frame assembly of Gingery lathe

That is mostly true, although I have seen cases where rivets were used as pivots in lever joints. Usually on cheaply made mechanical devices (think of a cheap can opener, for example).

Sounds like Gingery is making some assumptions about the reader's skill level and ability to improvise. Then again it wouldn't be much fun to build a machine in a strictly paint-by-numbers fashion, where one's noodle isn't brought into play. Maybe when he talks of welding the frame together he doesn't bother to mention the use of nuts and bolts for any hinged parts. I don't know since I don't have the book.

Not sure you need an entire book on the subject in order to get the layout of the different motor frame styles. This link should provide the needed info:

Thanks to Artemia Salina for helpful comments.

Whether one installs rigid rivets or pivoting ones to make the motor frame, how does one install them?

Gingery considers the design of the frame to be extremely simple, but does go into a lot of detail, just as he does in the rest of the book. It's just that there are things I don't know in this case that I don't know how to look up.

Regarding my question:

Trust me, I need an entire book. Or maybe two books. One on how one designs and builds frames for various purposes, and maybe has a chapter on building frames for motors. The other on motors, their classification, and varieties of things to do with them. I see that Lindsay Books has reprinted an old book on dynamos and electric motors, and another one on armature winding and motor repair. Maybe that would give me some background, but probably not explain NEMA stuff (for some reason, I'm having trouble connecting to

I took a look at the site. It has a table of sizes that ought to be fairly useful after I've read the book.

Ignorantly, Allan Adler snipped-for-privacy@zurich.ai.mit.edu

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There a number of types of rivets and ways to install them. Basically though, you would drill holes through the members to be riveted and insert the rivets into the holes. Then the rivet is compressed or "peened over" in one way or another, either by means of impact or through the use of a press. Hot rivets are used in some cases because the rivet is easier to compress when heated to a plastic state and because as the rivet cools it contracts, drawing the joined pieces more tightly together.

I think maybe there is some confusion with the term "frame" here. Electric motors have frames which are integral to them. There are different standard types. It sounds like from your description that the frame of the motor is attached to the frame of the lathe. You say that Gingery states that the frame of the lathe will have to be modified to adapt a motor with a different frame type (lets call it a "base") than the example he uses in his book (a NEMA 48).

To substitute a motor with a different base would require information on the dimensions of the base (bolt hole patterns, height of shaft from bottom of base, etc.). This information will allow you to design an adapter, or modify the design of the mounting on the lathe's frame, to attach a motor with a base style other than a NEMA 48.

Specifically, what other information do you need?

I built a slightly larger version of the Gingery lathe and may be able to help. The frame that carries the countershaft is pivoted at the base on each side so that it can be moved back & forth when neccessary to shift the belt to the different pulley diameters for changing speeds, but the frame itself should be as stiff as possible so as not to upset the alignment of the countershaft bearings. Think of it like a door, you want the door to easily open and close but you wouldn't want the door itself to bend or twist. A casting would be ideal for this part from a stiffness standpoint but a good one would be harder to make. Mine was welded up from 2" steel angle because that was the easiest way for me, but rivets would do if you don't have welding equipment. NEMA is a set of standards and specifications that the National Electrical Manufacturers Association came up with for motors so that, in theory, every #48 motor base will interchange with every other #48 base, as far as hole diameters and spacing is concerned. My motor was an ancient one built before the NEMA standards were thought of but I just sized the countershaft frame to fit what I had. There are motor handbooks that show base diagrams for the various NEMA frame sizes ("frame" in this case referring to the motor's mounting base) but it would be better to find the motor you are going to use first and then use it as a guide for building the countershaft frame. Mike.

I've made a little progress.

In the lathe book, Gingery mentions peening on page 70, which presumably means using a ball peen hammer. In his book, Building a Gas Fired Crucible Furnace, in connection with the frame for that device, he says (p.44) one can purchase soft iron rivets in a hardware store or one can cut lengths of 1/4" iron rod and use a one pound hammer to cold set them. On the same page, he says that the pivots in the mechanism are made with these rivets. According to my dictionary, which I've been consulting more frequently since reading Gingery's books, the fact that is calls them pivots suggests that these are parts that are intended not to be rigid.

I think the following conclusion is valid but it would be reassuring for someone to confirm it: If you want to install a rivet, you take a small piece of iron rod and hit it with a hammer until all the ends protruding from the hole are too big to go through the hole. If you want it to be able to pivot, make sure from time to time that you can still move it. If you want it to be rigid, keep hitting it until it won't pivot anymore.

Regarding motors:

Thanks for pointing out this possible source of confusion.

Regarding what information I need on motors:

Maybe I don't need it. I think it is probably easy to modify Gingery's design to meet other specs. But I also like to do a lot of peripheral reading when I have a concrete example to compare it to. I guess I'm hoping to wind up with a good reference book so I don't have to pester everyone so often with dumb questions and can be a little more independent.

Ignorantly, Allan Adler snipped-for-privacy@zurich.ai.mit.edu

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You're right, except that I would recommend drilling two (or more) holes adjacent to each other in a joint and riveting them if you want the joint to be rigid. A second or third rivet will positively prevent the pieces from pivoting.

And as I say, (red) hot rivets will form an even more rigid joint due to contraction when cooled.

I understand that the only motion that the frame should allow is in the direction towards and away from the motor. It also makes sense that the parts described as pivots ought to move, or at least to be connected by a movable joint to a part that moves. I would expect that the only parts that actually move are the release lever (which is rigidly attached to the release crank and the handle) and the release link, i.e. parts 7,6,10,9, respectively. From the picture on p.71, I think it is intended that the release link pivot (part 8, which I think is rigidly attached to the upright rail, part 4) is intended to block the release crank from moving any closer to the motor than it is in the upright position of the release lever. Thus, in the door analogy, this is the part of the frame that keeps the door from being a swinging door and allows the door to assuming a limiting position in which it is closed. Such an arrangement makes sense and I think it was Gingery's intention. It also implies that the upright rail is suppose to be rigidly attached to the base rails (part 5) and unable to pivot.

The reason I have doubts about that conclusion is that Gingery writes, p.71: "The mechanics of the assembly are simple. Notice the dotted center line from the release link pivot to the release lever pivot. When the release lever is drawn forward, the crank will pull the lower link pivot over the center line, unlocking the linkage and pulling the upright forward."

In other words, he seems to be saying that the upright does move. If it moves, I don't see what there is in the construction that keeps it upright. The motor is going to be turning the motor pulley, which will turn the outboard pully and the counter shaft. These are mounted on pillow blocks attached to the upright rail, which is therefore going to be subject to some significant forces, in my uninformed opinion. It would make sense for the upright rail to be completely rigid in order to keep from getting jerked around by the motor.

Since I haven't finished reading the entire book, and don't know yet exactly how this set up is connected to the pulley in the headstock, I'm not sure yet exactly how the release lever is supposed to let one change the ratio for the pulleys and why, once selected, the selection is supposed to remain stable. Maybe I'll be able to answer my own question after I've read a lot further. On the other hand, maybe what is making me uneasy about this is also related to the reason why Gingery writes on p.70 that he has belt slipping problems when he uses an 8 inch outboard pulley instead of a

Ignorantly, Allan Adler snipped-for-privacy@zurich.ai.mit.edu

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My take on the motor frame etc was that it was more work then required. My first motor was a small 1750 rpm induction motor and I put step pulleys on both the motor and spindle. I had 4 speeds by changing belt positions. Now I use one of those surplus 2hp (1.5 is more like it) DC treadmill motors (remember that flurry of RCM purchasing a few years back ?), which works really well. Both of these motors required a simple mount that I built to fit. And that's my advice here, get a motor (DC with speed control is ideal) and then worry about the frame/mount/whatever.

Artemia Salina kindly confirmed my impressions about installing rivets, while adding some additional pointers:

I went back and took another look at the drawings on p.71 and p.75 of Gingery's book. There are definitely places where two rivets are indicated, making it clear that he wants those attachments to be rigid, while the rest are single rivets, indicating that he wants those to be able to move. So, that clarifies his intentions about what is supposed to move and what is not.

Even though the upright rail is allowed to move, there might be a reason, falling under the category of "ingenious mechanisms", why the upright rail can move away from the motor but not towards it. I half convinced myself that this is so, but I still need to think about it. Maybe someone (MikeM?) with first hand experience with the Gingery lathe can perhaps confirm or reject that conclusion.

Getting back to how one actually installs rivets, there are some more details that I don't understand. First, how does one make sure that the rivet deforms and doesn't instead move through the hole when one hits it with the hammer? Presumably, some kind of support is required under the plate and/or rivet, but what kind? Second, it seems that there might be some risk of causing some deformation of the plate itself in the process of hammering on the rivet? Is that risk real and if so how does one avoid it (this might be another reason to prefer red hot rivets)?

Ignorantly, Allan Adler snipped-for-privacy@zurich.ai.mit.edu

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Since I've never really worked with rivets (aside from "pop rivets") before the following is just what I would imagine. Anyone with any experience please jump in.

I would think that an anvil would be ideal for use in installing rivets if you were to hammer on them. A press would be even better to use as there is little chance of damaging anything by a missed blow of a hammer and also you could use a die to give a more professional finish to the rivet. What I've seen on the "back" side of rivets are cross-hatch patterns and perpendicular notches. The perpendicular notching seems to be done in order to assist the mushrooming of the rivet.

If you don't have an anvil then any massive object with a tough flat surface should do. I have a chunk of railroad track that I use as an impromptu anvil, for instance. I don't think lots of hammering is necessary to set a rivet, depending on it's size and material. You could regrind a chisel to assist in setting rivets in tight spots. Grind it so that the business end is slightly cup shaped if possible, and rest that end on the rivet and give it a whack or two.

On my reverberatory furnace, I used my 6" chunk of track plus a 16-20oz. hammer to set the 3/16" dia. rivets which the lid hinges on. (It's under the current update on my webpage.)

Tim

-- "That's for the courts to decide." - Homer Simpson Website @

I'm pretty much convinced now that the upright rail, although moveable, can only move away from the motor, not towards it, from the upright position. The argument is as follows: (1) Let the rivet for the upright rail be A, the rivet for the release lever be B, let the rivet joining the release link pivot to the release link be C and let the rivet joining the release crank to the release link be D. Assume the motor is on the left, so that A is the left of B. Then if one tries to push the upright rail towards the motor, the motion of the upright rail and the release lever will both have to be counterclockwise. (2) Let E be a point on the base to the right of B. Then the angle CAE is less than 90 degrees and angle DBE is more than 90 degrees. That means that when the rails are rotated to the left, C moves up and D moves down, and therefore, since D is lower than C to begin with, the vertical distance between C and D increases. (3) On the other hand, the right side of the release link pivot blocks the left side of the release crank, which makes it impossible for the horizontal distance between C and D to decrease. However, the actual distance between C and D is always the same, since C and D are rivets located on the release link, which is one piece of metal. (4) The square of the distance from C to D equals the sum of the squares of the horizontal and vertical distances between C and D (Pythagorean theorem). If the motion towards the motor were possible, the horizontal distance would not decrease and the vertical distance would definitely increase, so the distance between C and D would have to increase, which it can't.

Therefore, motion towards the motor is impossible.

I think that aspect of the design of the frame assembly is pretty clever and is not explicitly mentioned by Gingery. There is nothing actually blocking the path of the upright rail from moving toward the motor, but it still can't move that way. And that feature would have to be preserved by anyone proposing to modify the design for use with another motor. The moral is that one has to make sure that the release link pivot and the release crank have a significant overlap of their vertical edges.

There must be a lot of tricks like that which apparently everyone takes for granted, but this is the first time I've seen anything like that. There is an expensive (one could buy a Clisby instead) four volume work called "Ingenious mechanisms" which might be the place to look for things like this and might not. Does anyone know of a book that definitely has this trick in it (besides the Gingery lathe book)?

Ignorantly, Allan Adler snipped-for-privacy@zurich.ai.mit.edu

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I had to get my copy of Gingery's book out of storage. His terminology for the linkage parts is possibly confusing but the mechanisim is clever and simple. The countershaft frame, when locked, is prevented from moving from the extreme of its locked position by the support piece (he calls it a "crank") for the release lever end of the pivoting link striking the similar support on the c. shaft frame, and also by the pull of the belt. In any case the motor, in his design, is bolted to the c.shaft frame and will move along with it. I departed from his plans here and mounted my motor under the lathe bench on a swiveling sub-base which kept the motor belt tension constant using the motor's own weight. Also, since I condidered this to be an experimental assembly and subject to change, I used 5/16" fine thread bolts with double locknuts for the pivots instead of rivets in the locking linkage and 1/2" bolts for the c.shaft and release lever frame pivots. His comment about belt slippage is accurate, and the lathe would be greatly improved by a backgear drive. A DC variable-speed motor will help also and I considered it, but 15 years ago when I built mine small DC motors were not as easy to find and industrial motors were around $300.00 from Grainger. A later book shows how to make change gears for threading using a milling machine from another book in the series, though I never got that far with mine. The lathe is really best suited for turning plastic, wood and non-ferrous metals. While I managed to coax mine into doing fairly heavy work on steel, the machine's lightweight design made it prone to chatter and using it at near its maximum capacity could be a slow and frustrating experience. Mike.

Thanks to MikeM for getting his copy of Gingery's lathe book out of storage and checking the details of my argument and pointing out the oversight that the motor is mounted on the upright rail. Taking that into account, I think my argument is ok for the assertion that one can't move the upright rail counterclockwise by pushing the other rail in that direction.

Please don't put it back just yet! (cf. another posting on the next chapter)

Thanks also to Artemia Salina for suggesting Anthony J. Pansini's book "Basics of electric motors: including polyphase induction....". I had a chance to look at a copy today in a library (the book itself is out of print) and will have to look at it some more to form a definite impression. One thing I think it doesn't discuss is different ways of using motors.

One of the reasons Gingery is able to get his design to work is that he draws on skills in using motors for ad hoc purposes. This allows him to use his ad hoc setups to do some of the work that he would normally need the lathe to do (e.g. boring the headstock). This also applies to his earlier book on the charcoal foundry, where I recall he mentions making a grinder out of a motor, and probably to some of his other books.

Since Gingery already wrote several books where he builds things that feature motors, it might seem like I'm asking for one book that contains what it takes several books to explain. But actually, all that is required is an account of the available methods of interfacing a motor to something else, and that would probably fit in one book.

Ignorantly, Allan Adler snipped-for-privacy@zurich.ai.mit.edu

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• in any way on MIT. Moreover, I am nowhere near the Boston *

• metropolitan area. *

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