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Doc Nickel
08-24-2009, 10:10 PM
Right now, my Logan 11"x32" (model 950?) is set up for a top spindle speed of right at 600rpm. As I mainly deal in small aluminum pieces (and have another lathe to boot) I'd like to bump up the max by at least half again, to around 900 to 1,000 rpm. Unless I'm mistaken, I should just need a motor pulley about half-again larger. It's 2-1/2" now, and the next common size in that range is 3-1/2".

Now, the question is, will I be hurting anything at that kind of increased speed? The headstock has roller bearings (or ball, I'm not sure- but it's not plain bearing, anyway.) Now that I think about it, I'm going to have to check the jackshaft bearings- those might be plain. (If so, I haven't lubed 'em in a while. :D )

I was wanting to double the speed, to closer to 1,200 rpm, but I thought that might be pushing it.

Doc.

Don Young
08-24-2009, 10:20 PM
I can't give you a specific answer but 1200 RPM does not seem out of line for a lathe of that size, especially with ball or roller bearings. Be sure everything is well oiled and watch for any signs of bearing overheating. If the bearings run only slightly warm you should be fine. Watch for unbalance and vibration.

Don Young

rkepler
08-24-2009, 10:45 PM
I would expect that 1000 would be fine, maybe even 1200 or more. You might just give Scott Logan a call and check - http://www.loganact.com/

J Tiers
08-24-2009, 11:25 PM
The 11" must be quite different to the 10".

My 10" has a top speed of 1400 rpm +-. I would suppose that the 11" would have had a similar top speed, they are very similar, same bed, just a taller headstock with a somewhat larger spindle and ball bearings.

If you don't have the manual, do get one. I believe Scott does ship to foreign countries (Aren't you in Alaska? Or is that the other "doc" who is?)

atty
08-25-2009, 12:04 AM
Been running my 912 with a DC motor for over a year now. I rarely exceed 800 to 1000, but have done so....up to 2500 with no problems. As Don said, make sure your lube is up to date. Keep your eyes and ears open, just in case.

Doc Nickel
08-25-2009, 12:30 AM
The 11" must be quite different to the 10".

-Not necessarily. This particular machine started out as a turret lathe, and clearly saw quite a bit of factory use, considering the dings speckled all over the 6-jaw and the first 2" of bedways. It's possible they specified a lower spindle range.

Besides that, the fellow who had this before me, as I recall, bought it from an eBay auction, had it shipped up, and then had to do quite a bit of work to it- spindle bearings, among others. He either replaced the motor, or installed a new one- either way, when I got it, it had a new Marathon 1HP motor and a typical cast hardware store pulley. (Which I later replaced first with a 1.5Hp single phase, and then a 2HP 3Ph and VFD.)

It's entirely possible he inadvertently or intentionally slowed it down- now that I think about it, if the original motor was a 3450, with the existing drive setup, it would have a 1,200 rpm top speed, wouldn't it... ?

I hadn't thought about that- I even have a TEFC 2HP 3Ph 3450 that's begging for a new home... Weird how blindered one can get when planning out a project. I never put those two thoughts together 'til just now. :D

For those of you with Logans, especially the underdrive-cabinet style, does yours have a 1725 or 3450 rpm motor?

Oh, and the jackshaft has sealed roller bearings (unlike my Sheldon which has mostly bushings.) Presumably they'd be okay with a doubling of the shaft speed. (Which given the pulley sizes is probably 1/3rd to 1/4 the motor shaft speed.)

Doc.

rantbot
08-25-2009, 12:45 AM
Factory spec for the 11" Logan was 1500 RPM top speed, with a 1/2HP 1750 RPM motor.

At least, so says a 1949 Logan catalog.

CountZero
08-25-2009, 01:48 AM
Just a thought,

Since you have a VFD, why not use that to increase spindle speed a bit?

atty
08-25-2009, 02:27 AM
My 11" 912 came with a monster Century induction motor 1/3 HP, 1460 rpm, although it looks as big as today's 1 1/2 HP. No doubt not factory. The current DC motor, 3HP Baldor is 3200 rpm.

The last time I did a speed check, the strobe aimed at the chuck said 2556, and I had more potentiometer left on the controller, but unlike my teenage years, that was quite fast enough, thank you. :eek:

Bmyers
08-25-2009, 06:22 AM
I dont want to hijack this thread, but I am new to Logan Lathes. How do you switch the belt between the two motor pulleys on the 10" machines ? Does it take brute strength to lift the drive assembly and move the belt ?

Doc Nickel
08-25-2009, 07:02 AM
I dont want to hijack this thread, but I am new to Logan Lathes. How do you switch the belt between the two motor pulleys on the 10" machines ? Does it take brute strength to lift the drive assembly and move the belt ?

-On mine, the motor-to-jackshaft distance is set by a threaded rod. No "quick change", in other words. Also, as above, mine has a nonstock motor and decidedly aftermarket motor pulley- in order to change to the "low speed" jackshaft pulley, I'd literally have to move the pulley on the motor shaft, and install a different diameter belt.

I'm not sure how the factory did it on my version of the underdrive- which is different than all the versions shown on lathes.co.uk.

I'd say use the back gear for occasional low-speed use, and only bother with the pulley change if you'll be doing a great deal of low-speed work.


Since you have a VFD, why not use that to increase spindle speed a bit?

-That's fine for occasional use, but I'm told it's not something you want to do on a regular and frequent basis, due to motor heat issues, as I recall. And as I said, I mainly do small aluminum pieces on this machine- I rarely used any low speeds before, and since getting the Sheldon (which had a VFD before the Logan) I haven't used anything at all except top gear. If it just takes a $15 pulley to make the speed change, that's better all around than overspeeding the motor on a regular basis.


The last time I did a speed check, the strobe aimed at the chuck said 2556, and I had more potentiometer left on the controller[.]

-That might be getting a little carried away. :D But it sounds like I wouldn't have any real problem with bumping top speed up to even 1200 or so...

Doc.

J Tiers
08-25-2009, 08:47 AM
My Logan has a Southbend countershaft instead of the cumbersome drive box. My father-in-law had a Logan with the whole setup.

With the drive box, lifting the cover slacks the belt. You can then move flat belts easily from pulley to pulley.

The speed range selection of high or low comes from moving the belt on the motor pulleys. The large pulley is flat, the motor pulley V. if you slip the belt off the flat, you can change V pulley settings pretty easily.

Underdrive units have a different system of belt slacking or in some cases variable speed pulleys.

Speed changes are easy enough with my setup, slightly more of a pain if you have the silly 'drive box". You will want to be able to change speeds, I change between the 3 "easy" speeds all the time. Only more rarely do I switch into the high speed range.