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14th Aug 2021, 08:20 AM #16Most Valued Member
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Thanks John. I’m guessing the gears are to compensate for the slight difference between metric leadscrew and imperial dial.
Ie 5mm is .1968” whereas the dial would be .200”
Steve.
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14th Aug 2021, 10:23 AM #17Philomath in training
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14th Aug 2021, 11:15 PM #18Most Valued Member
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I had a similar thought Michael.
I removed the countersunk screw from that piece but it doesn’t pop up or anything, and can’t turn it with my fingers.
Might have to remove the hand wheel to look inside…
Steve
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15th Aug 2021, 11:02 PM #19Most Valued Member
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I had another poke at the disc tonight and it came off. Must have initially just stuck on with old oil gum.
It’s just a disc - nothing else.
I pulled apart the compound hand wheel as it also has the dual scales, but looked easier to remove. Definitely looks like an internal ring gear, and that there’s meant to be a small gear in there as BaronJ described earlier.
One the “get it running” aspect, I opened the electrical panel.
Red anyone??
There’s a bit more happening in there than I expected.
For a start there’s 6 wires going to the motor…
Thankfully the wiring diagram was inside the enclosure.
It shows both star and delta connections to the motor, but the motor nameplate shows delta.
Not sure what that means yet.
It’s also 20hp - the largest motor option. I was hoping it would be 10 or 15hp. Will see how it goes on the 11kW 220-380v VFD with my single phase supply.
Steve
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16th Aug 2021, 04:14 AM #20
Hi Steve,
Thanks for the pictures, particularly the dial assembly !
I believe that the original gear was made of plastic and that both scale rings should move freely. Its quite probable that the scale ring seized and destroyed the gear. It seems to have been a common problem from what I recall. I think that the other hand wheel might be the same construction.
You may be able to reproduce a suitable gear with a 3D printer, that is assuming that you can get the right template file, though you might be able to get the size and profile data from the existing teeth.
As far as the motor size is concerned 20 Hp isn’t the biggest one that they used. I think the one on my friends DSG is 30 Hp. It should Have been a Brooks Huddersfield made motor, though they did use other manufacturers motors, I've not seen an "EE" one. Red wiring seems to be the standard on DSG machines, the ones that I've played with use red for everything.Best Regards:
Baron J.
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16th Aug 2021, 08:11 AM #21Philomath in training
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Start/ delta connections on large motors are one of the things that are done to limit starting current. Starts in delta and then switches to star at some pre-determined time I think. 6 wires because the connections that normally happen inside the motor terminal box now happen externally. Adam may be able to say more.
If you want me to, I should be able to cut you a little brass gear (or plastic if you prefer) to replace the missing one if you can work out the size.
Michael
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16th Aug 2021, 08:12 AM #22I break stuff...
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Star/Delta start, most likely.
Diagram on this page (on the left) is the same diagram, just slightly differently laid out:
https://theengineeringmindset.com/star-delta-startes/
Pretty common for bigger motors to use this method to reduce startup current. There are a couple of other methods like autotransformer start and resistor start, not sure if they were used on something as small as your tiny 20hp motor .
*EDIT* Michael beat me.
All obsolete now thanks to VFDs. Just means there are more contactors you can ignore!
So given the 5hp Graziano can do 0.25" DOC (just) I expect to see a 1" cut when you get this thing running. Don't want to hear any excuses about extra rotating mass sucking up the extra power or any of that nonsense...
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16th Aug 2021, 10:59 AM #23Most Valued Member
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Thanks guys. Star-delta start sounds familiar and would make sense. There's a separate MTE control systems booklet with the wiring diagrams, so I expect that's tied up with it.
The 6 motor wires are all nicely terminated on the rail, so should just be a case of connecting the windings appropriately in delta, and hooking up the 3 phases from the VFD.
I haven't got far enough into it yet to decide whether I'll use the existing control contactors to signal the VFD, or just use the switches directly, but will get the motor running directly from the VFD for a start.
There's a spindle brake involved which seems to have wiring associated, but could just be a microswitch for an indicator light. Hopefully not a solenoid operated clutch like on my TOS mill.
John - my comment about the 20hp motor being the largest they used was in relation to this model (from the note on the wiring diagram that shows 10/15/20hp as the options). I'm guessing your friend's lathe is a larger swing model than this - maybe a 24 or 31"?
As you suggest, it looks like both dials should be free to rotate, but none of the metric ones will move. I had to give the compound metric dial a tap with a copper hammer to free it from the inner part as it was gummed up with old oil and gunk.
I still haven't figured out exactly how they work, but hoping its just a simple gear that connect the 2 dials together and the dials have the different tooth count to give the slight differential movement between them. The locking knob probably just handles the dial connection to the leadscrew to allow zeroing.
They are very fine teeth - think I'd be suss about 3d printing being strong enough to last long term, but it would definitely be an easy way to test.
Michael - thanks for the offer to cut some gears. I'll let you know if I need to take you up on it.
J&H - I reckon I could get to the full 20hp - just need to suck all the 64A out of Powercor, and pick a cool day/clear in the middle of summer when I'm getting the full 5kW out of the solar
Steve
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16th Aug 2021, 12:23 PM #24Most Valued Member
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I found the video on that page explaining the star/delta starting was great. Brief, but comprehensive and easy to understand.
I probably learned that stuff 35 years ago, but too many late nights and alcohol at the time (and not using the info since then) have dulled my memory
Steve
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16th Aug 2021, 02:47 PM #25Most Valued Member
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Finally found a video online that shows the dual dials in use. Looks like both dials do turn at the same time.
Go to 33s in the video https://www.youtube.com/watch?v=8vPTzVgTUsE to see the cross slide dials operating.
Steve
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16th Aug 2021, 09:55 PM #26Most Valued Member
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There’s a reasonable size bridge rectifier between the two transformers, possible that the wires going to the brake are for DC injection. Don’t really need DC for anything on a lathe. May also be completely unrelated.
With a machine that big I’d give serious consideration to having 3phase put on to the property. You’ll be seriously kneecapped without it.
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16th Aug 2021, 10:54 PM #27Most Valued Member
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Ive spoken to the power distributor here and unfortunately the nearest 3 phase supply is about 1km away. There’s both LV and HV about 50m from the shed, but both are only 2 phase.
There’s some development going on across the road which may change things, but the woman I spoke to only had visibility of the current infrastructure - not what was still in the planning/provisioning.
I’ll definitely contact them again in a few months.
The DC is definitely tied up with the (assuming spindle) brake
Steve
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20th Aug 2021, 03:07 AM #28
I found this video mate https://www.youtube.com/watch?v=cgctavCrv34
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20th Aug 2021, 10:09 AM #29Most Valued Member
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The dual dials should indeed both rotate all the time. I will say that the dual dials add quite a bit of resistance and makes the cross slide feel a bit average so id probably leave the gear out and put a DRO on.
Admittedly the ones on my smart and brown are still there and functional so I have left them.
Sent from my SM-G973F using Tapatalk
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20th Aug 2021, 10:59 AM #30Most Valued Member
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Adventures with a jolly green giant
Thanks!
Did you notice that the only dial on that lathe that's working correctly is the saddle! The cross slide and compound metric dials don't move.
Power feed on the compound was a surprise - will have to check that out on mine, but don't think it has it.
Caskwarrior - I wouldn't have thought they would make much of a difference to the feel if everything in the dials was clean and working properly.
Interesting if the reality is otherwise.
Its only a very minor ratio change - 125/127 teeth, so near as dammit the dials are direct coupled. Definitely some close fits though and a lot of surface area inside the dials, so probably wouldn't take much crap buildup to start to bind things up.
Here's a shot of the inside of the saddle dials. Just a larger version of the cross-slide one.
Also one of the locking arrangement for zeroing the dials.
A tapered thumb screw in the end of the shaft pushes some pins out to grip on the inside of the imperial dial bore.
Steve
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