Warco Mill drive belt problems

[houstonceng]

Hi Guys

The manual for my Warco A1S mill (Similar to a Warco VMC, Myford VMC & VME, Grizzly G0728,29, 30 & 31 and probably Jet, Chester and Axminster as well) states that the belt sizes are B40 from quill to intermediate pulley and B35 from Intermediate to motor pulley.

They are, probably, the sizes when fitted with a 1ph motor. I bought the mill with 3ph motor and inverter and the belts supplied were B38 & B35. These tensioned OK, but were a real PITA when I needed to change pulley speeds. Normally, I run the motor on the inverter between 25Hz and 100Hz, so most of the time I don't need to change the belt positions - except when the lowest speed, for fly-cutting, is required or needing Max speed. Grizzley offer a variable speed version (G0822). It appears to be a VMC (G0802) equivalent which only has one belt and a two step pulley on which the inverter speed ratio is 6:1 (probably 20Hz to 120Hz).

Anyway, when the original belts wore out, I went to my friendly, local V Belt supplier and tried to buy the some belts that might be easier to fit and change speeds with. To cut a long story short, he "lent" me a number of belts and said that once I had found two that were OK, I could bring the rest back and pay for the one's I kept (Yes. He is a nice supplier !). The new 38/35 were almost impossible to fit, 39.5/34 don't tension correctly, so I settled on a 39/34 set. They are still a PITA to change speeds, but they do tension.

Must explain that to tension the belts, the motor swings in an arc on a pin and if the belt combination is too long, it swings past the max distance point before correct tension is obtained. Removing the tensioner and swinging it as far as possible to slacken the belts still leaves them very difficult to move from one groove to the next.

After a number of years struggling with these belts, I think it's time to do something about the problem.

I was wondering if I could turn down the pulley flanges a little as the belts would still have a lot of engagement, bit wouldn't have to climb over a large diameter edge. With another milling machine, I could, perhaps, mill some material off the motor mount to allow it to swing closed more, or - - - -

Has anyone else hit this problem and found a solution ?

[uuu]

You mention the one-belt version. Would you get an acceptable speed range if you went this way? I say this because my Meddings drilling machine just has one long belt, and I don't necessarily need to slacken off the motor to move the belt, there's enough stretch to flip it over to the adjacent pulley.

Wilf

[houstonceng]

Hi Will

I’d need to source a suitable two shieve motor pulley ad the current three way can’t be inverted. If I just take out the intermediate pulley, it would be near 1:1 in all positions of the belt as the “cone” is the same way on the quill and motor pulleys.

As I said, practical experience of inverters says 25 to 100Hz range us about correct. I know that, in theory, 0Hz to ‘hellofaspeed” is possible, but not good for motor life. The Grizxly has a ratio of 6:1 on the inverter and two steps on the pulley to cover the required speed range. So their inverter must do something like 20 to 120Hz or, being USA, possibly 30 to 180 ?

In my other thread about V belts, i’m wondering if the belts that were supplied with the mill and some I bought later are correctly sized.

[ettingtonliam]

A number of years ago, I had a discussion with Fenner about the drive belts for my Raglan lathe, which had to be in matched pairs. I was told that modern vee belt technology meant that vee belts from any one manufacturer would be virtually identical, but that between manufacturers, allowable tolerances meant that there could be up to 3/4" difference in length for the same nominal size, so don't 'mix and match'. Unless you are replacing your vee belts with ones from the same manufacturer (unlikely I would have thought, on a far eastern machine), you can expect to have to do some experimentation to get the right belt length. I don't see there would be any problem trimming a bit off the diameter of the sheaves, especially if you leave nicely rounded edges to help the belt over the edge when changing speeds.