Unisaw Question

[Greg Bender]

To everybody with a 1 to 5 year old Unisaw I ask,Should my recently acquired Unisaw with a Weg motor start with a jerk? This is my first cabinet saw and I guess I'm accustomed to the way my Contractor's saw started.There seemed to be a very slight ramp up to the motor starting.This unisaw starts immediately with a thud.Shakes or rocks anything that is on the saw table.It has been sitting around for several monthes,don't know if that adds a problem to the performance of the saw.The saw was used in a commercial shop for a year or so and has a little use on it.By the dust in the bottom it seems like all they cut was MDF.
Also,it seems like the fence is closer to the blade on the outfeed end of the saw and was wondering if the fence rail had enough play in the mounting holes to adjust that out.I'm borrowing the setup to measure the alignment tonite but figured I ask ahead of time.I put it together by myself so I need to go back and adjust and tune a little.I did get the rail close to the gauge height without having the delta supplied gauge.
Well,any help or suggestions will be much appreciated.
Thanx,Greg B.

[Keith Harrell]

Yes my Unisaw does and it happens more in the winter than in the summer with the belts getting cold. You may want to check the belt tension but the thud should become less about the third time it turn on during the day. The motor has a lot of torque which is nice if you have to restart a cut in the middle of a board. Mine is a 3hp and is four years old and has never failed to cut any board I put into it.

[Greg Bender]

Keith,
would it make a difference to swap out the regular belts and install link belts.I ask but that seems like it would be expensive if there was no gain to be had.I had links on my Contractors saw but it was a single belt.So far I've had no problem cutting anything with the saw and the blade on it needs to be sharpened.Thanx for the reply
Greg

[Dan Forman]

Mine thumps pretty good too at startup.

Dan

[Ron Bontz]

Mine thumps a little as well. The fence sounds like it just needs adjusting. How depends on which one it is. Best wishes.:)

[Frederick Rowe]

One more Unisaw starting with a Thump! Mine was brand new. The belts had taken an oval shaped set. I replaced with link belts, and smooth start and running now.

[Keith Harrell]

I'm not sure if different belts would help as I just got use to it. The link belts seem like they would offer some help as they flex more at startup. I know my saw doesn't do it after a few starts. It did bother me at first but now I guess I just don't notice it anymore. Let us know if you try the link belts.

[Greg Bender]

Thanx everybody,
I can live with the thump as long as I know I'm suppose to have the thump.I will try the link belts as they sure smoothed out my other saw.

Frederick,
do you remember how much link belt it took to replace all three belts.

Ron,
as far as fence alignment,the blade looks to be parallel with the mitre slot,but when the fence is locked in position ,it's not parallel with the mitre slot.That is whyI was wondering if the rail mounting bolts had enough play to get that kind of adjustment from it.I'll give it a try.
Thanx again,Greg

[Michael Drew]

Mine is a 95 model but it started with a resounded thump when I first got it. I swapped out the V belts to link belts and now it starts smooth as silk. The one draw back is that the link belt is slightly taller than the V’s and I lost roughly 1/8” of arbor lift because the belts will rub on the table. I’ll also add that the machine runs extremely smooth now. Before it has a slight vibration. I’m sold on the link belts now……..

[kenneth kayser]

Thanx everybody,
I can live with the thump as long as I know I'm suppose to have the thump.I will try the link belts as they sure smoothed out my other saw.

Frederick,
do you remember how much link belt it took to replace all three belts.

Ron,
as far as fence alignment,the blade looks to be parallel with the mitre slot,but when the fence is locked in position ,it's not parallel with the mitre slot.That is whyI was wondering if the rail mounting bolts had enough play to get that kind of adjustment from it.I'll give it a try.
Thanx again,Greg

For proper table saw operation is is mandatory that the blade be parallel with the slots. This alignment must be done with a DTI or straightedge. Check at the same spot on the blade, front to back. The fence can be parallel to the slots or the back end moved away from the blade a few thousandths. If it is not parallel, however, it will not work on the other side of the blade.

[Michael Drew]

Thanx everybody,
I can live with the thump as long as I know I'm suppose to have the thump.I will try the link belts as they sure smoothed out my other saw.

Thanx again,Greg

Greg, although the "thump" may be common, and considered normal, it is not a good thing to happen. That thump is slack being suddenly taken up by the motor as it comes up to operating speed. Unless a motor has a soft start (ramp up) function, motors come to speed instantaneously after the windings are energized when the contactor closes. This will cause premature motor bearing failure. I'd encourage you (or anyone) to check belt tension and pulley alignment if their saw has this "thump". 240V motors are pretty spendy to replace.

Many, many years ago, matched belt sets could be bought. The sets were machined from the same blank. This is not the case anymore. It has become a very big problem in the industrial world where large motors and machines with multi-belt configurations. Most plants have gone to wider gang belt applications to eliminate multi-belt pulley arrangements because of poor belt tolerance matching. It is this reason that I went with the link belts verses V-belts.

[Greg Sznajdruk]

I'm not sure the thumps is a result of slack in the belts. but rather the fact that the saw sits for extended period of time. The belts take a set around the pulley and this deformation is what causes the thump. When my saw sits for a week or so there is a thump the first start. As I use the saw the thump disappears and of course reappears after the saw has sat for an extended period of time.

Greg

[Paul Atkins]

We used to have a 3 horse Unisaw that was 240v single phase and a PM 66 5 horse 3 phase. The Unisaw ramped up a bit to full speed, but the PM was on right now. I always thought it was because of the 3 phase rather than the h.p. The thin kerf blades came up to speed faster because of mass too, I thought. Another thought is to check the pulley set screw and key to see if they are tight.

[Bruce Page]

I remember reading that link belts were not good in multi-belt applications because of length variations in the link belt design. Is that no longer the case?
I wouldn’t mind converting my Woodmaster DS to link belts. Luckily, my Unisaw does not thump.

[Jack DuBois]

I'd like to make a couple comments about this unisaw motor thread. Sorry in advance for this long post.

Most general purpose industrial motors found in the home are single phase capacitor start AC induction (non-synchronous) motors. This is true to almost all woodworking motors. The capacitor is used to generate the magnetic vector necessary to get a single phase motor to start spinning (it wouldn't spin otherwise). Once it is spinning the cap is no longer necessary and so often is taken out of the circuit with some type of speed controlled or electronic switch.

These motors are characterized by having a high starting torque and very little slip at operating speed. This high starting torque is what creates the "thump" on startup. Most table saws have very little rotational inertia (unlike a bandsaw w/ cast iron wheels for example) and so the blade accelerates very quickly. The higher the HP of the motor, the higher the starting and running torque so cabinet saws have more tendency for this "thumping". See motor torque-speed curves here (http://www.electricmotors.machinedesign.com/guiEdits/Content/bdeee11/bdeee11_7.aspx) (a typical motor 1phase motor is Design A).

If you want to control the spin-up speed you'll need to get a motor controller ($$$) or perhaps you could change out the capacitor size (me thinks smaller would reduce startup torque with no impact to running torque) - but this is tricky business so don't go experimenting without a lot more research...

Now for multi-link belts. These belts cannot reliably be used for high pulley speeds or high HP applications. A ML belt is good for <<1HP and <4500fpm typically. Usually the 4500fpm is not reached in a table saw b/c the motor speed (3450rpm) thru a 1.25:1 ratio and a 3" pulley is well below that limit. However, the low amount of power it can transmit means it often will act like a clutch on startup - i.e. it will slip with the high starting torque of the motor. This slipping means the saw arbor spins up slower - no thump. But this slipping is not good. It means the belt and pulleys will wear out faster and the peak torque from the motor will be limited not only during startup but running as well. So you have a big high HP motor that you cannot fully utilize when plowing wide deep dados...

The vibration improvements appear to come from the lower natural frequency of the ML belt (this is just my theory, I have no proof). It seems the Fn of the belt is traversed quickly on startup and is not excited elsewhere in operation. Whereas a typical V-belt might actually run close to the Fn and thus cause some vibe.

To rule out any other reason for the thump, check all the bolts, belts, pulleys, keys etc to make sure nothing is loose. The thumping should not cause the bearings in the motor or the arbor undue stress. Besides, most saws have pretty low starting cycles over life. What will wear out bearings really fast is too much tension on the belts. Put only enough on to prevent slipping both at startup and running. It doesn't take much as V-belts have a unique and useful tendency to climb into the groove as the torque goes up, thus increasing the ability to drive that torque. In a sense it naturally increases the "tension"... I have a Browning Sheave engineering manual around here somewhere so if you want formulas and belt tensioning procedures I can supply...

Hope this helps a little.
Cheers,
Jack-

[Bruce Page]

Jack, welcome to SMC.
Nice information in your first post.

[Tony Bilello]

Well Jack, even on the outside chance that you didn't know what you are talking about, most of us would believe you anyway. Well stated and very authoritively written.
Oh yeah, and......

Welcome to the forum and thanks for taking the time to explain it all.

[Jack DuBois]

Thanks guys! I'll help where I can...I'm renovating an old Boice Crane 3500 Monomaster Table Saw from the 50's/60's so I've been doing lotsa research on motors, sheaves, belts, riving knives, bearings etc. I think I'm going to adapt the latest Unisaw riving knife/guard/pawl system onto this old piece of 'arn. I'll let you know how it goes once I get into the meat of it...

Oh - Bruce, you asked about multiple link belts used together? Yeah, that's a bad idea because of exactly what you mentioned. The length tolerance on those is pretty bad.

[Greg Bender]

Well,first I have to say Thanx for all the info and personel experiences with the unisaw.I will say that my fence was out on the parallelism.Right now it is +.001 away from the blade on the outfeed end which is about right.I get a very slight drag/small ring as the board passes the far edge of the blade.I also made a white oak L-bracket tied to the edge of the saw through the 7/16 bolts on the saw table.The bracket supports a 1.75 inch thick maple bench top that I ripped to 27 inches by 54 inches.I made the legs out of some 80/20 extruded aluminum.
As far as the thump,you can see that the belts have a memory kink in it from sitting around so long.From the conversation link belts are not the fix or are they.I never thought about the tolerances as all my old tools had single belt drive.I will go through everything underneath and make sure all is tight.
Last but not least,welcome Jack to SMC,very informative and well written post that much appreciated.How many of the unisaws here have WEG motors and have they been reliable.I had expected to see a different brand , leeson?, but was surprised.I work for IR and we work with 50 hp to 450 hp WEG's and they have there idiosyncrasies for sure.
Jack,where could one find out what range of start up capacitor would reduce the start up torque and not create another problem.
Thanx again,greg

[Jack DuBois]

Greg, good Q. Truthfully I'm not totally sure. And I'm not sure I'd play too much with it until you understand more about the particular motor winding and operation. For example, if the motor does not disengage the capacitor after reaching some speed, then it is called a PSC motor and you have to be very careful in cap sizing or fear overheating the motor windings due to excessive current draw.

If it truly is only a capacitor start motor, then it implies (i.e. assumptions!!) the capacitor is removed from the circuit after starting. In this config playing with the capacitor is less risky. To reduce the starting torque, you could reduce the capacitor size (or significantly increase it, but that's much more expensive solution). Not that I'm condoning this, but if I was feeling adventurous, I'd go radical, say 1/4 of the value and see what happens. I'd keep an eye on the current and might even o-scope the input or motor phase windings to check for harmonics... And keep your ears open! Listen for humming or buzzing (that's bad).

Basically, if you remove the capacitor altogether there is no magnetic vector to start the motor. It will humm angrily and draw huge amounts of current, quickly self destructing without turning the shaft at all. This is analogous to stalling the motor during operation - bad stuff. But you're taking advantage of this property to alter the starting torque. The closer that cap is to zero, the less starting torque you should have and the slower it should spool up.

Play with the capacitor size until you find a happy medium between BAM - started and huuummmmmmmmm - whirrrrrrrr - started. Note the excessive "m's" I put there? you don't want many of those, maybe just hum - whirr - started.

As I said, if it's a true start cap only, then the full speed torque/operation should be unaffected.

PS: we're all big boys here so if you use any of this info without thoroughly researching it, you're taking the risks entirely for your own. Maybe you could call WEG and ask them?

Cheers, Jack

[Michael Drew]

Jack,

I’m new as well, but I also extend to you a welcome.

Your logic is sound and I agree with your comments, in general. Why I am hesitant to completely agree with you, is in regards to this particular application. The reason being, is because there is such low inertia to overcome (at least I believe it is low, comparatively speaking to other industrial applications I have experience with). Considering the drive ratio and relatively light mass of the arbor and a 10” blade, I just find it difficult to believe that a 3 HP 240V motor would have enough electrical slip to be the cause of the noise that is being described here, which I know is common on a much higher horse power motor that is direct coupled. [In the plant I work, we have some 1500 HP 13.8V motors directly coupled to speed increasing gears that sound as if a hand grenade went off when they start.] I attributed this noise in my particular saw to belt creep or slip or one of the belts being excessively over tensioned creating an unequal load on the motor sheave and bearing (as one belt was significantly shorter then the other two). I am by no means an electrician or EE, but have spent the better part of my life working on this equipment. Having said that, I just haven’t experienced this sort of common motor thumping in similar applications as our subject table saw. But to be honest, I have not consulted our engineers either, so I would love to hear your thoughts, especially now that I’m very curious after reading your comments. Do you really think it is possible that in this application (table saw), provided belt tension is correct and no belt slippage is occurring, that we should be hearing a noticeable motor thump from an inrush of current? I am not trying to be disagreeable sir, and sincerely want to understand what is occurring. You sound as if you can explain this in a manner that I (and assuming others) can understand.

I would also like to hear more from you regarding link belts. I ask because I measured mine with a belt gauge and they were all within 1/16” net difference in length. When I adjusted tension, I used the force deflection method and a tension tester set to 22 pounds. I used the Force Deflection Table in my Audel Millwrights and Mechanics guide, edition # 5. (9.5” – 16” diameter, 1741 – 3000 RPM, 27.8 – 18.5 pounds for new belts). I have not used these belts before and was somewhat hesitant, but pleased with their performance. After reading your comments, I’m now wondering if I set them incorrectly and am experiencing excessive slippage. Please advise. I don’t want to destroy my pulleys.

And if it wouldn’t be too much trouble, could you also comment on the mechanism that is used for soft start motors such as some of the larger router motors? Do they achieve this through capacitance?

Thank you, and again, I am not trying to be disagreeable, but simply want to understand. I would enjoy reading your explaination and conversing with you on many more related topics.

[Dave Lehnert]

Thanks guys! I'll help where I can...I'm renovating an old Boice Crane 3500 Monomaster Table Saw from the 50's/60's so I've been doing lotsa research on motors, sheaves, belts, riving knives, bearings etc. I think I'm going to adapt the latest Unisaw riving knife/guard/pawl system onto this old piece of 'arn. I'll let you know how it goes once I get into the meat of it...

Oh - Bruce, you asked about multiple link belts used together? Yeah, that's a bad idea because of exactly what you mentioned. The length tolerance on those is pretty bad.

This is interesting. I was just about ready to use link belts on my JET cabinet saw because of the different length issue. I have the original V belts on my saw and all 3 belts are different lenghts. One can be tight the other loose.
So if this state is not good for the saw what is one to do??

[Jack DuBois]

Michael, no offense taken whatsoever. I also encourage a healthy discussion...

Sounds like you've got a lot of really great practical experience with big industrial drives of the sort that most homeowners never get to see. Cool machines those... Also sounds like you know a thing or 2 about belts, not too many people will reference a handbook and get out a force gauge to set them up.

But you asked a lot of Q's and I'll answer to the best of my ability...

First, link belts: I do not have any direct experience with them. In fact I've been quite leery of them because of the HP and speed limitations. Plus, they don't engage the sheave in the same manner as a proper V-belt, so I'd be worried about uneven wear. In the past I considered link belts as a type of belt emergency kit - something broke and you need to keep going, throw on the link belt. Having said that, I cannot ignore the thousands of glowing reviews from real users in the woodworking community. me personally, I'd start with V-belts and move to link belts if the problem cannot be solved any other way.
It seems you've set them correctly, checked for uneven length, etc. I'm not sure how one would definitively confirm slippage without seeing clear evidence thereof such a bright spots/wear/markings on the sheaves or without doing some data collection with instruments capable of measuring speeds of motor and saw arbors simultaneously. Of course if the belt is screaming on startup then it's pretty obvious...My advice is if you're using them, keep an eye out and if it ain't broke don't fix it...

Thump sound: I don't think it has anything to do directly with the sound of the current itself rushing into the motor on startup. And as you said, barring belt slippage, loose parts, correct tension, loose parts etc. My theory is that the acceleration of such a low mass so rapidly is causing something in the Unisaw cabinet to resonate, you're hitting a particular mode shape that isn't otherwise excited. Just like when a car hits a big pothole - "thump", same thing. If the car hits a depression the same depth, but spread over 10x the distance (or much slower), it hardly makes a sound at all. That's why I think a slower startup speed should eliminate the "problem". [aside: actually, I don't think its much of a problem anyways because it's highly unlikely this is causing any damage - barring slippage, tension etc as you mentioned]. Further evidence of the mode theory - it doesn't seem to happen on every TS, cabinet or not. But I bet almost every Unisaw of XX vintage will do it! One way to rid of it is find the part that is resonanting and change it's resonant frequency or damp it. My first target would be the cabinet itself. Tape on panel damping might do wonders...

Motor controllers: I have some experience with this as the product I work on uses 3-phase synchronous permanent magnet DC motors. It very much depends on the type of motor you're driving, but the controllers I have experience with will usually take AC power & rectify it (or just straight DC power), then run it through some high speed high power FETs switching at a high frequency. By controlling the frequency, duty cycle and phase, you can very accurately control the speed, power, torque, current draw or pretty much any motor parameter you desire (with associated tradeoffs of course!) through the methods of pulse width modulation. For 3-phase DC motors, it is quite common to apply some sort of motor vector control. For application such as a table saw, we're most interested in holding a constant speed regardless of the load. AC induction motors do this beautifully because of the torque-speed characteristics. You can load them up pretty heavily with only a small drop in speed. What I find a little odd about the motors used in table saws in particular is the high amount of starting torque they seem to apply, it's really not needed (unlike say an air compressor). I wonder if a capacitor-run motor (not capacitor start) might do a better job at rated speed and give a slower startup... Having said that, it appears this high starting torque does no damage so in this bloke's opinion, although it's not optimum, it's by no means bad.

I just bought a DW618 router. It seems it uses a brushed "DC" permanent magnet motor. The speed control here appears quite simple, they PWM the AC signal to control the average current to the stator and thus the average torque/speed. My router is so new I haven't even run it up yet! I would be surprised if they have any closed loop speed control. I bet it is just open loop PWM control, which would be quite effective for the soft-start function, but would still bog down when hogging thru hard stuff too fast...

enuf blah blah 4 tonight.

Cheers, Jack-

[Michael Drew]

Thanks Jack. I am a millwright of sorts and got my start in the Navy’s nuke program…..long story for another day, but in short, I tend to over think things. I can borrow tools from work and we have a specialty tool for just about anything. I borrowed a Belt Hog laser alignment tool to check alignment too. Pretty cool little gizmo. Way over kill, but why not? It’s easier, faster and more reliable than the old straight edge method.

I too had concerns using the link belts. Too many positive comments, and my inability to find a matched set of V belts this particular size forced my hand to try them (I would much prefer a cogged type V belt). They are odd to say the least. The links are much more uniform in length than I would have thought. When observing how they make contact to the sheave, they do this by laying down in the V. Their contact patch is split into what I would refer to as “continuous” and “intermittent”. The continuous piece is in contact with roughly 65% of the upper part of the sheave walls toward the bottom. The intermittent would be from that mark down. The intermittent contact would be the link tabs. If you are interested, I can send you a section to look at if you PM me your mailing address. I have a section left over from the set I bought that I have no use for as it’s not long enough for anything I have.

I hate the way this saw runs up. I would much rather have a soft start feature like my Hitachi 12MV router. It gracefully runs up to full speed instead of angrily jumping up like the Unisaw. I’d like to experiment with this some, although I’m not terribly excited about pulling this motor out. It’s pretty cramped in the cabinet.

I am also going to corner one of the EE’s I know and bounce all this off him. He’s a wood worker too and one of the few engineers I know with common sense. He’s on vacation right now but will be back in a couple weeks. I’ll post back with what his thoughts are at that time. I’ll probably post a different thread though, so the information doesn’t get buried.

[Jack DuBois]

Cool! I'm very interested to hear what he has to say. I'll keep my eyes open for your new post.

[John Thompson]

A little late but.. a few comments from having owned a Uni-saw and seeing many in long time use in commercial shops over the years...

I have never seen a Uni-saw that doesn't thump on start-up. I believe this is due as the tranfered torque in the belts which actually causes the motor to jerk down and hit the motor stop bolt head behind the motor deep in the saw. Metal to metal = Thump! And engine in a car would do the same thing if a motor mount was loose or the rubber padding on that mount has worn allowing play.

I have noticed the thump is not as bad once the belts warm to some degree. Guessing that heat build-up in them causes expandsion and relaxing which will produce less initial jerk on subsequent starts beyond the initial start-up at the beginning of the day. I have notice more thump in a cold shop than a heated one but.. after the saw is run and the belts heat from friction.. the heated shop becomes a basic non-factor from my observation.

The thump can be reduced a little by running out the motor stop bolt with a hex head wrench to allow the smallest amount of play.. then re-adjusted the belts at that point. As already stated.. belts should not be adjusted over tight. I also expect that a small piece of rubber glued to the the head of the motor stop bolt would absord some of the thump nose but....

Bottom line... all Uni-saw's thump and 5 HP one's more than 3 HP or the older style's with less HP. I have never seen a Uni-saw yet damaged from the thump. My neighbor has a 1962 model he uses daily building outdoor furniture. Solid as a rock but... it thumps on start-up. ;)

[Brent Smith]

Two facts of life....Old Harleys mark their spot, and Unisaws thump. You can play with, adjust and/or rebuild both, you might even solve the problem for a little while, but nothing is going to change either fact in the long run.

[Michael Drew]

I’m almost afraid to comment further in this thread as I’m probably going to sound like I’m on some sort of crusade…..

I doubt the motor stop is meant to be used as a torque block. If it was, it would be in constant contact with the motor, as all torque blocks and motor mounts are. I may be wrong, but I believe the stop is a safety device to keep from getting your fingers crushed between the motor and the base cabinet after you pull the last belt off. I was glad it was there when I swapped belts, not expecting the motor to be as heavy as it is and swing down as fast as it did. My guess is that belts are too long if the motor bumps against it during start up.

As already stated, this may be common and not be an issue whatsoever, but I’d still suggest that if anyone’s saw is making any sort of noise during start up that doesn't sound right to you, that you check belt alignment and tension. If somethign sounds amiss, it generaly is.

Also, maybe my saw is the exception and not the norm, but after changing belts and properly aligning the pulleys, there is no noticeable thump or any sort of unusual noise when it starts. It just spins up and hums along.

[Greg Bender]

Michael and Jack,
Thanx for all the info and great back and forth conversation.Now that is why I come to this site.I'm also going to check with our ( IR) EE's to see what they have to ad.We work with Weg motors from 50 to 450 hp in our group and should lead to some interesting conversation.As far as resonant frequencies,that could be a very good cause of my thump.I clamped two each 2 by 2 white oak strips on either side of the cabinet diagonally and tryed starting the motor and noticed a reduced "thump".Now what I do not see is a slight lift to the blade at start up,my buddy here has a PM 66 that the blade kind of bounces at start up.I need to get into the cabinet and check all my mechanicals and belt length to see if there is anything obvious.AS a last resort I may try a smaller start capacitor and will report back.
Thanx again,very informative'
Greg

[Joe Shinall]

Mine thumps on startup and it freaked me out the first time I booted it up. Turned it off immediately and began to check everything. Quick call to Delta and found that it was normal due to the speed it starts up. It doesn't ramp up like the smaller ones because it's a "real saw" as the guy from Delta said. :D

[mark tanzi]

Greg, are you still experiencing hard starts with the Unisaw? I own a circa 1990 Unisaw, and have been searching for an answer to this question for years. In my case the hard start is VERY INCONSISTENT. One start is smooth as butter, and the very next start produces a big bang....no explanation.

mark




To everybody with a 1 to 5 year old Unisaw I ask,Should my recently acquired Unisaw with a Weg motor start with a jerk? This is my first cabinet saw and I guess I'm accustomed to the way my Contractor's saw started.There seemed to be a very slight ramp up to the motor starting.This unisaw starts immediately with a thud.Shakes or rocks anything that is on the saw table.It has been sitting around for several monthes,don't know if that adds a problem to the performance of the saw.The saw was used in a commercial shop for a year or so and has a little use on it.By the dust in the bottom it seems like all they cut was MDF.
Also,it seems like the fence is closer to the blade on the outfeed end of the saw and was wondering if the fence rail had enough play in the mounting holes to adjust that out.I'm borrowing the setup to measure the alignment tonite but figured I ask ahead of time.I put it together by myself so I need to go back and adjust and tune a little.I did get the rail close to the gauge height without having the delta supplied gauge.
Well,any help or suggestions will be much appreciated.
Thanx,Greg B.

[Rod Sheridan]

I have a Hammer B3 which has a single phase 4 HP motor and poly-v belt.

The motor has smaller starting capacitors than your typical NA motor, and has a smooth, aproximately 2 second acceleration time.

No thumping or banging...............I would experiment with a starting capacitor of half the size.................Rod.

[Stan Krupowies]

I'm not sure if different belts would help as I just got use to it. The link belts seem like they would offer some help as they flex more at startup. I know my saw doesn't do it after a few starts. It did bother me at first but now I guess I just don't notice it anymore. Let us know if you try the link belts.

Mine starts with a thump as well and I have the link belts on it. When running it'll pass the nickel test but it fails on startup.

[david paul miller]

my 2009 model unisaw has 2 belts, thumps at start up, but passes nickel test from off, run, off.

[mark tanzi]

Stan and David,

Do your machines start hard EVERY time, or is it random? The part that really puzzles me is that my Unisaw starts smoothly....truly like butter...many times. Just as often, the start is hard...actually with a JOLT...or semi-hard with a small bump....this occurence is NOT CONSISTENT at all.

If the hard starts were consistent...every time...then it would be more plausible that the suggested solutions of changing to a smaller capacitor or different belts may work. But, I am reluctant to start trying solutions because this RANDOM starting behavior has me baffled.

Does anyone have a comment on why this hard starting behavior is random? Is that what most Unisaw owners are experiencing, and if so, how could Delta simply explain this as "normal"?

I once called Delta, and a technical rep explained that due to the sine wave characteristic of AC power, sometimes the machine would see 220 volts upon pressing the start button, and sometimes less...this was his explanation of the random behavior...????

p.s. my saw is a circa 1990 machine...I believe Delta changed to a new motor for this year...or thereabouts.

THANKS ALL !!!!!!!

mark









my 2009 model unisaw has 2 belts, thumps at start up, but passes nickel test from off, run, off.