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I did some calculations and if the larger pulley is put on the motor side it will up my RPM’s even more.
I would prefer to buy a perfect replacement but that does not seem to be an option and I’d like to have a little bit more range from my gearbox in the 300 - 400 RPM area
On my machine the pulleys are 3"/4"/5"/6". Are they giving the 5 step for the price of the 4 step? It should be easy enough to slice off the 2" section. For all the poking fun at that 8" chuck it is going to come in handy for this, lol.
I don't know how critical the location of the set screw is, it should still be okay on the 3" pulley vice the 4" pulley.
Thank Yota, i’m not exactly sure why I was quoted a different price than the sheet I was sent. Maybe he felt bad for me having to get the 5 step hahah.
I will double check that the set screw location works thanks!
And just to double check that my lathe has one “stock” pulley the motor pulley on you machine is 5,4,3,2... right?
Just throwing this out to you RPM guys - my 10” Utilathe has a 3 phase motor and it is rated for 1 Hp @1725 RPM with voltages 208-220. We are running about 235 ish volts so I decided to check the RPM.
The lathe was running about 25 RPM fast - I adjusted the VFD down to 57.4 Hz to yield a motor RPM of 1725 ish - and all my speeds are bang on.
The speed control on your 9” Utilathe appears to have a 5:1 gearing reduction so if your pulleys are correct you “should” be taking 1725 RPM and then reducing it to 1500, 900, 500 and 250 RPM. Using the gearbox set to low speed you can reduce those speeds by a factor of 5 to 300, 180, 100 and 50 RPM.
To get the correct speeds your motor pulley would be a 4, 3, 2 and 1”. The pulley on the lathe spindle will be something like 7, 6-3/4, 5-3/4 and 4-5/8”. This will give you pretty much the speeds as indicated. Examples:
1/7 x 1725 = 246
2/6.75 x 1725= 511
3/5.75 x1725 = 900
4/4.625 x 1725 = 1491
The pulleys on my machine were cast iron - it would be interesting to find an Original 9 or someone that can clarify all the pulley measurements so the correct ratio is achieved.
Very good thoughts! But the motor pulley is not a 4 inch it’s a 5 inch (5,4,3,2)
But in your calculations you’re not taking into acount the head stock gearing for low and high range. If the spindle pulley was driving the spindle directly you would be spot on!
I think this is my best options to get back into the general RPM range.
If you look at my post again you will note that I mentioned the 5:1 gear reduction you get when you switch from High Speed to Low Speed. Well I did not include the High speed reduction but here is a look inside the gearbox of the Utilathe (9 inch). When I wrote the first post I had reduced the inner gear reductions to a 5:1 but this pic should explain things better.
The 2:1 high speed reduction allows for the motor pulley to be larger than the 4321 and make it a 5432. So using @YYCHobbyMachinist pulley specs with the 6,5,4,3 on the spindle drive: that pulley drives a 20 Tooth gear connected to a 48 Tooth gear which in turn will drive the #16 40 Tooth gear when you are in high speed. the gear reduction is 2:1 so with a 1725 RPM motor you will get the speeds I put up in the top corner reduced to the high speed output: 575/2 = 287.5 , 1035/2 = 517.5, 1725/2= 862.5 and finally 2875/2 = 1437.5 RPM and the Slow speed will be the 15 tooth driving the big bull gear (number of teeth not listed but should be 63 (perhaps 62) to give you your slow speeds. The gear ratio is not a perfect 10:1 but around 10.08 to 1 so there will be a bit of RPM variance but close to 57.5, 103.5, 172.5 and 287.5 for your slow speeds.
Anyway, if you are seeking perfection the only way would be to make a custom pulley to get the ratio as close as possible. As @YYCHobbyMachinist stated "close enough" with a 6, 5, 4, 3...and that could be the original........
Emery - the motor pulley is 5432. As a hobby machinist I don't think the speeds being exact is anywhere close to being an issue. As is being said "close enough".
BrentH- you must be on a boat out in the middle of nowhere to spend so much time on pulley calculations, lol
Emery - the motor pulley is 5432. As a hobby machinist I don't think the speeds being exact is anywhere close to being an issue. As is being said "close enough".
BrentH- you must be on a boat out in the middle of nowhere to spend so much time on pulley calculations, lol
And I'm still of the opinion that he could put the 5432 on the headstock and a 4321 on the motor and have the same thing. What I'm not sure of is how that would affect torque.
But I do appreciate Emery's desire to return the machine back to factory configuration.
Indeed - but your best bet is to keep the pulley diameter larger so more of the belt is in contact. The 5432 is fitted to the motor. The 2 will be closet the motor. Then it’s a matter of what you want in the end for speed. If you had a perfect 1725 rpm motor and you were driving the 6” pulley 2/6 x 1725 = 575. In low speed 575/10.08 = 57 RPM
but say now you take a 1-3/4 / 5-3/4 x 1725 = 525 RPM
so this was part of my question - were the “original pulleys” dialed in to match the gear ratio’s to give you those speeds indicated on the machine? Or was close enough the mission?
if you go back to my original post I changed the drive pulley to a 4321 - well that would be “impractical” with a 1” as it may be too small for the belt to get a good grip. So you go 5432 as your drive then mess about with the spindle pulley.
in the total ideal world you would want that fist RPM to be 500 so you would get 250 and 50 with the gear reduction. That would take pulleys close to 2” and 7” giving an RPM of 492. The problem comes as the next ratio is not good for a 7654
3/6 x 1725 = 862 and is a bit slow. A better match would be 5-1/8” so you would get 3/5.125x 1725 = 1009.
but maybe you have a different combo on the drive pulley like 2, 3.5, etc.
Mine came with a 3/4 @ 1725 but I ended up replacing it with a 1/2 @ 1725 due to a vibration issue.
You got a good deal considering the stuff you got with it. I paid $950 for mine with no stand. It was missing the threading dial indicator, follower rest, dog drive plate, face plate, 4J, and the gears required to delete the height extensions. It did come with 98% of the taper attachment.
so I tried swapping around the pulleys like you said. ( 5-4-3-2 on the spindle 4/ 1/4-3-2-1 on the motor.) The motor pulley was very stuck a couple failed attempts to get it to budge.
My RPMs got a lot closer to what they should be!
RPM was before
50 - 105
100-254
180-415
300-702
250-521
500-1100
900-1926
but I’m still going to pick up the proper pulley just so I can get it a little closer to the actual face plate markings. Especially on the higher speeds.
But... With the switched pulleys I’m getting a vibration issue at what should be 250 RPM. I remember you mentioning that you swapped your 3/4 hp motor for 1/2 hp because of this.
what speed did you have a vibration on?
Also, what length is your V belt?
Mines is a 270 but the motor mount touches the metal base tray on the high speeds. (Probably because one of my pulleys is to small)
That's better!!! I'd use it as is and keep looking for a suitable aluminium pulley replacement or better yet make one.
The belt I'm using is 1/2" X 30"
The vibration issue I had was due to motor vibration and it bouncing the motor mount. The 1/2 HP I replaced it with just spun a lot smoother. With the motor tensioning the belt by weight alone it may have something to do with the 3/4 HP motor being a lot heavier. When I relieved the belt tension the vibration diminished. It's still a bit of mystery.
lol