Mini Lathe Speed Reduction.......

[Stilldrillin]

Early on, last year. I replaced the motor and pc board on my Real Bull mini lathe........         http://madmodder.net/index.php?topic=4962.0

As it was all done in a  bit of a rush at the time. I now intend to finish the job, properly.
Including reducing the belt ratio, as posted by Loply, around ½ way down the page.......   http://madmodder.net/index.php?topic=4946.0

This motor/ board set up is a lot more lively than the old one. Giving less torque, and 1,287/ 2,920 rpm, instead of the promised 1,100/ 2,500.
So, first I need to slow it down to spec'.

This is my board. MAX, MIN, IR, CL .......





Also, ACCEL.........




Do I switch on, and reduce revs to 1100, using the MAX pot?

I've heard mention of higher torque, through twiddling........

What can I achieve, and how, with the other pots?

Or, should I leave well alone??

David D

[John Rudd]

David,

If in doubt dont do it...As my dad would say....

Can you afford to lose another board?

I'd say that to gain more torque at lower speed, you need to do it mechanically(keep the motor running high and reduce the speed thru a cog box)...The current setup isnt capable of more torque at lower speed..besides running the motor at lower speeds for more torque will cause the motor to overheat (poor cooling....)

[andyf]

David,

When all else fails, read the instructions... I think you know where to find them. You should be able to rein back the speed with the MAX trimpot, though it does look as though it interacts a bit with the MIN, so a bit of toing and froing might be needed.

I'd hazard a guess that the IL trimpot might raise the limit of the current which the board supplies to the motor, thereby increasing the torque. Instructions on p19 of the online manual. But get a second opinion from Dave BC or someone else who knows what he is talking about before you twiddle.

Looking back at your "It doesn't work any more!" thread, I see that it concluded with the news  that Dave had repaired your old board, so I suppose the last resort is to put it back in, unless he is holding it to ransom.

Andy

[Troutsqueezer]

Speaking as an EE (my day job) I would recommend leaving well enough alone unless you have a thorough understanding of the safe operating areas (how they are biased and where along the load line they are operating) of all components involved and maybe an understanding of phase angles...well, you get the point. There is much to consider when making adjustments to circuitry of this nature, things that unless you designed the circuit, you have no way of knowing. Maybe you can tweak the pots and everything will be ok, and...maybe not.

[Stilldrillin]

John, Andy, Dennis.
Thanks for your comments, and cautions, which I have taken on board...... 

Andy, the only online instruction manual I can find is this one....   http://www.kbelectronics.com/manuals/kbic_manual.pdf     Section 7 deals with twiddling.

Is this the manual you are referring to? 

The old, repaired board, is still residing with Dave. We'll meet up, sometime. No ransom has been mentioned, as yet! 

David D

[andyf]

That's the one, David.

Andy

[Lew_Merrick_PE]

This pending project is relatively far down the priorities list, but I will be moving the motor on my MiniLathe out from under the base casting so it can have multiple pulley ratios going into a (to be added) jackshaft that will sit in the (to be vacated) volume.  The advantage of this (from my knothole) is that I can get better torque at lower speed ratios and free up the area occluded by the motor cover today (which I will need for my taper turning attachment).  My plan at this point (and subject to change without notice) is to mount the motor on a 2- or 3-position lateral slide that mounts to a (belt-tension-wise) second slide that will use a cam to maintain belt tension.  That way I can loosen the cam, move the motor to the proper belt alignment position, and re-tighten the belt (fairly) quickly.  There will need to be some tin-bashing to make a cover that keeps the swarf out of the drive, but a pivot/hinge and pivot-hook snap latch should take care of that...

[loply]

This pending project is relatively far down the priorities list, but I will be moving the motor on my MiniLathe out from under the base casting so it can have multiple pulley ratios going into a (to be added) jackshaft that will sit in the (to be vacated) volume.  The advantage of this (from my knothole) is that I can get better torque at lower speed ratios and free up the area occluded by the motor cover today (which I will need for my taper turning attachment).  My plan at this point (and subject to change without notice) is to mount the motor on a 2- or 3-position lateral slide that mounts to a (belt-tension-wise) second slide that will use a cam to maintain belt tension.  That way I can loosen the cam, move the motor to the proper belt alignment position, and re-tighten the belt (fairly) quickly.  There will need to be some tin-bashing to make a cover that keeps the swarf out of the drive, but a pivot/hinge and pivot-hook snap latch should take care of that...

Lew, not only can moving the motor accomplish this, but here's an experiment for you to try.

Take off the head of the lathe and remove the motor. Observe that the head is bolted to a piece of the lathe bed which is supported at the front of the lathe, but that the corner of the bed furthest from the operator at the left end of the lathe is just floating with nothing supporting it. Pop a dial indicator stand on the bed and put the needle in this corner and push down with your thumb.

It will deflect by a very surprising amount. 10/15mm thick floating cast iron sheet is not very rigid when it's not supported at all.

Moving the motor will allow you to put a "support" in there and will stop the entire flippin' head from rocking and rolling when under pressure.

[Stilldrillin]

I had a gentle tweak at the control board, the other day.

A very small movement on MAX, reduced the revs to "correct". But, this then caused very slight creep when control pot was turned to zero.
A slight movement on MIN solved the creep, but the top revs increased slightly.

As I often use a 5" chuck, I turned the ACCEL to give 3secs acceleration time. This then disturbed the other two settings..... Again!

Finally, (after 5 mins), all was balanced satisfactorily.

Today, I made the two motor mounting washers, to work with the cradle. Hopefully this will give a more rigid motor location.




Also, I started on turning the pulleys to fit.......

After the speed/ acceleration alterations, the lathe performed perfectly. 

David D

[andyf]

Hi David,

Glad the tweaks to the pots have got the speed to behave properly.

There's a plan of a jackshaft speed reducer here, though it is single speed:
 http://www.toolsandmods.com/library/ralph_patterson_speed_reducer_2.pdf

I think you are in the Yahoo 7x12 minilathe group; at least, a couple of messages from a Stilldrillin (but with a surname which doesn't begin with D) recently popped up for moderation, because you/he's a new member. In the Photos section, there's an album called "Belt Drive" showing a multi-speed reducer, though it seems to involve two jackshafts.

Andy

[Stilldrillin]

Hi Andy. Thank you!

Those two seem very purposeful. Though I wonder just how much torque the gearing can stand. 

Yes that is me, on 7 x 12. Still rather smockravelled with the email only format. Not quite as homely as on here....... 

David D

[andyf]

Hi Andy. Thank you!

Those two seem very purposeful. Though I wonder just how much torque the gearing can stand. 
Yes that is me, on 7 x 12. Still rather smockravelled with the email only format. Not quite as homely as on here....... 
David D

As to the gearing, not a huge amount of torque, I imagine. From reports on the 7x12 group, the plastic gears within the headstock seem to be those which most frequently lose a tooth. And the headstock end of the bed is cut away to accommodate the motor so much that it might flex a bit with supertorque, as Fergus said. See two of the pictures on this page, which show the Real Bull variety, but Siegs are the same. http://www.toolsandmods.com/mini-lathe-bed.html

Yes, the 7x12 Group is a bit clunky, like all Yahoo groups. Threads on it aren't neatly arranged, as they are here. The format dates from years back. You can post via email, but it's easier to do it by visiting the group. It started as a spinoff from the 7x10 group when that degenerated into political ranting, so is fairly tightly moderated by John "Gadgetbuilder", Trevor Rymell and me to make sure it doesn't go the same way.  Don't really know why I'm a mod, having never owned a Seig or RB lathe.

Andy

[Stilldrillin]

 And the headstock end of the bed is cut away to accommodate the motor so much that it might flex a bit with supertorque, as Fergus said. See two of the pictures on this page, which show the Real Bull variety, but Siegs are the same.

Andy

Andy.
Where's this cutaway? 

This is my Real Bull, during a stripdown, some time ago........




Same thickness of bed, all the way through. Full, four bolt fixing.

David D

[andyf]

Sorry, David; I omitted the link from my last post, but have now rectified that. "Cut away" was not the best way of putting it, but I was referring to how the rear vertical side of the bed stops short and doesn't afford any reinforcement to the top of the bed under one side of the headstock - see the last pic on that page.

Andy

[John Swift]

Hi Dave

I guess this picture shows the cutaway

without it ,you need extra metalwork to attach the motor

(not what the exra bean counters want when the are keeping the cost down )


   John

PS       the motor  mounting in the Ralf Patterson speed reducer has given me ideas

[Stilldrillin]

Andy, John. Thank you! 

I realise there's a little less metal, in a Sieg version.......

I wondered if the deck was cut away, under the headstock. Or summat!   

David D

[Bluechip]

Hi Dave

I KNEW you'd fix the speed wotsit ..

I had every confidence..

What happened to the squeak BTW ??

Or are you looking for a pip to go with it ?? 

After last nights curry I've got some bubbles if you want some ... 

I'm off .... not before time etc etc

BC
 

[Stilldrillin]

Hi Dave.
Thanks for your confidence, in my confidence. 

Squeak's still there, as it has been since new. No sign of Wilfred, or Pip...... 

Will post the build/ mods, as they happen. Don't hold yer breath. I'm hoping I can grab a whole hour in there this aft...... 

David D

[Stilldrillin]

Dave BC.
I was fiddling with the new pulleys, this aft. Realised I could do a vid, or two...... 

But, I couldn't make it squeak on camera, for you! 

But, here's a vid of the quiet end.........

[ Invalid YouTube link ]


The other end isn't as exciting, but it's a lot noisier......

[ Invalid YouTube link ]


I still think the commutator needs a gentle skim.......

David D

[Bluechip]

Dunno Dave, does sound a bit ratchetty ...but ....

If I turn the one on my WM16 mill right down it cogs ... and I expect it to really.

With these controllers you are only putting a bit of a pulse through the motor 100 times a second.
So the motor is going to give a lot of little kicks rather than a continous s-m-o-o-t-h rotation.

On my mill it rattles the gears horribly, but if I put some drag on the spindle, it don't, 'cos I have taken the backlash out of it.

I wonder what that motor would sound like using my Variac with a bridge rectifier  ???

When the controller went dud on the WM16 I ran using the variac/rectifier for months 'cos I was too idle to fix the Controller Board and it ran a whole lot better. And faster ...  the motor was getting a fair bit more than it's usual 180V ration ...

It may be that the commutator is a bit gruesome. but I would not have thought so, the motor ain't all that old is it?

No harm in having a shufti, make sure the brushes are free too, they can give all sorts of aggro ...
BTW what's all that black stuff? Belt crud??

I'll wind your spare board up with the Warco motor and see what that's like ...

IIRC it doesn't make too much noise.

Hmmmmm hard to tell at this distance ...

BC



 

[Stilldrillin]

Over seven years of belt crud........ Less, a rub with a rag! 

David D

[Stilldrillin]

I finally got some meaningful workshop time, these past few days.

Modded the 12 tooth motor pulley, by boring to suit, and sleeving the boss o/d, to take an M3 grubscrew.

Needs a tidy up, and a shorter screw, but you get the gist of it........




Removed the flanges from the driven pulley. Faced, bored 10mm, and roughed the keyway......




Then turned away the large boss. The lathe was pulling like a train! Who needs speed reduction?




Filed the keyway. Installed nicely, inside the new recess in the bearing spacer......




Tried the new cradle mounting idea, on the old motor........




Time to remove the motor to swap pulleys, and cradle.

Ah! Whaat! 

Perhaps this is why the motor's a bit noisy......... 




Bugga!!!!!!!!



The new(ish) motor is 11mm longer in the plastic brush housing end.

I knew it was a neat fit inside the bed casting. But not to cause damage.....




No problem! I'll just swap ends!

No I won't! Not compatible, at all......... 





BUT...... That wasn't the end of it!

As Dave BC had fixed the blown board. Bless Him! 
There must be nothing wrong with the old motor, except the cracked fan blade. 

This will suffice, until I can get the broken motor replaced.

Swapped to the old motor.

Switched on. With speed controll set at zero.


It took off at full revs, then stopped with a POP!!! 

We've been here before, haven't we............. 

Walked out. Locked up. Went and had me tea. And a real good good sulk........ 

Sigh.........

David D

[Bluechip]

        

Strewth. It is a bit moth eaten isn't it ???

Commutator looks none too healthy anyway. All that black ... er... whatever it is ... doesn't  seem right.

The old motor looks better, just a dark smear where the brushes bear on the copper is about normal.

Oh dear ...

Oh dear, Oh dear Oh dear ...

BC

 

[lordedmond]

Dave I have to agree completely with dave BC on the condition of the comms the old first duff one looks just about perfect but the new duff one is well ugly not fit for man or beast.

but it could be many things bad neutral or wrong grade of brush , we used to aim for a nice shiny chocolate colour, it also relates to the load on the motor



Stuart

[Stilldrillin]

Well..... Finally got this job sewn up! (All bein' well)....... 

Dave Bluechip called this morning, with some test equipment, and also returned my original, repaired board.
There's nowt wrong with either motor. Electrically.......... Which was a bit of a surprise! 

Therefore the intermittent fault must lie inside the 8yr old control box. Fortunately, I bought one from Amadeal a few days back!

It's a bit larger than the original Chester box........




So, two more M5 mounting holes were drilled, higher up the casting........




Nice new 400w motor, from Chester........




Getting to be a bit of a mongrel, now.........




I ran the motor for a few minutes, to bed in a little, then checked rpm. Low gear, 800rpm. High gear 1800rpm. That'll do for me!

Only had time to face a piece of 1" steel. It performed beautifully! When really heavily loaded, it just 'dug in', and kept going!   

Rather pleased! Thanks everyone for your input....... Especially, Mr. BC! 

David D