SB9A restore and retrofit 3 phase/VFD - Page 3
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  1. #41
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    What gear head did you mean?

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    To start a rap up of this project, I will tell one more thing before I summarize and detail my expenses. When finished with the rebuild, I had 5 lock washers and a pin left over. I wasn't too concerned with the lock washers because they may have been associated with the countershaft or the old table bolts, but the straight pin was driving me crazy. I pulled the gear box and nothing was obvious. This was a 2nd gearbox pull because of the swapped tumbler assemblies. Then, I pulled the gear box a 3rd time to remove the apron and looked that over. Then, sitting in front of a PDF of the 9A exploded parts, I noticed the pins were described by size. I measured the length and diameter, scanned the parts list and Bingo, it was the "dowel" that inserted thru the holes of the 4 larger gears of the gear tree. It was totally hidden from visual inspection. In reality, it's importance was more of an aid to make the process of lacing the gears easier.

    I felt better, though.

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  4. #43
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    capture9608.jpg
    Here are the "final" spindle RPMs for this setup. VFD to deliver 93% of cycles for a spindle speed of 600 RPM. This cuts off the vibration I was getting above that. I still think the vibration is related to the belt drive, but that is another discussion.

    Secondarily, I liked iwananew10K's idea of a 2 speed motor pulley to incorporate the middle cone spindle pulley for higher spindle rpm's. The proposed rpm's is suggested in red.

    This maybe an earlier project and would allow a rebuild of the motor mount plate to shift the mount over left enough for positioning of the 2 place motor pulley. This would be the time to beef up the mount for any resonance at higher speeds. However, I do have some jobs ready to go, namely turning a 2" x 2" aluminum contact wheel for a belt grinder out of 3.5" x 3.5" round bar stock.

  5. #44
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    I did the exact thing you are purposing to my South Bend 9. I Mounted the motor under the stand and a hinged counter shaft with 2 belts to change the direction of the belt.

    I will post some pics and more detailed later.

    The the basis is a 1.5HP baldor 3 phase motor, 1725 rpm with the pulleys set up to turn 700 RPMS at 60HZ, I forget the exact numbers but from around 150 rpms to 1200 rpms it has at least 1/2 HP (if you cut the speed in half so does the HP). In back get you can cut the speed by 1/4 with 4 times the torque. The catch is running at 700 RPMS you have the full 1.5HP and could possible break the lathe if you push it to hard. It is running a 6 rib serpentine belt that is tensioned to act like a clutch if something binds up. It is running off a vector drive VFD. It has been running 8 years like that.


    But a 1hp or 1.5 HP motor set up with a VFD turning ~700 rpms at 60HZ will get you what you are after.

  6. #45
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    Here is a link to the thread with some pics of my 9c

    Pics of my Direct drive 9in with VFD.

  7. #46
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    capture0610.jpg
    Yes, I agree with most here that the SB9 is a machine for slow speeds and HSS tooling, with a good working spindle speed range up to about 700 RPM.

    Attached is a general torque curve from the KB electronics KMBA manual, comparing inverter rated motors with standard industrial motors where the torque is delivered early on by 10 cycles or less (1/6 of full 60 cycles) whereas regular TEFC motors don't develop torque until higher in the cycle range, thereby using higher HP motors to add torque at lower speeds.

    Every install is so application specific, example being a belt grinder where a 1750 rpm 3 phase motor can be run at upper rpms and even up to 2X nameplate rpm with small loss of torque but no loss in cooling from the fan.

    Anyway, that's a great build on the direct drive 9 with VFD. I can't put the drive under table because I have to have a bench top install with limited space at the moment. However, I am thinking of rebuilding the motor mount using square heavy gauge tubing like yours.

  8. #47
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    https://drive.google.com/open?id=1-6...8ITfOdW0cMp6Tr
    Look ma no hands!

    This is a big deal to me, power crossfeed. I have been wanting this for a long time. As said by fellow PM member kopeck, paraphrasing that a Precision Mathews PM-1030V "may" have a few more capabilities, but it and maybe the 8.5" lathe from little machine shop is the lowest priced lathe with a power crossfeed.

    Compared to those options, my out of pocket costs are a 1/3 of that here in Calif.

    These are light cuts getting to know the feed rates. This will be a contact wheel for a belt grinder.

  9. #48
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    First item, I pulled from the garbage can to take a photo, is the Harbor Freight rubber caster wheel cut from its base and chiseled keyway to fit the motor shaft in order to turn the original SB motor pulley into a flat crowned pulley. I will now throw it away again. Seen on top is the aft mentioned mini lathe spindle that will be the back plate for the 3 inch.
    20190614_173603.jpg

    It would have been so easy to pay ebay $42 for a backplate for the little 3" 3 jaw chuck I had left over from the Chinese mini lathe. Presently, I will rely on the original Cushman 3005" which shows good run out precision, the 3", and hopefully a 6" 4 jaw chuck very soon. Well, I remembered the 3" chuck spindle that I had stashed in my "shed", when I replaced it in the Chinese min lathe with a 4" spindle/chuck. So, being non-hardened, I cut the spindle and with a HSS cutter since I don't have a boring bar yet, will bring it out to a 1.34" bore for threading.
    https://drive.google.com/open?id=1-8...GSA-LmLW4DL-JI
    Last edited by JimBuchanan; 06-14-2019 at 11:42 PM.

  10. #49
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    Default Feedback request on belt slippage

    Now that the "retro-mod" 9A/VFD is online and I'm getting experience with the greater cutting capacity over the little chinese mini lathe, I'd like to ask for feedback on acceptable cutting capacity of an original 9A with the countershaft reduction wheels.

    With the 3/4 hp 1150 rpm motor and back gears, I get all the torque I need up to 120 rpm spindle speed. I'm experimenting with the VFD and largest cone pulley at a roughly 1:2 reduction and serpentine belt tensions. The belt tracks perfect due to the available adjustments and there is no vibrations up to 600 rpm spindle speed. The VFD has a feature called Slip Compensation and does kick in to maintain rpm's under load, which even the Chinese lathe had. However, I am getting belt slipage on more aggressive cuts. The belt is a .8 inch and 6 rib.

    So, I'd like to understand the cutting capabilities of the original SB 9A, and advice on belt tensions if possible.

    The larger the diameter of work piece, the greater the torque requirements. I've been turning down a 3.5" by 3" long 6061 aluminum solid rod to final 2.0" diameter at 200-400 spindle rpm (direct large cone pulley) and have gotten belt slippage. What depth of cut (true depth of cut, not diameter reduction) would you get with your 9A before belt slippage? And can the flat belt tension from the cone pulley to countershaft be described somehow?

    Thanks.

  11. #50
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    the weight of the counter shaft and motor on my lathe is enough to stall a 1/2 hp dc drive in the slow speed, so 500 rpm max iirc. that's 5.4 foot pounds. in reality my motor might be delivering up to 3/4hp, so increase that by 50%.

    so, figure that's 30 pounds of slippage at the belt given a 2" radius, 0.4? friction coefficient, that accounts for the 70 pounds of weight hanging on the belt. my belt is fiberglass packing tape btw.

  12. #51
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    I wish I could access my old videos on PB...parting 5.5" diameter steel,cast iron for bachplates, reducing 1" 1018 to NOTHING in a single pass(1/2" DOC)
    Stuff no 9" should ever do.
    On a 9" with 1HP 1140 motor and VFD through the original reductions.

    All with hand ground HSS.

    I actually had to go back to the original motor once I got a bigger lathe as it became obvious my set up was capable of destroying my 9" which as 9s go was nearly pristine.

  13. #52
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    I am using my retro-mod 9A initially to gear up capabilities. Here is a thread dial I made for $6. $4 for the 16 tooth gear from China, $2 for a 3/4" hex bolt that is the body of the unit and a 1/4" carriage bolt I had on hand for the dial/axle.

    I understand the 4 quadrant dial with 16 tooth gear will indicate even and odd imperial threads, which is good for the present. If I ever need 1/2 threads, I'm sure I can deal with that, then.

    Oh, and of course I will easily calibrate the dial to the lead screw with ample room/space on the dial bezel.

    It's a good thing this forum has a long memory for all the accumulated knowledge, because there really isn't a lot of current activity.
    20190711_183249_2.jpg

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    I would have liked to have seen parting 5.5" diameter. . . Why would you disassembly a 6 pole 1140 rpm motor with c/shaft that was performing so good?

    I'm liking my 6 pole 1140 rpm motor a lot. Yes, I could and will improve the mount, but it works good for now.

    Quote Originally Posted by iwananew10K View Post
    I wish I could access my old videos on PB...parting 5.5" diameter steel,cast iron for bachplates, reducing 1" 1018 to NOTHING in a single pass(1/2" DOC)
    Stuff no 9" should ever do.
    On a 9" with 1HP 1140 motor and VFD through the original reductions.

    All with hand ground HSS.

    I actually had to go back to the original motor once I got a bigger lathe as it became obvious my set up was capable of destroying my 9" which as 9s go was nearly pristine.

  15. #54
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    mine was performing TOO well, it would have eaten itself given the chance.
    I had a bigger lathe and was starting to teach my son how to use the 9",, thus the reason for going back to original.

    so as not to give the wrong impression, the 5.5" parting was for backplates so there was a center hole, and it *was* a slow process, IIRC it took about 30 minutes, maybe a bit longer and I also had to stop a couple times to let things cool down and reset the feed rate but it did it nonetheless.

    2.5" I did on a regular basis, no problem whatsoever.


    PS- yes, you scored a really sweet motor! Once you refine things to realize it's full potential you should have a sweet set up...you seem like a capable fellow,maybe even make a simple Hi/low gearbox, the parts are cheap and easy to source...the gearbox could be a stand alone unit with your motor mounted directly to it, lots of possibilities!

    nice job on your dial,never could figure why anyone would spend 200 bucks for one.

  16. #55
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    Quote Originally Posted by iwananew10K View Post
    PS- yes, you scored a really sweet motor! Once you refine things to realize it's full potential you should have a sweet set up...you seem like a capable fellow,maybe even make a simple Hi/low gearbox, the parts are cheap and easy to source...the gearbox could be a stand alone unit with your motor mounted directly to it, lots of possibilities!
    Since you mentioned this, a further thought. The 5 ribbed .8" wide serpentine belt I used is tensioned the South Bend recommended 1" flex between the motor and spindle cone pulley. It gives good traction, but I have made it slip for example when parting steel. I understand the clutch like function of protecting the gears, but I may redo that part with a wider 6 rib belt. There was another very similar 9A build I found that he ground a parting bit to a V and cut 6 grooves, as one would cut a thread, for the serpintine belt in the pulleys. Since spindle cone pulleys are so plentiful on ebay, I might try this on the 2 largest pulleys and make a motor pulley with 2 corresponding grooved pulleys. The biggest reduction equal to what I have now would get me to 600 rpm spindle and the other reduction would be a high speed at least over 1000 rpm. After a little math, it appears the 2 motor pulleys really could be the same diameter, as the middle spindle cone pulley is significant smaller at 3.25" versus the big one at 4.25". The only problem with this idea is when in high gear (middle cone pulley), the motor position would be and inch or so out due to the shorter belt path. So, I would need a 2 step tensioning system.

    I really believe the belt system is the source of vibration or harmonics at around 700 rpm spindle speed on my setup. The spindle bearings are in good shape and within the tolerances published. I believe this whether the motor is physically attached to the ways or separately mounted to a common table. Its the belt speed feet per minute that's the villain, I think. With a high gear, the belt speed feet per minute goes down. My theory is that the vibration/harmonics will go away.

  17. #56
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    cutting grooves and using a wider belt won't help IME.
    the 1" deflection thing doesn't really apply in your case for a couple reasons.
    shorter belt plus the poly v for all intents has no stretch.

    Sound like your belt is too loose...those poly v belts don't slip easy.

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    The automotive poly V belts are designed to be used with grooved pulleys. If they can provide increased traction with less sideways load on a 9A spindle, why wouldn't that be a good thing?

    As far as the mentioned vibration/belt harmonics at above 700 rpm spindle speed, I calculate that as about 600 ft/minute. The original high speed countershafted lowest gear using the largest spindle cone pulley travels at about 450 ft/min. The middle speed is about 600 ft/min. At some point I will try a 2 speed setup.

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    Quote Originally Posted by JimBuchanan View Post
    The automotive poly V belts are designed to be used with grooved pulleys. If they can provide increased traction with less sideways load on a 9A spindle, why wouldn't that be a good thing?
    You have little to lose, the only question is whether you gain enough to justify the mix of cost/time/effort you put into achieving it. In the automotive application, they have to work under a considerable range of conditions, constantly changing rpms, varying loads, multiple loads driven off same belt, lesser circumference of engagement spread across multiple pulleys and angles, doubling back around tensioners, sudden extreme changes in loads (like an A/C compressor clutch cycling in/ out), for a lot of operating hours, -20F to +100F.... etc; 'Duty' on an SB9 in workshop usage is probably like an endless vacation.

  20. #59
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    ^^^ for the most part agree with the above.
    at some point it's like putting racing slicks on a smart car, it not gonna help and may even be harmful as belt slippage can save your butt sometimes, so I would not wish to eliminate it entirely.

    a case could be made for using a grooved pulley on the motor but even that isn't a benefit I think that would be realized in this application.

    simply having a lip on the outer edges so the belt can't come off the motor pulley is plenty good,easy to make and let's you get on with using the lathe.

    I do applaud your efforts, good show.

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    I had a left over 3" chuck and spindle from a mini-lathe when I upgraded it to a 4" chuck, spindle and steel gears. After I traded up to this SB 9A, I thought it would be a good idea to be able to use that 3" for small ring adapters and such, so I had a 1 1/2 x 8 back plate for a 3" on my ebay watch list. When I remembered I still had the spindle, I immediately parted off the spindle from the mounting plate. Here are all the parts, with the finished back plate made from the spindle, a spacer parallel +/- about .00025", a paper washer that helps to unthread the chuck.
    20190716_103715.jpg
    Although the thread dial is not needed to thread 8 TPI using a 8 TPI lead screw, I had fun using it for the first time anyway. The thread stop clamp was useful however. I had to "pickup" the thread about 5 or 6 times, as the plate came loose from the chuck the first time and I did test fittings on the spindle. The large threads made it easier to align the trailing side of the cutter into the thread.
    20190716_120321.jpg
    Mounted to the spindle and seated perfectly to the register flange, with paper washer in between. I made the register bore 1.523" like most spindle accessories and there is maybe 1 or 2 thou radial/sideways play in the threads just before flange contact to allow concentric seating as explained in various threads here, namely "Machining A Chuck Adapter".
    20190716_154240.jpg
    Last edited by JimBuchanan; 07-16-2019 at 06:04 PM.


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