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

[KICK-ASS]

Hi, I'm new to the Forums and this is my first thread. I have been assigned to draw an isometric and 2 dimensional view of a sprocket. It has to be to scale with the sprocket given to us. I can't figure out how to measure it, much less start it. My guess is to start with the center, but I can't even measure that. When I figure out how to post a picture, I will. What I can tell you so far is that all I am permitted to measure with is a 6" CEN-TECH Dial Caliper. Not sure of the name, but I can describe the center hole(s). The center looks like a gear with 6 (flat) teeth. Above that (I eyeballed the bottom of it at about 1/8 in. away from top of center) is a circle that my caliper reads at 0.276 in. in diameter. It has 14 teeth. Sorry for the long explanation, but I want to make sure the responses can be accurate as possible. When I get the pic, I'll post it. On this thread.

 

THANKS SOOO MUCH!!!

[ReMark]

You can attach an image (ex. - JPG or PNG) by first clicking on the Go Advanced button. At the next screen click on the Paper Clip icon. Browse to where your image is located on your computer, upload it to CADTutor then attach it to your post.

 

So let me get this straight. You have been given an actual sprocket and told to take the measurements yourself then reproduce it in CAD? I don't know who your instructor is but I admire him/her already.

[KICK-ASS]

I know. i just need to actually take the picture. I don't know how to use the integrated webcam on my laptop. And my teacher is the AutoCAD Drafting teacher at Valencia High School.

[neophoible]

Welcome to the forum. It sounds like you may be describing some sort of bike/motorcycle chain sprocket? But a pic would be best. If you can't take one, then try to Google sprocket pics to see what you can find. That's what I did to try to find a sprocket that looked smth like your brief description. While we wait, let me ask just a few more questions:

 

How familiar are you with AutoCAD? From the assignment, I would think you must know a significant amount already.

 

Do you already know how to draw in isometric?

 

Do you know anything about drawing sprocket teeth?

 

Do you know how to measure with dial calipers? Since you were able to measure a diameter, it sounds like you know at least a little. If not, a YouTube video link might be your best bet to get started there. You will mostly be measuring a lot of diameters, which should be very doable in this case.

 

Will you be able to post your progress in the form of DWG files so that your work can be checked?

 

By the way, it sounds pretty impressive to me that a ninth-grader is working on such an assignment. I'm sure folks here will be glad to help you learn as much as you can, so stick with it and don't lose heart.

[KICK-ASS]

I'm pretty familiar with AutoCAD. I'm nearing the end of my Mechanical 2B semester. I can DEFINITELY draw in Iso. For the teeth, I tried something posted on another: Draw a circle, then make a smaller circle on the outer quadrant of the first, polar array, then trim. I did this, but because it was around the first circle, the outside dia was too small. I have the basics of measuring with the dial caliper. And I have been top student of my CAD classes since START of ninth grade (I don't mean to brag haha) and this is the FIRST time I'm having this much trouble with an assignment.

[KICK-ASS]

How do I use the Dell Laptop Integrated Webcam?

[neophoible]

I'm pretty familiar with AutoCAD. I'm nearing the end of my Mechanical 2B semester. I can DEFINITELY draw in Iso. For the teeth, I tried something posted on another: Draw a circle, then make a smaller circle on the outer quadrant of the first, polar array, then trim. I did this, but because it was around the first circle, the outside dia was too small. I have the basics of measuring with the dial caliper. And I have been top student of my CAD classes since START of ninth grade (I don't mean to brag haha) and this is the FIRST time I'm having this much trouble with an assignment.

Sounds like you ought to be able to get up and running fairly quickly with this. If you measure several of the concentric diameters and put them into a drawing, you would be well on your way. Can you measure and draw the following: Inside diameter (bore, center hole); Spline (out to out of the inner "teeth" or notches; there are 6, right?); Width of a spline notch; Outer diameter of the sprocket? How many of the 0.276 dia holes are there? Measure across for a reference diameter to those as well. I suggest just start putting something down for reference if for nothing else.

[neophoible]

How do I use the Dell Laptop Integrated Webcam?

Perhaps someone could help you with that here; but, if you just start drawing the parts of the sprocket you know how to measure and put other parts in as reference, e.g., fake a tooth or show what didn't work quite right, until you know how to do those correctly, it would only take you a few minutes. Then post your progress in a DWG and help could start flowing. Put a few dimensions on the drawing, as well, for comparison. I know you wouldn't do this for a final product, but to get started, you can override the dimension text where the drawing does not yet match your measurements. Just make them a different color (or something) to indicate they are hardcoded.

[ReMark]

You don't need to use a webcam to create an image. A simple screen capture will do. What OS are you running?

 

How to take a screen shot using Windows XP...

 

http://windows.microsoft.com/en-us/windows-xp/help/setup/take-a-screen-shot

 

Another option would be to use a screen capture program such as Snagit...

 

http://www.techsmith.com/snagit.html

 

Is this by any chance a countershaft sprocket like this....

 

http://www.motorcycle-superstore.com/2/10/211/6487/DPITEM/Dirt-Bike-Motocross-Front-Countershaft-Sprockets-Renthal-520-Off-Road-Front-Countershaft-Sprocket.aspx

Edited May 10, 2013 by ReMark

[neophoible]

ReMark: That's similar to what I was guessing (the smaller one in this more general pic): http://twostrokemotocross.com/wp-content/uploads/2010/12/ren-sprocket.jpg

 

I think he's still needing to make an actual photo to get onto the computer first. If he has the image up on his screen via his webcam, then he could do a screen capture. Alternatively, he could use a cell phone with such capabilities, or a digital camera.

 

If he has the part number, he or someone here might be able to find the right pic online.

 

But, if he does not have much experience with any of that or help at home in doing it, then, as good as he seems to be at drawing in AutoCAD, he could just send a rough draft of what he needs to draw. In any case, from what I understand, he should be measuring the sprocket himself and make an AutoCAD drawing based on those dimensions.

 

K-A: I've no doubt ReMark could practically draw this thing blind (he does that sort of thing a lot here). So, unless it is a direct part of your assignment, you don't really need to worry about an actual picture here. Just start putting down the rough idea as though you were sketching on a napkin. (Did I just say that?) Then explain what you know how to measure, what you don't know, what you know how to draw, what you don't know. You're evidently one of our best and brightest, so go for it! I suspect that once you get started it will come together very quickly.

 

If nothing else, then perhaps you could roughly trace the thing on a piece of paper, add a few notes, then scan it into the computer.

[ReMark]

I draw blind all the time. I have a scarred lens in my right eye. Vision is 20/1000. It just takes me twice as long to see everything!

[neophoible]

I draw blind all the time. I have a scarred lens in my right eye. Vision is 20/1000. It just takes me twice as long to see everything!

:lol:See what I mean?! But half the speed of light is still bookin'!

[easymike29]

I draw blind all the time. I have a scarred lens in my right eye. Vision is 20/1000. It just takes me twice as long to see everything!

 

Can you not have the lens replaced as is done in cataract surgery?

 

Gene

[neophoible]

Here's another link that shows a few key dimensions on the diagram: http://cnemanda.b2bage.com/product-motorcycle-transmissions/1293297/chain-amp-sprocket-kit-for-cd70-motorcycle.html

[JD Mather]

Are you willing to follow steps, step-by-step?

[KICK-ASS]

I appreciate your help, but the reason I came hear was because I didn't know any of those kind of sprocket terms. (bore, outside dia, etc.) However, I do know that there are 14 teeth as for measuring them...

[neophoible]

I appreciate your help, but the reason I came hear was because I didn't know any of those kind of sprocket terms. (bore, outside dia, etc.) However, I do know that there are 14 teeth as for measuring them...

OK; and we're glad you sought our help. We don't really care if you don't know the terms right now. I probably don't even know them all! You can call them whatever descriptive terms you like. Did you take a look at any of the links we presented to see if anything matches up? As good as you are at AutoCAD, don't you think you could quickly approximate the sprocket in a preliminary 2-D drawing? Or perhaps use some of the other ideas to get up and running? If you just put smth down, then you can refer to the dimensions themselves.

 

By the way, the diagram I linked to shows a symbol that is a circle with a line through it--it represents diameter. But you already know this much, right? You don't really need to know the terms in order to measure the diameters and put them into AutoCAD and post, or to just draw an approximation and post. If it is just the teeth you don't know how to measure, then post what you have and we can go from there. "Tell what you know, show what you've got." I really think you can do this.

[KICK-ASS]

GOOD NEWS!!! I figured out the picture thing! I'm editing it now (it is unbelievable how blurry the webcam makes it). And yes, I am willing to go step by step IF that is what it takes.

[neophoible]

I appreciate your help, but the reason I came hear was because I didn't know any of those kind of sprocket terms. (bore, outside dia, etc.) However, I do know that there are 14 teeth as for measuring them...

With an even number of teeth, you should be able to measure all the way across from the end or tip of one tooth to the one on the opposite side of the sprocket. That would be the outside diameter. The inner hole has two basic diameters that can be measured with the calipers. That's already three concentric circles to draw.

 

If you're having trouble with any of this, I seriously suggest you answer Yes to JD Mather's question and commit to doing exactly what he says. He will carefully step you through. It's a very good option in any case.

[KICK-ASS]

Thanks! The outside diameter is 3.107 in, the outer circle of inner hole is dia: 0.983 in, and the inner circle of inner hole is dia: 0.8265 in.