Desperately need help drawing/measuring 2d sprocket!!!!

[KICK-ASS]

Sorry about the blur in the upper left. IT WON'T GO AWAY!!! (Do you guys need a side view?)

[JD Mather]

I appreciate your help, but the reason I came hear was because I didn't know any of those kind of sprocket terms.

 

I think you meant here rather than hear.

You never answered my question. Are you really willing to go through this process step-by-step.

 

Can you give me an approximate measure center to center of these arcs (just need a ballpark measurement).

 

Do you have a Machinery's Handbook?

 

If you are a student, is there a reason you are not using Inventor?

[JD Mather]

If you have a Machinery's Handbook you should be able to find an image very similar to this one.

 

Once you have commited to following the process we can begin.

 

[JD Mather]

Once you give me the approximate distance of the red line shown above on your actual part we can fill in the spreadsheet and calculate our parameters for this sprocket.

 

[neophoible]

And yes, I am willing to go step by step IF that is what it takes.

JD, I think he did answer your question, but with a condition. The answer to his condition is, of course, that it DOES need to be step by step. I'll leave it to you to explain why.

 

K-A, congratulation on making the pic and getting it uploaded--good enough; and congratulations on making some base measurements.

 

A few more questions for you regarding your assignment: Do you have an actual statement of the assignment? If so, you should post that. Again, "Tell what you know, show what you've got."

 

How much math do you have under your belt? I assume you have Algebra I. Have you taken a formal Geometry class? How much Trigonometry do you know? How much calculating are you allowed/expected to do for this assignment?

How much are you allowed to reference outside the sprocket itself? For example, are you allowed to determine anything about it based on what it is, a standard roller chain sprocket? Did your teacher mention anything about tolerances regarding measurements? How close to exact are you supposed to be when done?

 

You mentioned that you tried to draw a tooth, but the method did not seem to work out. I didn't really follow what you were trying to do, but in any case, you should post that attempt here. Along with the post you should include the dimensions you were using. Was it a method recommended by your instructor?

Edited May 11, 2013 by neophoible
words not spaced

[ReMark]

You would have been better off taking a digital picture with your phone and posting it.

[JD Mather]

JD, I think he did answer your question, but with a condition. The answer to his condition is, of course, that it DOES need to be step by step. I'll leave it to you to explain why.

 

I missed this response by the OP. My internet is going painfully slow making it difficult to go backwards in the discussion thread (each page takes 5 minutes to load).

 

Sprockets are governed by standardized dimensions as indicated in the Machinery's Handbook. I have set up a spreadsheet for the calculations - so no math is needed (unless the OP wants to dig into the math).

 

 

The process is fairly straitforward for someone who knows how to draw circles, lines, trim and extend and a couple of rotates of lin

[JD Mather]

I just realized that the OP did give an OD dimension for the sprocket earlier that would indicate that it is smaller than a #40 chain. OD is not the best of measurements to go by as the theoretical perfect points are usually cut down a bit becuase they would quickly wair away anyhow. (now all my spelling is looking suspect to me, if my internet was not running so slow I would do a check, but oh well.

 

The best measure would be the pitch, but the thickness is also a pretty good measure (and the easiest) since the thickness is also governed by the standard chain sizes and given in the Machinery's Handbook. (see tooththick variable in spreadsheet image above) Of course manufacturing tolerance and application might vary that parameter a bit, but it shouldn't be too far off and can only go one direction (smaller) as you can't make the chain wider from side to side.

[neophoible]

What I can tell you so far is that all I am permitted to measure with is a 6" CEN-TECH Dial Caliper.

One of the reasons for my extra questions is that, from the OP, it sounds like he may be required to rely solely on measuring the sprocket and is not allowed to consult any manuals. I would like for him to clarify his assignment so that we can help him do it the way the instructor expects. The main thing is to get off dead center and start. He's done that, and that's a good thing. Now he can continue to move forward, but he will not be closer to the end of his assignment if he doesn't do it according to the instructor's specifications, though he stands to learn a lot in any case.

[JD Mather]

.... sounds like he may be required to rely solely on measuring the sprocket ....

 

Having worked out on the shop floor for 8 years making parts, in my opinion such an effort would be a waste of time. Better to do it by the standards.

[KICK-ASS]

Overall view of progress. This one isn't to important. The image FOLLOWING this post will have a closer view on the copied dwg (read txt in the img) with dimensions.

[KICK-ASS]

Here is the more detailed one. Let me know if you want a picture of the ORIGINAL one (left side on first picture) with dimensions.

[neophoible]

Overall view of progress. This one isn't to important. The image FOLLOWING this post will have a closer view on the copied dwg (read txt in the img) with dimensions.

Looks like progress, but does not show any dimensions, nor did you respond to earlier questions. I take it you are feeling more comfortable measuring the sprocket?

[neophoible]

Here is the more detailed one. Let me know if you want a picture of the ORIGINAL one (left side on first picture) with dimensions.

Again, it looks like a lot of progress. Very blurry, though. Are you showing just dimensions you measured yourself? What about the angle on the tooth? It is really very difficult to make the dimensions out. I feel like I'm looking at it without glasses, even when I'm zoomed in very close. Also, you did not respond to earlier inquiries about your project. Do you understand why JD wanted the dimension you pointed out? When is your project due?

[KICK-ASS]

Is it really?! (No sarcasm instead ) I'm not sure how it can have blur, considering that I got that by using the "Prnt Scrn" key. (basically a screenshot)

[KICK-ASS]

I can understand why it seems that I didn't answer his question (you couldn't make out the dimensions), but I used txt box to write "JD!!!" and pointed an arrow to the dimension he asked for. And in case you can't read it (this sentence is talking to JD) The measurement you asked for is 0.63284954 in.

[KICK-ASS]

However I still need a side view and an Iso view, but I'm pretty sure I got those. If I end up getting stuck on it though, I'll make sure to come back to this thread. (rather not make a new one )

 

THANK YOU GUYS SSSOOOO MUCH FOR ALL YOUR HELP!!!!!

[neophoible]

And in case you can't read it (this sentence is talking to JD) The measurement you asked for is 0.63284954 in.

Wow! Those are some really fancy dial calipers you've got there. I've never had such precise measurements from dial calipers before; or anything else for that matter. BTW, I can actually see the image much better on my wife's home laptop than my ancient work monitor.

[neophoible]

However I still need a side view and an Iso view, but I'm pretty sure I got those. If I end up getting stuck on it though, I'll make sure to come back to this thread. (rather not make a new one )

 

THANK YOU GUYS SSSOOOO MUCH FOR ALL YOUR HELP!!!!!

No, you shouldn't start a new thread for the same project. And, you are welcome for the help. Though you didn't answer most of the questions, I think your response via the finished view pretty much sums it up for us. I'm sure JD would still be glad to step you through a more thorough approach to drawing a standard sprocket by the book, if you're ever interested. Hope you did well for the assignment. Maybe you'll let us know what grade you get for this? I wish they'd had CAD back when I was in 9th grade. Hope you will continue to make the most of the opportunity.

[neophoible]

Having worked out on the shop floor for 8 years making parts, in my opinion such an effort would be a waste of time. Better to do it by the standards.

Yes, I wouldn't argue that with you, given the need to come up with a drawing for an established standard part.

 

On the other hand, there is a lot to learn and this is only a 9th grade project. An instructor has to decide what the goal of a project should be. This looks more like a reverse engineering project to me. When reverse engineering, there aren't always standards or drawings to go by. In this case, one can do the reverse engineering and then compare the results to the standard to see how close he came. Again, this is not a bad idea, in my opinion. There have been times where I have had to work backward to match something where the drawings no longer existed, the original manufacturer was no longer in business, etc., so the comparison is more difficult, more expensive, especially if you have to do it over. This project seems to me to be a good introduction to this sort of thing.

 

There are also times when a special sprocket has had to be designed and one needed to know how these things work in general. However, I don't think this is a part of this particular assignment. There are also a lot of tools one could use for the purpose (reverse engineering), but again, there's a lot to learn in general; it has to be taken a step at a time. From what I can tell, this is still pretty new to the OP. Just using the dial calipers on the sprocket seemed daunting at first. So, I would say this is a good step in the overall learning process, even if the final product does not match actual standards.