Logan 200 Custom Shop - My Modest Modifications

I haven't modified the lathe much. It seems to work pretty well as it is. I've found it worthwhile to fiddle slightly with the ball cranks, and replace the leather belt with something a bit less medieval.

Knuckle Busters

I find that I klunk my knuckles on the center screw or nut. By the time one acquires one of these oldies, they've been apart and together so many times that the weirdest nuts, washers, pins, etc. can be on there. I found it worthwhile to put a regular nut on the inboard side of the cranks, and a narrow jam nut on the outside. This gets the central obstruction as far as practical away from my knuckles. I was considering experimenting with an acorn nut on the outboard end, but the local hardware stores didn't have any in fine threads. Some NyLoc locking nuts are shaped much like acorn nuts, and might work well. The idea is to get corners and edges away from my poor fingers.

The slightly yellowish appearance of one of the nuts in the photo looks like a zinc chromate finish on the steel. Brass nuts look nice on machine tools, and are plenty strong enough, but the variety of shapes and sizes isn't as good in brass.

There is a clamping setscrew on the crank but it's useless to rely on it to keep the crank in place. Besides, it just diggers up the threads on the cross feed screw. Use the nut and jam nut on either side of the crank to hold it in place. Sock them down tight and they will hold it without any help from the setscrew.

Replacing the cow with rubber

The older Logans, like the 200, use a leather drive belt between the countershaft and the spindle. By 1953, all Logan flat-belt models had been replaced by V-belt equivalents. The most interesting thing about leather belts is that they work at all. Belts can be stitched together or glued, but then are a chore to put on a Logan as the spindle and countershaft have to be partially disassembled (unless of course they're glued or laced in situ - see pages 10 and 11 of the official Logan Lathe instructions). So alligator clips are used on the belt ends. These work but need a fancy crimper to put on. There is a type which can be put on with a hammer, but I haven't seen one of those. Rather than buy a crimper, a normal person would haul over to a belting supplier and have them make belts to the right length with the clips installed. Look in the Yellow Pages under "belting" (not under "belts" - listings there are for fashion accessories).

The trouble with the leather belts is that they stretch and slip. The belt on my 200 had stretched to the point that it had used up all the adjustment distance available. It would still work, but I didn't have enough left to adjust the countershaft so that the belt wouldn't fall off the pulleys at startup. Flat belts are traditionally used with crowned pulleys, and the crown, somewhat counter-intuitively, keeps the belt pretty well centered (not exactly centered - when running, the belt will sit a little bit to one side or the other of the peak of the crown). The centering action is very strong - it will work even if the belts are fairly slack. However, the physical processes involved are entirely different if the belt slips (as it will tend to do on startup). When slipping, the belt will immediately scoot to one side or the other of the pulley. If it happens to scoot the wrong way, it will fall off the pulley. A good hefty flange would keep the belt from falling off the pulley, but it would then be harder to move the belt between the pulleys for speed adjustment. The Logan drive box assembly has provision to adjust the countershaft alignment so as to encourage the belt to scoot the right way, and not fall off. That was the adjustability I didn't have with the stretched belt.
UPDATE - The LA-16, the early version of the Drive Box Assembly, had that adjustability. It may have been deleted on later machines. The parts seem to have been changed on the LA-16-2. I don't have a parts list for the LA-16-1, though I figure there must have been such a beast. But no matter, the rubber replacement for the leather belt will work just fine, whether or not the adjustments are present.
I had a new belt which I had had made about an inch shorter than the old (stretched) belt, but I must have over-tensioned it because the alligator clips pulled out of one end immediately. Rather than get another one, I decided to stop screwing around with these cow parts and switch to a modern endless rubber belt.

The most common endless rubber belt is the ubiquitous V-belt. There are several different section sizes available. However the clearance in the Logan headstock is tight, so a thinner serpentine belt is probably a better choice. Here is my serpentine belt on the lathe -

Both V-belts and serpentine belts run fine on crowned pulleys. They're not really designed for that but they work anyway. Serpentine belts are the type now used in most automotive applications, so they can be found at any auto parts store. A serpentine belt is basically a bunch of mini-V-belts side-by-side. Because it's thinner in one direction than the conventional V-belt, it's more flexible, and can be reversed on itself and threaded around a relatively large number of pulleys. Conventional V-belts can have longevity problems if they're flexed in reverse.
V-belt vs. serpentine belt sections
The great virtue of the V-belt (and the serpentine belt) is that it wedges itself into the V-section pulley, increasing the torque it can transmit relative to a flat belt of the same material. This wedging action would not be present in my application, as I was using the old crowned pulleys, not replacing them with V-pulleys. However for a sub-horsepower application I figured, correctly, that would be OK. I know of some owners who have tried to revamp their lathes by machining V-grooves into their drive pulleys. Don't bother - it is entirely unnecessary. Even without grooves, the rubber belt has far more traction on the pulleys than the original leather.

Buying the belt

I bought a belt at NAPA autoparts. It turned out to be a tad short, and was a real chore to put on. Were I to do this all over again I'd get a belt that was about an inch longer. Mine is a Gates Micro-V® 040390, which one might guess would mean that it's four little Vs wide and 39.0 inches long. Mais, au contraire, on the back of the package it gives 39 and 5/8 inches for the length, or 1005 mm. A PDF file on the Gates site tells a slightly different story - length 39 and 3/4 inches (1008 mm). I don't know what those guys at Gates are up to with that. In any case, I'd have been better off with a belt length more like 1030 mm ... maybe a Gates 040399 or 040400. But to get another one cost another $15, and what Robert Benchley used to call that "old New England respect for money" became a dominant factor. So I made the small one fit. ("Made it fit" means that there was some filing on the drive box casting involved. I don't want to talk about it. Do what I didn't do, and buy a longer belt.)

The width of the Gates belt is 9/16 inches (14 mm). The original cow belt was 1 inch wide. This difference is not a problem. It is possible to get wider serpentine belts, but is unnecessary. If you simply must have a wide belt, or if you want a narrow belt but the lathe is in Amish territory and there are no auto parts stores around, try McMaster-Carr -

Installing the belt

The annoyance with the endless belt installation is disassembling the spindle. It's not too bad, though. Here is the Logan 200 spindle and back gear -

Start at the outboard (left) end. The collar 259 comes off first. It needs a funny pin wrench, which I didn't bother with - I knocked it off with a hammer and pin punch. That chews up the area around the hole for the wrench pin, but it doesn't matter much on that part. Pull off the gear 215-1, and work the woodruff key 0643 out. Then the collar 130-1 should slide off freely.

At the other end of the spindle, remove the three screws holding the cap 194 to the headstock casting. Loosen or remove the bull gear set screw 0315. Then use a wood, leather, or rubber mallet, or even just a block of wood, to tap out the shaft from the left. The only tricky part is that the woodruff key 240 (under the bull gear) has to pass through a square cutout in the bearing cover 134. Otherwise, it will dent and bend the cover something awful as you mess around with it.

The spindle shaft, the front bearing and its take-up nut 132, the front cover 194, and the grease seal cap 195 will come out as a unit. The collar 131, the cone pulley and pinion assembly 118-2 or 118-2-A, and the bull gear assembly 120-2 or 120-2-A will be left sitting in the headstock. Lift those out, and you can put the belt in.

Here is another part which may have to come out, at least partially -

The Logan drive box assembly is held to the headstock by a rod, or by two pins. The drawings show two pins (see LA-16, below), but mine has the rod shown in the photo above. If yours has pins, you don't have to do anything. If it has a rod, you have to loosen two set screws and tap the rod partially out. It will probably only go one way, so try both directions before getting violent. Don't remove the rod completely, as it's the only thing keeping your drive box from falling off. Don't count on catching the drive box if it starts to go - it's all iron and %$#^&* heavy. Put the belt around the rod, tap the rod back into place, and tighten the set screws.

The countershaft has to be removed to get the belt on. Here is how Logan thought it should go together -

The drawing doesn't show a square key locking the cone pulley to the shaft. Mine has such a key, which makes disassembly a tad tricky. The keyway isn't cut all the way through the pulley, so the pulley has to come off to the left (in the photo), or downwards (in the drawing). That is, the shaft has to be tapped out to the right, or upwards. Fortunately, you probably won't have to remove the pulley to get the new belt on. But you probably will want to move it a bit. Consider positioning the pulley as shown below. The idea is to offset the pulleys a bit if you are using a narrower belt than the stock 1" of the leather belt. This is to encourage the belt to stay on the pulleys if and when it slips. Here is how it looks with the new belt installed -

Note that I have moved the cone pulley on the countershaft to the right of its normal position. A shaft collar (319 in the drawing) normally rests against the right-hand bearing. I removed the collar (in red, below) and moved the pulley (blue, below) so that it rests directly against the bearing to its right.

          BEFORE                                                                 AFTER

An alternative to the Endless Belt

If for some reason the endless belt is right out - the spindle is fractious and just won't come apart, or whatever - it may still be worthwhile to switch from a leather belt to a rubber belt, since the rubber doesn't stretch as much as the leather, and has far better traction on the pulleys. Use the same poly-V belt, but cut it, install on the lathe, then lace (with stainless steel wire, or monofilament); or start with a longer belt, overlap the ends, and glue them together. There is an extensive thread about doing something similar to a South Bend lathe on the Practical Machinist forum. I've never tried gluing a belt, so can't get into recommendations about adhesives and such myself. See the PM thread for that.

So, how does the Endless Belt work?

It drives well and stays on track. On startup, it squeals like some poor pig stuck in the gears if it's under-tensioned, but everything is nice and quiet if reasonably tight. However, I'm not sure the three cone pulleys are exactly the right sizes, as I seem to have to fiddle a bit with the tension when changing speeds. I never noticed that before - perhaps the leather belt had even more stretch to it than I thought.
UPDATE - I've taken to setting the belt tension slightly looser than optimal, and just letting it squeal for a half-second or so on startup. So long as the neighbors don't complain, that's better than fiddling with the belt tensioner every time I change speeds.

This single modification transforms the lathe, entirely eliminating its most annoying original quirks. I can recommend it without reservation to anyone who has the stamina to take his spindle apart. You'll be mystifyied as to why you put up with that leather belt for so long.

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Updated: December 8, 2004
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May 9, 2008
October 16, 2008