Mathematical question

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
When I saw it on Youtube I didn't get the right answer and I am an engineer that's pretty good at geometry and trigonometry. I'm guessing I shouldn't post any more tricky questions (at the time I regarded is as interesting rather than insulting to"engine guys" ) if there are other "touchy feely" types like yourself.

Re "engine guys" then among the various jobs I had before I started my own company, I was Quality Engineer for a Danish company making parts for the F-16. The contract at the time stated that the Danish company would make half the number. Ended up that the Danish company made them all.
??? What in Steve's reply suggested anything touchy-feely or that he felt insulted?
 
??? What in Steve's reply suggested anything touchy-feely or that he felt insulted?
I didn't write that he felt insulted. I wrote that I did. I suggest you read some of the posts he writes to others and either you get what I mean or you don't.
 
Hmm, sorry that I misunderstood. I have to say, though, I have been reading Steve's posts for years, and have not felt any "sharp edges" to them. YMMV.
Depends on how you read his replies. I've only read a few but to me, and obviously not to you, I read what he writes as condescending rather han helpful although I suppose to some (most?) they appear helpful.

How would you read and understand the reply I got when I asked why he didn't just give an answer? If that isn't enough look at the recent replies he's been giving posts.

I've tried but can't find a thread he's started. I'm sure he has so if you let me know I'll read it. Who knows, I might change my opinion ;)
 
I did not hear that reply as condescending, but rather as good humored. Always hard to tell "tone of voice" in an internet forum, so I generally assume the best. YMMV.
I know you didn't "hear" it. You read it. That's one of the biggest problem with the internet. You can't see the expression on people's face. A very good reason to think before posting.

Interesting too is that you seem to dislike more me objecting than why I objected.

There are 2 rules in life:
1. NEVER GIVE OUT ALL THE INFORMATION
 
I don't regard myself as stupid but it did take me a while to figure out why I originally got the answer wrong. There have been many explanations but in my own head I've got it explained thus ;)

The distance the smaller circle is travelling around the larger circle isn't the circumference of the larger. It's the larger circumference that the smaller circle has from its radius. I know others have more or less written the same but if I was explaining it to anyone (in this case myself) that's how I'd write or say it.

"Statistics is the art of never having to say you're wrong."
 
I don't regard myself as stupid but it did take me a while to figure out why I originally got the answer wrong. There have been many explanations but in my own head I've got it explained thus ;)

The distance the smaller circle is travelling around the larger circle isn't the circumference of the larger. It's the larger circumference that the smaller circle has from its radius. I know others have more or less written the same but if I was explaining it to anyone (in this case myself) that's how I'd write or say it.


Easy to say after reading what I posted last Sunday to your other thread (Reading, understanding and following instructions)...

A coin of diameter 2R is held stationary while a smaller coin of diameter 2r is rolled around its circumference until it returns to its starting position. How many revolutions does the smaller coin make ?

The number of revolutions (N) can be found by dividing the distance the center of the coin has traveled (T) by its circumference...

N = T/(2*pi*r)

The center of the smaller coin travels around a circle with a radius of (R+r); thus T = 2*pi*(R+r) and...

N = (R+r)/r = R/r +1

In the case of R = r (two identical coins), N = 2.
 
Wow. I have been on this forum sence 2006? And have never found Mr klotz ( Mr used loosely) to be anything but helpful. Math skills way above normal. Just an all around helpful when he can guy. I have been staying away from this thread as not to exacerbate some negative feelings but I can't help to defend Mr klotz. In my opinion he has been nothing out side of helpful.
 
All right, I've had it. Thread Man, you have a grand total of 50 posts, and you've been a member for just over 3 weeks. In that time, you have repeatedly posted that various members are condescending, being a smart ass, not following directions, etc. - and these members are folks who have been around this forum for many years, with many hundreds or thousands of posts and many hundreds or thousands of likes - in other words, long valued members who are widely regarded as some of the most helpful posters on this forum.

All this to say, I heartily endorse your statement that it is time for you to leave the forum. Sorry to be blunt, but there it is.
 
I don't regard myself as stupid but it did take me a while to figure out why I originally got the answer wrong. There have been many explanations but in my own head I've got it explained thus ;)

The distance the smaller circle is travelling around the larger circle isn't the circumference of the larger. It's the larger circumference that the smaller circle has from its radius. I know others have more or less written the same but if I was explaining it to anyone (in this case myself) that's how I'd write or say it.

"Statistics is the art of never having to say you're wrong."

Sorry, but no.

Take the larger circle, split it in the bottom center and turn the two tails out so that it's shaped like an Omega symbol. Roll your smaller circle along the Omega-shaped path. This will have almost exactly the same "larger circumference that the smaller circle has from its radius", but the smaller circle will turn exactly the expected "ratio of the diameters" number of turns.

The reason there's an extra rotation when the path is a circle, is because the path contains a rotation. You only get as much extra rotation as the difference in rotation of the beginning and ending of the path, so if the beginning and ending are co-linear (and there are no rotations between them), there is zero extra rotation in the rolling circle, nomatter how far its center travels.
 
You're right. What I wrote was easier to say than what you wrote. There's smart and there's smartass. You seem to be the latter. It's also why I choose to quit this forum as I don't want to be the same place as folk like you.

Bye all!

I don't think you will be missed.
Happy trails

Mark T
 
Well I was wrong and of course Marv was right but I had to draw it out to convince myself
M4GEAR-Model.jpg

By rotating a 10T planet gear about a 60T sun gear (3:1) ratio in 180° (10 tooth) increments you can see that after being turned though 3 half turns the datum dot is now in its starting position and thus after travelling all the way around it has only traveled through 2 revolutions.
It loses a rev not gained a rev as I had (wrongly) guessed.

Regards, Ken
 
Last edited:
We have a very helpful and wonderful engineering community and we should be proud of that and not be offensive to each other. Mathematics is full of interesting and non-intuitive puzzles (which should really reside on YouTube) which often don't have obvious answers or even answers at all. That's how it is!

I did like Ken's approach to the problem - thank you

Although ThreadMan used a cartoon which depicts terms which remain in use in todays Politically Correct world, I personally thought the cartoon unnecessarily vulgar and was surprised that it was allowed by the moderators. I made no comment at the time.

I do however endorse the criticism aimed at ThreadMan - he was out of order - completely out of order and he is no loss to the community.

As a mathematician I would also take issue with his statement "Statistics is the art of never having to say you're wrong". He should only make comments he understands but fortunately we will never hear his response!

Mike
 
The cartoon reminds me of my first visit to Copenhagen Airport about 1981. We were welcomed by a large poster of a ferocious Viking complete with helmet and sword and the words 'We have already been trading for more than a thousand years with the rest of Europe', clearly to support the then Danish campaign for acces to the EC.
 
You're right. What I wrote was easier to say than what you wrote. There's smart and there's smartass. You seem to be the latter. It's also why I choose to quit this forum as I don't want to be the same place as folk like you.

Bye all!
I don't know if you read it but I hope you will
As I said : " Wellcome !
Please share your knowledge ... . "
You may be good at math , geometry ... but there is always someone better than you ( definitely not me ) in this forum .
So sit down, calm down, have a cup of coffee or beer and think.
 
Clockworkcheval, Yes it is interesting that different countries have completely different views about humour - some can't even spell humor! Japan is an interesting example of adverts which would never be allowed in the UK. I was once told by my Head Teacher at school to never discuss/joke about politics or religion with someone from Ireland. Having worked in the US I would change that to "never discuss/joke about politics, religion, guns or abortion" with anyone from the outside the upper East/West coast area of the US ie the middle and South.

Its a strange world but fortunately modelling is common to many countries but interestingly not many EU countries.

Mike
 

Latest posts

Back
Top