: Southern Ontario, Canada
Ok, thanks for the suggestions. I did some trials running the lathe with the apron removed from the equation, and we can safely eliminate the apron as a probable cause and focus on the gearbox.
Disengaging the gearbox levers allows the input gear to be turned easily by hand. Engaging the levers in the higher speed ranges definitely increases the effort needed to rotate the input gear.
Looks like the idler shaft where all the small gears ride on is bent. Well it doesn't look like it, it IS bent, no doubt about it. The new bushing I had made previously eliminated most of the play that was present between that shaft and the gearbox housing. I had left a shoulder on the bushing so it could be pried out if necessary, and without the bushing in there the end of the shaft wobbles considerably. I took the gearbox all apart and checked the shaft against a straight edge and verified that it is bent, so I guess the next step is to make a new shaft. Not a big job. This gearbox has been apart before and I can see signs of abuse elsewhere so hopefully making a new idler shaft and other shaft bushings will put this machine right again.
Thanks again for the input.
Chris S
Disengaging the gearbox levers allows the input gear to be turned easily by hand. Engaging the levers in the higher speed ranges definitely increases the effort needed to rotate the input gear.
Looks like the idler shaft where all the small gears ride on is bent. Well it doesn't look like it, it IS bent, no doubt about it. The new bushing I had made previously eliminated most of the play that was present between that shaft and the gearbox housing. I had left a shoulder on the bushing so it could be pried out if necessary, and without the bushing in there the end of the shaft wobbles considerably. I took the gearbox all apart and checked the shaft against a straight edge and verified that it is bent, so I guess the next step is to make a new shaft. Not a big job. This gearbox has been apart before and I can see signs of abuse elsewhere so hopefully making a new idler shaft and other shaft bushings will put this machine right again.
Thanks again for the input.
Chris S
Chris S in C eh N eh D eh, where too many motors (or lathes) are never enough
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Outboardguy44
- Posts: 15
- Joined: Sat Mar 24, 2007 5:23 pm
- Location: Southern Ontario, Canada
Finished what repairs I could on the gearbox. Made a new idler shaft to replace the bent one and replaced every bushing. It works better, and is noticeably quieter. The gentleman who suggested that the 48 tooth gear might be a big part of the problem probably had it right. Flat belt will still come off the pulley but only at the very highest speed range. In all other speed ranges, it works more like you'd think it should. I'll change over to the 24 tooth gear as soon as I figure out how to configure it. Will do the serpentine belt change as well and lose the leather belt. Thanks for the input eh.
Chris S in C eh N eh D eh, where too many motors (or lathes) are never enough