Planetary Gearbox mounting

[elinah34]

Hello,

I am trying to understand why the planetary gearbox manufacturer recommends mounting his planetary gearbox through the High Torque (Low Speed) side.
I tried to figure out what is the reason, but unfortunately he didn't reply.

A colleague told me I would better mount the gearbox through the High Torque (Low Speed) side, because otherwise "I will transfer all of the generated forces through the gearbox housing", and I am not sure I understood what he meant.

I tried to use a simplified FBD (Force Body Diagram) to analyze the reactions on the gearbox housing in both optional mounting cases (through the High or Low torque side), and it seems that in both cases the gearbox housing reaction would be the same – tangential friction forces (under the bolts' heads) that resist the same torque, no matter to which side it's connected.
Am I missing something?

Thanks!

 

[mfgenggear]

OP
Please provide the intent of the hardware. Generally a planetary gear box is to do the following.
A high rpm motor with low torque.is the input side.
The out put is reduced rpm with high torque.
Objective will depend on the application.

 

[mfgenggear]

Op
The gear ratio dictate the input of the rpm and
The out rpm desired, and torque.
Is there a brochure defining the properties?

 

[elinah34]

Hey, mfgenggear.
Lets leave for a moment what is the input side.
I am trying to understand if the mounting side matters.

 

[mfgenggear]

Hey, mfgenggear.
Lets leave for a moment what is the input side.
I am trying to understand if the mounting side matters.

It does very much so. What is the intent

 

[mfgenggear]

Are you trying to reduce or increase rpm
Also very much depends how the internal components are mounted

 

[elinah34]

I think you didn't understand my question.
I know what is the gear ratio (1/16).
I am trying to understand to which side of the gearbox I attach the L bracket, and if it matters in terms of gearbox durability.

 

[mfgenggear]

Input side with the motor, then run the numbers

 

[elinah34]

I need to increase the speed.
So my manual handle (input) is connected to low speed (high torque) shaft. The output is the shaft on the side of high speed (low torque).
Now - I have interface to mounting bracket connection on both side of the gear (input and output sides) and I wonder if the side the L bracket is connected to matters? And how?

 

[Jboggs]

"I am trying to understand why the planetary gearbox manufacturer recommends..."
OK. We know what "a colleague" said, and we know what various folks on this fine forum have said. But we don't know what the Application Engineer at the gearbox manufacturer, the folks that actually made it, said. I am assuming we don't know that because you didn't ask. I don't mean checking their website or their catalog. I mean picking up the phone and talking to a live person.

No disrespect intended here, but I get awfully tired of giving this same advice over and over again - call the manufacturer and talk to a live person! Not an order taker in Sales. Talk to a live engineer in Product Design or Application Engineering. Manufacturers hire those people for one reason - to help you use their product successfully, and then come back later and buy another one. There are so many intricate details that could effect that recommendation. You might learn that in your specific application it would be ok to mount it the way you want to. Or you might learn the very good reason NOT to do that. The engineers at the manufacturer know more than anyone on this forum knows about that particular question. Call them.

 

[elinah34]

"I am trying to understand why the planetary gearbox manufacturer recommends..."
OK. We know what "a colleague" said, and we know what various folks on this fine forum have said. But we don't know what the Application Engineer at the gearbox manufacturer, the folks that actually made it, said. I am assuming we don't know that because you didn't ask. I don't mean checking their website or their catalog. I mean picking up the phone and talking to a live person.

No disrespect intended here, but I get awfully tired of giving this same advice over and over again - call the manufacturer and talk to a live person! Not an order taker in Sales. Talk to a live engineer in Product Design or Application Engineering. Manufacturers hire those people for one reason - to help you use their product successfully, and then come back later and buy another one. There are so many intricate details that could effect that recommendation. You might learn that in your specific application it would be ok to mount it the way you want to. Or you might learn the very good reason NOT to do that. The engineers at the manufacturer know more than anyone on this forum knows about that particular question. Call them.

If you read carefully what I wrote, then you can see that I wrote "I tried to figure out what is the reason, but unfortunately he didn't reply". He lives in germany and hardly speaks english, so calling isn't useful. Our communication is via emails and I asked several times to explain his recommendation but he stopped replying.
Now, instead of criticizing try to help. Your advices aren't that revolutionary.

 

[kjoiner]

I'm just making a quick comment based on the first post. You get a reaction at the mounting points because the housing is trying to turn in the opposite direction of the output torque. If you mount the gearbox on the output side as shown, the reaction acts as a tangential shear load on the fasteners right at the face of the gearbox. If you mount on the other side, the input side, the reaction is still there but it has to travel as a torsional load on the body of the gearbox to get to the face on the input side. A bigger consideration is whether you have an overhung load on the output shaft. Is it connected to another shaft or is it turning a pulley, sprocket or gear? If so, I would definitely try to mount to the output face.

 

[dvd]

Misalignment at the high speed side will experience many more cycles on the shaft coupling, high-speed shaft, bearings, and seals than the low-speed side. I would strive to provide the best alignment capability at the high speed, low torque end. The housing reaction does not seem that important to me - if the mounting screws can handle the reaction, then surely the housing is capable.

 

[TugboatEng]

This is the second time I've seen this question asked here. The gearbox low speed flange is designed to handle all of the reaction loads. It doesn't matter which side you drive it from. You need to restrain your gearbox on the low speed end. The opposite side simply isn't strong enough.

You may be able to get way with mounting from the opposite side of you aren't intending to load the gearbox to its rated values.

 

[Jboggs]

"He lives in germany and hardly speaks english, so calling isn't useful. Our communication is via emails and I asked several times to explain his recommendation but he stopped replying."

There are many manufacturers of planetary gearboxes. I recommend finding one that actually wants your business. A good industrial power transmission distributor could be very helpful right now since they represent many different manufacturers.

 

[Compositepro]

The low speed side of the gearbox must be capable of reacting the maximum torque. The high speed side does not need to be capable of reacting the maximum torque unless it is used as the mount for reacting this torque. Gearboxes are usually designed the be lighter and less expensive by reacting the low speed torque at the mount on the low speed end.