Thread: Motor twin pulley dimensions ???

HI blitza500 ,
I just recently bought a New 1/2 hp Motor 1425 rpm Single Phase Motor. For My Model 'A' Hercus Lathe as a result I had to calculate the Pulley sizes. The old Motor was 1425 Rpm too ,but I knew that the slow Speed was always to quick. I used the calculation method for Compound Drives from the 'Engineers Black Book - 2nd Edition' . My old Motor pulley is Steel and its sizes are 2 1/4" and 3 1/2".
The Pulley Sizes I worked out are 1 1/2" (220 rpm lowest slow speed and 534 rpm fastest slow speed-not on back gears) and 3 1/4" (423 rpm slow high speed and 1029 rpm fast high speed -not on back gears). If a 3 1/2" pulley was used the slowest high speed would be 446 rpm (not on back gears) and the fastest high speed would be 1083 rpm (not on back Gears). I have ordered the New Pulley but am still waiting for it. Also still waiting on a price for a reversing switch.
Two Speed Motor Drive and 4 - Step Belt Drive:
Fast Motor Speed 1050 - 770 - 550 - 420 (Back Gears >) 230 - 170 - 120 - 92
Slow Motor Speed 540 - 395 - 280 - 215 (Back Gears >) 118 - 86 - 61 - 47
All the above Speeds are for a Double Motor Pulley. A double Motor gives You the Two Speed Motor Drive. The only other way to get a Two Speed Motor Drive. Is to have a Motor that has Two inbuilt Speeds itself for example 1425 rpm and 2850 rpm.
I hope this is of Help to You and any one else interested. I must join the Hercus Register later.
Cheers steran50 (stewart)

Hi Stewart, Thank you for that information as my old girl has a way to go before finally running My main concern was the thickness of the wall and as you have a twin pulley are the V's literally machined upwards to a blunt edge no side wall like the single pulley I have
So can you measure the width of your old pulley as I am going to make a new one from scratch but mine looks like a 20 year old Aluminium pulley with no side walls left and I do not believe that is the case so could you please measure or do you want to sell the pulley as I am fitting a new 5HP 1450 RPM (WEIRD) to my old girl but am going to make a plate to bolt this motor on as the bolt pattern is so far out like 2" and I want to be able to set the pulleys in line as well as having both pulleys fitted with a belt so I can measure the difference as nothing on my lathe is standard anymore so it is all made to fit but I have never seen a pulley unless worn out with such sharp ends on the outside diameter

Next Question as you have found our little secret site HaHa I am doing a register I have all your details I need from your email except the serial number and colour with you this makes 3 more people within 24 hours who have come onto the forum you would be Number 27 and all I am doing is collecting serial numbers and details to keep this site alive plus keep a roll of Honour if you like to the owners who have persisted with their Hercus 9" lathe

As their is no other Q & A Forum for the Hercus 9" so the serial numbers we can date due to Drummond supplying a build date list and I am just doing this to get as many people with Hercus's to register

This is not Compulsory you are still Number 27 anyway but if you want to let me know what the Serial Number and Colour is or was it just helps to preserve the remaining Hercus's as even Hercus has no History to look at so up to you

But if you can give me the width dimensions
email me at [email protected]

as the pulley is sitting in front of the Keyboard with Ken"s Nut and Washer who will be just about ready to drop in in the next 15 minutes to pick up and have a chat

All the best derek bitza500