Member postings for John Munroe

Hi John,

I've thought about a blind type base, but I worry about wear and tear as the base would need to be rather thin to keep the small package.

These are actually parts of two parts that are separated by a spring. The spring is compressed when the two parts are pressed together. Inside the chutes, there can be arbitrarily positioned blocks. I wonder if the jamming issue could be resolved by giving the chutes a better finish, e.g., 1.6Ra? Perhaps, the gaps between the two could be reduced? Would it be reasonable to make the gaps 0.05MM on each side (so that lubricant won't get squeezed out)?

Thanks

John

Unfortunately both ends are supposed to be used for discharged.

The setup is rather small, so I think hinges will fit in there.

I'm not sure if I completely understand, but how does a spiral work here?

Thanks

Hello

I'm trying to design a small metal telescopic track (6cm x 2cm when extended) where small objects may be arbitrarily positioned inside. Here's an example:

In the above example, the green block jams the tracks as the bottom cannot move upward. Does anyone know of a better design such that the tracks won't be jammed? I've thought about putting a sleeve on the inside, but if it was 6cm long and covers the entire extended length, it'd overhang when retracted.

Any help will be appreciated.

Thanks

Yeah, I'm aware of that. I'm having problem with even just connecting the two discs together!

Sure, I know orreries. However, I just wonder if there's a simpler way to achieve something similar in a more compact housing if the two discs can be directly joined up. I'm only trying to model the motion of the objects on one plane, so there doesn't need to be empty space between the discs.

Also, I'm not sure traditional orreries can dynamically adapt/self-adjust to objects shifting axis.

Thanks

John

Edited By John Munroe on 06/02/2016 09:54:12

Edited By John Munroe on 06/02/2016 09:56:05

Edited By John Munroe on 06/02/2016 09:56:21

Hello

I'm hoping to make a small mechanical demo (~10cm tall) that models an orbit that is similar to the Earth-Moon orbit - that is, only one side of the Moon faces Earth. I'm hoping to keep it simple, so here's my idea so far

where the blue and yellow represent Earth and Moon, respectively. These are meant to represent a different planet and its moon though.

The orbit of the Planet (blue) and its Moon (yellow) has the following differences:

- Planet is eccentric
- Only one face of the Planet and see its Moon, i.e. the horizontal bar on each disc should remain parallel. The bars are for explanatory purposes only.
- Planet's rotation axis may shift (vertically along the green bar), but the Moon's orbital axis is fixed, i.e. Moon should be always in contact with the outer ring housing

My question is: how should the two discs be connected in order to to have the above properties? I've thought about using springs, but I think it'd be quite flimsy.

Thank you for the help in advance!

That's interesting! Have you got pictures of the knurled bushings used? Did you make them or buy them off the shelf? I guess you used Loctite on yours - right?

Thanks

Thank you for all the input.

I have a related question: the shaft of my motor is actually just 3MM in diameter. Given that the gear bores are 6MM in diameter, what's a good way to fit the 3MM shaft in a 6MM bore? I'm hoping to avoid using a shaft coupler. Could I add a metal ring of some sort inside the bore such that the resulting bore diameter will be reduced to 3MM?

Hello

I'm looking at some bevel gear setups, e.g.,

and

To me, the rods seem to be offset such that they don't intersect each other. However, aren't bevel gears supposed to mesh along the centre axes?

Thanks

Hello everyone, what a wonderful forum this is! (Long time lurker...)

I am working on a project and am down to the last few operations; and one of them is stumping me.

I have a plastic (POM) 15T bevel gear, 16MM in diameter and 15MM thick, and am trying to fix it on a steel rod (shaft) with a diameter of 6MM. The bore on the gear is also 6MM.

This has to be a firm attachment, as the rod/shaft will drive the gear, rotating another bevel gear (45T).

That's the other problem, the second gear is also plastic, about 14MM thick, with a bore of 6MM as well. The output torque on that rod will be around 0.2N-m, maximum torque around 0.4N-m.

Both gears have M4 set screw holes.

What would be a good way to attach the rods to the gears? I've heard that press fitting metal into plastic may not be a good idea. The 6MM rods I'm using are round, so there's no flat surface for the set screw to hold though. Would it be a good idea to still use set screws even if they'll only be gripping on a round surface?

I've never fit a gear before, so all opinions are helpful. Thanks!