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Fixing RF45 milling machine (noisy gearbox) AndysMachines

PeterT

Ultra Member
Premium Member
Came across this very good video showing what's in the guts of the typical RF-45 mill & one of (many apparently) potential sources of gearbox noise. Mine was a growler from day one & seemed to be getting worse over time, but I lacked the confidence or know how to tear down, investigate & potentially source parts. Who, knows, it may have been something relatively simple. I wish there were other videos like this at the time. The closest ones was CNC conversions & they basically turfed most of the gearbox mechanism anyways.

 

Tom Kitta

Ultra Member
The problem with RF45 noise is that it is direct gear driven machine. All gears are metal on metal and straight cut.

Mine is not noisy and actually quiet till the very last gear - at 1500 rpm - max (or maybe 1800) it is noisy. I do not think this is due to any issue - I think it is noisy as much as new.

I also have a drill press that is gear driven from Sweden so I can compare at same speeds a bit - but Swedish machine has plastic (!!!) gears for I assume top speed to keep things quiet. At least this is what I was told.

Far worse fix for RF-45 is electrical - box is tiny and there are a LOT of cables as there is interlock between going forward and reverse for both motors - so you cannot go forward and reverse at the same time.
 

phaxtris

(Ryan)
Premium Member
Premium Member
straight cut gears are always noisy, no matter what you do if you have straight cut gears you will have gear whine

not saying that is the only noise you are hearing, just be warned, it will always have gear noise

...think of every manual transmission car you have ever driven...reverse is always noisy, because reverse uses straight cut gears as opposed to helical gears, thats the whine you hear.
 

PeterT

Ultra Member
Premium Member
Well there is normal gear noise & there is RF-45 'clackety-clack something else' noise. Plenty of lathes & machines have entirely steel, often much higher gear counts or more complex driveline arrangements and they run with with a pleasing hum. My 14x40 lathe was the same vintage & country of origin, its nearly silent by comparison to the mill. Now a lathe spindle remains essentially axially fixed where the mill quill must move. But another data point that stands out in my mind is when we had our meetup at Modern couple years back & Alex ran their Chinese RF-45. It was significantly quieter, what you might think of as normal. So they either fixed something or it was lucky tolerance day with the keyways or splines or something, not sure. Seems to me I checked & there are no composite gears, it looked rater identical to prior designs. I think same goes for PM's 45. Its been a standing observation for decades so I just assumed it was by design.
 

PeterT

Ultra Member
Premium Member
I never considered the straight cut gear aspect. OTOH looks like that's what I have in my lathe. Probably from the same factory LOL.

Aside from Andy changing/upgrading his bearings, maybe one scratchy one in the lot, seems like his biggest issue may have been the iffy key / keyway allowing the float. He showed the before after noise level & it it was significant. no other gear related changes. Now maybe if the gears themselves were upgraded, we'll never know.

On my RF-45 I could rotate my quill by hand on the drawbar section & make that same clunk-clunk sound by lightly reversing motion. In one direction it was essentially quiet. Gear teeth roll on one another if everything aligned & cut properly & powered in the same direction. I had this theory that maybe the SP motor delivering its power pulses at just the right (wrong) frequency that there was enough momentary pause that the gear train was getting 'impulsed' kind of like I was doing by hand. But the fact that it got worse over time makes me think it was mechanical, some of the axial sliding fit components, the spline, keyway....

1684770778792.png
 

jcdammeyer

John
Premium Member
On my RF-45 I could rotate my quill by hand on the drawbar section & make that same clunk-clunk sound by lightly reversing motion. In one direction it was essentially quiet. Gear teeth roll on one another if everything aligned & cut properly & powered in the same direction. I had this theory that maybe the SP motor delivering its power pulses at just the right (wrong) frequency that there was enough momentary pause that the gear train was getting 'impulsed' kind of like I was doing by hand. But the fact that it got worse over time makes me think it was mechanical, some of the axial sliding fit components, the spline, keyway....
I have a similar issue with the spline in the spindle and the driving pulley. It's just loose enough that it makes a clacking noise unless under constant load. With gears all it takes is a slight offset in where the gear shaft holes are bored and the teeth will still mesh but not the desired rolling action that an involute shape is supposed to provide. And with that you also get clacking type noise.
 

slow-poke

Ultra Member
Great video.

I guess I'm stating the obvious but straight cut gears in an automobile transmission are noticeable noiser (and stronger). When driving on the street and a hot rod pulls along side, they know pretty quickly that the car with them is all business.
 

phaxtris

(Ryan)
Premium Member
Premium Member
Where did you hear straight cut gears are stronger ? its quite the opposite, helical gears are stronger due to the fact that more than one tooth is engaged at a time, the advantage in a high hp car is that there is no thrust load created from the helix, less load on the thrust bearings/case/etc, and no wasted energy creating that thrust force

but same tooth count, same pitch, same material a helical gear is stronger
 

Tom Kitta

Ultra Member
Where did you hear straight cut gears are stronger ? its quite the opposite, helical gears are stronger due to the fact that more than one tooth is engaged at a time, the advantage in a high hp car is that there is no thrust load created from the helix, less load on the thrust bearings/case/etc, and no wasted energy creating that thrust force

but same tooth count, same pitch, same material a helical gear is stronger

Well, they are "stronger" as far as teeth go but their axial load can tear everything else apart... so who cares if your teeth did not fail but transmission is dead b/c shaft bent or bearing disintegrated.

Generally you can make equally strong gearbox design with either.

I think in RF45 the design choices made are mostly centered around "price". I see a lot of design not with say splines but simple keys. RF-45 is made to a price point. If nothing fancy is needed - nothing fancy is used. Also I suspect the gears do not mesh super perfectly and this also introduces extra noise - especially at full speed.
 

slow-poke

Ultra Member
The case is the weak link on some of the Detroit type transmissions Muncie and T5 come to mind. Weak case too much flex, things start breaking. Straight cut gears can result in less case flex for a stronger transmission (also more efficient) . Beefier aftermarket case can help as well. I was pretty good at breaking drivetrain parts.
 

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a smile

Lifelong hobby - cold iron
Premium Member
Came across this very good video showing what's in the guts of the typical RF-45 mill & one of (many apparently) potential sources of gearbox noise. Mine was a growler from day one & seemed to be getting worse over time, but I lacked the confidence or know how to tear down, investigate & potentially source parts. Who, knows, it may have been something relatively simple. I wish there were other videos like this at the time. The closest ones was CNC conversions & they basically turfed most of the gearbox mechanism anyways.


I can learn some knowledge from this, and I happen to be repairing the drill press ----

I also just finished most of the repair, soon into the motor drive time, I can't wait to hear the sound of my drill machine, mine is two electric wood gear, should be quieter!
QQ图片20230618081011.jpg
Also, I replaced all the bearings
 

MikeANW

Member
Came across this very good video showing what's in the guts of the typical RF-45 mill & one of (many apparently) potential sources of gearbox noise. Mine was a growler from day one & seemed to be getting worse over time, but I lacked the confidence or know how to tear down, investigate & potentially source parts. Who, knows, it may have been something relatively simple. I wish there were other videos like this at the time. The closest ones was CNC conversions & they basically turfed most of the gearbox mechanism anyways.

This is an excellent video. May have to rear mine down over the winter.
 

fixerup

Super User
I had leaks on my lathe change gear lever, and replacing the o-rings on those shaft was a major chore. So I had this mechanic in a bottle LUCAS transmission fix from the 1980. It would ride on the gear and stay on , We use to call it honey oil. Another claim was, it would stop the leaks and that why I used it. I poured about half a liter in, and it immediately drop the noise a few decibel , I was surprise it was quite noticeable. It still leaks but much less. My gear box was all gear and the bearings were seal ones.
 

fixerup

Super User
Yes STP sells a similar transmission fix with the same claim. Stop slip and all leaks. . .... etc
But no were on my Lucas bottle they mentioned reduced transmission noise. But it sure made my gear box quieter. I just checked and it did finally sealed the lever shaft seal. There is no oil seeping from them. It took a while to seal completely, 2yrs since I poured the Lucas oil in it. And yes there is oil in the gear box. Lol
The sight glass is showing correct level.
My friend always laugh at me for using these liquid mechanics bottles, but some do work. I initially bought the Lucas tranny fix for my hard shifting 70's Vw van and again I was really happy how well it shifted afterwards.
 

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Ironman

Ultra Member
Lucas also makes a 5th wheel and slider lube, meant for holiday trailers. It sure is honey oil and sticks like snot.
 
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