SB 16 motor swap

I have a 1941 SB16 with it's original 1.5hp motor, and was curious if anyone here has upgraded to more horsepower??

I was thinking of installing a 3hp.

Thoughts??

Thanks,

Todd
Orange, CA

The original flat belt is a certain width and will not transmit more than a certain HP without going faster, which naturally would affect spindle bearing life

tar356 said:

I have a 1941 SB16 with it's original 1.5hp motor, and was curious if anyone here has upgraded to more horsepower??

I was thinking of installing a 3hp.

Thoughts??

Thanks,

Todd
Orange, CA

Click to expand...

tar356 said:

I have a 1941 SB16 with it's original 1.5hp motor, and was curious if anyone here has upgraded to more horsepower??

I was thinking of installing a 3hp.

Thoughts??

Thanks,

Todd
Orange, CA

Click to expand...

I can vouch for no issues swapping to a larger motor--just put a 3hp Leeson into my 1943 16" machine. What I can't yet say is if there's any advantage to it as my machine isn't yet reassembled due to some wear issues I need to address on the bed and saddle. John Oder may well be correct in the limiting factor being flat belt transmission capabilities; however, some of that may be mitigated by using a modern serpentine belt on the crown pulleys. I'll know myself soon enough, but not swapping the motor wasn't an option in my case and the 3hp Leeson was given to me as a freebie so I used it.

Space is not going to be an issue, although you will likely need to drill and tap new holes for the motor attachment bolts. You can see photos of the newly reassembled underdrive unit in the later posts on my ongoing restoration log here.

johnoder said:

The original flat belt is a certain width and will not transmit more than a certain HP without going faster, which naturally would affect spindle bearing life

Click to expand...

That's the big question...knowing at what point the belt will start to slip.

I'm not really asking the lathe to become something it will never be, but I do find that in certain situations, a heavy cut will draw the motor down a little (not stall or slip the belt). I think having a little more hp would certainly help.

I don't see any problem with a 3hp, especially if you take heavy cuts. Belt slippage shouldnt be a problem if you have the right belt material. My 16x10 has the original 1.5 3ph motor. It has been said that newer motors are not rated the same as the older motors. Also, running on a rotary converter may cause some power loss.

If I have to change a motor these days I use a 220 single phase cap start, its more convenient than running off the rotary converter. I put a 2hp in my 10L and its a pleasure to use.

When deciding about motor power for a machine, I usually look to see what it came with originally, figuring that the manufacturer had some idea of the machine's capability and what power would be required.

I see no harm in going to more power since the belt drives will let you know when you've gone too far.

There's some measure of truth in the statement about older motors having the ability to deliver more power for a given name plate rating than present day motors. However, having said that, older motors did not have the advantages of the higher quality insulations available today and so were less heat tolerant. Even today with the um......less expensive motor constructions, you can probably get about double the nameplate rating horsepower out of any of them. You just have to be careful about temperature. You can't do it continuously without overheating.

I would never buy a single phase motor to power any shop machinery today. The advent of the quite inexpensive VFD converters and their advanced capabilities makes it pretty silly to buy a single phase motor capable of only one speed. A three-phase motor driven by a VFD is a natural for powering lathes, drill presses, milling machines, band saws, etc.

I have a 16 inch SB made in 1969 that was originally equipped with a 3 HP motor. It is a 4-step cone pulley version. I see no reason why yours should not be able to handle a 2 HP motor.

If you do a close reading of the motor horsepower listed in various vintage SB catalogues over the years, you will find that the HP gradually increased over time.