Definining a Datum Plane tangential to 2 Surfaces

[rrrocket]

This is my first posting to this forum, despite having been a follower of the various postings for a couple of years. I have decided to bite the bullet and sign up.
I am using NX4 currently, and have been using UG since V9 days, but this problem has me stumped. I am attempting to construct a datum plane tangential to 2 surfaces of revolution, at an angle to another already defined datum plane. To put the problem in context, the surfaces of revolution are the front and rear tyres, the defined datum plane is the vertical plane of symmetry of a bike, and the angle is the lean angle of the bike. The final datum plane is to conduct a clearance check between the bike and the road surface.
Any suggestions?

 

[JohnRBaker]

Could you provide an image of the model or at least a 'sketch' of what the relationship is between the described elements?


John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

 

[rrrocket]

John,
I have uploaded a picture, hope it worked!

The front and rear tyres are shown, the datum plane I need is between the front and rear contact patches, at an angle to the vertical datum plane shown.
Note that the front and rear tyres are completely different sizes and profiles

 

[rrrocket]

John,
Spot the newbie: this time I read the instructions!

 

[JohnRBaker]

Could you post the part file itself? I could create a similar example, but why waste the effort if you can provide the original.


John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

 

[rrrocket]

John,
I have copied the relevant items to the attached file

 

[JohnRBaker]

The problem is that a plane tangent to 2 tori is ambiguous and as such needs some additional input. Unfortunately, our Tangent to Tangent option doesn't provide for any additional references. It appears that you will have to come up with another scheme to solve your problem.


John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

 

[rrrocket]

John,
That was the answer that I was dreading. The addition of a value for the angle would give 2 unique solutions – one at the top of the tyres and one at the bottom (or 4 solutions if you consider both sides of the vehicle), but, as you say, there is no way to input that information. Unfortunately, as the tyre profile and the tyre positions are variables, as is the lean angle, constructing the plane ‘longhand’ is going to be difficult and tedious.

But thanks for trying, anyway.

 

[hudson888]

This is a fair solution. I think John answered your question quite well and correctly however I think that the question as asked may be re-worded in terms of the model that you provided and therefore I offer the attached solution.

I am treating this as similar to a ground lines setup for automotive design. I have altered your model slightly by breaking the links and moving the small wheel off the same plane as the other one to make the example slightly more complex but clearer I think. The whole thing has been set up with a few associative curves in NX-5. You will notice a couple of suppressed offset features which you can toggle on and off to prove that the construction is in fact associative. One created the tangent line is unlikely to change sides unless you more one of the features fairly dramatically.


See how you go

Regards

Hudson

 

[rrrocket]

Hudson,
Thank you for your reply, which, unfortunately, I won't be able to study until I get into the office after the Easter break, as it is from a later version of NX to the one I have here.

 

[hudson888]

Sorry,

Similar method probably refined over what I did in NX-5 this one is in NX-4, second time lucky

Regards

Hudson

 

[mmauldin]

I think I have a solution to this problem. I tried to set up an engineering.com account but no joy there. I can send it by email if you wish.

 

[mmauldin]

Fixed. See if this works for you.

 

[rrrocket]

I finally got some time to evaluate your suggestions, and the final solution is attached. I couldn’t get a fully associative datum plane that covered all the wheel positions (different front and rear ride heights, different front steer angles), but the manipulation required to get an answer is ‘good enough’. The datum plane that is a different colour to the rest denotes the road surface at full lean.

Certainly the solution is good enough to figure out that the area where I thought I would have a clearance issue is quids in, and another area that I hadn’t considered had a foul condition with the road surface – fortunately, by catching it early, the problem was solved by a minor design tweek.

Thanks to all for their replies.