motor swap?

[Aaron Hancock]

Money is tight and I'm working on setting up my workshop. I've got a rigid 10" contractors saw, and I love it. I know its not a cabinet saw but it serves my needs. Only problem is that its a little under powered (1 1/2hp) But, I've got an older 3 1/2hp dewalt radial arm saw that I don't use and have no desire to spend the time to set up. My question is.. is a motor swap doable, or particle?

Thanks for the help,
Aaron

[Steven Satur]

Are you serious?

[Aaron Hancock]

sure am.. now tell me why this is a terrible idea..

[Rod Sheridan]

Hi Aaron, perhaps you could list the motor nameplate voltage and current so that we would have a better idea of the motor HP from the radial arm saw.

3 1/2 HP is enormous for a radial arm saw, makes me suspicious of the HP rating.......Regards, Rod.

[Steven Satur]

How are you going to mount that motor in a Ridge Contractors Saw, good enough that when it dislodges and cuts your hands or head off, who are you going to sue?

[Aaron Hancock]

Its a self tensioning belt drive boss, all I'd have to do is swap brackets between motors. Radial arm saw is a DeWalt 7790. Single/ 3 phase, V- 120/ 208-240. A - 17/ 8.5 The saw is already wired to an aux switch, so wiring wouldn't be that much of a problem...

[Rod Sheridan]

Hi Aaron, thanks for the nameplate info from the DeWalt radial arm saw.

Based upon the 8 amp current at 240 volts it's about a 1 1/2 HP motor, which sounds like what you already have in your tablesaw.

regards, Rod.

[Aaron Hancock]

it says 3 1/2 hp right on the side of the saw..

[Dan Keeling]

I've seen a 3hp rating on shop vacs before. Pure marketing hype.

[Jeff Bratt]

it says 3 1/2 hp right on the side of the saw..

Here's pics of several (http://home.roadrunner.com/%7Ejeffnann/WoodWorking/Shop/HP/Horsepower.html) other "HP ratings" that really aren't what they claim to be. Simple rule of thumb - at 120V it takes 10 amps to produce 1 HP, at 240 V it takes 5 amps to produce 1 HP. This is just a quick estimate, but it does help point out the absurd HP claims... look for words like "max", "peak", or "developed" HP - these are clues that the accompanying HP number is a lie.

[Stephen Cherry]

My 1 hp shaper would have my 3 1/4 hp router as a tossed salad before lunch.

[Tom Esh]

Have you considered trying a thin-kerf blade? It's like an equivalent 25% hp increase.

[Aaron Hancock]

Thanks for the (constructive) help. Even I knew it was a crazy idea going in haha.. Maybe I'll try the thin kerf blade. Thanks again.

Aaron

[Don Alexander]

are you bogging that ridgid saw down? i have one of those and its got plenty of power to cut anything i can throw at it there are a few things that are extremely important though

1) properly aligned fence
2) clean , sharp blade/s
3) proper feed rate i.e. you can't feed it as fast as you would a 3hp cabinet saw
4) heavy enough wire feeding your outlet its plugged into ; i've seen alot of houses wired with 14ga wire and that just isn't very good for woodworking machines , the longer the run from the panel the worse it is
5) skip the extension cord and plug directly into an outlet, if you absolutely can't do that use at least a 12ga cord and keep it as short as possible

you have probably thought of all of these things but they are still worth mentioning :)

[Chip Lindley]

Its a self tensioning belt drive boss, all I'd have to do is swap brackets between motors. Radial arm saw is a DeWalt 7790. Single/ 3 phase, V- 120/ 208-240. A - 17/ 8.5...


Thanks for the (constructive) help. Even I knew it was a crazy idea going in haha.. Maybe I'll try the thin kerf blade. Thanks again.
Aaron

Yes, Aaron, a crazy idea! This whole post has me wondering if you have been out in the mushroom patch again! The part that bothers me is that you would contemplate cannibalizing a venerable cast iron DeWalt 7790 12" RAS to try to better a BORG Ridgid TS. That is grounds for confinement in an institution for observation, in some states!

As said, compare the motor plate amperage rating of both motors and see if they are not quite similar. FYI, there is no such animal as a Single/ 3 phase motor (your words)

There is no mounting base on a RAS motor that would readily fit it to a tablesaw, without extensive metalwork. A RAS motor pivots in a yoke, and has a threaded arbor on the end; not a pulley shaft. Your aspiration to do this bit of motor surgery is rather like mounting a Mercury outboard motor on a Volkswagen to power it. Good Luck!

As Don mentions above, setting up your TS as exactly as possible is not an option, but a MUST DO. You may also see a BIG difference, if you can switch your TS motor to 240v instead of 120v. Some will argue the point, but in my experience, 240v gives a 1.5hp TS motor every advantage. The TK blade won't hurt either!

And, get that DeWalt 7790 set up and running! It can do lots of things better than a TS can!
~Chip~

[Van Huskey]

The part that bothers me is that you would contemplate cannibalizing a venerable cast iron DeWalt 7790 12" RAS to try to better a BORG Ridgid TS. That is grounds for confinement in an institution for observation, in some states!

~Chip~


Agreed, IF you really want to do a motor change sell the Delta and use the money for a motor, likely have some left over.

Get a high quality thin kerf rip blade and thin kerf crosscur blade and chances are it will be enough HP for 99% of situations.

Freud (Industrail not the BORG stuff), Forrest, Infinity and Tenryu are excellent blades to start with.

[Eric Wheeler]

Hi Aaron, thanks for the nameplate info from the DeWalt radial arm saw.

Based upon the 8 amp current at 240 volts it's about a 1 1/2 HP motor, which sounds like what you already have in your tablesaw.

regards, Rod.

I'm getting 2.7 HP with the 120 and the 240...how are you getting 1.5?

1 HP = 746 Watts
Watts = Volts x Amps
Watts / 746 = HP
(Volts x Amps) / 746 = HP
(120 x 17) / 746 = 2.7xxxx
(240 x 8.5) / 746 = 2.7xxxx

BTW, just cuz a motor lists an HP doesn't mean that's what it truely is, like mentioned it is marketing hype, they use the surge (startup power) current of the motor to do the calculation that I did. So for the split second that the motor is drawing many more amps (your lights usually dim) than rated, they use that number instead of the running current to calculate. Kinda like lawn and garden tractors, the last time I was looking into them they had 27 HP out, wouldn't surprise me if they had 30 HP by now, but take that 27 HP and put it up against an old 16 HP tractor and see which one is more capable.

[John Lanciani]

[QUOTE=Eric Wheeler;1509848]I'm getting 2.7 HP with the 120 and the 240...how are you getting 1.5?

1 HP = 746 Watts
Watts = Volts x Amps
Watts / 746 = HP
(Volts x Amps) / 746 = HP
(120 x 17) / 746 = 2.7xxxx
(240 x 8.5) / 746 = 2.7xxxx



Not quite. For an induction motor the formula for HP is volts x amps x power factor x efficiency / 746. For a consumer grade single phase motor, .80 is a safe bet for both power factor and efficiency at full load. Using the correct formula that motor is +/- 1.75 hp.

[Erik Christensen]

what chip said - but maybe a bit less harsh :)

your RAS is a much more desirable/capable/productive/functional tool IMHO than your table saw - so my strong recommendation is get your Dewalt tuned, aligned and setup vs stealing parts off it

this is kinda of like a guy who asks you about how to pull the motor from his Ferrari to put in his Yugo so it will go faster.... all you want to ask is.... WHY?????

[Jeff Bratt]

I'm getting 2.7 HP with the 120 and the 240...how are you getting 1.5?

You calculations assumption a motor with 100% efficiency converting electrical input power (watts) to mechanical output power (horsepower) - such a motor does not exist. Here are details on how motor HP is measured...
http://home.roadrunner.com/~jeffnann/WoodWorking/Shop/HP/Horsepower2.html

[Eric Wheeler]

[QUOTE=Eric Wheeler;1509848]I'm getting 2.7 HP with the 120 and the 240...how are you getting 1.5?

1 HP = 746 Watts
Watts = Volts x Amps
Watts / 746 = HP
(Volts x Amps) / 746 = HP
(120 x 17) / 746 = 2.7xxxx
(240 x 8.5) / 746 = 2.7xxxx



Not quite. For an induction motor the formula for HP is volts x amps x power factor x efficiency / 746. For a consumer grade single phase motor, .80 is a safe bet for both power factor and efficiency at full load. Using the correct formula that motor is +/- 1.75 hp.

Ahh, I vaguely remember now. It's been quite some time since my electrical theory class, and for the general purposes of the examples in the class we disregarded the power factor and efficiency, but now I recall that the prof mentioning those constants and said if we take his motors class we'll get more into it, I took communications instead so all I remembered was the formula we used that disregarded the constants.