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Jack shaft overheats.

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mjhenks

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#1
I rebuilt my LOGAN 400 a few years back. I also built a variable frequency drive and installed that at the same time.

The jack shaft Has new bronze bushings and I made a new SS shaft for it to overhang farther for the larger Baldor 3PH motor.

The jackshaft assy runs smokin hot. It overheats is 5 min at moderate speed. I have oiled it and the belt tension is not high. Not totally sure why right now. Fits on the bushings seem fine and it turns freely until it overheats.

Has anyone ever installed ball bearings in their jackshaft? Looking for a solution or understanding on why.

4ab3c18c4a077528cca1a706e8115e35.jpg

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tq60

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#2
First guess is the moment is too large.

The length of unsupported shaft caused much pressure on the bearing and it is possible that the pressure causes the oil to be pushed out of the way like a wiper due to the pressure.

A ball bearing would help but moving motor so pulley is in correct place would be better.

To test loosen tension so it just barely holds and see if it running this way runs any cooler.

Which bushings are getting hot?

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mjhenks

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#3
I tried to keep it as short as possible so totally understand your point. Will test with almost not belt tension. Darn 3PH motors are way bigger than original.

Both bushings get hot at about the same rate.


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Old junk

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#4
Agree with above Belt is out too far
 

tq60

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#5
Agree with above Belt is out too far
If both are getting hot then something is not right.

"New" bushings.

What you mean "new"?

Original replacement parts or Something made or general replacement type thing?

If the bushing is not an oil impregnated type then it needs to retain a film to work.

That means a somewhat critical sizing that depends on the lubricant type.

You could consider honing out a bushing to allow a bit of oil to form a film.

Another trick is to place o - rings on the bare shaft against the bushing to retain the oil a bit.

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mjhenks

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#6
New meaning oil lite bearings from McMaster Carr with the right OD but were bored for the ID. Fit i do not recall exactly but was with-in .0005" if the shaft OD. I have oiled the bearings anyways to see if that would help. The bearing visually takes the oil in from the top original oil holes and the oil can be seen exiting the bearing after a while.

I am going to do some testing to confirm it is just the shaft overhang and will report back. If it is that then i will be in a pickle on how to fix it and retain the lever arm to switch pulley's in the head stock.
 

projectnut

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#7
I would agree with tq60 that the shaft needs to be supported closer to the motor. I would also bet the rpm is too high for the bronze bearings. I have a similar setup on an old Seneca Falls machine with a 1750 rpm motor and an almost 12 to1 reduction between the motor and the jackshaft. In this case the maximum spindle speed is about 650 rpm. There has never been a problem with the jackshaft bushings overheating.

I also have a Sheldon machine that uses a jack shaft setup. This setup uses pillow block ball bearings. Also there's very little distance between the driven pulley and the bearing. I can run the spindle speed on this machine up to 2,200 rpm without problems.

Sheldon Jackshaft assembly.

IMG_0378.JPG

Seneca Falls jackshaft assembly.

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.
 

dlane

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#8
Can you turn the motor around and move the pulley next to the bearing, may have to make traveling motor mount
Motor should be reversible. Didn’t see any oil cups or on bearing bosses may be a good idea to add a couple .
Just a thought
 

Nogoingback

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#9
The other thing I just noticed is your motor and jack shaft pulley ratios.
On small Logans the shaft pulley is LARGER than the motor pulley. It looks to me as though the shaft is
turning much to fast and you're compensating with the VFD.


218136-bb6c3ca34c42d5c7d3671e3231ee6821.jpg

Here's the pulley setup on a Model 200.


DSCF7316.jpg

Here's a pic of a Model 400 I just found online:

27701-B.jpg
 
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Silverbullet

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#10
You know the saying speed kills. Also I know they say you don't need to but did you drill a hole thru the bushing so oil gets to the shaft? I agree your pulley system is over speeding the lathe itself. It's old not a 2,000 rpm machine. Just guessing if your motor is 1750 your pushing the Jack over 2,750 to 3,500 rpms. Melting the bushing quickly
 

mjhenks

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#11
Thinking over the speed thing.

I found a larger pulley that would slow down the jackshaft speed. Need to get a belt.

I did check out the tension on the original belt and I probably had 1” or so of easy play on each side of the belt. Not a lot of tension. In fact when the VFD break engages the belts slipped.

If this does not work then I really struggle to see how to reconfigure the motor and keep the stock jackshaft arrangement with the belt tensioner/swapping system. I know I do not need that any more with the VFD. Wonder if Direct drive may be better but I fear loosing low end torque.

5ff1775dd739e4c6a1af632b9ea79067.jpg


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Nogoingback

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#12
I have a couple of questions:

How did you decide to fit a 3 HP motor? I would think a 1/2 HP motor would be about right. Do you have all the parts to return
the belts and tensioning system to stock, or would you have to buy parts? That pulley looks like the original Logan part: If nothing
else, you can use it and just get a new belt. Belts are easy.

Your VFD doesn't have enough speed range to replace the pulley system.
 
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f350ca

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#13
Fit i do not recall exactly but was with-in .0005" if the shaft OD.
Your bearing fit might be too tight. As the shaft warms up your clearance goes to zero. With oil I'd go .001 to .0015 clearance, for grease you need at least .005 or you can't pump it into the space.

Greg
 

mjhenks

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#14
Nogoingback. 3HP because it became available. I made two VFD at the same time. One for my mill and one for the lather. I found the motor used and since i was working on the mill way before the lather i just grabbed both as they were priced to move. I do have all the parts to return to stock somewhere... I have not given up on this yet thought...

Greg. You may be right. I foresee the system coming apart soon and i will re-check things.

Here is my plan of action.

- first get a belt for the larger pulley. That will drop by shaft RPM's. See what happens. I suspect i will still run hot.
- Since i do not see a way to shift the motor over so the overhang is less i will look at making a support bearing and place it just inside the pulley. Attaching it to the motor mount to take the moment load from the belt.
- If i am still experiencing issues then i will look to switch to ball bearings. I think there is enough material to get bearings in there. Shaft is 3/4". I should be able to get a 1" OD bearing set in there with material left. Maybe even a little bigger but not much. Not as large as i would like but not alot of casting there to work with.

I am having fun but man i wish Grandpa bought a 9B or a 200 back in the day. The 200 probably would not have fit in my garage but the 9B would have saved me all the upgrades i have done to this little 400. :)
 

Richard White (richardsrelics)

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#15
I had the same issue, I swapped out my yoke for one with Gitz oil cups and bronze bushings. Of which my original had neither. No longer an issue
 

Nogoingback

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#16
I think your plan is a good one. The pulley change should help with the bushings, as well as bringing your spindle RPM's down into
the design range. Instead of making up a bearing support, how about switching out the 3 HP motor for a 1/2 HP that will fit in the
space a bit better? A 3 HP Baldor is worth enough, I would think you could sell it and buy a smaller motor without spending more in
the end. Then you could locate the pulley next to the support bracket and eliminate the overhang on the shaft.

Richard's suggestion on oil cups is a good one. You could also just drill a couple of holes down from the top and drip some oil in every time
you use the lathe. The jackshaft on my Atlas 618 is like that.

As for the upgrades, all these old lathes seem to require work. Once you get it sorted, it will be worth it. :)
 

Silverbullet

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#17
I would bet the tension with all that overhang was much more then you think that shaft will flex ,,, bend ,,, easily with barely any real tension. I'd bet money on that. If you mount an indicator on top near the end and put your tension on the belt it will bend down an125 thou. It's hard to realise but no support near the end is part of the problem. You could add a frame with ball bearing carriers fairly easy and about $50 in cost.
 

wa5cab

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#18
I agree that 0.0005" clearance is much too tight even if the shafter weren't bending. And that this is aggravated by the shaft bending a lot so that it is jammed in the hole at an angle and has zero clearance. And that with a 3 HP motor, sooner or later you are going to seriously break something.
 

tq60

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#19
3 hp with proper vfd should have great torque Down in low rpm range so consider keeping it.

Another option is to add another mid shaft to both offset the alignment(motor under bench) then you also can reduce speed by offsetting pulley sizes.

Flip motor 180 degrees then have output pulley in correct place.

The motor and new shaft are mounted under the bench out of the way.



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mjhenks

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#20
An update.

First some info.

The motor i have is a 2HP Baldor Motor. Model CM3558. 13.23" long. I would need to reduce that OAL by 3-4" to shorten the assy back to what the old Dayton motor was.
http://www.baldor.com/catalog/CM3558

I cannot easily run the motor from below the lathe and turning it around to stick the motor pulley in the middle of the jackshaft would not work either as the belt angles are wrong.

Direct drive to the head stock is interesting but this motor would still not work. It is too long since my lathe is tucked into a very particular corner of my much too small garage. (I know... no one has a garage big enough...)

Seems like i am officially looking for a new motor now...

Pulled it all apart last night and something went very wrong. I will place my bets for the initial problem being the bushings were too tight which was compounded by running too fast. Anyways, things got nasty and both the shaft and the bushings are shot.

IMG_3060.JPG

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IMG_3066.JPG

So where do i go from here.

I located an alternate 3PH Baldor motor (3/4HP, 4 pole, 230VAC) that would fit but it is only face mount. (10.25" long) I have located a few with side mounts that are in the 11.5" range that would work with a external bearing support.

As far as external support my thought is to come off the back side of the jackshaft structure but it is not the best surface. Doable but not going to be fun.

IMG_0896sm.jpg IMG_0733.JPG

Guidance and ideas are welcomed.

A few questions.

What is your guy's opinion on running bearings in the assy? I have a 3/4" shaft and could likely get 1" OD needle bearings in there. Note sure there is enough material for a 1-1/4" bearing.

What material would you suggest for the new jackshaft?

Thanks
 

Dave Smith

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#21
I've just read this thread on overheating and maybe can help others in diagnosing heat problems--in your case you could find out what specifically is causing the heat as it is warming up--HF has a hand held laser heat gun that will give instant heat settings on objects aimed at----it is on sale for about $14 now--I've had mine for approx. a year and amazed at all the uses for it---I have it with me in the car for finding overheating of wheel hubs, any engine accessory, trannys- rear ends-radiators-transfer cases-exhaust and intake manifolds-etc---I use it in my shop and home to find overheating breakers-wiring-plugs and wall receptacles- motors-bearings etc.--it makes quick accurate readings of close or far away objects and can help to predict potential problems-I think I will buy another one today so I will always have one within reach --Dave
 

f350ca

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#22
Needle bearings need a hardened shaft. Off the top of my head don't think they would be rated for the rpm your running even on a hardened shaft.

Greg
 

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#23
I think the best course of action is to return your machine to "stock" as Logan produced it. There's nothing wrong with the
design of these machines, and with proper pulley sizes, a shaft of the correct length and a suitable motor it should work
fine for you. Small Logans of this basic design have been producing good work since the early 1940's, so why re-invent the
wheel?
 

whitmore

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#24
Pulled it all apart last night and something went very wrong. I will place my bets for the initial problem being the bushings were too tight which was compounded by running too fast. Anyways, things got nasty and both the shaft and the bushings are shot.

...What material would you suggest for the new jackshaft?
I've never seen a jackshaft too rusty to work; mild steel, not SS, would be my preference. Heck, it's 3/4 inch
diameter, there's not a lot of material strength needed. SS has chromium oxide layer, it does NOT
make a good bearing material (CrO2 is abrasive).

2HP motor and higher speed than lube will handle, did score the shaft a bit. But, that's not fatal: you want
some (three mils?) diameter difference in shaft and journal, and you can turn that much off the scored shaft
just fine. It was too tight, after all. Then, lube with high viscosity oil (SAE 90 ?). The scoring on the
bushing hasn't removed enough metal to matter, and a smooth shaft will polish it back to round
in short order.

So, if 'twere my problem, I'd do a very light lathe cut over the scored shaft area (use carbide, there's probably some
workhard stuff there) and try to reuse the shaft. Even if you get a new shaft, consider using emery
on the affected area, and remounting temporarily the one you've got. After all, the new shaft will want new bushings, too,
there's really no loss if you mung the old ones while turning the new 'uns.

Heck, maybe just a few manual swipes with emery cloth, and some white-rouge polishing, can recondition the shaft.
 
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mjhenks

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#25
This may be a mistake but i am going to test out the direct drive option first. I of course have the motor and some aluminum laying around already so all it will cost me is my time and a new belt. I started last night cobbling together a 10" tall motor riser and will pull the head stock apart to install a shorter belt. Hope to have it put together some time next week.
 

mjhenks

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#26
Success.

Using some scrap aluminum i had laying around i bolted together a 9" tall riser for the 2HP motor. Ugly but it did the job

IMG_3569.JPG

I then played around with the step pulley combination and ended up settling for around 1300 RPM and locked the motor down to the bench. If i find this is not enough later i have at least two steps up i can go. Ran the lathe for about 30 minutes testing all sorts of frequencies and both directions and it seemed OK. I am happy with the results and will leave it this way until i find it is lacking in some way.

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IMG_3609.JPG

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Thank you for the help and guidance.

Four things left to do.

1. Finish wiring the RMP gauge. Should be done this weekend.
2. Make a debris shield for the motor. Should be done next week.
3. Locate a 9B for parts to harvest the power apron and install that. (Looking for 2 years now....)
4. Use the darn thing...

Matthew
 

Richard White (richardsrelics)

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#27
Very nice... I know I have issues with my original motor mount loosening up allowing the mounting plate to "rattle", making it a noisy lathe. I do not like that....
 

markba633csi

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#29
I saw that done on a South Bend 10K, the owner used direct drive with the motor on a platform like yours. He said it worked great for him.
mark
 
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