Loose belt or stall "management"??

[John C Bush]

Been turning larger bowl blanks~~20+" round ~~12+" deep--30#+(??). The PM 4224 handles the mass fine but as I turn the corner I frequently catch an edge and the blank stops and I hear an apparent belt squeak and when released the blank spins up to speed immediately. I tightened the belt as much as I could without using a prybar and it feels quite tight between the pulleys. I keep arbor speed at the mild earth tremor point and speed up as balance improves. Generally use a 5/8" bowl gouge but have been Robo Hippying it with a large scaper as well. Both have the same result if I get too greedy or catch a prominence. Is this standard ops, bad technique, low speed, worn belt?? Having a blast making bigger bowls and want to learn optimal techniques.

Another thought, I have leveling casters on the legs for mobility ease and they raised the height ~~2 3/4". It seemed that arm position wasn't ideal so I just made brackets to still use the casters and lower the height 2 1/4". haven't turned anything yet--paint still drying-- so maybe tool angle will make a difference. Thanks, John.

[Dwight Rutherford]

Are you using the lower speed belt set-up? How does the belt look, is it worn? Don't think you should be getting frequent catches. Is your tool rest set so your gouge or scraper is cutting at spindle height?

[John C Bush]

Belt is on low range and cutting at spindle height. Belt is flat with grooves and feels intact--rubber has no noticeable abrasions/ loss of material. No chip remnants stuck in belt. I get very little deflection when "tweaking" the belt so it is tight. I will see how the height and tool angle helps. It will help my shoulder and arm tightness for sure and help with more relaxed posture. The bigger the chunk of wood the more tense I get.

[Dwight Rutherford]

The way I was taught to adjust lathe height is to have the center point of the spindle at a height equal to or slightly higher than my elbow when standing erect.

[Reed Gray]

I haven't met a lathe yet that I couldn't stall, which is probably a good thing safety wise anyway. You have to learn both yours and the lathe's limits. Most of the time, my stalls are not from catches, but from trying to hog off too much. If you add to that, the larger the diameter is, the easier it is to stall, and the size of pieces you are turning are pretty big, so way out on the edge, if you try to take off too much, it will stall fairly easily. It takes a lot to wear out one of those grooved belts. I still have the original on my Robust after almost 10 years.

Robo hippying..... Love it. I don't use scrapers wider than 1 inch any more. There is no added 'stability' that I can tell, and with the wider ones, there really is a tendency to get too much metal into the wood at one time...

robo hippy

[Allan Ferguson]

Very good advise from Reed. Relax, lighter cuts, enjoy more.

[John K Jordan]

...I tightened the belt as much as I could without using a prybar and it feels quite tight between the pulleys. I keep arbor speed at the mild earth tremor point and speed up as balance improves. Generally use a 5/8" bowl gouge ...

I'd worry about over-tightening for one reason - I remember a thread where someone destroyed their lathe bearings by aggressive belt tightening. I wish I could find the thread - I think it was on a Jet 1642 but it might have been on a PM. IIRC the resolution was the proper and recommended tightening was to loosen the motor pivot lock and let the weight of the motor supply all the force to the belt, then tighten. I remember checking all my lathes and being glad none were over-tightened.

I see these instructions in the 4224b manual on page 20 "Loosen lock handle (A) and lower motor to tension belt. Be sure that the Poly-V grooves of the belt seat properly in corresponding groove of sheave. Do not overtension; a very light pressure on the tension handle (B) is adequate to prevent belt slippage." It must be important - they repeat this on the next page: " Loosen lock handle and allow motor to lower. Do not overtension; a very light pressure on the tension handle is adequate to prevent belt slippage. " Again on page 22: " Check belt; it should be snug but not overly tight."

That said, if the belt is in good condition I suspect technique. One thing I've found helpful is a smaller gouge - it has a smaller "bite" and is less likely to grab the wood. That and very sharp, of course, and light cuts riding the bevel. If the chunk is irregular so the bevel cannot yet be riding on the wood I still present the gouge as if the bevel is there.

Have you seen the videos with Lisi Oland turning big bowls - some are 3' in diameter! She uses long-handled tools with small cutters used as scrapers, just as usually used on the inside of a hollow form. This video shows her in action. I think this is one that shows how she uses a chain saw to core! https://www.youtube.com/watch?v=1PMEJ7rirso ...

If you have another bowl turner nearby, maybe a joint turning session to compare techniques would be helpful.

JKJ

[John C Bush]

Thanks to all for the help. The new mobility rig is installed and the lathe height is lowered ~2 1/2" so I will see if "reposturing" me helps.

John, I was concerned about over tensioning as well. The bearings seem massive and the pulleys are between the two but I will finally read the directions and follow the rules! I don't have, and haven't tried, any long handled, heavier roughing tools so I may be interested in your Oland tools. PM me with info if you wish. My brother went to Maryville College, married a gal from there and lives in Bristol now. Beautiful part of the country> Thanks for you help.

[Bill Boehme]

Motors aren't designed to handle large overhung loads and tightening the belt like you say you are doing is going to wear out the motor bearings as well as wear out the belt. In fact, the belt may already be worn out if it slips easily. Belts, whether standard V or Poly-V type run on the sidewalls of the belt. When they are worn to the point that the belt is running in the bottom of the grooves, they no longer have the ability to haul much of a load without slipping. A slipping belt will also glaze the rubber and ruin a pulley from overheating it. Poly-V belts are intended to have very low tension. You ought to be able to grab the belt at mid-span between your thumb and forefinger and flex it about a half inch using only finger pressure ... no arm pressure. My guess is that your belt is already worn out from over tightening it. Hopefully, your motor bearings are still OK. As long as the belt isn't flapping from being grossly loose, it is hard to under tension a belt that is in good condition.

If you are still having problems after replacing the belt and using proper tensioning then I would suggest that your turning technique needs tuning up.

I have accidentally squealed the belt on my lathe when I forgot to check the clearance between the piece and the tool rest before starting, but I've never stalled the motor. If you stall the motor that is an indication that the belt may be too tight.

[John K Jordan]

Thanks to all for the help. The new mobility rig is installed and the lathe height is lowered ~2 1/2" so I will see if "reposturing" me helps.

John, I was concerned about over tensioning as well. The bearings seem massive and the pulleys are between the two but I will finally read the directions and follow the rules! I don't have, and haven't tried, any long handled, heavier roughing tools so I may be interested in your Oland tools. PM me with info if you wish. My brother went to Maryville College, married a gal from there and lives in Bristol now. Beautiful part of the country> Thanks for you help.

I grew up in western PA but have been living mostly here since the late 60s. We love it - great weather (in 70s today), living within an abundance of hardwood which enhances the wood turning experience, low taxes, low property costs, low gas prices, low population density (compared to a lot of the country), high-tech science and engineering corridor, arts, crafts, museums, national and state parks, lakes, mountains...and good people! I have a farm with llamas, alpacas, horses, honey bees, etc, etc!

I'll send a PM about the tools.

JKJ

[Leo Van Der Loo]

The Laguna manual states that the belt should be tensioned with very little deflection, ⅛” to ¼” with moderate thumb pressure.

I certainly would not worry about the bearings in the headstock, they can stand much higher loads on them than the belt could possible put on them.

However there is the motor shaft that is sticking out with no bearing on the end of the shaft to carry the load, and you could well be putting enough of a load on it that it might bend, depending the size of the motor shaft of course, but there was a case of motor spindles breaking on a lathe with a 5 or 6 speed pulley on them that brought the tension quite a way from the motor bearing and the shafts would bend and eventually break when over-tightened.

This is at page 27 of the Laguna manual

Laguna belt tensioning.jpg

[Olaf Vogel]

Have you seen the videos with Lisi Oland turning big bowls - some are 3'' across! She uses long-handled tools with small cutters used as scrapers,
JKJ

For removing a lot of material, very quickly, this is a great solution.

Today I did two 30 in. "bowls" about 12" deep in a couple of hours each.
One "chisel" is a 1/4" cutter in a 48" bar.
The other is my Thompson 3/4" gouge, in a 48" steel tube (allows me to work a fair ways off the tool rest).

I use the long tools, because it reduces the physical stress on my arms.

(BTW - I would NOT advise wrapping your fingers around the tool rest, like in the video.)

And as Robo said, yes, this allows me to stall my lathe as well (4 belts and 5 hp) and its a good thing they do slip.
His advice is spot on, learn the limits and figure out how much you can cut without stalling.

[John C Bush]

Thanks again!!

I spun a couple of 22" chunks of London Plane-neighbor said it was a sycamore but the grain is plain--mainly-- and after all mechanical considerations and adjustments it's clearly technique. I lightened up my touch and kept the tool from moving forward into the void as the lathe rocked with the imbalance and had far fewer catches and stalls. Lowering the lathe, posture and mostly relaxing are key. Moving up on that learning curve!! I think heavier and longer(for inside of bowls) roughing tools will help. Need a longer curved tool rest as well. It's interesting that as I turn larger pieces I'm finding it is really all about the wood! Large bowls with uninspired grain and character are still fun but the modest sized bowl with outrageous character are even better. The art seems to start at the wood pile. My next learning curve. Thanks again for the help.

[Reed Gray]

With the London Plane, which is a Sycamore or Sycamore is a Plane tree, in order for the spectacular rays to show, you have to quarter saw it, so that means if you cut and turn like most bowls with the bark side being the bottom of the bowl, it will be very plain. However if you cut it so the pith side is the bottom of the bowl you get spectacular medullary ray patterns. It also spalts very nicely...

robo hippy

[John C Bush]

Thanks Reed. I'll that next.