Help me improve my Cataract drive

[rmcphearson]

This is what I have now. It sucks. Any suggestions? This is my only lathe and I'm willing to invest time and dough in it so I don't feel like a total dufus when using it.

 

[Rob F.]

What is wrong with it? Flat belt is slipping? Motor underpowered?

 

[rustyironism]

Maybe try putting the tensioner wheel under the slack side of the belt instead of on the drive side?
Maybe take a couple inches off the length of the belt, too?
Mike

 

[john.k]

Some belt dressing?

 

[MrStretch]

++ on putting the tensioner on the other side of the belt. You didn't describe the actual problem. How you feel using it is up to you.

 

[M.B. Naegle]

Dealing with that style of tensioner as often as you would shift the belt on a lathe like this wouldn't be ideal IMO. I'd replace the current jack shaft bracket (which is actually a Miller Falls belt driven bench grinder) for one that hinges such as on benchtop South Bend Lathes. That with a lever action engament and turn buckle would make shifting belts while keeping the same tension a lot easier. Even without a "proper" iron or steel jack shaft bracket, you can make one with 2x4's, a sturdy hinge, and a couple pillow block bearings.

 

[rmcphearson]

Everything involving the drive needs to be reworked. If I'm going to redo everything I want an ideal set up. And I'm not familiar with the typical drive systems for these old things. The motor is hinged on primitive "pillow blocks" and is heavy enough to keep the v belts tight. And they can be shifted over quickly. I'm happy with that part. I'm not sure how to incorporate another hinge set up while keeping the motor hinge set up. These are the options that I came up with myself (with my limited experience):
1) A variable speed DC motor replacing everything. No need to move the belt.
2) A screw/turnbuckle tensioner at the base of the jack shaft bracket, eliminating the current post tensioner.
3) A screw/turnbuckle tensioner at the base of the jack shaft bracket, and the current post tensioner.
4) A screw/turnbuckle tensioner at the base of the jack shaft bracket, and adding an automotive type tensioner spring to the current post tensioner.
5) A hinge system for the jack shaft. I'm not able to envision that.

I think I'd frequently change speeds with the v belts, and infrequently change the leather belt position. That's why I'm considering options 2-4.

Thank you all for your replies.

 

[Rob F.]

First thing I would do as others have mentioned is to put the tension wheel on the slack side of the leather belt. Not on top but under the belt pushing up. That could be a longer roller on some sort of over center mechanism on a spring so the different speeds would all work without major adjusting. I am thinking you pull a spring with an over center lever and the spring pulls up on the tensioner, always holding the right tension if you can get a good goldilox spring.
I would also avoid a simple DC motor it will not have any low rpm power compared to a belt reduced drive like you have now.

 

[Doozer]

Use a pulley-motor drive off a SouthBend.
It has belt adjusters, a hand clutch, and mounts
to the table. I saw a pulley-motor drive off an AtIas
lathe on a Rivett 608, and it was a good fit.
Trash what you have and go with a known engineered
solution from another lathe.

-Doozer

 

[lazz]

The belt looks too long. A long belt wanders on the crown pulleys.
You also need a way to release the tension on the belt when you are not using the lathe. Constant tension on a leather belt stretches the belt making it longer.

The next comment is strange coming from someone with no flat belt machines in use.
You have a sewn splice... While that can be a working method to splice belts... You are cheating yourself out of the ticking of a metal splice. I have always cherished that sound...
The tick, tick, tick of a metal splice means to me the world outside can be as crazy as ever but right here right now things are working and all is well..

 

[Doozer]

Scarfed and glued is the way for me.
I can't stand noise.
That damn ticking would drive me (more)
nuts. Keep it.

I have a 1920 Cataract QC swing lathe
with the factory overhead drive.
It has Silent Chains for high and low speeds.
Now the chains are stretched and NOT silent
any more. I really want to machine the teeth
off and convert to J-rib belts.

I have a Hendey T&G with motor-gen drive.
The generator is 3600 rpm and a fan that
makes noise enough to wake the dead.
I might take the fan off the gen shaft and just
use a 6" computer type fan, or convert the
thing to 3 phase and a VFD.

If I could make a lathe as quiet as my HLV-H
that would be nice.

-D

 

[Chris Lesiak]

It has been mentioned that you should put the tensioner on the slack side of the belt. What you show is correct; the top side of your belt is the slack side for normal turning on the lathe.

 

[M.B. Naegle]

The South Bend set-up involves having the motor mounted to your jack-shaft bracket, not under the table, so it's belt tension remains constant. They also don't use the 2nd cone pulley set between the motor and the jack shaft. Various makers used this same set-up and at most I've seen 2 speed options between the motor and the jack-shaft, and they were not frequently used. They often use the motor's mounting slots to change it's tension, and if you need to shift speeds you just muscle the belt from one step to the other. Your flat belt should be your main speed change. Those three speeds should give you the needed variation between high speed with low torque and low speed with high torque, but if you need more speed options I'd do like others and use a 3 phase motor and VFD drive. A lathe this small don't need much horse power and small HP 3 phase motors are cheap, but a good VFD will deliver consistent power across it's range.

There are other ways to do it, but this is the most common and most proven IMO. Any other mechanical means of speed variation you will need to factor in easily changing tension to change belts, or factor the tension into the length of the belts. That's one place that old flat belts do well with IMO is that they can be set to still transmit a good amount of power without being "taught" and hard to shift. A lot of the old overhead jackshaft lathes had no tension adjustment because the distance between the head stock and the ceiling was enough that the stretch of the belt made it easy to walk from one step to another. The shorter your belt gets, the more tension is required to keep it from slipping and flopping around.

Also keep in mind that not all slipping belts are suspects. If you're taking a heavier cut then the machine is meant to do, your cutter is dull, or you're cutter geometry is off, think of the slipping belt as a safety until you rectify THOSE issues. A 1" flat belt should transmit about 1HP, and most of these little lathes were originally supplied with 1/2HP motors, so consider that with the belt slips.

 

[jim rozen]

For a hinged tensioner you probably want the motor and the jackshaft on the same, hinged plate. Motor V-belt stays same tension when the flat belt gets tight.

What everyone is dancing around here is something I'll come out and say: a thinner automotive serpentine belt won't need a tensioner and won't slip. If you put a 1/2 hp 3 phase motor and a VFD on the rig, you'll have lots more oomph available. I've gone through a variety of configurations on this open belt lathe and this is the nicest one I've found. Note the lack of tensioner - the plate at the top does have the adjusting nuts to finre tune things - set it and forget it. I slip the belt off when not in use. The motor is 1/3 hp and do NOT try to stop the lathe cone pulley when it's running. The serpentine belt is not even one inch wide.

 

[rmcphearson]

Thank you all for the input. A lot of info there!

I thought DC drives had 100% torque at all rpms, while 3 phase VFDs the torque was proportional to the rpms.

 

[jim rozen]

For motors run from a VFD, they are constant torque below nameplate speed, and constant hp above nameplate speed.