weak MKVII motor

[lahola1]

Electrical expertise needed :
I recently tried to rip some 2x4s(for the 1st time) with my 60s MKVII and it was slow going. Slowed down several times; stalled once; tripped the 20a breaker ( the shop vac was also connected to the same circuit). It had a 40T combo blade (recently resharpened) on it. Switched to a brand new Diablo 60T combo and it was no better, maybe a little worse.
So then I put the Diablo blade on my 1980 MKV (set at O) and it was still slowing down; stalled twice. Switched to the resharpened 40T; still slowing down but overall seemed a little better than the MKVII. More info: the MKVII was in my garage w/ a 20a, 12-2 romex no more than 40 feet long; the MKV was in my barn w/ 20a 12-2 romex more than 100feet from the breaker box to the barn. So with both motors being 1 1/8HP 13a motors I would think the MKV in the barn would have less power, not more.
I am no electrician so my questions are:
1) is there such a thing as a weak motor. If so, what are the causes inside that are making it weak and not failing completely.
2) I have ripped many 2x4s on my rigid 2412 120v 14a and don't recall any slowing or stalling with the same 40T blade. Is there something inherently
weaker in the SS system compared to a std belt driven tablesaw.
BTW, I fire up my MKVII today; went thru the speeds, no problem; ripped a 3/4" pine board ,no problem so it doesn't look like I damaged it ; just seems weaker than I think it should be.
Any thoughts?

[algale]

A properly maintained and aligned Shopsmith should have no problem at all ripping through 2 inch thick stock that has been properly prepared.

Regarding maintenance, are the belts properly tensioned, is the table properly aligned to the blade and is the rip fence properly aligned? If any of these things is out of whack, even properly prepared stock can bog down and stop a perfectly good motor and/or pop a circuit.

Regarding stock preparation, today's 2x4s are seldom straight enough or flat enough to be ripped without preparing them on the jointer. If you don't joint a face and an adjoining edge straight and flat before ripping, you are very likely to put a lot of sideways force on the blade and bog the motor down, stopping it and/or popping a circuit breaker.

These problems come up while ripping more often than when cross-cutting because the length of the work piece being ripped can put a lot leverage on the side of blade.

Because your 3/4" pine board ripped fine, I suspect the issue is 2x4 prep. Most 3/4" pine boards are going to already be jointed and planed. 2x4s are not.

[RFGuy]

As Alan pointed out, I would suspect belt slipping on the Mark V or Mark VII. You need a good belt that is properly tensioned to cut any thick stock on a Shopsmith. I have cut Redwood 4x4's on my Shopsmith with no problem. Having said that though, the feed rate is much slower for something like ripping a 4x4 or even a 2x4 depending on the blade. Keep in mind a 40T blade is a combination blade and is really only intended for the occasional rip because it is meant for crosscutting. Feed rate must be slower for a combo blade. IF you are doing A LOT of ripping, you really should have a 20T blade on any saw. It is much easier to change out blades on a Shopsmith saw than it is on most traditional tablesaws so really no reason not to have a separate ripping vs. crosscutting blade IMHO. After belt tension, the next thing is to make sure you have a clean and sharp blade. A dirty blade can appear dull when in reality it may be sharp underneath all the pitch & resin buildup. Lastly, a 60T blade is for cutting plywood and I would never rip 2x4's with one.

[JPG]

" 2x4s are not." ????

They are not rough sawn(i.e.they are planed), but do have corners 'rounded'(to prevent splinters embedding in carpenter's hands).

And yes rarely 'straight'.

I think Al nailed it.

So did RFGUY.

[algale]

" 2x4s are not." ????

They are not rough sawn(i.e.they are planed), but do have corners 'rounded'(to prevent splinters embedding in carpenter's hands).

And yes rarely 'straight'.

I think Al nailed it.

So did RFGUY.

Good point, JPG.

2x4s may well be processed straight at the factory. But by the time they arrive at the box store, they usually have a pretty obvious bend or twist.
Is that because the 2x4s are processed at the factory while the wood is still green? Or because they are cut from such small/young trees today that you will often see growth rings doing a 180 or even a 270 on the end grain of a single 2x4? I don't know the why, I just know I haven't bought a 2x4 in a long, long time that I would be comfortable ripping without first taking it to my jointer to remove the twist and bend.

[chapmanruss]

The blade information talked about above may be the problem. There is another consideration for what could appear as a "weak" motor. BEARINGS, if the bearings are bad they will "rob" power from the motor reducing performance. In the Mark VII and V that will include the motor bearings, idler bearings, drive sleeve bearings and quill bearing(s).

[lahola1]

All good points.
I think it's still aligned well I've built kitchen and bath cabinets with it.
I don't think the belts are slipping. I can here the MKV motor stopping and starting back up; not sure on the MKVII. Replaced the poly v belt 4 yrs ago; I believe it's set correctly.
Idler bearings were replaced 4yrs ago; all other seemed good. I haven't put too many hours on it since the rebuild 4yrs ago.
No, I will not be jointing my 2x4's to make construction 2x2s.
RF Guy, I like your 20T blade suggestion, but redwood is nowhere near as tough as pine/fir.

But back to my original question, to expand my electrical knowledge base, is there anything "IN" the motor electrically that can cause a "weak" motor?
And is the mechanical design of the SS less efficient than a STD belt driven table saw? Meaning, if all of the possible problems mentioned were corrected
but keeping the 40T blade, would the SS cut without bogging down like I can with my Ridgid table saw since the motor HP is basically the same?

[RFGuy]

I don't think the belts are slipping. I can here the MKV motor stopping and starting back up; not sure on the MKVII.

So, what do you mean by the motor is "stopping"? I interpreted that to mean a belt slip, but maybe something else is going on. Do you see the sawblade stop or slow significantly while making the cut? Or does it just go really slow? I know myself that I have had a belt slip in the past on some 8/4 cherry that I was ripping, but when I investigated I found that my belt had stretched a little from use so I had to re-tension. Once I did, it fixed it, but maybe you are seeing a different issue here.

[wa2crk]

How about front to rear table alignment. This can also cause the blade to bind and can be confused with other symptoms. Electric motors don't usually go "weak". If the windings get burned or scorched they will continue to function until the windings either short or open. If the motor is actually stopping I would suggest that you check for a loose connection at the main switch or the centrifugal switch in the motor
Bill V

[lahola1]

Yes, the blade completely stopped; quickly pulled the board out then it started up again. Sure sounded like the motor stopped, then started again. Not like the motor was running at speed in the background with the blade stopped then just the blade starting back up again.