Motor Rpm And Ratios

M

Manderioli

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My Van Norman no 10 mill came with a baldor 1725 rpm motor. I currently have the motor being inspected to find out the condition and curious if the motor is too big for my machine. Currently it is a L1322T 2hp 1725rpm.

Originally VN calls for a 1hp 1150 rpm motor but I do not have the original stepped pulleys (flat belt) Equipped to the machine are 4 stepped v belt pulley's in steps of roughly 3", 4.5", 5.5" and 7". My low speed gear is 23/46 while the high speed is 33/36. The motor pulley is roughly 3.5" that transmits to a 9" pulley, which is original for this machine.

So I will try to explain the lay out of the pulleys:
3.5" transmits to 9"
9" pulley is on the same shaft as one stepped pulley
3" step transmits to 7" step on other stepped pulley
4.5" transmits to 5.5"
5.5" transmits to 4.5"
7" transmits to 3"
The second stepped pulley transmits to the low/high gear box
23/46 low
33/36 high

My rpm at the spindle are roughly (w/ 1725 initial input rpm)
Low-125, 238, 356, 680
High-229, 436, 652, 1245

A 1150 rpm motor would give me roughly:
Low-74, 141, 210, 402
High-135, 253, 378, 721

If I used a 2" motor pulley with the 1725 rpm motor I would end up very similar to the 1150rpm figures.

Originally Vn has rpm 46-84-112-205-272-500. Will the 1245 rpm damage the brass bushings? Would be nice to have the rpm for small end mills but not at the expense of destroying the machine.

I already am considering a brand new motor and want to make sure I will not over run the machine.

Any experience, advise, ideas, help would be greatly appreciated.
 
Personally, I wouldn't be too worried. I've over speeded a couple other old machines. Don't run it too hard and too long up there. Keep it lubed. And yep, I see why. You need a bit more Rs for small endmills.
 
i need to insert my 2 cents. its possible the design engineers had something in mind when they suggested 1 hp, and 1200 rpm. i would search for a comparable motor to the original.
1: it will most likely fit the machine better
2: you will not "tim taylor" it and possibly cause it harm.
 
I don't have an answer.
However, like always I have questions.
Do we know if there are bearings or bushings? Both?
It seems that both bearings, bushings, and lubricants have evolved significantly over time.
It's my understanding that different bearings and bushing have different lubrication requirements.
Some (especially vintage) bearings and bushings were not designed to handle modern lube additives.
Do we know which lubes your bearing/bushings were designed to handle?
We can also speculate that higher rpms may generate more friction, thus heat.
Is the entire system designed to handle the additional rpm?

Daryl
MN
 
Found this, other sources may have different information available:

AST Bearings offers bearings that are capable of rotation in excess of 500,000 RPM. These are typically used in experimental and defense applications.

However, the speed capability of a bearing will depend on its size, the type and amount of lubrication used, the bearing and cage materials, precision levels and tolerances, and for how long the the maximum speed is required (among other factors).

http://www.astbearings.com/faq-max-speed-of-bearings.html



Additional documents:
White Papers & Technical Information About Bearings
AST Bearings provides "value beyond the part" by sharing its technical knowledge with fellow engineers and designers. AST engineers and technical writers will be constantly updating and adding new materials to this section of our website so bookmark it, share it, and come back frequently.

http://www.astbearings.com/technical-information.html

Daryl
MN
 
The machine has SKF 6305 Ball bearings for the lower pulley transfer shaft (9" to 4 stepped pulley) but the rest of the machine has brass/bronze bushings. The lubricants that I will be using have been sourced from other members that meet the requirements back from 1920.
 
Consider looking at the ratings for SKF6305 and associated bushings.
Also, think about how you will be using her. Horizontal mode may likely require the slower speeds.
Small end mills and softer metals will tolerate higher speeds very well.

Daryl
MN
 
Another thing to keep in mind, older machines have a lot of gears in them for transmitting power and RPM's to the spindle and such. They were designed to run at the stated speeds on the machine for the life of the machine if properly lubricated. When you start playing with the "bench mark" like speeding up the RPM's on the machine, you start playing with the design factors that went into that machine originally. So instead of getting 60 years out of a machine life, you may get 5 years out of it by making changes to RPM's.
So if you speed up the RPM's, expect to see more noise coming from the gearing, bearings going bad sooner, turning into a trashing machine soon... But wait, what happens if you improve the lubrication of the bearings, gears, bushings? Those life factors increase significantly! Something to think about....
 
Last edited by a moderator:
4gsr said:
Another thing to keep in mind, older machines have a lot of gears in them for transmitting power and RPM's to the spindle and such. They were designed to run at the stated speeds on the machine for the life of the machine if properly lubricated. ........
Click to expand...

It's interesting to note that the engineers at Van Norman designed attachments to increase spindle speeds instead of just offering a faster motor.
Was it because they wanted to sell attachments? Or because the transmissions and heads were not designed to handle the additional RPM?

Daryl
MN
 
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