AndyMark Wheels- adding sprockets, bolts, and such

[Bryan Herbst]

So, after playing around with SolidWorks for awhile, I decided to throw some wheels on the kitbot.

Unfortunately, I can't figure out to add fasteners to the sprocket/wheel. I can use the smart fastener tool to add a fastener, but I can't seem to make it long enough to add nuts (when I add a nut, it appears before the wheel and after the sprocket anyways). I also can't remember off the top of my head the length, size, or even type of bolt used either.

Finally, how would I CAD the sprocket so that it isn't right on top of the wheel? I want to define the assembly so that I can't slide the sprocket and bolts in and out of the wheel.

Still a bit new at this, so all help is appreciated. If someone has a step-by-step guide to assembling the wheels/sprockets, that would be fabulous.

[artdutra04]

Could you post a screenshot of what you have so far? That way it would be easier for us to help you. :)

[JesseK]

I don't use the fastener wizard (or the hole wizard for that matter). I CAD the bolts myself, then add nuts. It's actually pretty easy to make the bolts as parts, and for the nuts I create hollow cylinders that represent the maximum nut dimensions. (edit -- note that creating your bolts will allow you define the lengths of your bolts, rather than allowing the lengths of the bolts available to define your assembly)

In order to assemble the sprocket, bolts, nuts, and wheel, you will want to define two main types of mates: concentric holes and coplanar faces. The best tip here is to define the mates exactly as you would assemble it physically. This will ensure everything lines up and there are no misrepresentations. If you need the sprocket raised away from the wheel, you can create spacers as parts and insert them in between the wheel and sprocket. Be sure to use descriptive file names when saving parts to make it easier if you want to create a new assembly later.

It seems like alot of part creation, but in the end you will know every part, every assembly method, and perhaps a realistic final weight for the assembly if you go that far.

[Bryan Herbst]

I attached a screenshot of one of the wheels. It currently has a bearing and sprocket mated to the wheel. The bearing is fully defined, the sprocket n be moved closer to the wheel or farther away from the wheel, but the holes remain lined up.

I've also been trying to figure out if the KOP came with standoffs or spacers for the sprocket/wheel assembly... can't remember off the top of my head...


If I have to, I may just cad all the nuts and bolts by hand, but if there's an easier way, I would much rather do it that way.

[Greg Needel]

I attached a screenshot of one of the wheels. It currently has a bearing and sprocket mated to the wheel. The bearing is fully defined, the sprocket n be moved closer to the wheel or farther away from the wheel, but the holes remain lined up.

I've also been trying to figure out if the KOP came with standoffs or spacers for the sprocket/wheel assembly... can't remember off the top of my head...


If I have to, I may just cad all the nuts and bolts by hand, but if there's an easier way, I would much rather do it that way.

sounds like you need to add a mate constraint between the face of the sprocket and one of the flat faces on the wheel. You can apply an offset dimension to this mate so the position away from the wheel is defined.

As for the hardware. I would figure out what screw you want, and constrain one. Then use the pattern feature to generate the rest of the screws. All you will need is the angle in between the holes and you will be all set.

[Bryan Herbst]

Is there a way to change the smart dimension in the assembly, and have the distance mate automatically correct itself to the new dimension?

Whenever I double click the dimension, it goes to a properties screen, not a change dimension screen...

Also, My sprocket holes are larger than my wheel holes (?).
I decided I could still use the right size bolts by selecting the holes on the wheel hub for the smart fastener, but it wont let me select those holes in the smart fastener dialog...

[artdutra04]

Okay, things are going better now, just one more question.

Is there a way to change the smart dimension in the assembly, and have the distance mate automatically correct itself to the new dimension?

Whenever I double click the dimension, it goes to a properties screen, not a change dimension screen...Is the smart dimension only controlling the distance mate?

If that was the case, I'd just scroll down to that specific mate, right click > Edit Feature to change the distance.

[Bryan Herbst]

That works, I was just trying to figure out if there was a way to change the mate from the dimension.

Anyways, I guess I edited my message after you replied-
The holes to connect the sprocket and wheel hub are different sizes ((sprocket is larger).
I decided I could still use the right size bolts by selecting the holes on the wheel hub for the smart fastener, but it wont let me select those holes in the smart fastener dialog...How do I make this work?

As for length, if I select a different bolt size, I can get the bolt long enough, but the bolt is too large in diameter for the holes. What do you guys do when adding bolts to the sprocket/wheel assemblies? Am I just doing this a hard way?

[artdutra04]

That works, I was just trying to figure out if there was a way to change the mate from the dimension.

Anyways, I guess I edited my message after you replied-
The holes to connect the sprocket and wheel hub are different sizes ((sprocket is larger).
I decided I could still use the right size bolts by selecting the holes on the wheel hub for the smart fastener, but it wont let me select those holes in the smart fastener dialog...How do I make this work?

As for length, if I select a different bolt size, I can get the bolt long enough, but the bolt is too large in diameter for the holes. What do you guys do when adding bolts to the sprocket/wheel assemblies? Am I just doing this a hard way?I don't really ever use the Smart Fastener option. Instead, I use Machinery's Handbook or other references to manually choose the right size hole for tap/clearance for the specific size hardware that I want.

Then for the CAD models of the hardware, I go over to McMaster (http://www.mcmaster.com/) and look through their online catalog for the screw or nut that I want. When you finally get to a page where you can't narrow down the choices of screw options anymore, almost all of the screw/nut pages have a Download link in the left side of the top grey bar, to download a CAD model of that specific hardware in a variety of different 2D and 3D formats, including SolidWorks.

Other times, they may not have the specific CAD model, but they will have a link on the left frame for "Product Specifications" and/or "Technical Drawing". Usually from this information alone, I can recreate the CAD model of that part.

After a while, you'll end up with quite a large library of parts already downloaded, and you'll more or less have everything that you need. I personally put everything I could ever use across multiple projects inside a "Parts Library" folder. For all McMaster-Carr parts I use the naming convention MC-####_PART-DESCRIPTION.SLDPRT where #### is the MC part number (such as 91251A197), and where PART-DESCRIPTION is something like 8-32x0.75-SOCKET-HEAD.

[Bryan Herbst]

Thanks, I think I might just use McMaster's bolts. Sounds easier than messing with the smart fasteners.

[JesseK]

It looks like you're using AM's flat sprockets, is this correct?

If so, how will you get around the fact that the KOP wheel bearings have a 1/2" bore whereas the AM sprockets are designed for the bearings that have a 3/8" bore? You may be able to get away with no bearing on the sprocket, but you may or may not have problems:

http://www.chiefdelphi.com/forums/showthread.php?t=66640&highlight=sprocket+bearing

[Bryan Herbst]

That is correct.

Do you have a link to a sprocket that will work better?

[artdutra04]

That is correct.

Do you have a link to a sprocket that will work better?All you need to do is to open the CAD model of the sprocket and enlarge the center hole to accommodate the larger bearing.

In real life, you can always ream holes larger but you can't make them smaller. :)

[Bryan Herbst]

All right, everything is working great now. Thanks!

[JesseK]

The other option you have, if you don't trust your machining skills, is a brass sleeve bearing from mcmaster (or such) that you press into the KOP bearings. We used 1/2" OD 3/8" ID bearings, but it was tough to press them into the KOP wheel bearings without breaking the bearings. Once we finally did it, it worked like a charm for 2 full competitions.

Could have told you this earlier, but wanted to let you think on it a bit. Plus, there's always 2 ways around a problem.