A riveting problem

I borrowed a fan from 3DW and made some revisions but when I came to adding the rivets they’re just all over the place. Tried a circular array but arms aren’t rotated evenly so rotated group of rivets manually to each arm but have same problem. As I move rivets from arm to arm they appear to be changing position radially on each blade as well as receding thru the arms until by the 4th or 5th arm they hardly show on the front surface anymore.

I rotate about the origin out to a similar point on each arm. I rotated all the blades around in a similar fashion and all attached to surface of each arm the same and appear identical so can’t figure out why the rivets behave differently.

Rivet placement doesn’t have to be exact. The position of four rivets shown are close enough if they appear on other blades in similar position.

flex fan.skp (300.7 KB)

I placed one arm around a heptagon. I covered the middle part.
flex fan_ecati.skp (321.5 KB)

Doh! Well, if I’m not a monkey’s uncle. A hepta-what? I was so wrapped up and struggled a bit trying to use the original it never occurred to me to go a step or two further back which would have been the beginning and start fresh (I’ll blame working on it too long and in the early hours). Ecati your approach sure cleaned the model up and I’m grateful that you pointed me in a better direction. Hope it wasn’t too big a PITA as I hadn’t bothered to group anything other than the rivets. When I post the full assembly, fan, shroud and radiator, I give you a word of credit for your help. I’ll use #flex_fan in the description if you get curious to see the completed item. Thanks!

Here’s an image (viewed from other side) trying to show what I had tried to describe that I always ended up with. The rivets seem to rotate around (CW) on an inclined plane and for some reason slowly disappear a bit each blade into the object.

I don’t understand. If you put the rivets in a blade component, won’t they show up in the same relationship in each blade?

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There are too many errors in the geometry of this model. The best method is to draw all over again.

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Unfortunately the model you started with wasn’t drawn very well so you inherited some problems. @ecati is right that starting over would be best.

If the initial circles for the hub had been drawn out on axis it would be easier to work with. Also, since there are seven blades, I would use a multiple of seven at least for the outside circle on the hub. This would make joining the arms a whole lot easier. I did that here. And then I created the arm, blade and the rivets and used Rotate/Copy to make the rest.

pbacot: That was my thinking as well. Still scratching my head over that issue but has been resolved. Would like to know the answer though just to keep in back of mind.

ecati: Yeah agree. Knew there were some issues but everything went together so nicely except for those darn rivets.

DaveR: Got too involved trying to work with what I had and didn’t think things thru. Don’t know why I didn’t see the simplicity of it from the beginning, maybe it was the early and many hours working on related items. It may have been originally drawn on axes but may have been fussed with. Thought model I posted was on axes though. Lesson learned.

Thanks guys

I just got to thinking while there was some attention on subject. My reality based fan has 7 blades composed of 3 sets of pairs set closer together and then a lone 7th blade. Anyone know off hand how these blades are positioned to maintain balance and for modeling purposes? TIA

Can you show a picture of the real fan?

This is way different construction than my real or modeled one but shows the positions clearly. For modeling purposes I suppose one could start with 13 segments but looks like maybe 29 segs might work better flex fan 2.skp (322.2 KB)


Add fan. I suppose that’s done to avoid some sort of oscillation in the air flow. I expect the lone blade or the arm it is riveted to has a bit of additional weight applied. As for modeling it, I think it would just be a matter of sorting out the angles between blades and working from there.

Balancing with weight makes sense but don’t see anything on mine. I did sneak a model in there with 13 segs if ya didn’t see it. Tried 29 but got way to complicated for my old brain. Arrived at 29 by doubling 13 and adding a seg space centered between the pairs so 26+3=29.

Yes (as you surely know!), by definition all instances of such a blade component (with a sheet-metal blade sub-component and various rivet sub-components) will be identical unless unique transformations are applied to different instances.

TDahl: I didn’t pick up on actually inserting the rivets into a component but my thinking was that if the collection (not particularly a group) of 4 rivets were rotated around on a flat surface to centerline of each arm all rivets would appear the same.

I left the rivet components separate from the blade component but I copied them together making sure the rotation plane was aligned correctly.

I reconfigured a blade from the original to my liking and then rotated it from arm to arm (couldn’t use array as original angle rotation weren’t correct) and all went together nicely. But using rivets from original blade location they just started repositioning themselves from blade to blade. Doesn’t matter if there is a ton of errors in original model as long as the base used to rotate about is flat rivets should appear to come out correctly. The blades having positioned themselves correctly proved that. I’m just curious.

Just uploaded model to 3D Warehouse using keywords #radiator #shroud and #flex_fan. Not sure if there is a way to link directly to model.

Thanks all for the knowledge learned.

Read where blades are still balanced but spaced out unevenly, which makes them sound quieter to our hearing by spacing out the pressure waves.