Spider dead center

New here and looking to buy a lathe. I have a whole list of projects that I would like to do. I have read many of the what lathe to buy threads and I am not looking for that advice. Some of my projects will be barrel threading and chambering. Not looking for advice on that either. I have read the threads on the different ways to thread and chamber barrels. The method most appealing to me is to do threading and chambering between centers. Based on the lathe advice threads you need a large lathe with 35 to 40 inches between centers. Those are big lathes.
So here is my question and I will use a Logan model 940 lathe as an example because I know of one for sale at a reasonable price. A Logan 940 has a 1 3/8 spindle bore but is only 24 inches between centers at best. To get more distance between centers would it work to make a spider with a dead center in it. I may be using incorrect terminology here. I don't know the length of the spindle on a Logan 940 but it has to be around 12 inches or more. This would give a between centers distance of at least 36 or so inches with a dead center mounted on the end of the spindle. Attached are two crude Google Sketchup images of what I am calling a spider dead center.
One version has a bushing bored to hold a MT#3 dead center. The bushing would fit inside the spindle bore and would be secured by set screws. The spindle would have to be drilled and tapped for the set screws.
The other version would fit over the outside of the spindle with set screws in the spider to hold it to the spindle.
If this is a good solution it would open up a larger selection of lathes that I could chose from.
If this is a really dumb idea it won't be the first time someone has told me that I am not playing with a full deck of cards.
So what do you think?
Chuck
PS I am retired and recently went back to being a dirt dweller after living on my sailboat for a number years.

A 40" center lathe is not big, it's a toy. Don't screw around with half ass mickey mouse bs. Get a lathe that is big enough to do the job.

Putting a center back there can work, but you need to think about how you're going to drive the barrel. A dog in a face plate up front is probably going to flex the barrel and make it chatter. You never know, it might work fine. Just seems not so good to me.

I have one that goes up inside the spindle that I use for short barrels. But the front end is held in a set screw chuck (spider if you like) and dialed in.

Also how to do the work. Between centers can be fine for the OD work, but out end held in a steady, a 4jaw or a spider for the ID work.
Surprises me that nobody puts a center to (in) the back side of the spindle. could be live or dead.. even held in a spider of sorts. it seems the muzzle end ID would run truer than the indicating the OD. I wonder how true the tube ID would be? I wonder how true the barrel ID to OD runs at the muzzle end.. I used to turn Mouser 98 barrels and they ran near dead to the ID at both ends so suspect they were between centers turned after the bore was done..Yes some were turned very course on the OD with almost a thread showing the fast feed.
Yes a centered plug might be good for the muzzle end.

Measure a few guns over the front sight as it can help to have a lathe spindle hole that a front sight can fit through..save a lot of time if you decider to use a spider on the back end..and for collect use the hole size matters.
Having a MT at the spindle bore with using a face plate for the driver and using a dead soft center can work well.. You turn the point with a bit and with that the center runs dead true to the spindle. Yes you have to tickle it after each time you take it out.
This increases the distance to the tail or end of bed that would be used up by using any chuck.

If you want to use a smaller lathe, then chamber through the head stock with a 4jaw and an outboard spider. Make sure to get a lathe with a large enough spindle bore. Also put Copper wire around the barrel so it can pivot in the 4jaw chuck.

I'd like to thank everybody for their suggestions. My first choice of course would be to buy a lathe that has sufficient distance between centers to suit my needs.
It also appears that a spider with a dead center would work if I can drive the barrel. I could make a dog that would fit fairly tight to the muzzle with a set screw to hold the dog to the barrel and have two ears on the spider that the dog would engage with. Attached is another drawing of the spider and the dog. Again I apologize if I am using incorrect terminology.
Chuck

It would seem a face plate would take no space on the logan and a bent tail dog could drive the barrel as well as a special made center with a drive collar. That way you might use a shorter center and so get more space between centers.

Also a collar to thread on the logan spindle nose with 4 screws to act as a spider would be easy to make.

I do think a steady is handy for barrel work.

I have a list of projects to make for whatever lathe I get starting with a simple turned bar to check the alignment of the tailstock. Next are 3 and 4 jaw spiders for both ends of the spindle. I also need a fixture to be able to accurately drill holes in round tubes. I frequently need to drill holes in the stainless steel tubing on my boat. I think that these are relatively simple projects and good to start with. If the lathe doesn't come with a steady rest or follower rest I will make those. I also plan to make a milling attachment. I am sure that my list will keep expanding. I figure that I will spend a year or so just making things with ever increasing levels of difficulty before I attempt any of my gunsmithing projects.
I typically make detailed drawings of things that I would like to make. I used to use pencil and paper. Now I use Google Sketchup. Drawing in 3D at least for me seems to reveal fabrication problems that aren't apparent in 2D pencil and paper drawings.
Once I get my lathe I will probably start an ongoing thread on my projects seeking advice on how to solve the problems I encounter.
Thanks again for all of your suggestions on my idea tor a spider with a dead center.
Chuck

I could make a dog that would fit fairly tight to the muzzle with a set screw to hold the dog to the barrel and have two ears on the spider that the dog would engage with.

You might make your driving dog larger so it could handle barrels of different size. That would require a number of different driven collars. And instead of a set screw on the collar to couple to the barrel, consider splitting the collar and using a clamp screw to tighten it on the barrel.

This is a poor pic of a clamp dog: non-marring clamp dog

A collar with splits and a clamp screw could work. It would just depend on how fine you can make the threads and I don't know the answer to that question. I did some sketching and the clamp screw would be about .0625 thick I like your idea. It would be better than a set screw and one collar would fit the range of muzzle OD's that I might work with.

Attached is a sketch of a collar with a screw clamp. The center of the collar is tapered so that when you screw the clamp screw down the collar it will hold the collar tight to the barrel. This all might be academic. I might be looking at a sheldon lathe this weekend with sufficient distance between centers to suit my needs.

I used to hold the muzzle in a 4jaw and put some part in a steady(with pulling the trigger off to avoid hitting) turning 98 barrels.
But with putting the muzzle on a head stock center one would have to hold it tight as the drive dog would drive but not hold it tight to the center. So for that I think my old grinding trick. Drive with the dog with part on center.. then with a collar and a number of rubber bands hold the barrel tight to the center.
Between centers is fine for barrel OD work but any inside work the tail center has to be out of the way.

After mulling everybody's suggestions over I think that I have finally come up with a workable design. Attached are google sketchup drawings.
One is for fitting inside the spindle. The spider would be held to the spindle with a screw drilled and tapped through the spindle and into the spider. There 3 bolts that hold the barrel against the dead center and drive the barrel.
The other is fitted over the outside of the spindle with a screw drilled and tapped through the spider and into the spindle. There are again 3 bolts that hold the barrel against the dead center and drive the barrel. This design is only convenient to use if the OD of the spindle is concentric with the spindle bore. If the OD is not concentric then you would have to use 3 screws to hold the spider to the spindle and dial in the spider every time you used it.

If those screws do what I think they do, they're not going to hold the barrel against the dead center. Rather, since you can't tighten them perfectly even they'll push it off the dead center as you tighten them, resulting in the barrel being out of true.

And if you actually have that much room why not just put the barrel in the set screws and dial it in?

You will find centering the barrel a lot easier if you use 4 screws instead of 3.

Wesg
I hear what you are saying and have thought about that very issue. I am a newby to this and based upon my lack of experience and knowledge I can see myself making significant errors with the thru the headstock dialing everything in method of threading and chambering a barrel. I think that Spearchucker's method of doing this between centers has less chance for error for a newby. There seems to be some debate about which method is better.
I am only going to be doing this for myself. The rifles will be primarily for hunting and casual target shooting.
From reading the other posters' suggestions it doesn't sound like it takes much pressure to hold the barrel against the dead center. One poster mentioned using rubber bands.
I have passed by several 9" lathes with sufficient distance between centers because of their tiny spindle bore. I really want to get a lathe with a spindle bore of 1 3/8" because I have other possible projects not related to gunsmithing that would require a 1 3/8 spindle bore but don't require turning between centers. So I am exploring my options for lathes that can meet my requirements. If I can use a dead center in a spider then that would expand the selection of lathes that would meet my needs. What I will end up with is anybody's guess.
I appreciate your comments and the comments of the other posters.
Thanks for your thoughts

Sorry, kinda forgot what it was you were actually trying to do. Was thinking a 4 jaw at the other end.

Whatever you come up with, it probably needs to be usable to crown the barrel as well. And if you're going to do that it might open up some options for holding onto it for chambering, since you're going to cut it back at some point.

First thing that popped into my head was to run a tap into the muzzle a couple turns, and thread it onto a screw in the spindle attachment. Kinda crude and may not be secure enough. Next was a collet chuck of some sort, even a bored hole and set screw. Start by holding the breech end and turning a short section of the muzzle to fit and then flip it around.

Or make the thing larger in diameter and cut some slots through the side for a dog to go through. Couple pieces with v grooves and clamp screws. Thrust for chambering is taken by the center, but you need a chord or spring to keep it engaged.

I must be misunderstanding something here. It is my understanding that when you are turning something between centers the pressure from the centers keeps the work against the centers and you just need some means to drive the work. On the other hand if one end of the work is on a center and the other end is in a steady rest then you need a way to drive the work and a way to hold the work against the center. Are these assumptions correct?
It looks like I would need different setups depending on what I am trying to accomplish instead of a one size fits all solution.

Correct,

A part set on the head stock center and the other end in a steady may be driven by a lathe dog, perhaps from a face plate with a bolt or such pushing to turn the part around, but the part would just float away from the head stock center. A collar can be set around the part (barrel) perhaps with three screws and then perhaps three O rings stretched to anchor to the face plate also. Something has to hold the part tight to the head stock center.
A collar might just be a cut of pipe with three screws through it to contact the part. Even rubber band would hold.. I have done much grinding with rubber bands holding a part tight to a center.

Threading, drilling reaming toward the head stock would be fine..but any work going away from the head stock may pull the work off the head stock center.

Any spider going into the the spindle would reduce the ID hole. A tube on a face plate would keep the hole open so might be a spider off the chuck mount thread and face up to the chuck register. That would not be a center but a spider to contact the part OD. Such a spider could also be the draw device with adding O rings or rubber bands to pull tight the part toward the head stock center that is in the taper, and it could be designed to be a dog driver.

At CST we were trained on 9 inch South Bends with a small bore. Used a piloted cutter to cut centers in each end of the barrel. Then turned between centers to true the tenon concentric to the bore and then thread the tenon. Set up a steady rest on the tenon while still between centers. Once the steady rest is adjusted, backup the the tailstock and loosen the face plate. We then laced the dog on the muzzle to the face plate with a leather lace and then tightened the faceplate back to the spindle. By loosening the face plate about a 1/4 inch, lacing the barrel to it, and tightening the face plate, there was no chance of the muzzle coming off the center.

That was before bench resting became popular and everyone decided that bores must be concentric within .0000000000000000001 microns(or is it .00000000000000000000000000000000001?.