Got my tach and serpentine belt installed - logan 200

[notqwik]

Got my franken lathe back together this weekend. Got the 39" serpentine belt installed and the tach installed and hooked up. Here are some pic's. You can see the sensor behind the chuck if you look close. Any body got any comments on the speed? At 61 hz, it is 339 rpm and and then at 110 hz it is 612 rpm. Seems like it is a bit slow to me.

Do I need to get a bigger motor / smaller counter shaft pulley?

 

[Chuck K]

Yep, 600 rpm is pretty slow. If that's your true spindle speed at 110 hz you need to look at changing pulleys. I'm just guessing here...but I think that machine should run somewhere in the area of 1200 rpms with the stock motor and pulley setup @ 60 hz. I've never run a motor at anywhere near 110 hz. I have run them down to about 20 hz for short periods and didn't have any problems. I would have to wonder how long the bearings would last at that speed.

Chuck

I just noticed in your pic you are running on the center step of your pulleys....even at that you should be faster than 600. What rpm is the motor rated at?

 

[notqwik]

motor is a 1 hp, 1140 rpm 3 phase. Using a 3" motor pulley and a 10" counter shaft pulley.

Calculates out to 342 rpm at 60 hz. Online calculator is amazingly close. I guess everything is as it should be.

This motor is going to be hard to use if the target is 1250 rpm at 60hz. That means the motor pulley will have to be slightly larger than the counter shaft pulley, or I will need to use the larger pulley on the counter shaft, in addition to changing the other pulleys.

 

[Chuck K]

I think your problem is the motor. Every lathe I've had was equipped with an 1800 rpm motor.

 

[CluelessNewB]

According to the owners manual the stock top speed with original motor and pulleys was 1450 rpm. The original motor would have been 1800 rpm. I'm not sure what size the original countershaft and motor pulleys were but if yours are the same the 1140 rpm motor should give you 918 rpm @ 60 hz and 1683 rpm @ 110 hz. I assume you are using the smallest spindle pulley and largest countershaft pulley for the flat belt (not the middle step as shown) right?

Added Info:
I roughly measured the motor and countershaft pulleys on my 820.

• High Speed : Motor 4.5" Countershaft 9"
• Low Speed: Motor 2.5" Countershaft 10.5".

These are approximate but probably close enough. So it looks like with a 1800 rpm motor the high speed V belt pulleys give a 1:2 reduction so with your 10" countershaft pulley and the 1140 motor at 60hz you would need about an 8" motor pulley to get the same speed.

 

[notqwik]

Thanks for the info. I used a motor I had originally bought for the Hardinge Cataract Miller I'm putting together ..... I have a line on a 3 phase 3/4 hp 1730 rpm motor now and will probably just swap it along with some pulley adjustment.