Logan 200 - Figuring this thing out!

[Laminar]

I don't think that I would eliminate the counter shaft. The original spindle RPM range is something like 179 to 1450 RPM. Which is more than the satisfactory speed range of a variable speed AC or DC motor. Plus Back Gear of course. At the lower RPM, the motor would over heat.

The original recommended motor HP was probably between 1/3 and 1/2 or 3/4 HP. 2 HP would as you mentioned be much to much.

wa5cab,
Thanks for your input. I'm sure there's a better solution than the 2HP motor that came with, I've spotted several treadmills locally for free. I may also reach out to a couple of vendors I work with. I know a three phase inverter-rated motor with even just 100:1 turndown can happily run at 1/100th of its base speed. So a 1750rpm motor can run at 17.5rpm all day. 1000:1 motors are also available that can turn 1.75rpm without overheating. Things can get pricey quickly, though.

 

[Aukai]

Your making some good progress

 

[Winegrower]

It’s amazing how many spare parts came in your collection. Clearly you know what you’re doing, so best wishes for a terrific resurrection!

 

[Laminar]

The longer cross slide with the slot in it is for use with a taper attachment. It replaces both the standard cross slide and the chip guard. The compound assemblies should be interchangeable between the two types of cross slides

Here it is! Very cool stuff.

 

[MikeInOr]

Any thoughts on maintaining the current lantern-style toolpost vs. converting to a quick change? I don't have anything for tooling so I have no sunk cost in either method yet.

I used the lantern style tool-post on my Craftsman 12" lathe for near 30 years and it always got the job done. When I upgraded to my South Bend 13" lathe the first thing I did was purchased a quick change tool post... and I will NEVER go back. Once you have everything running smooth and are happy with the lathe I would recommend the quick change. I think the lantern tool post will do everything you need while getting the lathe running and tuned though.

Taper attachment??? I am jealous!!!!

 

[Laminar]

wa5cab,
Thanks for your input. I'm sure there's a better solution than the 2HP motor that came with, I've spotted several treadmills locally for free. I may also reach out to a couple of vendors I work with. I know a three phase inverter-rated motor with even just 100:1 turndown can happily run at 1/100th of its base speed. So a 1750rpm motor can run at 17.5rpm all day. 1000:1 motors are also available that can turn 1.75rpm without overheating. Things can get pricey quickly, though.

I ran some numbers on this for fun. I built a little Excel sheet based on the reductions published in the manual. I can plug in a motor input speed, select my reductions, and it will spit out the resulting spindle speed.


Here it is with motor belt position 1, spindle belt position 3, and the back gear disabled, the result is 179 rpm just like the table shows:


Now if I eliminate the countershaft reduction by changing that value to 1:1, I can see how slow a variable speed motor would have to run to achieve the factory minimum speed of 30rpm.

So a motor speed of 340 rpm directly into the spindle using the reduction of the #3 spindle pulley position plus the back gear gets me 30rpm at the spindle output. That's roughly 20% of a 1750rpm rated speed motor, or 12Hz on a 60Hz motor. That's only a 5:1 turndown and very liveable for basically any inverter-rated AC motor.

But what about torque? The advantage of the big primary reduction is an increase in torque at the spindle. The specified 1/2HP motor, after all of the reduction, sees about a 58x increase in torque. If you eliminate the primary reduction, you only see an 11x increase in torque. So if you tried to drive the machine with a 0.5HP motor, you'd end up with way less torque at the chuck given the same spindle speed.

Upping to a 2.5HP motor would give you (essentially) the same torque at the chuck as the 0.5HP motor through the primary reduction.

But if you're tied to just the #3 spindle pulley position, then spinning at the rated motor speed of 1750rpm only gives you a max of 936rpm, far less than the factory max of 1450. But it's possible to run higher than the nameplate speed, and running that motor at 2700rpm would achieve the factory 1450rpm spindle speed.

Here's a motor that looks pretty decent:

https://www.automationdirect.com/adc/shopping/catalog/motors/ac_motors/general_purpose_and_inverter_rated/mtrp-002-3bd18

It's 2HP and will run from 176 to 2700rpm.

This is all just a thought exercise until I get a little further into the mechanicals, but it was fun nonetheless.

 

[T. J.]

It looks like you’ll have a very well equipped machine once you get it cleaned up. I’m jealous of your taper attachment

 

[Laminar]

Grabbed some hardware over lunch yesterday and tinkered for a couple of minutes last night. Replaced the bent front carriage gib screws with some allen head bolts, and got the "0964" 1/8" split pin to retain the compound base gib.

Here's how we sit right now:

Part LA-298 is the Woodruff key between the crossfeed screw and its handwheel. The Logan parts catalog says it's 3/16" x 3/8" long. That's not right! Even a 1/8" square key is too wide. A 5/16" to 7/16" shaft uses a 3/32" key as standard, which seems about right by my measurements. I'll need to find a 3/32" key somewhere and give it a shot.

I still need to find some 10W oil and some way grease.

I moved the LA-345 plunger out of the cone pulley assembly and engaged the back gear, that all seemed to work. The manual mentions that the plunger should be retained outward by a pawl that must be pressed to release it. I don't seem to have that function, so I'll have to dig a little deeper.

With the back gears disengaged and the plunger engaged, there is quite a bit of slop in the plunger, enough that I end up with noticeable backlash between the cone pulley assembly and the bull gear. Still more poking around to do!

 

[Nogoingback]

Mobil makes a product called Vactra #2 way oil that is very suitable for your lathe. It's available in gallon jugs.

There should be a pawl and a spring set into the slot on the bottom of the back gear plunger. If yours are missing,
Logan sells them. There is an adjustment procedure for setting up the back gears. Here's the link: http://lathe.com/ll-group-archive/logan_lathe_back_gears.html. It's a fiddly procedure, but it works. I used a screwdriver to roll the gears when I did mine.

Honestly, a 3/4 hp 3 phase motor with a vfd will do everything you need with this lathe. More power will just make the belts slip and these machines are happiest if you don't over do it on DOC anyway.
The speeds available would be suitable for anything you'll want to do. Redesigning the drive system would be a lot of work with pretty much nothing in return. Notice when the belt cover is raised, tension from the countershaft belts is removed which makes most belt changes
a very quick and easy procedure, and even changing the motor belt is quick.

 

[Laminar]

Mobil makes a product called Vactra #2 way oil that is very suitable for your lathe. It's available in gallon jugs.

I just found a vendor selling Vactra #2 and the Velocite spindle oil and bought some of each!

There should be a pawl and a spring set into the slot on the bottom of the back gear plunger. If yours are missing,
Logan sells them. There is an adjustment procedure for setting up the back gears. Here's the link: http://lathe.com/ll-group-archive/logan_lathe_back_gears.html. It's a fiddly procedure, but it works. I used a screwdriver to roll the gears when I did mine.

I'll check that out, thank you.

Honestly, a 3/4 hp 3 phase motor with a vfd will do everything you need with this lathe. More power will just make the belts slip.
The speeds available would be suitable for anything you'll want to do. Redesigning the drive system would be a lot of work with pretty much nothing in return. Notice when the belt cover is raised, tension from the countershaft belts is removed which makes most belt changes
a very quick and easy procedure, and even changing the motor belt is quick.

I think keeping things simple and close to original really seems to be the way to go here.