# Thread: Help regarding geared mechanism

1. ## Help regarding geared mechanism

Hello Everybody!
I want some help designing a mechanism, I hope someone here could do that. The description is given below.
I have got two concentric shafts. Outer shaft is output shaft & inner is input shaft.
Both shafts rotate in the same direction.
Outershaft rotates with half the speed of inner shaft.
Dia of outer shaft is 80mm & inner shaft is of 50mm.
Only one pair of gears is to be used.
How I am trying to solve this problem is that one internal spur gear should be attached to outer shaft and one spur gear with inner shaft but at some off centre(i.e. at some distance from the centre of the shaft). Will this arrangement of gears work?
Suggestions required.
Thanks!

2. To make sure I'm picturing this right, it sounds like you're describing something like a planetary gear train with only one planet, no sun gear, and where the planet carrier is held fixed? (Concentric, by the way, means the shafts have the same center, but what your describing has different centers, right?) I've never seen this configuration before, and a quick web search doesn't turn up anything. If using more gears is a possibility, then you can use a typical planetary gear train, with the center shaft connected to the sun gear (input) and the outer shaft connected to the planet carrier (output). With the ring gear held fixed, the sun gear and the planet carrier would rotate in the same direction. Then you just have to choose a gear configuration that gives you a 2:1 ratio. In this design, the shafts would be concentric.

3. @mhJones12. I really appreciate your suggestion. Shafts are concentric, i.e. they have same center. I will consider using planetary gear train. But my real question is, Is there any configuration where I can use only one set of gears? If that is not possible then I will definitely use planetary gear train.
Thanx.

4. If the shafts have to be concentric then I see no way to use only one pair of gears. Planetary gear train seems the best way to go.

5. Your idea will not work using only two gears.
Planetary gears will give you high speed reduction.

You will need four gears to get efficient power transmission.
One gear on inner shaft. One on outer shaft. Two fixed to each other on pin mounted on external structure.

6. The internal gear on the outer shaft (really a tube!) is ok, but only one gear on the internal shaft looks impossible unless the two shafts are parallel to each other, not "concentric". If they must be concentric, you need two more gears to operate this system.
Have a great day: Benoit Ventimiglia.

7. Well in my view if you could play with the diameters of the gears then of course we would have a solution with single pair of gears but with a difference of 30mm, I think it isn't possible. A gear train mechanism could be helpful, as mentioned by one of the post above, but again that will not solve your question . Your answer to the question is no , you can't do it using single pair of gears.
Regards,
Rohan Thapar

8. Finally we do not know what Mr. Thapar wants to do with those two shafts ??? May be there is a simple way to accomplish the same task. Remember: "There are 101 ways to skin a ....t" Maybe lets look at it in a new way. Have a great weekend folks: Benoit Ventimiglia.

9. I meant a very simple solution , reduce or increase the gear diameter(any one) , which will enable the pitch circle and the addendum circle interact.If you could relate it to spur and pinion. Thus,positive drive without slippage.

10. You have not addressed my question: What is that you trying to accomplish? May be there is a simpler way to do it!!!!

11. There is a way of doing this with a single pair of gears, called the Planocentric drive. In this arrangement the shafts are not concentric, as the input shaft is eccentric to the extent of the depth of the gear tooth. The output gear is internal, while the input pinion will have one tooth less than the gear. The pinion is mounted on the input shaft and is separated by a bearing. When the input shaft rotates, the pinion wobbles around the gear at the output speed. This is transmitted to the output shaft through pins.
It sounds very complicated, but fulfills the requirement of one pair of gears. You can Google for the images to see how it looks.

12. Thanks you very much for your suggestions. I am considering all of my options. I will share here whatever configuration I will be using. And if anything troubles me again I will definitely post here & seek your valuable advice.
Thanks.

13. If using more equipment is a probability, then you can use a common planetary equipment practice, with the middle base linked with the sun equipment (input) and the external base linked with the earth service provider (output). With the band equipment organised set, the sun equipment and the earth service provider would move in the same route. Then you just have to choose a equipment settings that gives you a 2:1 rate. In this design, the golf club shafts would be concentric.. . . . . . . . . . . .. .