belt drive conversion

[Charter Oak]

For argument's sake, the two are not compatible. I had completely neglected the fact that you have the Mach1 system when I suggested the belt drive. That being said, in order to use the Mach1 with the belt drive you would need to fabricate a "bridge" over the spindle pulley for the actuator cap to mount and then shorten the cap by the height of the bridge. We haven't experimented with it yet, but I don't see why it wouldn't work.

[Bob La Londe]

Paul, Thanks. I was looking at the whole thing and thinking it didn't look like it would work as a straight bolt on. That's why I was asking. Now I know its a little more involved than I want to do "right now." but it is something I may tackle down the road.

[Bob La Londe]

Dave, Do you machine the pulleys or buy them?

[arizonavideo]

I make them.

[Bob La Londe]

Just out of curiosity. Why did you select a multiple V-groove belt over a timing belt?

The original 5HP motor (now off) on my Hurco mill was 1:1 with a heavy timing belt. That mill was made in 1982. I made a few cuts (by accident) hard enough to stall the motor and destabilize the VFD, and the belt held up just fine.

[arizonavideo]

Its way harder to make a large T5 style pulley and the grooved flat belt is the smoothest running of almost any belt system.

[Bob La Londe]

Ok... I was thinking about just buying some pulley's and machining the bores to fit as needed. McMaster has the heavy timing pulleys and belts in stock.

[hjl4]

My old Tree also uses a timing belt. I had the mill apart a couple of month ago, and the belt was still like new. Also 5 hp.

[RustedOut]

May I ask, what's the compelling reason for using a timing belt on the spindle drive. I can see some of the advanced commercial mills using it as they tie all sorts of things into the spindle requirements. But for a small machine like these, I guess I'm not seeing the need. If spindle orientation is needed, can't that just be done at the spindle like you would for a tach input. Or are you thinking rigid tapping may be achievable? Or am I just missing something obvious?

Bob

[Bob La Londe]

What is the compelling reason for using a multiple V-groove pulley?

For off the shelf parts there doesn't seem to be much difference in price, and it seems to be easier to find the fitup I want in timing pulleys and belts.

I can see why somebody who is making the pulley from plate might prefer a V-Groove as its easier to make, but its not really cost effective in my opinion when I look up the cost of raw plate, and add my time. Heck, if Dave didn't have a six month backlog I'ld just buy his setup and be done with it.

...and when I get the head open on my Charter Oak I plan to check and see if I can repurpose some of the heavy timing pulleys I have in my salvage bin.

[RustedOut]

For off the shelf parts there doesn't seem to be much difference in price, and it seems to be easier to find the fitup I want in timing pulleys and belts.

Availability of the v groove pulleys, or lack of, had me leaning to the timing belts early on in my belt drive conversion that's still in work. But making a v groove set of pulleys was dead easy once I made the lathe tool for it. Those tools or cutters are available to buy.

Either way, there was affair amount of machining required on the mill or on the lathe to fit the hub to drive the spindle. There's no off the shelf timing pulley that I found that would fit the hub I made, I actually had timing pulleys on hand I intended to use.

It was seeming to me the target for timing pulleys in the same width as the v groove belt I chose were meant for fractional or low hp uses. But i was just casually looking at them once I keyed on using v groove pulleys, so I could be wrong in that regard. I had an ulterior motive to going to v groove as well, I'd like to put a serpentine belt system on one of my old antique vehicles, so it was a good learning experience.

Bob

[Bob La Londe]

Well... as I mentioned the 5HP motor on my Hurco mill was driving the spindle with a timing belt. I wasn't looking at XL pulleys. LOL.

[ksanalytical]

All,

I've been running ArizonaVideos belt drive for a few years now and I can say without a doubt that my machine would not be in use at all without it. It's truly been night and day where before I'd sit next to the machine and count the seconds it had been running at 3K rpm. Now the only thing I stress about is the coolant running dry during a run and I don't worry about that much. As far as the V-belts go... Yesterday I managed to drive a 2.5" face mill right into my soft jaws. It completely locked the spindle and let out a deafening scream. It was the belt slipping on the pulley. If I'd been using a timing belt, I'm guessing it would have snapped, or worse, spun the spindle around my tool holder until I came out to check on it. The V-belt saved my bacon once and it probably won't be the last time. Just my $0.02.

Ken

[Bob La Londe]

All,

I've been running ArizonaVideos belt drive for a few years now and I can say without a doubt that my machine would not be in use at all without it. It's truly been night and day where before I'd sit next to the machine and count the seconds it had been running at 3K rpm. Now the only thing I stress about is the coolant running dry during a run and I don't worry about that much. As far as the V-belts go... Yesterday I managed to drive a 2.5" face mill right into my soft jaws. It completely locked the spindle and let out a deafening scream. It was the belt slipping on the pulley. If I'd been using a timing belt, I'm guessing it would have snapped, or worse, spun the spindle around my tool holder until I came out to check on it. The V-belt saved my bacon once and it probably won't be the last time. Just my $0.02.

Ken

Well, here is another 2¢ worth. Connect the trouble output from your VFD to the E-stop circuit. Then program your VFD to fault at just over peak current demand of your motor at full load. Then instead of screeching a belt it should just stop the machine. Of course you have to have a big enough belt and enough belt tension to be able to spin at full load. Nice thing about that is even at slower speeds where your motor doesn't have the toque it will cause it to fault instead of doing a poor job of cutting due to motor slip or worse. Fry your VFD.

I know I said I stalled a 5HP motor, but I'm guessing the belt had no issue handling 5HP. Or more likely 4HP since that's all the VFD would support on single phase input. They must have picked one rated for it. I hooked up the fault output after that. LOL.

[RustedOut]

I studied some of the commercial mills while I was doing the design of my belt drive, Bridgeport used timing belts on some models, while Fadal used v groove belts on the ones I found info on. My original design, I was trying to emulate Fadal on the use of two belts, one slack and one tensioned. I gave up that idea after deciding to just overspeed the motor and that required only one ratio. But I kept the v groove belt. I guess time will tell if that was a good decision, but I have no worry about that selection.

Bob

[Bob La Londe]

Anyway, I wasn't really challenging anybody's choice of multi V-groove belts. I just wanted to know they why of the thought process.

[mactec54]

Anyway, I wasn't really challenging anybody's choice of multi V-groove belts. I just wanted to know they why of the thought process.

It's a better choice using the Poly-V Belt, they use less Hp, run much quieter & smoother running in general, than a timing Belt, the round tooth timing Belt is not to bad for noise,& can run smooth but still has no need unless you need precision for rigid tapping spindle orientation, this can still be done with the Poly-V Belt, with a little more care with the design

I have used them in Bridgeport head conversions for 20 years Photo attached, the drive in this photo can do rigid tapping

A source for Poly-V Belt pulleys is automotive pulleys even junk ones can be used, but you have to check that you can get e belt to match the pulleys & your needs

They are very easy to custom make to fit your needs

[Bob La Londe]

I think people throw "better" and "best" around a little to easily.

[hjl4]

Bob, my two cents, go with timing belt. The efficiency is just as good as v grooves. You will never notice the HP drawback unless you are into the 10K RPM range.
Why I would go with a timing belt? Because if one day you ever decide to play and try your hand at rigid tapping, you know you have the right stuff to keep the spindle in time with the encoder. Not only are timing belts easier to find, they are capable of greater drive ratios then v-groove belts, without the need of a belt tensioner.
P.S. I too have stalled my 5 hp Tree mill, and the timing belt handled it no prob.

[Bob La Londe]

For me its a cost and time equation. When I take the head apart I want to be able to put it back together very quickly. I am fortunate in that I have other mills, but I don't want to have one down for days, and the others tied up making parts for it. I never had issue with ths noise level on the Hurco. Like I said, if Dave's kit wasn't six months out I woud just buy his and be done with it. Then I could be swapped out and running in a couple hours. I mostly wanted to know if there was an over riding problem with using a timing belt, and it appears there is not.

While rigid tapping sounds wonderful, its not something I would likely do with a regular 3 phase spindle motor. I might if I went to an AC servo spindle. Spiral thread milling meets most of my odd size tapping requirements, and 95% of the rest is done on the drill pess with a tapping head.

Again for me its about cost and time. (mostly time)

Look at the cost of billet. Its not much cheaper than a complete pulley.