Another 46-715 Delta reeves drive problem

[KEW]

I picked up a Delta 46-715 14" refurbished lathe as a "tie me over" lathe until I am ready to commit to my final lathe. Unfortunately, after about 4 months, it is having problems.
While this lathe would never freewheel, it binds (more than just belt friction) when rotating it by hand. You can hear it when it runs and the lathe stops too quick when turned off.
After removing the drive cover, the problem is at the movable pulley half on the spindle (not the motor shaft). I marked the pulley and the binding occurs in sync with its revolution. When I run it, I can see this pulley wobbling, but I don't know for certain that relates to the binding.
If I rotate it by hand a few revolutions in the reverse direction, everything smooths out. However, once I turn it back on, it quickly settles into the binding condition once again.

Has anyone experienced this situation and know how to fix it?

The lathe has 2 months left to it's warranty, but from the other post, it sounds like I will be right back where I am now (except no more warranty) in another few months if I just let them swap headstocks.

Thanks!

 

[Bill Boehme]

Cause of problem ......

This is another common problem on the Delta lathe (see my earlier post this week). What has happened in your case is that there is a bearing on the yoke assembly that couples to the hub of the movable half of the pulley and the part of the pulley that the bearing fits over has broken off or is on the verge of breaking.

The root cause of this particular problem stems from too much free play (side-to-side wobble) in the yoke assembly. The follower rod on the yoke is considerably undersized for the hole that it fits into and additionally, the fit between the yoke and the follower and also the yoke and the rack gear is much too sloppy. This results in the whole assembly sort of flopping around and all of the strain when changing speeds gets put onto the pulley hub.

I rebuilt the whole mess and had a machinist friend turn a larger diameter follower rod that also had a tight fit to the yoke. In addition to the roll pins that connect the follower and rack to the yoke, I also added setscrews to tighten up any potential looseness. When you do this, it is important to make absolutely certain that everything remains perfectly square or there will be a binding problem that has the potential of making things worse than before. Once the yoke assembly was completed, I installed a new pulley set and new bearing -- all of the off-axis twisting forces also had caused the bearing to fail.

I'm telling you, it was a total disaster. When any part of the yoke/pulley assembly on the spindle goes, it is like a bunch of lemmings all jumping off the cliff. I even replaced the spindle because it got galled up where the pulley rides. Delta was nice enough to gladly send whatever parts I needed -- no questions asked. Their service is great even if this lathe is not.

I concluded that keeping the Reeves drive would be maintenance hell, so I decided to redesign the whole drive system. I have had to postpone the work right when I was in the middle of it because of back surgery, but when I am finally done with my drive update, it will be a vector drive with a 1.5 or 2 HP motor (I have both and am contemplating which to use). A vector drive is similar to a variable frequency drive on steroids -- it uses a shaft mounted optical encoder to give rate and position feedback to the drive, which then gives a corrected speed command to the motor. Not that I really need it, but it gives full torque all the way down to zero speed -- it can also do position indexing accurate to 1024 increments per revolution -- that's about 20 arc minute increments -- and it can be connected to a PC to follow a programmed speed/position profile that would give the ability to create unusual shapes if multi-axis control were desired.

However, I plan to stay away from what amounts to CNC operation because then it will cease to be an art and become just a milling machine/lathe. Anyway, this is my idea of turning a sow's ear into a silk purse. Why am I doing it? Why do we do anything -- just because we want to -- designing automatic control systems is what I did before retiring and I can't just throw on the brakes too suddenly or I might tear something loose or strip a gear.

Bill

 

[Ken Grunke]

Bill, are you using the stock pulley on the spindle for the conversion? Or using a solid pulley? I'm wondering if the original Reeves pulley will do with a variable frequency adaption if you just keep it at the low speed setting, and maybe lock it down somehow.
--
Ken Grunke,
AAW Forums Co-Moderator
member & webmaster, Coulee Region Woodturners
My Home Page

 

[Bill Boehme]

Bill, are you using the stock pulley on the spindle for the conversion? Or using a solid pulley? I'm wondering if the original Reeves pulley will do with a variable frequency adaption if you just keep it at the low speed setting, and maybe lock it down somehow.

Sorry about being so late in getting back to you, but it is newsletter time for me (Woodturners of North Texas) and things get busy for a while until I get it put to bed.

In my particular case, one of my goals was to completely get rid of the Reeves pulleys because I don't believe there is any operating condition for these pulleys that would yield any kind of acceptable MTBF, especially with the much greater torque capability at low RPM.

My new drive will use a 10-groove J-section belt and pulleys and there will be two somewhat overlapping speed ranges. One of the ranges will cover 0 to 1800 RPM and the other will cover 1200 to 3200 RPM. The pulleys are Gates QD hub types with the appropriate bushings to fit the 24 mm spindle shaft and 7/8" motor shaft. Everything will more or less fit in the same envelope as the original configuration with some modification to the belt cover and easy access to change belt ranges.

I have included thumbnail drawings of a couple of details of the assembly, but admit that it is hard to make heads or tails out of it unless you have been working on it for a while.






Bill

 

[KEW]

Follow-up

I just wanted to follow up on this.
Kudus to Redmond Machinery for customer service!
I bought the refurbished 46-715 lathe late 9/07. In a month, I took the headstock in for repair and Redmond just handed me another - No down Time!! :cool2:
3 months later, I had the problem that started this thread. I took it to Redmond and they have run out of replacements and do not want to work on these (not worth the effort) since they are so problematic. They offered to refund my money (which sure beats taking home another headstock, knowing that it will likely fail in the next few months)!

If anyone comes across this thread researching the Delta 46-715 as a possible purchase my suggestion is to avoid it. I figured it would last at least a year, but the mean time between failures for me was 2.5 months!

I also have a mini and a PM90. I had hoped that this lathe would offer me the flexibility of 14" swing and a sliding head until I finished saving up for a PM3520 (about a year) then I could sell it at a reasonable loss, but I'm back to my old faithfuls with another few months before I am ready to pull the trigger on the PM3520B.

Cheers,
Kurt

 

[Bill Boehme]

Kurt,

Redmond Machinery sounds like good folks to deal with and they are definitely being truthful. I can see their point -- the problem is not going to go away just by replacing parts -- it would require a redesign using more rugged and reliable parts in place of the die-cast zinc pulley parts. I was told by Delta's tech support that I could return the lathe at any time during the two year warranty period for a full refund -- no questions asked. The headstock, bed, stand, and tailstock are all quite decent so I decided to keep the basic components as the guinea pig for my drive system upgrade.

I suppose that next, I will be wanting to increase the swing so I will be thinking of ways to raise the headstock and tailstaock -- no wait .... gotta' stop thinking!

Bill

 

[KEW]

Bill,

You should start a show - "Pimp Your Lathe!!"

Thanks for you help your posts made it quite clear that there were fundamental design issues.

Thanks,
Kurt