Charlie_6ft

Crescent Machine Co. Bandsaw (Patent 1905) Advice

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Hi, I am eyeing off an old bandsaw (I think it's about 32") and have thrown a few queries to Matty (L.S. Barker1970) but thought I would stop pestering him and share my questions here in the event it may help others. The saw is about 350klms from me so to daylte I have relied on pictures and a multitude of questions to the owner.

Q1. From the pics I have been provided it looks like at the very least it'll need new vulcanized rubber on the idler and drive wheel. Through a query a year or two ago someone mentioned a place in Goodna (Brisbane) that charged about $250, but can't find the info anywhere. Does anyone know where I may be able to get the wheels re-done in Brisbane?

Q2. I am told it was working fine last time it was used but has just been sitting in a shed for a while (it belonged to an ex-boat builder). With that said, I may need to repour the babbitt bearings, I did a quick Google and there doesn't seem to be a shortage of people in Australia who can supply the lead based babbitt metal. But who in Brisbane could someone recommend?

Q3. The motor on the saw is a Crompton Parkinson 2.75HP Three Phase motor. On the motor plate it has 940RPM. This sounds pretty slow? I would be replacing the motor with a Single Phase 3HP motor (Cheaper than a VFD) which looks very straight forward given the foot mounting assembly. What RPM would I seek in a motor as a replacement? I have read anything from 1400RPM to over 3000RPM!

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A 940 rpm motor would yield around 1500 inches per second blade speed over 32" wheels, with no reduction. I'm sure there are pulleys involved, you will need that ratio to determine the appropriate motor rpm. Is the power grid in your part of the world 50hz? If so, that 940 rpm rating will likely be listed as 1000 rpm on a modern motor. It used to be common to see full load speed ratings, now I see no-load ratings more than not.

Regarding the wheels, would modern tires like these work? I'm not familiar with that saw, but most folks seem to prefer urathane these days. Soak them in hot water and they will stretch over the wheels without too much effort.

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Thanks chaps,

Q1. I found the people today I was looking for regarding vulcanized rubber services. They are called Queensland Rollers & Liners (Cobalt Street, Carole Park QLD) over near my part of the world and advised me that it would cost between AUD$265 - AUD$300 ex GST. There are blue or orange polyurathan options but think from America which with postage may end up nudging the price up.

Q2. Babbit bearings - It may not be required BUT will find out in about 3 weeks when I pickup the saw.

Q3. I think it may have had a conversion at some point regarding the pulley (see pics) and is driven by 2 x V-belts. I've got the choice out of 4 Pole (1400rpm) or 2 Pole (2800rpm) both 50Hz for a Single Phase motor. OR I get a VFD and I make use of it being variable speed and can add in soft start, etc. BUT regardless I'll get all the figures and then run it through an RPM calculator to figure out the speed.

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I would go with the 2 pole motor, unless you plan to change the pulleys, too. Doubling the speed will increase heat build-up from friction. It will certainly work, but require modified cutting practice to get the desired results.

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I like having a VFD on my big bandsaw.  Listening to the slow windup to speed is worth it, alone.  I can also run it under, or over normal speed.  We ran it 10% over, for three or four hours at the time, and nothing got even warm to the touch.

Babbit bearings are the smoothest running bearings in existence, until they need to be repoured.  I've never owned any, but have had my hands on such machines running.  With no personal experience, I have no idea how long they last.

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19 hours ago, Tom King said:

I like having a VFD on my big bandsaw.  Listening to the slow windup to speed is worth it, alone.  I can also run it under, or over normal speed.  We ran it 10% over, for three or four hours at the time, and nothing got even warm to the touch.

Babbit bearings are the smoothest running bearings in existence, until they need to be repoured.  I've never owned any, but have had my hands on such machines running.  With no personal experience, I have no idea how long they last.

Hmm ... perhaps I re-visit this idea. A VFD is about $50 more expensive than a motor replacement BUT am keen on gentle startup. Is it purely just to variables you need to set:

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The VFD will want to know the "normal" speed of the motor you pair it with. Even though the drive varies speed by changing the frequency, it will likely have a display scaled to RPM or % of nominal speed, so it needs a known point to scale from.

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The VFD's I have will do many more things than I have even learned how to do with them.   I'd have that old motor checked out first.  If you need to replace the motor, it probably wouldn't make sense to buy both a new 3-phase motor, and a VFD.

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Regarding the babbit bearings: as newly poured bearings, there typical are removable shims between the upper and lower halves of the bearing.  These shims can be changed to thinner or thicker ones, or be removed or replaced with fewer or different ones, or to a lesser extent the fit can be adjusted by the degree to which the bolts are tightened.  If it comes to repouring, it is not all that difficult.

Regarding the motor: is a phase-convertor a viable option?  Can you simply change a pulley or two to achieve the desired speed?

Regarding the tires: if the wheels themselves are not crowned then the tires must be crowned after mounting.

Good luck; it is well worth the effort.

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