Does it exist?

Well there are lathes intended for turning full size loco wheels but I suspect they won't squeeze in either
AWEM

There are specialist things like brake lathes, for refacing automotive discs & drums, but I don't know whether they would be viable for your sort of job.
Gap bed Colchester Students - at least the older L0 spindle verisions, don't know about the newer ones - can turn over 18" dia in the gap, & they're not a huge machine. I suppose it all depends on your idea of 'large'.
Cheers Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service

What diameter are you actually talking about here by 'large swing'? Your large might be my small. -- Dave Baker Puma Race Engines Camp USA engineer minces about for high performance specialist (4,4,7)

Do you have a horisontal mill?
See if you can fashion a type of chock or holder to go into the spindle bore and then removing the over arm and depending on what you can get between the knee and bed use a cutting tool fastened to the bed to do you cutting.
I have managed 2 ft dia with this on a Harrison mill.
Adrian

A Willson slant bed lathe may do what you want.Due to the slant it makes the swing a lot bigger than normal for that size of machine.It so happens I know of one for sale which could be measured.Footprint the same or smaller than a Student and a better machine. Mark.

As has been said it depends on the meaning of *big*.
Starting at the small options you used to be able to get an attachment for a Myford to raise the spindle. A few designs were made, one no suprisingly called "big turn". I think that Hemingway did a kit aswell.
Bigger gap bed lathes don't have to be huge. My Kerry will swing something 17" x 3" in the face plate and that's just a 5.5" x 24" lathe. Not a big footprint.
Colchester did make a "short bed" version of the round head Triumph which must swing 23-24" in the gap.
Or do you need bigger than those?
Charles

How about a Raglan Loughborough training lathe. Tthe same capacity as the 5" but much shorter bed, and no screwcutting. They don't seem to fetch very much either, seen a couple on ebay. there's a picture and description here;
Regards Kevin

There was a facing lathe, or whatever they call them, on one of the toy shop sites a year ago, it had been there a few years so it's probably still there; no I can't be more helpful than that, I came across the site quite a few times from google searches though.The lathe had something like a foot of bed and a 3ft or so swing..

Depending on how big your mill (yes, mill) is, you can use it as an "inverted" lathe. Clamp the flywheel onto the spindle, clamp a lathe bit into the vice and you have a not-so-handy lathe. I had the same problem and it worked really well on the mill.
Nick

Or alternatively set the flywheel up on a rotary table on the mill table and mill the features that you would have turned. This is rather more stable (if it is a big flywheel) than trying to hold it in the spindle, and has the big advantage that the cutting action is on the upper surface that you can see rather than underneith.
AWEM

I made that before. You don't get that "it-was-turned finish" a flywheel asks for. Also tried it with a big boring-head (planning and boring head with feed in the diameter) and wasn't happy either.
Vision is an issue with the setup I described, no doubt! But on my Deckel I could turn diameters of 1m with the horizontal spindle. No, the RPM would be way to high and the setup _much_ to risky. I made 300mm diameter on the vertical spindle and will do it again without doubt and fear.
Nick

Yup! A 3 in 1 machine tool with the mill removed. Massive swing for the size of the machine.
Cheers Trevor Jones

Good point everything is relative - for me, who has a Myford and wishes to make models such as those from Alyn Foundry, large is 10" - 12", but the workshop space would struggle to accept something more than 3ft long.
Thanks for the input so far....
John Ambler Sussex, UK Return E-mails to snipped-for-privacy@skiprat.net

I got an old book describing various repairs on large steam engines and the like.
One was an engine with a damaged low pressure cylinder piston of 86" diameter. Would have taken 3 weeks to get a new one and they did not want to wait, the largest available lathe was only like a 24" swing. They ended up building up a framework of I beams bolted to the floor and some pillow block bearings on top for a spare piston rod which was used as a spindle to spin the piston. An old gearbox was connected up between a motor and the shaft to turn it slow. A lathe a smaller one not the 24" was bolted to the floor in front of the spinning piston. The lathe had a spot on the back side of the cross slide for mounting an inverted cutoff tool, this was used to mount a turning tool pointing out the back of the lathe. The repair to the piston was to cut some dovetail groves to hold some babbitt to build up the diameter of the piston. And then after the babbitt was poured and hammered well into the groves the OD and ring grooves were cleaned up to size on the same setup.
You could maybe do something similar. _____________ Andre' B.

Sounds interesting - thanks to everybody who gave so much food for thought - sorry also for the slow response - I haven't been able to connect to my normal News server (Tiscali) since the 3rd.
I have a Warco miller (VMC), so the suggestions centring on the vertical lathe are also worth a try - I have a Myford chuck adaptor for it so mounting a 9" faceplate is possible. Any thoughts on whether a support bearing on the table would be benefcial for turning the outer face of the rim (equivalent to tailstock support) ?
John Ambler Sussex, UK Return E-mails to snipped-for-privacy@skiprat.net