How smooth should a table saw start?

[Rob Mitchell]

I have a new General 650, a very nice saw. While I'm sure it was set up perfectly at the factory, I had to remove the motor to get it into my ground level basement.

I put the motor back on, and set it so the drive pulley's are square to each other and inline. When I push on the belts in the centre, they go in about 0.75".

The saw runs with just a whistle from the blade and no vibration. However when the 3HP motor first starts, there is a fairly loud 'whump' sound and then it immediately spins up to speed. The motor is 220V on a 40A circuit.

Strangely enough, if the motor has *just* stopped and I restart it, there is no whump.

I know that motors draw high current when they start up so I expect some 'kick' but is this normal? Is there some way to soften the startup with a capacitor say?

Rob

[Edwin Pawlowski]

That's because of the check valve in the whump circuit. The saw has to be shut down for a while for the reservoir to refill with more whump. A whumpless start is OK as long as the whooosh did not drain down, a rare occurrence.

[Mark Howell]

I noticed alot less 'whump' after I replaced the belts with link belts.

[Mike Marlow]

This is only true with the economy whump circuit check valves, and it's because they employ a simple one way valve. Better designs typically employ a feedback circuit that modulates in direct proportion to the remaing coeffiecient of the inverse propogator and resolves the issues of a large delta between the static whump value and the anticipated whoosh values as determined by the rotational latency divided by the height of the blade.

[Swingman]

I have always been of the opinion that you don't really need link belts on a high quality cabinet saw ... the General 650 should certainly qualify in that regard.

My Unisaw does the same thing. The startup thump is not uncommon on higher powered saws ... I recall hearing that distinctive sound back in woodshop some 40 years ago. This is not something to worry about, or go to extra expense to "cure", IME.

[kwoodhands]

The belt is causing the "whump". When the saw has run a while, the belts are stretched a bit and the whump is not felt on startup. Forget about it, probably after a few hours of use the whump will be less noticeable. It may dissapear altogether. mike

[Leon]

Oddly this is normal. Norm's TS on TOH does it. Mine does it and most every one with a Cabinet saw with 3 V-belts sees this happen. Basically you have plenty of power available to the motor and it starts INSTANTLY. Jet and I tried to remedy this on my TS and they sent me a new motor. I started the new motor prior to mounting to be sure that it turned in the correct direction and noticed that this thing does not wind up so to speak like the smaller 110 volt models. When I flipped the switch the motor was instantly up to speed. With than in mind, starting the belts and blade from a dead stop to instantly on, makes noise. You may notice that as you use the saw during a typical sawing operation and the belts warm up that the Bang will start to subside until the belts cool off. I do not know if the remedy is to loosen the belts or make them tighter. I believe loosening them will help. Many use link belts to eliminate or help eliminate the problem. Seems to me that the link belts would fit some what looser how ever I could be wrong.

[Leon]

I remember back in the late 70's when I had gone to work for an Olds dealer in Corpus Christi the guys sent me up to turn on Bertha. I knew something was up, no Bertha was not a woman, Bertha was "The COMPRESSOR". This thing must have been a 5 or 6 hundred gallon monster with a 20 hp motor. The tank was about 4' tall laying down and 7 or 8' long and the compressor was in a rather confined low ceiling room above the parts department. Just before I grabbed the lever on the electrical box I noticed 2 ropes tied to the lever going down through a hole in the floor and down to the parts department below. I grabbed the lever and pushed it up. With a loud explosion sound the monster started up and as I got back up off the floor I checked my pants for a deposit. When I came back down stairs a crowd was gathered to see the expression on my face and they then indicated that the ropes on the lever were used to turn the compressor on from down stairs.

[Robert Bonomi]

But *that* one is an option only if you have the 3ph motor installed.

[Mark Howell]

I replaced the belts not to reduce the startup jolt, but rather to reduce vibration.

I agree, it's more of an annoyance than a problem...

[google]

I've never looked at a cabinet saw too closely. But on my contractor's saw, the motor pivots on a hinge and the weight of the motor tensions the belt (I think this is pretty standard). Anyhoo, when I first turn the saw on the torque and stretch of the belt cause the motor to jump a bit. Is that the whoomp you're hearing? I wired my motor for 220. I don't have those fancy three-belt pullys and it'll chirp the belt when I have 3/4" of stacked dado on the arbor. :)

[Rob Mitchell]

Guys, I'm in Canada. Whump is a proper SI unit of measure.

milliwhump, centiwhump, deciwhump, WHUMP, decawhump...

[Leon]

Different animal.

[Duane Bozarth]

That, of course, depends on how hard you push... :)

Sounds like the belts may be a little loose to me. My PM 66 has never made any unusual noise on starting that I recall from the beginning...5 hp/3-grooved matched belts.

[Stephen Young]

Here a whump, there a whump, everywhere a whump whump - This old tablesaw had a noise, E I E I O!

[david zaret]

i have a one year old 650, but with a 5 HP motor. i get the same whump. no worries. runs smooth, whump is normal. great saw.

just out of curiosity, how flat is your table top?

enjoy.

--- dz

Rob Mitchell wrote:

[Old Nick]

On Wed, 02 Feb 2005 02:34:19 GMT, david zaret vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

It's got a ruddy great whump in the middle............

[Rob Mitchell]

Well, I wouldn't be able to measure it to any precision, but when I looked at light glaring off of it, there were no noticable undulations. The top was a thing of beauty, and probably the biggest reason that I bought the General over an import 'King' that I was considering. The King table was already rusting on the edge.

Why, did you have a problem? My General had a hidden wiring problem which I discovered when I removed the motor.